A PID controller with dynamic set-point weighting

A new set point weighting technique is proposed to improve the set point response and load rejection characteristics of Ziegler-Nichols tuned PID controllers. Instead of a fixed (single or multi-valued) set point weighting factor, here dynamic set point weighting is suggested based on the change of error (Deltae) of the controlled variable and normalized dead time of the process under control. The proposed scheme is very simple to implement and can be easily incorporated in an existing control loop. Effectiveness of the proposed scheme is tested on different linear and nonlinear dead time processes under both set point change and load disturbance. Performance of the proposed PID controller with dynamic set point weighting (DSW-PID) is compared with that of a PID controller with variable set point weighting (VSW-PID) reported in the literature as well as Ziegler-Nichols tuned PID controller (ZN-PID) in terms of several performance indices. The result shows a considerably improved performance of the proposed DSW-PID over the others.