Novel IMC filter design-based PID controller design for systems with one right half plane pole and dead-time

Abstract

In this article, design of PID controller using a modified internal model control (IMC) filter for right half plane (RHP) pole process with dead time is proposed. To possess H2 optimal behaviour, the derived IMC controller minimises the integral square error (ISE) for step input disturbances by defining the Blaschke product of unstable poles of the specific input and the model. Then it is converted into a single feedback loop controller as either PID or PID with first order filter on the basis of proposed underdamped IMC filter to improve the integral action and thereby providing fast response which is not feasible with critically damped filter. Maclaurin series approximation is used to design PID controller and Pade's approximation is used to design PID with first order lead lag filter. Various first order plus dead time (FOPDT) examples are taken and simulation is executed on diverse unstable processes and compared with some of the developed methods available in the literature. The two proposed controllers provide improved responses with respect to both nominal and perturbed conditions. The robustness studies have also been carried out for uncertainties in the plant dynamics and it is apparent that the proposed tuning method is robust.