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Egerstedt, Magnus B.

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    Automatic Deployment and Formation Control of Decentralized Multi-Agent Networks
    (Georgia Institute of Technology, 2008-05) Smith, Brian Stephen ; Howard, Ayanna M. ; Egerstedt, Magnus B.
    Novel tools are needed to deploy multi-agent networks in applications that require a high degree of accuracy in the achievement and maintenance of geometric formations. This is the case when deploying distributed sensing devices across large spatial domains. Through so-called embedded graph grammars (EGGs), this paper develops a method for automatically generating control programs that ensure that a multi-robot network is deployed according to the desired configuration. This paper presents a communication protocol needed for implementing and executing the control programs in an accurate and deadlock-free manner.
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    Optimal Control of Hybrid Systems with Regional Dynamics
    (Georgia Institute of Technology, 2007-08-23) Schöllig, Angela
    In this work, hybrid systems with regional dynamics are considered. These are systems where transitions between different dynamical regimes occur as the continuous state of the system reaches given switching surfaces. In particular, the attention is focused on the optimal control problem associated with such systems. More precisely, given a specific cost function, the goal is to determine the optimal path of going from a given starting point to a fixed final state during an a priori specified time horizon. The key characteristic of the approach presented in this thesis is a hierarchical decomposition of the hybrid optimal control problem, yielding to a framework which allows a solution on different levels of control. On the highest level of abstraction, the regional structure of the state space is taken into account and a discrete representation of the connections between the different regions provides global accessibility relations between regions. These are used on a lower level of control to formulate the main theorem of this work, namely, the Hybrid Bellman Equation for multimodal systems, which, in fact, provides a characterization of global optimality, given an upper bound on the number of transitions along a hybrid trajectory. Not surprisingly, the optimal solution is hybrid in nature, in that it depends on not only the continuous control signals, but also on discrete decisions as to what domains the system's continuous state should go through in the first place. The main benefit with the proposed approach lies in the fact that a hierarchical Dynamic Programming algorithm can be used to representing both a theoretical characterization of the hybrid solution's structural composition and, from a more application-driven point of view, a numerically implementable calculation rule yielding to globally optimal solutions in a regional dynamics framework. The operation of the recursive algorithm is highlighted by the consideration of numerous examples, among them, a heterogeneous multi-agent problem.
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    Realization of the Sensor Web Concept for Earth Science Using Mobile Robotic Platforms
    (Georgia Institute of Technology, 2007-03) Howard, Ayanna M. ; Smith, Brian Stephen ; Egerstedt, Magnus B.
    In this paper, we discuss the realization of a robotic mobile sensor network that allows for controlled reconfiguration of sensor assets in a decentralized manner. The motivation is to allow the construction of a new system of in-situ science observations that requires higher spatial and temporal resolution models that are needed for expanding our understanding of Earth system change. These observations could enable recording of spatial and temporal variations in environmental parameters required for such activities as monitoring of seismic activity, monitoring of civil and engineering infrastructures, and detection of toxic agents throughout a region of interest. The difficulty in establishing these science observations are that global formation properties must be achieved based on the local interactions between individual sensors. As such, we present a novel approach that allows for the sensor network to function in a decentralized manner and is thus able to achieve global formations despite individual sensor failure, limitations in communication range, and changing scientific objectives. Details on the sensing and control algorithms for controlled reconfiguration will be discussed and results of field deployment will be presented.