Inverse-based Design for a Modified PID Controller

Abstract

A modified PID (m-PID) controller design using low order dynamic models is presented. In contrast to the one of Haggland and Astrom (1985), the controller uses model-based parameters. Synthesis of such a controller is by way of an inverse-based approach. By this approach, a pure lead is introduced into a l=p to make the system equivalent to a modified Smith predictor (MSP) control system. Tuning rules for this m-PID controller are then derived from this equivalent system. For robustness, gain and phase margins are analyzed. It is found that this proposed m-PID control system has good responses to both set-point and load changes. Tuning rules derived from reduction of this m-PID controller for conventional PID control have also been presented.