Adaptive and robust feedback controller for active control of sound and vibration

An adaptive feedback system for the active control of sound and vibration is investigated. The controller combines adaptation for minimum variance of the error, to achieve optimal H₂ performance for every disturbance, and H_∞ robust stability measures, to account for uncertainties in the plant. An Internal Model Control configuration is used, with a fixed FIR filter for the plant model, and an adaptive FIR filter for the controller. The adaptation is performed using the Filtered-x LMS algorithm, which is modified so that it converges to a robust controller. The considerations for using this design in active control are discussed, and implementation results on active noise reducing headphones are presented.