Chapter 12 – Practical Issues

Publisher Summary The designer of a digital control system must be mindful of the fact that the control algorithm is implemented as a software program that forms part of the control loop. Successful practical implementation of digital controllers requires careful attention to several hardware and software requirements. During the design phase, designers make several simplifying assumptions that affect the implemented controller. They usually assume uniform sampling with negligible delay due to the computation of the control variable. Thus, they assume no delay between the sampling instant and the instant at which the computed control value is applied to the actuator. This chapter discusses the most important of these requirements and their influence on controller design. It then analyzes the choice of the sampling frequency in more detail in the presence of antialiasing filters and the effects of quantization, rounding, and truncation errors. In particular, it examines the effective implementation of a proportional–integral–derivative (PID) controller. Finally, it examines changing the sampling rate during control operation as well as output sampling at a slower rate than that of the controller.