Optimization of the prestress stable wrench closure workspace of planar parallel three-degree-of-freedom cable-driven mechanisms with four cables

There exist configurations of parallel cable-driven mechanisms (CDM) within their wrench closure workspace (WCW) for which they may become unstable when their cables are subjected to internal forces due to prestress or external loads. With the goal of avoiding such configurations, the prestress stable WCW (PSWCW) is defined as a subset of the WCW where an increase in the prestress level leads to an increase in the overall stiffness of the mechanism. A genetic algorithm is used to optimize the geometry of planar parallel CDMs with four cables with the objective of reaching a desired PSWCW. Results are obtained that may guide the designer in the preliminary selection of mechanism dimensions and cable connectivities.