Abstract
Although cable driven robots are a type of parallel manipulators, the evaluation of their performances cannot be carried out using the performance indices already developed for parallel robots with rigid links. This is an obvious consequence of the peculiar features of flexible cables—a cable can only exert a tensile and limited force in the direction of the cable itself. A comprehensive performance evaluation can certainly be attained by computing the maximum force (or torque) that can be exerted by the cables on the moving platform along a specific (or any) direction within the whole workspace. This is the idea behind the index—called the Wrench Exertion Capability (WEC)—which can be employed to evaluate the performance of any cable robot topology and is characterized by an efficient and simple formulation based on linear programming. By significantly improving a preliminary computation method for the WEC, this paper proposes an ultimate formulation suitable for any cable robot topology. Several numerical investigations on planar and spatial cable robots are presented to give evidence of the WEC usefulness, comparisons with popular performance indices are also provided.
Highlights
Cable driven robots, or cable robots, are relatively simple parallel manipulators, operating in planar or spatial arrangements, formed by attaching multiple cables to a moving platform, on which the end-effector is fitted
For example, the Wrench Exertion Capability (WEC) of a fully constrained cable robot can be expressed in terms of the maximum force w f d that can be exerted along the direction d while keeping bounded cable tensions f and given values w e R of the other wrench components
The objective is to provide a clear proof of the effectiveness and usefulness of the WEC when it is employed at the design stage to find the regions of the workspace where a cable robot can best perform, or to compare different cable robot topologies or cable layouts
Summary
Cable robots, are relatively simple parallel manipulators, operating in planar or spatial arrangements, formed by attaching multiple cables to a moving platform, on which the end-effector is fitted. Can the WEC be employed for maximum force/torque evaluations and to compute the minimum force/torque values which can be guaranteed throughout the workspace, irrespective of the direction and for isotropy evaluations All these analyses allow getting considerable insight into cable robot performances and give the possibility to perform comprehensive comparisons among the performances of cable robots with different topologies and alternative cable layouts: such comparative investigations often need to be carried out since it is apparent that are the performances of cable robots influenced by the number of active cables and by their geometrical arrangement.
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