Hybrid optimization strategy beyond local optima in aerospace panel designs

Convergence to local optima rather than the global optimum is a common shor tcoming of directed search (gradient based) optimization techniques. Succes sive convergence on better local optima is an efficient way of finding the global optimum and is achieved by the proposed hybrid global optimization s trategy, which combines ideas from the improving hit-and-run and the tunnel ing global optimization methods. The searching technique of improving hit-a nd run is adapted to find suitable starting points to converge on other (be tter) local optima. The suitability of candidate starting points is confirm ed by the concept of the tunneling method. The strategy presented has uniqu e features due to the underlying structural theory being exact, in the sens e of differential equations being solved for the member (or element) stiffn esses so that they are transcendental functions of the load factor Hence th e buckling eigenproblem for the entire structure is a transcendental one, i nstead of the linear one associated with the more usual finite element meth od formulations. Constrained minimum mass aerospace panel stability design problems are used to demonstrate the efficiency and robustness of the hybri d global optimization strategy.