一种并联机构结构误差识别与修正的新算法

为了提高并联机床的运动精度，针对简化误差源模型（含42个误差量），基于并联机构位置正解的快速算法提出了一种结构误差识别的新算法．首先按理论并联机构设计参数，将一球杆仪的两个球铰分别固定在保持平行的动、静平台上，令球杆仪在动平台上的球铰中心相对于静平台上的球铰中心做球面螺旋线运动．然后在此前提下根据球杆仪球杆理论计算长度与实际长度之差构造m维矢量空间，依次让每一个待识别的结构参数有一个单位增量，重点修正与实测误差相关程度最高的结构参数．并通过从测量误差向量中分离出主修正向量后的残余误差向量方法提高修正效率．经过若干轮修正，直到使修正后球杆理论计算长度与实际长度基本一致，即可认为各项误差已修正完毕．该算法只需测量球杆的长度值，大大减少了测量工作量及由此而引入的误差源．

A New Kind of Algorithm on Parallel Mechanism Structural Errors Detection and Modification

In order to improve the kinematics accuracy of parallel machine tool and to simplify error resource model(including 42 errors),a new kind of algorithm on parallel mechanism structural errors reorganization is proposed in this paper based on the fast algorithm of parallel mechanism forward displacement analysis.Firstly,the parallel mechanism parameters are designed by theory,and the two spherical hinges of cue instrument on the mobile and base platform are fixed up separately.Under the condition that the mobile platform parallels the base platform,the center of spherical hinge of the cue instrument on the mobile platform are moving along a spherical helix corresponding to the center of spherical hinge on the base platform.An m-dimension vector space is constructed in terms of the differences between theory calculation lengths and actual lengths of the cue.Each pending detection parameter has a unit increment in turn,and the construct parameter is modified,which has the highest correlation degree with the measured error at first.The modification efficiency is improved by getting the residual error vector of the major modification vector separated from the measured error vector.Finally,after some annulus modifications,all items errors have been modified until the theory calculation length of the cue after modification is consistent with the actual length by and large.The cue length is only need to be measured in this algorithm;therefore,the measurement workload and the error resource introduced by them are largely reduced.