Design and Performance Assessment of Variable Fractional Order PID controller

This paper puts forth a new controller design of Fractional Order PID (FOPID) controllers i.e., Variable Fractional Order PID (VFOPID) controller. It has been contrived by utilizing three distinct values of λ (integral order) and μ (derivative order) considering different regions of process output. Existing control schemes like Ziegler Nichols (ZN) tuning, Fixed Set Point Weighting (FSPW) and Variable Set Point Weighting (VSPW) fail to provide satisfactory results in both, initial transient and load rejection phases. In this context, VFOPID can provide better response during both phases. The effectiveness of the proposed VFOPID controller is demonstrated by considering two different process models and their perturbed models in MATLAB simulation platform. The supremacy of the proposed controller is established by comparing the various performance indices of existing control methods and the suggested controller. From the results it is observed that, VFOPID shows excellent robust control ability under considerable perturbation which makes it superior.