Kinetostatic Modeling and Comparative Dexterity Analysis of Telescoping Continuum Robots With Tendon-Magnetic Coactuation for Retrograde Endoluminal Navigation

In the field of natural orifice transluminal endoscopic surgery, there are tasks including retrograde operations. These tasks require endoscopy manipulators to perform retrograde motion in narrow human orifices, along with sufficient compliance to minimize the risk of unintended tissue injury. Aiming for them, a tendon-magnetic coactuation concentric robot (TMCR) is proposed. The tendon-driven continuum manipulator provides a steerable, higher stiffness working channel of the magnetic continuum manipulator. In contrast, the magnetic continuum manipulator equipped with several magnets can bend with different curvature distributions. By combining two manipulators with different approaches of actuation, the proposed TMCR attains greater flexibility and reduces its unreachable workspace. Then, the kinetostatic model considering the gravity influence is established for the first time. The comparison between the motion performance of the TMCR with the current concentric mechanisms is conducted. Results indicate that the TMCR reduces the unreachable cavity (the reachable to unreachable area ratio increases by 71.64$\%$). In addition, the experiment results show that the modeling error of the inner magnetic manipulator is less than 4$\%$and the 3-D path tracking error of the TMCR is less than 1.1 mm. Finally, a phantom experiment demonstrates that the TMCR can finish different insertion tasks.