Study On Fault Diagnosis Of An Unbalanced Wheelset

The deformation of the wheelset of the electric multiple unit is inevitable due to its manufacturing defects or long-term stress. When the wheelset is with the deformation, the mass of the wheelset is not uniform. When the wheelset with the mass unbalance rotates, the unbalanced mass will result in an inertial force of the wheelset. The mechanical vibration caused by the unbalanced inertial force will affect the stability and safety of the train and the comfort of the passengers. The wheelset imbalance detection technology has become an important technology in the development process of high speed trains.In this dissertation, the empirical mode decomposition (EMD) is used in extracting characteristic parameters of the unbalanced wheelset. It can decompose an original signal into a series of basic intrinsic mode functions(IMF). Then the Hilbert envelope of each IMF component is carried out. Finally, the spectrum analysis of each IMF Hilbert envelope is performed to obtain the EMD envelope demodulation spectrum of the original signal. If the peak frequency of the EMD envelope demodulation spectrum coincides with the rotational frequency of the wheelset, the wheelset is considered unblanced.The experimental test shows that when the speed of the wheelset is in the range of 150～200 km/h, the fault signal of the unbalanced wheelset can be identified effectively.Most signal analyses are implimented by MATLAB in the identification of the unbalanced wheelset. It has a very powerful data calculating ability. However the human-machine interface of MATLAB is poor, and MATLAB does not have the data acquisition function. This dissertation uses LabVIEW combined with MATLAB to design the testing procedure. The procedure has the advantage of two softwares.It has the data acquisition and analysis abilities by programming. Moreover, it has a good human-machine interface.