Design and kinematic analysis of a 3-translational-DOF spatial parallel mechanism based on polyhedra

Because of the high rigidity and high load-capacity, the spatial parallel mechanisms (SPMs) which have coupling chains or consist of loop chains in the limbs are attracting more and more interest. In order to obtain such kind of mechanism, a design strategy inspired by the ground structure method for the topology optimization of trusses is proposed in this paper. Based on the strategy, a new three degree-of-freedom (DOF) translational SPM is found. One characteristic of the proposed mechanism is that each limb of the mechanism consists of a passive planar 6R single-loop closed chain (6RSCC). Then the kinematics is analyzed in detail, including kinematic modeling, Jacobian analysis, singularity analysis, isotropy configuration analysis and workspace analysis. The analysis results further guide the detailed design of the mechanism. Based on the analysis results, a prototype is fabricated to demonstrate the feasibility of the design. At the end of the paper, some conclusions are drawn and future works are discussed.