Proprioceptive Sensors

Proprioceptive Sensors

Proprioception is dead reckoning, where the robot measures a signal originating
within itself. In biology, this is usually some measure of how far an
arm or leg has been extended or retracted. In robotics, actuators are generally
SHAFT ENCODER motors. Many motors come with a shaft encoder which measures the number
of turns the motor has made. If the gearing and wheel size is known, then the
number of turns of the motor can be used to compute the number of turns
of the robot’s wheels, and that number can be used to estimate how far the
robot has traveled.

Proprioception is often only an estimate. This is due to the impact of the
environment on the actual movement of the robot. Arkin in his PhD thesis8
showed that the same wheeled robot, HARV, traveled different distances for
the same encoder count on a sidewalk, grass, and wet grass. The texture of
the different surfaces caused the wheels of HARV mobile to slip to varying
degrees. A robot on a tiled floor might slip twice as much as on dry grass.