Performance of a Multiple versus a Single Reference MIMO ANC Algorithm based on a Dornier 328 test data set

摘要

In many active noise control (ANC) applications, the primary noise source is periodic. In these cases, successful noise reduction can be achieved by using an ANC system based on a feedforward technique. This technique is commonly used in aircraft application where the propeller bladepassage noise frequency is the main noise problem and is to be reduced. However, the adaptive feedforward controller requires reference signals from the primary noise sources. The achieved noise attenuation depends on the correlation between the reference signals and the primary noise. To achieve an efficient noise reduction the correlation must be significant. In applications where the noise originates from only one source a single reference controller will work well. Whereas if several independent sources contribute to the primary noise, one reference signal from each source is needed to achieve a successful noise reduction. Today, most twin propeller aircraft is fitted with a synchrophaser, a device which synchronizes the propellers. The synchrophaser can not keep the propellers synchronized during the complete flight cycle. When the propellers are perfectly synchronized they act as two correlated noise sources, but in cases with unsynchronized propellers, they may act as uncorrelated sources, with different BPF frequencies. In this paper, a comparison study between a single-tacho and a twin-tacho controller system in two different flight conditions with and without synchronized propellers is presented. The simulation and prediction results show the global mean noise attenuation as well as the narrowband mean reduction versus time. Data from a Dornier 328 aircraft has been used in the evaluation.