A · Appendix
Every term
Each term with an ELI5, the real definition and, for terms used across China's robot supply chain, the simplified Chinese with pinyin.
Search in English, Chinese or pinyin. Tone marks are optional: "jiansuqi" finds 减速器. Tick "With Chinese" to see only the terms that have a Chinese name.
420 terms
Absolute encoder
ELI5An angle sensor that knows where it is the moment it switches on, like GPS instead of a trip meter.
RealAn encoder that reads a unique code for every shaft angle, so it needs no homing after power loss; industrial units give 17 to 25 bits over serial protocols such as BiSS-C or EnDat.
Ch. 02Accelerometer
ELI5The part of the IMU that feels pushes, including gravity pulling down, so the robot knows which way is up.
RealA sensor of specific force along each axis, including gravity (1 g at rest). Double integration gives position, so a 2 mg bias becomes about 36 m of error after 60 s.
Ch. 05Access control integration
ELI5Letting the robot open locked doors and gates by talking to the building's security system.
RealIntegration between a robot fleet and a building's door, gate and turnstile access system, so robots pass secured doors under the building owner's rules and every passage is logged.
Ch. 12Action chunking
ELI5Plan the next second of movement at once, do half, look again, plan again.
RealPredicting k future actions in one pass (for example 50 steps, 1 s at 50 Hz), executing part and re-planning. Reduces jitter and compounding error. Introduced with ACT on ALOHA (2023); used by π0 and GR00T N1.6.
Ch. 10Action tokenizer
ELI5A zip file for movements, so a language model can write motion the way it writes words.
RealA method that turns continuous action trajectories into discrete tokens a transformer can predict. FAST (Physical Intelligence, Jan 2025) applies a discrete cosine transform per action dimension, quantises and compresses with byte-pair encoding; it matched diffusion π0 with up to 5x faster training.
Ch. 10Actuated DOF
ELI5How many of a hand's joints have their own motor. A finger can have three joints but only one motor.
RealThe number of independently driven joints, as opposed to total DoF, which includes passive or coupled joints. Unitree Dex5-1: 20 DoF, 16 actuated.
Ch. 04Actuator
ELI5The robot's muscle: the part that turns electricity into movement at a joint.
RealA device that converts energy into motion; in electric robots, a motor plus reducer, sensors and driver packaged as a rotary or linear joint. Actuators are 40 to 60% of a humanoid's bill of materials.
Ch. 02Admittance control
ELI5A stiff arm feels your push with a wrist sensor and moves out of the way on purpose.
RealThe dual of impedance control: measure force (usually with a six-axis wrist sensor) and command a position offset from a virtual mass-spring-damper. Suits stiff position-controlled arms and hand-guiding of cobots.
Ch. 08Advance replacement
ELI5You get a working spare first, then send the broken one back.
RealA service model where a replacement unit or module ships before the failed one is returned, so downtime equals delivery plus swap time. Requires a local spares pool; no maker in the research publishes it for service robots in Southeast Asia.
Ch. 13After-sales service
ELI5Everything that happens after the robot is sold: fixing it, swapping parts, updating software, answering the customer's calls.
RealPost-sale support: warranty repair, spare parts, preventive maintenance, software updates and uptime guarantees. In Southeast Asia distributors deliver it; Pudu supplies free parts and support during warranty and distributors pay for parts after. Otis earns 91% of segment profit from service, the model makers want to copy.
Ch. 13AgiBot
ELI5The Shanghai startup that shipped more humanoids than anyone in the first half of 2026 and also runs a robot rental arm and a data factory.
RealAgiBot 智元机器人, Shanghai (Lingang), founded Feb 2023 by Deng Taihua and Peng Zhihui (both ex-Huawei). About 8,400 units in 1H 2026 (44% of global, SAG). Products: A2 and A3 full-size bipeds, X2 compact biped, G2 wheeled industrial humanoid, D1 and D2 quadrupeds. Brain: Genie Operator GO-1 and GO-2 models; AgiBot World dataset. Hong Kong IPO process began Jul 2026.
Ch. 16Aluminium alloy
ELI5Light, stiff, cheap metal that is easy to cut. Most robot frames are made of it.
Real6061-T6 (E 69 GPa, yield 276 MPa, 2.70 g/cm³) for general structure and 7075-T6 (yield 503 MPa) for highly loaded links; raw US$2.5 to 8 per kg (estimate). "Aerospace-grade" in marketing usually means one of these two.
Ch. 07Annotation
ELI5Adding labels to recordings: what task this is, where each step starts, whether it worked.
RealLabelling episodes with instructions, segment boundaries, success or failure and quality marks. Human annotation costs about US$0.25 to 1.00 per episode; VLM-assisted about US$0.05 to 0.10 (Mar 2026 estimates).
Ch. 11API
ELI5The menu of commands a robot or its cloud will accept from other software.
RealApplication programming interface: the defined requests a system accepts and the responses it returns, such as "send robot 7 to table 12" or "report battery". Maker clouds expose APIs to venues, distributors and partners at different access levels.
Ch. 12Assembly
ELI5Putting all the parts together into a working robot, by hand, by machine or both.
RealJoining sub-assemblies (joint modules, hands, torso, wiring harness, shell) into a finished unit. Design for assembly cuts part count and steps; Unitree's processing and assembly is about ¥3,000 of a G1's ¥41,574 BoM (China Post Securities, estimate).
Ch. 07Astribot
ELI5A Shenzhen maker of a very fast wheeled upper-body robot, famous for cooking and folding videos and sold with a teleoperation rig.
RealAstribot 星尘智能 (Stardust Intelligence), Shenzhen, founded 2022. S1: wheeled upper-body humanoid, two 7-DoF arms, end-effector speed at least 10 m/s, ±0.1 mm repeatability, 5 kg per arm; research edition about ¥500,000 with teleoperation rig and SDK. T1 from about US$13,000. 2026 fundraising past ¥1 billion at a valuation above ¥10 billion.
Ch. 16Authorised service provider
ELI5A repair company the maker has officially approved and given its tools and parts.
RealA partner certified by the maker to repair its products with factory diagnostics, parts and warranty reimbursement. Pudu runs a Service Partner Platform; Weston Robot is Unitree's Global Service Center for Singapore and Malaysia.
Ch. 13Autonomous mobile robot
ELI5A self-driving cart. It builds a map of the building and plans its own way around people and boxes.
RealAMR: a wheeled robot that localises on a map it built with LiDAR or cameras and plans its own paths, unlike an AGV that follows fixed tape or markers; used for totes, pallets and deliveries.
Ch. 01Autonomy level
ELI5How much the robot does by itself versus how much a person still does for it.
RealA rung on a scale from teleoperated (a human drives every motion) to fully autonomous (no human in the loop for the task); robotics has no agreed standard scale as of Sep 2026, so always ask what the human still does.
Ch. 01Availability
ELI5The share of the time the robot is supposed to work that it actually can work.
RealMTBF ÷ (MTBF + MTTR), with repair time converted to scheduled hours lost. 99% at 24/7 is 87.6 hours down a year; 99.9%, the industrial bar, is 8.8 hours.
Ch. 13Back EMF
ELI5A spinning motor also acts like a generator and pushes back against the battery, so it can only spin so fast.
RealThe voltage a spinning motor generates in opposition to its supply, V = Ke × ω; it caps top speed at a given bus voltage and lets sensorless drives estimate rotor position.
Ch. 02Backdrivability
ELI5How easily you can move a robot's joint by pushing on it. Easy to push means safer to bump into.
RealThe ease with which a load can drive an actuator from its output side, falling with gear ratio because reflected inertia scales with N² and friction with about N; high in quasi-direct drives, near zero in 100:1 harmonic joints.
Ch. 02Backlash
ELI5The little bit of wiggle between gear teeth. You feel it as a clunk when the joint changes direction.
RealLost motion between input and output when direction reverses, in arc-minutes. Near zero in harmonic drives; grows with wear and is a key health signal.
Ch. 03Balance
ELI5Not falling over, by keeping your weight's push on the floor under your feet.
RealRegulating the centre of mass and contact forces so the zero moment point stays inside the support polygon, or stepping to the capture point when it can't. Handled by the whole-body controller or a learned policy at 50 Hz to 1 kHz.
Ch. 09Ball screw
ELI5A screw and nut with steel balls rolling between them, so a spinning motor can slide something smoothly in a straight line.
RealA rotary-to-linear screw with recirculating balls between shaft and nut; efficient and precise, lower load and shock capacity than a roller screw. Micro ball screws drive many dexterous-hand fingers.
Ch. 03Bathtub curve
ELI5Machines break a lot when new, rarely in middle age, and a lot again when old. Drawn as a graph it looks like a bathtub.
RealThe failure rate over service life: decreasing early failures, a flat period of random failures, rising wear-out. Humanoid fleets may never reach wear-out: Figure 02 retired after about 11 months.
Ch. 13Battery cell
ELI5One single battery, like a fat AA. A robot's pack holds dozens of them.
RealThe electrochemical unit (cylindrical 18650 or 21700, prismatic or pouch) with a fixed nominal voltage set by chemistry: about 3.6 to 3.7 V for NMC, 3.2 V for LFP. Unitree buys cells and builds its own packs.
Ch. 06Battery pack
ELI5The robot's whole battery: many small cells wired together in a box with a little computer that looks after them.
RealCells in series and parallel plus BMS, busbars, fuses, contactors and enclosure. Humanoid packs run about 0.4 to 2.3 kWh (G1 about 420 Wh derived, Figure 03 2.3 kWh) at roughly 50 to 76 V.
Ch. 06Battery swap
ELI5Taking out the flat battery and putting in a full one, so the robot never has to wait to charge.
RealReplacing a depleted pack with a charged one, by hand or autonomously. UBTech Walker S2 swaps its own pack in about 3 minutes; Atlas also self-swaps. Requires two or more packs per robot and a charging rack.
Ch. 06Behaviour cloning
ELI5The simplest copying: for every picture, learn the move the human made in that picture.
RealSupervised learning on (observation, action) pairs from demonstrations, the plainest form of imitation learning. Stable and sample-efficient; suffers from compounding error, which action chunking and correction data reduce.
Ch. 10Bill of materials (BoM)
ELI5The full shopping list of parts in one robot with the price of each. Add it up and you know what the parts cost before the factory, the test, the warranty and the profit.
RealThe structured list of every component, sub-assembly and quantity in a product with unit costs. A Unitree G1 base is about ¥41,574 (23 joint modules ¥27,500, lidar ¥3,840, depth camera ¥1,869, compute ¥1,415, assembly ¥3,000; China Post Securities, Mar 2026); an Optimus Gen 2 from Chinese suppliers US$46k to 55k (Morgan Stanley). Actuators are 40 to 60% of a humanoid BoM.
Ch. 07Bimanual station
ELI5Two robot arms bolted to one table, working together like two hands, doing one job all day.
RealA fixed work cell with two arms (often 6-DoF with parallel-jaw grippers) and an overhead camera. Dyna Robotics sells these for napkin and towel folding at tens of thousands of dollars each, against hundreds of thousands for a humanoid.
Ch. 15Biped
ELI5Walks on two legs, like you. It can climb stairs and step over things but has to keep balancing.
RealA two-legged robot, usually with six actuated joints per leg; it is statically unstable and relies on a balance controller running at hundreds of hertz.
Ch. 01Bipedal walking
ELI5Walking on two legs, which means spending most of every step balanced on one foot.
RealTwo-legged locomotion with alternating single and double support. Dynamically stable in practice: the centre of mass leaves the support polygon each step and the next foot placement catches it.
Ch. 09BLDC motor
ELI5A motor with no brushes to wear out; electronics switch the coils on and off in turn to pull the magnets round.
RealBrushless DC motor: permanent-magnet rotor, electronically commutated stator, classically driven with trapezoidal current; the same family as a PMSM and often used as a synonym.
Ch. 02BMS (battery management system)
ELI5A nanny computer wired to every battery cell. It stops them getting too full, too empty or too hot, and works out how much energy is left.
RealElectronics that sense cell-group voltages, pack current and temperatures; open contactors on faults (derating first); balance cells (usually passively at 30 to 200 mA); and estimate state of charge, often with an extended Kalman filter.
Ch. 06Booster Robotics
ELI5A Beijing maker of small football-playing humanoids that swept the RoboCup humanoid divisions in 2026.
RealBooster Robotics 加速进化, Beijing, founded Aug 2023. T1 (about 1.18 m class research and soccer humanoid) and K1 (kid-size, launched at US$4,999). 38 RoboCup 2026 teams used Booster robots; more than 700 units to 200+ clients in 20+ countries (company claim).
Ch. 16BotQ
ELI5Figure's own robot factory. A line rated for up to 12,000 robots a year, where the robots are meant to help build robots.
RealFigure AI's manufacturing facility, unveiled 15 Mar 2025: a first-generation line rated at 12,000 humanoids a year, 150+ networked workstations on custom manufacturing software and 50+ in-process inspection points. Figure reported 350+ Figure 03 units delivered and a build rate that rose from one a day to one an hour by 29 Apr 2026.
Ch. 15Brain and cerebellum (big brain, little brain)
ELI5The big brain decides what to do; the little brain keeps the body balanced and moving smoothly.
RealChinese industry split of robot intelligence: 大脑 (big brain) for perception, language and task planning, usually a large model; 小脑 (little brain) for motion control, balance and whole-body coordination, often called 运控. Maps to S2 and S0 in Western three-tier stacks.
Ch. 10Brake
ELI5A clamp inside the joint that grabs when the power goes off, so the arm doesn't drop.
RealA spring-applied, electrically released holding brake in a joint module that locks the shaft on power loss or e-stop; standard on cobot joints and load-bearing humanoid joints.
Ch. 02Burn-in test
ELI5Running each new robot for hours before it ships, so the weak ones break in the factory instead of at the customer.
RealPowered operation of finished units under load or heat to trigger early-life failures (the left of the bathtub curve) before shipment. Durations for humanoids are not public; ask each maker.
Ch. 07Bus
ELI5One shared cable that many parts talk over, instead of a separate wire to each one.
RealA shared communication medium with an addressing and access scheme. Robots use fieldbuses (EtherCAT, CAN FD, RS-485) for joints and Ethernet or USB for computers and cameras.
Ch. 06Calibration
ELI5Measuring exactly where each sensor sits and how it is slightly off, so the robot can correct for it. A camera moved by 2 mm makes every grasp miss by 2 mm.
RealEstimating intrinsic parameters (lens model, IMU bias, scale factors) and extrinsic parameters (the pose of each sensor relative to the body and to each other). Knocks, bracket swaps and temperature can void it, so field recalibration is a service task.
Ch. 05CAN bus
ELI5The cheap, tough network cars use. Devices take turns talking, and the most important message goes first.
RealController Area Network (Bosch, 1986): 1 Mb/s differential bus with priority arbitration; CAN FD raises the data phase to 5 to 8 Mb/s. Common for joints in small humanoids and quadrupeds.
Ch. 06Captive customer
ELI5A buyer that also owns the seller, so the sale is guaranteed but proves little about whether strangers would buy.
RealA customer that controls the supplier through ownership. Hyundai owns 100% of Boston Dynamics, supplies its actuators through Hyundai Mobis and takes all 2026 Atlas output with Google DeepMind. Guaranteed volume; no open-market price discovery.
Ch. 15Capture point
ELI5The exact spot to put your foot after a shove so you stop instead of stumbling.
RealFor the linear inverted pendulum, the ground point x + ẋ/ω (ω = √(g/z)) where stepping brings the centre of mass to rest over the foot. Used for push recovery and footstep planning.
Ch. 09Carbon fibre
ELI5Super-stiff black threads glued in resin. Very light and strong, but slow and costly to make.
RealCarbon fibre reinforced polymer (CFRP): quasi-isotropic laminates E 50 to 60 GPa at 1.55 g/cm³; fibre US$15 to 30 per kg, prepreg US$50 to 150 (estimate). Largely hand laid up, so it pays only where weight is worth money.
Ch. 07Centre of mass
ELI5The single point where the robot's weight balances, like the spot on a ruler you can balance on one finger.
RealThe mass-weighted average position of all links (CoM). Its ground projection, velocity and height drive every balance model; in a humanoid it moves with every arm and torso motion.
Ch. 09Certification
ELI5A test lab checks your robot against the rules and gives it a stamp so you are allowed to sell it.
RealType testing of a design against standards before sale: CE, FCC, UL, RoHS, UN38.3 for batteries, national radio approvals (IMDA Singapore, SIRIM Malaysia, SDPPI Indonesia) and robot standards such as ISO 13482 and SS 713. TÜV SÜD PSB and SGS test robots in the region.
Ch. 07Charging dock
ELI5The robot's parking spot with charging contacts. It drives on by itself when it is low.
RealA fixed station a robot docks with autonomously to charge through contacts or coils; cleaning-robot docks may also refill and drain water (Pudu ET1 8-in-1 dock).
Ch. 06Chip
ELI5A small slab of silicon with billions of tiny switches that does the computing.
RealAn integrated circuit: here the SoCs, microcontrollers, motor-control ICs and memory in a robot. Chinese makers increasingly test domestic chips (Horizon, Rockchip) against NVIDIA.
Ch. 06Circular spline
ELI5The stiff outer ring with teeth on the inside, bolted still, that the squishy cup rolls against.
