IMC based PID controller tuning of series cascade unstable systems

A simple method of tuning series cascade systems for Integrating, Unstable First order plus time delay process is proposed. Here the PID controller is analyzed for series cascade process based on IMC method and H2 minimizat ion. Maclaurin series is used to approximate the controller expression as a PID controller. Improved closed loop performances are achieved with the proposed method when compared to the recently reported methods in the literature. Further, an analysis is carried out based on maximum sensitivity for arriving at systematic guidelines for selection of the closed loop tuning parameter which is essential for unstable systems. The robustness for uncertainty in the model parameters is studied and compared with that of the controllers reported by Lee et a l. (2002).