What is a robot?
A robot is a machine that can sense its surroundings, decide using a program, and act on the world. It works by itself, fully or partly.
Robotics is the field that designs, builds and programs robots. It mixes mechanical engineering (body and movement), electrical and electronic engineering (motors, circuits, sensors) and computer science (programs).
A washing machine follows a fixed timer, so it is an automatic machine. A robot changes what it does based on what it senses.
Parts of a robot: hardware and software
- Structure (body): frame, links and joints. Made of metal or plastic.
- Sensors: measure things. Examples: distance (ultrasonic, infrared), light, touch, camera, temperature, gyroscope (tilt).
- Controller: the brain, a microcontroller or computer that runs the program.
- Actuators: make movement. DC motors, servo motors, stepper motors, pneumatic or hydraulic cylinders.
- End effector: the tool at the end: gripper, welding torch, suction cup.
- Power: battery or mains supply.
- Software: the program. It reads sensors, makes decisions (if-then, loops) and sends commands to motors.
Hardware is what you can touch. Software is the set of instructions.
Structure and transmission: joints, gears and degrees of freedom
A joint lets two parts move. A revolute joint turns (like your elbow). A prismatic joint slides (like a drawer).
Degrees of freedom (DOF) = the number of independent ways a robot can move. Our 3D arm has 2 DOF (shoulder, elbow). A human arm has about 7.
Transmission carries motion from motor to joint: gears, belts and pulleys, chains, screws.
Gear ratio = teeth on driven gear ÷ teeth on driver gear. If the ratio is 3, the output turns 3 times slower but with about 3 times more turning force (torque). Speed and force trade off.
Types and uses of robots across engineering
- Industrial robots: welding, painting, packing in factories.
- Medical robots: helping in surgery, rehabilitation, delivering medicines in hospitals.
- Service robots: vacuum cleaners, delivery robots, guides in malls.
- Field robots: farm drones, underwater robots, bomb-disposal robots.
- Space robots: rovers on the Moon and Mars.
- Humanoids and cobots: robots shaped like humans, and collaborative robots that work safely beside people.
Good points: accuracy, work in danger, no tiredness. Limits: cost, need for power and repair, job changes, safety and ethics.
Key formulas and definitions
- Robot = sensors + controller + actuators + structure + power + program
- Sense → Think → Act (the control loop repeats many times a second)
- Gear ratio = driven teeth ÷ driver teeth
- Output speed = input speed ÷ gear ratio; output torque ≈ input torque × gear ratio
- Degrees of freedom = number of independent joint movements
Worked examples
1. A line-following robot has two light sensors, a microcontroller and two wheel motors. Name the sense, think and act parts.
Sense: the two light sensors see the dark line. Think: the microcontroller compares the two readings. Act: it slows one wheel motor to turn back onto the line.
2. A motor gear has 12 teeth and drives a wheel gear with 36 teeth. The motor turns at 300 rpm. Find the gear ratio and wheel speed.
Ratio = 36 ÷ 12 = 3. Wheel speed = 300 ÷ 3 = 100 rpm. The wheel turns slower but with about 3 times more torque.
3. A robot arm has a rotating base, a shoulder, an elbow and a wrist that both bends and twists. How many degrees of freedom?
Base 1 + shoulder 1 + elbow 1 + wrist 2 = 5 DOF.
Common mistakes
- Calling every automatic machine a robot. A robot must sense and change its action.
- Mixing up sensors and actuators. Sensors take in information; actuators produce movement.
- Thinking a bigger gear makes the output faster. A bigger driven gear makes it slower but stronger.
- Forgetting software. Without a program, the hardware does nothing useful.