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  • 601. Xia, W.
    et al.
    Meng, Z.
    Shi, G.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Optimal tradeoff between instantaneous and delayed neighbor information in consensus algorithms2017Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 83, s. 116-123Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider a distributed consensus problem over a network, where at each time instant every node receives two pieces of information from disjoint neighboring sets: a weighted average of current states of neighbors from a primary network, and a weighted average of one-hop delayed states of neighbors from a secondary network. The proposed algorithm makes each node update its state to a weighted average of these individual averages. We show that convergence to consensus is guaranteed with non-trivial weights. We also present an explicit formula for the weights allocated to each piece of the information for the optimal rate of convergence, when the secondary network is the complement of the primary network. Finally numerical examples are given to explore the case when the neighbor sets of the agents do not cover the whole network.

  • 602.
    Xia, Weiguo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Cao, Ming
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Structural balance and opinion separation in trust–mistrust social networks2016Inngår i: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 3, nr 1, s. 46-56Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Structural balance theory has been developed in sociology and psychology to explain how interacting agents, e.g., countries, political parties, opinionated individuals, with mixed trust and mistrust relationships evolve into polarized camps. Recent results have shown that structural balance is necessary for polarization in networks with fixed, strongly connected neighbor relationships when the opinion dynamics are described by DeGroot-type averaging rules. We develop this line of research in this paper in two steps. First, we consider fixed, not necessarily strongly connected, neighbor relationships. It is shown that if the network includes a strongly connected subnetwork containing mistrust, which influences the rest of the network, then no opinion clustering is possible when that subnetwork is not structurally balanced; all the opinions become neutralized in the end. In contrast, it is shown that when that subnetwork is indeed structurally balanced, the agents of the subnetwork evolve into two polarized camps and the opinions of all other agents in the network spread between these two polarized opinions. Second, we consider time-varying neighbor relationships. We show that the opinion separation criteria carry over if the conditions for fixed graphs are extended to joint graphs. The results are developed for both discrete-time and continuous-time models.

  • 603.
    Xia, Weiguo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Liu, J.
    Cao, M.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Basar, T.
    Products of generalized stochastic Sarymsakov matrices2016Inngår i: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2016, s. 3621-3626Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the set of stochastic, indecomposable, aperiodic (SIA) matrices, the class of stochastic Sarymsakov matrices is the largest known subset (i) that is closed under matrix multiplication and (ii) the infinitely long left-product of the elements from a compact subset converges to a rank-one matrix. In this paper, we show that a larger subset with these two properties can be derived by generalizing the standard definition for Sarymsakov matrices. The generalization is achieved either by introducing an SIA index, whose value is one for Sarymsakov matrices, and then looking at those stochastic matrices with larger SIA indices, or by considering matrices that are not even SIA. Besides constructing a larger set, we give sufficient conditions for generalized Sarymsakov matrices so that their products converge to rank-one matrices. The new insight gained through studying generalized Sarymsakov matrices and their products has led to a new understanding of the existing results on consensus algorithms and will be helpful for the design of network coordination algorithms.

  • 604. Xia, Weiguo
    et al.
    Liu, Ji
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Basar, Tamer
    Convergence Rate of the Modified DeGroot-Friedkin Model with Doubly Stochastic Relative Interaction Matrices2016Inngår i: 2016 AMERICAN CONTROL CONFERENCE (ACC), IEEE conference proceedings, 2016, s. 1054-1059Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In a recent paper [1], a modified DeGroot-Friedkin model was proposed to study the evolution of the social-confidence levels of individuals in a reflected appraisal mechanism in which a network of n individuals consecutively discuss a sequence of issues. The individuals update their self-confidence levels on one issue in finite time steps, via communicating with their neighbors, instead of waiting until the discussion on the previous issue reaches a consensus, while the neighbor relationships are described by a static relative interaction matrix. This paper studies the same modified DeGroot-Friedkin model, but with time-varying interactions which are characterized by a sequence of doubly stochastic matrices. It is shown that, under appropriate assumptions, the n individuals' self-confidence levels will all converge to 1 n exponentially fast. An explicit expression of the convergence rate is provided.

  • 605. Xia, Weiguo
    et al.
    Shi, Guodong
    Meng, Ziyang
    Cao, Ming
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Balance Conditions in Discrete-Time Consensus Algorithms2017Inngår i: 2017 IEEE 56TH ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We study the consensus problem of discrete-time systems under persistent flow and non-reciprocal interactions between agents. An arc describing the interaction strength between two agents is said to be persistent if its weight function has an infinite l(1) norm. We discuss two balance conditions on the interactions between agents which generalize the arc-balance and cut-balance conditions in the literature respectively. The proposed conditions require that such a balance should be satisfied over each time window of a fixed length instead of at each time instant. We prove that in both cases global consensus is reached if and only if the persistent graph, which consists of all the persistent arcs, contains a directed spanning tree. The convergence rates are also provided in terms of the number of node interactions that have taken place.

