Research On Vibration Sources Identification Of Tractor Cab Based On Wavelet Packet And Spectral Correlation Analysis

As the main part of the tractor NVH (Noise, Vibration, and Harshness), the vibration of tractor cab has a direct impact on ride comfort, vibration and noise level of tractor cab, and physical & mental health. Based on wavelet packet and spectral correlation method and for the purpose of controlling the tractor cab vibration, this paper identifies vibration sources of the tractor cab in different frequency subband and put forward the targeted vibration control scheme.When tractor works, the cab will be affected by multiple source of vibration excitation, and each source has its own frequency characteristic, which will inevitably lead to different vibration source has different influence on the cab in different frequency band. When multiple vibration sources coexistence, to reduce cab vibration efficiently we should control the main vibration sources. So, in order to control cab vibration we should target control the dominant vibration source in different frequency band. Then, to identify the dominant vibration source in different frequency band become the first work for cab vibration control. However, most existing vibration source identification methods take the full spectrum of vibration signal as the research object, and only identify one single dominant vibration source in the full spectrum, ignoring the influence of vibration in the local spectrum. Taken the engine’s four-point supporting as the research object, this paper identifies the dominant vibration source and the dominant vibration frequency of the tractor cab floor in different frequency subband, which provide some guidance for the vibration control of tractor cab.Using simulation signal, this paper firstly studies the feasibility of vibration sources identification method based on wavelet packet and spectral correlation. This method firstly decomposes signal into several sub-signals which have the same frequency band (refer as frequency subband signals in the following) in frequency domain and after that identifies the frequency subband signals’dominant vibration source with spectral correlation method, which can achieve the purpose that identify the dominant vibration source in different frequency band. The study result indicates that this method can clearer show local frequency correlation than full-band correlation analysis and has the ability of identify the dominant vibration source in different frequency band.Secondly, this paper identifies the dominant vibration sources and the dominant vibration frequency of the tractor cab floor in different frequency band with this method. Obtain cab and engine’s four-point supporting’s vibration acceleration signals by test. Firstly, obtain vibration subband signals which have the same frequency band by using the solution of four grades of the wavelet packets method, and then analyses all the vibration signals according to wavelet packet node energy. Secondly, calculate spectral correlation coefficients of frequency subband signals with spectral correlation method and identify the dominant vibration sources. From the results we can find that cab floor vibration signal has his main source in each frequency subband and that cab floor vibration signal’s sources are different in different frequency subband. Finally, identify the dominant vibration frequencies of the dominant vibration sources based on the spectral analysis method.Finally, based on vibration source identification results and combined with rubber absorber and the FEM structure optimization methods, this paper put forward the targeted vibration control scheme, calculating engine’s vibration absorber stiffness, optimizing cab structure and verifying the vibration control effect by experiments. This paper provides a new idea for tractor cab vibration control.