Disturbance-observer-based active control of engine-induced vibrations in automotive vehicles

An approach for active noise and vibration control for systems subject to periodic disturbances with time-varying fundamental frequency is presented. The motivation is active compensation of engine-induced noise in automobiles, where the fundamental frequency (engine firing frequency) goes from 7 Hz (idle, 800 rpm) to 50 Hz (6000 rpm) and the frequency (engine speed) is available. In this new approach, an observer for an input disturbance is designed based on a disturbance model containing all frequencies to be cancelled. The disturbance-model part of the observer is time-varying since the current frequency is measured and fed into this part. Based on this frequency measurement, an observer gain is selected from a set of pre-computed gains. The approach is non-adaptive, and the frequency is a scheduling variable. Theoretical issues of the algorithm (observer design) are discussed and real-time results obtained with an active control system in a vehicle are presented. These results show a major reduction of the interior sound pressure level in the vehicle.