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Robotics, from the joint up
How humanoids and service robots work, who builds them and what the parts cost, explained from the joint up with original drawings and sourced numbers.
- 18 chapters and a glossary
- every term with ELI5 and real definition
- Chinese names for the key terms
- every drawing original · Sep 2026
The whole robot on one screen
Three layers. The mind decides, the body senses and moves, and a supply chain that runs from magnet mines to after-sales desks makes both possible. Every chapter zooms into one box on this drawing.
The reading path
Each chapter takes 10 to 20 minutes and ends with the terms it introduces. Chapters you mark done get a tick in the contents.
The body
7 chapters- 01The whole robotRobot types, degrees of freedom, links and joints, and the sense, think, act loop.
- 02Motors and jointsHow a joint module works: motor, driver, encoder, torque sensor and brake.
- 03Gears and screwsHarmonic drives, planetary and cycloidal reducers, roller screws, tendons and why they decide cost.
- 04Hands and touchGrippers, dexterous hands, tendons and tactile skin: the hardest hardware problem.
- 05Sensors and perceptionEncoders, IMUs, force sensors, cameras, depth, LiDAR and how robots build a picture of the world.
- 06Compute, wiring and powerOnboard computers, real-time buses, batteries, heat and the wiring harness.
- 07Materials, manufacturing and costWhat robots are made of, how they are made, the bill of materials and the cost-down curve.
The mind
7 chapters- 08Control, from current loop to plannerThe layered control stack: PID, impedance control, kinematics, whole-body control and MPC.
- 09How robots walk and balanceGait, balance, reinforcement learning in simulation and sim-to-real transfer.
- 10Robot foundation modelsVision-language-action models, world models and the race to a general robot brain.
- 11The data engineTeleoperation, human video, simulation and fleet data: the bottleneck of robotics.
- 12Software, fleets and safetyROS 2, simulation, fleet management, updates, cybersecurity and safety standards.
- 13How robots fail and get fixedFailure modes, uptime maths, service models, spare parts and who owns failure data.
- 14One second inside a robotFollow one grasp from camera to fingertip and see every part of the machine work together.
The atlas
3 chapters- 15US and European robotsFigure, Apptronik, 1X, Tesla, Agility, Boston Dynamics, Neura and Dyna, drawn and explained.
- 16Chinese robotsUnitree, UBTech, AgiBot, Fourier, Xpeng, Galbot and more, drawn and explained.
- 17Robots already at workPudu, Keenon, Gausium, cleaning, delivery, warehouse and industrial robots deployed today, with a Southeast Asia focus.
The industry
1 chapterAppendix
1 pageHow to use this primer
Every hard idea is explained twice, side by side. The left column is exact. The right column is what you would say to a sharp fifteen-year-old. Read whichever lands first, then the other.
Real
A joint module integrates a frameless brushless motor, a reducer such as a harmonic drive, one or two encoders and a motor driver in one housing.
ELI5
A robot joint is one can you bolt in. Inside: a motor that spins fast, a gear that makes it slow and strong, a dial that knows the angle, and a little computer that runs the motor.
Dotted words are terms. Hover, tap or focus one and a card shows the ELI5, the real definition and the Chinese. Every term lives in the glossary, searchable in English, 中文 or pinyin.
Numbers carry chips. verified Sep 2026 means a primary source was checked this month. estimate is a reasoned figure. contested means credible sources disagree and the text shows both. unverified means no primary source confirmed it yet.
Use the contents to jump around and the button at the end of each chapter to mark it done. Animations stop when you scroll past them and switch off under reduced motion. Nothing here needs an account, and nothing leaves your browser.