Optimal tuning of PID controllers for integral and unstable processes

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 squared error performance criteria. Results have been obtained by means of genetic algorithms, 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