  • 606.
    Xia, Weiguo
    et al.
    Dalian Univ Technol, Sch Control Sci & Engn, Dalian 116023, Peoples R China..
    Shi, Guodong
    Univ Sydney, Sch Aerosp Mech & Mechatron Engn, Australian Ctr Field Robot, Sydney, NSW 2008, Australia.;Australian Natl Univ, Res Sch Engin, Canberra, ACT 0200, Australia..
    Meng, Ziyang
    Tsinghua Univ, Dept Precis Instrument, State Key Lab Precis Measurement Technol & Instru, Beijing 100084, Peoples R China..
    Cao, Ming
    Univ Groningen, Engn & Technol Inst Groningen, Fac Sci & Engn, NL-9712 Groningen, Netherlands..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Persis en Flows in Deterministic Chains2019Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 64, nr 7, s. 2766-2781Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper studies, the role of persistent flows in the convergence of infinite backward products of stochastic matrices of deterministic chains over networks with nonreciprocal interactions between agents. An arc describing the interaction strength between two agents is said to be persistent if its weight function has an infinite l(1) norm; convergence of the infinite backward products to a rank-one matrix of a deterministic chain of stochastic matrices is equivalent to achieving consensus at the node states. We discuss two balance conditions on the interactions between agents, which generalize the arc-balance and cut-balance conditions in the literature, respectively. The proposed conditions require that such a balance should be satisfied over each time window of a fixed length instead of at each time instant. We prove that in both cases global consensus is reached if and only if the persistent graph, which consists of all the persistent arcs, contains a directed spanning tree. The convergence rates of the system to consensus are also provided in terms of the interactions between agents having taken place. The results are obtained under a weak condition without assuming the existence of a positive lower bound of all the nonzero weights of arcs and are compared with the existing results. Illustrative examples are provided to validate the results and show the critical importance of the nontrivial lower boundedness of the self-confidence of the agents.

  • 607. Yang, T.
    et al.
    Meng, Z.
    Shi, G.
    Hong, Y.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Network synchronization with nonlinear dynamics and switching interactions2016Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 61, nr 10, s. 3103-3108, artikkel-id 7317753Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This technical note considers the synchronization problem for networks of coupled nonlinear dynamical systems under switching communication topologies. Two types of nonlinear agent dynamics are considered. The first one is non-expansive dynamics [stable dynamics with a convex Lyapunov function φ(·)] and the second one is dynamics that satisfies a global Lipschitz condition. For the non-expansive case, we show that various forms of joint connectivity for communication graphs are sufficient for networks to achieve global asymptotic φ-synchronization. We also show that φ-synchronization leads to state synchronization provided that certain additional conditions are satisfied. For the globally Lipschitz case, unlike the non-expansive case, joint connectivity alone is not sufficient for achieving synchronization. A sufficient condition for reaching global exponential synchronization is established in terms of the relationship between the global Lipschitz constant and the network parameters. © 2015 IEEE.

  • 608.
    Yang, Tao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Meng, Ziyang
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Periodic Behaviors for Discrete-Time Second-Order Multiagent Systems With Input Saturation Constraints2016Inngår i: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 63, nr 7, s. 663-667Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This brief considers the existence of periodic behaviors for discrete-time second-order multiagent systems with input saturation constraints. We first consider the case where the agent dynamics is a double integrator and then establish conditions on the feedback gains of the linear consensus control law for achieving periodic behaviors. This, in turn, shows that the previously established sufficient condition for reaching global consensus has a necessary aspect since these two conditions are exclusive. We further consider all other second-order agent dynamics and show that these multiagent systems under the linear consensus law exhibit periodic solutions provided the feedback gains satisfy certain conditions. Simulation results are used to validate the theoretical findings.

  • 609.
    Yang, Tao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Meng, Ziyang
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Global consensus for discrete-time multi-agent systems with input saturation constraints2014Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 50, nr 2, s. 499-506Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the global consensus problem for discrete-time multi-agent systems with input saturation constraints under fixed undirected topologies. We first give necessary conditions for achieving global consensus via a distributed protocol based on relative state measurements of the agent itself and its neighboring agents. We then focus on two special cases, where the agent model is either neutrally stable or a double integrator. For the neutrally stable case, any linear protocol of a particular form, which solves the consensus problem for the case without input saturation constraints, also solves the global consensus problem for the case with input saturation constraints. For the double integrator case, we show that a subset of linear protocols, which solve the consensus problem for the case without saturation constraints, also solve the global consensus problem for the case with input saturation constraints. The results are illustrated by numerical simulations.

