Research On The Virtual Instrument System For Engine Vibration Diagnostic

Engine is moving in small, automated, integrated development, but also widely was used in agriculture, industry, transport, defense and other fields, its technical state have a great impact for energy consumption and environmental quality. Engine vibration signals are signs of engine fault, direct performance technical status of the engine. Therefore, condition monitoring for the engine vibration signal in real time is effective way to judge the engine fault. It broke the traditional instruments shortcomings of fixed-function, single, bring inconvenience and become the mainstream of test instrument with the rapid development of virtual instrument technology in the automatic detection, data acquisition, instrument control, measurements. Therefore, engine vibration diagnostic system base on virtual instrument to achieve real-time monitoring, diagnostic of engine fault, using characteristics of virtual instrument.This paper introduces engine fault diagnosis purpose, significance and research status in international. It describes the system software LabVIEW virtual instrument concept, characteristics and application development. According to the structure and operation characteristics of the engine, using 4G65 engine as the research object and anglicizing main route of transmission of engine vibration signal, connected to the PCI-8210 data acquisition card and BZ1185 piezoelectric accelerometer acquisition engine vibration signal, and final to achieve signal acquisition, signal processing ,signal analysis , data storage, data query, data story by software LabVIEW. Single and multiple sensors and data acquisition card was used to achieve the single or multi-channel signal acquisition, monitoring, display and contrast engine vibration signal of normal and fault state to realize engine fault diagnosis function, and stored fault data in the fault database. System was mainly implemented on-line monitoring and off-line diagnostics functionality. On-line monitoring realize initial diagnosis to engine working status by driver function of data acquisition card to evenly spaced real-time collection engine vibration signals and calculate the RMS value, and ultimately stored in standard database. Users call the RMS value of the standard database as the alarm threshold under different conditions operating. The alarm light flashes and stored fault database when collecting data achieve the alarm condition. Off-line diagnosis mainly determines engine fault location and cause by anglicizing fault data. Off-line diagnostic main use modular programming ideas, which includes data analysis and data processing module, data storage module, document management module. Data analysis module includes time-domain analysis module, relevant domain analysis module (autocorrelation analysis, correlation analysis), frequency domain analysis module (furrier transform, power spectrum analysis, cross power spectrum analysis, cestrum analysis) Joint time-frequency analysis module (short time furrier transform, wavelet analysis). Different signal analysis and processing methods was compiled to independent sub-vi, diagnostic function module will combine, using software menu feature. The diagnosis module was based on user needs and signal characteristics. System will call the VI, click on the menu contents to anglicize engine signal, when the system only need to add functionality programmed sub-VI. When the system need to add new function, function modules sub-vi was added to menu to realize new function that need not changes whole system. Signal was acquainted at different speed in normal, cut off oil, inadequate intake in 4G65 engine by off-line diagnostic analysis module analysis fault data. Experiments confirmed that it greatly improve the diagnostic accuracy and efficiency.