Improved fractional filter IMC-PID controller design for enhanced performance of integrating plus time delay processes

In this paper, an improved fractional filter IMC-PID controller was proposed to enhance the performance of integrating processes after identifying the optimum higher order fractional IMC filter structure. The identification involves a systematic procedure based on the minimisation of integral absolute error (IAE). The present design also considers different approximations for time delay. The tuning parameters are obtained based on the prefixed robustness (maximum sensitivity, M-s). The present method is compared with recent methods in the literature and its superiority is demonstrated with performance measures IAE and total variation (TV). Enhanced output performance is obtained for nominal process conditions; for process parameter variations and for noise in the measurement. Robustness analysis is performed using complementary sensitivity function and parametric uncertainty bounds. Also, the fragility analysis is carried out to check the sensitivity of closed loop system for variation in controller parameters.