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17
An overview of recent progress in the study of distributed multi-agent coordination
, 2012
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Distributed Control of Spacecraft Formation via Cyclic Pursuit: Theory and Experiments
"... Abstract — In this paper we study distributed control policies for spacecraft formations that draw inspiration from the simple idea of cyclic pursuit. First, we extend existing cyclicpursuit control laws devised for single-integrator models in two dimensions to the case of double-integrator models i ..."
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Abstract — In this paper we study distributed control policies for spacecraft formations that draw inspiration from the simple idea of cyclic pursuit. First, we extend existing cyclicpursuit control laws devised for single-integrator models in two dimensions to the case of double-integrator models in three dimensions. In particular, we develop control laws that only require relative measurements of position and velocity with respect to the two leading neighbors in the ring topology of cyclic pursuit, and allow the spacecraft to converge to a variety of symmetric formations, including evenly spaced circular formations and evenly spaced Archimedes ’ spirals. Second, we discuss potential applications, including spacecraft coordination for interferometric imaging and convergence to zero-effort orbits. Finally, we present and discuss experimental results obtained by implementing the aforementioned control laws on three nanospacecraft on board the International Space Station. I.
Distributed formation control without a global reference frame
- In American Control Conference (ACC), 2014
, 2014
"... Abstract—This paper presents a decentralized controller to drive a team of agents to reach a desired formation in the absence of a global reference frame. Each agent is able to measure its relative position and orientation with respect to its neighbors. The different orientations imply that the rela ..."
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Abstract—This paper presents a decentralized controller to drive a team of agents to reach a desired formation in the absence of a global reference frame. Each agent is able to measure its relative position and orientation with respect to its neighbors. The different orientations imply that the relative positions between pairs of agents are sensed differently for each agent. In order to reach the desired configuration, the agents run two simultaneous consensus controllers, one to control their relative orientations, and another for their relative positions. The convergence to the desired configuration is shown by comparing the system with time-varying orientations with the equivalent approach with fixed rotations, showing that their difference vanishes as time goes to infinity. While the analysis in the paper is performed in a 2-dimensional space with orientations belonging to SO(2), our approach can be extended to handle 3 dimensions and orientations in SO(3). Simulation results, as well as hardware experiments with two quadrotor UAVs, corroborate the theoretical findings of the paper. I.
Leader-Follower Formation via Complex Laplacian
, 2013
"... The paper introduces complex-valued Laplacians for graphs whose edges are attributed with complex weights and studies the leader-follower formation problem based on complex Laplacians. The main goal is to control the shape of a planar formation of point agents in the plane using simple and linear in ..."
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The paper introduces complex-valued Laplacians for graphs whose edges are attributed with complex weights and studies the leader-follower formation problem based on complex Laplacians. The main goal is to control the shape of a planar formation of point agents in the plane using simple and linear interaction rules related to complex Laplacians. We present a characterization of complex Laplacians that preserve a specic planar formation as an equilibrium solution for both single integrator kinematics and double integrator dynamics. Planar formations under study are subject to translation, rotation, and scaling in the plane, but can be determined by two co-leaders in leader-follower networks. Furthermore, when a complex Laplacian does not result in an asymptotically stable behavior of the multi-agent system, we show that a stabilizing matrix, which updates the complex weights, exists to asymptotically stabilize the system while preserving the equilibrium formation. Also, algorithms are provided to nd stabilizing matrices. Finally, simulations are presented to illustrate our results.
Swarm Splitting and Multiple Targets Seeking in Multi-Agent Dynamic Systems
"... Abstract — This paper presents an approach to swarm split control of a system of multi-agents with limited sensing capa-bilities. The control scheme utilizes the competition between the inter-agent repulsive and attractive interactions and can split one cohesive swarm into several clustered subswarm ..."
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Abstract — This paper presents an approach to swarm split control of a system of multi-agents with limited sensing capa-bilities. The control scheme utilizes the competition between the inter-agent repulsive and attractive interactions and can split one cohesive swarm into several clustered subswarms along the direction perpendicular to the common heading direction of agents. The cohesion and collision avoidance of agents are ensured by long-range attractive and short-range repulsive interactions between agents. The split of swarm is achieved via a Gaussian-like repulsive interaction between agents, whose magnitude affects the number of subswarm clusters and can be designed to control the swarm splitting/rejoining maneuver, and whose maximum location mainly affects the relative distance between clustered subswarms. The split control law is also applied to double targets seeking task in a swarm of 100 agents, and simulations are worked out. These results are of interest in understanding and utilizing the splitting dynamics in swarms of agents with local coupling interactions. I.
Leader-following Formation Control Based on Pursuit Strategies
"... Abstract-The paper studies formation control of multi-agent systems under a directed acyclic graph. In a directed acyclic graph, the agents without neighbors are leaders and the others are followers. Leaders move in a formation with a time-varying velocity and followers can access the relative posi ..."
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Abstract-The paper studies formation control of multi-agent systems under a directed acyclic graph. In a directed acyclic graph, the agents without neighbors are leaders and the others are followers. Leaders move in a formation with a time-varying velocity and followers can access the relative positions of their neighbors and the leaders' velocity. A local formation control law is proposed in the paper based on pursuit strategies and necessary and sufficient conditions for stability and convergence are derived. Moreover, the results are extended to the case with arbitrary communication delays, for which the steady-state formation is presented according both the control parameters and time delays.
State Feedback Consensus for Multi-Agent System with Multiple Time-Delays
"... Abstract—In this paper, we study the multi-agent system to achieve a faster consensus with multiple time-delays under a directed asymmetric information exchange topology. We first assume that an agent processes its own state information with self-delay and receives state information from its neighbo ..."
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Abstract—In this paper, we study the multi-agent system to achieve a faster consensus with multiple time-delays under a directed asymmetric information exchange topology. We first assume that an agent processes its own state information with self-delay and receives state information from its neighbors with communication delays. Based on state proportion derivative feedback, the improved consensus protocol can accelerate the system to achieve a consensus. A sufficient condition for reaching consensus is then derived based on the Nyquist stability criterion and frequency domain analysis. In addition, a specific form of consensus equilibrium is obtained which is influenced by the initial states of agents, time-delays and state feedback intensity. Finally, simulations are presented to verify the validity of the theoretical results.