A Constraint-based Mission Planning Approach for Reconfigurable Multi-Robot Systems

The application of reconfigurable multi-robot systems introduces additional degrees of freedom to design robotic missions compared to classical multi-robot systems. To allow for autonomous operation of such systems, planning approaches have to be investigated that cannot only cope with the combinatorial challenge arising from the increased flexibility of modular systems, but also exploit this flexibility to improve for example the safety of operation. While the problem originates from the domain of robotics it is of general nature and significantly intersects with operations research. This paper suggests a constraint-based mission planning approach, and presents a set of revised definitions for reconfigurable multi-robot systems including the representation of the planning problem using spatially and temporally qualified resource constraints. Planning is performed using a multi-stage approach and a combined use of knowledge-based reasoning, constraint-based programming and integer linear programming. The paper concludes with the illustration of the solution of a planned example mission

Constraint basierte Modellierung von Komponentennetzwerken am Beispiel eines autonomen Unterwasserfahrzeugs

Moderne Robotersysteme werden zunehmend komplexer. Die Forschung im Bereich der Robotik sieht sich immer mehr mit dem Problem der Integration von Algorithmen in neue Plattformen konfrontiert. Es gibt zahlreiche innovative Verfahren und Algorithmen, die die Robotersysteme mit neuen Fähigkeiten ausstatten. Diese Erweiterungen lassen sich sowohl auf der Hardware- als auch der Softwareebene erkennen. Jedoch findet diese Vielzahl an neuen Entwicklungen nur selten Anwendung auf den aktuellen Ziel-Plattformen. Dies bremst weitere Entwicklungen, da mehr Zeit für die Integration als für die eigentliche Forschung aufgewendet wird. Mit einem Blick über die eigene Forschung hinaus oder durch die detailliertere Beschäftigung mit den eingesetzten Verfahren lässt sich erkennen, dass die Lösungen zumeist systemspezifisch sind oder sich nur mit großer Mühe auf andere oder gar größere komplexere Maßstäbe übertragen lassen. Das Ziel dieser Arbeit ist es daher zu identifizieren, wo die größten Herausforderun liegen. Im Anschluss soll das markanteste Problem gelöst werden. Die Modularisierung sowie die modellgetriebene Entwicklung sind dabei die größten Änderungen, die sich Abzeichen. Beide Trends haben verschiedene, teils gravierende Einflüsse auf die Art und Weise, wie Entwicklung stattfindet. Modularisierung erhöht die Wiederverwendbarkeit einzelner Module und führt zu kleineren Verbunden. Modellgetriebene Entwicklung versucht mögliche Fehler in Konzepten zu einem frühen Zeitpunkt zu erkennen. Konkret bedeuten beide Verfahren jedoch Mehrarbeit im Vergleich zu der klassischen monolithischen und reaktiven Systementwicklung. Die Komponenten lassen sich zwar oftmals wiederverwenden, aber die Konsistenz und Nebeneffekte der Selektion bzw. der Abhängigkeiten erfordern viel Zeit und Expertenwissen. Die modellgetriebene Softwareentwicklung verlangt von den Entwicklern von Algorithmen bereits im Voraus Informationen darüber, wie und unter welchen Bedingungen ihr Algorithmus operieren kann. Auf der anderen Seite, der Hardwareentwicklung, stehen immer kleinere und hoch integrierte Sensoren und Aktuatoren zur Verfügung, die wiederum die Konstruktion immer komplexerer Systeme erlauben. Die Systeme bieten oftmals ausreichend Redundanz, um Probleme auf unterschiedliche Art und Weise lösen zu können

Autonomous Operation of a Reconfigurable Multi-Robot System for Planetary Space Missions

