并联机构实现舱段对接的位姿测量方法及试验研究

Pose Measurement Method and Experimental Study in the Docking of Cabins by Parallel Mechanism

针对目前串联对接技术的不足,为实现舱段自动对接,研制了一套以激光跟踪仪为测量设备,并联机构为对接机构的舱段对接系统,提出了一种位姿测量及换算方法,旨在为并联机构实现舱段对接提供可靠的调姿运动参数。首先,以特征测量为基础,匹配移动舱段与激光跟踪仪之间的坐标系关系,将移动舱段坐标系作为中间坐标系,分别构造移动舱段与动平台及移动舱段与固定舱段的相对位姿关系方程;因相对位姿关系方程包含测量误差而难以取得解析解,根据相对位姿关系方程分别构造了自定义标量函数,使相对位姿求解问题转化为各标量函数的无约束优化问题,在合理选择初值的条件下,利用单纯型法求解出各标量函数取极小值时的相对位姿参数,并采用位姿传递转换法计算在实现舱段对接时并联机构动平台所需运动的目标位姿;最后,搭建了舱段对接模拟试验平台,并利用上述位姿计算结果成功实现了舱段对接。为了在一定程度上评价对接效果,对接完成时,在两舱段端面上分别选择并测量了3组特征点,特征点集在x方向的坐标绝对偏差均值为2.673 mm,与各销轴倒角略微插入销孔的结果较吻合;特征点集在y、z方向的坐标绝对偏差均值分别为0.120、0.163 mm,与两舱段端面对正,各销孔与销轴基本对齐的结果较吻合;在一定程度上表明了所提出位姿测量方法的有效性及计算结果的正确性。

Aiming at overcoming the shortcomings in the current series docking technology and realizing automatic cabin docking,a cabin docking system was developed and a pose measurement and conversion method was put forward to provide reliable motion parameters for the parallel mechanism to achieve the docking task.Firstly,the coordinate system relation between the movable cabin and the laser tracker was matched through measuring relevant features.The coordinate system of the movable cabin was taken as the intermediate coordinate system,and equations of the relative pose relation between the movable cabin and the mobile platform as well as that between the movable cabin and the fixed cabin were constructed respectively.Because the analytical solutions of the relative pose equations which contain measurement errors,were difficult to obtain,the relative pose equations were constructed into custom scalar functions.Thus the problem of relative pose calculation was transformed into the optimization of each scalar function and the simplex method was used to solve each scalar function to gain the relative pose parameters.The position transfer conversion method was used to calculate the target pose of mobile platform.Finally,a simulation platform for cabin docking test was built,and the docking was successfully realized by using the above pose calculation results.In order to evaluate the docking effect,three groups of feature points on the end faces of the two cabins were measured after docking.The mean absolute deviation of the coordinate of the feature points set in the x-direction was 2.673 mm,which was consistent with the result of the chamfering of pins being slightly inserted into the pin holes.Meanwhile,the mean absolute deviation of the coordinates of the feature points set in the y and z directions were 0.120,0.163 mm respectively,which is consistent with the result that the end faces of two cabins are facing directly and the holes are basically aligned with the pins,and to some extent,showed the validity of the proposed pose measurement method and the correctness of the calculated results.