In this paper, a novel composite 6-DOF parallel robot is introduced. Two independent components are included in this new mechanism. One is a planar 3-RPR mechanism, the other is a spatial 3-UPS-l-PU mechanism. The planar mechanism provides translations along the x and y axes and rotation around the z axis. As a complement, the 3-UPS-l-PU mechanism provides translation along the z axis and rotations around the x and y axis. These two mechanisms are combined using a serial connection. Different combinations of these two mechanism are proposed in this paper.

While a number of researchers have published results in the area of parallel robot singularity determination and the a posteriori elimination of these singularities, far less work has been published in the area of singularity free workspace design. Several researchers have committed substantial funds to design hardware prototypes that have proven worthless because of unavoidable singularities. This trend, if carried over to industrial applications, could prove especially detrimental to the future of applied parallel robotics. A comprehensive and straightforward design strategy that guarantees a singularity free workspace is presented in this paper. The design problem is mathematically modeled, and relaxations are suggested for finding solutions. The translational 3-UPU parallel robot is studied to verify the efficacy of the design approach.

A method to design a singularity-free 3-arm planar parallel mechanism is presented. Parallel mechanism singularities are categorized by their relationship to the design problem. A sequential design procedure is explained, whereby two arms are designed first to satisfy workspace requirements, then the third arm is designed to provide a singularity free workspace. The method is used to develop a singularity-free workspace design for the 3-RPR mechanism.