Baxter robot picking up ping pong balls
Baxter robot

Sensors and Actuators

Sensors are devices which measure quantities which the robot can use to achieve given tasks.

Examples of what a robot may need to determine include:

  • How far away and where is an object (like another robot, a light, a wall)?
  • At what speed is the robot moving?
  • If the robot is on a hill, at what angle is it?
  • If the robot is rotating, by how much has it rotated?
  • Where is the robot, or in what direction is it going?
  • How far it has it travelled (which is odometry)?
  • How much power has it consumed?
  • What information is being communicated to the robot?

The robot may require internal and external sensors.

External sensors are used to measure other objects, for instance:

  • How far away is an object?
  • Where is the object?

Internal sensors are used to measure the robot itself, for instance:

  • How fast it is going
  • The angle of the robot
  • Where it’s ‘gripper’ is
  • How much power it’s consuming


An actuator is a device which causes something to happen.

This could be a robot movement, which is often achieved using motors:

  • An actuator is needed to make the robots wheels turn.
  • Or the joints of a robot arm to rotate.
  • Or for a robot gripper to open or close.

Or it could be to let the others know what the robot is doing.

  • A light being turned on to indicate the robot is working.
  • Sound is being emitted - so the actuator is a loudspeaker.
  • Communication in some form - so a transmitter is needed.
  • An LCD (Liquid Crystal Display) screen for showing pictures and other data.

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This article is from the free online course:

Begin Robotics

University of Reading