Meta Modelle - Neue Planungswerkzeuge für Materialflußsysteme

Meta-Modelle sind Rechenmodelle, die das Verhalten technischer Systeme näherungsweise beschreiben oder nachbilden. Sie werden aus Beobachtungen von Simulationsmodellen der technischen Systeme abgeleitet. Es handelt sich also um Modelle von Modellen, um Meta-Modelle. Meta-Modelle unterscheiden sich grundsätzlich von analytischen Ansätzen zur Systembeschreibung. Während analytische Ansätze in ihrer mathematischen Struktur die tatsächlichen Gegebenheiten des betrachteten Systems wiedergeben, sind Meta-Modelle stets Näherungen. Der Vorteil von Meta-Modellen liegt in ihrer einfachen Form. Sie sind leicht zu bilden und anzuwenden. Ihr Nachteil ist die nur annähernde und u.U. unvollständige Beschreibung des Systemverhaltens. Im folgenden wird die Bildung von Meta-Modellen anhand eines Bediensystems dargestellt. Zuerst werden die Möglichkeiten einer analytischen Beschreibung bewertet. Danach werden zwei unterschiedliche Meta-Modelle, Polynome und neuronale Netze, vorgestellt. Möglichkeiten und Grenzen dieser Formen der Darstellung des Systemverhaltens werden diskutiert. Abschließend werden praktische Einsatzfelder von Meta-Modellen in der Materialflußplanung und -simulation aufgezeigt

An MDO exercise using response surface methodology: optimal shape and composite structure of a wing for optimal range

Engineering problems of multidisciplinary nature are challenging where design optimization requires effective communication of the disciplines. This communication is typically referred as multidisciplinary design optimization (MDO) framework. One of the strategies in such a framework is to use of approximations within and among the disciplines to facilitate the navigation of information through a discipline A by an expert in discipline B. Response surface methodology (RSM) for instance is an effective way to bridge the information and expertise between the disciplines within the framework to complete an MDO problem. This thesis makes a demonstration of RSM in an aircraft composite wing design example. Approximation by RSM aims to generate a prediction tool for optimal structural weight which is required to optimize wing exterior planform for maximum performance, here set as the range of the aircraft. Three planform/shape parameters are chosen: wing span, tip and chord length. For each planform there exists an optimal structure to be found by finite element based structural optimization. The structural optimization level for a given planform makes also use of a different kind of approximation associated with the laminated composite materials. Laminates are treated as homogenized through the thickness and equivalent laminate mechanical properties are implemented. In other words, homogenized laminates approach allows using single continuous thickness variables for each assigned laminate domain replacing the ply-by-ply description of the laminated structure within the structural analyses. Comparison of the homogenized laminate approach and ply-by-ply analyses for a reference wing design is also provided and concluded that former can be incorporated into the design optimization cycles. The MDO framework for the present example is as follows: Wing planforms are described by full factorial DOE. For each configuration/planform: a) LAMDES was used to calculate aerodynamic forces., b) weight optimization of the wing structure subject to displacement and stress constraints was accomplished using MSC Nastran SOL 200 module. Statistical software JMP 7 was then used to construct an RS weight equation. Genetic Algorithm tool of MATLAB was applied for the range optimization

Nonparametic-validated computer-simulation surrogates : a Pareto formuation

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.Includes bibliographical references (p. 91-96).by Miltos E. Kambourides.M.S

Experimental Geometry Optimization Techniques for Multi-Element Airfoils

A study is reported on geometry optimization techniques for high-lift airfoils. A modern three-element airfoil model with a remotely actuated flap was designed, tested, and used in wind tunnel experiments to investigate optimum flap positioning based on lift. All the results presented were obtained in the Old Dominion University low-speed wind tunnel. Detailed results for lift coefficient versus flap vertical and horizontal position are presented for two airfoil angles-of-attack: 8 and 14 degrees. Three automated optimization simulations, the method of steepest ascent and two variants of the sequential simplex method, were demonstrated using experimental data. An on-line optimizer was demonstrated with the wind tunnel model which automatically seeks the optimum lift as a function of flap position. Hysteresis in lift as a function of flap position was discovered when tests were conducted with continuous flow conditions. It was shown that optimum lift coefficients determined using continuous flow conditions exist over an extended range of flap positions when compared to those determined using traditional intermittent conditions