Fractional-order IMC-PID controller design for fractional-order time delay processes

This paper presents an analytical IMC based fractional-order PID controller tuning approach for fractional-order processes with time delay. The conventional IMC scheme utilizing first order filter suffers from the inability to reject the input disturbances of integrating processes. To tackle this issue, a new three-degree-of-freedom IMC scheme equipped with an active disturbance rejection controller is presented leading to a perfect regulatory response. Using user-specified gain and phase margins, a novel tuning technique is proposed simply correlating adjustable parameter to the process time delay while minimizing the ISE performance index. Simulation results patently elaborate the simplicity and superiority of the proposed approach in providing solid performance for both servo and regulatory responses while retaining robustness against the parameter variations.