Workspace optimization for a planar cable-suspended direct-driven robot

• We present a large-workspace cable robot (CDPR) with a passive serial manipulator.
• We show that the CDPR can be used as a state-of-the-art Repetitive Workspace Robot.
• We evaluate the tessellation efficiency with a state-of-the-art index IRWRIRWR.
• We use the IRWRIRWR index to design and optimize the CDPR.
• We review the performance of the UECA algorithm to compute the IRWRIRWR.

The present work is inspired by an industrial task, i.e. spray painting a large area by means of a robotic system consisting in a Cable-Driven Parallel Robot (CDPR). In many cases, the area of the robot workspace is smaller than the area to be painted. For this reason, the base of the robot has to be shifted several times during the painting process. These robots are referred to as Repetitive Workspace Robots (RWR). In other words, in order to accomplish the whole task, they need to be moved after they have completed a sub-task locally. A cable suspended CDPR is an ideal candidate for such tasks; it can be thin, light, flexible and cost-efficient.The question is: which is the best shape of the local workspace in these conditions? In fact, not always a larger area of the local workspace guarantees an efficient painting process. This is because the efficiency relies mainly on the shape rather than on the local workspace area itself.In this work we employ an index [Seriani S, Gallina P, Gasparetto A, 2014] to evaluate the efficiency of the workspace of a 2-link CDPR. Finally, we show how the index value changes in relation to some geometrical parameters of the robot, thus laying the foundations for a general design methodology.

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