AN ALTERNATIVE FEEDBACK STRUCTURE FOR THE ADAPTIVE ACTIVE CONTROL OF PERIODIC AND TIME-VARYING PERIODIC DISTURBANCES

An alternative feedback Structure, inspired from a speech coding struc ture, is introduced for the adaptive active control of periodic and ti me-varying periodic disturbances. The new structure is an Internal Mod el Control (IMC) structure. It separates the information and the proce ssing pertaining to the plant from the information and the processing pertaining to the disturbance signal. A non-causal filter modelling th e inverse of the secondary path is used, and the future samples of the disturbance signal are estimated by linear prediction (using an LMS a lgorithm). No filtering of a reference signal with the model of the se condary path is required to compute a filtered reference signal. In co nsequence, for the cases presented in the paper, the new feedback stru cture has a much faster convergence behavior and a better transient re sponse than the classical FX-LMS algorithm with a feedback IMC structu re, or the more recent and usually faster ANC-LMS algorithm with the s ame IMC structure. Simulation results with experimentally measured pri mary and secondary paths of a beam are presented, showing that tither for multi-harmonic disturbance signals or sweeping sine wave disturban ces, the structure presented in this paper greatly improves the conver gence behavior of an adaptive feedback controller. (C) 1998 Academic P ress Limited.