Multirate sampling technique in digital control systems simulation

Simulation is a useful technique for evaluating the dynamic performance of digital control systems. Digital regulators for continuous plants are designed today by means of conventional c-transfer function methods. With these z-transfer functions the value of the system output y(t) can be learned only at instants-spaced T seconds, where T is the sampling period. A technique is proposed where the value of y(t) can be learned at instants-spaced T/n seconds, where n is any integer. This technique is based on multirate sampling. First a method to calculate the output multirate sampled sequence is described. Then an efficient algorithm to calculate the “multirate sampling discrete transfer function,” from the normal discrete transfer function is proposed.