Workspace and Singularity Analysis of a 3-PRRS Parallel Robot

Abstract

This paper presents in-depth kinematic, work-space and singularity analysis of a six-degree-freedom parallel robot having 3-PRRS structure. The robot has three identical link chains connected together by a triangular moving platform. Each link chain composes of three rigid bodies connected by two actuating revolute joints. These link chains are connected to base with passive prismatic joint and to the moving platform by passive spherical joints. Explicit inverse kinematic solutions are provided and forward kinematic solutions are determined by dialytic elimination technique. Through its special structure, geometrical method for finding three types of workspace (constant orientation, reachable and dexterous) are given. By using Grassmann-Cayley Algebra, planes can be formed geometrically to determine singularity configurations of the robot. The method presented is advantageous as it provides geometrical insight to singularity conditions which help to avoid their occurrence in the design stage.