Design robust FOPIλD controller for higher-order systems base on D-composition and DE algorithm

The current state of the art of optimization algorithm for tuning the FOPID controller is hard to balance the contradiction between frequency- and time-domain specifications. To overcome this drawback, a graphical tuning method of fractional order PI
^λ
D (FOPI
^λ
D) controller for the higher-order process is proposed to improve the control performance and robustness. The concept of D-decomposition along with the gain-phase margin tester is applied to portray constant gain margin (GM) and phase margin (PM) boundaries in the controller parameters plane. The overlapping region of GM and PM boundaries has been taken to as the optimization region of the differential evolution (DE) algorithm. The time-domain performance requirement has been considered in the cost function of the DE algorithm, which is defined to facilitate the control strategy over the overshoot (σ), settling time (T
s
) and ITAE. The control performances of the proposed FOPI
^λ
D controller are compared with PID and FOPI controllers. The numerical simulation demonstrates the superior robustness as well as the transient performance of the proposed control algorithm.