RealThe rigid, internally toothed ring of a strain-wave gear, usually fixed to the housing, with two more teeth than the flexspline.
Ch. 03Cleaning robot
ELI5A robot that sweeps, vacuums, scrubs or mops a floor by itself. The home ones are round; the commercial ones weigh as much as a person.
RealAutonomous floor-care robot. Consumer units are under 5 kg; commercial units carry 10 to 100 litre tanks, weigh 50 to 400 kg and clean 500 to 3,000 square metres an hour.
Ch. 17Cliff sensor
ELI5Little eyes under the robot that look at the floor and stop it before it rolls off a step.
RealA downward-facing infrared or ToF range sensor on a wheeled base that detects drops such as stairs and escalator edges. Very dark or shiny floors can trigger false cliffs.
Ch. 05Closed loop
ELI5Checking the result and correcting, like tasting soup while you cook it.
RealControl that measures the output, compares it with the setpoint and corrects the command on every tick. Rejects disturbances and model error at the cost of sensors and a stability risk if delay grows.
Ch. 08Cloud platform
ELI5The maker's website and servers that every robot phones home to for maps, updates and reports.
RealThe maker-run online system that stores maps and logs, dispatches tasks, pushes updates and exposes dashboards and APIs. Pudu runs separate platforms for distributors, venues and authorised service partners, with robot data stored in China.
Ch. 12CNC machining
ELI5A computer-driven cutter carves a part out of a solid block. No mould needed, but you pay for every minute of cutting on every part.
RealComputer-controlled milling and turning from bar or plate. No tooling; ±0.025 mm routine, ±0.005 mm in a controlled shop. Machine plus operator about US$12 to 40 an hour in China, US$40 to 150 in the West (estimate). The default for joint housings, reducer parts and low-volume robot structure.
Ch. 07Collaborative robot
ELI5A robot arm gentle enough to work beside people without a cage, because it feels a bump and stops.
RealA cobot: a lightweight arm, typically six or seven axes and 3 to 20 kg payload, that limits speed and contact force (ISO/TS 15066) so it can share a workspace with people; UR5e, Dobot CR and JAKA Zu are examples.
Ch. 01Collision detection
ELI5The robot noticing it has bumped into something by feeling its motors push back.
RealDetecting unexpected contact from motor current, joint torque sensors or skin sensors, then stopping or retracting. The sensing half of power and force limiting.
Ch. 12Commercial cleaning robot
ELI5The scrubber you see gliding across a mall floor at night with a blue light on, leaving a dry strip behind it.
RealProfessional floor-care robot for malls, airports, offices and warehouses: scrubber-dryers, sweepers and vacuums with LiDAR navigation, docking stations and a fleet cloud. Global shipments in 2025 were 50,000 to 58,000 units depending on the analyst.
Ch. 17Compute (算力)
ELI5How much thinking a computer can do per second. More compute runs bigger AI models faster but burns more battery and costs more.
RealAvailable processing capacity, usually quoted in TOPS or TFLOPS for AI accelerators. In robots it trades against power (Jetson Thor up to 130 W), heat and price (T5000 US$4,999 at 1k units after the 22 Jul 2026 increase).
Ch. 06Continuous-rotation joint
ELI5A joint that can spin all the way round, like a wheel, instead of stopping where a human elbow or hip would.
RealA rotary joint with no mechanical end stop, which needs slip rings or a wireless link across the axis for power and data. The electric Atlas uses them so it can turn its torso to walk the other way or stand up from lying face down without a human-like sequence.
Ch. 15Contract manufacturing
ELI5Paying another company's factory to build your product for you.
RealOutsourced production by a firm that owns the factory but not the product. Margins are thin: Foxconn's net margin has hovered around 2 to 3% for a decade. Jabil builds Apptronik's Apollo; Foxconn led the private placement in Agility's SPAC.
Ch. 07Control frequency
ELI5How many times a second a loop checks and corrects.
RealThe update rate of a control loop, in Hz. Each loop in a cascade runs 5 to 10 times faster than the loop outside it; robot stacks span about 1 Hz (planner) to 40 kHz (current loop).
Ch. 08Control loop
ELI5Look, compare with what you wanted, nudge, and do it again, over and over. Your hand does this when you carry a full glass.
RealA repeating cycle that reads a sensor, compares the reading with a setpoint and sends a correction to an actuator. A humanoid nests several: a current loop at 10 to 40 kHz inside each joint, joint position loops near 1 kHz, a whole-body loop at 500 Hz to 1 kHz, a learned policy at 50 to 200 Hz and a planner at 1 to 10 Hz.
Ch. 14Controller
ELI5The part of the robot that keeps asking "where am I, where should I be" and pushes the difference to zero.
RealCode or circuitry that computes a command from a setpoint and a measurement. In a robot, controllers are stacked by rate, from the 10 to 40 kHz current loop on each motor driver to a 1 to 10 Hz planning model.
Ch. 08Core components
ELI5The expensive, hard-to-make parts inside a robot: the joints, gears, sensors and chips.
RealReducers, servo motors and drivers, roller screws, force sensors, encoders and controllers. Actuation plus hands are about 50 to 70% of a humanoid BoM; Chinese makers now lead their home market in harmonic reducers (Leaderdrive 27.5%, Laifual 21.4%, HDSI 4.4% in 2025).
Ch. 18Coreless motor
ELI5A tiny motor with no iron inside its spinning part, so it starts and stops almost instantly. Robot fingers use lots of them.
RealA brushed or brushless micro motor whose rotor is a self-supporting copper winding without an iron core: low inertia, no cogging. 6 to 8 mm units drive dexterous fingers, 16 to 20 per hand; about CNY 1,000 domestic vs CNY 2,000 imported (estimate). Called hollow-cup motors in Chinese.
Ch. 04Cost of transport
ELI5How much energy it takes to move one kilogram one metre. Lower means longer runtime per charge.
RealDimensionless energy efficiency of locomotion, CoT = P / (m·g·v). Wheels beat legs on flat ground by a wide margin; straight-knee and passive-dynamic gaits lower it for bipeds.
Ch. 09Cost-down
ELI5Making the same part cheaper every year, by buying more, designing it simpler and making suppliers compete.
RealThe planned reduction in unit cost through volume, redesign, supplier competition and localisation. Leju's joint module plus driver fell from US$433 to US$202 per axis over three years as purchases grew 100x (corematter, Sep 2026).
Ch. 07Cross roller bearing
ELI5A thin, very stiff bearing whose little rollers point in two directions, so one bearing holds the joint steady against pushes from any side.
RealA bearing with cylindrical rollers alternating at 90 degrees between the races, carrying radial, axial and tilting loads in one slim ring; Unitree uses industrial crossed roller bearings at its joint outputs.
Ch. 02Cross-embodiment
ELI5One brain that learns from many kinds of robot bodies and can drive a new one.
RealTraining on pooled data from different robot bodies so skills transfer between them. Open X-Embodiment pooled about 1M trajectories from 22 robot types and beat specialists by 50%; naive pooling across very different bodies still fails.
Ch. 10Current loop
ELI5The fastest check inside the motor driver: is the current exactly what we asked for? Fix it, again, 20,000 times a second.
RealThe innermost feedback loop of a servo drive, regulating phase currents (and so torque) at 10 to 20 kHz, matched to the PWM switching rate; the velocity and position loops run 5 to 10 times slower around it.
Ch. 02Cybersecurity
ELI5Keeping strangers from taking over a machine that can move and see.
RealProtection of a robot's networks, Bluetooth, cloud links and update channels against intrusion. ISO 10218:2025 requires considering cybersecurity where it can defeat safety functions. Unitree had four public findings from Mar 2025 to Aug 2026, including root over Bluetooth.
Ch. 12Cycloidal drive
ELI5A wavy disc that wobbles inside a ring of pins. Each wobble walks it back one bump, and lots of bumps share every push, so it survives hard knocks.
RealA reducer in which an eccentric input makes a cycloidal disc with one fewer lobe than the surrounding pins orbit; ratio equals the lobe count, output reversed. Many lobes carry load at once, giving high shock tolerance for hips and knees.
Ch. 03Dangerous goods
ELI5Things that could cause a fire or harm in transport, like big lithium batteries. They need special packing, labels and paperwork.
RealGoods regulated for transport by air, sea and road. Lithium batteries fall under these rules; packs above the 100 Wh airline carry-on limit ship as declared cargo, with stricter rules for loose batteries than for batteries installed in equipment.
Ch. 06Data collection
ELI5Recording robots or people doing tasks so an AI can learn from the recordings.
RealCapturing training data for robot policies: teleoperation, wearable and egocentric capture, simulation runs and deployment logs. Chinese engineers shorten 数据采集 to 数采. China had 40+ state data collection centres announced by Dec 2025.
Ch. 11Data factory
ELI5A big hall full of robots and operators whose only job is to make training recordings.
RealA dedicated facility where staged scenes, many robots and trained operators produce teleoperation data at scale. AgiBot's 4,000 m² facility with 100 robots produced 1M+ trajectories and 2,976 hours (AgiBot World).
Ch. 11Data flywheel
ELI5Robots work, mess up, get fixed, learn from it, and work better, round and round.
RealThe loop of deploying robots, logging their failures and human interventions, retraining on that data and shipping the improved model over the air. 1X Expert Mode, Dyna's nightly updates and π*0.6's correction training are examples.
Ch. 11Data pyramid
ELI5Lots of cheap videos at the bottom, a little expensive robot data at the top, stacked to train one brain.
RealThe layered mix used to train robot foundation models: web and human video at the base (huge, no actions), simulation and synthetic data in the middle, real-robot teleoperation and deployment data at the top (scarce, action-labelled). In GR00T N1 the top layer was about 1.7% of the base.
Ch. 11Data security
ELI5Making sure the robot's camera pictures, maps and logs do not leak to people who should not have them.
RealControl over what data a robot collects (images, audio, maps, logs), where it is stored and who can access it. A standard venue IT question; Singapore's PDPA covers personal data. Pudu stores robot logs on servers in China.
Ch. 12Dataset
ELI5A big organised collection of recordings used to train a model.
RealA structured collection of episodes with metadata in a loadable format (LeRobot, RLDS). Reference robot sets: Open X-Embodiment (~1M trajectories, 22 robot types), DROID (76,000 trajectories, 350 h), AgiBot World (1M+ trajectories, 2,976 h).
Ch. 11DDS
ELI5The postal service underneath ROS 2 that actually carries the notes, with settings for 'must arrive' or 'latest only'.
RealData Distribution Service, an OMG publish and subscribe standard with quality-of-service settings (reliable or best effort, deadlines, history). Implementations include eProsima Fast DDS, Eclipse Cyclone DDS and RTI Connext.
Ch. 12Deep Robotics
ELI5The Hangzhou robot-dog company whose X30 inspects power tunnels for Singapore's utility.
RealDeep Robotics 云深处科技, Hangzhou, founded 29 Nov 2017 by Zhu Qiuguo and Li Chao (Zhejiang University). Products: Jueying X20 and X30 industrial quadrupeds (X30 rated −20 to 55 °C), Lite3 education quadruped, DR01 humanoid, Lynx wheel-legged robot. Singapore Power Group deployed an X30 for power-tunnel inspection in Jan 2025.
Ch. 16Degrees of freedom
ELI5The number of different ways a robot can move, one for each motorised joint. Your arm from shoulder to wrist has seven.
RealDOF: the number of independent motions a mechanism can make. A rigid body in space has 6 (three positions, three rotations); a robot's actuated DOF is its count of powered joints, from 2 on a tray robot to 75 on 1X NEO.
Ch. 01Delivery robot
ELI5A wheeled trolley that drives itself from the kitchen to table 14, or from the front desk to room 1207, and comes back on its own.
RealIndoor autonomous mobile robot with trays or compartments, LiDAR plus depth-camera navigation on a pre-built map, 30 to 60 kg payload, 8 to 12 hours per charge. Restaurant units are 送餐机器人, general indoor units 配送机器人.
Ch. 17Demonstration
ELI5One recording of a person showing the robot how to do a task, start to finish.
RealA recorded episode of a task performed by a human, via teleoperation or wearable capture, used as a supervised training example for imitation learning. Operators produce 5 to 50 usable demonstrations per hour.
Ch. 11Depth camera
ELI5A camera that tells you how far away every pixel is, not only its colour.
RealA sensor producing a per-pixel range image by stereo matching, structured light or time of flight. Examples: RealSense D435i (in the Unitree G1 base), Orbbec Gemini 330 and Femto series.
Ch. 05Dexterous hand
ELI5A robot hand with five fingers that can bend at many joints, so it can use tools made for people. Expensive and fragile.
RealA multi-fingered end effector with 6 to 22 actuated joints driven by coreless motors through micro screws, linkages or tendons, often with fingertip tactile sensors. About 17% of an Optimus-class BOM (estimate). Examples: Unitree Dex5-1 (20 DoF), Sharpa Wave (22 active), Inspire RH56.
Ch. 04DFM
ELI5Designing a part so the factory can make it cheaply and easily, before you order the moulds.
RealDesign for manufacture (with design for assembly, DFA): rules and scoring, such as Boothroyd and Dewhurst's three questions per part (does it move, must it differ in material, must it come apart), that cut part count, tooling and assembly steps.
Ch. 07Die casting
ELI5Squirting molten aluminium or magnesium into a steel mould at high pressure, like a waffle iron for metal.
RealHigh-pressure die casting (HPDC): molten aluminium, zinc or magnesium injected into a steel die at 10 to 100+ MPa; 20 to 120 s cycles, ±0.05 to 0.3 mm, tooling US$20k to 300k+, economic from about 10,000 parts. Parts are porous, so usually not welded or fully heat treated.
Ch. 07Diffusion policy
ELI5Start with a random scribble of a motion and clean it up step by step until it is a good move.
RealA policy that generates an action sequence by iterative denoising, as image diffusion models do. Captures tasks with several valid solutions without averaging them into an invalid one. Used by TRI's Large Behavior Models and the GR00T action head.
Ch. 10Digital twin
ELI5A video-game copy of one real building or machine that you keep in step with the real one, so you can try changes on the copy first.
RealA simulation of a specific site, line or robot kept synchronised with live data, used to rehearse layout changes, routes and software updates and to diagnose faults before touching the real system.
Ch. 12Distributor
ELI5The local company that buys robots from the Chinese factory, sells or rents them to your restaurant, and is the one you phone when it stops.
RealChannel partner that imports, sells, installs and maintains a maker's robots in a territory. Under Pudu's published terms the distributor performs in-warranty maintenance with free parts from the maker, and pays for parts after warranty.
Ch. 17Dobot
ELI5A Shenzhen cobot-arm maker that added a humanoid, Atom, and sells it through the same factory accounts.
RealDobot 越疆, Shenzhen, HKEX-listed cobot maker. Atom humanoid: 1.53 m, 62 kg, 41 DoF, ±0.05 mm repeatability, straight-knee gait, ¥199,000 (about US$27,500), third batch of mass deliveries in 2026.
Ch. 16Domain randomization
ELI5Make the video game a bit wrong in a different way every time, so the real world is just one more version the robot has already seen.
RealRandomising masses, friction, motor strength, latency, terrain, lighting and textures per training episode so the policy is robust to the simulator's errors. Used for Helix 02's S0 across 200,000+ environments.
Ch. 09Domestic substitution
ELI5China replacing parts it used to import with Chinese-made ones, usually at a much lower price.
RealThe policy and market shift toward Chinese-made components in place of imports. In harmonic reducers, Leaderdrive (27.5%) and Laifual (21.4%) outsold HDSI (4.4%) inside China in 2025 (estimate).
Ch. 03Downstream
ELI5The customers who use robots and the people who set them up on site.
RealApplications, system integrators, distributors and end users. In 1H to Q3 2025, 73.6% of Unitree's humanoid revenue came from research and education buyers.
Ch. 18Dual-system architecture
ELI5A slow thinker that decides what to do and a fast doer that moves the muscles, working together.
RealA robot brain split into a large reasoning model at 1 to 10 Hz (System 2) and a small visuomotor policy at 50 to 200 Hz (System 1), after Kahneman. Helix: 7B at 7 to 9 Hz over 80M at 200 Hz; Helix 02 adds a 1 kHz S0 whole-body controller.
Ch. 10Dynamics
ELI5The maths of which forces make the robot move how, including gravity and the swing of its own limbs.
RealThe relation between joint torques and motion, M(q)q̈ + C(q, q̇)q̇ + g(q) = τ + Jᵀ F_ext: inertia, coupling, gravity and external contact. Solved forward in simulators and backward (inverse dynamics) for feedforward.
Ch. 08EDU version
ELI5The unlocked, more expensive version of a robot that lets you write your own code for it. The cheap base version is a toy you can only drive.
RealA maker's developer configuration: full SDK and low-level joint access (secondary development, 二次开发), more DoF, optional Jetson compute and dexterous hands, and a longer warranty. Unitree G1 base from US$13,500 vs EDU quoted at US$43,900 to US$73,900 by US resellers; the base warranty is 8 months, EDU 18 months.
Ch. 16Efficiency
ELI5How much of the motor's effort actually reaches the joint. The rest turns into heat in the gears.
RealOutput power divided by input power for a transmission. Losses heat packed joints and cut battery runtime; efficiency usually falls as ratio rises.
