Image based Spatial-Temporal Information Retrieval for Vibration Measurement

摘要

Image sequences recorded by high-resolution digital video cameras contain vast amount of spatial-temporal information of targeted objects.With the rapid increase of image resolution,these digital cameras can now be used to measure three-dimensional complex motion of structures with sufficient accuracy for the purpose of modal analysis or health monitoring applications.In this paper,a measurement technique based on image sequence analysis is proposed for extracting spatial-temporal responses of continuous structures.Two digital cameras are used to record two-dimensional(2D)image sequences of a three-dimensional(3D)structural vibration response.This structural vibration response is reconstructed using the two 2D image sequences through the epipolar geometry theory without the use of any pre-installed targets.The obtained displacement response provides a more direct way to quantify the modal properties of the structure.To demonstrate,a laboratory test was conducted to measure the free vibration of a cantilever steel rod.Furthermore,a field test to measure vibration of a bridge cable was also performed Results show that the proposed technique can obtain excellent results as compared to the analytical solution.The proposed technique provides a lowcost alternative to measure 3D vibration of low-frequency flexible structures in a non-contact and non-target fashion.