Model-Based Systems Engineering in Mobile Applications

An efficient system development needs reuse, traceability and understanding. Today, specifications are usually written in text documents. Reuse means a copy and paste of suitable specifications. Traceability is the textual note that references to affected requirements. Achieving a full context understanding requires reading hundreds of pages in a variety of documents. Changing one textual requirement in complex systems can be very time-consuming. Model-based systems engineering (MBSE) addresses these issues. There, an integrated system model is used for the design, analysis, communication and system specification and shall contribute to handling the system complexity. This paper shows aspects of this approach in the development of a wheel loader\'s attachment system. Customer requirements will be used to derive a specification model. Based on this, the author introduces the system and software architecture. The connection between requirement and architecture leads to a traceable system design and produces the huge advantage of MBSE

Comparing contact and dipolar interaction in a Bose-Einstein condensate

We have measured the relative strength $\epsilon_dd$ of the magnetic dipole-dipole interaction compared to the contact interaction in a chromium Bose-Einstein condensate. We analyze the asymptotic velocities of expansion of a dipolar chromium BEC with different orientations of the atomic magnetic dipole moments. By comparing them with numerical solutions of the hydrodynamic equations for dipolar condensates, we are able to determine $\epsilon_dd = 0.159\pm0.034$ with high accuracy. Since the absolute strength of the dipole-dipole interaction is known exactly, the relative strength of the dipoledipole interaction can be used to determine the s-wave scattering length $a = 5.08\pm1.06\cdot10^-9 m = 96\pm20 a0$ of 52Cr. This is fully consistent with our previous measurements on the basis of Feshbach resonances

Green Wheel Loader – improving fuel economy through energy efficient drive and control concepts

The drive train components and the machine control system significantly influence the fuel consumption of mobile machinery. The demonstrator vehicle “Green Wheel Loader” developed within the joint research project “TEAM” combines the most promising drive concepts currently available for mobile machines with an innovative operating strategy. The developed drive and control system proved its functionality and performance under realistic operation conditions in a gravel pit. Reference test showed 10 – 15 % fuel savings of the prototype vehicle compared to a state-of-the-art series machine

Laserendbearbeitung metallischer Werkstoffe

Die Laserendbearbeitung metallischer Werkstoffe fasst die Einzelprozesse der abtragenden Mikromaterialbearbeitung von Metallen mit Laserpulsen von ns-Dauer zusammen. Dabei wird erstmals die Strahlausbreitung in die Betrachtungen einbezogen. Somit gelingt es, ein Modell zu erarbeiten, das Vorhersagen zu Optimierungsbemühungen erlaubt und ein tieferes Verständnis dieser Abtragprozesse ermöglicht. Schließlich führen Optimierungsergebnisse auf Basis der entwickelten Modellvorstellung zu einer Verkürzung der Prozesskette. So gelingt einerseits die Aufteilung des Bearbeitungsprozesses in Schruppen und Schlichten, andererseits motiviert die Beobachtung von erstarrten Schmelzefilmen zur Erzeugung einer definierten Schmelzeschicht. Damit kann die Qualität der gefertigten Oberflächen bei reduzierter Bearbeitungszeit gesteigert werden, wobei sich die Fertigung in einer Aufspannung realisiert lässt.The present work, laser finishing of metallic materials, summarizes the individual processes of ablative micromachining of metals with laser pulses of ns duration. Thus, synergetic effects between these erosive processes are revealed, serving a description of both, the stationary ablation, i.e. the mechanisms of material removal, when laser pulses are applied in a static superposition, as well as the dynamic erosion, i.e. laser machining at a relative motion between incident laser beam and work piece. In addition, investigations on beam propagation are leading to the development of a conceptual model that considers not only ablation mechanisms but also optical parameters at once. On that basis a simulation of pulse superposition for two-dimensional laser processing is created, which allows a prediction of the machining results and a visualization of optimization efforts as well. Results of own experimental studies and data from literature are used to develop the conceptual model. Moreover, the results serve for identification and verification of predominating parameters on the ablation process. They also confirm that the well-known mechanisms of stationary ablation remain to be valid in case of percussion drilling as well as for two-dimensional laser processing. However, for a complete description of the two-dimensional laser processing, also the radiation propagation and the resulting beam-material interaction are to be considered with respect to the overlapping use of a multiplicity at laser pulses. This is leading to the consideration of the iso-intensity lines along the beam propagation direction and to the definition of a limiting intensity, which depends on the ablation threshold, thus the thermo-physical properties of the material. Among other things, it allows the description of the resulting geometry along the drilling axis of holes produced by use of percussion drilling. Finally, optimization results lead on basis of the developed conceptual model to a shortening of the process chain. By dividing the process in rough and finish machining the quality of the manufactured surfaces can be increased. The observation of solidified melt films on these surfaces motivates additionally to the production of a defined melt layer. Hence, by applying continuous laser radiation in alteration with finish machining smooth or shiny surfaces are obtained in one setting