Mechanistic Analysis of Cable Tension Effects on the Stiffness of Cable-Driven Serpentine Manipulators

Abstract

This paper presents a mechanistic analysis of stiffness in cable-driven serpentine manipulators (CDSMs), incorporating both cable tension and cable stiffness. First, we derive an analytical stiffness model based on robot statics, identifying cable tension and stiffness as the dominant factors governing robot stiffness at a given configuration. Crucially, we characterize a previously overlooked tension-stiffness coupling effect: cable tension induces nonlinear stiffness variations in driving cables, significantly altering overall robot stiffness. Due to this interdependence, quantifying cable tension’s specific influence on stiffness remains a challenging research gap. To address this, simulations and experiments validate the model and quantify their coupled effects on robotic stiffness. Results demonstrate that for CDSMs using multi-strand cables with nonlinear stiffness, robot stiffness increases sharply with rising tension. Conversely, when cable elasticity is constant, robot stiffness decreases with increasing tension. These findings provide critical insights for advancing stiffness control accuracy in CDSMs.