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Hu, C., Hu, X. & Hong, Y. (2019). Distributed adaptive Kalman filter based on variational Bayesian technique. Control Theory and Technology, 17(1), 37-47
Open this publication in new window or tab >>Distributed adaptive Kalman filter based on variational Bayesian technique
2019 (English)In: Control Theory and Technology, ISSN 2095-6983, Vol. 17, no 1, p. 37-47Article in journal (Refereed) Published
Abstract [en]

In this paper, distributed Kalman filter design is studied for linear dynamics with unknown measurement noise variance, which modeled by Wishart distribution. To solve the problem in a multi-agent network, a distributed adaptive Kalman filter is proposed with the help of variational Bayesian, where the posterior distribution of joint state and noise variance is approximated by a free-form distribution. The convergence of the proposed algorithm is proved in two main steps: noise statistics is estimated, where each agent only use its local information in variational Bayesian expectation (VB-E) step, and state is estimated by a consensus algorithm in variational Bayesian maximum (VB-M) step. Finally, a distributed target tracking problem is investigated with simulations for illustration.

Place, publisher, year, edition, pages
South China University of Technology, 2019
Keywords
adaptive filter, Distributed Kalman filter, multi-agent system, variational Bayesian, Adaptive filtering, Kalman filters, Multi agent systems, Spurious signal noise, Target tracking, Adaptive kalman filter, Consensus algorithms, Distributed Kalman filters, Distributed target tracking, Multiagent networks, Posterior distributions, Wishart distribution, Adaptive filters
National Category
Mathematics
Identifiers
urn:nbn:se:kth:diva-248223 (URN)10.1007/s11768-019-8183-9 (DOI)2-s2.0-85060635596 (Scopus ID)
Note

QC 20190412

Available from: 2019-04-12 Created: 2019-04-12 Last updated: 2019-04-12Bibliographically approved
Zhang, S., Ringh, A., Hu, X. & Karlsson, J. (2018). A moment-based approach to modeling collective behaviors. In: 2018 IEEE Conference on Decision and Control (CDC): . Paper presented at 57th IEEE Conference on Decision and Control, CDC 2018; Centre of the Fontainebleau in Miami Beach Miami; United States; 17 December 2018 through 19 December 2018 (pp. 1681-1687). Institute of Electrical and Electronics Engineers (IEEE), Article ID 8619389.
Open this publication in new window or tab >>A moment-based approach to modeling collective behaviors
2018 (English)In: 2018 IEEE Conference on Decision and Control (CDC), Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 1681-1687, article id 8619389Conference paper, Published paper (Refereed)
Abstract [en]

In this work we introduce an approach for modeling and analyzing collective behavior of a group of agents using moments. We represent the occupation measure of the group of agents by their moments and show how the dynamics of the moments can be modeled. Then approximate trajectories of the moments can be computed and an inverse problem is solved to recover macro-scale properties of the group of agents. To illustrate the theory, a numerical example with interactions between the agents is given.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2018
Series
IEEE Conference on Decision and Control, ISSN 0743-1546
National Category
Computer Vision and Robotics (Autonomous Systems)
Identifiers
urn:nbn:se:kth:diva-245104 (URN)10.1109/CDC.2018.8619389 (DOI)000458114801093 ()2-s2.0-85062188079 (Scopus ID)978-1-5386-1395-5 (ISBN)
Conference
57th IEEE Conference on Decision and Control, CDC 2018; Centre of the Fontainebleau in Miami Beach Miami; United States; 17 December 2018 through 19 December 2018
Note

QC 20190307

Available from: 2019-03-07 Created: 2019-03-07 Last updated: 2019-03-07Bibliographically approved
Zhang, H. & Hu, X. (2018). Consensus control for linear systems with optimal energy cost. Automatica, 93, 83-91
Open this publication in new window or tab >>Consensus control for linear systems with optimal energy cost
2018 (English)In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 93, p. 83-91Article in journal (Refereed) Published
Abstract [en]

