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240
Distributed coordinated tracking with reduced interaction via a variable structure approach
 IEEE Trans. Autom. Control
, 2011
"... Abstract—A distributed coordinated tracking problem is solved via a variable structure approach when there exists a dynamic virtual leader who is a neighbor of only a subset of a group of followers, all followers have only local interaction, and only partial measurements of the states of the virtual ..."
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Cited by 20 (3 self)
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Abstract—A distributed coordinated tracking problem is solved via a variable structure approach when there exists a dynamic virtual leader who is a neighbor of only a subset of a group of followers, all followers have only local interaction, and only partial measurements of the states of the virtual leader and the followers are available. In the context of coordinated tracking, we focus on both consensus tracking and swarm tracking algorithms. In the case of firstorder kinematics, we propose a distributed consensus tracking algorithm without velocity measurements under both fixed and switching network topologies. In particular, we show that distributed consensus tracking can be achieved in finite time. The algorithm is then extended to achieve distributed swarm tracking without velocity measurements. In the case of secondorder dynamics, we first propose two distributed consensus tracking algorithms without acceleration measurements when the velocity of the virtual leader is varying under, respectively, a fixed and switching network topology. In particular, we show that the proposed algorithms guarantee at least global exponential tracking. We then propose a distributed consensus tracking algorithm and a distributed swarm tracking algorithm when the velocity of the virtual leader is constant. When the velocity of the virtual leader is varying, distributed swarm tracking is solved by using a distributed estimator. For distributed consensus tracking, a mild connectivity requirement is proposed by adopting an adaptive connectivity maintenance mechanism in which the adjacency matrix is defined in a proper way. Similarly, a mild connectivity requirement is proposed for distributed swarm tracking by adopting a connectivity maintenance mechanism in which the potential function is defined in a proper way. Several simulation examples are presented as a proof of concept. Index Terms—Consensus tracking, cooperative control, distributed control, multiagent systems, swarm tracking, variable structure approach. I.
Consensus of multiagent networks in the presence of adversaries using only local information
 HICONS'12
, 2012
"... This paper addresses the problem of resilient consensus in the presence of misbehaving nodes. Although it is typical to assume knowledge of at least some nonlocal information when studying secure and faulttolerant consensus algorithms, this assumption is not suitable for largescale dynamic network ..."
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Cited by 17 (5 self)
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This paper addresses the problem of resilient consensus in the presence of misbehaving nodes. Although it is typical to assume knowledge of at least some nonlocal information when studying secure and faulttolerant consensus algorithms, this assumption is not suitable for largescale dynamic networks. To remedy this, we emphasize the use of local strategies to deal with resilience to security breaches. We study a consensus protocol that uses only local information and we consider worstcase security breaches, where the compromised nodes have full knowledge of the network and the intentions of the other nodes. We provide necessary and sufficient conditions for the normal nodes to reach consensus despite the influence of the malicious nodes under different threat assumptions. These conditions are stated in terms of a novel graphtheoretic property referred to as network robustness.
Collective motion from consensus with Cartesian coordinate coupling—Part i: Singleintegrator kinematics & part ii: Doubleintegrator dynamics
 in Proc. IEEE Conf. Decision Control, Cancun
, 2008
"... Abstract—Collective motions including rendezvous, circular patterns, and logarithmic spiral patterns can be achieved by introducing Cartesian coordinate coupling to existing consensus algorithms. We study the collective motions of a team of vehicles in 3D by introducing a rotation matrix to an exi ..."
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Cited by 17 (1 self)
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Abstract—Collective motions including rendezvous, circular patterns, and logarithmic spiral patterns can be achieved by introducing Cartesian coordinate coupling to existing consensus algorithms. We study the collective motions of a team of vehicles in 3D by introducing a rotation matrix to an existing consensus algorithm for doubleintegrator dynamics. It is shown that the network topology, the damping gain, and the value of the Euler angle all affect the resulting collective motions. We show that when the nonsymmetric Laplacian matrix has certain properties, the damping gain is above a certain bound, and the Euler angle is below, equal, or above a critical value, the vehicles will eventually rendezvous, move on circular orbits, or follow logarithmic spiral curves lying on a plane perpendicular to the Euler axis. In particular, when the vehicles eventually move on circular orbits, the relative radii of the orbits (respectively, the relative phases of the vehicles on their orbits) are equal to the relative magnitudes (respectively, the relative phases) of the components of a right eigenvector associated with a critical eigenvalue of the nonsymmetric Laplacian matrix. Simulation results are presented to demonstrate the theoretical results. Index Terms—Collective motion, consensus, cooperative control, distributed algorithms, multivehicle systems. I.
Distributed coordinated tracking with a dynamic leader for multiple Euler–Lagrange systems
 IEEE TRANSACTIONS ON AUTOMATIC CONTROL
, 2011
"... In this note, we study a distributed coordinated tracking problem for multiple networked Euler–Lagrange systems. The objective is for a team of followers modeled by fullactuated Euler–Lagrange equations to track a dynamic leader whose vector of generalized coordinates is time varying under the con ..."
