Research On Fault Diagnosis Method Of Automobile Engine Mechanical Abnormal Sound Based On Acoustic Signal

The current method of detecting abnormal sound of automobile engine is based on traditional diagnosis methods such as artificial experience auscultatory method and instrument auxiliary diagnosis method.The traditional diagnostic methods are highly subjective,prone to misjudgment.Therefore,it is very necessary to study methods of diagnosing abnormal sound of automobile engine based on objective facts,which is helpful to improve the accuracy of detection and analysis.First,we introduce a brief overview of the domestic and overseas research on non-contact detection of automobile engine faults and summarizes the advantages and disadvantages and feasibility of detecting automobile faults based on engine acoustic signals.It also describes basic theories in this area and analyzes the three factors of the rotating angles of mirror symmetry planes,amplification and the time interval based on the basic theory of polar coordinate transformation method.Finally,the image matching efficiency is described.Then,we take the car four-stroke inline engine as the research object,through the artificial settings of engine mechanical failure,we detect the abnormal sound of the oil bottom shell,the front of the cylinder,the valve tappet and all kinds of mechanical failure and the produced acoustic signals,detailing the test process and test of the hardware system and the system hardware selection and correlate well with experimental matters needing attention are described.In this paper,the measuring condition of engine acoustic signal is introduced,the test position is determined,and the whole design of acoustic signal acquisition system is completed.Of filtering software for all kinds of auto engine acoustic signals of polar coordinate transformation theory analysis,the analog signal in the assessment of the effect of selected,with measurement of engine acoustic signal of engine abnormal sound detection analysis.Lastly,we analyze acoustic signal data of engine using polar coordinate transformation method and makes feature maps of four acoustic signal types respectively:the normal fault free engines,engines with abnormal sound at oil bottom shell,engineswith abnormal sound in the front and engines with abnormal sound in valve pillar.It also forms feature maps of the polar coordinate transformation image by analyzing 10 groups of data on various defects of the engine to prove that the polar coordinate transformation method can accurately detect the abnormal sound of engine.