Payload Placement on Board a Cable-Driven Parallel Robot with Workspace Including Tilt

When it comes to planning the operation of a cable-driven parallel robot, the Available Wrench Set (AWS) is a very useful tool, describing conditions for suitable payload positions in the platform frame for a described set of poses. However, this is only applicable when no platform tilt is involved, as tilting has an impact on the wrench components when the payload is not placed at the platform reference center. For the cases where rotations are required, which can be combined with translations, the principle of a support polyhedron, derived from the AWS, is proposed in order for the robot designer to know where a payload should be placed on the platform to ensure static equilibrium at the target pose or set of poses, including tilt. With the AWS being based on a admissible range of cable tensions, an improved model of sagging cable focused on collision avoidance between cables, yielding a minimum cable tension, is also proposed in the paper. These analytical tools are then used to give a comprehensive analysis of the Cogiro robot featuring combined rotations around horizontal axes.