Analog Interfacing to Embedded Microprocessor Systems, 2nd Edition

the motor shaft for a 500-count encoder. Notice that the position initially in-

creases 5 steps per sample interval, then 10, then 20, and so on. This acceleration

profile is reversed when the motor is stopping.

Software Considerations

The PID loop controls motor position. In many designs, having a critically

damped waveform is crucial. Remember that this is a mechanical system—over-

shoot may result in broken parts.

The problem of offset in a PID loop, where the final position is just slightly

different from the desired position, can cause a unique problem in a motor

control application. There is usually a plus or minus 1 count ambiguity in any

digital ...