In Processing Fault Detection of Machinery Based on Instantaneous Phase Signal

The instantaneous phase signal contains abundant information about the health state of machineries, which plays an important role in fault detection of machineries, rotor dynamic balance, transmission error of Rotate Vector reducer, etc. Traditional methods use signal processing methods based on encoders, EMD and Hilbert transforms or fractional delay filters to extract instantaneous phase information indirectly. These traditional methods are state-of-art, however those algorithms are slightly complicated and time-consuming, which is not conducive to online prognostics and health management to some extent. In fact, high precision and high reliability sensor technology can effectively reduce the complexity of subsequent signal processing. In this paper, an instantaneous phase direct detection technique based on eccentric demodulation principle is proposed. The method is derived from the kinematics between the cam and the pushrod. The laser displacement sensor is used to replace the pushrod to realize non-contact measurement. The instantaneous phase is modulation by the cam, and the proposed method can realize the obtain of the theoretical phase infinite resolution, which reaches 16,000-line resolution. Compared with the traditional encoder and other inspection technologies, the proposed method is also suitable for the measurement of broadband shifting and reciprocating motion. By means of simple signal processing methods, this paper realizes the fault diagnosis of the rolling bearing with typical defectives, and realizes the extraction and identification of the fault signal of the reciprocating compressor. Experimental results proved that the proposed inspection technology can serve as an effective technology for mechanical fault diagnosis.