| 1. |
- Alexandre, Seuret, et al.
(författare)
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Consensus of Double Integrator Multi-agents under Communication Delay
- 2009
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - : Elsevier BV. - 1474-6670. ; , s. 376-381
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the consensus problem under network induced communication delays. It is well-known that introducing a delay generally leads to a reduce of the performance or to instability. Thus, investigating the impact of time-delays in the consensus problem is an important issue. Another important issue is to obtain an estimate of the convergence rate, which is not straightforward when delays appear in the network. In this paper, the agents are modelled as double integrator systems. It is assumed that each agent receives instantaneously its own output information but receives the information from its neighbors after a constant delay. A stability criterion is provided based on Lyapunov-Krasovskii techniques and is expressed in terms of LMI. An expression of the consensus equilibrium which depends on the delay and on the initial conditions taken in an interval is derived. The results are supported through several simulations for different network symmetric communication schemes.
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| 2. |
- Dimarogonas, Dimos V., et al.
(författare)
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A connection between formation infeasibility and velocity alignment in kinematic multi-agent systems
- 2008
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Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 44:10, s. 2648-2654
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a feedback control strategy that achieves convergence of a multi-agent system to a desired formation configuration is proposed for both the cases of agents with single integrator and nonholonomic unicycle-type kinematics. When inter-agent objectives that specify the desired formation cannot occur simultaneously in the state space the desired formation is infeasible. it is shown that under certain assumptions, formation infeasibility forces the agents' velocity vectors to a common value at steady state. This provides a connection between formation infeasibility and flocking behavior for the multi-agent system. We finally also obtain an analytic expression of the common velocity vector in the case of formation infeasibility.
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| 3. |
- Dimarogonas, Dimos V., et al.
(författare)
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An inverse agreement control strategy with application to swarm dispersion
- 2007
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Ingår i: PROCEEDINGS OF THE 46TH IEEE CONFERENCE ON DECISION AND CONTROL. ; , s. 3824-3829
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Konferensbidrag (refereegranskat)abstract
- We propose an inverse agreement control strategy for multiple kinematic agents that forces the team members to disperse in the workspace in a distributed manner. Both the cases of an unbounded and a cyclic, bounded workspace are considered. In the first case, we show that the closed loop system reaches a configuration in which the minimum distance between any pair of agents is larger than a specific lower bound. It is proved that this lower bound coincides with the agents' sensing radius. In the case of a bounded cyclic workspace, the control law is redefined in order to force the agents to remain within the workspace boundary throughout the closed loop system evolution. Moreover the proposed control design guarantees collision avoidance between the team members in both cases. The results are supported through relevant computer simulations.
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| 4. |
- Dimarogonas, Dimos V., et al.
(författare)
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Analysis of robot navigation schemes using Rantzer's Dual Lyapunov Theorem
- 2008
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Ingår i: 2008 AMERICAN CONTROL CONFERENCE. ; , s. 201-206
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Konferensbidrag (refereegranskat)abstract
- When robots are driven by the negative gradient of a potential field that consists of the sum of an attractive and a repulsive term, convergence to the desired configuration cannot be guaranteed by traditional Lyapunov techniques. In this paper, sufficient conditions for convergence of such systems are provided instead with the use of Rantzer's Dual Lyaptinov Theorem. In particular, a condition that involves the trace of the Hessian matrix of the potential function is derived and then applied to the cases of navigation of a single robot and of multi-robot formation stabilization. The main result of the paper states that a sufficient condition for convergence to a desired configuration in both cases is that the attractive potential admits a sufficiently large gain. A lower bound on the attractive potential is computed. Computer simulations that support the new results are provided.
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| 5. |
- Dimarogonas, Dimos V., et al.
(författare)
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Connectedness Preserving Distributed Swarm Aggregation for Multiple Kinematic Robots
- 2008
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Ingår i: IEEE Transactions on robotics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1552-3098 .- 1941-0468. ; 24:5, s. 1213-1223
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Tidskriftsartikel (refereegranskat)abstract
- A distributed swarm aggregation algorithm is developed for a team of multiple kinematic agents. Specifically, each agent is assigned a control law, which is the sum of two elements: a repulsive potential field, which is responsible for the collision avoidance objective, and an attractive potential field, which forces the agents to converge to a configuration where they are close to each other. Furthermore, the attractive potential field forces the agents that are initially located within the sensing radius of an agent to remain within this area for all time. In this way, the connectivity properties of the initially formed communication graph are rendered invariant for the trajectories of the closed-loop system. It is shown that under the proposed control law, agents converge to a configuration where each agent is located at a bounded distance from each of its neighbors. The results are also extended to the case of nonholonomic kinematic unicycle-type agents and to the case of dynamic edge addition. In the latter case, we derive a smaller bound in the swarm size than in the static case.
