ON THE STATIC WORKSPACE OF LARGE DIMENSION CABLE-SUSPENDED ROBOTS WITH NON NEGLIGIBLE CABLE MASS

In most studies on parallel cable-driven robots, cables are supposed to be massless and inextensible. However; in the case of large dimension robots, cable mass and elasticity cannot be neglected anymore. Based on a well-known cable static model which takes these characteristics into account, the formulation of the inverse kinematics of n cable/n-DOF cable-driven robots is presented. The consequences of this modeling on the usual static workspace definition is then discussed. Notably, as the tension in a cable is not constant, the maximal tension along the cable has to be found. An example of a planar 3 cable/3-DOF robot is used to highlight that, in some particular poses, the mobile platform can be in static equilibrium while some cables are hanging below the platform. Finally, new limiting factors for the definition of the static workspace are introduced and applied to the same planar robot example which shows the significance of taking into account cable mass and elasticity.