  • 610.
    Yang, Tao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Meng, Ziyang
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Global consensus in homogeneous networks of discrete-time agents subject to actuator saturation2013Inngår i: 2013 European Control Conference, ECC 2013, IEEE , 2013, s. 244-249Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we give necessary conditions for achieving global consensus in homogeneous networks of discrete-time linear time-invariant agents with input saturation constraints under fixed undirected topologies. For two special cases, where the agent model is either neutrally stable or a double integrator, these necessary conditions together with a gain condition are also sufficient. We show this by designing a linear protocol based on the combination of state differences between the agent and its neighbors. In particular, for the neutrally stable case, we show that any linear protocol of a particular form which solves the consensus problem for the case without input saturation constraints also solves the global consensus problem for the case with input saturation constraints. For the double integrator case, we show that a subset of linear protocols which solve the consensus problem for the case without saturation constraints also solve the global consensus problem in the presence of input saturation. The results are illustrated by numerical simulations.

  • 611.
    Yang, Tao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Meng, Ziyang
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Periodic behaviors in multi-agent systems with input saturation constraints2013Inngår i: 2013 IEEE 52nd Annual Conference on Decision and Control (CDC), IEEE conference proceedings, 2013, s. 4467-4472Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we give conditions for the existence of periodic behaviors in a multi-agent system of identical discrete-time double integrators with input saturation constraints. If the feedback gain parameters of the controllers, which are based on relative state measurements of the agent itself and its neighboring agents, are bounded by a value depending on the largest eigenvalue of the Laplacian matrix, then the multi-agent system exhibits a periodic solution for certain initial conditions.

  • 612.
    Yang, Tao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Meng, Ziyang
    Ren, Wei
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Synchronization of Coupled Nonlinear Dynamical Systems: Interplay Between Times of Connectivity and Integral of Lipschitz Gain2016Inngår i: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 63, nr 4, s. 391-395Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This brief considers the synchronization problem of coupled nonlinear dynamical systems over time-varying interaction graphs. We first show that infinite joint connectivity is necessary for achieving globally asymptotic synchronization. We then show that the commonly used Lipschitz condition on the nonlinear self-dynamics is not sufficient to ensure synchronization even for an arbitrarily large coupling strength. A sufficient synchronization condition is established in terms of the times of connectivity, the integral of the Lipschitz gain, and the network parameters.

  • 613. Yang, Tao
    et al.
    Meng, Ziyang
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Shi, Guodong
    Hong, Yiguang
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Synchronization for multi-agent systems under directed switching topologies2015Inngår i: Proceedings of the World Congress on Intelligent Control and Automation (WCICA), IEEE conference proceedings, 2015, nr March, s. 3473-3480Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the synchronization problem for a network of state diffusive coupled agents with identical but time-varying dynamics under switching communication topologies. Both leader-follower and leaderless networks are studied. For leader-follower networks, sufficient conditions are established regarding the connectivity of communication graphs for the network to achieve global exponential or asymptotic synchronization, respectively, for directed and undirected communications. For leaderless networks, sufficient conditions for asymptotic norm synchronization are established, respectively, for directed and undirected communications, in the sense that the norm of agents' states converges to a common value. We also show that if the communication graph is fixed, norm synchronization leads to state synchronization. The results reveal some important similarities and differences between leaderless and leader-follower networks for synchronization under directed switching communication graphs.

  • 614.
    Yang, Tao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Stoorvogel, A. A.
    Saberi, A.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Further results on saturated globally stabilizing linear state feedback control laws for single-input neutrally stable planar systems2013Inngår i: 2013 European Control Conference, ECC 2013, IEEE , 2013, s. 2728-2733Konferansepaper (Fagfellevurdert)
    Abstract [en]

    It is known that for single-input neutrally stable planar systems, there exists a class of saturated globally stabilizing linear state feedback control laws. The goal of this paper is to characterize the dynamic behavior for such a system under arbitrary locally stabilizing linear state feedback control laws. On the one hand, for the continuous-time case, we show that all locally stabilizing linear state feedback control laws are also globally stabilizing control laws. On the other hand, for the discrete-time case, we first show that this property does not hold by explicitly constructing nontrivial periodic solution for a particular system. We then show for an example that there exists more globally stabilizing linear state feedback control laws than well known ones in the literature.

  • 615. Yang, Tao
    et al.
    Wu, Di
    Ren, Wei
    Wang, Hong
    Hong, Yiguang
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Cooperative Optimal Coordination for Distributed Energy Resources2017Inngår i: 2017 IEEE 56TH ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2017, s. 6334-6339Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the optimal coordination problem for distributed energy resources (DERs) including distributed generators and energy storage devices. We propose an algorithm based on the push-sum and gradient method to optimally coordinate distributed generators and storage devices in a distributed manner. In the proposed algorithm, each DER only maintains a set of variables and updates them through information exchange with a few neighbors over a time-varying directed communication network. We show that the proposed distributed algorithm solves the optimal DER coordination problem if the time-varying directed communication network is uniformly jointly strongly connected, which is a mild condition on the connectivity of communication topologies. The proposed distributed algorithm is illustrated and validated by numerical simulations.