In this paper, we design an optimal energy cost controller for linear systems asymptotic consensus given the topology of the graph. The controller depends only on relative information of the agents. Since finding the control gain for such controller is hard, we focus on finding an optimal controller among a classical family of controllers which is based on Algebraic Riccati Equation (ARE) and guarantees asymptotic consensus. Through analysis, we find that the energy cost is bounded by an interval and hence we minimize the upper bound. In order to do that, there are two classes of variables that need to be optimized: the control gain and the edge weights of the graph and are hence designed from two perspectives. A suboptimal control gain is obtained by choosing Q=0 in the ARE. Negative edge weights are allowed, and the problem is formulated as a Semi-definite Programming (SDP) problem. Having negative edge weights means that “competitions” between the agents are allowed. The motivation behind this setting is to have a better system performance. We provide a different proof compared to Thunberg and Hu (2016) from the angle of optimization and show that the lowest control energy cost is reached when the graph is complete and with equal edge weights. Furthermore, two sufficient conditions for the existence of negative optimal edge weights realization are given. In addition, we provide a distributed way of solving the SDP problem when the graph topology is regular.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Consensus control, Distributed optimization, Multi-agent systems, Optimal control, Semi-definite programming
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-227534 (URN)10.1016/j.automatica.2018.03.044 (DOI)000436916200010 ()2-s2.0-85044478071 (Scopus ID)
Note

QC 20180521

Available from: 2018-05-21 Created: 2018-05-21 Last updated: 2019-01-21Bibliographically approved
Wang, L., Markdahl, J., Liu, Z. & Hu, X. (2018). Decentralized cooperative tracking subject to motion constraints. Automatica, 96, 121-126
Open this publication in new window or tab >>Decentralized cooperative tracking subject to motion constraints
2018 (English)In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 96, p. 121-126Article in journal (Refereed) Published
Abstract [en]

This paper addresses the formation control problem, where three agents are tasked with moving an object cooperatively along a desired trajectory while also adjusting its posture to some desired attitudes, i.e. position and attitude tracking. Two decentralized control laws based on locally available information are proposed. The first control law maintains constant inter-agent distances over time, i.e. the formation of agents moves as a single rigid-body. The second control law relaxes this constraint by only maintaining similarity of the agent formation as a polygon in Euclidean space. 

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keywords
Decentralized tracking, Formation control, Rigidity, Motion constraints, Attitude control
National Category
Computer and Information Sciences
Identifiers
urn:nbn:se:kth:diva-235562 (URN)10.1016/j.automatica.2018.06.037 (DOI)000444659500012 ()2-s2.0-85049475395 (Scopus ID)
Note

QC 20181001

Available from: 2018-10-01 Created: 2018-10-01 Last updated: 2018-10-01Bibliographically approved
Zhang, S., He, F. & Hu, X. (2018). Exponential Stability of Formations for Reduced Attitudes: A Coordinates Free Approach. In: Proceedings of Chinese Control Conference, 2018: . Paper presented at 37th Chinese Control Conference, CCC 2018; Wuhan; China; 25 July 2018 through 27 July 2018 (pp. 7220). IEEE Computer Society, Article ID 7215.
Open this publication in new window or tab >>Exponential Stability of Formations for Reduced Attitudes: A Coordinates Free Approach
2018 (English)In: Proceedings of Chinese Control Conference, 2018, IEEE Computer Society, 2018, p. 7220-, article id 7215Conference paper, Published paper (Refereed)
Abstract [en]

In this work, a methodology based on differential geometry techniques is proposed to investigate exponential stability of a formation for reduced attitudes. By the proposed method, there is no need in finding any relative coordinates, which is typically needed but shown to be difficult when the formation problem is evolving in a non-Euclidean space. In this paper, the desired formation is treated as an embedding submanifold in (S 2 ) N and by using the rotation symmetries owned by the attitude dynamics its stability is directly examined. Moreover, such a method turns out to be coordinates free, namely, exponential stability of a formation can be completely determined by just investigating anyone equilibrium which can result in the formation under any local chart of (S 2 ) N . This greatly simplifies the stability analysis for the formation problems.