Ch. 03Egocentric video
ELI5Video filmed from your own eyes, with a camera on your head or glasses.
RealFirst-person video from head, glasses or chest cameras that shows the wearer's hands and objects as a robot would see them. Sets include Ego4D (~3,670 h), Build AI Egocentric-10K (10,000 h) and Figure Index (16M+ uploads by Aug 2026).
Ch. 11Electronic skin
ELI5Touch sensors spread over a big area like skin, so the robot can feel bumps on its palm or arm, not only its fingertips.
RealFlexible, large-area tactile sensing laminated onto palms, fingers or limbs, usually piezoresistive or capacitive arrays; used for contact detection and safe human contact.
Ch. 04Embodied AI
ELI5AI that lives in a body and learns by acting in the real world, instead of only chatting on a screen.
RealArtificial intelligence that perceives and acts through a physical body; in China 具身智能 is the umbrella policy and investment term for humanoids, robot foundation models and their supply chain.
Ch. 01EMC (electromagnetic compatibility)
ELI5Making sure the robot does not jam other electronics and does not go haywire near strong radio signals.
RealThe ability of equipment to function in its electromagnetic environment without causing or suffering interference, tested for certification (for example FCC Class A or B). Motor drivers switching at 10 to 40 kHz are the main emitters.
Ch. 06Emergency stop
ELI5The big red button that stops the robot right now.
RealA manually triggered safety function that halts hazardous motion immediately, wired independently of normal control software. On Pudu robots a pressed or damaged e-stop is a listed reason the robot will not power on.
Ch. 12Encoder
ELI5A sensor that tells the robot exactly how far a shaft has turned.
RealA rotary position sensor, magnetic or optical, incremental or absolute; joint modules often carry one on the motor and one on the output, and the difference measures gearbox wind-up.
Ch. 02End effector
ELI5Whatever is on the end of the arm that touches the work: a gripper, a torch, a suction cup or a hand.
RealThe tool mounted at the end of a manipulator's kinematic chain, attached at the tool flange; swapping it changes the robot's job.
Ch. 01End-to-end
ELI5One program learns the whole job from seeing to moving, instead of separate hand-written steps passing notes.
RealA learned system that maps raw inputs (pixels, words, joint states) straight to outputs (motor targets) with one network trained on one objective, replacing hand-designed perception, planning and control modules and the interfaces between them.
Ch. 10EngineAI
ELI5A young Shenzhen maker known for front-flipping robots and a robot fighting league, selling a full-size humanoid at about ¥180,000.
RealEngineAI 众擎机器人, Shenzhen (Nanshan), founded Oct 2023 by Zhao Tongyang. Products: T800 (1.73 m, 75 kg, 29 body DoF, 450 N·m peak joint torque, ¥180,000), SE01 (1.70 m, human-like gait), PM01 (1.38 m, front flips). Series B US$200 million at about US$1.5 billion (Apr 2026); filed for HKEX listing Apr 2026; runs the URKL humanoid combat league.
Ch. 16Engineering plastic
ELI5Tough plastics that can replace metal in covers and brackets, like glass-filled nylon.
RealPolymers such as PA66-GF30 (about 9.5 GPa, 180 MPa, 150 to 180 °C), POM and PEEK (to about 250 °C, US$75 to 100 per kg). Nylon absorbs 2 to 8% water, which can halve its strength; check test conditions.
Ch. 07Episode
ELI5One try at a task, from start to finish, recorded as one clip.
RealOne complete attempt at a task, stored as time-aligned streams (cameras, joint positions, actions, gripper state, instruction, success flag). The unit that datasets count, buyers accept or reject, and annotators label.
Ch. 11EtherCAT
ELI5A very fast robot cable network where one message zooms past every joint and each joint grabs its orders and writes its answer as it goes by.
RealBeckhoff's industrial Ethernet fieldbus (2003): frames are processed on the fly by each node, about 100 Mb/s, with distributed clocks for sub-microsecond synchronisation. The de facto bus of multi-axis robots.
Ch. 06Expert Mode
ELI5When NEO cannot do a job, a 1X employee puts on a VR headset and drives the robot from far away. The owner approves it, and the session becomes training data.
Real1X's remote teleoperation service for NEO: an operator in the US takes control through VR when the onboard model fails, with owner approval per session, blurring of people and no-go zones. It fills the autonomy gap at launch and doubles as the company's data collection channel.
Ch. 15Export control
ELI5A government rule that says you need permission to sell certain things abroad.
RealLicensing or bans on exports of strategic goods and technology. China licenses rare earths and magnets (from Apr 2025, with an extraterritorial 0.1% rule suspended to 10 Nov 2026); the US controls advanced chips. Dual-use items: 两用物项.
Ch. 18Extended warranty
ELI5Paying extra to keep the free-fix promise going after the first year.
RealPurchased cover beyond the standard period. Pudu sells it only while the original warranty runs. Consumer extended warranties paid claims of about 21% of revenue (2005), a margin ceiling for robots, which fail more often.
Ch. 13Exteroception
ELI5The robot's sense of the world outside its body: seeing, hearing, feeling an obstacle.
RealSensing of the environment: cameras, depth cameras, LiDAR, radar, ultrasonic sensors, microphones and tactile skin. Typically 10 to 120 Hz, feeding mapping, obstacle avoidance and learned policies.
Ch. 05Failure
ELI5Anything that stops the robot doing its job until a person steps in.
RealAn event that ends a machine's ability to perform its required function until intervention. In service contracts, the definition (does a lost robot pushed back by staff count?) decides the MTBF and the bill.
Ch. 13Failure data
ELI5Recordings of the robot getting things wrong, which show the AI exactly what to fix.
RealLogs of unsuccessful or corrected attempts with synchronised sensors, actions and outcome labels. Labs train on it (π0.7 uses failures labelled with performance metadata), but only when captured on their own robots with full streams; a repair ticket lacks those streams.
Ch. 11Failure rate
ELI5How often the robot breaks, for example once every 1,000 hours of work.
RealFailures per unit of operating time or per unit shipped per period; the inverse of MTBF for a constant rate. No maker publishes failure rates for service robots or humanoids as of Sep 2026.
Ch. 13Fall protection
ELI5What the robot does when it knows it's going down: soften the joints, land on the padded parts, then get back up.
RealFall detection from IMU and state, torque reduction or damping, protective fall postures onto sacrificial parts, and a get-up controller. Matters because warranties usually exclude fall damage.
Ch. 09Fast charging
ELI5Filling the battery very quickly with a big current, so the robot is back at work in minutes.
RealHigh C-rate charging, limited by cell plating and heat. Digit 5: 9 min DC charge for 90 min runtime (preliminary); NEO: 6 min per hour of runtime; Figure 03: 2 kW with cooling in the pack housing.
Ch. 06Fault code
ELI5A short error number the robot shows or sends when something goes wrong.
RealA coded identifier for a detected fault (for example winding overheat on a joint, localisation lost, loss of Wi-Fi). Meaning tables usually sit in maker service documentation.
Ch. 13Feedforward
ELI5Pushing the right amount before anything goes wrong, because you already know how heavy the thing is.
RealA command computed from a model or plan instead of from error: inverse-dynamics torque from planned acceleration, gravity and friction. Carries most of the load in production motion systems; feedback trims the residual.
Ch. 08Field-oriented control
ELI5The motor driver always pushes the magnets sideways at exactly the right spot as they spin, so none of the electricity is wasted.
RealFOC: measuring the three phase currents, transforming them into the rotor's frame (Clarke and Park transforms) and regulating the torque-producing component at 90 degrees to the magnet field, at 10 to 20 kHz.
Ch. 02Figure Index
ELI5A phone app that pays ordinary people to film themselves doing chores. Figure feeds the video to its robot brain instead of paying teleoperators.
RealFigure AI's crowd data operation, public since 25 Aug 2026: 264,000 downloads in 108 countries, 44,000+ weekly contributors and 30 to 35 minutes of first-person video ingested every second, cleaned by a five-stage filtering, fraud, dedup, rebalancing and annotation pipeline. Helix 2.5 was pretrained on it.
Ch. 15Financing round
ELI5One batch of money a startup raises from investors, named in order: angel, A, B, C.
RealA priced equity raise (seed, Series A, B, C, pre-IPO). Chinese founders say A轮, B轮; Apptronik's Series A reached more than US$935m with extensions, showing labels no longer map to size.
Ch. 18Fine-tuning
ELI5Short extra lessons that teach a schooled model one specific job.
RealContinuing training of a pretrained model on a small task-specific dataset, often 50 to 100 demonstrations or about 1 hour of robot data, sometimes updating only small adapter weights (LoRA).
Ch. 10Fingertip
ELI5The last pad of a robot finger, where most touching happens and where the touch sensors usually sit.
RealThe distal segment and pad of a robot finger; carries the densest tactile sensing (Figure 03's detects 3 g) and wears fastest.
Ch. 04Firmware
ELI5The software built into each chip, like the motor drivers and the battery computer. Change it and the hardware behaves differently.
RealLow-level software stored in non-volatile memory on MCUs, drivers, BMS and sensors. Access to firmware and its update tools usually sits with the maker and authorised partners.
Ch. 06Fleet management system
ELI5The control room app that tells every robot in a building what to do, where to go and when to charge.
RealSoftware that holds maps, assigns tasks, plans routes, handles lifts and doors, pushes updates and reports uptime for many robots. Usually the maker's own cloud (Pudu, Gausium, Brain Corp); vendor-neutral options connect brands through Open-RMF or VDA 5050.
Ch. 12Flexspline
ELI5The thin, bendy steel cup in a harmonic drive. It gets squashed into an oval twice every motor turn, so it's the part that wears out.
RealThe thin-walled, externally toothed steel cup of a strain-wave gear, usually the output. It has two fewer teeth than the circular spline and is elastically deformed by the wave generator; fatigue at the tooth root is its main failure mode.
Ch. 03Floor-scrubbing robot
ELI5A cleaning robot that wets the floor, scrubs it with a spinning brush and sucks the dirty water back up through a rubber blade, all in one pass.
RealAutonomous scrubber-dryer: clean-water tank, spray nozzles, roller or disc brushes, rear squeegee with vacuum recovery into a dirty-water tank. Pudu CC1, Gausium Phantas and Scrubber 50, Keenon C40 are examples.
Ch. 17Flow matching
ELI5A faster way to turn a scribble into a clean motion: slide it along a straight route in a few moves.
RealA generative method that learns a velocity field carrying noise samples to data samples along near-straight paths, so about 10 integration steps suffice. The action expert in π0, π0.5, π*0.6 and SmolVLA.
Ch. 10FMEA
ELI5A table listing every way each part could break, what would happen, and how you would catch it.
RealFailure mode and effects analysis: a systematic review of each component's failure modes, effects, causes, detection and severity, often scored as a risk priority number. Used in design reviews and service planning.
Ch. 13Force control
ELI5Telling a joint how hard to push and letting it move wherever that push takes it.
RealControl of contact force or joint torque, using a torque or force sensor or motor current in a low-friction joint. Needed for legs, wiping, insertion and safe contact with people.
Ch. 08Forward kinematics
ELI5Given where every joint is bent, work out where the hand ends up.
RealThe map from joint angles to the pose of a link or end effector, computed by chaining each link's transform. Always has exactly one answer.
Ch. 08Foundation model
ELI5One huge model that learned a bit about everything first, so it can be taught a specific job quickly afterwards.
RealA large neural network pretrained on broad data (web text, images, video, robot logs) and then adapted to many downstream tasks by fine-tuning. Robot foundation models such as π0 and GR00T start from a pretrained vision-language model.
Ch. 10Fourier
ELI5A Shanghai rehabilitation-equipment maker that turned its know-how into padded, huggable care humanoids.
RealFourier 傅利叶 (Fourier Intelligence), Shanghai. Rehabilitation and exoskeleton company; humanoids GR-1 (2023), GR-2, GR-3 (Aug 2025). GR-3: 1.65 m, 71 kg, 55 DoF, soft shell with 31 pressure sensors, aimed at care homes, hospitals and eldercare.
Ch. 16Frameless torque motor
ELI5A motor sold as two loose rings, the coil ring and the magnet ring, so the robot's own joint becomes its case.
RealA brushless motor supplied as a separate stator and rotor with no housing, shaft or bearings, built into the joint to save mass and length; CNY 2,000 to 5,000 each today, target below CNY 1,000.
Ch. 02Fully actuated
ELI5Every joint has its own motor, so every joint can move on its own. More skill, more cost, more to break.
RealA mechanism with one actuator per degree of freedom, allowing independent control of every joint, as in high-end dexterous hands.
Ch. 04Functional safety
ELI5Proving the robot's safety features still work when a part breaks or the software freezes.
RealThe discipline of designing safety functions that perform correctly under faults, with quantified reliability: IEC 61508 (SIL 1 to 4) for electronic systems, ISO 13849 (PL a to e) for machinery control parts.
Ch. 12Gait
ELI5The rhythm of how legs take turns: walk, trot, run.
RealThe repeating pattern of leg contacts and swings, described by the gait cycle (stance, swing, double support or flight). Humanoids walk and run; quadrupeds also trot, pace and bound.
Ch. 09Galbot
ELI5A Beijing company that skipped legs: its robot is a torso on a lifting pole on a wheeled base, and it runs unstaffed shops.
RealGalbot 银河通用, Beijing, founded May 2023 by Wang He (Peking University). G1: wheeled semi-humanoid with a lifting column, working envelope floor to about 2.4 m, 1.73 m, 92.5 kg. Runs Galaxy Space Capsule unstaffed retail kiosks and a licensed pharmacy in Beijing. More than US$800 million raised, backers include CATL, China Mobile funds, Sinopec, CITIC.
Ch. 16Gausium
ELI5The Shanghai cleaning robot company whose scrubbers work at Changi. Formerly Gaussian Robotics.
RealShanghai maker of commercial cleaning robots (Phantas, Scrubber 50 and 75, Omnie, Beetle, Vacuum 40); IDC's No. 1 commercial cleaning robot supplier for 2025 by shipments and revenue; 9,400+ customers in 70+ countries; Singapore arm is a subsidiary of SIMPPLE.
Ch. 17Gear ratio
ELI5How many times the motor turns for one turn of the joint. A 50:1 ratio means 50 motor turns make one slow, strong joint turn.
RealInput speed divided by output speed. Output torque is roughly input torque times the ratio times efficiency. Stages multiply: 4:1 then 4:1 gives 16:1. Engineers quote it as 减速比 for reducers.
Ch. 03Gemini Robotics
ELI5Google DeepMind's robot brain, lent to robot makers. Apptronik's Apollo and Boston Dynamics' Atlas both think with it.
RealGoogle DeepMind's family of vision-language-action and embodied-reasoning models (Mar 2025; 1.5 in Sep 2025; 2 on 30 Jul 2026 with whole-body humanoid control). Distributed to partners rather than open-sourced. Apptronik and Boston Dynamics are the two western humanoid makers that outsource cognition to it.
Ch. 15Generalization
ELI5Doing the job right in a new kitchen, with a new cup, the first time.
RealA model's performance on objects, scenes, instructions or robot bodies absent from its training data. The central unsolved problem: Helix 2.5 reached 56% zero-shot in 30 unseen homes (Sep 2026) against 97 to 99% on trained narrow tasks elsewhere.
Ch. 10Global shutter
ELI5A camera that takes the whole picture at the same instant, so fast motion does not smear or bend.
RealAn image sensor that exposes all pixels simultaneously, avoiding the rolling-shutter distortion of row-by-row exposure. Preferred for robots and used in RealSense's D430 series.
Ch. 05Going overseas (出海)
ELI5The Chinese business word for selling abroad. Every robot maker you meet in Shenzhen will say it in the first five minutes.
RealChinese industry term for international expansion. Pudu reports more than 80% of revenue from outside China for three years running; Chinese vendors held 84.7% of global commercial service robot shipments in 2024.
Ch. 17Goods-to-person
ELI5Instead of a picker walking to the shelf, a robot brings the shelf to the picker, who stands still at a station all shift.
RealWarehouse design in which mobile robots carry storage units (pods, totes or bins) to fixed pick stations. Pioneered at scale by Kiva Systems (Amazon Robotics since 2012); the standard model in Chinese e-commerce fulfilment.
Ch. 17Government subsidy
ELI5Money a government gives a company to do something it wants, like build robots in its city.
RealGrants, rent relief and purchase subsidies. Hangzhou offers up to ¥5 million per project (unverified); Singapore's EDGE grant covers up to 70% for SMEs, capped at S$100,000 a year, from 30 Sep 2026.
Ch. 18Grasp
ELI5Getting hold of something so it doesn't fall.
RealEstablishing contacts that constrain an object against gravity and task forces; classified as power (palm wrap) or precision (fingertip) grasps. Chinese engineers say 抓取.
Ch. 04Gravity compensation
ELI5The robot adds exactly the push needed to hold its own arm up, so the rest of the controller only fixes small errors.
RealFeedforward torque τ = g(q) that cancels gravity at each joint configuration, computed from link masses and centres of mass. Lets low-gain PD loops hold pose without sag.
Ch. 08Grinding machine
ELI5A machine that shapes hard steel with a spinning abrasive wheel to within a few thousandths of a millimetre. Precision screws and gears are finished on them.
