A feedback control system employing spatial and temporal filtering has been described and its performance has been investigated when applied to the active control of road noise m a small city car. The controller, which is based on modal feedback strategies, has been described and it is shown that despite employing a number of error sensors and sources it behaves as a SISO system. A novel method of optimising the transducer weightings to achieve control of the composite error signal over a specific bandwidth has been detailed and a simple temporal filtering method previously employed in modal feedback control is described. The performance of the proposed controller has been evaluated through offline predictions, using plant responses and disturbance data measured in a small city car. The offline simulations predict reductions of up to 10 dB in the composite error signal over the targeted bandwidth. Unfortunately, however, this is predicted to make very little difference to the sum of the squared microphone signals, which is a measure of the global pressure level in the vehicle. This is believed to be due to the fact that the enclosure's response over the targeted bandwidth has contributions from a number of acoustic and structural resonances, which are excited in a complex way by a number of uncorrelated noise source, and the single channel controller cannot independently control each of these resonances. In vehicle enclosures, such as estate cars or station wagons, where a well separated acoustic mode occurs the presented system may, therefore, achieve significant levels of global control. However, in order to provide a more general solution that may be able to control several dominant resonances, a multichannel extension of the presented control strategy is currently being investigated.
Spatial and temporal filtering for feedback control of road noise in cars
2012
8 Seiten, 3 Bilder, 13 Quellen
Aufsatz (Konferenz)
Englisch
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