Planning and Navigation in Dynamic Environments for Mobile Robots and Micro Aerial Vehicles

Reliable and robust navigation planning and obstacle avoidance is key for the autonomous operation of mobile robots. In contrast to stationary industrial robots that often operate in controlled spaces, planning for mobile robots has to take changing environments and uncertainties into account during plan execution. In this thesis, planning and obstacle avoidance techniques are proposed for a variety of ground and aerial robots. Common to most of the presented approaches is the exploitation of the nature of the underlying problem to achieve short planning times by using multiresolution or hierarchical approaches. Short planning times allow for continuous and fast replanning to take the uncertainty in the environment and robot motion execution into account. The proposed approaches are evaluated in simulation and real-world experiments. The first part of this thesis addresses planning for mobile ground robots. One contribution is an approach to grasp and object removal planning to pick objects from a transport box with a mobile manipulation robot. In a multistage process, infeasible grasps are pruned in offline and online processing steps. Collision-free endeffector trajectories are planned to the remaining grasps until a valid removal trajectory can be found. An object-centric local multiresolution representation accelerates trajectory planning. The mobile manipulation components are evaluated in an integrated mobile bin-picking system. Local multiresolution planning is employed for path planning for humanoid soccer robots as well. The used Nao robot is equipped with only relatively low computing power. A resource-efficient path planner including the anticipated movements of opponents on the field is developed as part of this thesis. In soccer games an important subproblem is to reach a position behind the ball to dribble or kick it towards the goal. By the assumption that the opponents have the same intention, an explicit representation of their movements is possible. This leads to paths that facilitate the robot to reach its target position with a higher probability without being disturbed by the other robot. The evaluation for the planner is performed in a physics-based soccer simulation. The second part of this thesis covers planning and obstacle avoidance for micro aerial vehicles (MAVs), in particular multirotors. To reduce the planning complexity, the planning problem is split into a hierarchy of planners running on different levels of abstraction, i.e., from abstract to detailed environment descriptions and from coarse to fine plans. A complete planning hierarchy for MAVs is presented, from mission planners for multiple application domains to low-level obstacle avoidance. Missions planned on the top layer are executed by means of coupled allocentric and egocentric path planning. Planning is accelerated by global and local multiresolution representations. The planners can take multiple objectives into account in addition to obstacle costs and path length, e.g., sensor constraints. The path planners are supplemented by trajectory optimization to achieve dynamically feasible trajectories that can be executed by the underlying controller at higher velocities. With the initialization techniques presented in this thesis, the