中文摘要：

提出一种具有完全各向同性的3-PPRRR移动并联机构，该机构每个分支由2个移动副和3个转动副组成，其中第一移动副和第二移动副垂直，第一转动副轴线与第三转动副轴线相互平行，第二转动副轴线垂直于第一转动副轴线，3个分支呈正交布置。运用螺旋理论得出如下结论：单个PPRRR分支对动平台施加1个约束力偶，在正交布置条件下，3个分支约束力偶线性无关，约束动平台的3含转动自由度，第一移动副可作为驱动副。根据此自由度特性可证明各个PPRRR分支中第二转动副为消极副，进而简化该机构的运动学分析，得到3-PPRRR并联机构的位置、速度和加速度的正逆解关系以及工作空间，结果表明该机构具有3个完全解耦的移动自由度和完全各向同性。

英文摘要：

A novel 3--PPRRR parallel mechanism with three translational degrees of freedom was presented. The limb chain of the 3--PPRRR parallel mechanism consisted of two prismatic pairs and three revolute pairs. The first prismatic pair was perpendicular to the second prismatic pair. The axis of the first revolute pair was parallel to the third revolute pairs. The axis of the second revolute pair was perpendicular to the first revolute axis. The three limb chains were arranged orthogonally. The constraint analysis of the 3--PPRRR parallel mechanism was performed by using screw theory. It is shown that the three PPRRR limb exerts three independent constraint couples on the moving platform,which restricts three rotational degrees of freedom of the moving platform. The validity of the first prismatic pair being actuated is verified. Further,it is proved that the second revolute pair in each limb is inactive based on the mobility features of the 3--PPRRR parallel mechanism, which simplifies the kinematic analysis of the 3-PPRRR parallel mechanism. The forward and inverse position, velocity and acceleration analysis, and workspace are discussed. The three translational degrees of freedom of the 3--PPRRR parallel mechanism are completely decoupled and the mechanism is fully--isotropic.