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  • 1.
    Anderson, James
    et al.
    Oxford University.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Papachristodoulou, Antonis
    Oxford University.
    Dynamical System Decomposition Using Dissipation Inequalities2011In: Proceedings of the 50th IEEE Conference on Decision and Control and European Control Conference,  Orlando, Florida, 2011Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate stability and inter-action measures for interconnected systems that have beenproduced by decomposing a large-scale linear system into aset of lower order subsystems connected in feedback. We beginby analyzing the requirements for asymptotic stability throughgeneralized dissipation inequalities and storage functions. Usingthis insight we then describe various metrics based on a system’senergy dissipation to determine how strongly the subsystemsinteract with each other. From these metrics a decompositionalgorithm is described.

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    fulltext
  • 2. Andersson, G.
    et al.
    Esfahani, P. M.
    Vrakopoulou, M.
    Margellos, K.
    Lygeros, J.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Cyber-security of SCADA systems2012In: 2012 IEEE PES Innovative Smart Grid Technologies, ISGT 2012, IEEE , 2012, p. 6175543-Conference paper (Refereed)
    Abstract [en]

    After a general introduction of the VIKING EU FP7 project two specific cyber-attack mechanisms, which have been analyzed in the VIKING project, will be discussed in more detail. Firstly an attack and its consequences on the Automatic Generation Control (AGC) in a power system are investigated, and secondly the cyber security of State Estimators in SCADA systems is scrutinized.

  • 3.
    Araújo, José
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Henriksson, Erik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    A down-sampled controller to reduce network usage with guaranteed closed-loop performance2014In: Decision and Control (CDC), 2014 IEEE 53rd Annual Conference on, IEEE conference proceedings, 2014, p. 6849-6856Conference paper (Refereed)
    Abstract [en]

    We propose and evaluate a down-sampled controller which reduces the network usage while providing a guaranteed desired linear quadratic control performance. This method is based on fast and slow sampling intervals, as the closed-system benefits by being brought quickly to steady-state conditions while behaving satisfactorily when being actuated at a slow rate once at those conditions. This mechanism is shown to provide large savings with respect to network usage when compared to traditional periodic time-triggered control and other aperiodic controllers proposed in the literature.

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    preprint
  • 4.
    Farokhi, Farhad
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Teixeira, Andre M. H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Langbort, Cedric
    Gaussian Cheap Talk Game with Quadratic Cost Functions: When Herding Between Strategic Senders is a Virtue2014In: 2014 AMERICAN CONTROL CONFERENCE (ACC), 2014Conference paper (Refereed)
    Abstract [en]

    We consider a Gaussian cheap talk game with quadratic cost functions. The cost function of the receiver is equal to the estimation error variance, however, the cost function of each senders contains an extra term which is captured by its private information. Following the cheap talk literature, we model this problem as a game with asymmetric information. We start by the single sender case in which the receiver also has access to a noisy but honest side information in addition to the message transmitted by a strategic sender. We generalize this setup to multiple sender case. For the multiple sender case, we observe that if the senders are not herding (i. e., copying each other policies), the quality of the receiver's estimation degrades rapidly as the number of senders increases.

  • 5.
    Ghadimi, Euhanna
    et al.
    KTH, School of Electrical Engineering (EES).
    Teixeira, Andre
    KTH, School of Electrical Engineering (EES).
    Shames, Iman
    KTH, School of Electrical Engineering (EES).
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES).
    On the Optimal Step-size Selection for the Alternating Direction Method of Multipliers2012Conference paper (Refereed)
    Abstract [en]

    The alternating direction method of multipliers is a powerful technique for structured large-scale optimization that has recently found applications in a variety of fields including networked optimization, estimation, compressed sensing and multi-agent systems. While applications of this technique have received a lot of attention, there is a lack of theoretical support for how to set the algorithm parameters, and its step-size is typically tuned experimentally. In this paper we consider three different formulations of the algorithm and present explicit expressions for the step-size that minimizes the convergence rate. We also compare our method with one of the existing step-size selection techniques for consensus applications.