convergence of the optimization problem is expedited. Furthermore, frequent reoptimization of the initial trajectory allows for the reaction to changes in the environment without planning and optimizing a complete new trajectory. Fast, reactive obstacle avoidance based on artificial potential fields acts as a safety layer in the presented hierarchy. The obstacle avoidance layer employs egocentric sensor data and can operate at the data acquisition frequency of up to 40 Hz. It can slow-down and stop the MAVs in front of obstacles as well as avoid approaching dynamic obstacles. We evaluate our planning and navigation hierarchy in simulation and with a variety of MAVs in real-world applications, especially outdoor mapping missions, chimney and building inspection, and automated stocktaking.Planung und Navigation in dynamischen Umgebungen für mobile Roboter und Multikopter Zuverlässige und sichere Navigationsplanung und Hindernisvermeidung ist ein wichtiger Baustein für den autonomen Einsatz mobiler Roboter. Im Gegensatz zu klassischen Industrierobotern, die in der Regel in abgetrennten, kontrollierten Bereichen betrieben werden, ist es in der mobilen Robotik unerlässlich, Änderungen in der Umgebung und die Unsicherheit bei der Aktionsausführung zu berücksichtigen. Im Rahmen dieser Dissertation werden Verfahren zur Planung und Hindernisvermeidung für eine Reihe unterschiedlicher Boden- und Flugroboter entwickelt und vorgestellt. Den meisten beschriebenen Ansätzen ist gemein, dass die Struktur der zu lösenden Probleme ausgenutzt wird, um Planungsprozesse zu beschleunigen. Häufig ist es möglich, mit abnehmender Genauigkeit zu planen desto weiter eine Aktion in der Zeit oder im Ort entfernt ist. Dieser Ansatz wird lokale Multiresolution genannt. In anderen Fällen ist eine Zerlegung des Problems in Schichten unterschiedlicher Genauigkeit möglich. Die damit zu erreichende Beschleunigung der Planung ermöglicht ein häufiges Neuplanen und somit die Reaktion auf Änderungen in der Umgebung und Abweichungen bei den ausgeführten Aktionen. Zur Evaluation der vorgestellten Ansätze werden Experimente sowohl in der Simulation als auch mit Robotern durchgeführt. Der erste Teil dieser Dissertation behandelt Planungsmethoden für mobile Bodenroboter. Um Objekte mit einem mobilen Roboter aus einer Transportkiste zu greifen und zur Weiterverarbeitung zu einem Arbeitsplatz zu liefern, wurde ein System zur Planung möglicher Greifposen und hindernisfreier Endeffektorbahnen entwickelt. In einem mehrstufigen Prozess werden mögliche Griffe an bekannten Objekten erst in mehreren Vorverarbeitungsschritten (offline) und anschließend, passend zu den erfassten Objekten, online identifiziert. Zu den verbleibenden möglichen Griffen werden Endeffektorbahnen geplant und, bei Erfolg, ausgeführt. Die Greif- und Bahnplanung wird durch eine objektzentrische lokale Multiresolutionskarte beschleunigt. Die Einzelkomponenten werden in einem prototypischen Gesamtsystem evaluiert. Eine weitere Anwendung für die lokale Multiresolutionsplanung ist die Pfadplanung für humanoide Fußballroboter. Zum Einsatz kommen Nao-Roboter, die nur über eine sehr eingeschränkte Rechenleistung verfügen. Durch die Reduktion der Planungskomplexität mit Hilfe der lokalen Multiresolution, wurde die Entwicklung eines Planers ermöglicht, der zusätzlich zur aktuellen Hindernisfreiheit die Bewegung der