On the accuracy of $N-1$ wire-driven parallel robots

A $N-1$ wire-driven parallel robot is a robot for which all the $N \ge 3$ wires are connected at the same point of the platform, allowing to control the location of this point. We are interested in the positioning accuracy of such a robot. If the wires are not elastic we show that the influence on the accuracy of the co-location errors of the wire anchor points on the platform is moderate, although a full analysis is a very difficult task. If the wires are elastic we study the influence of the the wire lengths measurement errors and inaccurate estimation of the stiffness of the wires. Again we show a moderate influence but very large changes in the tensions in the wires that probably prohibit the use of the redundancy to optimize the tension in the wires. In all cases the complexity of the forward kinematics of such a robot makes accuracy analysis a very demanding task that requires an in-depth investigation.