6PUS并联机构的运动学整机标定

首先建立了6PUS并联机构包括虎克铰铰链点、球铰铰链点、杆长以及导轨方向向量在内的54结构参数的误差雅可比矩阵。在MATLAB中使用最小二乘法建立了其标定模型,通过仿真验证了雅可比矩阵的正确性和最小二乘法参数辨识的有效性。其次采用正交试验选取位姿,用激光跟踪仪进行整机标定实验。根据标定结果,在MATLAB中采用建立的标定模型进行参数辨识,得到54结构参数。最后进行误差补偿,观察标定补偿效果。该整机标定可使单方向最大位置误差在0.030 mm,最大姿态误差在0.0007 rad;三方向最大位置误差在0.046 mm,最大姿态误差在0.0008 rad。由标定效果可知,整机标定可明显地提高运动学精度。

Integral kinematic calibration of 6PUS parallel mechanism

Firstly, the error Jacobi matrix of 54 parameters including the centers of U-joints and S-joints, the length of each link and the guide's position vectors was derived for the target 6PUS parallel mechanism. And the calibration model was established based on least squares method in MATLAB. The correctness of Jacobi matrix and the validity of the identification method using least squares method can be proved with MATLAB simulation. Secondly, the poses were selected based on orthogonal experiment and the integral mechanism calibration experiment was carried out by a laser tracker. The 54 parameter data were obtained through parameter identification using calibration model in MATLAB based on the calibrated results. Finally, the calibrated consequence can be obtained through error compensation. The results show that after compensation, in one direction, the maximum position error of the target mechanism is 0.030 mm and the maximum angle error is 0.0007 rad, while in three directions, the maximum position error of the target mechanism is 0.046 mm and the maximum angle error is 0.0008 rad. Therefore, we did a significant improvement in kinematic precision by integral mechanism calibration.