Design of digital controllers for double-loop systems based on series expansions

Abstract

A method of designing digital controllers for a double-loop system is presented based on series expansions of pulse transfer functions. The controllers can achieve approximately an arbitrarily specified response. Simulation studies are performed for some plants, and the results are compared with those for single-loop systems reported before. Both systems give similar responses to a step reference input. However, the double-loop system gives a smaller response to a step disturbance.