Résumé
This paper introduces a new two-degree-of- freedom parallel manipulator producing two translations in the vertical plane. The classical drawback of the existing robots built to realize those dof is their lack of rigidity along the transversal axis. Indeed, these architectures cannot be lightweight and stiff at the same time. The proposed architecture is a spatial mechanism which guarantees a good stiffness along the transversal axis. This parallel architecture is composed by two actuated kinematic chains, and two passive chains built in the transversal plane. The key feature of this robot comes from those passive chains which are linked to the frame using coupled revolute joints. This coupling system guarantees the functioning of the robot by constraining the platform to stay in one plane. The stiffness analysis presented in this paper shows that the robot can be lighter and stiffer than a classical 2 dof mechanism. A prototype of this robot has been built and the preliminary tests show that accelerations of 23 g can be achieved while keeping a low tracking error.