Experiments on a variable stiffness tensegrity mechanism for an MR-compatible needle holder

Abstract : In this paper, we present the design of a novel MR-compatible needle holder with variable stiffness and a first experimental evaluation of its ability to be controlled in position and stiffness. The device should be able to control both the orientation and the angular stiffness of the needle around the insertion point within the MR-environment. To do so, our design is based on tensegrity mechanisms, a class of prestressed mechanisms that exhibit interesting properties for our context since they are compact, lightweight and remotely controllable. An experimental setup is developed. The position and stiffness control on one degree of freedom is then performed using an open loop control strategy. Encouraging results are finally presented as well as future works to be carried out.