Static Analysis and Modeling of a Trunk-Like Robot Capable of Adjustable Multi-Turn Helical Deformation

Current trunk-like continuum robots face limitations in actuator capabilities, hindering the realization of adjustable multi-turn helical deformations. In our previous research [1], [2], we proposed the Twisted String and Spiral Hose (TSSH) mechanism, which utilizes both the tensile and torsional forces of twisted string actuators (TSAs) to generate helical deformations. However, the deformation principles of the TSSH mechanism remain not fully understood, motivating further investigation. The main contribution of this study is the analysis of TSSH deformation principles using a conventional mathematical model of twisted strings, supported by experimental validation. Building on this analysis, we developed a static simulation model based on potential energy minimization to predict TSSH deformation. The proposed model provides insights into the deformation behavior of the TSSH mechanism, enabling parameter optimization for enhanced performance. Furthermore, this static analysis can be extended to other TSA-based and tendon-driven systems, providing a valuable reference for string-actuated robotic mechanisms.