  • 6.
    Ghadimi, Euhanna
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rabbat, Michael
    McGill Univ, Dept Elect & Comp Engn, Montreal, PQ, Canada..
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    The ADMM algorithm for distributed averaging: convergence rates and optimal parameter selection2014In: CONFERENCE RECORD OF THE 2014 FORTY-EIGHTH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS, IEEE conference proceedings, 2014, p. 783-787Conference paper (Refereed)
    Abstract [en]

    We derive the optimal step-size and overrelaxationparameter that minimizes the convergence time oftwo ADMM-based algorithms for distributed averaging. Ourstudy shows that the convergence times for given step-size andover-relaxation parameters depend on the spectral propertiesof the normalized Laplacian of the underlying communicationgraph. Motivated by this, we optimize the edge-weights of thecommunication graph to improve the convergence speed evenfurther. The performance of the ADMM algorithms with ourparameter selection are compared with alternatives from theliterature in extensive numerical simulations on random graphs.

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    preprint
  • 7.
    Ghadimi, Euhanna
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Shames, Iman
    University of Melbourne, Australia.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Optimal parameter selection for the alternating direction method of multipliers (ADMM): quadratic problems2015In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 60, no 3, p. 644-658, article id 6892987Article in journal (Refereed)
    Abstract [en]

    The alternating direction method of multipliers (ADMM) has emerged as a powerful technique for large-scale structured optimization. Despite many recent results on the convergence properties of ADMM, a quantitative characterization of the impact of the algorithm parameters on the convergence times of the method is still lacking. In this paper we find the optimal algorithm parameters that minimize the convergence factor of the ADMM iterates in the context of l2-regularized minimization and constrained quadratic programming. Numerical examples show that our parameter selection rules significantly outperform existing alternatives in the literature.

  • 8.
    Herdeiro Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Strategic stealthy attacks: The output-to-output ℓ2-gain2016In: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2016, p. 2582-2587Conference paper (Refereed)
    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.

  • 9.
    Juelsgaard, Morten
    et al.
    Aalborg University, Denmark.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Wisniewski, Rafal
    Aalborg University, Denmark.
    Bendtsen, Jan
    Aalborg University, Denmark.
    Distributed Coordination of Household Electricity Consumption2014In: 2014 IEEE Conference on Control Applications, CCA 2014, IEEE , 2014, p. 33-40Conference paper (Refereed)
    Abstract [en]

    This work presents a distributed framework for coordination of flexible electricity consumption for a number of households in the distribution grid. Coordination is conducted with the purpose of minimizing a trade-off between individual concerns about discomfort and electricity cost, on the one hand, and joint concerns about grid losses and voltage variations on the other. Our contribution is to demonstrate how distributed coordination of both active and reactive consumption may be conducted, when consumers are jointly coupled by grid losses and voltage variations. We further illustrate the benefit of including consumption coordination for grid operation, and how different types of consumption present different benefits.

  • 10.
    Larsson, Martin
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Lindberg, Jonas
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Lycke, Jens
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Hansson, Karl
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Khakulov, Aziz
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Ringh, Emil
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Svensson, Fredrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Tjernberg, Isak
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Alam, Assad
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Araujo, Jose
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Farokhi, Farhad
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ghadimi, Euhanna
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Teixeira, Andre
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Towards an Indoor Testbed for Mobile Networked Control Systems2011Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider the design of an indoor testbed composed of multiple aerial and ground unmanned vehicles for experimentation in Mobile Networked Control Systems. Taking several motivational aspects from both research and education into account, we propose an architecture to cope with the scale and mobility aspects of the overall system. Currently, the testbed is composed of several low-cost ARdrones quadrotors, small-scale heavy duty vehicles, wireless sensor nodes and a vision-based localization system. As an example, the automatic control of an ARdrone is shown.

