6. A New Strategy for Form Finding and Optimal Design of Space Cable Network Structures

Cable network structures, which are a class of nonlinear flexible structures, have been widely used in infrastructures and spacecrafts. In this work, a new form-finding method, namely, the fixed nodal position method (FNPM), is developed for optimal design of geometric configuration and internal force distribution for cable network structures, to meet the operation requirement of high shape/surface accuracy. Different from conventional methods, which usually adopts a stress-first-and-displacement-later procedure in form finding, the FNPM first assigns nodal coordinates for a cable network structure and then determines the internal force distribution of the structure by a nonlinear optimization process. The highlight of the FNPM is that the prescribed nodal coordinates are unchanged during the form-finding process. This unique feature of fixed nodal positions makes it possible to place the nodes of a cable network structure at desired locations, satisfying complicated structural constrains and yielding high shape/surface accuracy as required. As another advantage, the FNPM in form finding undertakes the assignment of geometric configuration (nodal coordinates) and the determination of internal force distribution separately. This translates into significant savings in computational effort, compared with conventional form-finding methods. The new form-finding method is applied to the optimal design of a large deployable mesh reflector of 865 nodes.