Gegenspieler auf dem Feld berücksichtigt. Hierbei liegt der Fokus auf einem wichtigen Teilproblem, dem Erreichen einer guten Schussposition hinter dem Ball. Die Tatsache, dass die Gegenspieler vergleichbare Ziele verfolgen, ermöglicht es, Annahmen über mögliche Laufwege zu treffen. Dadurch ist die Planung von Pfaden möglich, die das Risiko, durch einen Gegenspieler passiv geblockt zu werden, reduzieren, so dass die Schussposition schneller erreicht wird. Dieser Teil der Arbeit wird in einer physikalischen Fußballsimulation evaluiert. Im zweiten Teil dieser Dissertation werden Methoden zur Planung und Hindernisvermeidung von Multikoptern behandelt. Um die Planungskomplexität zu reduzieren, wird das zu lösenden Planungsproblem hierarchisch zerlegt und durch verschiedene Planungsebenen verarbeitet. Dabei haben höhere Planungsebenen eine abstraktere Weltsicht und werden mit niedriger Frequenz ausgeführt, zum Beispiel die Missionsplanung. Niedrigere Ebenen haben eine Weltsicht, die mehr den Sensordaten entspricht und werden mit höherer Frequenz ausgeführt. Die Granularität der resultierenden Pläne verfeinert sich hierbei auf niedrigeren Ebenen. Im Rahmen dieser Dissertation wurde eine komplette Planungshierarchie für Multikopter entwickelt, von Missionsplanern für verschiedene Anwendungsgebiete bis zu schneller Hindernisvermeidung. Pfade zur Ausführung geplanter Missionen werden durch zwei gekoppelte Planungsebenen erstellt, erst allozentrisch, und dann egozentrisch verfeinert. Hierbei werden ebenfalls globale und lokale Multiresolutionsrepräsentationen zur Beschleunigung der Planung eingesetzt. Zusätzlich zur Hindernisfreiheit und Länge der Pfade können auf diesen Planungsebenen weitere Zielfunktionen berücksichtigt werden, wie zum Beispiel die Berücksichtigung von Sensorcharakteristika. Ergänzt werden die Planungsebenen durch die Optimierung von Flugbahnen. Diese Flugbahnen berücksichtigen eine angenäherte Flugdynamik und erlauben damit ein schnelleres Verfolgen der optimierten Pfade. Um eine schnelle Konvergenz des Optimierungsproblems zu erreichen, wurde in dieser Arbeit ein Verfahren zur Initialisierung entwickelt. Des Weiteren kommen Methoden zur schnellen Verfeinerung des Optimierungsergebnisses bei Änderungen im Weltzustand zum Einsatz, diese ermöglichen die Reaktion auf neue Hindernisse oder Abweichungen von der Flugbahn, ohne eine komplette Flugbahn neu zu planen und zu optimieren. Die Sicherheit des durch die Planungs- und Optimierungsebenen erstellten Pfades wird durch eine schnelle, reaktive Hindernisvermeidung gewährleistet. Das Hindernisvermeidungsmodul basiert auf der Methode der künstlichen Potentialfelder. Durch die Verwendung dieser schnellen Methode kombiniert mit der Verwendung von nicht oder nur über kurze Zeiträume aggregierte Sensordaten, ermöglicht die Reaktion auf unbekannte Hindernisse, kurz nachdem diese von den Sensoren wahrgenommen wurden. Dabei kann der Multikopter abgebremst oder gestoppt werden, und sich von nähernden Hindernissen entfernen. Die Komponenten der Planungs- und Hindernisvermeidungshierarchie werden sowohl in der Simulation evaluiert, als auch in integrierten Gesamtsystemen mit verschiedenen Multikoptern in realen Anwendungen. Dies sind insbesondere die Kartierung von Innen- und Außenbereichen, die Inspektion von Gebäuden und Schornsteinen sowie die automatisierte Inventur von Lägern