  • 616.
    Yang, Tao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Yuan, Ye
    Li, Kezhi
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Goncalves, J.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Finite-time road grade computation for a vehicle platoon2014Inngår i: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2014, nr February, s. 6105-6110Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Given a platoon of vehicles traveling uphill, this paper considers the finite-time road grade computation problem. We propose a decentralized algorithm for an arbitrarily chosen vehicle to compute the road grade in a finite number of time-steps by using only its own successive velocity measurements. Simulations then illustrate the theoretical results. These new results can be applied to real-world vehicle platooning problems to reduce fuel consumption and carbon dioxide emissions.

  • 617.
    Yi, Xinlei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Liu, Kun
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Distributed Dynamic Event-Triggered Control for Multi-Agent Systems2017Inngår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, IEEE, 2017, s. 6683-6688Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose two distributed dynamic triggering laws to solve the consensus problem for multi-agent systems with event-triggered control. Compared with existing triggering laws, the proposed triggering laws involve internal dynamic variables which play an essential role to guarantee that the triggering time sequence does not exhibit Zeno behavior. Some existing triggering laws are special cases of our dynamic triggering laws. Under the condition that the underlying graph is undirected and connected, it is proven that the proposed dynamic triggering laws together with the event-triggered control make the state of each agent converges exponentially to the average of the agents’ initial states. Numerical simulations illustrate the effectiveness of the theoretical results and show that the dynamic triggering laws lead to reduction of actuation updates and inter-agent communications.

  • 618.
    Yi, Xinlei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Wei, Jieqiang
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Formation Control for Multi-Agent Systems with Connectivity Preservation and Event-Triggered Controllers2017Inngår i: IFAC-PapersOnLine, ISSN 1045-0823, E-ISSN 1797-318X, Vol. 50, nr 1, s. 9367-9373Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, event-triggered controllers and corresponding algorithms are proposed to establish the formation with connectivity preservation for multi-agent systems. Each agent needs to update its control input and to broadcast this control input together with the relative state information to its neighbors at its own triggering times, and to receive information at its neighbors' triggering times. Two types of system dynamics, single integrators and double integrators, are considered. As a result, all agents converge to the formation exponentially with connectivity preservation, and Zeno behavior can be excluded. Numerical simulations show the effectiveness of the theoretical results.

  • 619.
    Yi, Xinlei
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Yang, Tao
    Univ North Texas, Dept Elect Engn, Denton, TX 76203 USA..
    Wu, Junfeng
    Zhejiang Univ, Coll Control Sci & Engn, Hangzhou 310027, Zhejiang, Peoples R China..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Distributed event-triggered control for global consensus of multi-agent systems with input saturation2019Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 100, s. 1-9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The global consensus problem for first-order continuous-time multi-agent systems with input saturation is considered. In order to reduce the overall need of communication and system updates, we propose an event-triggered consensus protocol and a triggering law, which do not require any a priori knowledge of global network parameters. It is shown that Zeno behavior is excluded for these systems and that the underlying directed graph having a directed spanning tree is a necessary and sufficient condition for global consensus. We use a new Lyapunov function to show the sufficient condition and it inspires the triggering law. Numerical simulations are provided to illustrate the effectiveness of the theoretical results.

  • 620.
    Yi, Xinlei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Yang, Tao
    Wu, Junfeng
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Event-Triggered Control for Multi-Agent Systems with Output Saturation2017Inngår i: 2017 36th Chinese Control Conference (CCC), IEEE Computer Society, 2017, s. 8431-8436, artikkel-id 8028693Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose distributed static and dynamic event-triggered control laws to solve the consensus problem for multiagent systems with output saturation. Under the condition that the underlying graph is undirected and connected, we show that consensus is achieved under both event-triggered control laws if and only if the average of the initial states is within the saturation level. Numerical simulations are provided to illustrate the effectiveness of the theoretical results and to show that the control laws lead to reduced need for inter-agent communications.

  • 621.
    Yi, Xinlei
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Yao, Lisha
    Univ North Texas, Dept Elect Engn, Denton, TX 76203 USA..
    Yang, Tao
    Univ North Texas, Dept Elect Engn, Denton, TX 76203 USA..
    George, Jemin
    US Army Res Lab, Adelphi, MD 20783 USA..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Distributed Optimization for Second-Order Multi-Agent Systems with Dynamic Event-Triggered Communication2018Inngår i: 2018 IEEE CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2018, s. 3397-3402Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we propose a fully distributed algorithm for second-order continuous-time multi-agent systems to solve the distributed optimization problem. The global objective function is a sum of private cost functions associated with the individual agents and the interaction between agents is described by a weighted undirected graph. We show the exponential convergence of the proposed algorithm if the underlying graph is connected, each private cost function is locally gradient-Lipschitz- continuous, and the global objective function is restricted strongly convex with respect to the global minimizer. Moreover, to reduce the overall need of communication, we then propose a dynamic event-triggered communication mechanism that is free of Zeno behavior. It is shown that the exponential convergence is achieved if the private cost functions are also globally gradient-Lipschitz- continuous. Numerical simulations are provided to illustrate the effectiveness of the theoretical results.

