Optimal Design of Compliant Joint and Gripper for Miniature Robotic Devices: Application to Surgery

Abstract

In this paper, we present the different steps towards the development of miniature compliant bending joint and gripper with high mechanical performances. These low encumbrance structures (5 mm cross-section) should deliver, with few actuation force, a large output displacement (90° bending, and 60° jaws opening respectively) under large output loads. Firstly, we describe the theoretical studies that have been investigated in order to optimally dimension these structures. For the bending joint, the design has been inspired from the literature and optimized. For the gripper, a non-intuitive design has been generated using a multi-objective optimal synthesis method. Finally, these compliant structures have been prototyped, and characterized. As an applicative example, they have been integrated into the end-effector of a surgical instrument. Despite the limited output load performances obtained (12.5 mN.m output torque with a 2.1 N actuation force, and 0.2 N gripping force respectively), these new building blocks demonstrate the ability of millimeter-size robotic devices further miniaturization.