中文摘要：

以具有3平动1转动的4自由度UPU机构为研究对象，分析了机构对影响其自由度特性及运动误差的各类扭角误差的敏感程度。首先，建立了机构的运动学模型，给出了可能发生的各类误差分类。以给定一定概率分布的数值误差为条件，应用数值方法对位姿正解进行了两种情况的计算和分析，即计算和分析了在误差不变的情况下机构末端操作器的位姿误差随时间的变化，以及扭角误差按照一定概率分布的前提下机构末端操作器在某一运动瞬时的位姿误差。通过分析和对比得到的数值结果和模拟图形，得出了各类扭角误差对机构运动平台影响的不同结果，按照其敏感程度，给出了源误差的大小。

英文摘要：

This paper takes a 4 DOF UPU parallel manipulator possessing the function of 3 translational and 1 revolute （3TI R） motion as a studying object to analyze parallel manipulators＇ sensitivity to various kinds of twist angle er- rors that have an impact on manipulators＇ DOF characteristics and kinematic errors. A kinematic model for manip- ulators is established and typical twist angle errors are enumerated. Based on the model and particular probability distribution, forward solution is solved and discussed in two eases by the numerical method. Firstly, the position and orientation error of the end effector changing with time is presented when error is fixed. Secondly, by using the probability distribution theory, the influence of error sources amplitude on the position and orientation error of ma- nipulators in the particular time is assessed. With analyzing and comparing the numerical results and simulation il- lustrations, status of different twist angle errors acting on the moving platform are obtained. The error sources are estimated according to the sensitivity.