A Steerable Cross-Axis Notched Continuum Manipulator for Endobronchial Intervention

Abstract

Achieving the balance between stiffness and range of motion (ROM) in continuum manipulators is a primary design challenge. To tackle this design trade-off, this paper introduces a novel notched-tube continuum manipulator (NTCM) called the Steerable Cross-axis Notched (SCAN) manipulator. It achieves this by integrating asymmetric cross-axis notches into a pair of concentric nitinol tubes. Two pairs of cross-tilted beams are positioned within each segment, thereby extending the length of the flexural members. When compared to traditional NTCM with vertically configured beams (termed as v-NTCM), the SCAN manipulator (SCANM) exhibits a greater maximum bending angle for the same level of bending stiffness. Furthermore, the SCANM exhibits greater bending stiffness in comparison to the v-NTCM with the same maximum bending angle. Subsequently, a mechanical model for the SCANM, accounting for external tip load and tendon friction, is developed. Additionally, a multi-objective optimization is carried out to identify the optimal structural performance. Through model analysis and comparisons, this paper also elucidates the distinct advantages offered by the SCANM. Model verification experiments and stiffness testing experiments are conducted to quantify both the model’s accuracy and stiffness of the SCANM. Finally, an endobronchial grasping and a laser ablation experiment are conducted to demonstrate the practical feasibility of the SCANM for clinical applications.