Force performance indexes for parallel mechanisms with actuation redundancy, especially for parallel wire-driven manipulators

This paper presents new force performance indexes adapted to parallel mechanisms with actuation redundancy (PMAR) especially parallel wire-driven manipulators (where only tensile forces in cables are possible). Such performance indexes might be used for optimization purpose. At first, the operational force polytope is established. It is the accurate representation of admissible operational forces from the kinetostatic analysis point of view. A way to efficiently compute it is given. The obtained description of the polytope is the same as in (Krut S. et al., March-April 2004), but regarding forces. As a consequence the reader is free to use any of the indexes introduced in (Krut S. et al., March-April 2004). From the authors' point of view the "maximum operational isotropic force" is well adapted to characterize parallel wire-driven manipulators' force behavior. The way to compute it is established. At last, this index is computed for several parallel wire-driven manipulators.