  • 622.
    Yoo, Jaehyun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Learning communication delay patterns for remotely controlled UAV networks2017Inngår i: IFAC PAPERSONLINE, Elsevier, 2017, Vol. 50, nr 1, s. 13216-13221Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper deals with collaborative unmanned aerial vehicles (UAVs) that are remotely controlled from a cloud server. The main contribution is to apply machine learning technique to find a pattern of network-induced effects on maneuvers of UAVs, in order to compensate for time delays and packet losses in remote communication. As machine learning technique, a Gaussian process (GP) based approach is employed due to its computational simplicity and flexibility in modelling complex expressions using a small number of parameters. We combine a deterministic compensation for an enhanced GP model to overcome a problem of the lack of training data at the beginning of training phase. This is done by defining training data input as a set of delayed observation and the deterministic compensation term, and by training the GP on residual between the true state and the input set. The proposed algorithm is evaluated to collaborative trajectory tracking of two UAVs. Simulations are performed for various delays and tracking scenarios. It is shown that the better tracking results are achieved compared to a conventional linear compensation algorithm.

  • 623.
    Yoo, Jaehyun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Semi-Supervised Learning for Mobile Robot Localization using Wireless Signal Strengths2017Inngår i: 2017 INTERNATIONAL CONFERENCE ON INDOOR POSITIONING AND INDOOR NAVIGATION (IPIN), 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper proposes a new semi-supervised machine learning for localization. It improves localization efficiency by reducing efforts needed to calibrate labeled training data by using unlabeled data, where training data come from received signal strengths of a wireless communication link. The main idea is to treat training data as spatio-temporal data. We compare the proposed algorithm with the state-of-art semi-supervised learning methods. The algorithms are evaluated for estimating the unknown location of a smartphone mobile robot. The experimental results show that the developed learning algorithm is the most accurate and robust to the varying amount of training data, without sacrificing the computation speed.

  • 624.
    Yoo, Jaehyun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kim, Hyoun Jin
    Indoor Localization Without a Prior Map by Trajectory Learning From Crowdsourced Measurements2017Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 66, nr 11, s. 2825-2835Artikkel i tidsskrift (Fagfellevurdert)
  • 625.
    Yoo, Jaehyun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kim, H. Jin
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Mapless Indoor Localization by Trajectory Learning from a Crowd2016Inngår i: 2016 INTERNATIONAL CONFERENCE ON INDOOR POSITIONING AND INDOOR NAVIGATION (IPIN), Institute of Electrical and Electronics Engineers (IEEE), 2016, artikkel-id 7743685Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper suggests a mapless indoor localization using wifi received signal strength (RSS) of a smartphone, collected by multiple people. A new trajectory learning algorithm by combining a dynamic time warping and a machine learning technique is proposed in order to generate an alternative map. Moreover, we combine particle filter and Gaussian process (GP) for the position estimation, because it can use the alternative map as the probabilistic function (the prior), and can use probabilistic relationship (the likelihood) between wifi RSSs and location. Field experimental results confirm the usefulness of our algorithm when the map is not available and robustness against outliers, in that the accuracy of the proposed localization is similar to that using the true map information.

  • 626.
    Yoo, Jaehyun
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Lee, Seungjae
    Seoul Natl Univ, Dept Mech & Aerosp Engn, Seoul, South Korea..
    Kim, H. Jin
    Seoul Natl Univ, Dept Mech & Aerosp Engn, Seoul, South Korea..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Trajectory generation for networked UAVs using online learning for delay compensation2017Inngår i: 1st Annual IEEE Conference on Control Technology and Applications, CCTA 2017, IEEE, 2017, s. 1941-1946Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a trajectory generation mechanism based on machine learning for a network of unmanned aerial vehicles (UAVs). For delay compensation, we apply an online regression technique to learn a pattern of network-induced effects on UAV maneuvers. Due to online learning, the control system not only adapts to changes to the environment, but also maintains a fixed amount of training data. The proposed algorithm is evaluated on a collaborative trajectory tracking task for two UAVs. Improved tracking is achieved in comparison to a conventional linear compensation algorithm.

  • 627.
    Yoo, Jaehyun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES). KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Molin, Adam
    Jafarian, Matin
    KTH, Skolan för teknikvetenskaplig kommunikation och lärande (ECE). KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Esen, Hasan
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Event-triggered Model Predictive Control with Machine Learning for Compensation of Model Uncertainties2017Inngår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 5463-5468Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As one of the extensions of model predictive control (MPC), event-triggered MPC takes advantage of the reduction of control updates. However, approaches to event-triggered MPCs may be subject to frequent event-triggering instants in the presence of large disturbances. Motivated by this, this paper suggests an application of machine learning to this control method in order to learn a compensation model for disturbance attenuation. The suggested method improves both event-triggering policy efficiency and control accuracy compared to previous approaches to event-triggered MPCs. We employ the radial basis function (RBF) kernel based machine learning technique. By the universial approximation property of the RBF, which imposes an upper bound on the training error, we can present the stability analysis of the learningaided control system. The proposed algorithm is evaluated by means of position control of a nonholonomic robot subject to state-dependent disturbances. Simulation results show that the developed method yields not only two times less event triggering instants, but also improved tracking performance.

