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  • 201.
    Flärdh, Oscar
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    A comparison of control structures for error correction in packet-switched networks2005Konferansepaper (Fagfellevurdert)
  • 202.
    Flärdh, Oscar
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    A new feedback control mechanism for error correction in packet-switched networks2005Inngår i: 44th IEEE Conference on Decision and Control & European Control Conference, 2005, s. 488-493Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Error correction mechanisms enable control and other real-time applications to be executed over unreliable packet-switched networks. By adding carefully adjusted redundancy to transmitted data at the sender, it is possible to recover lost data at the receiver and thereby improve effective throughput. We describe simple models for packet loss, which allow us to find the optimal redundancy as a function of packet loss probability. Two feedforward control mechanisms based on the packet loss probability are presented: one that is computed off-line and another one using an on-line algorithm. A drawback with these approaches is their dependency on accurate network state information and precise loss models. To cope with these issues, we propose a new feedback solution that tracks the optimum using gradient estimation. Simulations in ns-2 illustrate the behavior of the error correction schemes, demonstrating that the feedback solution outperforms the feedforward solution in presence of model errors.

    Fulltekst (pdf)
    network_fec_cdc05
  • 203.
    Färnqvist, Daniel
    et al.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Strandemar, Katrin
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Johansson, Karl Henrik
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Hespanha, João Pedro
    Hybrid modeling of communication networks using Modelica2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Modeling and simulation of communication networks using the modeling language Modelica are discussed. Congestion control in packet-switched networks, such as the Internet, is today mainly analyzed through time-consuming simulations of individual packets. We show, by developing a model library based on a recent hybrid systems model, that Modelica provides an efficient platform for the analysis of communication networks. As an example, a comparison between the two congestion control protocols is presented.

    Fulltekst (pdf)
    network_rm02
  • 204.
    Gao, Yulong
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jafarian, Matin
    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.
    Xie, Lihua
    Distributed Freeway Ramp Metering: Optimization on Flow Speed2017Inngår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, IEEE , 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper studies the distributed freeway ramp metering problem, for which the cell transmission model (CTM) is utilized. Considering the jam density and the upper bounds on the queue lengths and the ramp metering, we first provide feasibility conditions with respect to the external demand to ensure the controllability of the freeway. Assuming that the freeway is controllable, we formulate an optimization problem which tradeoffs the maximum average flow speed and the minimum waiting queue for each cell. Although the cells of the CTM are dynamically coupled, we propose a distributed backward algorithm for the optimization problem and prove that the solution to the problem is a Nash equilibrium. Furthermore, if the optimization problem is simplified to only maximization of the average flow speed, we argue that the obtained explicit distributed controller is globally optimal. A numerical example is given to illustrate the effectiveness of the proposed control algorithm.

  • 205.
    Gao, Yulong
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Wu, Shuang
    Hong Kong Univ Sci & Technol, Elect & Comp Engn, Kowloon, Clear Water Bay, Hong Kong, Peoples R China..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Shi, Ling
    Hong Kong Univ Sci & Technol, Elect & Comp Engn, Kowloon, Clear Water Bay, Hong Kong, Peoples R China..
    Xie, Lihua
    Nanyang Technol Univ, Sch Elect & Elect Engn, Singapore 639798, Singapore..
    Stochastic Optimal Control of Dynamic Queue Systems: A Probabilistic Perspective2018Inngår i: 2018 15TH INTERNATIONAL CONFERENCE ON CONTROL, AUTOMATION, ROBOTICS AND VISION (ICARCV), IEEE , 2018, s. 837-842Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Queue overflow of a dynamic queue system gives rise to the information loss (or packet loss) in the communication buffer or the decrease of throughput in the transportation network. This paper investigates a stochastic optimal control problem for dynamic queue systems when imposing probability constraints on queue overflows. We reformulate this problem as a Markov decision process (MDP) with safety constraints. We prove that both finite-horizon and infinite-horizon stochastic optimal control for MDP with such constraints can be transformed as a linear program (LP), respectively. Feasibility conditions are provided for the finite-horizon constrained control problem. Two implementation algorithms are designed under the assumption that only the state (not the state distribution) can be observed at each time instant. Simulation results compare optimal cost and state distribution among different scenarios, and show the probability constraint satisfaction by the proposed algorithms.

  • 206.
    Gao, Yulong
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Yu, Pian
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Xie, Lihua
    Nanyang Technol Univ, Sch Elect & Elect Engn, Singapore 639798, Singapore..
    Robust self-triggered control for time-varying and uncertain constrained systems via reachability analysis2019Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 107, s. 574-581Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper develops a robust self-triggered control algorithm for time-varying and uncertain systems with constraints based on reachability analysis. The resulting piecewise constant control inputs achieve communication reduction and guarantee constraint satisfactions. In the particular case when there is no uncertainty, we propose a control design with minimum number of samplings over finite time horizon. Furthermore, when the plant is linear and the constraints are polyhedral, we prove that the previous algorithms can be reformulated as computationally tractable mixed integer linear programs. The method is compared with the robust self-triggered model predictive control in a numerical example and applied to a robot motion planning problem with temporal constraints.

  • 207. Garin, Federica
    et al.
    Varagnolo, Damiano
    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.
    Distributed estimation of diameter, radius and eccentricities in anonymous networks2012Inngår i: Estimation and Control of Networked Systems, Vol 3. Part 1, IFAC , 2012, s. 13-18Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider how a set of collaborating agents can distributedly infer some of the properties of the communication network that they form. We specifically focus on estimating quantities that can characterize the performance of other distributed algorithms, namely the eccentricities of the nodes, and the radius and diameter of the network. We propose a strategy that can be implemented in any network, even under anonymity constraints, and has the desirable properties of being fully distributed, parallel and scalable. We analytically characterize the statistics of the estimation error, and highlight how the performance of the algorithm depends on a parameter tuning the communication complexity.

