Optimal tuning of PID controllers for integral and unstable processes

Abstract

Tuning formulas for PID controllers applied to integral and unstable processes are presented. In particular, the controller parameters are determined, based on the process model, to minimise integral performance criteria such as ISE, ITSE and ISTE. Results have been obtained by means of genetic algorthms, in order to avoid local minima in the optimisation procedure. Both the set-point following and the load disturbance rejection design specifications are addressed. The achieved results can be adopted both for tuning purposes and for the evaluation of the performances of a pre-existing PID controller.