针对焊接、切割、打磨、抛光等轻型加工需求，提出一种由面对称3-UPU并联机构及3自由度转头组成的6自由度混联机器人，侧重研究其中并联机构刚度的半解析建模与全域快速预估问题。从分析系统的力旋量系和变形协调条件入手，构造出计及所有支链构件及铰链弹性贡献的半解析静刚度模型。通过算例揭示整机静刚度在任务空间中随位形的变化规律，并借助ANSYS有限元分析软件在典型位形验证了所建模型的正确性。

To meet the demanding in modular design of robotized devices for welding, cutting, deburring and polishing, etc, a novel 6-DOF hybrid robot compose of a plane symmetrical 3-UPU parallel mechanism plus a 3-DOF rotating head is presented. With a brief introduction to the architecture of the robot, a semi-analytical stiffness model of the 3-UPU parallel mechanism is formulated by analyzing the wrenches systems imposed by the UPU limbs upon the platform. This leads to the complete formulation of the static and deformation equations, resulting in a comprehensive stiffness model that accounts for the compliances of all limb components and joints. With the aid of this approach, the stiffness of a prototype machine throughout the entire task workspace is evaluated. The computational results are validated by the ANSYS at two typical configurations.