Optimum Design and Stiffness Analysis of a 3-RCU Parallel Manipulator * .

Large tilt angle is required for parallel manipulators in many applications, this is a challenging issue in the field. In this paper, the optimum design of a 3-RCU parallel manipulator with 1T2R DoFs is carried out to realize the performance of large tilt angle output. The parameter-finiteness normalization method is used to build the parameter design space, and the motion/force transmission and constraint performance indices are used as the evaluation criterion. On these bases, the performance charts have been generated. Taking the constraint condition of achieving 45° tilt angle in all directions into consideration, an optimum region in the parameter design space has been derived and a group of optimized parameters is obtained. According to the results of optimum design, an CAD model of the manipulator is built. Based on perturbation method and principle of virtual work, a stiffness analytical model is established. Finally, the stiffness has been investigated, and the accuracy of the stiffness analytical model has been verified by comparing with the stiffness calculation using finite element analysis method. The work in this paper lays the foundation for the development of the manipulator.