    Fulltekst (pdf)
    network_garin_necsys12
  • 208. Giani, A.
    et al.
    Sastry, S.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    The VIKING project: An initiative on resilient control of power networks2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents the work on resilient and secure power transmission and distribution developed within the VIKING (vital infrastructure, networks, information and control system management) project. VIKING receives funding from the European Community's Seventh Framework Program. We will present the consortium, the motivation behind this research, the main objective of the project together with the current status.

    Fulltekst (pdf)
    security_isrcs09
  • 209. Guinajdo, M.
    et al.
    Lehmann, Daniel
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Sanchez, J.
    Dormido, S.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Reducing communication and actuation in distributed control systems2013Inngår i: 2013 IEEE 52nd Annual Conference on Decision and Control (CDC), IEEE conference proceedings, 2013, s. 5288-5293Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper addresses the problem of reducing the number of transmissions and control updates in a distributed control network of interconnected linear systems. Each node in the network decides when to transmit its state through the network and when to update the control law. Both decisions are event-driven and based on local information. It is shown that the stability of the system is preserved and the state of the system converges to a small region around the origin, whose size depends on the parameters of the transmission and control update trigger functions. A strictly positive lower bound for the inter-event times is derived. The results are illustrated through simulations showing the effectiveness of the proposed approach.

  • 210. Guinaldo, M.
    et al.
    Dimarogonas, Dimos
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Lehmann, Daniel
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Distributed event-based control for interconnected linear systems2015Inngår i: Asynchronous Control for Networked Systems, Springer, 2015, s. 149-179Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    For large-scale interconnected systems, the control performance can be improved by means of distributed control solutions in which the subsystems communicate over the network. In this chapter, different distributed event-based control strategies are analyzed. Each subsystem broadcasts its state over the network according to certain triggering rules which depend on local information only.

  • 211. Guinaldo, M.
    et al.
    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.
    Moreno, J. S.
    Dormido, S.
    Distributed event-based control for interconnected linear systems2011Inngår i: 2011 50th IEEE Conference on Decision and Control andEuropean Control Conference (CDC-ECC), 2011, s. 2553-2558Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a distributed event-basedcontrol strategy for a networked dynamical system consistingof N linear time-invariant interconnected subsystems. Eachsubsystem broadcasts its state over the network accordingto some triggering rules which depend on local informationonly. The system converges to an adjustable region aroundthe equilibrium point under the proposed control design, andthe existence of a lower bound for the broadcasting period isguaranteed. The effect of the coupling terms over the region ofconvergence and broadcasting period lower bound is analyzed,and a novel model-based approach is derived to reduce thecommunications. Simulation results show the effectiveness ofthe proposed approaches and illustrate the theoretical results.

  • 212. Guinaldo, M.
    et al.
    Lehmann, Daniel
    KTH, Skolan för elektro- och systemteknik (EES).
    Moreno, J.S.
    Dormido, S.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Distributed event-triggered control with network delays and packet losses2013Inngår i: IEEE 51st Annual Conference on Decision and Control (CDC), 2012, IEEE conference proceedings, 2013, s. 1-6Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a distributed event-based control approach to cope with communication delays and packet losses affecting a networked dynamical system consisting of N linear time-invariant coupled systems. Two communication protocols are proposed to deal with these communication effects. It is shown that both protocols preserve the system stability in the sense that the state of every subsystem converges to a small region around the origin if the delay and the number of packet losses are bounded. Analytical expressions for the delay bound and the maximum number of consecutive packet losses are derived. Simulations illustrate the results.

    Fulltekst (pdf)
    fulltext
  • 213. Guinaldo, M.
    et al.
    Lehmann, Daniel
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Sanchez, J.
    Dormido, S.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Distributed event-triggered control for non-reliable networks2014Inngår i: Journal of the Franklin Institute, ISSN 0016-0032, E-ISSN 1879-2693, Vol. 351, nr 12, s. 5250-5273Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a distributed event-based control approach to cope with communication delays and packet losses affecting a networked dynamical system. Two network protocols are proposed to deal with these communication effects. The stability of the system is analyzed for constant and time-dependent trigger functions, showing that asymptotic stability can be achieved with the latter design, and this also guarantees a lower bound for the inter-event times. Analytical expressions for the delay bound and the maximum number of consecutive packet losses are derived for different scenarios. Finally, the results are illustrated through a simulation example.

  • 214. Guinaldo, Maria
    et al.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Sanchez, Jose
    Dormido, Sebastian
    Distributed event-based control strategies for interconnected linear systems2013Inngår i: IET Control Theory & Applications, ISSN 1751-8644, E-ISSN 1751-8652, Vol. 7, nr 6, s. 877-886Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study presents distributed event-based control strategies for a networked dynamical system consisting of N linear time-invariant interconnected subsystems. Each subsystem broadcasts its state over the network according to certain triggering rules that only depend on local information. The system can converge asymptotically to the equilibrium point under the proposed control design, and the existence of a lower bound for the broadcasting period is guaranteed. A novel model-based approach is derived to reduce the communication between the agents. Simulation results show the effectiveness of the proposed approaches and illustrate the theoretical results.

