Study of Effect of Cable Yielding in Cable-Driven Robotic System

A methodology was developed herein to characterize the performance limitations imposed by the yielding of the cables in a planar robotic mechanism with a cable-driven transmission. The planar robotic mechanism was first presented and the kinematic coupling between links due to the cable-drives was investigated. This method involved a model of the cable tensions based on a rigid-body model of the system, where the tensions are considered as reaction forces. The model allowed for analysis of the tensions in a manner similar to that of a recently developed characterization called the Dynamic Capability Hypersurface. In effect the limitations on dynamic performance caused by cable yielding were added to the limitations caused by the bounds on actuator torque capacity, in order to give a more comprehensive description of the capabilities of the cable-driven system. A two degree-of-freedom mechanism was analyzed in order to illustrate the methodology. The effect of pulley radius was also studied.