A Novel Robot Platform With Decoupled Stiffness Control for Endoscopic Surgery

Abstract

Endoscopic robot has garnered significant attention for its ability to offer auxiliary traction and precise maneuverability. However, the low stiffness of its insertion tube makes it susceptible to deformation, which poses great challenges for precise control. Existing variable stiffness technologies have limitations in the maintenance of torsional stiffness and platform size. To address these issues, this work presents a robot platform with decoupled stiffness control for endoscopic surgery. The novel toothed disks are designed to ensure that variation of bending stiffness does not affect torsional motion. An effective cross-sectional ratio is proposed to evaluate the compactness of variable stiffness mechanisms, which is set to 67.16% for the proposed design. With the compact design, the robot platform efficiently integrates a variable stiffness mechanism and multiple functional channels within a diameter of 10 mm. A drive model for the variable stiffness insertion tube is established, and tests are conducted to evaluate the stiffness variation performance. According to the test results, the bending stiffness of the proposed insertion tube can achieve a variation of 15.11 times (227.69–3439.47 N<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\cdot$</tex-math></inline-formula>cm<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${^{2}}$</tex-math></inline-formula>), the variation in bending stiffness does not affect the torque and angle transmission efficiency, and the angle transmission performance surpasses that of the commercial insertion tube. Moreover, an in-vivo animal trial is conducted and 126 mm<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${^{2}}$</tex-math></inline-formula> of mucosal tissue is successfully resected, which verifies the potential application of the variable stiffness insertion tube and robot platform in endoscopic surgery.