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    fulltext
  • 11.
    Sandberg, Henrik
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, K. H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On Security Indices for State Estimators in Power Networks2010In: Preprints of the First Workshop on Secure Control Systems, CPSWEEK 2010,  Stockholm, Sweden, 2010Conference paper (Refereed)
    Abstract [en]

    In this paper, we study stealthy false-data attacksagainst state estimators in power networks. The focus ison applications in SCADA (Supervisory Control and DataAcquisition) systems where measurement data is corrupted bya malicious attacker. We introduce two security indices for thestate estimators. The indices quantify the least effort neededto achieve attack goals while avoiding bad-data alarms in thepower network control center (stealthy attacks). The indicesdepend on the physical topology of the power network and theavailable measurements, and can help the system operator toidentify sparse data manipulation patterns. This informationcan be used to strengthen the security by allocating encryptiondevices, for example. The analysis is also complemented witha convex optimization framework that can be used to evaluatemore complex attacks taking model deviations and multipleattack goals into account. The security indices are finallycomputed in an example. It is seen that a large measurementredundancy forces the attacker to use large magnitudes in thedata manipulation pattern, but that the pattern still can be relatively sparse.

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    fulltext
  • 12.
    Shames, Iman
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Teixeira, Andre
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karl Henrik, Johansson
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed Fault Detection for Interconnected Second-Order Systems2011In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 47, no 12, p. 2757-2764Article in journal (Refereed)
    Abstract [en]

    In this paper the existence of unknown input observers for networks of interconnected second-order linear time invariant systems is studied. Two classes of distributed control systems of large practical relevance are considered. It is proved that for these systems one can construct a bank of unknown input observers, and use them to detect and isolate faults in the network. The result presents a distributed implementation. In particular, by exploiting the system structure, this work provides further insight into the design of UIO for networked systems. Moreover, the importance of certain network measurements is shown. Infeasibility results with respect to available measurements and faults are also provided, as well as methods to remove faulty agents from the network. Applications to power networks and robotic formations are presented. It is shown how the developed methodology apply to a power network described by the swing equation with a faulty bus. For a multi-robot system, it is illustrated how a faulty robot can be detected and removed.

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    fulltext
  • 13.
    Shames, Iman
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed Fault Detection and Isolation with Imprecise Network Models2012In: 2012 American Control Conference (ACC), IEEE Computer Society, 2012, p. 5906-5911Conference paper (Refereed)
    Abstract [en]

    In this paper we consider the problem of Distributed Fault Detection and Isolation (D-FDI) in large networked systems with imprecise models. Taking a previously proposed D-FDI scheme for a given initial network model, we analyze its performance under small changes in the network graph, namely the addition or removal of edges. Under some assumptions, it is shown that for this kind of perturbations there exist suitable thresholds for which fault detection and isolation is achieved. As our second contribution, we propose solutions to accomplish D-FDI with considerably lower computational burden, while handling imprecise network models. Numerical experiments demonstrating the effectiveness of the proposed solution are presented, taking the IEEE 118 bus power network as an example.

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    fulltext
  • 14.
    Shames, Iman
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed fault detection for interconnected second-order systems with applications to power networks2010In: Preprints of the First Workshop on Secure Control Systems, CPSWEEK 2010,  Stockholm, Sweden, 2010Conference paper (Refereed)
    Abstract [en]

    Observers for distributed fault detection of interconnectedsecond-order linear time invariant systems is studied.Particularly, networked systems under consensus protocols areconsidered and it is proved that for these systems one canconstruct a bank of so-called unknown input observers, and usetheir output to detect and isolate possible faults in the network.The application of this family of fault detectors to power networksis presented.

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    fulltext
  • 15.
    Shames, Iman
    et al.
    University of Melbourne, Melbourne, Australia.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Fault Detection and Mitigation in Kirchhoff Networks2012In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 19, no 11, p. 749-752Article in journal (Refereed)
    Abstract [en]

    In this letter, we study the problem of fault detection and mitigation in networks where the measurements satisfy Kirchhoff's voltage law. First, we characterise the class of faults appearing as an additive fault vector (injected by a malicious adversary or due to equipment failures) that can be detected by taking into account the topology of the network. Second, we consider the problem of estimating the fault vector via tools from compressive sensing. Moreover, we comment on the applicability of the developed methods to the case where the measurements satisfy Kirchhoff's current law. The proposed methods are validated via numerical examples with application to time synchronization networks.

