Pre-Programmable Directional Stiffness in Continuum Robotic Arms: Effects of Truss Configurations

This paper investigates the implementation of trussed designs in modular tendon-driven continuum arms (CAs) to address stiffness and stability limitations while maintaining adaptability. Various truss configurations-Single-Level, Combined-Level, and Alternated trusses-were analyzed using Finite Element Analysis (FEA) to evaluate their impact on flexural and axial stiffness under realistic loading conditions. Results demonstrate that truss placement significantly influences performance, with bottom-level trusses improving flexural stiffness by up to 33 %, middle-level trusses enhancing axial stiffness by 43%. Further, Combined-Level configurations provide superior overall stiffness, with Middle-Bottom trusses achieving a 66.5% improvement in flexural stiffness and a 70.9% increase in axial stiffness, while fully trussed configurations maximize rigidity with an 87.8% increase in flexural stiffness and 98.5% in axial stiffness. Alternated configurations achieve anisotropic stiffness for directional control. Additionally, the proposed trussed wing approach enhances stiffness programmability with reduced complexity, eliminating the need for full segment disassembly or tendon re-routing. The proposed trussed CAs enable tailored stiffness and directional control in robotics, medical devices, and aerospace systems.