Assessment of Quadratic Nonlinear Cardiorespiratory Couplings During Tilt Table Test by Means of Real Wavelet Biphase

In this paper a method for the assessment of Quadratic Phase Coupling (QPC) between respiration and Heart Rate Variability is presented and applied to study cardiorespiratory couplings during a tilt table test. Strong QPC related to the dominant respiratory frequency is present and remains unchanged during Autonomic Nervous System changes.

Fault Feature Detection of Rolling Bearing Based on LMD and Third-Order Cumulant Diagonal Slice Spectrum

Bearing fault signal presents obvious nonlinear and non-stationary characteristics, and local mean decomposition (LMD) method can adaptively process nonlinear and non-stationary signal. Quadratic phase coupling is one of the commonest nonlinear phenomena, and three-order cumulant diagonal slice spectrum is suitable for the extraction of the frequency components involved in quadratic phase coupling. In order to effectively detect the fault features of rolling bearing, a fault feature detection method of rolling bearing based on LMD and diagonal slice spectrum was proposed in the paper. Diagonal slice spectrum was applied in the extraction of the frequency components involved in quadratic phase coupling from the simulation signal, and it successfully extracted the quadratic phase coupling frequency components of the , and . The method was finally used in the detection of the bearing inner race fault features, and the results demonstrated that compared with diagonal slice spectrum of the PF component signals, the diagonal slice spectrum of the PF component envelope signals can identify fault characteristics much clearer and brighter. Meanwhile, the effective extraction of the inner race fault features verified the effectiveness and practicability of the method proposed in this paper.

Application of Bipectrum in Mechanical Fault Diagnosis

Bispectrum produced by third order cumulant contains the asymmetric and nonlinear information of signal, which can be used to describe the nonlinear phase coupling, especially the quadratic phase coupling, has been widely applied in fault diagnosis. The features of fault signals and normal signals are fetched by 2-D wavelet in different directions, then these features are used to diagnose fault. The experiment shows that the method can achieve satisfactory result.