Agency

"There is agency in all we do: thinking, doing, or making. We invent a tune, play, or use it to celebrate an occasion. Or we make a conceptual leap and ask more abstract questions about the conditions for agency. They include autonomy and self-appraisal, each contested by arguments immersing us in circumstances we don’t control. But can it be true we that have no personal responsibility for all we think and do? Agency: Moral Identity and Free Will proposes that deliberation, choice, and free will emerged within the evolutionary history of animals with a physical advantage: organisms having cell walls or exoskeletons had an internal space within which to protect themselves from external threats or encounters. This defense was both structural and active: such organisms could ignore intrusions or inhibit risky behavior. Their capacities evolved with time: inhibition became the power to deliberate and choose the manner of one’s responses. Hence the ability of humans and some other animals to determine their reactions to problematic situations or to information that alters values and choices. This is free will as a material power, not as the conclusion to a conceptual argument. Having it makes us morally responsible for much we do. It prefigures moral identity. Closely argued but plainly written, Agency: Moral Identity and Free Will speaks for autonomy and responsibility when both are eclipsed by ideas that embed us in history or tradition. Our sense of moral choice and freedom is accurate. We are not altogether the creatures of our circumstances.

On the Shores of Education: Urban Bodies, Architectural Repetitions, and the Mythic Space of End Times

Orienting around Plato's allegory of the cave, this dissertation looks back to earlier mythological and historical roots and forward to the spatial aesthetics of "occupation" and "No Child Left Behind," to trace the enduring connection between philosophies and practices of education and sacrificial journeys of descent and emergence. This thematic work of repetition, birth and death, is not so much knowable as it is the privileged way in which we enact and recognize knowing itself. Education, as a spatial practice and a narrative rehearsal, is a way of situating ourselves and organizing our places. Urban Education, rather than being a beleaguered branch of Education proper, cleaves to the very project of Education, emerging as it does out of cities. This is an examination of the philosophical, architectural, urban, aesthetic, and embodied conditions and strategies by which we learn to remember and forget ourselves

Agency

"There is agency in all we do: thinking, doing, or making. We invent a tune, play, or use it to celebrate an occasion. Or we make a conceptual leap and ask more abstract questions about the conditions for agency. They include autonomy and self-appraisal, each contested by arguments immersing us in circumstances we don’t control. But can it be true we that have no personal responsibility for all we think and do? Agency: Moral Identity and Free Will proposes that deliberation, choice, and free will emerged within the evolutionary history of animals with a physical advantage: organisms having cell walls or exoskeletons had an internal space within which to protect themselves from external threats or encounters. This defense was both structural and active: such organisms could ignore intrusions or inhibit risky behavior. Their capacities evolved with time: inhibition became the power to deliberate and choose the manner of one’s responses. Hence the ability of humans and some other animals to determine their reactions to problematic situations or to information that alters values and choices. This is free will as a material power, not as the conclusion to a conceptual argument. Having it makes us morally responsible for much we do. It prefigures moral identity. Closely argued but plainly written, Agency: Moral Identity and Free Will speaks for autonomy and responsibility when both are eclipsed by ideas that embed us in history or tradition. Our sense of moral choice and freedom is accurate. We are not altogether the creatures of our circumstances.

Just Vibrations: The Purpose of Sounding Good

Modern academic criticism bursts with what Eve Kosofsky Sedgwick once termed paranoid readings—interpretative feats that aim to prove a point, persuade an audience, and subtly denigrate anyone who disagrees. Driven by strategies of negation and suspicion, such rhetoric tends to drown out softer-spoken reparative efforts, which forego forceful argument in favor of ruminations on pleasure, love, sentiment, reform, care, and accessibility. Just Vibrations: The Purpose of Sounding Good calls for a time-out in our serious games of critical exchange. Charting the divergent paths of paranoid and reparative affects through illness narratives, academic work, queer life, noise pollution, sonic torture, and other touchy subjects, William Cheng exposes a host of stubborn norms in our daily orientations toward scholarship, self, and sound. How we choose to think about the perpetration and tolerance of critical and acoustic offenses may ultimately lead us down avenues of ethical ruin—or, if we choose, repair. With recourse to experimental rhetoric, interdisciplinary discretion, and the playful wisdoms of childhood, Cheng contends that reparative attitudes toward music and musicology can serve as barometers of better worlds

On the Problem of Sustainable Economic Development: A Theoretical Solution to this Prisoner's Dilemma

