Fault diagnosis of gear transmission system on LMD and Cyclostationary Demodulation

Gear transmission system is as an important part of the vehicle, and its work reliability directly affects the working performance of vehicle. A JZQ-250 gear transmission system is as the object, and the gear’s and bearing’s characteristic frequencies of gearbox are got by analyzing the test platform, structure parameters, operating principle, and the layout of measuring point. The vibration signals are collected and analyzed in normal status, tooth wear, and outer ring failure condition under the motor speed as 600r/min, the sampling frequency for 4000Hz. By using cyclostationary demodulation method, directly demodulate the vibration signals, and get their cyclic spectrum and cycle frequency axis projection, and analyze the frequency aliasing phenomena. By using the local mean decomposition, obtained time-frequency distribution can clearly and accurately reflect the distribution regularities of signal energy in space various scales. First LMD decomposition downs to the vibration signal as individual components’ modulated signal, the calculation of energy of various components, and normalization processing, wherein the decomposed energy concentrated product functions proceeded the cyclostationary demodulation, obtained their cyclic spectrum, then the cyclic spectrum are combined and analyzed slices map in mesh frequency, they inhibit the influence of cross interference items directly use cyclostationary demodulation.