SENSITIVITY ANALYSIS OF TENSION DISTRIBUTION ALGORITHMS FOR CABLE-DRIVEN PARALLEL ROBOTS

Cable-Driven Parallel Robots (CDPRs) constitute a class of robots which displace a load by means of cables, pulleys and electric motors. Since cable tensions have to be bounded above and below, their use to guide the end-effector continues to be a challenging task. Indeed, several Tension Distribution Algorithms (TDAs) have been developed so far to properly steer the load. Although comparisons between them have been made, no performance index is established to evaluate numerically such methods. Therefore, this paper aims at defining a performance index establishing the sensitivity of a TDA by looking at the maximum tension variation that stems from a change in the external wrench. This would help both comparing and choosing the proper TDA among the existing ones. The definition of the index pops out naturally from the linearization of the equations defining the optimization problems. Hence, in this paper, commonly used TDAs are reproduced and then compared using the defined index. In order to show an application of it, a planar CDPR with four cables and a point mass load is considered. The simulations aim at characterizing its Wrench-Feasible Workspace (WFW) by means of the sensitivity index hereby defined. This will allow quantitative comparisons between above-mentioned TDAs.