Abstract: Modulation is common in the vibration signals measured from the gearbox and the meshing frequency components are primary in the signals. The fault characteristic signals of gearboxes are too weak to be detected accurately. According to these characters of the signals, a chaotic oscillator based method is presented to detect the early-stage fatigue crack of gears. Contrary to the common method used in weak signal detection with the chaotic oscillator, this method is based on identifying the reverse state transformation of the chaotic oscillator from the large-scale periodic state to the chaotic state after introduction of the gearbox vibration signal into chaotic oscillator. By this means, the state of two side bands of meshing frequency can be confirmed, and then the crack of gear can be diagnosed. Satisfactory result is achieved in monitoring the crack of the gearbox.

Key words: Chaotic oscillator, Duffing equation, Fault diagnosis, Gear box, Weak signal detection