  • 215.
    Guo, Meng
    et al.
    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.
    Distributed real-time fault detection and isolation for cooperative multi-agent systems2012Inngår i: 2012 American Control Conference (ACC), IEEE Computer Society, 2012, s. 5270-5275Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we propose a distributed real-time fault detection, isolation and mitigation framework for multiagent systems performing cooperative tasks. Various system models and detection schemes with respect to communication and sensing are considered. Two communication protocols for fault detection are introduced first and proved to be effective. Then a scheme based on limited relative state measurements is developed. Furthermore, we propose fault isolation and mitigation steps to guarantee the accomplishment of a global objective. All schemes are distributed in the sense that at each step of the fault detection, isolation and mitigation every agent only uses locally available information. One key feature of the framework is the significant reduction of required computational resource when compared with the fault detection and isolation schemes based on unknown input observers. Later we show that the proposed framework can be applied to the consensus and other cooperative formation problems. Several computer simulations are presented to demonstrate the efficiency of the framework.

  • 216.
    Guo, Meng
    et al.
    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.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Motion and Action Planning under LTL Specifications using Navigation Functions and Action Description Language2013Inngår i: 2013 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), IEEE , 2013, s. 240-245Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose a novel framework to combine model-checking-based motion planning with action planning using action description languages, aiming to tackle task specifications given as Linear Temporal Logic (LTL) formulas. The specifications implicitly require both sequential regions to visit and the desired actions to perform at these regions. The robot's motion is abstracted based on sphere regions of interest in the workspace and the structure of navigation function(NF)-based controllers, while the robot's action map is constructed based on precondition and effect functions associated with the actions. An optimal planner is designed that generates the discrete motion-and-action plan fulfilling the specification, as well as the low-level hybrid controllers that implement this plan. The whole framework is demonstrated by a case study.

  • 217.
    Guo, Meng
    et al.
    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.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Revising motion planning under Linear Temporal Logic specifications in partially known workspaces2013Inngår i: 2013 IEEE International Conference on Robotics and Automation (ICRA), IEEE Computer Society, 2013, s. 5025-5032Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we propose a generic framework for real-time motion planning based on model-checking and revision. The task specification is given as a Linear Temporal Logic formula over a finite abstraction of the robot motion. A preliminary motion plan is first generated based on the initial knowledge of the system model. Then real-time information obtained during the runtime is used to update the system model, verify and further revise the motion plan. The implementation and revision of the motion plan are performed in real-time. This framework can be applied to partially-known workspaces and workspaces with large uncertainties. Computer simulations are presented to demonstrate the efficiency of the framework.

  • 218. Guo, Z.
    et al.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Shi, L.
    A study of packet-reordering integrity attack on remote state estimation2016Inngår i: Proceedings of the 35th Chinese Control Conference 2016, IEEE Computer Society, 2016, Vol. 2016, s. 7250-7255, artikkel-id 7554505Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recent years have witnessed the surge of interest of security issues in cyber-physical systems. In this paper, we consider malicious cyber attacks in a remote state estimation scenario using time division multiple access communication protocol. A gateway collects the local measurement innovation of each sensor every time instant, while only transmits data packets to a remote estimator during specific time slots. It is assumed that a residue-based detection algorithm is used at the remote side to detect data anomalies. We propose a novel packet-reordering attack strategy where the attacker is able to change the order of the transmitted data packets, without being detected, by compromising the gateway. Furthermore, the evolution of the remote estimation error covariance is derived and the degradation of system performance under the proposed attack is analyzed. Finally, we obtain a sufficient condition for the attack policy to be optimal using the terminal estimation error covariance as a performance metric. Simulations are provided to illustrate the theoretical results.

  • 219. Guo, Z.
    et al.
    Shi, D.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Shi, L.
    Consequence Analysis of Innovation-based Integrity Attacks with Side Information on Remote State Estimation2017Inngår i: IFAC-PapersOnLine, ISSN 2405-8963, Vol. 50, nr 1, s. 8399-8404Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, we study the worst-case consequence of innovation-based integrity attacks with side information in a remote state estimation scenario. A new type of linear attack strategy based on both intercepted and sensing data is proposed and a corresponding stealthiness constraint is characterized. The evolution of the remote estimation error covariance is derived in the presence of the proposed malicious attack, based on which the worst-case attack policy is obtained in closed form. Furthermore, the system estimation performance under the proposed attack is compared with that under the existing attack strategy to determine which attack is more critical in deteriorating system functionality. Simulation examples are provided to illustrate the developed results.

  • 220. Guo, Z.
    et al.
    Shi, D.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Shi, L.
    Worst-case stealthy innovation-based linear attack on remote state estimation2018Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 89, s. 117-124Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, a security problem in cyber–physical systems is studied. We consider a remote state estimation scenario where a sensor transmits its measurement to a remote estimator through a wireless communication network. The Kullback–Leibler divergence is adopted as a stealthiness metric to detect system anomalies. We propose an innovation-based linear attack strategy and derive the remote estimation error covariance recursion in the presence of attack, based on which a two-stage optimization problem is formulated to investigate the worst-case attack policy. It is proved that the worst-case attack policy is zero-mean Gaussian distributed and the numerical solution is obtained by semi-definite programming. Moreover, an explicit algorithm is provided to calculate the compromised measurement. The trade-off between attack stealthiness and system performance degradation is evaluated via simulation examples. 

  • 221.
    Guo, Ziyang
    et al.
    Hong Kong Univ Sci & Technol, Dept Elect & Comp Engn, Hong Kong, Peoples R China. hi, Dawei.
    Shi, Dawei
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Shi, Ling
    Worst-Case Innovation-Based Integrity Attacks With Side Information on mote State Estimation2019Inngår i: IEEE Transactions on Big Data, ISSN 2325-5870, E-ISSN 2168-6750, Vol. 6, nr 1, s. 48-59Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we study the worst-case consequence of innovation-based tegrity attacks with side information in a remote state estimation enario where a sensor transmits its measurement to a remote estimator uipped with a false-data detector. If a malicious attacker is not only le to compromise the transmitted data packet but also able to measure e system state itself, the attack strategy can be designed based on e intercepted data, the sensing data, or alternatively the combined formation. Surprisingly, we show that launching attacks using the mbined information are not always optimal. First, we characterize the ealthiness constraints for different types of attack strategies to oid being noticed by the false-data detector. Then, we derive the olution of the remote estimation error covariance in the presence of tacks, based on which the worst-case attack policies are obtained by lving convex optimization problems. Furthermore, the closed-form pressions of the worst-case attacks are obtained for scalar systems d the attack consequences are compared with the existing work to termine which strategy is more critical in deteriorating system rformance. Simulation examples are provided to illustrate the alytical results.