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    fulltext
  • 16.
    Shames, Iman
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Agents Misbehaving in a Network: a Vice or a Virtue?2012In: IEEE Network, ISSN 0890-8044, E-ISSN 1558-156X, Vol. 26, no 3, p. 35-40Article in journal (Refereed)
    Abstract [en]

    Misbehaviors among the agents in a network might be intentional or unintentional, they might cause a system-wide failure or they might improve the performance or even enable us to achieve an objective. In this article we consider examples of these possible scenarios. First, we argue the necessity of monitoring the agents in a network to detect if they are misbehaving or not and outline a distributed method in which each agent monitors its neighbors for any sign of misbehavior. Later, we focus on solving the problem of distributed leader selection via forcing the agents to temporarily misbehave, and introduce an algorithm that enables the agents in a network to select their leader without any interference from the outside of the network.

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  • 17.
    Shames, Iman
    et al.
    Australian National University.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed Leader Selection without Direct Inter-Agent Communication2010In: 2nd IFAC Workshop on Distributed Estimation and Control in Networked Systems, NecSys'10, 2010, p. 221-226Conference paper (Refereed)
    Abstract [en]

    This paper is an endeavour to address the problem of distributed leader selection in a formation of autonomous agents where the agents do not communicate directly via communication channels. The algorithm that the agents use to select a leader relies on the agents observing each others' behaviours. It is shown that the proposed algorithm is terminated, on average, in finite number of step and results in the selection of a leader for the formation. Moreover, It is established that the algorithm has some common elements with an algorithm widely used in data networks, i.e.~Slotted Aloha. The application of the algorithm to a formation controlled by a nonlinear control law is studied and some numerical examples are presented to show the general performance of the algorithm.

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    multiagent_selection_necsys10
  • 18.
    Teixeira, Andre
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Networked Control Systems under Cyber Attacks with Applications to Power Networks2010In: 2010 AMERICAN CONTROL CONFERENCE   , 2010, p. 3690-3696Conference paper (Refereed)
    Abstract [en]

    Networked control systems under certain cyber attacks are analyzed. The communication network of these control systems make them vulnerable to attacks from malicious outsiders. Our work deals with two types of attacks: attacks on the network nodes and attacks on the communication between the nodes. We propose a distributed scheme to detect and isolate the attacks using observers. Furthermore, we discuss how to reduce the number of observer nodes while maintaining the coverage of the entire network. The results are applied to two classes of networked control systems: a network running the consensus protocol and a power network defined by the linearized swing equation. Sufficient conditions for the existence of the proposed attack detection scheme are provided for the first class of systems. For the second class, we provide a necessary condition for the existence of the proposed detection scheme.

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    secure_acc10
  • 19.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Toward Cyber-Secure and Resilient Networked Control Systems2014Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Resilience is the ability to maintain acceptable levels of operation in the presence of abnormal conditions. It is an essential property in industrial control systems, which are the backbone of several critical infrastructures. The trend towards using pervasive information technology systems, such as the Internet, results in control systems becoming increasingly vulnerable to cyber threats. Traditional cyber security does not consider the interdependencies between the physical components and the cyber systems. On the other hand, control-theoretic approaches typically deal with independent disturbances and faults, thus they are not tailored to handle cyber threats. Theory and tools to analyze and build control system resilience are, therefore, lacking and in need to be developed. This thesis contributes towards a framework for analyzing and building resilient control systems.

    First, a conceptual model for networked control systems with malicious adversaries is introduced. In this model, the adversary aims at disrupting the system behavior while remaining undetected by an anomaly detector The adversary is constrained in terms of the available model knowledge, disclosure resources, and disruption capabilities. These resources may correspond to the anomaly detector’s algorithm, sniffers of private data, and spoofers of control commands, respectively.

