Predictive PID controllers

Abstract

The design of predictive PID controllers with similar features to the model-based predictive controllers (MPC) is considered. Corresponding to a prediction horizon of size M, a bank of M parallel conventional PID controllers is defined. All the controllers have the same three terms gains, but the ith controller operates on the future error signal at time (t+i). A known future set point and dead time can be easily incorporated and the input constraints can be handled via the solution of constrained MPC problem or integral windup techniques. The stability of the closed loop system is studied and the optimal values of PID gains are derived. The controller reduces to a conventional PI or PID controller for the first or second-order system, respectively. The controller can be implemented on the existing process control hardware and the conventional PID tuning knobs can be used to adjust the controller performance. Simulation studies for a number of different systems show that the controller performance is close to an MPC type control algorithm.