Orthogonal adaptation for multichannel feedforward control

Abstract

In active noise control, it is desired to generate destructive interference by model-independent control. This is possible for single-channel systems to which a recently proposed method, called orthogonal adaptation, is applicable. In this study, the new method is extended to multichannel systems. An important issue is how to optimize a feedforward controller in the minimum H2 norm sense. In practice, secondary paths of some multichannel systems may be nonminimum phase. It is a difficult problem to design H2 feedforward controllers for multichannel systems with nonminimum phase secondary paths. The problem is solved analytically here with the best achievable, a practical and an economical solution. A recursive least squares algorithm is presented for online identification of multiple paths without persistent excitations. These solutions make it possible to implement noninvasive mode-independent controllers for multichannel systems. Experiment results are presented to verify the analytical results.