    Second, we address security and resilience under the perspective of risk management, where the notion of risk is defined in terms of a threat’s scenario, impact, and likelihood. Quantitative tools to analyze risk are proposed. They take into account both the likelihood and impact of threats. Attack scenarios with high impact are identified using the proposed tools, e.g., zero-dynamics attacks are analyzed in detail. The problem of revealing attacks is also addressed. Their stealthiness is characterized, and how to detect them by modifying the system’s structure is also described.

    As our third contribution, we propose distributed fault detection and isolation schemes to detect physical and cyber threats on interconnected second-order linear systems. A distributed scheme based on unknown input observers is designed to jointly detect and isolate threats that may occur on the network edges or nodes. Additionally, we propose a distributed scheme based on local models and measurements that is resilient to changes outside the local subsystem. The complexity of the proposed methods is decreased by reducing the number of monitoring nodes and by characterizing the minimum amount of model information and measurements needed to achieve fault detection and isolation.

    Finally, we tackle the problem of distributed reconfiguration under sensor and actuator faults. In particular, we consider a control system with redundant sensors and actuators cooperating to recover from the removal of individual nodes. The proposed scheme minimizes a quadratic cost while satisfying a model-matching condition, which maintains the nominal closed-loop behavior after faults. Stability of the closed-loop system under the proposed scheme is analyzed.

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    thesis_AndreTeixeira
  • 20.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Toward Secure and Reliable Networked Control Systems2011Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Security and reliability are essential properties in Networked Control Systems (NCS), which are increasingly relevant in several important applications such as he process industry and electric power networks. The trend towards using non-proprietary and pervasive communication and information technology (IT) systems, such as the Internet and wireless communications, may result in NCS being vulnerable to cyber attacks. Traditional IT security does not consider the interdependencies between the physical components and the cyber realm of IT systems. Moreover, the control theoretic approach is not tailored to handle IT threats, focusing instead on nature-driven events. This thesis addresses the security and reliability of NCS, with a particular focus on power system control and supervision, contributing towards establishing a framework capable of analyzing and building NCS security. In our first contribution, the cyber security of the State Estimator (SE) in power networks is analyzed under malicious sensor data corruption attacks. The set of stealthy attacks bypassing current Bad Data Detector (BDD) schemes is characterized for the nonlinear least squares SE, assuming the attacker has accurate knowledge of a linearized model. This result is then extended to uncertain models using the geometric properties of the SE and BDD. Using the previous results, a security framework based on novel rational attack models is proposed, in which the minimum-effort attack policy is cast as a constrained optimization problem. The optimal attack cost is interpreted as a security metric, which can be used in the design of protective schemes to strengthen security. The features of the proposed framework are illustrated through simulation examples and experiments. As our second contribution, we analyze the behavior of the Optimal Power Flow (OPF) algorithmin the presence of stealthy sensor data corruption and the resulting consequences to the power network operation. In particular, we characterize the set of attacks that may lead the operator to apply the erroneous OPF recommendation and propose an analytical expression for the optimal solution of a simplified OPF problem with corrupted measurements. A novel impact-aware security metric is proposed based on these results, considering both the impact on the system and the attack cost. A small analytical example and numerical simulations are presented to illustrate and motivate our contributions. The third contribution considers the design of distributed schemes for fault detection and isolation in large-scale networks of second-order systems. The proposed approach is based on unknown input observers and exploits the networked structure of the system. Conditions are given on what local measurements should be available for the proposed scheme to be feasible. Infeasibility results with respect to available measurements and faults are also provided. In addition, methods to reduce the complexity of the proposed scheme are discussed, thus ensuring the scalability of the solution. Applications to power networks and robotic formations are presented through numerical examples.

