Sensors

Sensors and Actuators

Sensors

Sensors are developed for consumer electronics and larger industries - rarely for robotics itself.

  • Type of information
  • Physical principle
  • Absolute vs. derivative
  • Amount of information (bandwidth)
  • Low and high reading (dynamic range)
  • Accuracy
  • Precision
  • Resolution
Accuracy = 1 - (|m - v|/v)
with m as measurement and v as true value

You can combine sensors (sensor fusion) to get a better idea of what is actually happening.

Accelerometer

F = kx = ma

Measures acceleration by knowing the spring constant k and measuring displacement.

Gives you relative measurement (acceleration - derivative of speed)

  • Tell the pose of an object from the direction of gravity
  • Tell when robot hits an object

Gyroscopes

Measure orientation and rate gyroscopes measure rotational speed.

Relative measurement.

  • Correct robots heading

Wheel/Joint encoder

Relative measurement.

  • Tell rotation of a wheel or a robot arm.

Distance from light intensity

Emitter/receiver pair gives you non linear distance measurement.

  • structure (xbox connect)
  • sound
  • phase shift (with laser scanner)

Actuation

  • Locomotion - moving oneself
  • Manipulation - moving others

Electric motors

DC (brushless) change the polarity in the motor quickly.

Direct Drive

Harmonic Drive

Linear Actuators

Series elastic

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