  • 628. Zareh, M.
    et al.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Franceschelli, M.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Seatzu, C.
    Consensus in multi-agent systems with non-periodic sampled-data exchange and uncertain network topology2014Inngår i: Proceedings - 2014 International Conference on Control, Decision and Information Technologies, CoDIT 2014, 2014, s. 411-416Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper consensus in second-order multi-agent systems with a non-periodic sampled-data exchange among agents is investigated. The sampling is random with bounded inter-sampling intervals. It is assumed that each agent has exact knowledge of its own state at any time instant. The considered local interaction rule is PD-type. Sufficient conditions for stability of the consensus protocol to a time-invariant value are derived based on LMIs. Such conditions only require the knowledge of the connectivity of the graph modeling the network topology. Numerical simulations are presented to corroborate the theoretical results.

  • 629. Zareh, M.
    et al.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Franceschelli, M.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Seatzu, C.
    Consensus in multi-agent systems with second-order dynamics and non-periodic sampled-data exchange2014Inngår i: 19th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2014, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper consensus in second-order multi-agent systems with a non-periodic sampled-data exchange among agents is investigated. The sampling is random with bounded inter-sampling intervals. It is assumed that each agent has exact knowledge of its own state at all times. The considered local interaction rule is PD-type. The characterization of the convergence properties exploits a Lyapunov-Krasovskii functional method, sufficient conditions for stability of the consensus protocol to a time-invariant value are derived. Numerical simulations are presented to corroborate the theoretical results.

  • 630. Zhang, Fan
    et al.
    Xia, Weiguo
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Trentelman, Harry L.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Scherpen, Jacquelien M. A.
    Robust synchronization of directed Lur'e networks with incremental nonlinearities2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we deal with robust synchronization problems for directed Lur'e networks subject to incrementally passive nonlinearities and incrementally sector bounded non-linearities, respectively. By making use of general algebraic connectivities of strongly connected graphs and subgraphs, sufficient synchronization conditions are obtained for diffusively interconnected identical Lur'e systems on both the strongly connected interconnection topology and the topology containing a directed spanning tree. The static feedback gain matrices are determined by the matrices defining the individual agent dynamics and the general algebraic connectivities. The synchronization criteria obtained in the present paper extend those for undirected Lur'e networks in our previous work.

  • 631. Zhang, J.
    et al.
    Johansson, Karl H.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Lygeros, J.
    Sastry, S.
    Zeno hybrid systems2001Inngår i: International Journal of Robust and Nonlinear Control, ISSN 1049-8923, E-ISSN 1099-1239, Vol. 11, nr 5, s. 435-451Artikkel i tidsskrift (Fagfellevurdert)
  • 632. Zhang, Jun
    et al.
    Johansson, Karl Henrik
    Lygeros, John
    Sastry, Shankar
    Dynamical systems revisited: Hybrid systems with Zeno executions2000Inngår i: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, Vol. 1790, s. 451-464Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Results from classical dynamical systems are generalized to hybrid dynamical systems. The concept of omega limit set is introduced for hybrid systems and is used to prove new results on invariant sets and stability, where Zeno and non-Zeno hybrid systems can be treated within the same framework. As an example, LaSalle's Invariance Principle is extended to hybrid systems. Zeno hybrid systems are discussed in detail. The omega limit set of a Zeno execution is characterized for classes of hybrid systems.

  • 633.
    Zhang, Kuize
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Efficient observability verification for large-scale boolean control networks2018Inngår i: 2018 37th Chinese Control Conference (CCC), IEEE Computer Society, 2018, s. 560-567Konferansepaper (Fagfellevurdert)
    Abstract [en]

    It is known that verifying observability of Boolean control networks (BCNs) is NP-hard in the number of nodes. In this paper, we use a node aggregation approach to overcome the computational complexity in verifying observability for networks with special structures. First, we define a class of network node aggregations with compatible observability. It is proven for this class of aggregations, the whole BCN being observable does not imply that all corresponding subnetworks are observable, and vice versa. Second, when the aggregations are acyclic, we prove that all corresponding subnetworks being observable implies that the overall BCN is observable, although the converse is not true. Third, we show that finding acyclic aggregations with small subnetworks can tremendously reduce the computational complexity in verifying observability. Finally, we use a BCN T-cell receptor kinetics model from the literature with 37 state nodes and 3 input nodes to illustrate the efficiency of these results. For this model, we derive the unique minimal set of 16 state nodes needed to be observed to make the overall BCN observable.

