Abstract: A frequency-adjustable micro-perforated muffler for the air compressor of a fuel cell vehicle is proposed in this paper. Firstly, the relationship between the length of the perforated section of third cavity and the resonant frequency of muffler is fitted based on the transfer characteristics of the micro-perforated muffler designed, the two-phase hybrid stepping motor and ball screw are chosen as the actuator, and a photo-electric encoder is taken as the feedback module. Then, a fuzzy PID controller suitable for frequency modulation system is designed to achieve the real-time adjustment of perforated section length of third cavity for changing the resonant frequency and thus broadening the muffling frequency-band of the micro-perforated muffler. Finally, the test bench for the frequency-adjustable micro-perforated muffler system is built and a test is conducted to validate the noise reduction effect in both the steady and transient conditions of target air compressor. The results of test show that the frequency-adjustable micro-perforated muffler proposed can effectively reduce the order noise of air compressor with the sound pressure level reduced by more than 12dB, and its broadband vortex noise is also reduced by more than 6 dB.

Key words: fuel cell vehicle, test bench, micro-perforated muffler, fuzzy PID