Investigating the effect of cable force on winch winding accuracy for cable-driven parallel robots

This paper focuses on the winch winding properties of typical driving mechanisms of cable-driven parallel robots. While cable properties have already been studied, the accuracy of winding mechanisms to control cable robots and the interaction with cable properties have yet to be investigated. To initiate this, some properties believed to affect the winding accuracy are outlined. It was found that cable force can have a significant effect, generally because of finite stiffness causing ovalisation and elongation effects on the rope. Experimental investigations showed that cable force was the most significant factor contributing to a change in cable length. This effect can change the accuracy of winding mechanisms by 0.3% to 1.2%. The accuracy is not affected by winding speed, and only minimally affected by variable cable forces. This implies that when investigating cable robot accuracy, the winch winding properties cannot be ignored and an accurate winding model will need to take into account different winding states.