Design of an enhanced fractional order PID controller for a class of second-order system

PurposeThis paper aims to design a modified fractional order proportional integral derivative (PID) (FO[PI]λDµ) controller based on the principle of fractional calculus and investigate its performance for a class of a second-order plant model under different operating conditions. The effectiveness of the proposed controller is compared with the classical controllers.Design/methodology/approachThe fractional factor related to the integral term of the standard FO[PI]λDµ controller is applied as a common fractional factor term for the proportional plus integral coefficients in the proposed controller structure. The controller design is developed using the regular closed-loop system design specifications such as gain crossover frequency, phase margin, robustness to gain change and two more specifications, namely, noise reduction and disturbance elimination functions.FindingsThe study results of the designed controller using matrix laboratory software are analyzed and compared with an integer order PID and a classical FOPIλDµ controller, the proposed FO[PI]λDµ controller exhibit a high degree of performance in terms of settling time, fast response and no overshoot.Originality/valueThis paper proposes a methodology for the FO[PI]λDµ controller design for a second-order plant model using the closed-loop system design specifications. The effectiveness of the proposed control scheme is demonstrated under different operating conditions such as external load disturbances and input parameter change.