Cable-driven parallel robot modelling considering pulley kinematics and cable elasticity

Abstract Cable Driven Parallel Robots (CDPRs) are parallel robots, in which the limbs are replaced by cables that are guided by pulleys. In many papers, the pulleys are considered as fixed points of passage and the cable elasticity is neglected. Those approximations simplify the robot modelling, but lead to some Moving-Platform (MP) pose errors. This paper deals with the modelling of suspended three degree-of-freedom CDPRs considering the geometry and kinematics of the pulleys as well as the cable elasticity. Furthermore, a novel pulley architecture with an universal joint is designed to increase the accuracy of CDPRs and limit the bending moment in the pulleys. Then a sensitivity analysis conducted on these newly established models allows to precisely quantify the effect and interactions of design elasto-geometric parameters on the MP pose. It turns out that the interaction between pulleys geometrical parameters are significant and should be considered in the elasto-geometric static models. Finally, it is shown that a CDPR equipped with the novel pulley architecture helps reducing the overall MP pose error.