What is a robot?
What you’ll learn
- A clear definition of a robot you can use for the rest of this course
- The difference between a robot, a machine and a computer
- Why robots are built from three kinds of parts
A working definition
People argue about the exact meaning of “robot”, but engineers mostly agree on this:
A robot is a machine that can sense its surroundings, decide what to do, and act on the world by itself.
All three parts matter:
| Part | Question it answers | Example |
|---|---|---|
| Sense | What is happening around me? | A distance sensor notices a wall 20 cm ahead |
| Think | What should I do about it? | A small computer decides “turn left” |
| Act | How do I change the world? | Motors spin the wheels to turn |
Take away any one of these and you have something else:
- A toaster acts (heats bread) but doesn’t sense how brown the toast is, so it’s just a machine.
- A laptop thinks but has no motors to move anything, so it’s a computer.
- A remote-controlled car moves, but a human does the sensing and deciding, so it’s a remote-controlled machine, not an autonomous robot.
Robots are everywhere
- Factories: robot arms weld cars and pack boxes.
- Homes: robot vacuums and lawn mowers.
- Hospitals: surgical robots help doctors make tiny, precise movements.
- Space: Mars rovers drive themselves because radio signals take minutes to reach Earth.
- Warehouses: fleets of small robots carry shelves to human packers.
The parts of every robot
Every robot you’ll build in this course has the same building blocks:
- Sensors, the robot’s senses: buttons, light sensors, distance sensors, cameras.
- A controller, the robot’s brain: usually a small computer called a microcontroller (for example an Arduino board or a LEGO hub).
- Actuators, the robot’s muscles: motors, servos, speakers, lights.
- Power, its energy: batteries or a power supply.
- Structure, its body: a chassis made from LEGO, plastic, wood or metal.
- Code, its instructions: the program that tells the controller how to turn sensor readings into actions.
You’ll learn each of these in its own section of the library.
Example: a robot vacuum, part by part
| Part | In a robot vacuum |
|---|---|
| Sensors | Bump switches on the front, downward infrared “cliff” sensors so it doesn’t fall down stairs, wheel encoders that count wheel turns |
| Controller | A microcontroller running the cleaning program |
| Actuators | Two wheel motors, a brush motor, a suction fan |
| Power | A rechargeable lithium-ion battery and a charging dock |
| Structure | A round, low plastic shell that slides under furniture |
| Code | Rules like “if a cliff sensor sees no floor, stop and turn away” |
Example: a Mars rover, part by part
| Part | On a Mars rover |
|---|---|
| Sensors | Navigation cameras, hazard cameras near the wheels, a motion sensor (IMU) |
| Controller | Radiation-hardened onboard computers |
| Actuators | Six wheel motors, steering motors, a robotic arm with tools |
| Power | A nuclear power source or solar panels, plus batteries |
| Structure | A rocker-bogie suspension that climbs over rocks |
| Code | Self-driving software that picks a safe path, because commands from Earth take minutes to arrive |
The two machines look nothing alike, but they’re built from exactly the same six kinds of part.
Try it: robot or not?
Without looking anything up, decide which of these are robots using the sense–think–act test: a traffic light on a timer, a self-driving car, an automatic door, a drone flown by a person, a drone that follows you on its own.
Show answers
- Timer traffic light: not a robot. It doesn’t sense anything; it just follows a clock.
- Self-driving car: robot. It senses (cameras, radar), thinks (computer) and acts (steering, brakes).
- Automatic door: borderline. It senses (motion sensor) and acts (motor), but its “thinking” is a single rule. Many people call it an automated machine.
- Drone flown by a person: not autonomous; a person does the deciding.
- Drone that follows you: robot.
Sense, think, act: automatic doorEasy
For an automatic shop door, write down its sense, think and act parts.
Show an answer
Sense: a motion or infrared sensor above the door. Think: a simple controller with the rule “if someone is near, open”. Act: a motor that slides the door.
Robot, machine or computer?Medium
Classify a washing machine, a smart speaker and a self-driving lawn mower. Give one reason for each.
Show an answer
- Washing machine: mostly a machine. It acts on a timer; newer ones sense load weight, which makes them borderline.
- Smart speaker: a computer. It senses (microphones) and thinks, but has no actuators that move things in the world.
- Self-driving lawn mower: a robot. It senses its boundary and obstacles, decides a route and drives its wheels and blade.
Design a plant-watering robotHard
List the sensors, controller, actuators and power you’d use for a robot that waters a plant only when the soil is dry. What tells you the soil is dry? What moves the water?
Show an answer
A soil moisture sensor (input), an Arduino (controller), a small pump or valve driven through a transistor or relay (actuator), and a 5 V power supply or battery pack. The rule: if moisture is below a threshold, run the pump for 3 seconds, then wait an hour before checking again.
Quick check
Finished this lesson?