  • 222. Guo, Ziyang
    et al.
    Shi, Dawei
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Shi, Ling
    Worst-case Analysis of Innovation-based Linear Attack on Remote State Estimation with Resource Constraint2016Inngår i: 2016 IEEE 55th Conference on Decision and Control, CDC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 6303-6308, artikkel-id 7799239Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, a security problem in remote estimation scenario is studied. We consider a multi-sensor system where each sensor transmits its local innovation to a remote estimator through a wireless communication network. A centralized residue-based detection criterion is adopted to monitor system anomalies. We propose a linear attack strategy and present the corresponding feasibility constraints to guarantee stealthiness. For a resource-limited attacker, who is able to listen to all the channels while only launches an attack on one sensor at each time instant, we investigate which sensor should be attacked and what strategy should be used such that the remote estimation error covariance is maximized A closed-form expression of the optimal linear attack strategy is obtained. Simulation examples are provided to illustrate the theoretical results.

  • 223. Guo, Ziyang
    et al.
    Shi, Dawei
    Johansson, Karl-Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Shi, Ling
    Optimal Linear Cyber-Attack on Remote State Estimation2017Inngår i: IEEE TRANSACTIONS ON CONTROL OF NETWORK SYSTEMS, ISSN 2325-5870, Vol. 4, nr 1, s. 4-13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent years have witnessed the surge of interest of security issues in cyber-physical systems. In this paper, we consider malicious cyber attacks in a remote state estimation application where a smart sensor node transmits data to a remote estimator equipped with a false data detector. It is assumed that all the sensor data can be observed and modified by the malicious attacker and a residue-based detection algorithm is used at the remote side to detect data anomalies. We propose a linear deception attack strategy and present the corresponding feasibility constraint which guarantees that the attacker is able to successfully inject false data without being detected. The evolution of the estimation error covariance at the remote estimator is derived and the degradation of system performance under the proposed linear attack policy is analyzed. Furthermore, we obtain a closed-form expression of the optimal attack strategy among all linear attacks. Comparison of attack strategies through simulated examples are provided to illustrate the theoretical results.

  • 224.
    He, Xingkang
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Liu, Q.
    The LSC, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, University of Chinese Academy of Sciences, China.
    Wu, J.
    The College of Control Science and Engineering, Zhejiang University, China.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Distributed parameter estimation under event-triggered communications2019Inngår i: Proceedings of the 2019 Chinese Control Conference (CCC), 2019, s. 5888-5893Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we study a distributed parameter estimation problem with an asynchronous communication protocol over multi-agent systems. Different from traditional time-driven communication schemes, in this work, data can be transmitted between agents intermittently rather than in a steady stream. First, we propose a recursive distributed estimator based on an event-triggered communication scheme, through which each agent can decide whether the current estimate is sent out to its neighbors or not. With this scheme, considerable communications between agents can be effectively reduced. Then, under mild conditions including a collective observability, we provide a design principle of triggering thresholds to guarantee the asymptotic unbiasedness and strong consistency. Furthermore, under certain conditions, we reveal that, with probability one, for every agent the time interval between two successive triggering instants goes to infinity as time goes to infinity. Finally, we provide a numerical simulation to validate the theoretical results of this paper.

  • 225. Heemels, W.P.M.H
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Tabuada, P.
    An introduction to event-triggered and self-triggered control2012Inngår i: IEEE 51st Annual Conference on Decision and Control (CDC), 2012, IEEE conference proceedings, 2012, s. 3270-3285Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recent developments in computer and communication technologies have led to a new type of large-scale resource-constrained wireless embedded control systems. It is desirable in these systems to limit the sensor and control computation and/or communication to instances when the system needs attention. However, classical sampled-data control is based on performing sensing and actuation periodically rather than when the system needs attention. This paper provides an introduction to event- and self-triggered control systems where sensing and actuation is performed when needed. Eventtriggered control is reactive and generates sensor sampling and control actuation when, for instance, the plant state deviates more than a certain threshold from a desired value. Selftriggered control, on the other hand, is proactive and computes the next sampling or actuation instance ahead of time. The basics of these control strategies are introduced together with a discussion on the differences between state feedback and output feedback for event-triggered control. It is also shown how event- and self-triggered control can be implemented using existing wireless communication technology. Some applications to wireless control in process industry are discussed as well.

    Fulltekst (pdf)
    fulltext
  • 226. Hendrickx, Julien M.
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jungers, Raphael M.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sou, Kin Cheong
    Efficient Computations of a Security Index for False Data Attacks in Power Networks2014Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 59, nr 12, s. 3194-3208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The resilience of Supervisory Control and Data Acquisition (SCADA) systems for electric power networks for certain cyber-attacks is considered. We analyze the vulnerability of the measurement system to false data attack on communicated measurements. The vulnerability analysis problem is shown to be NP-hard, meaning that unless P = NP there is no polynomial time algorithm to analyze the vulnerability of the system. Nevertheless, we identify situations, such as the full measurement case, where the analysis problem can be solved efficiently. In such cases, we show indeed that the problem can be cast as a generalization of the minimum cut problem involving nodes with possibly nonzero costs. We further show that it can be reformulated as a standard minimum cut problem (without node costs) on a modified graph of proportional size. An important consequence of this result is that our approach provides the first exact efficient algorithm for the vulnerability analysis problem under the full measurement assumption. Furthermore, our approach also provides an efficient heuristic algorithm for the general NP-hard problem. Our results are illustrated by numerical studies on benchmark systems including the IEEE 118-bus system.

