A Frequency Domain PID Controller Design Method Using Direct Synthesis Approach

In this study, the PID controller design method based on direct synthesis approach for achieving the desired set-point or load-disturbance response is proposed. The PID controller is derived using an approximate frequency-response-matching criteria. A simple criterion has been also provided to choose the frequency points for matching of the proposed PID controller with the desired direct synthesis controller. It is a unified approach which deals with broad class of processes including integrating and inverse response, and it is directly applicable to any order of process with time delay. The ideal controller based on the direct synthesis approach has been directly approximated to the PID controller in desired frequency range. Therefore, the proposed method is free from model reduction in high-order process to low-order process and also rational approximation of the time-delay term e−sL. The advantage of method is illustrated through examples taken from the literature and compared with some of the well-known methods.