Modelling and Analysis of Joint-to-End Variable Stiffness for Cable-Driven Hyper-Redundant Manipulator

To ensure operational accuracy and flexibility in confined environments, the cable-driven hyper-redundant manipulator needs to take into account both compliance and stiffness. Although the cable-driven method enables the manipulator to have adjustable stiffness, the theoretical analyses and studies on the effects of various factors on the stiffness are insufficient, leading to the possibility that the existing variable stiffness strategies may disrupt the equilibrium state of the manipulator. Accordingly, this paper presents the modeling and analysis of joint-to-end variable stiffness for cable-driven hyper-redundant manipulator. First, the multi-layered static models are constructed to decouple and characterise the complex robotic arm system by combining the manipulator kinematics with the virtual work principle. Then, the joint-to-end analytical stiffness models are developed to explore the influencing factors of stiffness, and relevant stiffness indicators are designed to evaluate the stiffness level. Finally, with platform validation and numerical method, the connections between cable tension, joint angle, joint stiffness and end stiffness are analysed, thereby summarising the variable stiffness characteristics of the cable-driven super-redundant manipulator.