Multi-Robot Coalition Formation for Distributed Area Coverage

The problem of distributed area coverage using multiple mobile robots is an important problem in distributed multi-robot sytems. Multi-robot coverage is encountered in many real world applications, including unmanned search & rescue, aerial reconnaissance, robotic demining, inspection of engineering structures, and automatic lawn mowing. To achieve optimal coverage, robots should move in an efficient manner and reduce repeated coverage of the same region that optimizes a certain performance metric such as the amount of time or energy expended by the robots. This dissertation especially focuses on using mini-robots with limited capabilities, such as low speed of the CPU and limited storage of the memory, to fulfill the efficient area coverage task. Previous research on distributed area coverage use offline or online path planning algorithms to address this problem. Some of the existing approaches use behavior-based algorithms where each robot implements simple rules and the interaction between robots manifests in the global objective of overall coverage of the environment. Our work extends this line of research using an emergent, swarming based technique where robots use partial coverage histories from themselves as well as other robots in their vicinity to make local decisions that attempt to ensure overall efficient area coverage. We have then extended this technique in two directions. First, we have integreated the individual-robot, swarming-based technique for area coverage to teams of robots that move in formation to perform area coverage more efficiently than robots that move individually. Then we have used a team formation technique from coalition game theory, called Weighted Voting Game (WVG) to handle situations where a team moving in formation while performing area coverage has to dynamically reconfigure into sub-teams or merge with other teams, to continue the area coverage efficiently. We have validated our techniques by testing them on accurate models of e-puck robots in the Webots robot simulation platform, as well as on physical e-puck robots

Algorithms for Modular Self-reconfigurable Robots: Decision Making, Planning, and Learning

Modular self-reconfigurable robots (MSRs) are composed of multiple robotic modules which can change their connections with each other to take different shapes, commonly known as configurations. Forming different configurations helps the MSR to accomplish different types of tasks in different environments. In this dissertation, we study three different problems in MSRs: partitioning of modules, configuration formation planning and locomotion learning, and we propose algorithmic solutions to solve these problems. Partitioning of modules is a decision-making problem for MSRs where each module decides which partition or team of modules it should be in. To find the best set of partitions is a NP-complete problem. We propose game theory based both centralized and distributed solutions to solve this problem. Once the modules know which set of modules they should team-up with, they self-aggregate to form a specific shaped configuration, known as the configuration formation planning problem. Modules can be either singletons or connected in smaller configurations from which they need to form the target configuration. The configuration formation problem is difficult as multiple modules may select the same location in the target configuration to move to which might result in occlusion and consequently failure of the configuration formation process. On the other hand, if the modules are already in connected configurations in the beginning, then it would be beneficial to preserve those initial configurations for placing them into the target configuration as disconnections and re-connections are costly operations. We propose solutions based on an auction-like algorithm and (sub) graph-isomorphism technique to solve the configuration formation problem. Once the configuration is built, the MSR needs to move towards its goal location as a whole configuration for completing its task. If the configuration’s shape and size is not known a priori, then planning its locomotion is a difficult task as it needs to learn the locomotion pattern in dynamic time – the problem is known as adaptive locomotion learning. We have proposed reinforcement learning based fault-tolerant solutions for locomotion learning by MSRs

Coalition Formation For Distributed Constraint Optimization Problems

This dissertation presents our research on coalition formation for Distributed Constraint Optimization Problems (DCOP). In a DCOP, a problem is broken up into many disjoint sub-problems, each controlled by an autonomous agent and together the system of agents have a joint goal of maximizing a global utility function. In particular, we study the use of coalitions for solving distributed k-coloring problems using iterative approximate algorithms, which do not guarantee optimal results, but provide fast and economic solutions in resource constrained environments. The challenge in forming coalitions using iterative approximate algorithms is in identifying constraint dependencies between agents that allow for effective coalitions to form. We first present the Virtual Structure Reduction (VSR) Algorithm and its integration with a modified version of an iterative approximate solver. The VSR algorithm is the first distributed approach for finding structural relationships, called strict frozen pairs, between agents that allows for effective coalition formation. Using coalition structures allows for both more efficient search and higher overall utility in the solutions. Secondly, we relax the assumption of strict frozen pairs and allow coalitions to form under a probabilistic relationship. We identify probabilistic frozen pairs by calculating the propensity between two agents, or the joint probability of two agents in a k-coloring problem having the same value in all satisfiable instances. Using propensity, we form coalitions in sparse graphs where strict frozen pairs may not exist, but there is still benefit to forming coalitions. Lastly, we present a cooperative game theoretic approach where agents search for Nash stable coalitions under the conditions of additively separable and symmetric value functions

