一种新型运动副及其在并联机床上的应用

提出了一种基于新型运动副——复合球铰的虚拟轴机床，它是由5-SPS分支组成的并联机构，其中3个分支汇交于一个三重球铰，另2个分支汇交于一个二重球铰，两个球铰固接在一起形成一个复合球铰，代替了并联机构的活动平台，而且机床主轴位于复合球铰中心线上。这种基于复合球铰的5个分支新型虚拟轴机床与基于Stewart平台机构的6个分支的虚拟轴机床相比具有同样多的实用自由度，并且机床结构简单、解耦，其正反解计算及控制亦相对简单。探讨了5分支机床的结构形式，尤其对关键结构——复合球铰的结构，机构位置反解，以及一定姿态下的可达工作空间进行了分析和计算。这种新型虚拟轴机床在空间曲面加工领域将有着广泛的应用前景。

NOVEL COMPOUND-SPHERE-JOINT AND ITS APPLICATION IN PARALLEL MACHINE TOOL

A novel parallel machine-tool mechanism based on the compound-sphere-joint is presented. The parallel machine tool consists of a moving spindle system and a fix base connected by 5-SPS serial chains. The moving spindle system is made up of two compound-sphere-joints, one of them is a three-layer sphere-joint connecting three SPS serial chains; the other is a two-layer sphere-joint connecting two SPS serial chains. The two-sphere-joints spindle system replaces the general moving platform and the main axis of the parallel machine tool is collinear with the centerline of two sphere-joints. Compared with Stewart platform, the novel 5-SPS parallel machine tool has the same necessary degree-of-freedom, and its structure will be simple and has decoupling of the position and orientation. In addition, inverse position resolution is convenient, and its control is easier. The novel structure of the parallel machine tool is proposed, and the structure of the compound-sphere-joint is analyzed. Inverse position resolution is obtained. Posing reachable workspace is also analyzed and calculated. The novel parallel mechanism machine tool has a wide prospective outlook in three-dimension surface manufacturing fields.