RealA precision machine tool that finishes hardened parts with an abrasive wheel; thread and gear grinders set capacity and accuracy for roller screws and reducers, and high-end units are mostly imported. Thread grinder: 螺纹磨床.
Ch. 03Gripper
ELI5Whatever the robot uses to hold things: a clamp, a suction cup, soft fingers or a hand.
RealAn end effector that grasps objects: parallel jaw, suction, soft, underactuated or dexterous. Engineers say 夹爪 for jaw-type grippers.
Ch. 04Gross margin
ELI5Out of every dollar a customer pays, what's left after paying for the parts and the factory.
Real(Revenue minus cost of goods sold) divided by revenue. Unitree 60.4% (2025), humanoids 62.9% (9M 2025) down from 87.7% (2023); UBTech 44.7% (1H 2026); JL Mag magnets about 16%; harmonic reducers 35 to 45%.
Ch. 18Gyroscope
ELI5The part of the IMU that feels spinning: how fast the robot is turning or tipping.
RealA sensor of angular rate. MEMS gyros measure the Coriolis force on a vibrating silicon structure; bias instability (degrees per hour of drift) is the headline spec.
Ch. 05Harmonic drive
ELI5A squishy toothed cup inside a stiff toothed ring. An oval cam squeezes the cup round and round, and each lap it slips back two teeth, so a fast motor makes a slow, strong, precise joint.
RealStrain-wave gear: an elliptical wave generator deforms a thin flexspline inside a rigid circular spline with two more teeth. Ratio = flexspline teeth ÷ 2, typically 50:1 to 160:1 (up to 320:1) in one stage with near-zero backlash. Used in arms, wrists and most humanoid rotary joints. HDSI (Tokyo) leads globally; Leaderdrive and Laifual lead in China.
Ch. 03Helix
ELI5Figure's robot brain. A slow part reads the scene and the instruction a few times a second, a fast part moves the joints hundreds of times a second, and since 2026 a reflex layer keeps it balanced a thousand times a second.
RealFigure AI's in-house vision-language-action system. Helix (Feb 2025): a 7B vision-language model at 7 to 9 Hz plus an 80M visuomotor policy at 200 Hz. Helix 02 (Jan 2026) added a 10M-parameter whole-body controller at 1 kHz trained in simulation. Helix 2.5 (Sep 2026) is pretrained on Figure's Index human video and ran three household tasks zero-shot in 30 unseen homes at 56% success.
Ch. 15Honor
ELI5The Shenzhen smartphone maker whose humanoid ran the 2026 Beijing half marathon faster than any human.
RealHonor 荣耀, Shenzhen. Its humanoid won the 19 Apr 2026 Beijing E-Town humanoid half marathon in 50 min 26 s, faster than the human world record. Robot specifications not published as of Sep 2026.
Ch. 16Hotel delivery robot
ELI5A locker on wheels that rides the lift by itself, calls the room phone and opens its door when the guest taps the screen.
RealCompartment delivery robot with lift and access-control integration, lockable bins, phone or app notification at the door. Pudu FlashBot, Keenon BUTLERBOT W3 and QuikBot are the units seen in Singapore and China.
Ch. 17Human video data
ELI5Videos of people doing everyday tasks, used to teach robots what good movement looks like.
RealVideo of humans performing tasks, from the internet or collected on purpose, used for pretraining. It lacks robot actions; labs recover approximate actions with hand pose tracking or latent-action models. The main new fuel of 2026 (Figure Index, Dyna-2, Generalist).
Ch. 11Human-to-robot transfer
ELI5Teaching a robot by showing it lots of videos of people doing chores, then giving it only a little robot practice.
RealPretraining a robot policy on video of humans (head-camera or phone footage with hand-pose labels) and fine-tuning on a smaller amount of robot data. Dyna-2 (15 Aug 2026, 1M+ hours) and Figure Helix 2.5 (17 Sep 2026, Index video) each claimed a scaling law for it within five weeks of each other. Company claims, not independently tested.
Ch. 15Humanoid form factor
ELI5The decision to build a robot with two legs, two arms and a head so it fits the doors, stairs, shelves and tools already made for people.
RealA design choice that trades mechanical simplicity for compatibility with human spaces: 1.6 to 1.9 m tall, roughly human reach and payload, bipedal or with a wheeled lower body. Apptronik and Neura both offer wheeled variants because a flat factory floor does not need legs.
Ch. 15Humanoid robot
ELI5A robot shaped like a person, with legs, arms, a torso and a head, so it can use stairs, doors and tools built for people.
RealA robot with a human body plan: two legs (or a wheeled base on some variants), two arms, a torso and a sensor head, typically 23 to 75 actuated degrees of freedom, built to work in spaces designed for people.
Ch. 01Hydraulic actuator
ELI5A muscle made of oil under huge pressure. Very strong, but it needs a pump and hoses, and it leaks.
RealA cylinder or rotary actuator driven by oil at 200 to 350 bar through servo valves; 5 to 10 times electric force density at the actuator but 30 to 60% system efficiency. Boston Dynamics retired hydraulic Atlas in April 2024.
Ch. 02Imitation learning
ELI5Learning by copying: watch a person do it many times, then do the same.
RealTraining a policy from human demonstrations of the task. The main pretraining method for every flagship VLA. Capped by demonstration quality, and errors compound when the robot drifts into states the demonstrations never covered.
Ch. 10Impedance control
ELI5Making the robot's hand act like it's held by a spring you picked: push it and it gives a bit, let go and it comes back.
RealControl that imposes a chosen relation between motion and force at the end effector, F = K·Δx + D·ẋ (+ M·ẍ). Needs torque-controllable joints. Soft K for contact with people, stiff K for placement.
Ch. 08IMU (inertial measurement unit)
ELI5An inner ear on a chip. It feels turning and pushing, so the robot knows which way is down and how it is moving, but it slowly loses track of where it is.
RealA package of three-axis gyroscopes and accelerometers, usually MEMS, reporting angular rate and specific force at hundreds to thousands of hertz. Consumer MEMS parts cost US$1 to 10 and drift 1 to 10 degrees per hour; integrated position error grows with time squared, so IMUs are fused with absolute fixes.
Ch. 05Industrial fund
ELI5A government-backed investment pot set up to grow one industry, such as robots, in one city.
RealGovernment guidance or industry funds, often co-invested with private capital. Examples: Shenzhen's ¥10bn AI and robotics fund; local funds that require the startup to register or build in the city.
Ch. 18Industrial robot
ELI5The big yellow or orange arm behind a fence in a car plant. It welds, paints, lifts and stacks all day and never gets bored.
RealISO 8373: an automatically controlled, reprogrammable manipulator with three or more axes, fixed or mobile, for industrial automation. More than 600,000 were installed in 2025 and 5 million are in operation.
Ch. 17Industry chain
ELI5Everyone who touches a robot, from the miner who digs up the metal to the shop that uses the robot, in order.
RealThe Chinese framing of an industry as upstream (materials and core components), midstream (robot makers) and downstream (applications and integrators). Officials and sellers use it constantly; Morgan Stanley puts China at about 63% of the humanoid value chain.
Ch. 18Inference
ELI5The model doing its job after training, deciding the next move right now.
RealRunning a trained model to produce outputs. On robots it runs onboard (for example Jetson Thor, 130 W) under hard latency limits, which is why brains split into slow large models and fast small ones.
Ch. 10Injection moulding
ELI5Melting plastic pellets and shooting them into a cold steel mould. Every LEGO brick is made this way.
RealA screw melts polymer and injects it at 500 to 2,000 bar into a cooled mould; cycle time is set by cooling, about 2 to 4 s per mm² of wall. A US$9,000 single-cavity tool makes a 50 g bracket at about US$0.45 and beats printing above about 1,500 parts.
Ch. 07Inspection round
ELI5A regular walk-round check of every robot, like a nurse's ward round.
RealA scheduled patrol inspection of deployed equipment to catch faults before they stop work: sensor cleanliness, wheel wrap, battery health, firmware version.
Ch. 13Integral windup
ELI5The controller keeps adding up how far off it is while the motor is already maxed out, then overshoots badly when it finally gets there.
RealIntegrator accumulation during actuator saturation, which causes large overshoot and slow recovery. Fixed by clamping (freeze the integrator while saturated) or back-calculation.
Ch. 08Intervention
ELI5A person grabbing the controls when the robot is about to get it wrong.
RealA human takeover during autonomous operation, remote or local, logged with the robot's observations and the corrective action. Interventions per hour is a core autonomy metric, and intervention data is a direct training input (π*0.6 Recap).
Ch. 11Inverse kinematics
ELI5Given where you want the hand, work out how to bend every joint to get it there.
RealThe map from a desired end-effector pose to joint angles. Two-link arms have closed-form solutions (two per target); redundant arms and humanoids have infinitely many and are solved numerically, usually through the Jacobian, with limits and balance as extra goals.
Ch. 08Inverted pendulum
ELI5A broom balanced upright on your palm: all the weight on top of a stick, always about to fall.
RealA point mass on a massless leg pivoting at the foot. The linear inverted pendulum model (constant CoM height) gives closed-form CoM dynamics used for ZMP preview control, capture point and MPC footstep planning; its constant-height assumption explains bent-knee classical gaits.
Ch. 09Involution
ELI5The Chinese word for an industry that runs harder and harder without anyone earning more, because everyone copies everyone.
Real内卷 (nèijuǎn): destructive over-competition. The NDRC used the idea on 27 Nov 2025 when it warned that more than 150 Chinese firms were making humanoids, over half newcomers and many highly similar, and pushed for consolidation and R&D over output.
Ch. 16IP rating
ELI5A two-number code for how well the robot keeps out dust and water. IP67 is dust-tight and survives a quick dunk; IP20 means keep it dry.
RealIngress protection code (IEC 60529): first digit solids (6 = dust-tight), second digit water (4 = splashing, 7 = temporary immersion). Atlas and Unitree B2 are IP67; Pudu KettyBot is IP20.
Ch. 06IPO
ELI5When a private company first sells shares to the public on a stock market.
RealInitial public offering. Unitree raised about ¥6.1bn (US$905m) on the STAR Market in Aug 2026; AgiBot began a Hong Kong IPO process; Agility is going public by SPAC at US$2.5bn. Chinese speakers usually say 上市 (to list).
Ch. 18Jacobian
ELI5A table that says how fast the hand moves in each direction when each joint turns a little.
RealThe matrix J(q) of partial derivatives mapping joint velocities to end-effector velocity (v = J q̇) and end-effector force to joint torques (τ = Jᵀ F). Its inverse or pseudo-inverse drives numerical IK and operational-space control.
Ch. 08Jetson
ELI5NVIDIA's family of small AI computers built to go inside robots, drones and cameras.
RealNVIDIA's embedded GPU modules: Orin (Nano, NX, AGX) and Thor (T4000, T5000). T5000 offers 2,070 FP4 TFLOPS, 128 GB memory and up to 130 W; prices rose 50 to 101% on 22 Jul 2026.
Ch. 06Jitter
ELI5When the delay keeps changing. Always being a bit late is manageable; being randomly early or late makes you drop the ball.
RealVariation in latency between cycles. It erodes a control loop's phase margin unpredictably, which makes it more damaging than a constant delay. EtherCAT keeps synchronisation jitter under a microsecond.
Ch. 06Joint
ELI5The place where two stiff pieces of a robot meet and can move, like your knee.
RealA connection between two links that allows one kind of relative motion, usually rotation (revolute) or sliding (prismatic); an actuated joint has its own motor.
Ch. 01Joint module
ELI5A robot's knee in a can: motor, gears, sensors and electronics sealed together, with a twist coming out of one end.
RealAn integrated rotary actuator: frameless motor, reducer, dual encoders, optional torque sensor and brake, cross roller bearing and driver board on a hollow shaft. LeJu pays about US$202 per axis at volume; retail modules run US$385 to 1,440+.
Ch. 02Kalman filter
ELI5A habit written as maths: guess where something is now, then correct the guess with each new measurement, trusting whichever is less fuzzy.
RealA recursive estimator that alternates prediction with a process model and update with measurements weighted by the Kalman gain. The extended Kalman filter (EKF) linearises nonlinear models and runs in drone flight controllers, robot state estimators and battery management systems.
Ch. 05Keenon Robotics
ELI5The Shanghai company behind the DINERBOT tray robots. Haidilao's robot waiters since 2018.
RealFounded 2010 in Shanghai by Tony Li; 100,000+ service robots shipped (Nov 2024), 70+ countries; 22.7% of global commercial service robot shipments and 40.4% of food delivery robots in 2024 (IDC); Series D US$200M from SoftBank Vision Fund 2 in 2021.
Ch. 17Kepler
ELI5A Shanghai maker whose K2 Bumblebee uses screw-driven linear actuators like Tesla's Optimus and claims 8 hours per charge.
RealKepler 开普勒, Shanghai. K2 Bumblebee 大黄蜂: hybrid architecture combining planetary roller-screw linear actuators with rotary actuators, straight-knee gait, up to 30 kg dual-arm payload, claimed 8 h runtime, ¥248,000 (about US$34,000), mass production announced 26 Sep 2025.
Ch. 16Kinematic chain
ELI5Links and joints joined end to end. Move the shoulder and everything after it comes along.
RealAn assembly of links connected by joints; open chains (arms, legs) end in a free tool or foot, closed chains (linkages, parallel robots) loop back on themselves.
Ch. 01Large model
ELI5What Chinese engineers call any big AI model, the kind behind chatbots and now robot brains.
RealChinese industry shorthand (大模型) for large pretrained models: LLMs, vision-language models and VLAs. In meetings it often means the high-level 'big brain' model a robot maker licenses or builds.
Ch. 10Latency
ELI5The delay between something happening and the robot reacting to it. Like the lag on a video call, except a lagging robot drops the cup.
RealThe time from a sensor event to the matching actuator response, summed across sensing, transport, computation and actuation. Latency eats stability margin: 20 ms of extra delay costs a 10 Hz loop about 72 degrees of phase margin, so each layer of the control stack gets a latency budget sized to its rate.
Ch. 14Leader-follower arm
ELI5You move a small copy of the robot arm by hand and the real arm copies every joint.
RealA teleoperation setup where a kinematically matched (often scaled, cheap) leader arm is moved by hand and a follower robot arm tracks its joint angles, while cameras and joint states are recorded. ALOHA (about US$20k, 2023) and GELLO (under about US$300 in parts) are the reference designs.
Ch. 11Learning curve
ELI5Every time you make twice as many, each one gets cheaper by about the same percentage.
RealUnit cost falls by a fixed fraction with each doubling of cumulative volume (Wright's law). Leju's actuated axis fell from US$433 to US$202 over 100x volume: about 11% per doubling, an 89% curve (estimate from corematter data).
Ch. 07Leju Robotics
ELI5A Shenzhen maker that sold 577 full-size Kuavo humanoids in 2025, runs Huawei's HarmonyOS on them and is listing on Shenzhen's ChiNext board.
RealLeju Robotics 乐聚机器人, Shenzhen, founded 2016 by Leng Xiaokun. Kuavo 夸父 full-size biped on OpenHarmony with Huawei Pangu models. 2025: 577 units, about ¥178 million revenue, ASP about ¥308,100. ChiNext IPO application accepted May 2026; Foshan plant with Dongfang Precision at about one robot every 30 minutes.
Ch. 16LFP (lithium iron phosphate)
ELI5A battery chemistry that is cheap, safe and long-lived, but heavier for the same energy.
RealLiFePO4 cathode chemistry: 150 to 210 Wh/kg cells, 3,000 to 10,000+ cycles, thermal runaway onset about 270 °C, about US$45 to 70/kWh cells in China (2025 to 2026 estimate); 3.2 V nominal.
Ch. 06LiDAR
ELI5A laser tape measure spun around very fast. Each laser echo is one exact dot in 3D; millions of dots make a shape of the room.
RealLight detection and ranging: pulsed-laser time of flight swept by a spinning head, mirrors, prisms or a flash array, giving 10^5 to 10^7 points per second at about 1 to 3 cm accuracy. Blind to glass, mirrors and very dark surfaces. Robot units run from about US$419 (Unitree L2, Sep 2026) upward.
Ch. 05Lift integration
ELI5Wiring the robot to the lift so it can call it, get in and press its floor without a person.
RealA software and hardware link between a robot or fleet system and the lift controller so robots can call cars and select floors. Singapore standardises the robot-to-infrastructure interface in SS 713:2025. Chinese vendors say 梯控.
Ch. 12LimX Dynamics
ELI5A Shenzhen maker of a shape-shifting research robot that becomes a biped, a wheel-legged robot or a two-arm bench unit for under US$10,000.
RealLimX Dynamics 逐际动力, Shenzhen. TRON 2: modular, about 1.57 m, reconfigures into biped, wheel-legged or stationary dual-arm forms, about US$6,800 to US$10,000. Oli full-size biped. Software: COSA, VGM, DreamActor. US$200 million Series B (Feb 2026) and a reported US$200 million pre-IPO round (Jul 2026).
Ch. 16Linear actuator
ELI5An actuator that pushes and pulls in a straight line, like a muscle, instead of turning.
RealA motor driving a ball or planetary roller screw so a rod extends and retracts; on humanoids it pushes a joint through a lever, as in Optimus's 14 linear joints. The screw is about 64% of its cost.
