Robotics sensors and actuators explain how a robot senses the world and turns decisions into motion. This cheat sheet helps students connect electronic parts, mechanical motion, and control logic in one quick reference. It is useful for building, programming, troubleshooting, and explaining robots in class projects or competitions.
Sensors measure inputs such as distance, light, force, rotation, or position, while actuators create outputs such as spinning, lifting, steering, or gripping. A robot often uses feedback, where sensor data is compared to a target value and the controller adjusts the actuator. Important ideas include input, output, calibration, error, speed, torque, and simple control rules such as error = target value - measured value.
Key Facts
- A sensor converts a physical condition into data, such as distance in centimeters, light level, button state, or wheel rotation.
- An actuator converts electrical energy into physical action, such as motor rotation, servo movement, solenoid pushing, or speaker vibration.
- Feedback control uses sensor data to adjust an actuator so the robot moves closer to a target value.
- Control error is found with error = target value - measured value.
- For wheel robots, distance traveled can be estimated with distance = wheel circumference x number of rotations.
- Wheel circumference is found with circumference = pi x diameter.
- Speed is calculated with speed = distance / time, and motor power settings often change speed but not always in a perfectly linear way.
- Torque is turning force, and more torque helps a robot lift loads, climb ramps, or start moving from rest.
Vocabulary
- Sensor
- A device that detects a physical condition and sends data to the robot controller.
- Actuator
- A device that creates motion or another physical output when controlled by the robot.
- Servo Motor
- A motor that moves to a commanded angle or position instead of spinning freely.
- Feedback
- Information from sensors that is used to adjust the robot output while it is running.
- Calibration
- The process of matching sensor readings or motor settings to known real-world values.
- Control Error
- The difference between the target value and the measured value, calculated as error = target value - measured value.
Common Mistakes to Avoid
- Confusing sensors with actuators is wrong because sensors read information, while actuators make the robot do something physical.
- Ignoring calibration is wrong because raw sensor values may not match real distances, angles, or light levels accurately.
- Using motor power as exact speed is wrong because battery level, friction, load, and surface conditions can change the actual motion.
- Forgetting units in calculations is wrong because distance, time, rotations, and angles must match the formula being used.
- Reacting to noisy sensor readings instantly is wrong because small random changes can make a robot twitch, overshoot, or make unstable decisions.
Practice Questions
- 1 A robot wheel has a diameter of 6 cm. Using circumference = pi x diameter and pi = 3.14, how far does the robot travel in one wheel rotation?
- 2 A robot travels 120 cm in 4 seconds. Using speed = distance / time, what is its average speed?
- 3 A line-following robot wants a light sensor reading of 50, but it measures 42. Using error = target value - measured value, what is the error?
- 4 A robot arm keeps overshooting the target position. Explain how feedback from a position sensor could help the controller improve the motion.