Interaction dynamics and autonomy in cognitive systems

The concept of autonomy is of crucial importance for understanding life and cognition. Whereas cellular and organismic autonomy is based in the self-production of the material infrastructure sustaining the existence of living beings as such, we are interested in how biological autonomy can be expanded into forms of autonomous agency, where autonomy as a form of organization is extended into the behaviour of an agent in interaction with its environment (and not its material self-production). In this thesis, we focus on the development of operational models of sensorimotor agency, exploring the construction of a domain of interactions creating a dynamical interface between agent and environment. We present two main contributions to the study of autonomous agency: First, we contribute to the development of a modelling route for testing, comparing and validating hypotheses about neurocognitive autonomy. Through the design and analysis of specific neurodynamical models embedded in robotic agents, we explore how an agent is constituted in a sensorimotor space as an autonomous entity able to adaptively sustain its own organization. Using two simulation models and different dynamical analysis and measurement of complex patterns in their behaviour, we are able to tackle some theoretical obstacles preventing the understanding of sensorimotor autonomy, and to generate new predictions about the nature of autonomous agency in the neurocognitive domain. Second, we explore the extension of sensorimotor forms of autonomy into the social realm. We analyse two cases from an experimental perspective: the constitution of a collective subject in a sensorimotor social interactive task, and the emergence of an autonomous social identity in a large-scale technologically-mediated social system. Through the analysis of coordination mechanisms and emergent complex patterns, we are able to gather experimental evidence indicating that in some cases social autonomy might emerge based on mechanisms of coordinated sensorimotor activity and interaction, constituting forms of collective autonomous agency

Game Theory Relaunched

The game is on. Do you know how to play? Game theory sets out to explore what can be said about making decisions which go beyond accepting the rules of a game. Since 1942, a well elaborated mathematical apparatus has been developed to do so; but there is more. During the last three decades game theoretic reasoning has popped up in many other fields as well - from engineering to biology and psychology. New simulation tools and network analysis have made game theory omnipresent these days. This book collects recent research papers in game theory, which come from diverse scientific communities all across the world; they combine many different fields like economics, politics, history, engineering, mathematics, physics, and psychology. All of them have as a common denominator some method of game theory. Enjoy

The difference constitutions make: a global inquiry into the impacts of institutional design

This dissertation provides an international perspective on the problem of constitutional engineering. At its heart it is an assessment of the direction and magnitude of constitutional effects on the quality and robustness of government, taken from two major constitutional paradigms: that of constitutional regime types and that of inclusive-versus-exclusive democratic competitiveness. Constitutional performance is evaluated in terms of effects on measurements of governance across dimensions such as rule of law, social welfare and fiscal management, which are measured based on citizen perceptions and other aggregates. The analysis moves in four stages. First, an analysis of regime types treated endogenously. Second, an estimation of regime type effects on three dimensions of good governance. This is proceeded by another estimation exercise, this time on the regime type effects on fiscal management. Finally, there is an assessment of the social welfare effects of power-sharing institutions. I find evidence in favour of the hypothesis that alloy constitutional models attenuate the effects of presidentialism and parliamentarism. The presidential system is also found to perform well with respect to fiscal management. Power-sharing institutions generally have positive effects on social welfare but these remarks must be qualified by the extent to which power-sharing institutions tend toward rent-seeking and inefficiency, and by the extent to which under stronger controls, related to making national aggregates more commensurable, this evidence appears to dissolve

LIPIcs, Volume 244, ESA 2022, Complete Volume

LIPIcs, Volume 244, ESA 2022, Complete Volum

Tragedy of Confusion: The Political Economy of Truth in the modern history of Iran (A novel framework for the analysis of the enigma of socio-economic underdevelopment in the modern history of Iran)

