Analysis and kinematic optimization of planar 2-DOF 5R parallel mechanisms considering the force transmissibility

This paper treats the problems of kinematic analysis and optimization of the 5R symmetrical parallel mechanism taking into account the force transmissibility. In the design process, the theoretical workspace cannot be used practically due to the inside singularity. The usable workspace without singularity inside cannot still be useful in an optimization problem since a mechanism at and near the boundary of the workspace will be out of control. The local conditioning index (LCI), which is widely used in the field of serial robots and has been applied in many optimizations, has the problem of physical significance and difficulty of measuring the distance to a singularity of a parallel mechanism. For such reasons, the concept of transmission angle is introduced in this paper to the optimization of the planar 5R parallel mechanisms. Based on this concept, three new indices are proposed. After presenting the performance charts, the optimization process of the mechanisms is finally presented by considering the workspace and force transmissibility.