中文摘要：

定义了一种能综合评价不同位形下并联机构灵巧度的指标——平方平均灵巧度系数，分别考察了4-UPS—RPS空间并联机构的定平台和动平台上铰链点的分布角、定平台铰链点分布圆的半径以及动平台铰链点分布圆的半径对平方平均灵巧度系数的影响规律，并据此对这些参数进行优化设计，得到该并联机构定平台铰链点的均布角为π／2，动平台铰链点的均布角为2w／5，定平台上第1个铰链点到定坐标系原点的距离为650mm，定平台上其余4个铰链点分布圆的半径为800mm，动平台上铰链点分布圆的半径为160mm。仿真结果表明，经过优化设计，4-UPS—RPS空间并联机构的平方平均灵巧度系数指标比优化前明显增大，运动学性能得到了较大改善。

英文摘要：

The square mean dexterity coefficient, which is used to comprehensively evaluate the dexterity of various configurations, is introduced. The influence law of the structural parameters, including the distribution position angle of the joints on the stationary platform and moving platform, the distribution position radius of the joints on the stationary platform, and the distribution position radius of the joints on the moving platform, on the square mean dexterity coefficient are discussed. On these grounds, the structural parameters are optimized. The optimal results obtained are as following, the distribution position angle of the joints on the stationary platform is π/2, the distribution position angle of the joints on the moving platform is 2π/5, the distance between the first joint on the stationary platform and the center of the stationary platform is 650 mm, the distribution position radius of the joints on the stationary platform is 800 mm, and the distribution position radius of the joints on the moving platform is 160 mm. The simulation results show that the square mean dexterity coefficient of 4 - UPS - RPS parallel mechanism are creased, so that the obvious improvement of the kinematics characteristics for the parallel mechanism is realized.