图像式无砟轨道路基沉降监测系统中,列车运营过程中受振动等因素影响,靶面和相机的相对偏转会影响光斑中心定位结果的精度。因此,设计了一种监测靶面位姿测量系统,通过靶面位姿解算得到偏转角,实现对光斑中心定位结果的修正。首先,将单目视觉和监测靶面相结合,根据靶面二维特征点之间已知的几何约束关系建立摄像机的透视投影模型;然后,基于P5P问题,使用HOMO算法对靶面位姿进行线性求解,在此基础上通过非线性Levenberg-Marqurdt算法得到位姿优化解。系统可以进行实时的特征点图像处理和位姿解算。搭建了无砟轨道表面沉降监测中靶面位姿测量系统的实验平台,以高精度的三维精密旋转台为基准,将靶面竖直安装在三维精密仪上,通过控制三维精密仪的旋转角度获取靶面位姿测量的数据。实验结果表明:当分别绕X、Y和Z轴转动角度在[-5°,5°]时,位姿测量系统三个方向的均方根误差分别是0.048°,0.052°,0.056°,整个测量过程时间为0.9 s,测量系统的时间和精度均满足图像式无砟轨道路基表面沉降监测系统的测量要求。

In the image type ballastless track subgrade settlement monitoring system, vibration and other factors are affected during the operation of the train. The relative deflection of the target surface and camera affects the accuracy of the spot center positioning results. Therefore, a monitoring target attitude measurement system is designed. The deflection angle is obtained by solving the target pose to achieve correction of the spot center positioning results. First of all, combine monocular vision with monitoring targets, establishing a perspective projection model of the camera according to a known geometric constraint relationship between the two-dimensional feature points of the target surface. Then, based on the P5P question, using the HOMO algorithm to solve the linear pose of the target surface linearly. On this basis, the pose optimization solution is obtained by the nonlinear Levenberg-Marqurdt algorithm. The system can perform real-time feature point image processing and pose calculation. An experimental platform for the target surface attitude measurement system in the surface settlement monitoring of ballastless track is constructed based on a high-precision three-dimensional precision rotary table, and mount the target surface vertically on the three-dimensional precision instrument. The data of the target pose measurement is obtained by controlling the rotation angle of the three-dimensional precision instrument. Experimental results show that when the X, Y, and Z axis are respectively rotated at [-5°, 5°],the root mean square error of the three directions of the pose measurement system is 0.048°, 0.052°, 0.056°, respectively. The entire measurement process time is 0.9 s. The time and accuracy of the measurement system meet the measurement requirements of the image-based ballastless roadbed surface settlement monitoring system.