R(RPS&RP)&2-UPS并联机构位置精度可靠性建模与分析

Modeling and Analysis of Position Accuracy Reliability of R(RPS&RP)& 2-UPS Parallel Mechanism

为提高并联机构末端位置精度可靠性,确定各误差源对机构末端位置精度可靠性的影响规律,以R(RPS&RP)&2-UPS三自由度并联机构为对象开展位置精度可靠性建模与分析,该机构由一条串接一转动副的1T1R平面并联运动链和两条空间无约束主动支链组成,具有与著名Tricept机器人中UP&3-UPS并联机构相同的运动模式。建立考虑基本尺寸误差、杆长误差及关节间隙的位置精度模型,进而分别利用四阶矩法和蒙特卡洛法提出机构位置精度可靠性计算模型,算例表明采用四阶矩法计算可靠性与采用蒙特卡洛法结果很接近,但可大幅降低计算量。利用四阶矩法研究各误差源对机构位置精度可靠性的影响规律,结果表明杆长误差、关节间隙和方位是影响机构末端位置精度可靠性的关键因素,为R(RPS&RP)&2-UPS机构的制造和装配误差合理制定提供参考。

In order to improve the end position accuracy reliability of the parallel mechanism and to determine the influence law of each error source on the end position accuracy reliability of the mechanism,a three-degree-of-freedom R(RPSRP)2-UPS parallel mechanism is used to model and analyse the position accuracy reliability.The mechanism is consisted of a 1T1R planar parallel kinematic chain with one rotating sub in series and two spatial unconstrained active branch chains,and has the same motion pattern as the UP3-UPS parallel mechanism in the famous Tricept robot.A position accuracy model considering the basic dimensional error,rod length error and joint clearance is developed,and then the reliability calculation model of position accuracy of the mechanism is proposed by using the fourth-order moment method and the Monte Carlo method respectively.An example shows that the reliability calculation results of the fourth-order moment method is very close to that of the Monte Carlo method,but the calculation cost can be greatly reduced.The fourth-order moment method is used to study the influence of each error source on the positional accuracy reliability of the mechanism.The results show that the rod length error,joint clearance and orientation are the key factors affecting the position accuracy reliability,providing a reference for the rational determination of the manufacturing and assembly errors of the R(RPSRP)2-UPS mechanism.