  • 634.
    Zhang, Kuize
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Long-term behavior of cross-dimensional linear dynamical systems2018Inngår i: Chinese Control Conference, CCC, IEEE Computer Society , 2018, s. 158-163Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Let M and V denote the sets of finite-dimensional matrices and finite-dimensional column vectors, respectively. Based on the semitensor product and the vector addition, M and V both form a monoid, where V is commutative. In addition, based on an equivalence relation ↔ on V, the induced quotient space V/ ↔ forms a vector space. In this paper, we give a basis for the vector space V/ ↔ , showing that V/ ↔ is of countably infinite dimension. In addition, we give an explicit characterization for how the dimension of a vector in V changes caused by the repetitive actions of a matrix in M on the vector, and characterize the generalized inverse behavior of the repetitive actions.

  • 635.
    Zhang, Kuize
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre. Harbin Engn Univ, Coll Automat, Harbin 150001, Heilongjiang, Peoples R China..
    Johansson, Karl Henrik
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Long-term behavior of cross-dimensional linear dynamical systems2018Inngår i: 2018 37th Chinese Control Conference (CCC) / [ed] Chen, X Zhao, QC, Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 158-163Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Let M and V denote the sets of finite-dimensional matrices and finite-dimensional column vectors, respectively. Based on the semitensor product and the vector addition, M and V both form a monoid, where V is commutative. In addition, based on an equivalence relation. on V, the induced quotient space V/<-> forms a vector space. In this paper, we give a basis for the vector space V/<->, showing that V/<-> is of countably infinite dimension. In addition, we give an explicit characterization for how the dimension of a vector in V changes caused by the repetitive actions of a matrix in M on the vector, and characterize the generalized inverse behavior of the repetitive actions.

  • 636.
    Zhu, Shanying
    et al.
    Shanghai Jiao Tong Univ, Dept Automat, Shanghai 200240, Peoples R China.;Minist Educ China, Key Lab Syst Control & Informat Proc, Shanghai 200240, Peoples R China..
    Chen, Cailian
    Shanghai Jiao Tong Univ, Dept Automat, Shanghai 200240, Peoples R China.;Minist Educ China, Key Lab Syst Control & Informat Proc, Shanghai 200240, Peoples R China..
    Xu, Jinming
    Arizona State Univ, Ira A Fulton Sch Engn, Tempe, AZ 85281 USA..
    Guan, Xinping
    Shanghai Jiao Tong Univ, Dept Automat, Shanghai 200240, Peoples R China.;Minist Educ China, Key Lab Syst Control & Informat Proc, Shanghai 200240, Peoples R China..
    Xie, Lihua
    Nanyang Technol Univ, Sch Elect & Elect Engn, Singapore 639798, Singapore..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Mitigating Quantization Effects on Distributed Sensor Fusion: A Least Squares Approach2018Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 66, nr 13, s. 3459-3474Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the problem of sensor fusion over networks with asymmetric links, where the common goal is linear parameter estimation. For the scenario of bandwidth-constrained networks, existing literature shows that nonvanishing errors always occur, which depend on the quantization scheme. To tackle this challenging issue, we introduce the notion of virtual measurements and propose a distributed solution LS-DSFS, which is a combination of a quantized consensus algorithm and the least squares approach. We provide detailed analysis of the LS-DSFS on its performance in terms of unbiasedness and mean square property. Analytical results show that the LS-DSFS is effective in smearing out the quantization errors, and achieving the minimum mean square error (MSE) among the existing centralized and distributed algorithms. Moreover, we characterize its rate of convergence in the mean square sense and that of the mean sequence. More importantly, we find that the LS-DSFS outperforms the centralized approaches within a moderate number of iterations in terms of MSE, and will always consume less energy and achieve more balanced energy expenditure as the number of nodes in the network grows. Simulation results are presented to validate theoretical findings and highlight the improvements over existing algorithms.

  • 637.
    Zurita Ares, Benigno
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Park, Pan Gun
    KTH, Skolan för elektro- och systemteknik (EES).
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Speranzon, Alberto
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    On power control for wireless sensor networks: System model, middleware component and experimental evaluation2015Inngår i: 2007 European Control Conference, ECC 2007, 2015, s. 4293-4300Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we investigate strategies for radio power control for wireless sensor networks that guarantee a desired packet error probability. Efcient power control algorithms are of major concern for these networks, not only because the power consumption can be signicantly decreased but also because the interference can be reduced, allowing for higher throughput. An analytical model of the Received Signal Strength Indicator (RSSI), which is link quality metric, is proposed. The model relates the RSSI to the Signal to Interference plus Noise Ratio (SINR), and thus provides a connection between the powers and the packet error probability. Two power control mechanisms are studied: a Multiplicative-Increase Additive-Decrease (MIAD) power control described by a Markov chain, and a power control based on the average packet error rate. A component-based software implementation using the Contiki operating system is provided for both the power control mechanisms. Experimental results are reported for a test-bed with Telos motes.

