Comparison of actuation schemes for wire-driven parallel robots

There are two main systems that can be used to coil and uncoil the wires of a wire-driven parallel robots: a rotary motor that turns a drum on which the wire is coiled or a linear motor with a pulley system. The rotary category may be divided into two sub-categories: the system with a spiral guide for the coiling, allowing only layer for the wire and the system without guide, that allows for several wire layers with the drawback that the amount of coiled wire for one motor turn depends upon the number of layer. All three systems are compared in terms of accuracy and compacity