Self-Motions of General 3-RPR Planar Parallel Robots

We study the kinematic geometry of general 3-RPR planar parallel robots with actuated base joints. These robots, while largely overlooked, have simple direct kinematics and large singularity-free workspace. Furthermore, their kinematic geometry is the same as that of a newly developed parallel robot with SCARA-type motions. Starting from the direct and inverse kinematic model, the expressions for the singularity loci of 3-RPR planar parallel robots are determined. Then, the global behavior at all singularities is geometrically described by studying the degeneracy of the direct kinematic model. Special cases of selfmotions are then examined and the degree of freedom gained in such special configurations is kinematically interpreted. Finally, a practical example is discussed and experimental validations performed on an actual robot prototype are presented. KEY WORDS--planar parallel robot, kinematic geometry, singularity, self-motion

• Type: Journal
• Year: 2008
• Where: CORR
• Authors: Sébastien Briot, Ilian A. Bonev, Damien Chablat, Philippe Wenger, Vigen Arakelian
• Keywords: CORR 2008, Education, Kinematic, Kinematic Geometry, Robot