  • 227. Hendrickx, Julien M.
    et al.
    Shi, Guodong
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Finite-Time Consensus Using Stochastic Matrices With Positive Diagonals2015Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 60, nr 4, s. 1070-1073, artikkel-id 6887337Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We discuss the possibility of reaching consensus in finite time using only linear iterations, with the additional restrictions that the update matrices must be stochastic with positive diagonals and consistent with a given graph structure. We show that finite-time average consensus can always be achieved for connected undirected graphs. For directed graphs, we show some necessary conditions for finite-time consensus, including strong connectivity and the presence of a simple cycle of even length.

  • 228.
    Henriksson, Erik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Quevedo, Daniel
    University of Newcastle, Australia.
    Sandberg, Henrik
    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.
    Self-Triggered Model Predictive Control for Network Scheduling and Control2012Inngår i: Advanced Control of Chemical Processes, Vol. 8. Part 1 2012, 2012, s. 432-438Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Herein we present an algorithm for controlling LTI processes using an adaptive sampling interval where the controller at every sampling instant not only computes the new control command but also decides the time interval to the next sample. The approach relies on MPC where the cost function depends on the control performance as well as the cost for sampling. The paper presents a method for synthesizing such a predictive controller and gives explicit conditions for when it is stabilizing. Further it is shown that the optimization problem may be solved off-line and that the controller may be implemented as a lookup table of state feedback gains. The paper is concluded with a numerical example.

  • 229. Henriksson, Erik
    et al.
    Quevedo, D.E
    Peters, E.G.W.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Multiple loop self-triggered model predictive control for network scheduling and control2015Inngår i: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 23, nr 6, s. 2167-2181Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present an algorithm for controlling and scheduling multiple linear time-invariant processes on a shared bandwidth-limited communication network using adaptive sampling intervals. The controller is centralized and not only computes at every sampling instant the new control command for a process but also decides the time interval to wait until taking the next sample.The approach relies on model predictive control ideas, where the cost function penalizes the state and control effort as well as the time interval until the next sample is taken. The latter is introduced to generate an adaptive sampling scheme for the overall system such that the sampling time increases as the norm of the system state goes to zero. This paper presents a method for synthesizing such a predictive controller and gives explicit sufficient conditions for when it is stabilizing. Further explicit conditions are given that guarantee conflict free transmissions on the network. It is shown that the optimization problem may be solved offline and that the controller can be implemented as a lookup table of state feedback gains. The simulation studies which compare the proposed algorithm to periodic sampling illustrate potential performance gains.

  • 230.
    Henriksson, Erik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    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.
    Predictive Compensation for Communication Outages in Networked Control Systems2008Inngår i: Proceedings of the 47th IEEE Conference on Decision and Control, Cancun, Mexico, 2008, s. 2063-2068Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A predictive outage compensator co-located with the actuator node in a networked control system can be used to counteract unpredictable losses of data in the feedback control loop. When a new control command is not received at the actuator node at an appropriate time instance, the predictive outage compensator suggests a replacement command based on the history of past control commands. It is shown that a simple tuning phase together with the monitoring of the control history can lead to a compensator that can improve the closed-loop control performance under communication outages considerably compared to traditional schemes. Worst case performance bounds are given that relate the quality of the tuning phase and the complexity of the compensator with the length of the communication outage period. Zero-order-hold (holding the past control command if the current is lost) and applying an a priori decided constant signal (using a redefined value on the control command if the current is lost) are special cases of the more general compensation scheme presented. The predictive outage compensator is illustrated through computer simulation with communication outages.

    Fulltekst (pdf)
    networked_control_cdc08poc
  • 231.
    Henriksson, Erik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    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.
    Reduced-Order Predictive Outage Compensators for Networked Systems2009Inngår i: Proceedings of the combined 48th IEEE Conference on Decision and Control and 28th Chinese Control Conference, Shanghai, P.R. China, 2009, s. 3775-3780Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Control systems utilizing wireless sensor and actuator networks can be severely affected by the properties of the wireless links. Radio fading and interference may cause communication outage of several samples in situations when the radio environment is noisy and low transmission power is desirable. We propose a method to compensate for outages by introducing a predictive outage compensator (POC), which is a filter to be implemented at the receiver sides of networked control systems and that generates artificial samples during the outage. The main contribution of the paper is to show that a POC can be derived based on a Kalman filter formulation and that it is possible to achieve good performance with a low-order implementation based on Hankel norm approximation. Tradeoffs between achievable closed-loop performance, outage length, and POC order are discussed. The results are illustrated on a simulated example of a multiple-tank process.

    Fulltekst (pdf)
    networked_control_cdc09henriksson
  • 232.
    Herdeiro Teixeira, André
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Strategic stealthy attacks: The output-to-output ℓ2-gain2016Inngår i: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2016, s. 2582-2587Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we characterize and analyze the set of strategic stealthy false-data injection attacks on discrete-time linear systems. In particular, the threat scenarios tackled in the paper consider adversaries that aim at deteriorating the system's performance by maximizing the corresponding quadratic cost function, while remaining stealthy with respect to anomaly detectors. As opposed to other work in the literature, the effect of the adversary's actions on the anomaly detector's output is not constrained to be zero at all times. Moreover, scenarios where the adversary has uncertain model knowledge are also addressed. The set of strategic attack policies is formulated as a non-convex constrained optimization problem, leading to a sensitivity metric denoted as the output-to-output ℓ2-gain. Using the framework of dissipative systems, the output-to-output gain is computed through an equivalent convex optimization problem. Additionally, we derive necessary and sufficient conditions for the output-to-output gain to be unbounded, with and without model uncertainties, which are tightly related to the invariant zeros of the system.

