IMC based modified Smith predictor for second order delay dominated processes with RHP

Abstract

A modified Smith predictor (MSP) with IMC based tuning is proposed for second order delay dominated processes. These processes often exhibit unstable behaviour due to right half poles (RHP) with positive or negative zeros. The control scheme incorporates forward path PI/PID controller with a lead–lag filter and a PD controller in the feedback path. IMC technique having single tuning parameter is utilized to design the forward path controller, while the feedback path controller is tuned by Routh stability criterion. The proposed scheme ascertains quick set point following without overshoot and smooth disturbance rejection, resulting superior closed-loop performance compared to recent MSP schemes. Validation is made based on performance indices and stability margins.