On the Dynamic Properties and Optimum Control of Parallel Manipulators in the Presence of Singularity

Sébastien Briot (1) , Vigen Arakelian (2)

1 IRCCyN - Institut de Recherche en Communications et en Cybernétique de Nantes
2 DGMA - Département de Génie Mécanique et Automatique

It is known that a parallel manipulator with a singular configuration can gain one or more degrees of freedom and become uncontrollable. That is it might not reproduce a stable motion under a prescribed trajectory. However, it is proved experimentally that there is possible passing through the singular zones. This was simulated and shown on numerical examples and illustrated on several parallel structures. In this paper, we determine the optimal dynamic conditions generating a stable motion inside the singular zones. The obtained results show that the general condition for passing through a singularity can be defined as follows: the end-effector of the parallel manipulator can pass through the singular positions without perturbation of motion if the wrench applied on the end-effector by the legs, and external efforts of the manipulator are orthogonal to the twist along the direction of the uncontrollable motion. This condition is obtained from the inverse dynamics and analytically demonstrated by the study of the Lagrangian of a general parallel manipulator. Numerical simulations are carried out using the software ADAMS and validated by experimental tests.

Mots clés: Index Terms -parallel manipulators; singularity; controllability; dynamics

Domaines: Génie mécanique [physics.class-ph]; Génie mécanique [physics.class-ph]

Sébastien Briot, Vigen Arakelian. On the Dynamic Properties and Optimum Control of Parallel Manipulators in the Presence of Singularity. 2008 IEEE International Conference on Robotics and Automation (ICRA 2008), May 2008, Pasadena, United States. ⟨hal-00451915⟩