A Stiffness-Enhanced Extensible Continuum Surgical Robot: Design, Modeling, and Evaluation

Due to the limited size of natural orifices, continuum surgical robots used for natural orifice surgery must be miniaturized, while maintaining their load capacity. To solve this challenging problem, this article first proposes a bio-inspired extensible variable-section continuum surgical robot based on a compression spring structure to improve its stiffness and load capability. Second, the stiffness advantages of the variable-section continuum surgical robot over the constant-section continuum surgical robot and the slope magnitude’s influences on the stiffness are analyzed. Third, a kinematic model of the proposed variable-section continuum surgical robot is established based on the geometric relationship of the variable-section structure. Stiffness and kinematic verification experiments were conducted to verify the enhanced load capacity of the variable-section continuum robot and to validate the kinematic model. The average stiffness of the variable-section continuum robot is improved by at least 31.5% compared with the constant-section continuum robot. Finally, we demonstrate the motion dexterity of the variable-section continuum robot.