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Cited by 15 (1 self)
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In this note, we study a distributed coordinated tracking problem for multiple networked Euler–Lagrange systems. The objective is for a team of followers modeled by fullactuated Euler–Lagrange equations to track a dynamic leader whose vector of generalized coordinates is time varying under the constraints that the leader is a neighbor of only a subset of the followers and the followers have only local interaction. We consider two cases: i) The leader has a constant vector of generalized coordinate derivatives, and ii) The leader has a varying vector of generalized coordinate derivatives. In the first case, we propose a distributed continuous estimator and an adaptive control law to account for parametric uncertainties. In the second case, we propose a modelindependent sliding mode control algorithm. Simulation results on multiple networked twolink revolute joint arms are provided to show the effectiveness of the proposed control algorithms.
Consensus tracking under directed interaction topologies: Algorithms and experiments
 IEEE Transactions on Control Systems Technology
, 2010
"... Abstract — Consensus tracking problems with, respectively, bounded control effort and directed switching interaction topologies are considered when a timevarying consensus reference state is available to only a subgroup of a team. A consensus tracking algorithm explicitly accounting for bounded co ..."
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Cited by 14 (5 self)
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Abstract — Consensus tracking problems with, respectively, bounded control effort and directed switching interaction topologies are considered when a timevarying consensus reference state is available to only a subgroup of a team. A consensus tracking algorithm explicitly accounting for bounded control effort is proposed and analyzed under a fixed directed interaction topology. Furthermore, convergence analysis for a consensus tracking algorithm is provided when the timevarying consensus reference state is available to a dynamically changing subgroup of the team under directed switching intervehicle interaction topologies. Experimental results of a formation control application are demonstrated on a multirobot platform to validate one of the proposed consensus tracking algorithms. I.
Resilient asymptotic consensus in robust networks
 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS
, 2013
"... This paper addresses the problem of resilient innetwork consensus in the presence of misbehaving nodes. Secure and faulttolerant consensus algorithms typically assume knowledge of nonlocal information; however, this assumption is not suitable for largescale dynamic networks. To remedy this, we foc ..."
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Cited by 13 (6 self)
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This paper addresses the problem of resilient innetwork consensus in the presence of misbehaving nodes. Secure and faulttolerant consensus algorithms typically assume knowledge of nonlocal information; however, this assumption is not suitable for largescale dynamic networks. To remedy this, we focus on local strategies that provide resilience to faults and compromised nodes. We design a consensus protocol based on local information that is resilient to worstcase security breaches, assuming the compromised nodes have full knowledge of the network and the intentions of the other nodes. We provide necessary and sufficient conditions for the normal nodes to reach asymptotic consensus despite the influence of the misbehaving nodes under different threat assumptions. We show that traditional metrics such as connectivity are not adequate to characterize the behavior of such algorithms, and develop a novel graphtheoretic property referred to as network robustness. Network robustness formalizes the notion of redundancy of direct information exchange between subsets of nodes in the network, and is a fundamental property for analyzing the behavior of certain distributed algorithms that use only local information.
Attitude Synchronization of a Group of Spacecraft Without Velocity Measurements
"... Abstract—We consider the coordinated attitude control problem for a group of spacecraft, without velocity measurements. Our approach is based on the introduction of auxiliary dynamical systems (playing the role of velocity observers in a certain sense) to generate the individual and relative damping ..."
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Abstract—We consider the coordinated attitude control problem for a group of spacecraft, without velocity measurements. Our approach is based on the introduction of auxiliary dynamical systems (playing the role of velocity observers in a certain sense) to generate the individual and relative damping terms in the absence of the actual angular velocities and relative angular velocities. Our main focus, in this technical note, is to address the following two problems: 1) Design a velocityfree attitude tracking and synchronization control scheme, that allows the team members to align their attitudes and track a timevarying reference trajectory (simultaneously). 2) Design a velocityfree synchronization control scheme, in the case where no reference attitude is specified, and all spacecraft are required to reach a consensus by aligning their attitudes with the same final timevarying attitude. In this work, one important and novel feature (besides the nonrequirement of the angular velocity measurements), consists in the fact that the control torques are naturally bounded and the designer can arbitrarily assign the desired bounds on the control torques, a priori, through the control gains, regardless of the angular velocities. Throughout this technical note, the communication flow between spacecraft is assumed to be undirected. Simulation results of a scenario of four spacecraft are provided to show the effectiveness of the proposed control schemes. Index Terms—Attitude synchronization, attitude tracking, consensus, output feedback, spacecraft. I.
Synchronization in Complex Networks of Phase Oscillators: A Survey
, 2014
"... The emergence of synchronization in a network of coupled oscillators is a fascinating subject of multidisciplinary research. This survey reviews the vast literature on the theory and the applications of complex oscillator networks. We focus on phase oscillator models that are widespread in realworl ..."
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The emergence of synchronization in a network of coupled oscillators is a fascinating subject of multidisciplinary research. This survey reviews the vast literature on the theory and the applications of complex oscillator networks. We focus on phase oscillator models that are widespread in realworld synchronization phenomena, that generalize the celebrated Kuramoto model, and that feature a rich phenomenology. We review the history and the countless applications of this model throughout science and engineering. We justify the importance of the widespread coupled oscillator model as a locally canonical model and describe some selected applications relevant to control scientists, including vehicle coordination, electric power networks, and clock synchronization. We introduce the reader to several synchronization notions and performance estimates. We propose analysis approaches to phase and frequency synchronization, phase balancing, pattern formation, and partial synchronization. We present the sharpest known results about synchronization in networks of homogeneous and heterogeneous oscillators, with complete or sparse interconnection topologies, and in finitedimensional and infinitedimensional settings. We conclude by summarizing the limitations of existing analysis methods and by highlighting some directions for future research.