运动副间隙引起的并联机器人误差及其补偿

Error and compensation of parallel robot with joint clearances

针对运动副间隙引起的并联机器人定位误差,提出了通过优化驱动杆的关节角位移参数来补偿运动副间隙误差的方法。以平面3-RRR并联机器人系统为研究对象,建立运动副误差模型,研究了间隙误差引起的杆件实际长度误差和驱动杆实际关节角位移误差的变化规律。根据机器人的逆运动学方程,建立了基于全微分理论的机构误差分析模型。应用粒子群优化(PSO)算法优化驱动杆的关节角位移参数,补偿了运动副间隙引起的系统结构误差。引入线性递减惯性权重和压缩因子对标准PSO算法进行改进,给出了算法的统一表达式。误差补偿结果显示,改进PSO算法能够有效提高优化算法的收敛性能,使用优化后的关节角位移参数得到的机器人末端轨迹误差值比未补偿轨迹降低了99%以上。仿真实验结果显示本文方法能够有效补偿运动副间隙引起的系统结构误差,保证并联机器人系统的定位精度。

To reduce the position error of a parallel robot caused by joint clearances,a method to compensate the joint clearance errors was proposed by optimizing the joint angular displacement parameters of drivers.For the purpose of a planar 3-RRR parallel robot system,an error model of the joint was presented and the change rules of the errors of actual lengths of links and actual joint angular displacements of drivers caused by joint clearances were obtained.According to the inverse kinematics equation,the error analysis model of system was proposed by total derivative theory.The structural errors of system caused by joint clearance errors were compensated by optimizing the joint angular displacements of drivers using Particle Swarm Optimization（PSO）algorithm.By inducing the linear decreasing weight and the compression factor,the standard PSO algorithm was improved,and an unified expression of algorithms was derived.The results of error compensation show that the improved PSO algorithm is effective for improving the convergence performance.The trajectory errors of end-effecter using optimized joint angular displacements are decreased by 99% as compared with that of uncompensated trajectory.Obtained results demonstrate that the proposed method effectively compensates the structural errors caused by joint clearances and guarantees the position accuracy ofparallel robot systems.