  • 233.
    Hernandez, Aitor
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Faria, Joao
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Araujo, Jose
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Park, Pangun
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    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.
    Inverted Pendulum Control over an IEEE 802.15.4 Wireless Sensor and Actuator Network2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recent research efforts are considering the problem of performing control of dynamical systems over wireless sensor and actuator networks. However, existing results lack an experimental evaluation in real platforms. In this demonstration an inverted pendulum system is controlled over an IEEE 802.15.4 wireless sensor and actuator network. This platform can evaluate several sensor networks and control algorithms and is currently used as an educational tool at KTH Royal Institute of Technology, Sweden.

    Fulltekst (pdf)
    hernandezewsn
  • 234. Hu, Jianghai
    et al.
    Prandini, Maria
    Johansson, Karl Henrik
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Sastry, Shankar
    Hybrid geodesics as optimal solutions to the collision-free motion planning problem2001Inngår i: Hybrid Systems: Computation and Control / [ed] M.D. Di Benedetto, A. Sangiovanni-Vincentelli, Springer Berlin/Heidelberg, 2001, s. 305-318Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    In this paper we address the problem of designing energy minimizing collision-free maneuvers for multiple agents moving on a plane. We show that the problem is equivalent to that of nding the shortest geodesic in a certain manifold with nonsmooth boundary. This allows us to prove that the optimal maneuvers are C1by introducing the concept of u-convex manifolds. Moreover, due to the nature of the optimal maneuvers, the problem can be formulated as an optimal control problem for a certain hybrid system whose discrete states consist of dierent \contact graphs". We determine the analytic expression for the optimal maneuvers in the two agents case. For the three agents case, we derive the dynamics of the optimal maneuvers within each discrete state. This together with the fact that an optimal maneuver is a C1con-catenation of segments associated with dierent discrete states gives a characterization of the optimal solutions in the three agents case.

    Fulltekst (pdf)
    hs01_jianhai
  • 235. Ianelli, L.
    et al.
    Johansson, Karl Henrik
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Jönsson, Ulf
    KTH, Tidigare Institutioner, Matematik.
    Vasca, F.
    Analysis of dither in relay feedback systems2002Inngår i: PROCEEDINGS OF THE 41ST IEEE CONFERENCE ON DECISION AND CONTROL, VOLS 1-4, IEEE , 2002, s. 4425-4430Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Dither signals provide an effective way of compensating for nonlinearities in control systems. The seminal, works by Zames and Shneydor and more recently by Mossaheb present rigorous tools for systematic design of dithered systems. Their results rely however on a Lipschitz assumption on the nonlinearity and thus do not cover important applications with discontinuities. This paper presents initial results on how to analyze and design dither in nonsmooth systems. In particular, it is shown that a dithered relay feedback system can be approximated by a smoothed system obtained through an averaging approach. Guidelines are given for tuning the amplitude and the period time of the dither signal, in order to stabilize the nonsmooth system.

    Fulltekst (pdf)
    dither_cdc02
  • 236. Ianelli, Luigi
    et al.
    Johansson, Karl Henrik
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Jönsson, Ulf
    KTH, Tidigare Institutioner, Matematik.
    Vasca, F.
    Practical stability and limit cycles of dithered relay feedback systems2003Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A new constructive way for choosing dither amplitude and frequency in order to effectively stabilize relay feedback systems by triangular dither is proposed. It is argued that the proposed averaging approach is not easily extended to square dither signals. Trajectories composed by smooth and switching parts are also analyzed and their relationship with limit cycles exhibited by the smoothed system is investigated.

    Fulltekst (pdf)
    dither_ecc03
  • 237. Ianelli, Luigi
    et al.
    Johansson, Karl Henrik
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Jönsson, Ulf
    KTH, Tidigare Institutioner, Matematik.
    Vasca, Francesco
    Dither shape in the averaging of switched systems2004Inngår i: PROCEEDINGS OF THE 2004 AMERICAN CONTROL CONFERENCE, VOLS 1-6, IEEE , 2004, s. 5812-5817Konferansepaper (Fagfellevurdert)
    Abstract [en]

    It was shown by Zames and Shneydor that a high-frequency dither of a quite arbitrary shape can be used to smooth the effective nonlinear sector of Lipschitz continuous feedback systems. Here it is shown that also systems with discontinuous nonlinearities can be smoothed using dither signals, as long as the amplitude distribution function of the dither is Lipschitz continuous.

    Fulltekst (pdf)
    dither_acc04
  • 238. Ianelli, Luigi
    et al.
    Johansson, Karl Henrik
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Jönsson, Ulf
    KTH, Tidigare Institutioner, Matematik.
    Vasca, Francesco
    Effects of dither shapes in nonsmooth feedback systems: experimental results and theoretical insight2003Inngår i: Proceedings of the 42nd IEEE Conference on Decision and Control, Vols. 1-6, IEEE , 2003, s. 4285-4290Konferansepaper (Fagfellevurdert)
    Abstract [en]

     Dither signals are commonly used to compensate for nonlinearities in feedback systems in electronics and mechanics. Recently, theoretical results were proposed for the analysis or a particularly interesting class of nonsmooth systems, namely relay feedback systems with triangular dither. In this paper the class of dither signals is enlarged by considering square and trapezoidal dither: it is shown how the dither shape affects the behavior of nonsmooth feedback systems, differently from the case of dither in Lipschitz continuous systems. Experimental results support this fact and a theoretical insight is given in order to explain the phenomena.

