Person:

Egerstedt, Magnus B.

Permanent Link

https://hdl.handle.net/1853/72204

Associated Organization(s)

Organizational Unit

School of Electrical and Computer Engineering

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Now showing 1 - 10 of 17

Observability and Controllability Verification in Multi-Agent Systems through Decentralized Laplacian Spectrum Estimation

(Georgia Institute of Technology, 2010-12) Franceschelli, Mauro ; Martini, Simone ; Egerstedt, Magnus B. ; Bicchi, Antonio ; Giua, Alessandro

In this paper we show how the decentralized estimation of the spectrum of a network can be used to infer its controllability and observability properties. The proposed approach is applied to networked multi-agent systems whose local interaction rule is based on Laplacian feedback. We provide a decentralized necessary and sufficient condition for observability and controllability based on the estimated eigenvalues. Furthermore we show an example of application of the proposed method and show that the estimated spectrum can also be envisioned as a tool for decentralized formation identification.
Geometric Foraging Strategies in Multi-Agent Systems Based on Biological Models

(Georgia Institute of Technology, 2010-12) Haque, Musad A. ; Rahmani, Amir R. ; Egerstedt, Magnus B.

In nature, communal hunting is often performed by predators by charging through an aggregation of prey. However, it has been noticed that variations exist in the geometric shape of the charging front; in addition, distinct differences arise between the shapes depending on the particulars of the feeding strategy. For example, each member of a dolphin foraging group must contribute to the hunt and will only be able to eat what it catches. On the other hand, some lions earn a "free lunch" by feigning help and later feasting on the prey caught by the more skilled hunters in the foraging group. We model the charging front of the predators as a curve moving through a prey density modeled as a reaction-diffusion process and we optimize the shape of the charging front in both the free lunch and no-free-lunch cases. These different situations are simulated under a number of varied types of predator-prey interaction models, and connections are made to multi-agent robot systems.
Controllability of Homogeneous Single-Leader Networks

(Georgia Institute of Technology, 2010-12) Egerstedt, Magnus B. ; Martini, Simone ; Twu, Philip Y.

This paper addresses an aspect of controllability in a single-leader network when the agents are homogeneous. In such a network, indices are not assigned to the individual agents and controllability, which is typically a point to point property, now becomes a point to set property, where the set consists of all permutations of the target point. Agent homogeneity allows for choice of the optimal target point permutation that minimizes the distance to the system's reachable subspace, which we show is equivalent to finding a minimum sum-of-squares clustering with constraints on the cluster sizes. However, finding the optimal permutation is NP-hard. Methods are presented to find suboptimal permutations in the general case and the optimal permutation when the agent positions are 1-D.
Battery Level Estimation of Mobile Agents Under Communication Constraints

(Georgia Institute of Technology, 2010-06) Kim, Jonghoek ; Zhang, Fumin ; Egerstedt, Magnus B.

Consider a team of mobile agents monitoring large areas, e.g. in the ocean or the atmosphere, with limited sensing resources. Only the leader transmits information to other agents, and the leader has a role to monitor battery levels of all other agents. Every now and then, the leader commands all other agents to move toward or away from the leader with speeds proportional to their battery levels. The leader then simultaneously estimates the battery levels of all other agents from measurements of the relative distances between the leader and other agents. We propose a nonlinear system model that integrates a particle motion model and a dynamic battery model that has demonstrated high accuracy in battery capacity prediction. The extended Kalman filter (EKF) is applied to this nonlinear model to estimate the battery level of each agent. We improve the EKF so that, in addition to gain optimization embedded in the EKF, the motions of agents are controlled to minimize estimation error. Simulation results are presented to demonstrate effectiveness of the proposed method.
Human-in-the-Loop: Terminal Constraint Receding Horizon Control with Human Inputs

(Georgia Institute of Technology, 2010-05) Chipalkatty, Rahul ; Egerstedt, Magnus B.

