A novel tuning method of differential forward robust PID controller for integrating systems plus time delay based on direct synthesis method

In this paper, a novel tuning rule of differential forward proportional–integral–derivative (PID) controller for integrating systems with time delay is proposed by using the direct synthesis method. This method is based on comparing the characteristic equation of the system which consists of the differential forward PID controller adding a lead-lag filter and the integrating time-delay process with the desired characteristic equation. The desired characteristic equation is obtained by placing a plurality of poles at the same desired position. Parameters of the differential forward PID are tuned to achieve the desired robustness. Tuning rules are given in terms of plant parameters for various kinds of integrating systems. Compared with the conventional PID controller, the proposed method is more effective for frequently changed set-points. Simulations for various integrating processes as well as the non-linear jacketed CSTR system illustrate the applicability and effectiveness of the proposed method.