Real-time three-dimensional vibration monitoring of rotating shafts using constant-density sinusoidal fringe pattern as tri-axial sensor

Abstract

Abstract The radial and axial vibration signals of a rotating machine are crucial information to understand the machine operation and to diagnose potential faults. Instead of using three single sensors to measure the horizontal, vertical and axial displacements of rotating shafts, a novel non-projection vision-based system was proposed to realize simultaneous measurement of the radial and axial displacements with high accuracy and good reliability using an tailored artificial constant density sinusoidal fringe pattern (CDSFP), which was pasted around the shaft surface and worked as a tri-axial (i.e. the horizontal, vertical and axial) displacement sensor. The measurement principle and setup of the proposed measurement system were well established. The horizontal displacement could be correctly obtained from the fringe period density changes of the CDSFP image sequence recorded by a high-speed camera. Simultaneously, the vertical displacement could be acquired by tracking the centerline of shaft whilst the axial displacement could be obtained by locating the peaks of the cross-correlation sequence of the fringe intensities. A sub-pixel method was employed to improve the displacement resolution of the developed system. The performance of the proposed system was demonstrated by the comparison of the experiments using eddy current sensors. It showed that the proposed method was an effective and accurate technique for real-time tri-axial vibration monitoring of rotating shaft. Experimental results verified the feasibility, effectiveness and good robustness of the proposed methodology, which demonstrated that the proposed system was capable of achieving accurate tri-axial vibration displacements of rotating shaft compared to the commercial eddy current sensor which could only measure one dimensional displacement at each measurement. Therefore, the vision-based tri-axial vibration monitoring system could be recommended for real engineering applications in condition monitoring of rotating shafts.