This paper presents a control theoretic formulation and optimal control solution for integrating human control inputs subject to linear state constraints. The formulation utilizes a receding horizon optimal controller to update the control effort given the most recent state and human control input information. The novel solution to the corresponding finite horizon optimal control problem with terminal constraint is derived using Hilbert space methods. The control laws are applied to two planar human-driven mass-cart pendula, where the task is to synchronize the pendula's oscillations.
Optimal Motion Primitives for Multi-UAV Convoy Protection

(Georgia Institute of Technology, 2010-05) Rahmani, Amir R. ; Ding, Xu Chu ; Egerstedt, Magnus B.

In this paper we study the problem of controlling a number of Unmanned Aerial Vehicles (UAVs) to provide convoy protection to a group of ground vehicles. The UAVs are modeled as Dubins vehicles flying at a constant altitude with bounded turning radius. This paper first presents time-optimal paths for providing convoy protection to static ground vehicles. Then this paper addresses paths and control strategies to provide convoy protection to ground vehicles moving on a straight line. Minimum numbers of UAVs required to provide perpetual convoy protection for both cases are derived.
Rendezvous with Multiple, Intermittent Leaders

(Georgia Institute of Technology, 2009-12) Notarstefano, Giuseppe ; Egerstedt, Magnus B. ; Haque, Musad A.

In this paper we study bipartite, first order-networks where the nodes take on leader or follower roles. In particular, we let the leaders' positions be static and assume that they are only intermittently visible to the followers. This is an assumption that is inspired by the way female silkworm moths only intermittently release pheromones to be detected by the males. The main result in this paper states that if the followers execute the linear agreement protocol, they will converge to the convex hull spanned by the leaders (may they be visible or not).
An exploration strategy by constructing Voronoi Diagrams with provable completeness

(Georgia Institute of Technology, 2009-12) Kim, Jonghoek ; Zhang, Fumin ; Egerstedt, Magnus B.

We present novel exploration algorithms and a control law that enable the construction of Voronoi diagrams over unknown areas using a single autonomous vehicle equipped with range sensors. Our control law and exploration algorithms are provably complete. The control law uses range measurements to enable tracking Voronoi edges between two obstacles. Exploration algorithms make decisions at vertices of the Voronoi diagram to expand the explored area until a complete Voronoi diagram is constructed in finite time. MATLAB simulation results are provided to demonstrate the effectiveness of both the control law and the exploration algorithms.
On the Number of Leaders Needed to Ensure Network Connectivity in Arbitrary Dimensions

(Georgia Institute of Technology, 2009-06) Gustavi, Tove ; Dimarogonas, Dimos V. ; Egerstedt, Magnus B. ; Hu, Xiaoming

We examine the leader-to-follower ratio needed to maintain connectivity in a leader-follower multi-agent network with proximity based communication topology. The paper extends the one-dimensional results of [2] to the two dimensional case. In the scenario we consider, only the leaders are aware of the global mission, which is to converge to a known destination point. Thus, the objective of the leaders is to drag the team to the desired goal. In the paper we obtain bounds on the number of leaders needed to complete the task. The results are first established for an initially complete communication graph and then extended to the incomplete case. Computer simulations support the derived theory.
A Switching Active Sensing Strategy to Maintain Observability for Vision-Based Formation Control

(Georgia Institute of Technology, 2009-05) Mariottini, Gian Luca ; Martini, Simone ; Egerstedt, Magnus B.

Vision-based control of a robot formation is challenging because the on-board sensor (camera) only provides the view-angle to the other moving robots, but not the distance that must be estimated. In order to guarantee a consistent estimate of the distance by knowing the control inputs and the sensor outputs in a given interval, the nonlinear multi-robot system must preserve its observability. Recent theoretical studies on leader-follower robot formation exploit the interesting influence that the control actions have on observability. Based on these results, in this paper we present a switching active control strategy for formation control. Our control strategy is active in the sense that, while asymptotically achieving the formation control tasks, it also guarantees the system observability in those cases in which all the robots tend to move along non-observable paths. As a result, both estimation and formation performances are improved. Extensive simulation results show the effectiveness of the proposed design.