Effect of Actuation Errors on a Purely-Translational Spatial Cable-Driven Parallel Robot

In this paper, we analyze a spatial 3-DoF cable-driven robot with a finite-size end-effector. The robot has 6 cables that define 3 parallelograms, each composed by two cables: thus, the robot cannot rotate, but only perform translational motions. Also, since the two cables in a parallelogram are always kept at the same length, they can be actuated by the same motor, thereby meaning that the 3-DoF cable-suspended robot requires only 3 actuators. The kinematic and dynamic behaviour of such robots was studied in previous works. The property of purely-translational motion depends on a precise control of the extension of the cables. Therefore, in this paper we study how the platform pose changes as some errors of known maximum magnitude are introduced in the cable lengths. Finally, the results from both numerical simulations and tests are presented. The orientation of the platform is shown to be robust to cable extension errors.