    Fulltekst (pdf)
    dither_cdc03
  • 239. Ianelli, Luigi
    et al.
    Johansson, Karl Henrik
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Jönsson, Ulf
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Vasca, Francesco
    On the averaging of a class of hybrid systems2004Inngår i: 43rd IEEE Conference on Decision and Control, 2004. CDC, IEEE , 2004, s. 1400-1405Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Modeling abstraction and time-scale separation in the design of complex systems often leads to hybrid dynamics. Discontinuities in the continuous evolution of a hybrid system may however create difficulties in the formal analysis, as well as in numerical simulation and verification. Here we study a class of hybrid systems that are excited by high-frequency external signals. These systems arise in the modeling of switched power converters, mechanical systems with friction and quantized systems. For a quite general class of excitation signals, an averaging result is shown stating that the hybrid system can be approximated by a Lipschitz-continuous system. The approximation is in the order of the maximal repetition interval of the excitation signal.

    Fulltekst (pdf)
    dither_cdc04
  • 240. Iannelli, L.
    et al.
    Johansson, Karl H.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Jonsson, U. T.
    Vasca, F.
    Dither for smoothing relay feedback systems2003Inngår i: IEEE Transactions on Circuits And Systems Part I: Fundamental Theory and Applications, ISSN 1057-7122, E-ISSN 1558-1268, Vol. 50, nr 8, s. 1025-1035Artikkel i tidsskrift (Fagfellevurdert)
    Fulltekst (pdf)
    dither_tcas03
  • 241. Iannelli, L.
    et al.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jönsson, U. T.
    Vasca, F.
    Averaging of nonsmooth systems using dither2006Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 42, nr 4, s. 669-676Artikkel i tidsskrift (Fagfellevurdert)
    Fulltekst (pdf)
    dither_automatica06
  • 242. Iannelli, Luigi
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jönsson, Ulf T.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Vasca, Francesco
    Subtleties in the averaging of a class of hybrid systems with applications to power converters2008Inngår i: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 16, nr 8, s. 961-975Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-frequency dither signals are commonly used to implement modulation schemes in power electronics converters. These systems represent an interesting class of hybrid systems with external excitation. They have a rich dynamical behavior, which cannot be easily understood intuitively. Despite the common use of averaging techniques in power electronics, it was only recently proved that a dithered hybrid system can be approximated by an averaged system under certain conditions on the dither signal. Averaging and averaged models for various types of power converters are analyzed in the paper. It is shown that the averaged nonlinearity depends on the dither shape and that dither signals with Lipschitz-continuous averaged nonlinearities can be used to adapt the equivalent gain of power converters. Practical stability of the original dithered system can be inferred by analyzing a simpler averaged system. The main contribution of the paper is to show that the averaged and the dithered systems may have drastically different behavior if the assumptions of the recently developed averaging theory for dithered hybrid systems are violated. Several practical experiments and simulation examples of power electronics converters are discussed. They indicate that the conditions on the dither signal imposed by the averaging theory are rather tight.

    Fulltekst (pdf)
    dither_cep08
  • 243. Iannelli, Luigi
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jönsson, Ulf
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Vasca, Francesco
    Subtleties in the averaging of hybrid systems with application to power electronics2006Inngår i: 2nd IFAC Conference on Analysis and Design of Hybrid Systems, 2006 / [ed] C.G. Cassandras, A. Giua, C. Seatzu, J. Zaytoon, IFAC , 2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Dither signals are commonly used in electronics for implementing different type of modulations in power converters, which represent a very interesting class of hybrid systems. It was recently shown that a nonsmooth dithered system can be approximated by an averaged system provided that the dither frequency is sufficiently high and that the amplitude distribution function of the dither is absolutely continuous and has bounded derivative. This result is exploited in this paper for power converters. Averaged models corresponding to various shapes of dither signal are analyzed, showing that dither with Lipschitz continuous amplitude distribution function can be used to adapt the equivalent gain of the power converter.

    Fulltekst (pdf)
    dither_adh06
  • 244. Ibrahim, A.
    et al.
    Čičić, Mladen
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Goswami, D.
    Basten, T.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Control of Platooned Vehicles in Presence of Traffic Shock Waves2019Inngår i: Proceedings 2019 IEEE Intelligent Transportation Systems Conference, ITSC 2019, Institute of Electrical and Electronics Engineers Inc. , 2019, s. 1727-1734Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Vehicle platooning has been attracting attention recently because of its ability to improve road capacity, safety and fuel efficiency. Vehicles communicate using Vehicle-to- Vehicle (V2V) wireless communication, making their status (acceleration, position, etc.) available to other vehicles. Shock waves, i.e. zones of reduced traffic speed that propagate upstream, are a well known emergent traffic phenomenon. Since vehicles entering such a zone need to decelerate sharply, shock waves cause a deterioration of fuel economy, driving comfort, and safety. While typically caused by bad driving behavior, recent studies have shown that it is possible to diminish or dissipate shock waves by applying certain good driving behavioral patterns. In this work, we use the information about the traffic situation to adapt the reference speed profile of the platoon we control, in order to mitigate the effect of a shock wave coming from downstream. The platoon leader receives the velocity of the vehicles downstream of the platoon and distance gap between them using V2V communication and it computes the shock wave speed. We show that by doing this we reduce the fuel consumption of the vehicles in the platoon, and improve the traffic situation by helping dissipate the shock wave. We validate our results using microscopic models with the help of a toolchain composed of Matlab, and the SUMO traffic simulator.