This study entails a theoretical reading of the Iranian modern history and follows an interdisciplinary agenda at the intersection of philosophy, economics, and politics and intends to offer a novel framework for the analysis of socio-economic underdevelopment in Iran in the modern era. A brief review of Iranian modern history from the constitutional revolution, to the oil nationalization movement, the 1979 Islamic Revolution, and the recent Reformist and Green movements demonstrates that Iranian people travelled full circle. This historical experience of socio-economic underdevelopment revolving around the bitter question of “why are we backward?” and its manifestation in perpetual socio-political instability and violence is the subject matter of this study. Foucault’s conceived relation between the production of truth and production of wealth captures the essence of hypothesis offered in this study. Michel Foucault (1980: 93-4) maintains that “In the last analysis, we must produce truth as we must produce wealth, indeed we must produce truth in order to produce wealth in the first place”. Based on a hybrid methodology combining hermeneutics of understanding and hermeneutics of suspicion, this study proposes that the failure to produce wealth has had particular roots in the failure in the production of truth. At the heart of the proposed theoretical model is the following formula: The Iranian dasein’s confused preference structure culminates in the formation of unstable coalitions which in turn leads to institutional failure, creating a chaotic social order and a turbulent history as experienced by the Iranian nation in the modern era. The following set of interrelated propositions elaborate further on the core formula of the model: Each and every Iranian person and her subjectivity and preference structure is the site of three distinct warring regimes of truth and identity choice sets (identity markers) related to the ancient Persian empire (Persianism), Islam, and modernity. These three historical a priori and regimes of truth act as conditions of possibility for social interactions, and are unities in multiplicities. They, in their perpetual state of tension and conflict, constitute the mutually exclusive, contradictory, and confused dimensions of the prism of the Iranian dasein. The confused preference structure prevents Iranian people from organizing themselves in stable coalitions required for collective action to achieve the desired socio-economic change. The complex interplay between the state of inbetweenness and the state of belatedness makes it impossible to form stable coalitions in any areas of life, work, and language to achieve the desired social transformations, turning Iran into a country of unstable coalitions and alliances in macro, meso and micro levels. This in turn leads to failure in the construction of stable institutions (a social order based on rule of law or any other stable institutional structure becomes impossible) due to perpetual tension between alternative regimes of truth manifested in warring discursive formations, relations of power, and techniques of subjectification and their associated economies of affectivity. This in turn culminates in relations of power in all micro, meso, and macro levels to become discretionary, atomic, and unpredictable, producing perpetual tensions and social violence in almost all sites of social interactions, and generating small and large social earthquakes (crises, movements, and revolutions) as experienced by the Iranian people in their modern history. As such, the society oscillates between the chaotic states of socio-political anarchy emanating from irreconcilable differences between and within social assemblages and their affiliated hybrid forms of regimes of truth in the springs of freedom and repressive states of order in the winters of discontent. Each time, after the experience of chaos, the order is restored based on the emergence of a final arbiter (Iranian leviathan) as the evolved coping strategy for achieving conflict resolution. This highly volatile truth cycle produces the experience of socio-economic backwardness. The explanatory power of the theoretical framework offered in the study exploring the relation between the production of truth, trust and wealth is tested on three strong events of Iranian modern history: the Constitutional Revolution, the Oil-Nationalization Movement and the Islamic Revolution. The significant policy implications of the model are explored

Fragmentation and integration in Swiss water governance: Understanding a complex system through the study of organizational networks

