Task-driven multi-formation control for coordinated UAV/UGV ISR missions

The report describes the development of a theoretical framework for coordination and control of combined teams of UAVs and UGVs for coordinated ISR missions. We consider the mission as a composition of an ordered sequence of subtasks, each to be performed by a different team. We design continuous cooperative controllers that enable each team to perform a given subtask and we develop a discrete strategy for interleaving the action of teams on different subtasks. The overall multi-agent coordination architecture is captured by a hybrid automaton, stability is studied using Lyapunov tools, and performance is evaluated through numerical simulations

Complex Networked Control Systems

This special section focuses on the study of network architectures and their formation as well as on the description of dynamical processes that take place over networks. A common thread throughout the five articles is the role of distributed processing and control, as well as the search for network-growth mechanisms that give rise to the desired structure and behavior

Information Surfing for Model-driven Radiation Mapping

In this report we develop a control scheme to coordinate a group of mobile sensors for radiation mapping of a given planar polygon region. The control algorithm is based on the concept of information surfing, where navigation is done by means of following information gradients, taking into account sensing performance as well as inter-robot communication range limitations. The control scheme provably steers mobile sensors to locations at which they maximize the information content of their measurement data, and the asymptotic properties of our information metric with respect to time ensures that no local information metric extremum traps the sensors indefinitely. In addition, the inherent synergy of the mobile sensor group facilitates the temporal erosion of such extremum configurations. Information surfing allows for reactive mobile sensor network behavior and adaptation to environmental changes, as well as human retasking

Increasing the Accuracy of Cooperative Localization by Controlling the Sensor Graph

We characterize the accuracy of a cooperative localization algorithm based on Kalman Filtering, as expressed by the trace of the covariance matrix, in terms of the algebraic graph theoretic properties of the sensing graph. In particular, we discover a weighted Laplacian in the expression that yields the constant, steady state value of the covariance matrix. We show how one can reduce the localization uncertainty by manipulating the eigenvalues of the weighted Laplacian. We thus provide insight to recent optimization results which indicate that increased connectivity implies higher accuracy and we offer an analysis method that could lead to more efficient ways of achieving the desired accuracy by controlling the sensing network

Simulation relations for discrete-time linear systems

Simulation relations of labeled transition systems are used in theoretical computer science in order to formally establish notions of modeling abstraction and refinement in hierarchical systems. In this paper, we establish and characterize simulation relations for arbitrary discrete-time, linear control systems. More precisely, given two discrete-time systems, we consider various embeddings into labeled transition systems, that differ in the amount of timing information that is maintained in the transition relation. For each embedding, we obtain necessary and sufficient conditions for one discrete-time system simulating the transitions of the other. Naturally, the simulation characterizations become weaker as more information is abstracted away in the embedding

Almost Global Asymptotic Formation Stabilization Using Navigation Functions

We present a navigation function through which a group of mobile agents can be coordinated to achieve a particular formation, both in terms of shape and orientation, while avoiding collisions between themselves and with obstacles in the environment. Convergence is global and complete, subject to the constraints of the navigation function methodology. Algebraic graph theoretic properties associated with the interconnection graph are shown to affect the shape of the navigation function. The approach is centralized but the potential function is constructed in a way that facilitates complete decentralization. The strategy presented will also serve as a point of reference and comparison in quantifying the cost of decentralization in terms of performance