Ch. 02Link
ELI5A stiff piece of the robot between two joints, like a bone between your elbow and wrist.
RealA rigid body in a kinematic chain, connected to neighbouring links by joints; link lengths set the robot's reach and workspace.
Ch. 01Linkage
ELI5Stiff rods and levers joined together, like the pedals and cranks of a bike, that carry motion from a motor to a joint.
RealA mechanism of rigid links and pivots (push rods, four-bars) that transmits motion from a remote motor; stiff and efficient, with a ratio that varies over the joint's range. Common in ankles and in dexterous-hand fingers.
Ch. 03Linkage-driven hand
ELI5A robot hand where small motors in the palm push stiff rods that bend the fingers.
RealA dexterous hand whose fingers are driven by rigid linkages from palm-mounted linear actuators, as in Inspire Robots' RH56 series; stiff and precise with coupled joints.
Ch. 04Localization
ELI5Working out where you are on a map you already have.
RealEstimating the robot's pose against a stored map by matching current sensor data to it. Service robots map once on installation and localise every run; 'localization lost' (定位丢失 dìngwèi diūshī) is a standard field fault.
Ch. 05Log
ELI5The robot's diary of what it did and what went wrong, written by the software.
RealTimestamped records of events, states and errors. Service robots upload operation logs to the maker's cloud (Pudu stores them in China); a repairer outside the maker's partner programme usually cannot read them.
Ch. 13Loop closure
ELI5The moment the robot recognises a place it has been before and uses that to straighten its whole map.
RealIn SLAM, a detected revisit of an earlier place that adds a constraint between distant poses; graph optimisation then removes accumulated drift. False closures from look-alike places bend the map.
Ch. 05MagicLab
ELI5A Suzhou humanoid startup linked to the vacuum-cleaner maker Dreame; its MagicBot is still listed as a prototype.
RealMagicLab 魔法原子, Suzhou (unverified). MagicBot listed at 1.38 m, 54 kg, 42 DoF, about US$50,000, marked prototype by aggregators. Thin public data as of Sep 2026.
Ch. 16Magnesium alloy
ELI5A metal a third lighter than aluminium that pours well into moulds, used for light housings.
RealAZ91 and similar: E 45 GPa, about 150 MPa, 1.81 g/cm³, service to about 120 °C; die-cast for housings where grams matter. Needs corrosion protection.
Ch. 07Magnetic encoder
ELI5A cheap angle sensor that watches a small magnet on the end of the shaft.
RealAn encoder that reads a diametric magnet on the shaft end with a Hall-array chip, typically 12 to 14 bits for about US$10 to 15 (AS5047 class); tolerant of dust, coarser than optical.
Ch. 02Main controller
ELI5The robot's main computer, the one that looks through the cameras and decides what to do next.
RealThe onboard AI computer that runs perception, planning and learned policies, such as an NVIDIA Jetson Thor or Orin, a Horizon RDK or an Intel CPU pair. Chinese engineers call it 主控 and split the stack into 大脑 (planner) and 小脑 (motion controller).
Ch. 06Maintenance and warranty service
ELI5The bundle deal: someone keeps the robot healthy and fixes it when it breaks.
RealThe contract line covering scheduled maintenance plus repair, in or out of warranty. In Chinese distributor contracts it is 维保, short for 维修保养 (repair and upkeep).
Ch. 13Manipulation
ELI5Everything a robot does with its hands after it picks something up: turning, sliding, pressing, folding.
RealPurposeful changing of an object's position or state with arms and hands, including in-hand reorientation. In-hand handling of cables, cloth and deformables is unsolved at human level. Dexterous manipulation is 灵巧操作.
Ch. 04Mapping
ELI5Drawing the map of a place so the robot can find its way next time.
RealBuilding a persistent map (occupancy grid, point cloud or feature map) of an environment, usually on installation day for service robots, and redoing it after a refit.
Ch. 05Mass production
ELI5When the moulds are made and the factory builds the same robot over and over at a low price.
RealProduction on hard tooling at stable yield and volume, with the lowest unit price. Chinese makers announce 量产 early; ask for delivered units, not the announcement.
Ch. 07Master distributor
ELI5The one distributor a maker appoints for a whole country. Everyone else in that country buys through them.
RealExclusive general agent for a territory, usually with minimum purchase commitments, price protection and the right to appoint sub-dealers. Xtrike Robotics claims this role for Pudu in Malaysia; Weston Robot holds it for Unitree in Singapore and Malaysia.
Ch. 17Microcontroller (MCU)
ELI5A tiny, cheap computer on one chip that does one job very fast and very reliably, like spinning one motor.
RealA single-chip processor with on-board memory and peripherals, running bare-metal code or an RTOS. In robots, MCUs run motor current loops at 10 to 40 kHz on each joint's driver board.
Ch. 06Middleware
ELI5The robot's internal post office: programs drop labelled notes in pigeonholes and whoever cares picks them up.
RealA software layer between the operating system and applications that moves typed messages between programs, often across several computers in one robot, with delivery and timing rules. ROS 2 over DDS is the common example; Zenoh is a newer transport.
Ch. 12Midstream
ELI5The companies that put the parts together into finished robots.
RealRobot body makers (本体厂商) such as Unitree, AgiBot and UBTech, which integrate components, write the control software and sell the robot. Chinese midstream firms shipped about 90% of 2025's humanoids.
Ch. 18mmWave radar
ELI5Radar with very short radio waves. It sees through fog and dust and can tell how fast something is coming, but the picture is blurry.
RealMillimetre-wave FMCW radar (76 to 81 GHz in cars) that measures range and, through Doppler, radial velocity per target. Weather-proof and cheap (about US$40 to 300); angular resolution is coarse unless imaging arrays are used.
Ch. 05Mobile manipulator
ELI5An arm on wheels: the cart drives to the shelf and the arm does the picking.
RealA robot that combines a mobile base (AMR or wheeled torso) with one or two arms, so it can both travel and manipulate; wheeled humanoids such as Galbot G1, AgiBot G2 and Pudu D7 fall in this class.
Ch. 01Model predictive control
ELI5Imagine the next half second, pick the best plan, do only the first bit, then imagine again.
RealMPC: at each tick, solve a constrained optimisation over a receding horizon using a dynamics model, apply the first input, re-solve. Legged robots run it at about 25 to 100 Hz over about 0.5 s with a 1 kHz loop underneath (MIT Cheetah, 2018).
Ch. 08MOQ
ELI5The smallest order a supplier will accept.
RealMinimum order quantity: the smallest run a supplier will quote, set by setup cost and material lots. Negotiable against a credible forecast or a higher unit price.
Ch. 07Motion capture
ELI5Recording how a person moves, joint by joint, so a robot can copy it.
RealMocap: measuring human body motion with optical markers, inertial suits or video pose estimation. Retargeted mocap is the reference for imitation rewards (dance, kung fu) and for learned whole-body controllers.
Ch. 09Motion capture suit
ELI5A suit covered in sensors that records how your whole body moves, so a humanoid can copy it.
RealA wearable inertial or optical tracking suit that records human joint angles for retargeting onto a humanoid, used for whole-body teleoperation and motion data. Full humanoid mocap programmes cost about US$80 to 150 per hour all-in (2026 estimate).
Ch. 11Motion control
ELI5The software that turns "walk forward" or "reach there" into exact motor pushes, fast enough to keep the robot upright.
RealThe layers that turn motion targets into joint torques: whole-body control, joint position and velocity loops, and current control. Chinese makers call it 运控 and treat it as the "little brain" (小脑) under the planning model.
Ch. 08Motion planning
ELI5Finding a route for the arm or body that doesn't bump into anything.
RealSearch for a collision-free path through configuration space, with sampling planners such as RRT or optimisation-based planners; MoveIt is the common open-source framework on ROS 2.
Ch. 08Motion retargeting
ELI5Adjusting a human's recorded moves to fit a robot with different leg lengths and stiffer joints.
RealMapping human motion onto a robot's kinematics and joint limits, usually by optimisation over keypoints, while keeping contacts and balance feasible. Figure's Helix 02 S0 trained on 1,000+ hours of retargeted human motion.
Ch. 09Motor driver
ELI5The small circuit board that decides exactly how much electricity each motor coil gets, thousands of times a second.
RealAn inverter of MOSFET or GaN switches plus a microcontroller running FOC that turns battery DC into three-phase motor current at 10 to 40 kHz PWM; about US$46 per axis at volume.
Ch. 02Mould
ELI5A steel block with a part-shaped hole inside. Squirt in melted plastic or metal, let it cool, pop the part out, repeat.
RealThe hardened steel tool that forms a moulded or cast part, with its cavity, cooling channels and ejectors. Die-casting dies in H13 steel last about 50k to 150k aluminium shots. Contracts should state who owns the mould and whether you can move it.
Ch. 07MTBF
ELI5How long the robot runs, on average, before something breaks.
RealMean time between failures: average operating hours between failures. A Fanuc integrator claims 80,000+ h for Fanuc arms; an illustrative humanoid component stack is about 4,545 h (estimates).
Ch. 13MTTR
ELI5How long the robot sits broken, on average, before it works again.
RealMean time to repair: average elapsed time from failure to restored service, including response, travel, parts wait and hands-on repair. For robots repaired in China the parts wait dominates (Unitree ships repaired parts within 20 days of receipt).
Ch. 13Multi-robot dispatch
ELI5Deciding which robot takes which job, like a taxi app picking the nearest driver.
RealTask allocation and scheduling across a fleet: assigning jobs to robots by position, battery and capability, and sequencing them to avoid conflicts. Chinese vendors call the software a dispatch system (调度系统).
Ch. 12Multimodal
ELI5Takes in several kinds of input at once, like pictures, words and body position.
RealA model that processes more than one data type (images, text, audio, joint states, touch) in a shared representation. Every VLA is multimodal.
Ch. 10Navigation
ELI5Planning a route from here to there on the map and following it without bumping into anything.
RealGlobal path planning on a map plus local planning around obstacles, combined with localization. In ROS 2 this is typically the Nav2 stack; service robots add lift and door integration.
Ch. 05NdFeB magnet
ELI5The super-strong rare earth magnets that make small motors powerful. China makes almost all of them.
RealSintered neodymium-iron-boron permanent magnet, with dysprosium or terbium added for heat resistance above about 100 °C; about 1 kg per humanoid, and China makes about 91 to 94% of the world's supply.
Ch. 02NMC (nickel manganese cobalt)
ELI5A battery chemistry that packs more energy per kilo than LFP, so robots can carry less weight, but it costs more and burns hotter if it fails.
RealLiNiMnCoO2 cathode chemistry (Chinese industry says 三元 sānyuán): 220 to 300 Wh/kg cells, 1,000 to 2,500 cycles, runaway onset about 210 °C, about US$70 to 100/kWh; 3.6 to 3.7 V nominal. Usual choice for humanoids.
Ch. 06Node
ELI5One small program inside the robot that does one job, like reading the camera.
RealIn ROS 2, a process or component that performs one function and communicates with other nodes through topics, services and actions. A robot typically runs dozens.
Ch. 12Noetix
ELI5A Beijing maker whose small Bumi humanoid sells for under ¥10,000, the price floor of the whole market.
RealNoetix 松延动力 (rendering unverified), Beijing. Bumi small humanoid listed at ¥9,998, seen at ¥9,118 after subsidies and discounts (Jun 2026).
Ch. 16NRE
ELI5The one-time engineering bill a supplier charges to set up your job, before any parts are made.
RealNon-recurring engineering: one-off design, setup, fixture and qualification charges, separate from tooling and the per-unit price. Negotiate whether it is refunded against volume.
Ch. 07Obstacle avoidance
ELI5Seeing something in the way and going around it or stopping.
RealLocal reactive planning that slows, stops or re-routes the robot around detected obstacles from lidar, depth cameras, ultrasonic and bumper inputs. A core selling point and a common complaint in service robots.
Ch. 05ODM
ELI5A factory that has already designed a product and will put your name on it.
RealOriginal design manufacturer: the factory owns the design and often the tooling, sells it to several brands and usually sets a minimum order. Fast and cheap to start; weak on differentiation and control.
Ch. 07OEM (contract build)
ELI5You bring the design, the factory builds exactly what you drew.
RealIn a supply contract, the factory builds to the customer's design, and the customer owns the design and usually the tools it paid for. Distinct from "robot OEM", the maker that sells robots under its own brand (本体厂商).
Ch. 07On-site service
ELI5A technician comes to the robot instead of the robot going to the technician.
RealField repair at the customer's site. Tennant services Brain Corp robots next business day if requested before 13:00 CT; PUDU Care Standard includes unlimited on-site repairs in the US and Canada.
Ch. 13Open loop
ELI5Following the recipe without tasting. A toaster runs for two minutes whether the bread is frozen or not.
RealControl that applies a pre-planned command with no measurement of the result. Accurate only as far as the model and the world's repeatability allow; in robots it survives as feedforward under a feedback loop.
Ch. 08Open source
ELI5Free to download and change, so you do not have to build it from nothing.
RealCode or model weights released under a licence that allows use and modification. Open robot models as of Sep 2026: openpi (π0, π0-FAST, π0.5, Apache-2.0), GR00T N1.6, SmolVLA, OpenVLA.
Ch. 10Open-RMF
ELI5An air traffic controller for a building: every robot brand asks it before using a corridor or a lift.
RealOpen Robotics Middleware Framework: open-source software for shared traffic scheduling, lift and door access and task allocation across multi-vendor fleets. Co-launched in Singapore in 2018 by the National Robotics Programme with Changi General Hospital, CHART, IHiS, HOPE Technik and OSRF; governed by the Open Source Robotics Alliance since 2024.
Ch. 12Operating system
ELI5The timetable keeper for one computer: it decides which program runs when and who gets the memory.
RealSoftware that schedules processes and manages memory and devices on one computer. Robots run general Linux on the main computer, real-time Linux or an RTOS (FreeRTOS, Zephyr, QNX, VxWorks) where deadlines matter. ROS is middleware on top of an operating system despite its name.
Ch. 12Opportunity charging
ELI5Topping up the battery for a few minutes whenever the robot has a gap, like plugging in your phone during lunch.
RealShort partial charges taken during natural pauses in work rather than one long charge from empty. Apollo 2 combines it with pack swaps and a tether for 22 h a day; Figure 03 does it by stepping onto a 2 kW inductive pad.
Ch. 15Order
ELI5A customer's promise to buy, which is not money until the robot is delivered and paid for.
RealA purchase commitment, often framework or multi-year and cancellable. Agility claims over US$300m of multi-year orders; Chinese makers announce 订单 by value. Ask what share is delivered and paid.
Ch. 18OTA update
ELI5Sending new software to the robot over the internet, like a phone update.
RealOver-the-air delivery of firmware, software and model weights, ideally with A/B partitions so a failed update rolls back. OTA and cloud links are also the main attack surface, as the 2025 to 2026 Unitree disclosures showed.
Ch. 06Parallel gripper
ELI5Two flat jaws that slide together to squeeze something, like a vice. Cheap, strong and hard to break.
RealA two-jaw gripper whose fingers translate toward each other, usually driven by one motor through a screw or rack. The workhorse of research arms, Dyna stations and industrial picking.
Ch. 04Payload
ELI5How heavy a thing the robot can carry or lift.
RealThe mass a robot can carry at its tool or on its body at rated speed and reach; arm payload falls as reach grows, and humanoids often quote sustained and peak figures separately (Atlas 30 kg and 50 kg).
Ch. 01Peak torque
ELI5The hardest the motor can twist for a few seconds before it gets too hot.
RealMaximum torque an actuator delivers briefly, typically 3 to 5 times its continuous rating, limited by winding temperature and driver current; spec sheets headline it.
Ch. 02Perception
ELI5The software that turns camera pictures and laser dots into facts: that is a person, that is a cup, I am at table 12.
RealThe pipeline from raw sensor data to a world model: detection, segmentation, pose estimation, mapping, localization and state estimation. In humanoids it is increasingly learned inside a VLA; service robots still run classic modules.
Ch. 05PID
ELI5Three reflexes added together: push harder the further off you are, harder still the longer you've been off, and ease off when you're closing in fast.
RealProportional, integral, derivative controller: u = Kp·e + Ki·∫e dt + Kd·de/dt. P sets stiffness, I removes steady offset, D adds damping. Practical versions filter D (N about 8 to 20), take the derivative of the measurement and add anti-windup. About 97% of process loops are PID.
Ch. 08Pilot deployment
ELI5A small trial: a few robots on one site for a few months, to see whether they earn their keep before anyone signs a big order.
RealA limited trial, usually 1 to 10 robots at one customer site, run to measure task success, throughput, uptime and integration cost before a commercial rollout. Most western humanoid customers in Sep 2026 are pilots; Agility's GXO contract and Dyna's Din Tai Fung rollout are among the few that converted.
Ch. 15Planet carrier
ELI5The frame that holds the planet gears' axles. As the planets roll round, it turns slowly, and that's the output.
RealThe member carrying the planet pins; with the ring fixed it is the output, turning at sun speed ÷ (1 + ring ÷ sun).
Ch. 03Planet gear
ELI5The gears that roll around the sun gear, like planets in orbit.
