A Novel Contact-aided Continuum Robotic System: Design, Modeling, and Validation

Tendon-driven continuum robots (TDCRs) are of great promise in dexterous manipulation in long-narrow spaces, such as in-situ maintenance of aero-engines, due to their slender body and compliant hyper-redundant architecture. However, major challenges in implementing this come from mechanical design and morphology estimation: (1) torsion and buckling issues induced by the intrinsic compliant architecture and the coupling of system gravity and distal loads; (2) low-accuracy morphology model influenced by complex load conditions. In this article, inspired by the contact-aided compliant mechanisms (CACMs), a novel continuum robotic system using the bearing-based CACM is developed to overcome the two intrinsic issues (i.e., torsion and buckling) while eliminating the implied wear due to friction at joint/socket interfaces without affecting its stiffness adversely. Subsequently, based on the chained beam constraint model, a comprehensive kinetostatic modeling framework is systematically derived, focusing on mechanism-oriented strategies (i.e., tendon routing friction, physical joint constraint, and section buckling estimation). Finally, various experiments are performed to verify the effectiveness of both our designed hardware and algorithm. It is demonstrated that the robotic system with such hardware and algorithm achieving the torsional stiffness outperforms the twinpivot design at least 24 times, stiffness enhancement > 100 times, morphology error < 2.5% of the manipulator length, and avoiding the first-order instability. Additionally, we demonstrate the navigation experiment by using two developed control strategies to show the performances of the robotic system.