This paper offers a solution to The Problem of Sustainable Economic Development, and a universal theory of value. We introduce axioms which serve as the first of two derivations of our solution, our methods, the origin and evolution of our theory, field notes from Mustique, Iceland, and Prince Edward Island, and set the stage for a more thorough discourse. Next we demonstrate that value (V) is a derivative function of relative insularity (IR): V=f´(IR), then model economic development by dividing the world into geo-political islands: Relatively Insular States (RIS), and Global Economic Military Superpowers (GEMS). Our axioms deduce two opposing development strategies: Maximum Economic Development (MED), and Maximum Ecological Preservation (MEP). We clarify this by applying our Theory of Value within geo-political contexts which reveal divergent, optimizing strategies for GEMS and RIS economic development. We discover GEMS and RIS strategies are antithetical, yet also discover these naturally opposing strategies represent the most tenable, rational solution-set possible. In light of the inherent and inescapable planetary uncertainties our axiom reveal, we discover the optimal RIS strategy = MEP and GEMS = MED. We note our solution represents the Prisoner's Dilemma. We also note, that, ceteris paribus, based upon revealed 20th and 21st century preferences, RIS strategy has been suboptimal/irrational. Strategic Equilibrium is attained when players pursue respective rational, opposing development strategies. Equilibrium, however, offers windfalls: surplus value is created (RIS-driven ecological preservation, and GEMS-driven Global Security and Planetary Protection). In essence, this non-cooperative, strategic equilibrium paves the way for rational, mutually beneficial, cooperative behaviour, and yields surplus ecological and planetary insularities, and thus surplus economic and biologic value: RIS cooperate, form coalitions, and struggle for greater ecological insularity (ecological preservation). At the same time, GEMS fight for economic development and planetary insularity (planetary preservation, i.e. financing national and global defense, extraterrestrial exploration, and solutions to mission-critical, extra-planetary threats to human existence). Furthermore, surplus value is maximized through strategic transparency: If all players recognize the value of respective, opposing, and antithetical, rational strategies, then all players negotiate more rationally, efficiently, and peacefully. We refer to our solution based upon two opposing, rational strategies as The Funk- Zweikampf Solution. Moreover, we demonstrate our solution is as powerful at local and individual levels as it is at the national level, including its use as a tool for strategic decisionmaking under uncertainty and variable insularity. Furthermore, our Theory of Value illuminates an entrenched, systemic, strategic RIS error which reflects the false application of widely misunderstood economic principles, and fundamental constitutional defects which promote The Tragedy of the Commons. Our theory also suggests that it is no coincidence that the island which best exhibits optimal pure RIS economic development strategy (MEP) is the uniquely independent, autonomous, privately-controlled island of Mustique. All RIS, however, may optimize with our counter-intuitive solution through individual, regional, and state coalitions. Furthermore, our Theory of Value promotes self-organization, constitutional amendment, self-sufficiency, independence, and thus places stones along the illusive path to a tenable solution to The Problem of Sustainable Development.Tragedy of the commons; sustainable economic development; island economic development; global threat mitigation; relative insularity; theory of value

Approaching the Planck Scale from a Generally Relativistic Point of View: A Philosophical Appraisal of Loop Quantum Gravity

My dissertation studies the foundations of loop quantum gravity (LQG), a candidate for a quantum theory of gravity based on classical general relativity. At the outset, I discuss two---and I claim separate---questions: first, do we need a quantum theory of gravity at all; and second, if we do, does it follow that gravity should or even must be quantized? My evaluation of different arguments either way suggests that while no argument can be considered conclusive, there are strong indications that gravity should be quantized.LQG attempts a canonical quantization of general relativity and thereby provokes a foundational interest as it must take a stance on many technical issues tightly linked to the interpretation of general relativity. Most importantly, it codifies general relativity's main innovation, the so-called background independence, in a formalism suitable for quantization. This codification pulls asunder what has been joined together in general relativity: space and time. It is thus a central issue whether or not general relativity's four-dimensional structure can be retrieved in the alternative formalism and how it fares through the quantization process. I argue that the rightful four-dimensional spacetime structure can only be partially retrieved at the classical level. What happens at the quantum level is an entirely open issue.Known examples of classically singular behaviour which gets regularized by quantization evoke an admittedly pious hope that the singularities which notoriously plague the classical theory may be washed away by quantization. This work scrutinizes pronouncements claiming that the initial singularity of classical cosmological models vanishes in quantum cosmology based on LQG and concludes that these claims must be severely qualified. In particular, I explicate why casting the quantum cosmological models in terms of a deterministic temporal evolution fails to capture the concepts at work adequately. Finally, a scheme is developed of how the re-emergence of the smooth spacetime from the underlying discrete quantum structure could be understood

