Virtual feedforward control for asymptotic rejection of periodic disturbance

In this paper, a novel, simple yet effective control scheme, called virtual feedforward control (VFC), is proposed for asymptotic disturbance rejection. The VFC control is an add-on function on top of normal feedback control, and it is activated when a periodic disturbance is found to be present in the system, based on output measurements and detection of output periodic behavior. It is shown that the proposed control can reject the periodic disturbances asymptotically under the perfect plant modeling. Furthermore, the closed-loop stability is not affected by the proposed control and, thus, there is no design tradeoff between disturbance rejection and stability. The robustness of the proposed control to model mismatch is analyzed. The effectiveness of the proposed method is sustained by simulation and comparison