Sub-band Energy Method Resarch On Viberation Siganl Of Engine

This paper mainly study vibration signal on the surface and hood of the DA462 cylinder engine, and analyzes and calculates the measure signal in the time domain, frequency domain, and I have proved and summarized the calculation results.I have put up a practical vibration signal test system. We changed the valve clearance to simulate the failure of engine. In the valve clearance and different rotate speed, we tested much vibration signal.This paper analyzed the signal in the time domain and frequency domain, after analyzing, I made the following conclusions:(1)We could observe something in the time domain. I saw prompting and respond of the inlet and exhaust valve opened or landed would be enhanced along with increasing gap valve, and prompting and respond of the combustion would be enhanced. Thus, the work state of engine was unstable with the change of valve clearance.(2)As the engine idle speed unstable, we bring forward the concept of the instantaneous frequency, and we deduce the formula that about the instantaneous frequency and the relationship between the crank angle of DA462-engine, finally we achieved formula for the instantaneous frequency of DA462-engine, and use this formula to orient signal benchmark.(3)I described two sub-band division method in the frequency domain, and brought forward idea that the energy unitary, and the use one of them to decompose and calculate the entire frequency band. After analysis the results, I could achieve to the band of each prompting and respond, and we used this section energy to determine whether or not unconventionality about the size of valve clearance.(4)This paper summarizes the change and drift law of each characteristics frequency band with the rotate speed changed under the same valve clearance. This paper detailed introduces the sub-band energy method. First, it proposed this method from the energy point of view, second, it told a sub-band arrangement method, third, we used this method to analyze vibration signal and made some calculation, the end, we obtained conclusions. Through using the sub-band energy method, we found this method has simple, accurate and practical features.