Authors:
Anas Hijazi
;
Jean-François Brethe
and
Dimitri Lefebvre
Affiliation:
Groupe de Recherche en Electrotechnique et Automatique du Havre (GREAH), Le Havre University, BP540, 76058 Le Havre and France
Keyword(s):
Singularity Analysis, Singular Surfaces, Jacobian Matrix, Redundant Manipulator Arm, XY-Theta Platform, Design and Kinematics.
Related
Ontology
Subjects/Areas/Topics:
Informatics in Control, Automation and Robotics
;
Robot Design, Development and Control
;
Robotics and Automation
Abstract:
In this paper, the singularity analysis of an XY-Theta platform held by a serial redundant manipulator will be illustrated in details. This XY-Theta platform has a patented kinematics designed to keep the final position error below to 2 µm in its 300mm × 300mm workspace (Hijazi et al., 2015). These high performances are obtained due to the combination of three factors: proximity to a singular configuration allowed by a specific choice of the arm lengths to reduce the lever arm lengths, redundant kinematic chain to enlarge the dexterous workspace and a two-step control using mechanical breaks set up on the furthest joints and exteroceptive sensors in the final step. However, if the proximity of singularities is useful for the precision performance, it may also cause some control problems. Consequently, it is crucial to identify the singularity loci and the kinematic constraints they induce. This analysis is done in two cases: when the first joint is considered locked and the robot is
not redundant anymore and when the robot can be controlled using the four joints. In the non-redundant case, the usual singularity surface degenerates into an helix. In the redundant case, singularity surfaces may appear in specific configurations. In both cases, the induced kinematic constraints are analyzed and strategies are proposed to overcome the problems.
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