基于外部坐标测量的六自由度并联机构标定方法

Calibration of 6DOF Parallel Mechanism Based on External Coordinate Measurement

针对六自由度并联机构校准精度问题,提出了一种基于外部坐标测量的标定方法。利用通用测量设备测量并联机构的位姿信息,构造一个统一度量的残差方程,其构造方式保证了所有几何参数的可辨识性,从而不再需要设计和加工专门用于标定的各种辅助机构和冗余传感器。在此基础上,通过对冗余方程组的优化求解,可以得到并联机构各参数的估计值,并用它们替代理想参数进行反解运算,实现误差补偿。仿真表明,此方法能够抑制测量噪声的影响,发挥并联机构不存在误差累积的特性,标定后并联机构校准精度能够达到测量噪声的量级。最后将此方法应用于实际设备的标定,经过误差补偿后其精度提高了5倍以上。

In order to improve the calibration precision of 6DOF parallel mechanism,a calibration method based on external coordinate measurement is presented.The position and attitude informations of the parallel mechanism are acquired using common measuring devices and the residual equations with uniform measure are constructed.These equations can ensure the identifiability of each geometry parameter＇s,so no special auxiliary calibration equipments or redundant sensors are required.From the residual equations,the estimated values of geometry parameters are obtained by optimization method,and the ideal parameters are replaced by them for the parallel mechanism inverse kinematics calculation of to realize the error compensation.The simulation results show that this method can decrease the effect of measure noise,and the kinematics accuracy after calibration can reach the same order of magnitude as measurement noise since the errors of parallel mechanism＇s are not usually cumulated.The calibration accuracy is improved more than 5 times after error compensation by using the method.