基于双目结构光视觉的煤流量测量研究

Research on coal flow measurement based on binocular structured light vision

在常规的双目视觉系统中,常用的加速稳健特征和尺度不变特征转换匹配算法对图像质量要求高,针对煤炭这种颜色纹理比较单一的场景应用时容易失效,且需要消耗大量的计算资源,难以保证实时性;激光雷达在进行煤流量测量时,有效视场范围较小,对应的测量点数较少,扫描频率也较低,在带式输送机运行速度较快时,精度会大幅降低。针对上述问题,提出一种基于双目结构光视觉的煤流量测量方法,将线结构光引入双目视觉系统,利用线结构光的约束,将图像特征点匹配简化成左右2幅图像行之间的匹配。在保证双目系统相机光轴平行度的基础上,采用对应行匹配计算三维坐标点,提高采样频率和分辨率,进而提高煤流量测量精度,降低测量系统对光照和环境的依赖。点云获取:利用线结构光凸显煤料截面曲线,提取煤料截面中心线的图像坐标,利用双目相机获取左右煤料截面线结构光图像,建立双目结构光三维重建模型,左右图像中心线坐标构成匹配点对参与计算煤料截面三维坐标,实现点云的实时获取。煤流量计算:利用空载胶带截面点云和负载胶带截面点云,结合获取煤料点云,利用微元法对煤料三维点云进行采样,分别利用均匀网格化法和三角网格化法求取单位时间内的煤料体积,实现带式输送机煤流量测量。实验结果表明,利用均匀网格化法检测煤料体积平均相对误差为6.758%,利用三角网格化法检测煤料体积平均相对误差为2.791%,三角网格化法测量精度高于均匀网格化法。工业性试验结果表明,基于双目结构光视觉的煤流量测量方法与电子胶带秤相比,绝对误差最大值为87.855 t/h,绝对误差平均值为25.902 t/h,相对误差最大值为2.876%,平均相对误差为0.847%,满足煤矿非接触式煤流量测量使用要求。

In the conventional binocular vision system,the commonly used speeded up robust features and scale-invariant feature transform matching algorithms have high requirements for image quality.When applied to scenes with relatively single color and texture such as coal,it is prone to failure.It needs to consume a lot of computing resources,which is difficult to ensure real-time performance.When using LiDAR for coal quantity measurement,the effective field of view is relatively small.The corresponding measurement points are few and the scanning frequency is low.When the belt conveyor runs at a faster speed,the precision will be significantly reduced.In order to solve the above problems,a coal flow measurement method based on binocular structured light vision is proposed.The linear structured light is introduced into the binocular vision system.By using the right image lines.On the basis of ensuring the parallelism of the optical axis of the binocular system camera,corresponding row matching is used to calculate three-dimensional coordinate points.The sampling frequency and resolution is improved.The precision of coal flow measurement is improved.The dependence of the measurement system on lighting and environment is reduced.Point cloud acquisition:It uses the line structured light to highlight the coal material section curve,and extracts the image coordinates of the coal material section center line.It uses the binocular camera to obtain the left and right coal material section line structured light images.It establishes binocular structured light 3D reconstruction model.The left and right image center line coordinates form a matching point pair to participate in the calculation of the coal material section 3D coordinates,so as to achieve real-time acquisition of point clouds.Coal flow calculation:The point cloud of coal material is obtained by combining the point cloud of no-load belt section and the point cloud of loaded belt section.The infinitesimal method is used to sample the 3D point cloud of coal material.The volume of coal material in unit time is calculated by the uniform meshing method and the triangle meshing method,respectively.The coal flow measurement of belt conveyor is realized.The experimental results show that the average relative error of coal volume measured by the uniform meshing method is 6.758%.The average relative error of coal volume measured by the triangle meshing method is 2.791%.The measurement precision of the triangle meshing method is higher than that of the uniform meshing method.The industrial test results show that compared with the electronic belt weigher,the maximum absolute error of the coal flow measurement method based on binocular structured light vision is 87.855 t/h.The average absolute error is 25.902 t/h,the maximum relative error is 2.876%,and the average relative error is 0.847%.The results meet the requirements of non-contact coal flow measurement in coal mines.