PI-PD smith predictor based cascade controller designing

Abstract

Cascade Control (CC) scheme is one of those most successful control strategies that can be used in process control applications where time delays are long and disturbances are strong. Cascade control strategy combined with Smith Predictor (SP) scheme proves to be more beneficial in improving the control performance as compared to conventional cascade scheme. This paper presents a control strategy, using a PI-PD SP structure for outer loop and results in significant improvement in control. PI-PD controller is designed in such a way that the delay free part of output of system will follow the response of outer loop, assuming that the model and actual plant has a perfect match. Plant models are obtained using Process Reaction Curve Method. Simulation results show comparative analysis of conventional cascade, conventional SP, single loop and PI-PD SP approach.