大空间运动3-RRRU并联机器人运动学标定与误差分析

并联机器人具有高速、高刚度和大负载等明显优势，被广泛应用到农业和工业领域，但多关节导致该类机器人控制精度不高。针对大空间运动3-RRRU并联机器人的运动学建模和误差标定方法展开了系统、深入研究。综合应用DH法和空间矢量法建立了机器人的运动学模型，在此基础上，借助偏微分理论推导并建立机器人的误差模型；应用激光跟踪仪进行不同轨迹下机器人的空间位置数据采集，对一般遗传算法进行改进，以等步距搜索策略实现主要遗传算子的优化，并通过全局数值寻优获取机器人的误差补偿数据，完成标定和补偿工作。实验表明：基于直线标定方式，补偿后直线轨迹跟踪误差控制在0.14～1.34mm，但不适用于曲线轨迹补偿，其实测补偿后的最大误差高达5.08mm。曲线轨迹标定精度高于直线轨迹标定，补偿后将直线和曲线两种路径下的最大误差分别降低至1.18mm和1.56mm。该标定方法自动化程度高，适用于含有大量关节并联机器人的误差标定工作。

Kinematic Calibration and Error Analysis of 3-RRRU Parallel Robot in Large Overall Motion

Parallel robot is a kind of nonlinear strong coupling system with many branches and joints. It has obvious advantages of high speed, high stiffness and large load. With the number of joints increasing, its control accuracy is generally not high. In order to improve the accuracy of 3-RRRU parallel robot, kinematic modeling and error calibration method were systematically researched. Firstly, the kinematic equation and error model were derived by DH theory and space vector method. On this basis, the error model of the robot was derived and established with the partial differential theory. Secondly, position data were collected by using laser tracker for straight line and curve path. Lastly, genetic algorithm was optimized and used to complete calculation. The experiment result showed that the tracking error was controlled between 0.14mm and 1.34mm based on the linear trajectory calibration, and the maximum error was greatly reduced from 9.36mm to 1.34mm. But this calibration mode was not suitable for curve path compensation. Its maximum error of curve compensation reached 5.08mm. The linear calibration was just suitable for straight path, and its compensation accuracy was also lower than that of curve calibration mode. After compensation, the maximum error of line trajectory and curve trajectory was respectively reduced to 1.18mm and 1.56mm. According to the experimental data, 3-RRRU robot had better accuracy in the central area of workspace. In summary, the proposed method owned high automation and its feasibility of the method was verified by experiments.