Design of robust fractional-order controller using the Bode ideal transfer function approach in IMC paradigm

Formulating a fractional-order controller and then implementing it in real-world environment is a challenging task for control professionals. Therefore, this paper proposes a simple, analytical and robust fractional-order controller synthesis scheme using Bode ideal transfer function in internal model control (IMC) paradigm. The controller acquires a PI form followed by a fractional-order integrator. The main advantage of the proposed scheme is that only two tuning parameters are required for satisfying the desired gain crossover frequency and phase margin. The properties of the proposed scheme are examined on the basis of tracking and disturbance rejection attributes. The effectiveness of the proposed method is verified through simulations of linear and nonlinear systems, and it is further experimentally validated on QUBE-Servo 2 set-up to control the velocity of DC motor. The proposed scheme exhibits satisfactory tracking and disturbance rejection performance when compared with integer-order and fractional-order PI controllers.