ABSTRACT
This chapter discusses the selection of sampling rate for a digital control system. As the sampling rate is increased, the performance of the digital controller usually improves. Computer cost also increases because less time is available to process the controller equations. Reducing the sample rate for the sake of reducing cost, however, may degrade system performance or even cause instability. Additionally, for systems with analog-to-digital converters, higher sample rates require faster A/D conversion speed which may also be expensive. Sampling is the process of deriving a discrete-time sequence from a continuous-time function. The main objective of many digital control system designs is to select a controller so that the system-tracking output, as nearly as possible, tracks or “follows” the tracking command input. An interesting problem involving the sample rate selection is encountered in the control system design of flexible spacecraft.
