Safe Controller Optimization for Quadrotors with Gaussian Processes

One of the most fundamental problems when designing controllers for dynamic systems is the tuning of the controller parameters. Typically, a model of the system is used to obtain an initial controller, but ultimately the controller parameters must be tuned manually on the real system to achieve the best performance. To avoid this manual tuning step, methods from machine learning, such as Bayesian optimization, have been used. However, as these methods evaluate different controller parameters on the real system, safety-critical system failures may happen. In this paper, we overcome this problem by applying, for the first time, a recently developed safe optimization algorithm, SafeOpt, to the problem of automatic controller parameter tuning. Given an initial, low-performance controller, SafeOpt automatically optimizes the parameters of a control law while guaranteeing safety. It models the underlying performance measure as a Gaussian process and only explores new controller parameters whose performance lies above a safe performance threshold with high probability. Experimental results on a quadrotor vehicle indicate that the proposed method enables fast, automatic, and safe optimization of controller parameters without human intervention.Comment: IEEE International Conference on Robotics and Automation, 2016. 6 pages, 4 figures. A video of the experiments can be found at http://tiny.cc/icra16_video . A Python implementation of the algorithm is available at https://github.com/befelix/SafeOp

Outside the Gates of Europe, the Weapons Speak : Metaphorical Conceptualizations of Ukraine and Russia in German Media Discourse

The world of global politics is composed of complex, interrelated and events. To obtain information, to form an opinion and to react to recent developments, policy makers as well as the public depend on news media. Decisions in the field of global politics, therefore, are based on perceptions and beliefs rather than on objective assessments. The following study takes the example of the German print media, analysing the German perception of Russia and Ukraine within the context of the ongoing Ukraine conflict. The current political development in Ukraine is complex, driven by geopolitical, economical and ideological factors. A mediation of these events by news media therefore requires a drastic reduction of complexity to inform readers and decision-makers on developments in this region. Through examination of conceptual metaphors used in the representation of the conflict, this study seeks to better understand how the two main state actors are comprehended and portrayed in German media discourse

Evaluating knowledge transfer at the interface between science and society

In view of the global grand challenges, fundamental research institutions are increasingly being asked to provide context for the application of their research findings and to incorporate transdisciplinary forms of knowledge production. But how can the involvement of stakeholders from outside academia be captured and evaluated within the research process? And how can they be engaged in meaningful science-stakeholder dialogue? “Good” processes are a prerequisite for meeting these changing requirements and for ensuring a successful knowledge transfer at the interface between science and society

The multi-protein family of sulfotransferases in plants: composition, occurrence, substrate specificity, and functions

All members of the sulfotransferase (SOT, EC 2.8.2.-) protein family transfer a sulfuryl group from the donor 3’-phosphoadenosine 5’-phosphosulfate (PAPS) to an appropriate hydroxyl group of several classes of substrates. The primary structure of these enzymes is characterized by a histidine residue in the active site, defined PAPS binding sites and a longer SOT domain. Proteins with this SOT domain occur in all organisms from all three domains, usually as a multi-protein family. Arabidopsis thaliana SOTs, the best characterized SOT multi-protein family, contains 21 members. The substrates for several plant enzymes have already been identified, such as glucosinolates, brassinosteroids, jasmonates, flavonoids, and salicylic acid. Much information has been gathered on desulfoglucosinolate (dsGl) SOTs in A. thaliana. The three cytosolic dsGI SOTs show slightly different expression patterns. The recombinant proteins reveal differences in their affinity to indolic and aliphatic dsGls. Also the respective recombinant dsGl SOTs from different A. thaliana ecotypes differ in their kinetic properties. However, determinants of substrate specificity and the exact reaction mechanism still need to be clarified. Probably, the three-dimensional structures of more plant proteins need to be solved to analyze the mode of action and the responsible amino acids for substrate binding. In addition to A. thaliana, more plant species from several families need to be investigated to fully elucidate the diversity of sulfated molecules and the way of biosynthesis catalyzed by SOT enzymes.DFG/PA/764/10-

Modellierung von Straßennetzen auf Basis diskreter Messpunkte

Diese Diplomarbeit beschäftigt sich mit der Erstellung einer Software, mit der existierende Straßennetze digital modelliert werden können. Grundlage der Modellierung sind Messpunkte, die von einem Messfahrzeug aufgezeichnet werden, welches das Straßennetz befährt und dabei in festen Zeitabständen seine Position erfasst. Die Software wird auf Basis von Messplan 1.0 entwickelt, einem Programm, das bereits die Erfassung einzelner Straßen beziehungsweise Streckenabschnitten beherrscht. Davon ausgehend wird Funktionalität implementiert, um Kreuzungen erfassen und diese mit Straßen verknüpfen zu können. Das Resultat ist eine neue Version von Messplan, mit der die Erfassung von Straßennetzwerken möglich ist