RealThe gears meshing with both sun and ring in a planetary set, mounted on pins in the carrier; three or four share the load.
Ch. 03Planetary gearbox
ELI5Gears arranged like a solar system: a sun in the middle, planets around it, and a ring outside. Small, strong and easy to push backwards.
RealA gear stage with a central sun gear, three or four planet gears on a carrier and an internal ring gear. With the ring fixed the ratio is 1 + ring teeth ÷ sun teeth, 3:1 to 10:1 per stage, efficient and backdrivable. Used in quasi-direct-drive legs (Unitree) and as first stages.
Ch. 03Planetary roller screw
ELI5A screw that turns spinning into pushing, with little threaded rollers between the shaft and the nut, so it can push very hard and take knocks.
RealA rotary-to-linear screw in which threaded rollers orbit between a threaded shaft and nut, giving many contact lines and 3 to 10 times the load of a same-size ball screw. Used in humanoid linear actuators (14 in Optimus); about 64% of a linear actuator's cost (estimate). The hardest humanoid part to scale: special steel, thread grinding, heat treatment.
Ch. 03PMSM
ELI5A brushless motor with magnets in the spinning part, driven with smooth wave-shaped current so it turns without jerks.
RealPermanent magnet synchronous motor: magnets on the rotor, sinusoidally wound stator, driven by FOC; the standard robot joint motor. Unitree lists low-inertia internal-rotor PMSMs across its humanoids.
Ch. 02Point cloud
ELI5Thousands of dots floating in 3D, each one a spot a laser or depth camera touched. Together they show the shape of things.
RealA set of 3D points, often with intensity and time stamps, produced by lidar or depth cameras. It carries geometry without meaning; segmentation and detection add labels.
Ch. 05Policy
ELI5The robot's trained reflexes: given what it senses now, what it does next.
RealA function, usually a neural network, from observations (joint states, IMU, commands, history, sometimes height maps or images) to actions. Locomotion policies typically output joint position targets at about 50 Hz for PD loops at about 1 kHz.
Ch. 09Position control
ELI5Telling a joint "go to 42 degrees and stay there, whatever it takes".
RealControl mode that tracks a joint or end-effector position with high-gain feedback. Precise and stiff, and blind to contact forces; the default on industrial arms with high-ratio reducers.
Ch. 08Power and force limiting
ELI5The robot is allowed to bump you, but only gently enough not to hurt.
RealA collaborative safety function that caps the force and pressure a robot can apply to a person, with limits per body region (tens of newtons to about 150 N quasi-static) from ISO/TS 15066, now folded into ISO 10218-2:2025.
Ch. 12Power consumption
ELI5How much electricity the robot uses every second it runs.
RealElectrical power drawn, in watts, average and peak. Optimus-class figures of about 100 W idle, 500 W walking and 700 W+ loaded are unverified; peak spikes can trip battery over-current protection.
Ch. 06Power grasp
ELI5Holding something with your whole hand wrapped round it, like a hammer. Strong and forgiving.
RealA grasp with palm and finger surfaces enclosing the object; high force, low precision, tolerant of position error.
Ch. 04Precision grasp
ELI5Holding something with just your fingertips, like picking up a coin. Exact but weak, and it needs a good sense of touch.
RealA fingertip grasp that allows fine positioning and in-hand motion at low force; depends on tactile feedback and accurate finger control.
Ch. 04Predictive maintenance
ELI5Using the robot's own data to spot a part about to fail and replacing it just in time.
RealCondition-based maintenance from telemetry. Fanuc ZDT connects 40,000+ arms, detects reducer wear from motor torque weeks before failure and has prevented 4,000+ downtime cases. Makers own this data loop.
Ch. 13PREEMPT_RT
ELI5A change to Linux that lets urgent jobs interrupt everything else, so Linux can run a robot's 1,000-times-a-second control loop.
RealThe real-time patch set that makes the Linux kernel fully preemptible for bounded latency; reported merged into mainline in Linux 6.12 (Nov 2024). Used with ros2_control for the 1 kHz layer.
Ch. 06Pretraining
ELI5The long general schooling before the robot learns its actual job.
RealThe first, largest training stage on broad data (web images and text, many robots' demonstrations, human video) before task-specific post-training. π0 pretrained on 10,000+ hours from 7 robot configurations.
Ch. 10Preventive maintenance
ELI5Fixing things on a timetable before they break.
RealTime- or usage-based upkeep. PUDU Care Standard includes 4 preventive visits a year; a US reseller makes Pudu's warranty conditional on a quarterly maintenance plan.
Ch. 13Price war
ELI5When 150 companies sell nearly the same robot, the price falls until only the biggest survive.
Real价格战: the 2025 to 2026 collapse in Chinese entertainment-class humanoid prices. Unitree's average humanoid price fell 72% from ¥593,400 (2023) to ¥167,600 (9M 2025); the R1 Air lists at ¥29,900 and Noetix Bumi at ¥9,998. Industrial humanoids (Walker S2, Galbot G1) held ¥600,000 to ¥760,000.
Ch. 16Prismatic joint
ELI5A joint that slides in a straight line, like a drawer.
RealA one-DOF joint that allows translation along a single axis, such as a lifting column, a gantry axis or a linear actuator's rod.
Ch. 01Production line
ELI5The row of workstations a robot moves through as it gets built and checked.
RealThe sequenced stations, fixtures, software and inspection points that build a product. Figure's BotQ: 150+ networked workstations, 50+ in-process inspection points, one robot an hour by Apr 2026 on a line rated at 12,000 a year.
Ch. 07Proprioception
ELI5The robot's sense of its own body: where each joint is, how hard each motor is pushing, which way it is tipping. Like knowing where your hand is with your eyes shut.
RealSensing of the robot's internal state: joint angles from encoders, motor currents, joint torques, IMU orientation and rates, foot contact and battery telemetry. Sampled at 1 to 40 kHz and used by balance and joint control loops.
Ch. 05Prototype
ELI5An early working robot built to test the idea, usually by hand and at high cost.
RealA functional pre-production unit, typically machined and printed, used to prove the design before tooling. Prototype-to-production is where most hardware schedules slip.
Ch. 07Pudu Robotics
ELI5The Shenzhen company behind the cat-face BellaBot and the CC1 scrubber. The biggest service robot maker by units shipped.
RealFounded 2016 in Shenzhen by Felix Zhang Tao; 130,000+ robots shipped to 85+ countries by Sep 2026; cleaning robots are more than 70% of revenue; raised about US$150M in Apr 2026 at more than US$1.5B valuation; preparing a Hong Kong listing.
Ch. 17PWM
ELI5Switching the power fully on and off very fast; the share of time it's on sets how much the motor gets.
RealPulse-width modulation: switching transistors at a fixed frequency (10 to 40 kHz in joint drivers) and varying the duty cycle to set average phase voltage.
Ch. 02Quadruped robot
ELI5A robot dog. Four legs make it far steadier than two, so it can trot over rubble and stairs.
RealA four-legged walking robot, usually with three actuated joints per leg (12 in total), a floating base balanced by a controller, and LiDAR or cameras for terrain; Unitree Go2 and Boston Dynamics Spot are examples.
Ch. 01Quasi-direct drive
ELI5A big flat motor with only a little gearing, so the joint is quick, springy to push and can feel the ground through its own motor.
RealQDD: a large-radius high-torque motor with a 6 to 10:1 planetary stage; low reflected inertia and friction make motor current an honest force signal. Used by Unitree and the MIT Mini Cheetah lineage.
Ch. 02Rare earth
ELI5Special metals that make the strong magnets inside every robot motor. China digs up and cleans most of them.
RealSeventeen elements; neodymium and praseodymium make NdFeB magnets, and dysprosium and terbium keep them magnetised when hot. China: about 70% of mining, 90% of refining, 99% of heavy rare earths. Licences on seven since 4 Apr 2025; an expanded package suspended until 10 Nov 2026.
Ch. 18Rated torque
ELI5How hard the motor can twist all day without overheating.
RealContinuous torque an actuator can hold indefinitely at rated temperature rise, set by copper loss (I²R) and cooling; the number a working robot lives on.
Ch. 02Real-robot data
ELI5Recordings made on an actual robot body, with every motor move logged.
RealData captured on physical robot hardware, by teleoperation or autonomous runs, with synchronised camera frames, joint states and commanded actions. The scarcest and most valuable layer of the data pyramid; about 300,000 hours existed worldwide in 2025.
Ch. 11Real-time
ELI5A job where a late answer counts as a wrong answer, like catching a ball.
RealA system whose correctness depends on meeting timing deadlines. Hard real time treats a missed deadline as failure (current loops, safety stops); soft real time tolerates occasional misses with degraded quality.
Ch. 06Reducer
ELI5The robot's lowest bicycle gear, fixed in place. A small motor spins fast and weak; the reducer makes the joint turn slowly and push hard.
RealA transmission between motor and joint that divides speed and multiplies torque by a fixed ratio. Robot reducers are harmonic (50:1 to 160:1), planetary (3:1 to 10:1 per stage), cycloidal or RV. About 36% of a rotary joint module's cost is the reducer (estimate, 2025).
Ch. 03Redwood
ELI5The small brain inside 1X's NEO. It runs on the robot's own chip a few times a second, and hands over to a remote human when it is stuck.
Real1X Technologies' onboard vision-language-action model for NEO: about 160M parameters running near 5 Hz on the robot's Jetson Thor, covering navigation, doors, retrieval and whole-body coordination. Paired with Expert Mode teleoperation and, since Jan 2026, a 1X World Model that predicts the visual result of an action before the robot takes it.
Ch. 15Reflected inertia
ELI5How heavy the spinning motor feels from the joint's side. A higher gear ratio makes it feel much heavier, like a flywheel, so impacts hit harder.
RealMotor rotor inertia seen at the output: N² × J_rotor for ratio N. At 100:1 it is 10,000 times the rotor's own inertia; quasi-direct drive keeps it about 100 times lower than harmonic joints (estimate).
Ch. 03Reinforcement learning
ELI5Learning by trying, scoring points for good moves and losing points for falls, millions of times.
RealRL: training a policy to maximise cumulative reward from interaction. For legged robots, run in GPU-parallel simulation (thousands of environments), then transferred to hardware; the standard way to build locomotion and whole-body controllers as of 2026.
Ch. 09Remote diagnosis
ELI5Working out what is wrong with the robot over the internet before anyone drives out.
RealFault analysis from telemetry, fault codes and logs through the maker's cloud. Gausium reported solving 40% of problems remotely (2022). Requires access to the maker's diagnostic tools.
Ch. 13Remote operations and maintenance
ELI5Fixing or driving the robot from another city through the internet.
RealRemote monitoring, fault clearing, configuration and teleoperated takeover of deployed robots through the maker's cloud link. Gausium reported solving 40% of problems remotely (2022). The same link is the main cyberattack surface.
Ch. 12Rental
ELI5Paying by the day or month for a robot instead of buying it. The rent usually includes the fixing.
RealOperating lease of a robot, often bundled with installation, mapping, software and maintenance (robot-as-a-service). Published Southeast Asian rates: BellaBot RM59 a day and KettyBot RM39 a day in Malaysia; Singapore rates are not published.
Ch. 17Repair
ELI5Fixing a robot that has broken.
RealRestoring a failed machine to working order by adjusting, recalibrating or replacing parts or modules. For service robots, most hardware repair is a module swap with maker-supplied parts.
Ch. 13Repeatability
ELI5How close the robot gets to the same spot each time it goes back. It can be very repeatable and still miss the spot you meant.
RealThe spread of positions when a robot returns to one taught pose, typically 0.02 to 0.1 mm on industrial arms (ISO 9283); absolute accuracy against world coordinates is often 10 to 100 times worse before calibration.
Ch. 01Response time
ELI5How long you wait between reporting a problem and someone starting to fix it.
RealTime from fault report to first action (remote or on site). Gausium's rule: 1 hour for severe, 2 hours normal, 4 hours complex (2022); Pudu claims customer service replies within 15 minutes.
Ch. 13Restaurant delivery robot
ELI5The tray robot with the cat face. It carries four trays of food to a table and a light tells the guest which tray is theirs.
RealTray-stack delivery robot for food service, typically 1.3 to 1.4 m tall, 4 trays, 40 kg payload, table-number dispatch from a tablet, ceiling-marker or LiDAR localisation. Pudu BellaBot and Keenon DINERBOT are the two market leaders.
Ch. 17Return to factory
ELI5Sending the broken robot or part all the way back to the maker to be fixed.
RealDepot repair at the maker's own facility. Unitree required robots to be shipped to Hangzhou at the customer's cost; the Z1 arm's repaired parts ship within 20 days of receipt.
Ch. 13Revenue
ELI5The money customers actually paid the company.
RealRecognised sales. Unitree 2025: ¥1.708bn, up about 4.3x, with ¥278m GAAP net profit. Figure and Agility have not disclosed revenue.
Ch. 18Reverse knee
ELI5A leg that bends backward at the knee, like a bird. The heavy motors sit close to the hip, so the leg swings fast with less effort.
RealA leg layout, inherited by Digit from Agility's Cassie, in which the knee points backward and the shin runs forward to the ankle. It keeps the heavy actuators near the hip, lowers leg inertia and lets the foot land under the body without copying a human gait.
Ch. 15Revolute joint
ELI5A joint that turns, like a door hinge or your elbow.
RealA one-DOF joint that allows rotation about a single axis; almost every joint on arms, legs and humanoids is revolute.
Ch. 01Reward function
ELI5The scoring rules: points for walking at the right speed, penalties for falling or wasting energy.
RealThe scalar signal RL maximises, built from weighted terms such as velocity tracking, uprightness, energy, action smoothness, foot clearance and collision penalties. Poorly designed rewards produce odd but high-scoring gaits.
Ch. 09Reward model
ELI5A second AI that watches the robot and says how close it is to getting the job done.
RealA learned model (reward or value function) that scores progress or success from observations, so reinforcement learning and data selection can run without a human grader. DYNA-1 is built around one; π*0.6 uses a 670M value function.
Ch. 10Right to repair
ELI5Laws that make makers share parts, tools and manuals so you can get things fixed elsewhere.
RealLegal duties on makers to supply parts, documentation, tools or data to owners and independent repairers. The EU directive (from 31 Jul 2026) does not list robots; the EU Data Act gives raw data access; Minnesota covers commercial equipment; nothing found in Singapore or ASEAN.
Ch. 13Ring gear
ELI5The big outer ring with teeth on the inside that the planets roll against.
RealThe internal gear enclosing a planetary set, usually fixed to the housing. Engineers say 内齿圈 or 齿圈.
Ch. 03RoboFab
ELI5Agility's own robot factory in Oregon. It could build 10,000 robots a year, and today it builds fewer than 100.
RealAgility Robotics' 70,000 sq ft factory in Salem, Oregon, with a stated capacity of 10,000 Digits a year. Agility's SPAC filing (26 Aug 2026) says it builds fewer than 100 robots a year today and expects triple digits next year.
Ch. 15Robot
ELI5A machine that can sense what is around it, decide what to do and move something in the real world, over and over without a person steering each motion.
RealA programmable machine with actuated joints or wheels, sensors and a controller that closes a sense, think, act loop to perform physical tasks with some degree of autonomy.
Ch. 01Robot arm
ELI5A mechanical arm bolted to the floor or a table that moves a tool to exact spots, like a very precise crane.
RealA serial manipulator: a fixed base and a chain of usually six revolute joints ending in a tool flange, rated by reach, payload and repeatability.
Ch. 01Robot body (本体)
ELI5The robot hardware itself: frame, joints, sensors and battery, without the job-specific software.
Realběntǐ: industry term for the physical robot platform as sold by its maker, as distinct from components upstream and applications or solutions downstream.
Ch. 01Robot brain company
ELI5A company that makes only the robot's thinking software and sells it to anyone who builds a body, the way Microsoft sold Windows to PC makers.
RealA firm that trains a robot foundation model and licenses it across embodiments without building its own robot: Physical Intelligence (π models), Skild AI (Skild Brain), NVIDIA (GR00T). Their valuations re-rated about 3x per round in 2025 to 2026 on little or no revenue.
Ch. 15Robot density
ELI5How many robots a country has for every 10,000 factory workers.
RealIndustrial robots in operation per 10,000 manufacturing employees (IFR). 2024: South Korea 1,220, Singapore 818 (2nd), Germany 449, Japan 446, US 307, China 166 after a denominator change, global average 132.
Ch. 18Robot OEM (本体厂商)
ELI5The company that builds and sells the robot itself, like Unitree or UBTech.
Realběntǐ chǎngshāng: a maker of complete robot bodies that buys or builds components and sells to integrators, distributors or end users.
Ch. 01Robot Park
ELI5A big practice hall where dozens of Apollo robots do real jobs all day, so the robot brain learns from them.
RealApptronik's data-collection sites, unveiled with Apollo 2 on 30 Jun 2026: a ~90,000 sq ft facility in Austin plus Robot Parks inside Google DeepMind, Mercedes-Benz and GXO, where Apollo 2 fleets run a mix of teleoperated and autonomous work to produce training data for Gemini Robotics.
Ch. 15Robots as a service (RaaS)
ELI5You rent the robot by the month instead of buying it. The maker keeps fixing it, updating it and swapping parts, and you pay while it works.
