中文摘要：

[PP]S类并联机构包括3-PRS、3-RPS、3-RRS和3-PPS四种构型,可实现1移动自由度和2转动自由度,具有广泛的应用前景。伴随运动是[PP]S类并联机构动平台在非独立自由度上发生的运动,是影响[PP]S类并联机构实际应用的关键问题。建立一般3-PRS并联机构伴随运动运动学模型,揭示出一般3-PRS并联机构各项几何结构参数与伴随运动的内在联系,证明3-PRS并联机构无伴随运动所必须满足的结构充要条件,根据这一结构条件可构建无伴随运动的3-PRS并联机构。指出无伴随运动的3-PRS并联机构中存在的局部自由度,给出考虑这一局部自由度的驱动选取方案,对无伴随运动的3-PRS并联机构进行自由度分析,并确定该类机构的2转动自由度的连续转轴。这一结构充要条件适用于全部[PP]S类并联机构。

英文摘要：

The family of [PP]S parallel mechanism consists of 3-PRS, 3-RPS, 3-RRS and 3-PPS parallel mechanisms, which can undergo one translational degree of freedom （DOF） and two rotational DOFs, and thus, has great potential in practical application. Parasitic motion is the motion occurring in the non-independent DOFs of a [PP]S parallel mechanism, which is a key issue affecting its application. The kinematic model of the parasitic motion of the general 3-PRS parallel mechanism is established, revealing the inherent link between the geometrical structural parameters and the parasitic motion. The sufficient and necessary structural condition for a 3-PRS parallel mechanism without parasitic motion is proved. Based on the structural condition, the 3-PRS parallel mechanism without parasitic motion can be constructed. Local mobility in the 3-PRS parallel mechanism without parasitic motion is identified. Actuation selection considering the local mobility is presented. Mobility analysis of the 3-PRS parallel mechanism without parasitic motion is performed and the two finite rotational axes of the moving platform are identified. The sufficient and necessary structural condition is applicable to all [PP]S parallel mechanisms.