中文摘要：

作为轴对称矢量喷管转向控制驱动机构的Gough—Stewart类并联机构，主要工作在奇异位置状态。在该位置，驱动平台能够获得一个绕其法线的自由转动，导致转向控制驱动机构的运动具有不确定性。为此，采用少自由度3SPS-3PRS并联机构限制该自由转动，通过对少自由度3SPS-3PRS并联机构的分岔特性研究发现．该并联机构存在尺度极限奇异位置，且输入参数的取值对由尺度极限奇异位置决定的并联机构的工作空间影响较大。对于给定的矢量状态要求，3SPS-3PRS并联机构的输入参数变化范围有可能超出由尺度极限奇异位置确定的工作空间．导致3PRS运动链产生较大的约束内应力，同时并联机构的工作空间跨越奇异位置使得动平台在通过奇异位置后的构型具有不确定性，因此该并联机构的运动奇异性问题依然存在.

英文摘要：

The Gough-Stewart parallel mechanism is chosen as the driving mechanism for the axisymmetrical vectoring exhaust nozzle （AVEN）. However, this manipulator works at its singular position normally and obtains one degree-of-freedom rotation about the axis of the AVEN. In order to restrict this obtained freedom, the 3SPS-3PRS constraint kinematic chains are introduced. Through the configuration bifurcation characteristics investigation of the 3SPS-3PRS parallel manipulator, it is found that the singular points still exist in the 3SPS-3PRS parallel manipulator and the singular-free workspace of the manipulator is restricted by singular points. For the given vectoring requirements of the AVEN, the lengths of the input parameters can possibly overstep the singular-free workspace determined by the singular points, and lead a huge inner constraint force in 3PRS kinematic chains to be produced, as well as the motion of the top platform uncertainty while the manipulator passes through the singular points. Therefore, the singularities of the parallel manipulator still exist.