基于最佳偏振角的线性位姿测量方法研究

在基于视觉图像的位姿测量中，非线性位姿测量算法的全局收敛存在不确定性，测量结果取决于初值的选取，不能保证位姿测量的鲁棒性。线性位姿测量算法对图像处理的要求比较高，如果定位特征点图像坐标提取不够精确，会导致位姿测量精度降低。在自然光条件下，相机采集定位特征点图像，图像中高亮度区域的存在对定位特征点提取精度产生影响，进而使有效定位特征点数量减少，影响位姿测量精度。针对上述问题，文中提出了一种基于最佳偏振角的线性位姿测量方法:在相机镜头前加装线偏振片，根据Stokes矢量建立偏振片最佳偏振角度求解模型，在使用最佳偏振角度的前提下采集定位特征点图像，提取图像坐标；建立线性位姿求解模型，计算被测物体位姿。实验结果表明，该方法能够有效减少图像中的高亮度区域，改善成像质量，提高线性位姿测量精度，在?60°~+60°的测量范围内，角度测量误差小于±0.16°，在0~20 mm的测量范围内，位移测量误差小于±0.05 mm。

Research on linear pose measurement method based on optimal polarization angle

As to pose measurement technology based on visual image, the global convergence of the nonlinear algorithm is uncertain, and the results depend on the selection of initial values, so the robustness of pose measurement cannot be guaranteed. Linear pose measurement algorithms have relatively high requirements for image processing. If the image coordinates of feature points are not accurately extracted, the pose measurement accuracy will be reduced. On the condition of natural light, the camera collects the image of positioning feature points, and the existence of high light regions in the image have some impacts on the extraction accuracy of feature points, which reduces the number of effective feature points and affects the pose measurement accuracy. To solve the problems above, a linear pose measurement method based on the optimal polarization angle was proposed. The camera was equipped with a polarizer. The optimal polarization angle solution model was established according to the Stokes vector. On the premise of the optimal polarization angle, the feature points images were collected and the image coordinates of the feature points were extracted. The linear solving model was established to solve the object pose. The experimental results show that this method can effectively reduce the high light regions in the image, which improve the imaging quality and improve the linear pose measurement accuracy. In the measurement range of ?60° to +60°, the angle measurement error is less than ±0.16°. In the measurement range of 0 to 20 mm, the displacement measurement error is less than ±0.05 mm.