中文摘要：

分析了并联机构的姿态空间，指出了影响姿态空间的因素为物理约束和奇异约束2类．并且分别从这2个方面给出了扩大姿态空间相应的解决方案．以3PRS（Prismatic Revolve Spherical）并联机构为例，提出了采用新的铰链形式和增加冗余UPS（Universal Prismatic Spherical）支链来增大姿态空间的方法，详细描述了动平台能够实现在各个方向90°偏转的机构设计过程，并基于遗传算法以机构整个姿态空间中的灵活度为目标对机构进行了优化，优化的结果通过仿真证实了可靠性，这对于进一步扩大并联机构的应用范围提供参考．

英文摘要：

Orientation space of parallel mechanisms was analyzed. Physical constraints and singular constraints are the two main reasons which restrict the orientation ability of parallel mechanisms. The corresponding solutions from the two aspects were presented. New joints and redundant active UPS （universal prismatic spherical） link were used to enlarge the orientation space of a 3PRS （prismatic revolve spherical） parallel mechanism. The detailed design process of this mechanism with 90° tilting ability was carried out. Genetic algorithm was used to optimize the gross dexterity of the mechanism. Computer simulation showed the effectiveness of these results, which provided references for the wide application of parallel mechanisms.