Place, publisher, year, edition, pages
IEEE Computer Society, 2018
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-241260 (URN)10.23919/ChiCC.2018.8482861 (DOI)2-s2.0-85056133917 (Scopus ID)9789881563941 (ISBN)
Conference
37th Chinese Control Conference, CCC 2018; Wuhan; China; 25 July 2018 through 27 July 2018
Note

QC 20190117

Available from: 2019-01-17 Created: 2019-01-17 Last updated: 2019-01-21Bibliographically approved
Wei, J., Zhang, S., Adaldo, A., Johan, T., Hu, X. & Johansson, K. H. (2018). Finite-time attitude synchronization with distributed discontinuous protocols. IEEE Transactions on Automatic Control, 63(10), 3608-3615
Open this publication in new window or tab >>Finite-time attitude synchronization with distributed discontinuous protocols
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2018 (English)In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 63, no 10, p. 3608-3615Article in journal (Refereed) Published
Abstract [en]

The finite-time attitude synchronization problem is considered in this paper, where the rotation of each rigid body is expressed using the axis-angle representation. Two discontinuous and distributed controllers using the vectorized signum function are proposed, which guarantee almost global and local convergence, respectively. Filippov solutions and non-smooth analysis techniques are adopted to handle the discontinuities. Sufficient conditions are provided to guarantee finite-time convergence and boundedness of the solutions. Simulation examples are provided to verify the performances of the control protocols designed in this paper.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2018
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-227718 (URN)10.1109/TAC.2018.2797179 (DOI)000446331200043 ()2-s2.0-85040999383 (Scopus ID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research
Note

QC 20180523

Available from: 2018-05-11 Created: 2018-05-11 Last updated: 2018-10-30Bibliographically approved
Zhang, S., Song, W., He, F., Hong, Y. & Hu, X. (2018). Intrinsic tetrahedron formation of reduced attitude. Automatica, 87, 375-382
Open this publication in new window or tab >>Intrinsic tetrahedron formation of reduced attitude
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2018 (English)In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 87, p. 375-382Article in journal (Refereed) Published
Abstract [en]

In this paper, formation control for reduced attitude is studied, in which a regular tetrahedron formation can be achieved and shown to be asymptotically stable under a large family of gain functions in the control. Moreover, by further restriction on the control gain, almost global stability of the desired formation is obtained. In addition, the control proposed is an intrinsic protocol that only uses relative information and does not need to contain any information of the desired formation beforehand. The constructed formation pattern is totally attributed to the geometric properties of the space and the designed inter-agent connection topology. Besides, a novel coordinates transformation is proposed to represent the relative reduced attitudes in S2, which is shown to be an efficient approach to reduced attitude formation problems.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Attitude control, Distributed control, Formation control, Nonlinear systems
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-219636 (URN)10.1016/j.automatica.2017.10.023 (DOI)000423002400042 ()2-s2.0-85033383085 (Scopus ID)
Note

QC 20171211

Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2019-01-21Bibliographically approved
Deng, J., Wang, L., Liu, Z. & Hu, X. (2018). Pose Synchronization of Multiple Rigid Bodies Under Average Dwell Time Condition. Journal of Systems Science and Complexity, 31(1), 215-233
Open this publication in new window or tab >>Pose Synchronization of Multiple Rigid Bodies Under Average Dwell Time Condition
2018 (English)In: Journal of Systems Science and Complexity, ISSN 1009-6124, E-ISSN 1559-7067, Vol. 31, no 1, p. 215-233Article in journal (Refereed) Published
Abstract [en]