This thesis undertakes a tour d'horizon of Swiss water governance. What can be said overall after it? In sum, three key insights stand out. These are the high potential for fragmentation among high-visibility, high-conflict issues surrounding agriculture, biodiversity and hydropower, the key integrative role of administrative agencies, especially on the cantonal level, and the essential role of local level implementation. All three articles in this thesis provide evidence that Swiss water governance has two distinct modes of operation in terms of visibility and conflict. On the one hand, a lot of water governance is "quiet politics'' related to the implementation and upkeep of water supply, waste water management and flood prevention measures and infrastructure. These areas are highly technical and relatively uncontroversial among the self-selecting set of actors involved. On the other hand, there is a second mode of more controversial issues, which are also more strongly reflected in media attention. At the heart of the matter lies the unwelcome fact that there are zero-sum games surrounding some water issues. Protecting aquatic biodiversity cannot avoid clashing with a reliance on agricultural methods based on pesticide use. Freeing up riverbeds and streams at some point comes at the cost of agricultural land. Large-scale hydropower concepts cannot be built outside of the landscape they are situated in and completely without impacting the dynamics of aquatic ecosystems. To overcome conflicts in these areas, administrative agencies have emphasized synergies to resolve the perception of zero-sum games. Revitalization projects are the prime example of this strategy. Arguments in favor of such projects sometimes go to great lengths in emphasizing how they do not only serve nature protection purposes, but can also improve flood prevention and increase the quality of life for residents by creating an inspiring landscape for recreational purposes. However, strategies of highlighting synergies can only go so far. Tellingly, many revitalization projects in Switzerland have tackled not necessarily areas where ecological improvements would have been maximized, but areas of least resistance, which in the Swiss context often means areas of a minimum amount of confrontation with agricultural interests. In the future, such areas will become more scarce. A key challenge for integration will thus relate to integrating agricultural organizations into the water governance system. In order to further improve the situation of aquatic habitats in Switzerland, any other way seems unrealistic. As agricultural interests are deeply entrenched within the political system, a more confrontational approach is only likely to lead to a stalemate and a patchwork of ecological improvement measures. Interestingly, also the first mode of operation in Swiss water governance, the more technocratic area of water supply and waste water management has been in more flux recently. It will need to find answers to the two key challenges of drought and micropollution in the future. Both require integration, sometimes involving an engagement with more controversial issues. How the challenges posed by increasing drought risks and micropollution are addressed in the future will thus be informative in order to judge the adaptive capacity of the Swiss water governance system, and the area of "quiet politics'' identified in this thesis will be crucial in this regard. There is good reason to be optimistic about this capacity for adaptation, not least due to the entrenched role of reputed cantonal level administrators and the presence of low-conflict local level networks within the areas of water supply and wastewater management. In overcoming fragmentation, cantonal level administrators emerge time and time again as a key player in Swiss water governance. They stand out as a hub connecting lower-level actors such as municipalities and regional service providers either to other lower-level actors or higher-level ones such as federal administrators. However, this thesis also shows that the networks of local level actors consisting of municipalities, service providers, and engineering and consulting firms are key in getting things done in the end. The studies assembled within this thesis indicate that they are part of distinct governance subsystems, integrate issues through their often generalist approaches to water governance within their territory, and show remarkable capacity for self-organization. The preceding three key points about Swiss water governance harbour theoretical insights for natural resource governance systems elsewhere. Much of natural resource governance is implementation and "quiet politics'', such as the water supply and flood control subsystems in Swiss water governance. In these non-adversarial areas, phenomena such as actor coalitions based on belief differences or "devil shifts'' are not likely to occur. Instead, as the regional water supply management network studied in the third article of this thesis shows, actors have a high capacity to organize and overcome fragmentation in such areas. In dealing with such subsystems, it thus seems advisable to establish conditions that retain a maximum amount of agency for organizations to self-organize. The most compelling argument for anarchy as a model for network governance thus somewhat ironically applies to cases where a degree of order in terms of a non-conflictive subsystem exists. Another general insight of this thesis is that integration comes in different forms. On the actor level, it can range from explicit coordination to providing bridges between different communities and access to outside knowledge. On an institutional level it can range from legislative, administrative or executive action, such as policy integration, to organizing venues for exchange, such as policy forums. If integration comes in different forms, the same can be said about fragmentation. Some of it is caused by the slow speed of adaption of a governance system to new challenges or lack of knowledge about relations between issues. Such fragmentation is easier to address. The more problematic kind of fragmentation has a root in more fundamental conflicts of values and interests. Setting up more institutional venues and disseminating knowledge can only go so far in overcoming it. In the end, there is no other legitimate and long-term effective way of resolving such fragmentation than the appropriate level of democratically legitimate debate and decision-making procedure. Social science based on complexity thinking can play an important role in this by informing debates and empowering actors based on an understanding of social systems appropriate to their nature