Reconfigurable robots can physically merge and form new types of composite systems. This ability leads to additional degrees of freedom for robot operations especially when dynamically composed robotic systems offer capabilities that none of the individual systems have. Research in the area of reconfigurable multi-robot systems has mainly been focused on swarm-based robots and thereby to systems with a high degree of modularity but a heavily restricted set of capabilities. In contrast, this thesis deals with heterogeneous robot teams comprising individually capable robots which are also modular and reconfigurable. In particular, the autonomous application of such reconfigurable multi-robot systems to enhance robotic space exploration missions is investigated. Exploiting the flexibility of a reconfigurable multi-robot system requires an appropriate system model and reasoner. Hence, this thesis introduces a special organisation model. This model accounts for the key characteristics of reconfigurable robots which are constrained by the availability and compatibility of hardware interfaces. A newly introduced mapping function between resource structures and functional properties permits to characterise dynamically created agent compositions. Since a combinatorial challenge lies in the identification of feasible and functionally suitable agents, this thesis further suggests bounding strategies to reason efficiently with composite robotic systems. This thesis proposes a mission planning algorithm which permits to exploit the flexibility of reconfigurable multi-robot systems. The implemented planner builds upon the developed organisation model so that multi-robot missions can be specified by high-level functionality constraints which are resolved to suitable combinations of robots. Furthermore, the planner synchronises robot activities over time and characterises plans according to three objectives: efficacy, efficiency and safety. The plannera s evaluation demonstrates an optimization of an exemplary space mission. This research is based on the parallel development of theoretical concepts and practical solutions while working with three reconfigurable multi-robot teams. The operation of a reconfigurable robotic team comes with practical constraints. Therefore, this thesis composes and evaluates an operational infrastructure which can serve as reference implementation. The identification and combination of applicable state-of-the-art technologies result in a distributed and dynamically extensible communication infrastructure which can maintain the properties of reconfigurable multi-robot systems. Field tests covering semi-autonomous and autonomous operation have been performed to characterise multi-robot missions and validate the autonomous control approach for reconfigurable multi-robot systems. The practical evaluation identified critical constraints and design elements for a successful application of reconfigurable multi-robot systems. Furthermore, the experiments point to improvements for the organisation model. This thesis is a wholistic approach to automate reconfigurable multi-robot systems. It identifies theoretical as well as practical challenges and it suggests effective solutions which permit an exploitation of an increased level of flexibility in future robotics missions

Autonomous Operation of a Reconfigurable Multi-Robot System for Planetary Space Missions

Reconfigurable robots can physically merge and form new types of composite systems. This ability leads to additional degrees of freedom for robot operations especially when dynamically composed robotic systems offer capabilities that none of the individual systems have. Research in the area of reconfigurable multi-robot systems has mainly been focused on swarm-based robots and thereby to systems with a high degree of modularity but a heavily restricted set of capabilities. In contrast, this thesis deals with heterogeneous robot teams comprising individually capable robots which are also modular and reconfigurable. In particular, the autonomous application of such reconfigurable multi-robot systems to enhance robotic space exploration missions is investigated. Exploiting the flexibility of a reconfigurable multi-robot system requires an appropriate system model and reasoner. Hence, this thesis introduces a special organisation model. This model accounts for the key characteristics of reconfigurable robots which are constrained by the availability and compatibility of hardware interfaces. A newly introduced mapping function between resource structures and functional properties permits to characterise dynamically created agent compositions. Since a combinatorial challenge lies in the identification of feasible and functionally suitable agents, this thesis further suggests bounding strategies to reason efficiently with composite robotic systems. This thesis proposes a mission planning algorithm which permits to exploit the flexibility of reconfigurable multi-robot systems. The implemented planner builds upon the developed organisation model so that multi-robot missions can be specified by high-level functionality constraints which are resolved to suitable combinations of robots. Furthermore, the planner synchronises robot activities over time and characterises plans according to three objectives: efficacy, efficiency and safety. The plannera s evaluation demonstrates an optimization of an exemplary space mission. This research is based on the parallel development of theoretical concepts and practical solutions while working with three reconfigurable multi-robot teams. The operation of a reconfigurable robotic team comes with practical constraints. Therefore, this thesis composes and evaluates an operational infrastructure which can serve as reference implementation. The identification and combination of applicable state-of-the-art technologies result in a distributed and dynamically extensible communication infrastructure which can maintain the properties of reconfigurable multi-robot systems. Field tests covering semi-autonomous and autonomous operation have been performed to characterise multi-robot missions and validate the autonomous control approach for reconfigurable multi-robot systems. The practical evaluation identified critical constraints and design elements for a successful application of reconfigurable multi-robot systems. Furthermore, the experiments point to improvements for the organisation model. This thesis is a wholistic approach to automate reconfigurable multi-robot systems. It identifies theoretical as well as practical challenges and it suggests effective solutions which permit an exploitation of an increased level of flexibility in future robotics missions