Straightforward Design of a Robust Fractional-Order Controller

Fractional-order controllers have emerged as robust alternatives to conventional PID controllers. Existing tuning methods generally focus solely on robustness to process gain variations. This paper introduces a design method for fractional-order PI controllers, specifically resilient to time constant changes by shaping the loop frequency response. This work simplifies the design method by replacing the separate magnitude and phase derivative calculations used in prior techniques with a unified, single partial derivative approach. Instead of using cumbersome optimization routines and graphical analysis used in existing fractional-order controller tuning methods, the proposed approach uses a direct, simple, and efficient 1-step algorithm. Numerical simulations for lag- and delay-dominant processes are included to highlight the efficiency of the proposed approach. Traditional integer order controllers are designed for comparative purposes. The proposed approach achieves a constant overshoot despite time constant variations, an advantage compared to classical controllers.