RealA subscription contract that bundles the robot, its software, updates, maintenance and often an uptime promise into one monthly fee, so the customer books operating cost instead of capital. Reported Digit price as of Sep 2026: about US$8,500 a month plus a US$25,000 deployment fee. Shenzhen sales people usually say 租赁 (rental) or the English letters RaaS.
Ch. 15ROS 2
ELI5A free toolkit that lets a camera program, a map program and a motor program written by different people talk to each other.
RealRobot Operating System 2: open-source middleware and tools (nodes, topics, services, actions, Nav2, MoveIt 2, ros2_control) running over DDS. Current long-term release Lyrical Luth, 22 May 2026, supported to May 2031. Research standard, used in products with care. Chinese engineers usually just say "ROS".
Ch. 12Rotary actuator
ELI5An actuator that twists, turning one bone relative to the next.
RealA joint actuator whose output rotates: motor, reducer (harmonic, planetary or cycloidal), encoders and often a torque sensor; the reducer is about 36% of its cost.
Ch. 02RRT
ELI5Throw out random safe poses, grow a tree of them from the start, and stop when a branch reaches the goal.
RealRapidly exploring random tree: a sampling-based motion planner that grows a tree of collision-free configurations toward random samples; effective in high-dimensional joint spaces. RRT* adds asymptotic optimality.
Ch. 08RS-485
ELI5An old, cheap way to send data down a twisted pair of wires to several devices.
RealA differential serial signalling standard for multi-drop links over twisted pair, used by many low-cost and hobby servos and sensors. Slower and less deterministic than EtherCAT.
Ch. 06RTOS
ELI5A tiny operating system that promises to run each job on time, every time.
RealReal-time operating system with deterministic scheduling and bounded interrupt latency: FreeRTOS and Zephyr on motor and sensor MCUs, QNX and VxWorks where certification matters.
Ch. 06Run-to-charge ratio
ELI5How many minutes of work you get for each minute plugged in. Ten to one means a nine-minute charge buys ninety minutes of work.
RealOperating time divided by charging time over one cycle. Digit 5 claims 10:1 (90 min of work, 9 min of high-current DC charge), giving 20+ productive hours a day; Digit 4 was 2:1. NEO quotes 6 minutes of charge per hour of runtime, also about 10:1.
Ch. 15Runtime (续航)
ELI5How long the robot works on one charge.
RealOperating time per charge: pack energy × usable share ÷ average power. Humanoids 2 to 5 h as of Sep 2026 (Figure 03 5 h, NEO 4 h, H2 about 3 h, G1 about 2 h); wheeled tray robots about 8 to 12 h.
Ch. 06RV reducer
ELI5A heavy, super-strong gearbox made of a small planetary set feeding a wobbling-disc stage. It holds up the whole arm of a factory robot.
RealRotate-vector reducer: a planetary first stage drives crankshafts that wobble two cycloid discs against a pin ring. High ratio, stiffness and shock capacity; standard at the base, shoulder and elbow of industrial arms. Nabtesco holds about 60% of medium and large industrial robot RV supply (estimate).
Ch. 03Safety certification
ELI5A test lab's official stamp saying the robot meets a safety rulebook.
RealThird-party assessment that a product meets standards such as ISO 13482, ISO 10218 or UL 3300, issued by bodies like TÜV SÜD or SGS. It is type testing before sale, done once per model; Singapore has no periodic in-service inspection for service robots that the research found.
Ch. 12Safety integrity level
ELI5A grade from 1 to 4 for how much you can trust a safety feature to work.
RealSIL 1 to SIL 4 under IEC 61508: the required probability that a safety function performs on demand, with SIL 4 the most demanding. Machinery often uses the parallel ISO 13849 performance levels PL a to e.
Ch. 12Sample
ELI5One or a few parts a supplier makes so you can check them before ordering more.
RealPre-production parts from a supplier for fit, function and quality checks, often charged. 打样 (dǎyàng) is the verb, to make a sample.
Ch. 07SDK
ELI5The toolbox and instructions that let your programmers use a robot's command menu.
RealSoftware development kit: libraries, examples and documentation for programming a platform, such as unitree_sdk2. Makers tier SDK access by product version and partner status.
Ch. 12Secondary development
ELI5Writing your own app on top of someone else's robot.
RealBuilding custom applications on a maker's robot through its SDK or API. A standard question in Chinese sales meetings; access often requires a developer or EDU version, and custom code can void the warranty (Unitree excludes damage in developer mode).
Ch. 12Section 1260H list
ELI5A US Defense Department list of companies it says help China's military. Being on it scares off US customers and investors.
RealThe Pentagon's list of "Chinese military companies" under Section 1260H of the FY2021 NDAA. Unitree was added in Jun 2026; the industry report says briefly, so current status is contested. Listing restricts US defence procurement and chills buyers.
Ch. 18Sense think act
ELI5Look, decide, move, and repeat, very fast.
RealThe basic robot control cycle: sensors measure, a computer estimates state and chooses an action, actuators apply force; real robots nest these loops from about 30 Hz (perception) to 20 kHz (motor current).
Ch. 01Sensor
ELI5Any part that measures something and turns it into a number the computer can read: how far, how fast, how hot, how hard.
RealA transducer that converts a physical quantity (angle, acceleration, light, distance, force, sound) into an electrical signal sampled by the robot's electronics. Robots combine proprioceptive and exteroceptive sensors; sensors are about 10 to 25% of a humanoid's bill of materials (estimate).
Ch. 05Sensor fusion
ELI5Combining several sensors that each make different mistakes, so together they are right more often than any one alone.
RealCombining measurements from sensors with complementary failure modes (IMU with camera, lidar and foot contact) into one estimate, usually with a Kalman-family filter or a factor graph. Requires calibration and time synchronisation.
Ch. 05Series elastic actuator
ELI5A motor with a spring on purpose between it and the arm. The spring soaks up bumps and its stretch tells you the force.
RealSEA: an actuator with a compliant element between gearbox and load whose deflection, read by two encoders, measures force; gains shock tolerance and safety, loses bandwidth and precision (Pratt and Williamson, MIT, 1995).
Ch. 02Service level agreement
ELI5A written promise of how fast help arrives and how fast the robot gets fixed.
RealA contract term fixing response time, repair time, coverage hours and penalties. PUDU Care Standard promises a 2-hour response in the US and Canada; no Singapore distributor publishes an SLA as of Sep 2026.
Ch. 13Service robot
ELI5Any robot that does a job outside a factory line: carrying plates, washing floors, delivering parcels, guarding a car park. The opposite of a caged factory arm.
RealIFR definition: a robot that performs useful tasks for humans or equipment excluding industrial automation. Professional service robots (about 200,000 sold in 2024) split into logistics, hospitality, cleaning, agriculture, medical and security classes.
Ch. 17Servicing
ELI5Routine care, like a car's regular service: clean, check, replace worn bits.
RealScheduled upkeep that prevents failures: cleaning sensors, clearing wheels, changing brushes and squeegees, checking batteries and fasteners. Pudu tells owners to clean sensors and wheels at least weekly.
Ch. 13Servo motor
ELI5A motor that knows where its shaft is and corrects itself until it gets there.
RealA motor sold with an encoder and closed-loop drive; in industry a PMSM with a 17 to 25 bit absolute encoder and FOC drive at US$500 to 3,000 per axis. Hobby 'servos' are a different, far cruder product.
Ch. 02Setpoint
ELI5The number you want: 90 degrees at the elbow, 1.2 m/s forward.
RealThe target value a controller tries to make the measured output match; it can change every tick when it comes from a trajectory.
Ch. 08Sheet metal
ELI5Cutting flat shapes out of thin metal sheets and folding them into boxes and brackets, like metal origami.
RealLaser or punch cutting plus press-brake bending (no tooling, ±0.1 to 0.4 mm) at low volume; progressive dies (US$20k to 150k in China) at high volume. Used for enclosures, battery trays, chassis and brackets.
Ch. 07Shipments
ELI5How many robots actually left the factory, which is often fewer than the orders a company talks about.
RealUnits delivered in a period. About 13,000 humanoids in 2025 by Omdia's count (up to 18,000 by others); Unitree over 5,500, AgiBot 5,168, UBTech 1,079, Figure, Agility and Tesla about 150 each.
Ch. 18Sim-to-real
ELI5Getting a skill learned in the video game to work on the real robot.
RealTransfer of a policy trained in simulation to hardware; the gap is mostly dynamics (friction, compliance, motor behaviour, delay). Closed for locomotion with domain randomisation and distillation; still wide for dexterous manipulation.
Ch. 09Simulation
ELI5A video game version of the robot and the world where it can practise and fall for free.
RealPhysics simulation of the robot, sensors and environment (Isaac Sim and Isaac Lab, MuJoCo, Newton, Genesis) used for training, testing and synthetic data. Strong on rigid bodies; weak on friction, contact stiffness, cables, thermals and latency.
Ch. 09Simulation data
ELI5Practice recordings made inside a video-game version of the world.
RealTrajectories generated in physics simulators such as Isaac Sim, MuJoCo or Newton, often with domain randomisation. Cheap and parallel, weaker on contact and friction; a rule of thumb puts about 8 simulated samples equal to 1 teleoperated sample.
Ch. 11Simulation platform
ELI5A physics video game where robots practise and get tested before they touch the real world.
RealSoftware that models robot bodies, sensors and physics for training, testing and synthetic data. Isaac Sim 6.0 and Isaac Lab 3.0 (NVIDIA), MuJoCo (DeepMind), Newton (Linux Foundation), Genesis. Vision simulates well; contact and friction do not.
Ch. 12Singularity
ELI5A pose, like a fully straight arm, where the hand can't move in some direction and trying makes the joints jerk.
RealA configuration where the Jacobian loses rank: the end effector loses a direction of motion and joint speeds needed for nearby motions tend to infinity. Handled with damped least squares and by planning away from singular poses.
Ch. 08Six-axis force/torque sensor
ELI5A metal ring in the robot's wrist that feels how hard and which way the hand is being pushed or twisted, like your wrist feeling a heavy bag.
RealA strain-gauge flexure that measures three forces and three torques at a wrist or ankle. China's humanoid makers bought about 12,300 in 2025, 92.8% domestic; wrist units CNY 15,000 to 38,000 (estimate).
Ch. 04SLAM
ELI5Drawing a map of a new building while also working out where you are on it, and fixing the map when you recognise a spot you have seen before.
RealSimultaneous localization and mapping: a front end (odometry, scan matching, feature tracking, loop-closure proposals) plus a back end that optimises a pose graph (g2o, Ceres, GTSAM). Lidar SLAM drifts about 0.1 to 0.5% of distance and visual-inertial odometry about 0.3 to 1% between loop closures (estimates).
Ch. 05Slip ring
ELI5A spinning connector: little brushes rub on metal rings so power and signals can cross a joint that keeps turning round and round.
RealA rotary electrical joint of brushes on rings carrying power and data across continuous rotation. It wears and adds electrical noise, so it is a maintenance item.
Ch. 06Small batch
ELI5Building tens or hundreds of units to prove the factory can make them before going big.
RealPilot production between prototype and mass production, often on soft tooling or machined parts, priced higher per unit.
Ch. 07Smile curve
ELI5Draw profit along a product's life from parts to customer and it looks like a smile: high at both ends, low in the middle where things are assembled.
RealThe pattern that value added is highest in R&D and key components and in brand, distribution and service, and lowest in assembly. In robots: chips about 70%+ gross, reducers 35 to 45%, contract assembly 2 to 3% net, Otis-style service 25% operating margin.
Ch. 18SPAC merger
ELI5A shortcut to the stock market: a shell company that already has listed shares merges with the startup, and the startup takes over the listing.
RealA merger with a special-purpose acquisition company, used instead of an IPO. Agility Robotics agreed a SPAC merger with Churchill Capital Corp XI on 24 Jun 2026 at US$2.5bn pre-money, raising over US$620m under the ticker AGLT, the first public-market path for a western humanoid maker.
Ch. 15Spare parts
ELI5Replacement pieces kept ready so a broken robot can be fixed quickly.
RealReplacement components and modules held for repair. The chokepoint for service robots: brand-specific, maker-supplied, lead times unpublished, and replaced warranty parts must be returned to Pudu and Gausium.
Ch. 13Speed and separation monitoring
ELI5The closer you walk to the robot, the slower it goes, until it stops.
RealA collaborative safety function that measures the distance to people with safety scanners or cameras and limits robot speed so it can always stop before contact; zones scale with stopping distance.
Ch. 12Stance phase
ELI5The part of a step when the foot is on the ground holding you up.
RealThe portion of the gait cycle during which a leg is in ground contact and carries load; in walking the two stance phases overlap in double support.
Ch. 09STAR Market
ELI5Shanghai's stock market for tech companies, where Unitree listed.
RealThe Shanghai Stock Exchange Science and Technology Innovation Board, opened 2019 for tech listings. Unitree listed there on 19 Aug 2026 at ¥150.80, with retail oversubscription above 8,000x, after listing-committee approval in about 73 days.
Ch. 18State capital
ELI5Money from government-owned funds and companies invested in startups.
RealInvestment by state-owned funds, banks and enterprises. Galbot's investors include units of Sinopec, CITIC, Bank of China and SAIC; an NDRC-backed fund targets about ¥1 trillion over 20 years (unverified).
Ch. 18Stereo camera
ELI5Two cameras side by side, like your two eyes. The closer something is, the more it shifts between the two pictures, and that shift gives the distance.
RealA pair of calibrated cameras a baseline B apart; depth z = f × B / d from disparity d. Depth error grows with the square of distance. Walker S2 and Unitree H2 use binocular stereo instead of lidar.
Ch. 05Structured light
ELI5Shine a known pattern of dots or stripes onto things and watch how it bends over their shape.
RealActive depth sensing that projects a known infrared pattern and triangulates its distortion. Precise at short range indoors; washes out in sunlight. Used in Face ID and the original Kinect.
Ch. 05Success rate
ELI5Out of every 100 tries, how many worked.
RealThe fraction of trials that complete the task. Meaningless without the task, the number of trials, speed relative to a human, interventions per hour and who chose the test. Company figures range from 99.4% (DYNA-1, one task) to 56% (Helix 2.5, unseen homes).
Ch. 10Suction cup
ELI5A rubber cup that sticks to flat things by sucking the air out, like the hook on a bathroom tile.
RealA vacuum end effector that holds objects by pressure difference over a sealed pad; fast and simple on boxes and flat sheets, weak on porous or curved surfaces. Boston Dynamics' Stretch unloads about 500 parcels an hour with one.
Ch. 04Sun gear
ELI5The small gear in the middle of a planetary set that the motor turns.
RealThe central external gear of a planetary set, usually the input.
Ch. 03Support polygon
ELI5Stretch a rubber band around every part of the robot touching the floor. The shape inside is where its weight can safely press.
RealThe convex hull of all ground contact points. One foot in single support; both feet and the area between in double support. Static stability requires the CoM projection inside it; dynamic stability requires the ZMP inside it.
Ch. 09Swing phase
ELI5The part of a step when the foot is in the air moving forward.
RealThe portion of the gait cycle during which a leg is off the ground and repositions for the next contact; foot clearance and landing timing decide stumbles.
Ch. 09Synthetic data
ELI5Training examples a computer made up, instead of recording them in the real world.
RealData generated by simulation or generative world models. NVIDIA's GR00T-Dreams made 780,000 trajectories in 11 hours and improved GR00T N1.5 by 40% over real data alone (Jun 2025). Force and contact do not synthesise well.
Ch. 11System integrator
ELI5The firm that takes a robot out of the box and makes it work in your building: maps, lift access, Wi-Fi, the door that never opens.
RealCompany that designs, installs and commissions robot systems for an end customer, combining robots, software, infrastructure (lifts, doors, networks) and training. Weston Robot in Singapore describes itself this way.
Ch. 17Tactile sensor
ELI5A patch of tiny pressure dots on a fingertip that tells the robot where it's touching something and how hard.
RealAn array of taxels (piezoresistive, capacitive, magnetic Hall-effect or camera-based gel) that reports contact location, normal force and sometimes shear. Arrays cost about US$0.4 to 1.2 per mm² (estimate); PaXini fingertips start near US$49.
Ch. 04Tariff
ELI5A tax a country charges on goods coming in from abroad.
RealImport duty. A Chinese industrial robot entering the US faces about 40%: 2.5% MFN, 25% Section 301 List 1 and 12.5% new Section 301 from 24 Jul 2026 (estimate); a Section 232 robotics action was still pending in Sep 2026.
Ch. 18Teacher-student distillation
ELI5A teacher who can see everything in the video game shows a student who can only see what the real robot sees, until the student can do it alone.
RealTrain a teacher policy with privileged simulator state (terrain heights, friction, contact forces), then train a student policy with only onboard observations and history to imitate it. The standard route to blind and perceptive locomotion that transfers to hardware.
Ch. 09Teleoperation
ELI5A person drives the robot from a distance, like a puppet, often wearing a VR headset.
RealRemote control of a robot by a human operator through VR, a leader arm or a gamepad; used for demonstrations, remote assistance and collecting training data at about US$36 to 40 per operator hour.
Ch. 01Teleoperation rig
ELI5The controls a person uses to drive a robot from a distance: a headset, a copy of the arm, or a suit.