  • 245.
    Ilic, N.
    et al.
    Faculty of Electrical Engineering, University of Belgrade.
    Stankovic, S.
    Faculty of Electrical Engineering, University of Belgrade.
    Stankovic, Milos
    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.
    Consensus based distributed change detection using generalized likelihood ratio methodology2011Inngår i: 19th Mediterranean Conference on Control and Automation, MED 2011, 2011, s. 1170-1175Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper a novel distributed recursive algorithm based on the Generalized Likelihood Ratio methodology is proposed for real time change detection using sensor networks. The algorithm is based on a combination of recursively generated local statistics and a global consensus strategy, and does not require any fusion center, so that the state of any node can be tested w.r.t. a given common threshold. Two different problems are discussed: detection of an unknown change in the mean and in the variance of an observed random process. Performance of the algorithm for change detection in the mean is analyzed in the sense of a measure of the error with respect to the corresponding centralized algorithm. The analysis encompasses constant and randomly time varying matrices describing communications in the network. Simulation results illustrate characteristic properties of the algorithms.

  • 246. Ilic, Nemanja
    et al.
    Stankovic, Srdjan S.
    Stankovic, Milos S.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Consensus based distributed change detection using Generalized Likelihood Ratio methodology2012Inngår i: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 92, nr 7, s. 1715-1728Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper a novel distributed algorithm derived from the Generalized Likelihood Ratio is proposed for real time change detection using sensor networks. The algorithm is based on a combination of recursively generated local statistics and a global consensus strategy, and does not require any fusion center. The problem of detection of an unknown change in the mean of an observed random process is discussed and the performance of the algorithm is analyzed in the sense of a measure of the error with respect to the corresponding centralized algorithm. The analysis encompasses asymmetric constant and randomly time varying matrices describing communications in the network, as well as constant and time varying forgetting factors in the underlying recursions. An analogous algorithm for detection of an unknown change in the variance is also proposed. Simulation results illustrate characteristic properties of the algorithms including detection performance in terms of detection delay and false alarm rate. They also show that the theoretical analysis connected to the problem of detecting change in the mean can be extended to the problem of detecting change in the variance.

  • 247. Ishizaki, T.
    et al.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Kashima, K.
    Imura, J. -I
    Aihara, K.
    Structured model reduction of interconnected linear systems based on singular perturbation2013Inngår i: Proceedings of the American Control Conference 2013, American Automatic Control Council , 2013, s. 5524-5529Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper proposes a singular perturbation approximation that preserves system passivity and an interconnection topology among subsystems. In the first half of this paper, we develop a singular perturbation approximation valid for stable linear systems. Using the relation between the singular perturbation and the reciprocal transformation, we derive a tractable expression of the error system in the Laplace domain, which provides a novel insight to regulate the approximating quality of reduced models. Then in the second half, we develop a structured singular perturbation approximation that focuses on a class of interconnected systems. This structured approximation provides a reduced model that not only possesses fine approximating quality, but also preserves the original interconnection topology and system passivity.

  • 248.
    Ishizaki, Takayuki
    et al.
    Tokyo Inst Technol, Meguro Ku, 2-12-1 Ookayama, Tokyo 1528552, Japan..
    Sadamoto, Tomonori
    Tokyo Inst Technol, Meguro Ku, 2-12-1 Ookayama, Tokyo 1528552, Japan..
    Imura, Jun-ichi
    Tokyo Inst Technol, Meguro Ku, 2-12-1 Ookayama, Tokyo 1528552, Japan..
    Sandberg, Henrik
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Retrofit control: Localization of controller design and implementation2018Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 95, s. 336-346Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we propose a retrofit control method for stable network systems. The proposed approach is a control method that, rather than an entire system model, requires a model of the subsystem of interest for controller design. To design the retrofit controller, we use a novel approach based on hierarchical state-space expansion that generates a higher-dimensional cascade realization of a given network system. The upstream dynamics of the cascade realization corresponds to an isolated model of the subsystem of interest, which is stabilized by a local controller. The downstream dynamics can be seen as a dynamical model representing the propagation of interference signals among subsystems, the stability of which is equivalent to that of the original system. This cascade structure enables a systematic analysis of both the stability and control performance of the resultant closed-loop system. The resultant retrofit controller is formed as a cascade interconnection of the local controller and an output rectifier that rectifies an output signal of the subsystem of interest so as to conform to an output signal of the isolated subsystem model while acquiring complementary signals neglected in the local controller design, such as interconnection signals from neighboring subsystems. Finally, the efficiency of the retrofit control method is demonstrated through numerical examples of power systems control and vehicle platoon control. 

  • 249. Ishizakiy, T.
    et al.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Kashima, K.
    Imura, J. -I
    Aihara, K.
    Singular perturbation approximation of semistable linear systems2013Inngår i: 2013 European Control Conference, ECC 2013, 2013, s. 4508-4513Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper proposes a singular perturbation approximation for semistable linear systems. In particular, we derive a novel expression of error systems in the Laplace domain. As a result, we obtain an h2-error bound in terms of the sum of eigenvalues of an index matrix, which coincides with a controllability gramian of the state-derivative. Furthermore, we show that the singular perturbation model appropriately preserves the semistability of the original system and also guarantees the stability of the error system. The efficiency of the proposed method is shown through a numerical example of a Markov chain model approximation.

  • 250. Ivarsson, Maria
    et al.
    Sahlholm, Per
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Blackenfelt, Michael
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Nielsen, Lars
    Jansson, Henrik
    Vehicle control using preview information2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The background and the aim of the project,“Vechicle control by using preview information - ’Look Ahead’ ” , are discussed. The project is raisedto explore the possibilities of reduction of fuel consumption and improvements in comfort and safety for heavy vehicles. In particular research will focus on improvements that can be made, in actual and future control systems, with knowledge of the road ahead. This paper describes the project and reports on initial findings as well as related research.

    Fulltekst (pdf)
    vehicle_rm06
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