The Forward Kinematics of the 4-1 Cable-Driven Parallel Robot with Non Elastic Sagging Cables

Abstract

We consider a 3 dof translational cable-driven parallel robot (CDPR) with 4 cables connected at the same point on the load. We assume that the CDPR has a small or medium size and uses synthetic cables so that the elasticity of the cable material is negligible. We will investigate the forward kinematics (FK) of such a CDPR (i.e. determining the CDPR pose for given cable lengths) with the purpose of evaluating the influence of the sagging of the cables and showing that the FK has, in general, a single solution. We then consider other FK problems where only cable tensions or angles are measured and show their advantages and drawbacks. We then consider the FK problem where we fuse the measurements of the cable lengths with direct measurements of the pose of the platform provided at a low rate.