The Study Of Using Virtual Instrument In Engine Vibration Testing And Analyzing

Engine vibration signal is the information carrier of engine working conditionand fault symptom. Further more, as main analyzing and testing measurement,vibration signals were utilized 20 years ago, and series of important engine testingresearch works were completed based on vibration signals.In this thesis, the concept of Virtual Instruments and the composition ofLabVIEW software development platform were introduced. Then, the application incars and engines in China and in foreign countries were summarized. The enginevibration measuring and signal analyzing technology were deeply studied. Somenon-stationary signal analysis and processing methods, which were utilized in theengine vibration signals analyzing, such as Short Time Fourier Transform,Wigner-Ville Distribution and Wavelet Analysis were reviewed.With Virtual Instruments concept and signal process methods, the enginevibration testing and analyzing system was founded using LabVIEW softwaredevelopment platform. Using this system some measuring and analyzing works werecompleted such as the real time data acquisition of engine vibration signals, thecalculation and the evaluation of engine vibration severity, the time domain analysis,frequency domain and joint time-frequency analysis. The software module to extractengine knock feature was developed, which was based on the principle of dyadicdiscrete waveform transform.Many experiments were performed for verifying the main functions of thesystem. In this thesis the examples of engine vibration testing and analyzing workswere presented. Some testing and analyzing results were acquired and thecharacteristic of engine vibration signals, which gave assistance for vibration sourcesrecognition and default diagnosis of engines, were basically discovered. The pressuresignals of engine were decomposed by waveform transform and the engine knockfeature were extracted from the decomposition results, which were compared with theresults of the traditional filter method. These experiments indicate that it is feasibleand convenient to utilize virtual technology in engine vibration testing and signalanalyzing, which plays the important role for developing the modern engine testingtechnology and the signal process technology.Instead of special signal processing instruments, this system can be used inlaboratories, production field and teaching for testing and analyzing of the vibrationsignals.