Development of a continuum manipulator with variable bending length and piecewise stiffness for transoral laryngeal surgery

Continuum manipulators (CMs) show great potential in transoral laryngeal surgery due to their flexibility. However, CMs for transoral surgery face several issues: large size, which reduces practicality; intersegment coupling, which causes undesired deflection; and a lack of versatility that limits their applicability across different patient groups. This work combines a rod-driven proximal segment and a cable-driven distal segment to achieve piecewise stiffness, alleviating the issue of intersegment coupling. A rigid constraint tube is integrated into the proximal segment to diversify its bending behavior. Preliminary experiments are conducted to validate the design concept. The proposed CM has an overall diameter of only 6.5 mm. The proximal segment can achieve a 90° bending with various curvatures. At the working configuration, the coupling error between the proximal segment and the distal segment is less than 1 mm. The effectiveness of the proposed CM is successfully validated using a human model. The proposed continuum manipulator possesses the desirable characteristics of small size, low coupling, and high versatility, indicating its great potentialities for the diagnosis and treatment of laryngeal lesion.