Research on over modulation response and demodulation method of motor current signals for rolling bearing faults

Abstract

In order to solve the over modulation frequency aliasing problem caused by high frequency mechanical fault in the analysis of stator current signals, the over modulation phenomenon and the reason of frequency aliasing are analyzed by digital simulation technology. A single-sideband modulation frequency-shift demodulation method is proposed by reference the principle of single-sideband Weaver modulation and demodulation in carrier communication. The local impact fault detection in rolling bearings outer ring is taken as an example, the mechanical model of the impact torque is established when the rolling element passes through the local fault of the outer ring. On the basis of this, it is carried out that the fault model simulation analysis of motor driven rolling bearing, and comparing with the actual motor stator current signal measured by rolling bearing fault analog test bench. The results show that although the motor stator current signal can effectively modulate the high frequency impact signal such as the rolling bearing local defect, spurious aliasing frequency components tend to exist due to over modulation phenomenon. The modulation single-sideband signal frequency-shift demodulation spectrum proposed in this paper can effectively solve these problems, which provides a new solution to extract high frequency modulated signals for the stator current analysis diagnosis method.