Robust and optimal tuning of PI and PID controllers

A general controller evaluation method based on three performance and robustness criteria is presented. It can be used to compare controllers of different structures, but also as a design method to find the optimal parameter setting for a controller of given structure. In this way optimal PI and PID controllers have been designed for a set of different plants. Clear regularities have then been noticed and utilised to formulate sets of tuning rules for non-oscillating stable plants and for plants with integral action. The rules demand very little plant knowledge but the resulting controllers are close to optimum. Furthermore, the user may adjust one or two of the tuning parameters and still get very good results. This means that the user has some freedom to manage the important trade-off between performance, robustness and control activity.