A Novel Continuum Overtube with Improved Triangulation for Flexible Robotic Endoscopy

This paper presents a novel continuum overtube that consists of a notched tendon-driven 2-DOF continuum joint and a distal deployable structure driven by a flexible screw rod. A smooth bending shape with constant curvature is achieved by adopting an overlapped area between notches to generate uniform stress distribution. The distal deployable structure provides an extensive triangulation for bimanual operations. The presented design achieves high flexibility, sufficient loading and anti-twisting capacity, and an improved layout of functional channels for flexible robotic endoscopy. Design optimization is performed to optimize structural parameters for performance investigation and improvement. The proposed continuum joint achieves an average distal positioning error of 1.48% and 1.20% within -115∘, 115∘ in the two bending planes with minor hysteresis errors of less than 1.5%, indicating the outstanding constant bending curvature characteristics for kinematic modeling and control. The loading capacity achieves 4.27N and provides significant advantages in terms of sufficient rigidity over the commercial endoscope. The designed deployable structure has significantly improved operational triangulation, which can effectively support bimanual operations with two instruments for complex operations. Meanwhile, the torsional stiffness of the designed continuum joint reaches a considerable value of 8.73mNm/∘ and provides stable support for instruments during operations. Ex-vivo experiments of gastric tissue biopsy have been performed to verify the feasibility of the presented design in a practical scenario.