     

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    fulltext
  • 21.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Amin, S.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sastry, S. S.
    Cyber security analysis of state estimators in electric power systems2010In: 49TH IEEE CONFERENCE ON DECISION AND CONTROL (CDC), 2010, p. 5991-5998Conference paper (Refereed)
    Abstract [en]

    In this paper, we analyze the cyber security of state estimators in Supervisory Control and Data Acquisition (SCADA) systems operating in power grids. Safe and reliable operation of these critical infrastructure systems is a major concern in our society. In current state estimation algorithms there are bad data detection (BDD) schemes to detect random outliers in the measurement data. Such schemes are based on high measurement redundancy. Although such methods may detect a set of very basic cyber attacks, they may fail in the presence of a more intelligent attacker. We explore the latter by considering scenarios where deception attacks are performed, sending false information to the control center. Similar attacks have been studied before for linear state estimators, assuming the attacker has perfect model knowledge. Here we instead assume the attacker only possesses a perturbed model. Such a model may correspond to a partial model of the true system, or even an out-dated model. We characterize the attacker by a set of objectives, and propose policies to synthesize stealthy deceptions attacks, both in the case of linear and nonlinear estimators. We show that the more accurate model the attacker has access to, the larger deception attack he can perform undetected. Specifically, we quantify trade-offs between model accuracy and possible attack impact for different BDD schemes. The developed tools can be used to further strengthen and protect the critical state-estimation component in SCADA systems.

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    secure_cdc10
  • 22.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Araújo, José
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed actuator reconfiguration in networked control systems2013In: Estimation and Control of Networked Systems, 2013, no PART 1, p. 61-68Conference paper (Refereed)
    Abstract [en]

    In this paper, we address the problem of distributed reconfiguration of first-order networked control systems under actuator faults. In particular, we consider the scenario where a network of actuators cooperates in order to recover from actuator faults. Such recovery is performed through a reconfiguration which minimizes the performance loss due to actuator faults, while guaranteing that the same state trajectory is obtained. The design of the distributed reconfiguration scheme is proposed and evaluated in numerical examples.

  • 23.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Berthier, Robin
    University of Illinois Urbana-Champaign, USA.
    Bobba, Rakesh
    University of Illinois Urbana-Champaign, USA.
    Valdes, Alfonso
    University of Illinois Urbana-Champaign, USA.
    Security of smart distribution grids: Data integrity attacks on integrated volt/VAR control and countermeasures2014In: American Control Conference (ACC), 2014, IEEE conference proceedings, 2014, p. 4372-4378Conference paper (Refereed)
    Abstract [en]

    We examine the feasibility of an attack on themeasurements that will be used by integrated volt-var control(VVC) in future smart power distribution systems. The analysisis performed under a variety of assumptions of adversarycapability regarding knowledge of details of the VVC algorithmused, system topology, access to actual measurements, andability to corrupt measurements. The adversary also faces anoptimization problem, which is to maximize adverse impactwhile remaining stealthy. This is achieved by first identifyingsets of measurements that can be jointly but stealthily corrupted.Then, the maximal impact of such data corruptionis computed for the case where the operator is unaware ofthe attack and directly applies the configuration from theintegrated VVC. Furthermore, since the attacker is constrainedto remaining stealthy, we consider a game-theoretic frameworkwhere the operator chooses settings to maximize observabilityand constrain the adversary action space.

    Download full text (pdf)
    preprint
  • 24.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl-Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A Cyber Security Study of a SCADA Energy Management System: Stealthy Deception Attacks on the State Estimator2011In: IFAC World Congress, 2011Conference paper (Refereed)
  • 25.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ghadimi, Euhanna
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Shames, Iman
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Optimal scaling of the ADMM algorithm for distributed quadratic programming2013In: 2013 IEEE 52nd Annual Conference on Decision and Control (CDC), IEEE conference proceedings, 2013, p. 6868-6873Conference paper (Refereed)
    Abstract [en]

    This paper addresses the optimal scaling of the ADMM method for distributed quadratic programming. Scaled ADMM iterations are first derived for generic equalityconstrained quadratic problems and then applied to a class of distributed quadratic problems. In this setting, the scaling corresponds to the step-size and the edge-weights of the underlying communication graph. We optimize the convergence factor of the algorithm with respect to the step-size and graph edge-weights. Explicit analytical expressions for the optimal convergence factor and the optimal step-size are derived. Numerical simulations illustrate our results.

