Design and Compensation Control of Modular Variable Stiffness Continuum Manipulator for Nasal Surgery

Rigid instruments with limited flexibility utilized in the traditional endoscopic sinus surgery maybe damage the tissue when surgeon operates in the narrow space of nose specific area. Flexible continuum manipulator would solve this issue. However, current manipulators may not be able to address the intricate and varied surgical demands effectively, and they may not meet the surgical requirements adequately in terms of the flexibility, precision, and stiffness. This article introduced a novel modular continuum manipulator designed to offer exceptional adaptability, precision, and adjustable stiffness. The various sizes of the manipulators could be optimized according to different surgical scenario while taking its flexibility into account. Moreover, the model-based estimation and feedforward compensation control were applied to enhance its precision, taking into account the coupling effect of two sections and friction loss. Additionally, this study introduced a theoretical analysis on the feasibility of implementing variable stiffness for the manipulator, and the coupling was also lessened via increasing the stiffness of the first section. The experiments demonstrated that the maximum average deviation observed was 3.43 mm, which is equivalent to just 2.5% of the total length of the manipulator. Furthermore, the stiffness could be enhanced by up to 75%. Therefore, the proposed flexible manipulator has a potential for the nasal minimally invasive surgery.