Modified Disturbance Observer based Control for Periodic Disturbance Rejection in Time-delay Process

This paper investigates the periodic disturbance rejection control of time-delay process by integrating a modified disturbance observer (MDOB) and internal model control (IMC) structure. A modified disturbance observer design method based on zero-pole placement is proposed. By the MDOB, periodic disturbance can be accurately estimated and the estimation is used as compensation to suppress disturbance. Precise analysis of using MDOB to overcome model uncertainty and external periodic disturbance is given. In addition, the control scheme has two degrees of freedom, in which the IMC controller is used to get desired tracking performance. The simulation results demonstrate the effectiveness of the proposed method for both minimum phase and non-minimum phase system with time-delay.