基于数字图像相关理论的非接触式 结构位移测量方法

为实现结构的位移及挠度测量,开展了基于数字图像相关算法的亚像素位移测量研究.采用改进初值的亚像素算法确定待测结构目标位置的基于像素的位移,利用相机标定方法将基于像素的位移转换为工程单位.在数字图像处理技术的基础上对编写的程序进行数值仿真试验,位移计算结果与理论值吻合良好,验证了该程序测量精度的可靠性.搭建视觉位移测量系统,为了验证该系统的有效性,对钢框架结构模型开展了视觉测量系统和激光位移计的对比试验;研究了相机与待测结构之间的距离对视觉测量系统精度的影响.利用该系统测量消防通道桥梁的跨中挠度,结果表明,视觉测量系统具备非接触、低成本和便于实施远距离测量等优势,可实现以毫米级精度进行结构位移测量.该测量方法在工程结构变形测量中具有较好的应用前景.

Non-contact Structural Displacement Measurement Based on Digital Image Correlation Method

This paper presents a structural sub-pixel displacement measurement by using the digital image correlation technologies for structural displacement and deflection measurement. Pixel-based displacements of a monitored structural location were determined using an improved sub-pixel algorithm. To transform pixel-based displacements to engineering units, a camera calibration method was developed. The numerical simulation test was carried out based on digital image processing algorithm. The simulation results were in good agreement with theoretical value, which validated the reliability of systematic measurement accuracy. A machine vision-based displacement measurement system was developed. A steel frame model was established for conducting experiments to investigate the follows: (i) comparison study on the measurement results obtained by the vision-based system and the laser displacement sensor, (ii) the effect of the measurement distance on the accuracy of the vision-based system. The mid-span deflection of fire-fighting bridge was measured by the developed system. The experimental results show many advantages of vision-based method such as non-contact, low-cost and convenient to implementation in realizing the structural displacement measurement with the accuracy level of millimeter. The method has wide application prospects in the deformation detection of bridges and other structures.