Nematode-Inspired Cable Routing Method for Cable Driven Redundant Manipulator*

Cable driven redundant manipulator (CDRM) can provide complex movements with high dexterity and singularity reduction. However, traditional CDRMs with universal joints have the disadvantages of requiring a high number of motors and having a narrow joint workspace. Furthermore, there is a limitation in terms of stiffness and payload. Recently, CDRMs composed of Quaternion joints have been developed to address these disadvantages. They require fewer motors and have larger joint workspace due to the Quaternion joints. Yet, their cable routing method is the same as the traditional CDRMs. In this paper, we propose a novel nematode-inspired cable routing method to achieve complex movements and stiffness increase. To achieve the stiffness increase of CDRM, the proposed cable routing method was inspired by the alternately arranged muscle structure of nematodes. Moreover, moving pulley structure was selected to amplify the stiffness and force of CDRM. An 8-DOF CDRM prototype composed of four Quaternion joints was developed to show the effectiveness of the cable routing method. Kinematics simulation was conducted and then, verified by trajectory through experiments. Finally, a joint stiffness simulation was conducted and verified with the developed prototype by stiffness experiments.