On the Design of Cable-Suspended Planar Parallel Robots

In this paper we present a workspace analysis methodology that can be applied for optimal design of cable-suspended planar parallel robots. The significant difference between regular parallel robots and cable-suspended parallel robots is that the cables in cable-suspended robots can only carry tension forces. The workspace of a planar cable robot is characterized as the set of points where a reference point of moving platform can reach with tensions in all suspension cables. In the design of cable-suspended parallel robots, the suspension points of the cables, size and shape of the moving platform are the design variables. The workspace area and global condition index are used as the objective functions to optimize the design parameters. The global condition index is a measure of isotropicity of the manipulator. The design variables are determined for different numbers of cables using both objective functions at a specified orientation and also at different orientations of moving platform. Experimental results to measure the workspace area demonstrate the effectiveness of this method.