齿轮故障振动信号精确幅值解调方法

Accurate Amplitude Demodulation Method of Gear Fault Vibration Signal

齿轮故障振动信号中通常包含幅值调制成分,当信号过调制时,常用的包络解调无法准确表示真实的调幅信号。因此,基于希尔伯特变换、平方解调与最小二乘优化算法,提出了一种精确的幅值解调方法。该方法利用希尔伯特变换构造优化目标函数,加入基于平方解调构造的约束方程,通过最小二乘优化算法求解调幅参数,实现了精确的幅值解调。仿真表明:该方法在信号欠调制和过调制时均可以精确重构出真实的调幅信号,具有通用性,抗噪性好。实验分析表明:严重的平稳型故障会导致振动信号出现过调制,断齿故障导致全频带内产生的离散谐波成分影响啮合频率附近振动信号的调制强度。解调结果验证了该方法处理两类齿轮故障的有效性。

The fault vibration signal of the gear usually contains amplitude modulation(AM)components.When the signal is overmodulated,the envelope demodulation has signal distortion,which cannot accurately represent the real AM signal.Therefore,based on the Hilbert transform,square demodulation,and the least squares optimization algorithm,an accurate amplitude demodulation method is proposed.The Hilbert transform is used to construct the optimized objective function,and the square demodulation is employed to construct the constraint equation.Finally,the least squares optimization algorithm is applied to solve the AM signal parameters to achieve accurate amplitude demodulation.Simulation results show that the method is versatile and has good anti-noise performance.The real AM signal can be accurately reconstructed whether the signal is under modulated or overmodulated.The demodulation effect for overmodulated signals is much better than those of the Hilbert transform demodulation method and the new amplitude demodulation method based on square demodulation and least square optimization algorithm.The experimental results show that the vibration signal near the meshing frequency is undermodulated in the case of slight stationary fault,while the vibration signal is overmodulated in the case of severe stationary fault.The fault degree of the gearbox can be judged according to the difference of demodulation results.For the compound fault signal of misalignment and broken teeth,the modulation intensity of the vibration signal near the meshing frequency will be affected by the discrete harmonic components distributed in the frequency domain caused by the broken tooth.The closer the meshing frequency is to the resonance region,the more likely the vibration signal is to be overmodulated.The demodulation results verify the effectiveness of the method in processing two types of gear fault.