Design and Performance Analysis of a Cable-Driven Continuum Robotic Joint Module

A Cable-Driven Continuum Robot (CDCR) is composed by several identical Cable-Driven Continuum Robotic Joint Modules (CDCRJMs). In a conventional CDCRJM, all of the driving cables are arranged parallel to each other, which results in a singularity configuration in its initial pose. This paper proposes a modified CDCRJM design through selecting appropriate cable anchorage points in order to avoid the kinematic singularity and improve the stability of the CDCRJM. However, the new CDCRJM design increases the difficulty in its performance analyses. The kinematics analysis, tension analysis and workspace analysis issues are investigated. The displacement analysis is addressed based on a two-variable local Product-of-Exponential (POE) formula, in which an approximation method is proposed for the forward displacement analysis. The Lie bracket theory is introduced for the velocity analysis of the CDCRJM. Moreover, in order to ensure the positive cable tensions, a generic tension analysis method is proposed based on the virtual work principle. Finally, the equi-volumetric partition method is utilized for the workspace analysis of the CDCRJM.