Research On Measurement Of Instantaneous Speed Of Engine Based On Vibration And Noise

Speed is an important basis for engine comprehensive performance testing and speed measurement is an important part of the engine research. In fact,the change of speed is regular and speed fluctuation contains abundant information which can reflect the running state of engine comprehensively. Therefore,speed measurement has practical significance for the engine maintenance and fault diagnosis and other industries. Instantaneous speed can provide reliable basis for the analysis of the real-time parameters in the process of engine operation, also, we can take advantage of speed imformation to estimate the engine power which make it become effective means and tools of engine performance test and fault diagnosis. Some traditional methods of speed measurements will bring inconvenience and some inevitable defects to the speed measurement, engine vibration signal and surface noise signal contain rich information and there is some relation between engine speed and the fundamental frequency of the vibration and noise signal.With the development of sensor technology, the acquisition of vibration and noise signal is more and more quick and convenient, so, the method of speed measurement based on vibration signal and surface noise signal has replaced the traditional measuring method to some extent.This paper choose automobile engine vibration and surface noise signal as the research object to carry out speed measurements, compared with the traditional methods, the measurement method is convenient and fast,suitable for all kinds of different types of automobile engine, do not need to consider the engine model and internal structure, also do not need to split part of the engine components. To the engine vibration and noise of the signal acquisition and processing efficiently,this paper designed a set of filtering, level conversion, amplification, automatic gain control in the integration of signal conditioning circuit board, through the experiment proved that the circuit board can be good to collect the signal of vibration and noise and be able to effectively handle the raw vibration and noise signal, has made the very good preparation for behind the digital signal processing and analysis.This paper presents a new method which fuses wavelet analysis and multiple correlation analysis, CZT transform effectively and this method can extract the fundamental frequency from the vibration signal and sufface noise signal accurately in reading at home and abroad related reference and signal processing related books.Wavelet analysis can be very good to vibration signal and noise denoising; correlation analysis effectively improves the signal-to-noise ratio, highlights the characteristics of periodic signal and suppressing the noise further,CZT transform can only for meaningful frequency local analysis, which not only makes the frequency resolution has been greatly improved, and avoid a lot of unnecessary operations, so that the frequency domain analysis results more quickly and accurately.This paper through MATLAB simulation analysis and real vehicle test the relative error of the extraction frequency is less than 0.8% and he accuracy is high and it verifies the reliability of the new method to measure the speed. At last,select the TMS320F28335 digital signal processor to complete the system design.of the tachometer.