This paper considers the pose synchronization problem of a group of moving rigid bodies under switching topologies where the dwell time of each topology may has no nonzero lower bound. The authors introduce an average dwell time condition to characterize the length of time intervals in which the graphs are connected. By designing distributed control laws of angular velocity and linear velocity, the closed-loop dynamics of multiple rigid bodies with switching topologies can be converted into a hybrid dynamical system. The authors employ the Lyapunov stability theorem, and show that the pose synchronization can be reached under the average dwell time condition. Moreover, the authors investigate the pose synchronization problem of the leader-following model under a similar average dwell time condition. Simulation examples are given to illustrate the results.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2018
Keywords
Average dwell time, hybrid dynamical systems, pose synchronization, rigid body, SE(3)
National Category
Mathematics
Identifiers
urn:nbn:se:kth:diva-224707 (URN)10.1007/s11424-018-7379-2 (DOI)000426304800015 ()2-s2.0-85042732607 (Scopus ID)
Note

QC 20180323

Available from: 2018-03-23 Created: 2018-03-23 Last updated: 2018-03-23Bibliographically approved
Zhang, H., Wei, J., Yi, P. & Hu, X. (2018). Projected primal-dual gradient flow of augmented Lagrangian with application to distributed maximization of the algebraic connectivity of a network. Automatica, 98, 34-41
Open this publication in new window or tab >>Projected primal-dual gradient flow of augmented Lagrangian with application to distributed maximization of the algebraic connectivity of a network
2018 (English)In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 98, p. 34-41Article in journal (Refereed) Published
Abstract [en]

In this paper, a projected primal-dual gradient flow of augmented Lagrangian is presented to solve convex optimization problems that are not necessarily strictly convex. The optimization variables are restricted by a convex set with computable projection operation on its tangent cone as well as equality constraints. As a supplement of the analysis in Niederlander and Cortes (2016), we show that the projected dynamical system converges to one of the saddle points and hence finding an optimal solution. Moreover, the problem of distributedly maximizing the algebraic connectivity of an undirected network by optimizing the port gains of each nodes (base stations) is considered. The original semi-definite programming (SDP) problem is relaxed into a nonlinear programming (NP) problem that will be solved by the aforementioned projected dynamical system. Numerical examples show the convergence of the aforementioned algorithm to one of the optimal solutions. The effect of the relaxation is illustrated empirically with numerical examples. A methodology is presented so that the number of iterations needed to reach the equilibrium is suppressed. Complexity per iteration of the algorithm is illustrated with numerical examples.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Projected dynamical systems, Semi-definite programming, Distributed optimization
National Category
Computational Mathematics
Identifiers
urn:nbn:se:kth:diva-239468 (URN)10.1016/j.automatica.2018.09.004 (DOI)000449310900005 ()2-s2.0-8505380717 (Scopus ID)
Note

QC 20181126

Available from: 2018-11-26 Created: 2018-11-26 Last updated: 2019-01-21Bibliographically approved
Markdahl, J., Hoppe, J., Wang, L. & Hu, X. (2017). A geodesic feedback law to decouple the full and reduced attitude. Systems & control letters (Print), 102, 32-41
Open this publication in new window or tab >>A geodesic feedback law to decouple the full and reduced attitude
2017 (English)In: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 102, p. 32-41Article in journal (Refereed) Published
Abstract [en]

This paper presents a novel approach to the problem of almost global attitude stabilization. The reduced attitude is steered along a geodesic path on the n - 1-sphere. Meanwhile, the full attitude is stabilized on SO(n). This action, essentially two maneuvers in sequel, is fused into one smooth motion. Our algorithm is useful in applications where stabilization of the reduced attitude takes precedence over stabilization of the full attitude. A two parameter feedback gain affords further trade-offs between the full and reduced attitude convergence speed. The closed loop kinematics on SO(3) are solved for the states as functions of time and the initial conditions, providing precise knowledge of the transient dynamics. The exact solutions also help us to characterize the asymptotic behavior of the system such as establishing the region of attraction by straightforward evaluation of limits. The geometric flavor of these ideas is illustrated by a numerical example.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Attitude control, Reduced attitude, Geodesics, Exact solutions, Special orthogonal group
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-207709 (URN)10.1016/j.sysconle.2017.01.005 (DOI)000399862600005 ()2-s2.0-85012131906 (Scopus ID)
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note

QC 20170524

Available from: 2017-05-24 Created: 2017-05-24 Last updated: 2017-11-10Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0177-1993

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