Three-dimensional translation vibration measurement system based on linear array sensor and composite fringe pattern

Abstract

The vibration signal of a structure gives crucial information to understand its condition. A novel three-dimensional (3D) vibration measurement system is proposed, based on a linear array sensor (LAS) and a composite fringe pattern (CFP), for monitoring a rigid structure with translation displacement along each direction. The CFP is composed of three sinusoidal fringe sets. Two parallel sinusoidal fringe sets on both sides of the CFP and an inclined one in the middle. The displacement along the imaging optical axis could be obtained from the center distance variation of the parallel fringe sets in the recorded CFP. Meanwhile, the vertical displacement could be acquired from the variation of the center distance ratio of the fringe sets. The horizontal displacement could be obtained by locating the symmetric center of the parallel fringe intensity. A peak locating algorithm was created to realize sub-pixel displacement measurement without an increase in the amount of computation. Simulation results verify the feasibility, effectiveness and robustness of the proposed algorithms. The measurement performance of the proposed system was also verified by comparison experiments, whose results demonstrated that the proposed system is capable of recovering structural 3D displacements. Therefore, the proposed vibration monitoring system could be recommended for real engineering applications in the 3D translation vibration monitoring of rigid structures.