The wheel encoder is a sensor attached to the motor to sense the number of rotations of the wheel. If we know the number of rotations, we can compute the displacement, velocity, acceleration, and angle of the wheel.

For this robot, we have chosen a motor with an in-built encoder. This encoder is a quadrature type, which can sense both the direction and speed of the motor. Encoders use different types of sensors, such as optical and hall sensors, to detect these parameters. This encoder uses Hall effect to sense the rotation. The quadrature encoder has two channels, namely Channel A and Channel B. Each channel will generate digital signals with ninety degree phase shift. The following figure shows the wave form of a typical quadrature encoder:

Quadrature encoder waveforms

If the motor rotates clockwise, Channel A will lead Channel B, and if the motor rotates counterclockwise, Channel B will lead Channel A. This reading will be useful to sense...