The Study Of Order Tracking Of Vibration Signal Of Engine In Speed Variant Process

With the development of automobile industry and demand of riding comfort of car, design optimization from interior structure to lower engine vibration and noise is needed. How to extract characteristic information from exterior measurement vibration signal and get interior structure information is of vital meaning.This project is to research the order tracking methods to extract rotation related signal and separate disturbed noise from complicated engine vibration signal. Engineers can better understand engine interior structure through extracted order signal, and instruct optimization design from depressing running vibration and noise aspect.In order tracking analysis, it is very important to acquire rotating speed of reference shaft. In practical application, tachometer impulse measurement is not accurate. Therefore rotating speed curve through direct computing impulse arriving time may have big error. Aiming at this problem, a subsection weighing cubic spline curve fit method was proposed in this paper. This proposed method uses cubic spine curve fit rotating speed subsection, and through data overlap and weighing average to ensure continuuty and smooth of subsection point. Accurate rotating speed was achieved.Wildly applied even-angle re-sampling order tracking method is commonly implemented by over sampling data and interpolation, and can only get 65dB signal noise ratio. Base on sampled signal recover theory, an interpolation filter adaptive numeric re-sampling method was proposed in this paper. Adaptive even-angle re-sampling is implemented by a filter which is constructed by pre-established over sampling rate interpolation sin c(t) function. Accuracy of re-sampling andsignal-noise-ratio of order spectrum were improved.Even-angle re-sampling plus FFT order tracking method can get waterfall, order spectrum and order tracking spectrum result view, but it can not get order extraction in time domain. Gabor transform and dual function bi-orthogonal condition to fulfill time domain reconstruction were researched in this paper. Vary center frequency band pass filter in time-frequent domain was implemented to separate order and noise. And order component reconstruction in time domain was achieved by similar duel function least square method iteration. Order component was extracted in time domain by Gabor transform.Engine is complicated in structure, and is consists of rotating and reciprocating movement of many shafts. Orders of different shafts crossing each other in frequency make order tracking difficult. Even-angle re-sampling plus FFT method can only take one shaft as re-sampling reference, extracted order waveform be interrupted by crossing order and cause distortion. A few changes was done on Vold-Kalman adaptive filter, and a band pass filter with center frequency vary with rotating speed was designed. Least square method combined with Kalman adaptive filter can extract orders of multi-shaft, solves crossing order decouple problem.Several simulation signals with different amplitude change were designed. Comparison was done between three order tracking methods. A field experiment scheme was also designed. Test software was programmed by combining Visual C++ and Matlab. Engine test platform and signal collection system were constructed. Expermental data were collected form air powered engine platform and provided by Dactron corperation. Field expremet was carried out by different order tracking methods.Final, a brief summarization of research job was done, and shortcoming and research proposal were put forward.