# 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)

# Laser Scanners

Results in a list of ranges and a list of angles (often implicit)

# 3d Range Finders

aka "depth camera" using spherical and cylindrical projection.

# 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