RealThe hardware that maps a human operator's motion to a robot: leader-follower arms (ALOHA, GELLO), VR headsets with hand tracking, exoskeletons or motion capture suits, plus the recording stack. Rig cost dominates teleop data prices of US$50 to 200 per hour on a target robot (2026 estimate).
Ch. 11Temperature rise
ELI5How much hotter the motor gets than the room while it works. Too much and it shuts itself off.
RealThe increase of winding temperature above ambient under load, set by copper loss and cooling; it fixes the continuous torque rating and is a standard test item in Chinese actuator spec sheets.
Ch. 02Tendon drive
ELI5Cables that pull on joints like the tendons in your arm pull your fingers, so the motors can sit far away.
RealActuation through cables routed over pulleys from remote motors, as in 1X NEO and tendon-driven hands. Light, quiet and backdrivable; cables stretch, fray and need tensioning. Engineers also say 绳驱.
Ch. 03Tendon-driven hand
ELI5A robot hand whose motors sit in the forearm and pull cables to bend the fingers, like the tendons in your arm.
RealA dexterous hand actuated by cables routed through the wrist from forearm motors, as in 1X NEO and reportedly Optimus Gen 3 (about 25 forearm actuators per arm). Slim, light fingers; cable stretch and tensioning add maintenance.
Ch. 04Thermal management
ELI5Keeping the robot's motors, computer and battery from overheating: fins, fans or water cooling.
RealDesign of heat paths from sources (motor copper, drivers, compute, cells) to ambient: conduction into structure, forced air, liquid cold plates. Sets continuous torque and sustained compute; overheated joints derate.
Ch. 06Third-party maintenance
ELI5An independent company fixing machines made by someone else, usually cheaper than the maker.
RealIndependent servicing of other makers' equipment. IT hardware TPM is 50 to 70% cheaper than the maker but under 2% of spend (2019); imaging independents reached 50% of US service spend (2022); elevator independents hold about 50% of service units.
Ch. 13Third-party repair
ELI5An independent garage fixing your robot instead of the company that made it or its official dealer.
RealMaintenance and repair by a firm other than the maker or its authorised partner. For robots it can void the warranty (Pudu voids cover for maintenance under unofficial guidance) and usually lacks the maker's diagnostic tools. Independents hold about 50% of elevator service units and reached 50% of US imaging service spend in 2022.
Ch. 15Time of flight (ToF)
ELI5Flash light and time how long it takes to bounce back. Light is so fast the stopwatch has to count in billionths of a second.
RealRange measurement from the round-trip time of light, distance = c × t / 2. Indirect ToF measures phase shift of modulated light (about 1 cm indoors to about 5 m, fooled by multipath and sunlight); direct ToF times photons with SPAD detectors and underlies lidar.
Ch. 05Time scale
ELI5How long one step of a job takes. A magnet's push lasts millionths of a second; retraining the robot's brain takes weeks.
RealThe characteristic period of a process, such as one current-loop cycle (25 to 100 µs), one policy step (5 to 20 ms) or one retrain and OTA cycle (days to weeks). A robot spans about twelve orders of magnitude of time scales, which is why its software is layered and why the layers are drawn on a logarithmic axis.
Ch. 14Timing belt
ELI5A toothed rubber belt, like a bike chain made of rubber, that carries turning from a motor to a joint a little way off.
RealA toothed belt with tensile cords that transmits rotation without slip between pulleys; lets designers move motor mass up a limb, adds some compliance.
Ch. 03Tolerance
ELI5How far a part is allowed to be off its drawing size and still pass. Tighter costs more, a lot more.
RealThe permitted variation of a dimension. Machined metal: ±0.1 mm cheap, ±0.025 mm +30 to 100%, ±0.01 mm 2 to 5x, ±0.0025 mm 5 to 20x (estimate). Suppliers are judged by Cpk at a tolerance; 1.33 is about 63 defects per million.
Ch. 07Tooling
ELI5The custom steel moulds and dies a factory has to make before it can stamp out your part. Expensive once, then every part is cheap.
RealDesign-specific moulds, dies, jigs and fixtures, paid up front and usable for one part design only. A single-cavity Chinese injection mould is about US$9,000; die-casting dies US$20k to 300k+. A product with 10 to 20 custom parts needs about US$100k to 500k of tooling (materials primer, estimate).
Ch. 07Topic
ELI5A named noticeboard. One program pins updates on it, and any program that wants them reads it.
RealIn ROS 2, a named, typed channel for one-to-many publish and subscribe messages, such as /camera/image at 30 frames per second. Publishers and subscribers do not know each other, which is what lets you add a logger without touching the camera driver.
Ch. 12TOPS
ELI5Trillions of operations per second: a headline number for how fast an AI chip is. Like a car's top speed, it tells you less than the ad suggests.
RealTera operations per second, the peak arithmetic rate of an AI accelerator at a stated number format (INT8, FP8, FP4). Figures at different formats are not comparable; delivered model latency at a given power matters more.
Ch. 06Torque constant
ELI5How much twist the motor makes for each amp of electricity.
RealKt, in N·m per amp: τ = Kt × I. In SI units it equals the back-EMF constant Ke; hobby Kv (rpm per volt) is its inverse in other units.
Ch. 02Torque density
ELI5How much twist you get per kilogram of motor. Higher means lighter legs for the same strength.
RealContinuous or peak torque divided by actuator mass (N·m/kg); the key figure of merit for legged robots, rarely published by makers.
Ch. 02Torque sensor
ELI5A tiny bathroom scale for twisting, built into a joint so the robot knows how hard it is pushing.
RealA metal flexure with strain gauges that measures twisting load in a joint; about 30% of a rotary actuator's cost. Six-axis versions at wrists and ankles measure three forces and three torques.
Ch. 02Torsional stiffness
ELI5How much a joint twists like a spring when you load it. Stiffer means less wobble when the arm holds something heavy.
RealOutput torque per unit of angular deflection with the input locked, in N·m per arc-minute. Low stiffness adds wobble and limits control bandwidth.
Ch. 03Training ground
ELI5A government-built hall with fake kitchens and factories where robots practise and get recorded.
RealA Chinese state or state-backed data collection centre with staged scenarios and many robots teleoperated by staff. Beijing Shijingshan's centre (Oct 2025) has 10,000+ m², about 200 instructors and 100 humanoids; Shanghai's Kylin Training Ground plans 1,000 robots by 2027.
Ch. 11Trajectory planning
ELI5Deciding how fast to move along the route, so the motors can keep up and the arm doesn't shake.
RealTime parametrisation of a path into positions, velocities and accelerations within joint limits, typically with S-curve profiles and input shaping to avoid exciting structural resonances.
Ch. 08UBTech
ELI5The Shenzhen company whose Walker S2 works in car factories and changes its own battery, and whose unit counts are audited because it is listed in Hong Kong.
RealUBTech Robotics 优必选, Shenzhen (Nanshan), HKEX 9880 since Dec 2023. FY2025 revenue about ¥2.0 billion with 1,079 full-size humanoids sold; 1H 2026 revenue ¥1.27 billion, 921 full-size units, gross margin 44.7%. Flagship Walker S2 (52 DoF, 15 kg payload, autonomous battery swap). Customers include BYD, Zeekr, FAW-VW, Foxconn, SF Express.
Ch. 16Ultrasonic sensor
ELI5A tiny speaker and microphone that squeak too high for you to hear and listen for the echo, like a car's parking sensor.
RealA short-range acoustic time-of-flight sensor. It detects glass and dark objects that lidar misses, with a wide beam and poor angular resolution; common around the base of service robots.
Ch. 05UMI gripper
ELI5A handheld robot-style gripper with a camera, so a person can record demos without any robot.
RealUniversal Manipulation Interface: a handheld parallel gripper with a wrist-mounted fisheye camera that records gripper pose and video while a human performs the task. Rig cost in the low hundreds of dollars; TRI used 32 h of UMI data in its Large Behavior Models.
Ch. 11UN38.3
ELI5The set of shake, heat, crush and short-circuit tests every lithium battery must pass before anyone is allowed to ship it.
RealSection 38.3 of the UN Manual of Tests and Criteria: transport tests for lithium cells and batteries. Carriers require the test summary; Figure's Figure 03 pack is UN38.3 certified.
Ch. 06Underactuated
ELI5A hand or finger with fewer motors than joints. The joints are tied together, so one motor bends several of them and the finger wraps round whatever it touches.
RealA mechanism with fewer actuators than degrees of freedom; passive joints follow through linkages, tendons or springs. Cheaper and more robust, with shape-adaptive grasps and fewer in-hand skills.
Ch. 04Unitree
ELI5The Hangzhou company that sells most of the world's robot dogs and about a third of its humanoids, at prices a school can afford.
RealUnitree Robotics 宇树科技, Hangzhou, founded 2016 by Wang Xingxing. Listed on the Shanghai STAR Market 19 Aug 2026 (IPO at ¥150.80, day-one close ¥845). 2025 revenue ¥1.70 billion, gross margin about 60%, more than 5,500 humanoids sold in 2025. Makes its own quasi-direct-drive joints, drivers and BMS. Products: G1, H2, R1 humanoids, Go2, A2, B2 quadrupeds, Dex hands, L2 lidar.
Ch. 16Upstream
ELI5The part suppliers: magnets, motors, gears, sensors, chips and batteries.
RealMaterials and core components in the robot industry chain: rare earths, magnets, motors, reducers, roller screws, sensors, chips, batteries. China holds about 90% of rare earth refining but about 35% of motors and 30% of power electronics.
Ch. 18Uptime
ELI5The measured share of time the robot was working, the number a venue sees on its report.
RealObserved operating time as a share of scheduled time, the after-the-fact counterpart of availability. Formic reported 99%+ over 100,000 production hours (Jun 2024); Weston Robot claims 99.4% fleet uptime.
Ch. 13Valuation
ELI5What investors say a whole company is worth when they buy a piece of it.
RealPre- or post-money price of a company in a funding round or on a market. Figure US$39bn (Sep 2025), Skild over US$14bn (Jan 2026), Unitree about US$9bn at its IPO price and about US$51bn at its first-day close (19 Aug 2026).
Ch. 18VDA 5050
ELI5A common radio language so one control room can order any brand of warehouse robot around.
RealA VDA and VDMA interface between a master controller and AGVs or AMRs from any maker, using MQTT and JSON (orders, state, instant actions). Version 3.0.0, Mar 2026, adds freely navigating robots, shared planned paths, zones and CRITICAL and URGENT error levels.
Ch. 12VLA model (vision-language-action)
ELI5A robot brain that looks through cameras, reads an instruction and writes out how each joint should move next.
RealA model that maps camera images, a language instruction and robot state to motor actions. Built from a pretrained vision-language backbone plus an action head (tokens, diffusion or flow matching) that outputs action chunks at 50 to 200 Hz. Examples: π0 (3.3B), GR00T N1.6 (3B), Helix, Gemini Robotics 2.
Ch. 10Warehouse robot
ELI5Robots that move stock around a warehouse so people do not have to walk: low units that carry whole shelves, carts that follow pickers, and cranes that dig bins out of a grid.
RealLogistics robots for intralogistics: goods-to-person shelf carriers (Kiva lineage, Geek+, HAI, Quicktron), collaborative picking carts (Locus), tote and pallet AMRs (Pudu T300, MP2000) and cube storage systems (AutoStore). IFR counted 102,900 transport and logistics robots sold in 2024.
Ch. 17Warranty
ELI5The maker's promise to fix manufacturing faults for free, as long as you did not break it yourself.
RealA contractual promise to repair or replace defective products for a period. Robot warranties exclude the common damage: Unitree excludes falls even on level ground and developer-mode damage; Pudu and Gausium exclude collisions, liquids and debris.
Ch. 13Warranty period
ELI5How long the free-fix promise lasts, usually one year.
RealThe time warranty cover runs, usually from the date of receipt. Gausium: 1 year; Malaysia's Pudu dealer: 1 year; Pudu: varies by country; Unitree's terms page gives no length. Also said 质保期 (zhìbǎo qī).
Ch. 13Wave generator
ELI5The oval spinning cam in the middle of a harmonic drive. The motor turns it and it pushes the cup's teeth into the ring at two spots.
RealThe elliptical cam plus thin-section flexible ball bearing that forms the input of a strain-wave gear and deforms the flexspline into an ellipse.
Ch. 03Wear parts
ELI5Pieces that wear out with normal use and get replaced on a schedule, like brake pads.
RealConsumable components with predictable life: squeegees, brushes, casters, wheels, filters. Cheap and generic enough to stock locally, unlike modules such as lidar or mainboards.
Ch. 13Wheel-legged
ELI5Legs with wheels on the ends: roll on flat floors, step up when there's a kerb.
RealA locomotion design combining legs with driven wheels at the feet, getting wheel efficiency on flat ground and leg mobility over steps. Examples: Unitree Go2-W and B2-W, Deep Robotics Lynx, LimX TRON 2 in wheel-leg mode.
Ch. 09Wheeled
ELI5Moves on wheels. Cheap, efficient and fast on flat floors, stopped by a step.
RealA locomotion type using powered wheels, usually differential drive (two driven wheels plus casters) on service robots; wheeled humanoids put an upper body on such a base.
Ch. 01White label
ELI5A finished product made by someone else, sold with your brand on it.
RealRebadging a maker's standard product under the seller's brand, with little or no design change. Common in service robots and in after-sales work done under a distributor's name.
Ch. 07Whole-body control
ELI5A ranked to-do list for the whole body (don't fall, keep feet planted, hold the box, look natural) solved a thousand times a second.
RealControl that computes all joint torques and contact forces together from prioritised tasks, classically as a quadratic program at 500 Hz to 1 kHz. Increasingly a learned network, for example Figure's Helix 02 S0 (10M parameters, 1 kHz, trained in simulation).
Ch. 08Wireless charging
ELI5The robot stands on a mat and power flows up through coils in its feet, so nobody has to plug it in.
RealInductive power transfer through coils in the robot's soles to a floor pad. Figure 03 charges at 2 kW this way, enough to keep a 2.3 kWh pack topped up if the robot steps onto a pad during a shift.
Ch. 15Wiring harness
ELI5All the robot's cables bundled together and routed through its body, like its nerves and blood vessels.
RealThe assembled set of power, signal and bus cables with connectors, routed through joints and links. In humanoids the harness flexes at every joint; cable fatigue and loose connectors cause intermittent faults.
Ch. 06Workspace
ELI5Every spot the robot's hand can reach without moving its base.
RealThe set of positions (and orientations) the end effector can reach, fixed by link lengths and joint limits; a two-link planar arm reaches a ring between the difference and the sum of its link lengths.
Ch. 01World model
ELI5A video game engine the AI learned by watching, so it can imagine what happens if the robot pushes the cup.
RealA generative model that predicts future observations (video frames or latent states) conditioned on actions. Used to synthesise training data (GR00T-Dreams), evaluate policies before real trials (1X World Model) and plan (V-JEPA 2). Weak on contact and force.
Ch. 10Wrist
ELI5The joint between the forearm and the hand. On robots it's crowded with motors, wires and a force sensor.
RealThe 2 to 3 DoF joint group between forearm and hand, often carrying the six-axis force/torque sensor. Figure named the forearm and wrist as Figure 02's top hardware failure point.
Ch. 04X-Humanoid (Tiangong)
ELI5Beijing's state-backed humanoid centre, whose Tiangong robots win the running events at China's robot games.
RealBeijing Humanoid Robot Innovation Center 北京人形机器人创新中心, brand X-Humanoid, robot family Tiangong 天工. Tiangong Ultra won the first humanoid half marathon (19 Apr 2025); its teams took the 400 m, 1,500 m, long jump and hurdles golds at the 2026 World Humanoid Robot Games.
Ch. 16Xiaomi
ELI5The phone and car maker that showed a humanoid, CyberOne, in 2022 and has not put one on sale since.
RealXiaomi 小米, Beijing. CyberOne humanoid shown Aug 2022 (about 1.77 m, 52 kg, 21 DoF, from memory). No humanoid product on sale found as of Sep 2026.
Ch. 16Xpeng
ELI5The Guangzhou electric-car maker whose IRON humanoid walks so much like a person that they cut its leg open on stage to prove nobody was inside.
RealXpeng Motors 小鹏, Guangzhou (Tianhe). IRON humanoid: 1.78 m, 70 kg, humanoid spine, flexible lattice skin, curved face display, 22-DoF hands, three in-house Turing chips (2,250 TOPS), semi-solid-state battery. Production line switched on 8 Sep 2026; mass production targeted for end 2026, own stores first, commercial sales 2027.
Ch. 16Yield
ELI5Out of every 100 robots you build, how many pass the checks first time.
RealThe share of units passing inspection. First-pass (rolled throughput) yield is the product of station yields: three stations at 95% give about 86%. Cosmetic anodised parts historically run 60 to 90% first-pass (estimate). Humanoid makers do not publish yields.
Ch. 07Zero moment point
ELI5The spot on the floor where the robot's weight and motion together press down. Keep it under a foot and you don't tip.
RealZMP: the point on the ground where the horizontal components of the net moment from gravity and inertial forces vanish; equivalently the centre of pressure under the feet. Must stay inside the support polygon for the feet to stay flat. Basis of classical humanoid walking with ZMP preview control.
Ch. 09