Ahlfors circle maps and total reality: from Riemann to Rohlin

This is a prejudiced survey on the Ahlfors (extremal) function and the weaker {\it circle maps} (Garabedian-Schiffer's translation of "Kreisabbildung"), i.e. those (branched) maps effecting the conformal representation upon the disc of a {\it compact bordered Riemann surface}. The theory in question has some well-known intersection with real algebraic geometry, especially Klein's ortho-symmetric curves via the paradigm of {\it total reality}. This leads to a gallery of pictures quite pleasant to visit of which we have attempted to trace the simplest representatives. This drifted us toward some electrodynamic motions along real circuits of dividing curves perhaps reminiscent of Kepler's planetary motions along ellipses. The ultimate origin of circle maps is of course to be traced back to Riemann's Thesis 1851 as well as his 1857 Nachlass. Apart from an abrupt claim by Teichm\"uller 1941 that everything is to be found in Klein (what we failed to assess on printed evidence), the pivotal contribution belongs to Ahlfors 1950 supplying an existence-proof of circle maps, as well as an analysis of an allied function-theoretic extremal problem. Works by Yamada 1978--2001, Gouma 1998 and Coppens 2011 suggest sharper degree controls than available in Ahlfors' era. Accordingly, our partisan belief is that much remains to be clarified regarding the foundation and optimal control of Ahlfors circle maps. The game of sharp estimation may look narrow-minded "Absch\"atzungsmathematik" alike, yet the philosophical outcome is as usual to contemplate how conformal and algebraic geometry are fighting together for the soul of Riemann surfaces. A second part explores the connection with Hilbert's 16th as envisioned by Rohlin 1978.Comment: 675 pages, 199 figures; extended version of the former text (v.1) by including now Rohlin's theory (v.2

An Interpretive Theory of International Law: The Distinction Between Treaty and Customary Law

The author begins with an explanation of the importance of the distinction between treaty and customary law. The author then presents six alternative principles currently used to inform that distinction (dichotomy, overlap, relativity, interdependence, equivalence, and indeterminacy) and evaluates the application of these principles according to their theoretical coherence, practicability, reconcilability, and resolving power. The author concludes that each of the alternative principles is unsatisfactory in at least one respect and proposes a superior interpretive approach that does not define customary law in terms of treaty, but rather according to its own independently defining attributes. Finally, the author suggests that this approach, called sub-referential threshold relativity (STR), may be applied to other key distinctions in legal doctrine and scholarship

Proceedings of the 3rd International Conference on Models and Technologies for Intelligent Transportation Systems 2013

Challenges arising from an increasing traffic demand, limited resource availability and growing quality expectations of the customers can only be met successfully, if each transport mode is regarded as an intelligent transportation system itself, but also as part of one intelligent transportation system with “intelligent” intramodal and intermodal interfaces. This topic is well reflected in the Third International Conference on “Models and Technologies for Intelligent Transportation Systems” which took place in Dresden 2013 (previous editions: Rome 2009, Leuven 2011). With its variety of traffic management problems that can be solved using similar methods and technologies, but with application specific models, objective functions and constraints the conference stands for an intensive exchange between theory and practice and the presentation of case studies for all transport modes and gives a discussion forum for control engineers, computer scientists, mathematicians and other researchers and practitioners. The present book comprises fifty short papers accepted for presentation at the Third Edition of the conference. All submissions have undergone intensive reviews by the organisers of the special sessions, the members of the scientific and technical advisory committees and further external experts in the field. Like the conference itself the proceedings are structured in twelve streams: the more model-oriented streams of Road-Bound Public Transport Management, Modelling and Control of Urban Traffic Flow, Railway Traffic Management in four different sessions, Air Traffic Management, Water Traffic and Traffic and Transit Assignment, as well as the technology-oriented streams of Floating Car Data, Localisation Technologies for Intelligent Transportation Systems and Image Processing in Transportation. With this broad range of topics this book will be of interest to a number of groups: ITS experts in research and industry, students of transport and control engineering, operations research and computer science. The case studies will also be of interest for transport operators and members of traffic administration