Two-Degree-of-Freedom Active Noise Control Design Based on System Identification Result using Subspace Method

We have proposed the two-degree-of-freedom active noise control (2 DOF-ANC) system, especially for active control of road noise inside automobiles. In this 2 DOF-ANC system, the feedforward part is a conventional filtered-x LMS (least mean square) adaptive control and the feedback part is based on an Internal Model Control (IMC). The purpose of this paper is to apply the subspace method to the identification of an IIR (infinite impulse response) model for an acoustic field in the proposed 2 DOF-ANC system. The IIR model is used to synthesize the feedback controller based on IMC and to reduce the number of arithmetic operations in feedforward control. The subspace method allows us to quantitatively determine the number of parameters in the IIR model. The effectiveness of the subspace method in the proposed 2 DOF-ANC system is demonstrated through computer simulations using actual vehicle data measured in the experiment which simulates road noise in the cabin.