This paper shows how a new combined optimisation algorithm can improve the efficiency in simulation-based parameter tuning of sheet-metal press lines. In automotive tandem sheet-metal press lines there are a number of critical interactions between moving parts to consider during the loading and unloading motions. All these interactions, both within each station and between the stations, are time-critical and must be synchronised to reach high production rates and avoid collisions. This cause conditions such as a highly non-linear objective functions with multiple local optima, considerable number of parameters, and long evaluation times. It is a great challenge to obtain an efficient direct search algorithm for global multi-criteria optimisation fulfilling all these conditions.

The new combined algorithm starts with the Lipschitzian algorithm DIRECT as global search and then switches over to the Nelder-Mead simplex algorithm for local convergence. Furthermore, during the switch over, the algorithm determines all local candidates of the set of points evaluated by DIRECT, and starts multiple Nelder-Mead local searches in each of these.