Part 1: Start hereChapter 3 of 155
The kinds of robots
Beginner3 min2 review cards
"Robot" covers everything from a vacuum cleaner to a surgical system to a Mars rover. Sorting them by how they move and where they work shows why they look so different, and which hard problem each one is built around.
What you will learn
- Sort robots by how they move and what they do
- Match a robot type to the task it suits
- Know which chapters of this course cover each kind
Sorting by how they move#
| Kind | Moves by | Strengths | The hard part |
|---|---|---|---|
| Fixed arm | Joints bolted to a base | Speed, precision, strength | Handling variety; safety near people |
| Wheeled mobile robot | Wheels or tracks | Efficient on flat ground, simple | Rough terrain, stairs |
| Legged robot | Legs (two, four or more) | Reaches places wheels cannot | Balance, energy use |
| Humanoid | Two legs, two arms | Fits spaces and tools made for people | Everything at once: balance, hands, reliability |
| Aerial robot (drone) | Rotors or wings | Fast access from above | Battery life, wind, regulation |
| Underwater robot | Thrusters | Reaches the deep sea | Communication, pressure, navigation |
| Space robot | Wheels, arms, thrusters | Works where people cannot | Delay, radiation, no repairs |
| Soft robot | Flexible bodies, air or fluid | Gentle, adaptable | Control and modelling |
| Micro and swarm | Tiny bodies, many of them | Scale, redundancy | Power, sensing, coordination |
A mobile manipulator combines a mobile base with one or more arms, and is the shape most service robots take. It inherits the problems of both halves.
Sorting by where they work#
- Factories and warehouses. The largest market by far. Industrial arms weld, paint and assemble. Mobile robots carry shelves and totes. Chapters 93 and 94.
- Roads, air and water. Self-driving cars, delivery drones and underwater vehicles. Chapters 95, 96 and 103.
- Hospitals. Surgical systems, rehabilitation and disinfection robots, prosthetics. Chapters 100 and 106.
- Farms, mines and building sites. Robots in rough, unstructured outdoor settings. Chapters 101 and 102.
- Homes and shops. Vacuums, lawn mowers, companions and, in development, general household helpers. Chapter 99.
- Labs and classrooms. Educational and hobby kits, and competitions. Chapter 107.
Sorting by autonomy#
How much does the robot decide for itself? A useful scale, from least to most:
- Teleoperated. A person drives every motion (a bomb-disposal robot, a surgical console).
- Programmed. It repeats a fixed routine (a classic welding arm).
- Supervised autonomy. It does a task alone and asks a person when it is unsure.
- Conditional autonomy. It runs by itself within a defined domain, such as a robotaxi in a mapped city.
- General autonomy. It handles open-ended tasks in open-ended places. Nobody has this yet.
Most commercial robots sit at levels 2 to 4, and the progress of physical AI is mostly about moving things up that scale without losing reliability.
The shape of the market today#
Factory arms are the established industry and their numbers keep growing. Warehouse robots grew quickly through the 2010s and 2020s. Robotaxis operate commercially in a small but growing set of cities. Legged and humanoid robots are the newest and most hyped: real machines exist and are being piloted, but how fast they will become everyday products is genuinely uncertain, and the later chapter 98 looks at the claims critically.
Check yourself
Answer in your head first, then open the answer and say how it went. That is what schedules your review.
Why is a humanoid considered the hardest common robot shape?
What is a mobile manipulator?
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About this chapter
On the learning pathRobotics and physical AI
Checked against python 3.14, numpy 2.5, scipy 1.18, mujoco 3.17, gymnasium 1.4, opencv 5.0 on 2026-10-24. Robotics and physical AI move fast, and products, prices and standards change often. Where a manufacturer's or standards body's current documentation disagrees with this page, trust the documentation, and tell us on the corrections page.