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| 6. |
- Dimarogonas, Dimos V., et al.
(författare)
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Connectivity preserving distributed swarm aggregation for multiple kinematic agents
- 2007
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Ingår i: PROCEEDINGS OF THE 46TH IEEE CONFERENCE ON DECISION AND CONTROL. - 9781424414987 ; , s. 3627-3632
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Konferensbidrag (refereegranskat)abstract
- A distributed swarm aggregation algorithm is developed for a team of multiple kinematic agents. Each agent is assigned with a control law which is the sum of two elements: a repulsive potential field, which is responsible for the collision avoidance objective, and an attractive potential field, that drives the agents to a configuration where they are close to each other and forces the agents that are initially located within the sensing radius of an agent to remain within this area for all time. In this way, the connectivity properties of the initially formed communication graph are rendered invariant for the trajectories of the closed loop system. It is shown that agents converge to a configuration where each agent is located at a bounded distance from each of its neighbors. The results are also extended to the case of nonholonomic kinematic agents and to the dynamic edge addition case, for which we derive a better bound in the swarm size than in the static case.
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| 7. |
- Dimarogonas, Dimos V., et al.
(författare)
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Decentralized connectivity maintenance in mobile networks with bounded inputs
- 2008
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Ingår i: 2008 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION. ; , s. 1507-1512
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Konferensbidrag (refereegranskat)abstract
- A distributed control law that guarantees connectivity maintenance in a network of multiple mobile agents is presented. The control law respects the limited sensing capabilities of the agents by allowing each agent to take into account only agents within its sensing radius in the controller implementation. In contrast to previous approaches to the problem, the proposed control law does not attain infinite values whenever an edge tends to be lost, and is therefore a bounded distributed control law. This is achieved via the use of decentralized navigation functions which are potential fields with guaranteed boundedness and are redefined in this paper in order to take into account the connectivity maintenance objective. We first treat the case of connectivity maintenance in a static initial position based communication graph and extend the results to the case of dynamic edge addition. The results are then applied to a formation control problem.
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| 8. |
- Dimarogonas, Dimos V., et al.
(författare)
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Event-triggered control for multi-agent systems
- 2009
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Ingår i: Proceedings of the IEEE Conference on Decision and Control. - 9781424438716 ; , s. 7131-7136
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Konferensbidrag (refereegranskat)abstract
- Event-driven strategies for multi-agent systems are motivated by the future use of embedded microprocessors with limited resources that will gather information and actuate the individual agent controller updates. The control actuation updates considered in this paper are event-driven, depending on the ratio of a certain measurement error with respect to the norm of a function of the state, and are applied to a first order agreement problem. A centralized formulation of the problem is considered first and then the results are extended to the decentralized counterpart, in which agents require knowledge only of the states of their neighbors for the controller implementation.
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| 9. |
- Dimarogonas, Dimos V., et al.
(författare)
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Further results on formation infeasibility and velocity alignment
- 2007
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Ingår i: PROCEEDINGS OF THE 46TH IEEE CONFERENCE ON DECISION AND CONTROL. ; , s. 4115-4120
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Konferensbidrag (refereegranskat)abstract
- In previous work, we deduced that formation infeasibility results in velocity alignment in multi-agent systems with bidirectional communication topology and single integrator as well as nonholonomic kinematics. This paper contains additional results regarding the connection between formation infeasibility and velocity alignment. In particular, we obtain an analytic expression for the resulting common velocity vector in the case of formation infeasibility and extend the results to the case of unidirectional communication topology. The results are then extended to the case of a leader-follower architecture in which the followers are not aware of a global objective while the leaders are responsible for driving the team to the interior of a desired leader formation. When this formation is infeasible, we show that both leaders and followers attain a common velocity vector, of which an analytic expression is also provided. Computer simulations support the derived results.
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| 10. |
- Dimarogonas, Dimos V., et al.
(författare)
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Further results on the stability of distance-based multi-robot formations
- 2009
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Ingår i: 2009 AMERICAN CONTROL CONFERENCE, VOLS 1-9. - 9781424445233 ; , s. 2972-2977
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Konferensbidrag (refereegranskat)abstract
- An important class of multi-robot formations is specified by desired distances between adjacent robots. In previous work, we showed that distance-based formations can be globally stabilized by negative gradient, potential field based, control laws, if and only if the formation graph is a tree. In this paper, we further examine the relation between the cycle space of the formation graph and the resulting equilibria of cyclic formations. In addition, the results are extended to the case of distance based formation control for nonholonomic agents. The results are supported through computer simulations.
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