  • 638. Årzén, Karl-Erik
    et al.
    Bicchi, Antonio
    Dini, Gianluca
    Hailes, Stephen
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Lygeros, John
    Tzes, Anthony
    A component-based approach to the design of networked control systems2007Inngår i: European Journal of Control, ISSN 0947-3580, E-ISSN 1435-5671, Vol. 13, nr 2-3, s. 261-279Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Component-based techniques revolve around composable, reusable software objects that shield the application level software from the details of the hardware and low-level software implementation and vice versa. Components provide many benefits that have led to their wide adoption it software and middleware developed for embedded systems: They are well-defined entities that can be replaced without affecting the rest of the systems, they can be developed and tested separately and integrated later, and they are reusable. Clearly such features are important for the design of large-scale complex systems more generally, beyond software architectures. We propose the use of a component approach to address embedded control problems. We outline a general coponent-based framework to embedded control aid show how it can be instantiated inspecific problems that arise in the control over/of sensor networks. Building on the middleware component framework developed under the European project RUNES, we develop a number of control-oriented components necessary for the implementation of control applications and design their integration. The paper provides the overview of the approach, discusses a real life application where the approach has been tested and outlines a number of specific control problems that arise in this application.

  • 639. Årzén, Karl-Erik
    et al.
    Bicchi, Antonio
    Hailes, Stephen
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Lygeros, John
    On the design and control of wireless networked embedded systems2006Inngår i: 2006 IEEE Conference on Computer-Aided Control System Design, Vols 1 and 2, IEEE , 2006, s. 143-148Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Wireless networked embedded systems are becoming increasingly important in a wide area of technical fields. In this tutorial paper we present recent results on the design of these systems and their use in control applications, that have been developed within the project Reconfigurable Ubiquitous Networked Embedded Systems (RUNES). RUNES is a European Integrated Project with the aim to control complexity in networked embedded systems by developing robust and scalable middleware systems. New components for control under varying network conditions are discussed for the RUNES architecture. The paper highlights how the complexity of the closed-loop system is increased, due to additional disturbances introduced by the communication system: additional delays, jitter, data rate limitations, packet losses, etc. Experimental work on integration test beds that demonstrates these results is presented, together with motivating links to the RUNES disaster relief tunnel scenario.

  • 640. Årzén, Karl-Erik
    et al.
    Robertsson, Anders
    Henriksson, Dan
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hjalmarsson, Håkan
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Conclusions from the European Roadmap on Control of Computing Systems2006Inngår i: First International Workshop on Feedback Control Implementation and Design in Computing Systems and Networks, 2006Konferansepaper (Fagfellevurdert)
  • 641. Årzén, Karl-Erik
    et al.
    Robertsson, Anders
    Henriksson, Dan
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Conclusions of the ARTIST2 roadmap on control of computing systems2006Inngår i: ACM SIGBED Review, ISSN 1551-3688, Vol. 3, nr 2, s. 11-20Artikkel i tidsskrift (Fagfellevurdert)
  • 642. Åström, K. J.
    et al.
    Johansson, Karl H.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Wang, Qing-Guo
    Design of decoupled PID controllers for MIMO systems2001Inngår i: Proceedings of the 2001 American Control Conference, IEEE , 2001, s. 2015-2020Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The design of PID controllers for systems with interacting loops is discussed. It is important to deal with the interaction at the lower-level loops, since supervisory control based on for instance MPC seldom has sufficient bandwidth. A new scheme based on modified scalar PID design and static decoupling is developed, where the frequency characteristics of the coupling between the lower-level loops is taken into account. This leads to a design method emphasizing the trade-off between the individual loop performances and the so called interaction indices. The controller is easily implemented, due to its simple configuration based on standard components. The method is applied to a couple of examples.

  • 643.
    Čičić, Mladen
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Liang, Kuo-Yun
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. Scania CV AB.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Platoon Merging Distance Prediction using a Neural Network Vehicle Speed Model2017Inngår i: IFAC-PapersOnLineVolume 50, Issue 1, July 2017, Pages 3720-3725, 2017, s. 3720-3725Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Heavy-duty vehicle platooning has been an important research topic in recent years. By driving closely together, the vehicles save fuel by reducing total air drag and utilize the road more efficiently. Often the heavy-duty vehicles will catch-up in order to platoon while driving on the common stretch of road, and in this case, a good prediction of when the platoon merging will take place is required in order to make predictions on overall fuel savings and to automatically control the velocity prior to the merge. The vehicle speed prior to platoon merging is mostly influenced by the road grade and by the local traffic condition. In this paper, we examine the influence of road grade and propose a method for predicting platoon merge distance using vehicle speed prediction based on road grade. The proposed method is evaluated using experimental data from platoon merging test runs done on a highway with varying level of traffic. It is shown that under reasonable conditions, the error in the merge distance prediction is smaller than 8%.

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