A nonlinear diagnosis method of gear early fatigue crack

For gears, periodic impulses indicate that there are faults in the components. However, it is difficult to detect the impulses at the early stage of fault because they are so weak that buried in the noise. According to the characters of vibration signal coming from gearboxes, a method using chaotic oscillator is presented to detect the early fatigue crack of the gear. This method is in a reverse way compared with the common chaotic oscillator based method. After introduction of gearbox vibration signals to the chaotic oscillator, by recognizing the state transformation of the oscillator from large-scale period to chaos, the state of two side bands of meshing frequency can be confirmed, and then the crack can be detected. The method is demonstrated in practice. In this paper, it is also presented how to use symbol sequence statistics to automatically identify the state transformation of the chaotic oscillator.