Analytical design of PID controller cascaded with a lead-lag filter for time-delay processes

Abstract−An analytical method for the design of a proportional-integral-derivative (PID) controller cascaded with a second-order lead-lag filter is proposed for various types of time-delay process. The proposed design method is based on the IMC-PID method to obtain a desired, closed-loop response. The process dead time is approximated by using the appropriate Pade expansion to convert the ideal feedback controller to the proposed PID•filter structure with little loss of accuracy. The resulting PID•filter controller efficiently compensates for the dominant process poles and zeros and significantly improves the closed-loop performance. The simulation results demonstrate the superior performance of the proposed PID•filter controller over the conventional PID controllers. A guideline for the closed-loop time con-stant, λ, is also suggested for the FOPDT and SOPDT models