A cooperative approach to multi-level multi-disciplinary aircraft optimization

Kurzfassung

In the usual approach to multi-disciplinary optimization (MDO), a few experts in optimization select and integrate disciplinary tools into a working MDO process, run it on target cases, and analyze the results. This approach is expedient, but it tends to oversimplify employment of disciplines. German Aerospace Center (DLR) is currently pursuing a more cooperative approach, where disciplinary experts from different DLR institutes are involved throughout in the definition, implementation, and evaluation of MDO processes. The goal is to establish a modular MDO platform, with well-balanced fidelity levels of employed disciplines, that can be used both for overall aircraft design, as well as for studying the influence of particular subsystem improvements on the overall design objective. Two MDO processes resulting from this effort so far are presented. The objective in both process is to minimize the mission fuel burn, as evaluated through Breguet range equation. One is a derivative-free process employing multi-level analysis, comprising the conceptual design level for determining the dependent top-level parameters, dynamic level for computing the sizing loads, and detailed level for sizing the structure and computing the performance indicators. The other is a gradient-based process on the detailed level alone, employing a split of design parameters between CAD-based and CAD-free, and treating all structural constraints independently. The set of sizing-relevant load cases is automatically determined based either on the actual configuration (in the derivative-free process) or on the baseline configuration (in the gradient-based process), rather than applying a set of generic load cases. The contribution concludes with several example studies carried out using these processes.