An adaptive feedforward controller for rejection of periodic disturbances

The issue of rejecting periodic disturbances arises in various applications dealing with rotating machinery. A novel adaptive feedforward controller (AFC) design method for rejecting periodic disturbance is proposed. It can be added to an existing feedback control system without altering the original closed loop characteristics, such as the stability margin and transfer functions. An adaptive algorithm derived for the proposed controller based on the steepest gradient descent method turns out to be identical to the popular delayed-x LMS algorithm. A number of computer simulations were carried out to demonstrate the salient features of the proposed AFC compared to the conventional one. The proposed method can be useful for control engineers in designing an adaptive feedforward controller for the rejection of the periodic disturbances. (C) 1997 Academic Press Limited.