| Sébastien Briot,
Vigen Arakelian Département de Génie Mécanique et Automatique,
Institut National des Sciences Appliquées (INSA), Rennes, France, Ilian A. Bonev Department of Automated Production Engineering,
École de Technologie Supérieure (ÉTS), Montréal, Canada, Damien Chablat and
Philippe Wenger Institut de Recherche en Communications et Cybernétique de Nantes
1, rue la Noë – BP 92101 44321, Nantes Cedex 3, France |
| 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. |
