基于机器视觉的大柔性结构振动位移测量
Machine Vision Based Vibration Displacement Measurement of Large Flexible Structures

针对空间大柔性结构受到扰动后所产生的低频率、大幅值振动变形难以测量的问题，利用基于机器视觉的结构振动位移测量方法对此类结构的振动位移进行了测量，并识别了结构的动态特性。首先，理论分析了传统的对加速度信号直接积分获得位移的方法存在低频噪声被放大的问题并进行了实验论证；然后，研究了基于机器视觉的结构振动位移测量方法，进行了方法精确度与有效性的实验验证。实验中采用数码相机作为视觉传感器，对采集的结构振动视频进行图像处理，采用数字图像相关方法提取每帧图像特征点的位置信息，应用亚像素定位方法改进测量精度。将视觉位移测量方法获得的结构固有频率与加速度数据求得的结构固有频率进行比较，验证了基于机器视觉的振动位移测量方法在大柔性结构振动位移测量和动态特性识别方面的应用有效性。
For space large flexible structures, it is difficult to measure their vibration displacements under disturbances due to low frequency and large amplitude vibration characteristics. In this paper, a machine vision-based vibration displacement measurement method is presented to face this challenge and used to identify structural dynamics properties. First, the problems of low-frequency noise amplifying during the integration of acceleration to obtain displacement are analyzed. Then, the principles of the machine vision-based vibration displacement measurement are introduced. Experiments are performed to verify the accuracy and effectiveness of the method. In those experiments, a commercial digital camera is used as a vision sensor. Digital image correlation method is used to extract pixel displacement of the target points. The sub-pixel positioning technique is applied to improve measurement accuracy. The transformation relationship between physical coordinates and pixel coordinates is built by camera calibration. The vision-based measurement results are compared to the results obtained by linear variable differential transformer. The resulted structural dynamic properties are compared to the results given by acceleration measurements. The results show that the vision-based method can capture the primary dynamic properties of large flexible structures and give more accurate measurement results of vibration displacements.