Dynamics of Cable Driven Parallel Manipulator Allowing Cable Wrapping over Rigid Link

Abstract

This paper investigates and models the phenomenon of cable wrapping over rigid links in the context of cable driven parallel manipulator (CDPM). The study addresses the cases in which parallel CDPM cables interfere with the rigid links of the manipulator. The outcomes of the study allow the manipulator to utilise the workspace otherwise discounted if cable-body interference was avoided, as well as produce better range of motion about the roll axis of the wrapped rigid link, where appropriate. In this paper, such interference is taken into account and is modelled by allowing the cables to wrap on a single rigid body. The generalised coordinates defined in the body space and in the joint space are studied accordingly. An example was given to demonstrate the approach and the feasibility of using this idea. In the example, given the desired motion of a cable robot, the required cable forces can be solved from an optimization problem. The result is promising and has shown the possibilities to expand the workspace of a cable robot. Nevertheless, the enhanced modelling improves the cable robot by allowing more flexible and compact design in the future application of cable robot such as the mimic glenohumeral joint of a humanoid robot.