Non-symmetrical Optimum Design Method of Fractional-order PID Controller

This paper presents novel non-symmetrical optimum based design of fractional-order PID controller (FOPID). Optimal parameters of FOPID controller are obtained through minimization of the integral gain combining non-symmetrical criterion constraints and specified phase margin. Fractional-order parameter α is an integral part of optimization procedure and is obtained as solution with other parameters of FOPID controller (k
_p
, k
_i
, k
_d
) for adopted filter time constant T
_f
. The effectiveness of the proposed method is tested with several representatives of typical industrial processes and comparison with PID controller optimized in the same manner is performed to demonstrate performance and robustness improvements of the closed-loop system with FOPID over PID controller.