Study On The Feature Extraction Of Motorcycle Engine Abnormal Sound

The current detection method of motorcycle engine abnormal sound is artificial auscultation, which is very subjective and easy to make mistakes. Therefore, it is necessary to establish an evaluation system of engine abnormal sound that detects engine sound objectively and quantitatively and improves the accuracy. In this paper, a detection method of the engine abnormal sound based on the vibration and acoustic signal is proposed. The method using modern signal processing technology analyses abnormal sound and extracts the fault characteristics.Based on vibration signals of abnormal sound on motorcycle engine cylinder head, shock signals in a cycle show clearly combining with timing angles and photoelectric sensor signal as reference signal, and characteristic values of every cycle are computed by time-domain statistical functions; compared to the spectrum of normal engine, characteristic frequency is found; vibration signals energy distribution is researched between normal and abnormal engines by the use of order analysis, as well as the energy difference between every order. The results show, three kinds of method can identify abnormal sound of cylinder head. From the spectral analysis and envelope analysis of the signal from right engine, the frequency of abnormal sound at 5kHz-6kHz and 3.3kHz-4.3kHz are found, and then abnormal frequency at 3.7kHz-4.2kHz is also found by acoustics interaction filter. From the analysis results of right engine abnormal sound, the fault frequency is not frequency of gear connection, but high frequency. And with the increasing speed, the fault frequency is constant, but its energy gradually increases. Normal engine and abnormal engine are classified by the k-means algorithm, and the result shows the characteristic parameters are feasible. Squeal is caused by balancing shaft gear and timing gear,and its fault frequency reflects in gear frequency and harmonic frequency that can be recognized obviously by 3-D waterfall spectrum and order tracking.Though sound intensity of the top and right side of engine, 2kHz-2.3 kHz and 2.3 kHz-2.5 kHz are confirmed as the frequency of normal engines and noise sources containing 5kHz -6kHz concentrate on Vice- clutch and oil pump.