Robust feedback controller combined with the remote microphone method for broadband active noise control in headrest

This paper proposes a design method combining the remote microphone method (RMM) with a robust fixed feedback controller to achieve active noise control in a headrest with physical microphones situated far from the target zone. Design objectives of the controller are based on a mixed H₂/H_∞ method and the proposed closed-loop gain margin constraint, which consider noise reduction performance, waterbed lift, and robustness against plant perturbations due to slight rotations of the head. Meanwhile, the design objectives are constructed with RMM to create a local zone of quiet far away from the physical monitoring microphone. Particle swarm optimization algorithm is employed for this multi-objective design problem to efficiently generate the feedback controller consisting of cascade second-order sections infinite-impulse-response (IIR) filters. Simulations and real-time experiments were conducted to demonstrate the superior noise reduction performance and robust stability of the designed IIR feedback controller in attenuating broadband disturbances measured in a vehicle.