Eccentric-Tube Robot (ETR) Modeling and Validation

Abstract

This paper introduces a snake-like continuum robot design intended for minimally invasive surgery (MIS) in which a robotic sheath is designed to control an end effector with enhanced dexterity. The structure of the eccentric tube robot (ETR) is a development and extension of the current concentric tube robot (CTR) design. By introducing a non-extensible outer sheath, three pre-curved superelastic nitinol (NiTi) tubes are held together eccentrically inside the sheath. The articulation of the ETR is achieved by rotating the individual tubes at their proximal ends, and the curvatures interact to determine the robot's final shape. A kinematic model based on Cosserat rod theory is derived considering the eccentric arrangement and the geometrical constraint imposed by the outer sheath. The kinematic model is validated through simulations and experiments for a single-stage ETR. Experimental results show that, in the worst case, the mean tip error corresponds to 5% of the length of the sheath.