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    preprint
  • 26.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kupzog, F.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Cyber-Secure and Resilient Architectures for Industrial Control Systems2015In: Smart Grid Security: Innovative Solutions for a Modernized Grid, Elsevier, 2015, p. 149-183Chapter in book (Other academic)
    Abstract [en]

    In this chapter, we survey cyber security solutions for control and monitoring systems that are used to manage the Smart Grid. We start with a short review of the history and use of Industrial Control Systems (ICSs) and Supervisory Control and Data Acquisition (SCADA) systems, and how cyber security in control systems has recently become a major concern, in the wake of the Stuxnet and other recently discovered malware. We follow up with surveying information technology and control-centric security tools that can be used to improve the resilience of industrial control systems. Feedback control loops are core components in the Smart Grid, as they enable the maximal utilization of the physical infrastructure and its resources. As the number of control loops in the Smart Grid increases, the cyber security challenges faced by ICSs become increasingly important within the Smart Grid's context. To highlight such novel challenges, we give an overview of the envisioned control loops in future Smart Grids, and discuss the potential impact of cyber threats targeting critical Smart Grid functionalities. As a case study, false-data injection attacks on power transmission networks are considered. The level of resilience to such attacks is assessed through a control-centric risk assessment methodology, which is also used for allocating the deployment of more modern and secure equipment. The chapter ends with a discussion of future research challenges in the area.

  • 27.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Paridari, Kaveh
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Voltage control for interconnected microgrids under adversarial actions2015In: IEEE International Conference on Emerging Technologies and Factory Automation, ETFA, IEEE conference proceedings, 2015Conference paper (Refereed)
    Abstract [en]

    In this paper, we study the impact of adversarial actions on voltage control schemes in interconnected microgrids. Each microgrid is abstracted as a power inverter that can be controlled to regulate its voltage magnitude and phase-angle independently. Moreover, each power inverter is modeled as a single integrator, whose input is given by a voltage droop-control policy that is computed based on voltage magnitude and reactive power injection measurements. Under mild assumptions, we then establish important properties of the nominal linearized closed-loop system, such as stability, positivity, and diagonal dominance. These properties play an important role when characterizing the potential impact of different attack scenarios. In particular, we discuss two attack scenarios where the adversary corrupts measurement data and reference signals received by the voltage droop controllers. The potential impact of instances of each scenario is analyzed using control-theoretic tools, which may be used to develop methodologies for identifying high-risk attack scenarios, as is illustrated by numerical examples.

  • 28.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Pérez, Daniel
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Attack Models and Scenarios for Networked Control Systems2012In: HiCoNS'12 - Proceedings of the 1st ACM International Conference on High Confidence Networked Systems, Association for Computing Machinery (ACM), 2012, p. 55-64Conference paper (Refereed)
    Abstract [en]

    Cyber-secure networked control is modeled, analyzed, and experimentally illustrated in this paper. An attack space defined by the adversary's system knowledge, disclosure, and disruption resources is introduced. Adversaries constrained by these resources are modeled for a networked control system architecture. It is shown that attack scenarios corresponding to replay, zero dynamics, and bias injection attacks can be analyzed using this framework. An experimental setup based on a quadruple-tank process controlled over a wireless network is used to illustrate the attack scenarios, their consequences, and potential counter-measures.

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    replay_scenario
    Download (mp4)
    bias_scenario
    Download (mp4)
    zero-dynamics_scenario
  • 29.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Optimal Power Flow: Closing the Loop over Corrupted Data2012In: 2012 American Control Conference (ACC), IEEE Computer Society, 2012, p. 3534-3540Conference paper (Refereed)
    Abstract [en]

    Recently the power system state estimator was shown to be vulnerable to malicious deception attacks on the measurements, resulting in biased estimates. In this work we analyze the behavior of the Optimal Power Flow (OPF) algorithm in the presence of such maliciously biased estimates and the resulting consequences to the system operator. In particular, we characterize the set of attacks that may lead the operator to apply the erroneous OPF recommendation. Such characterization is used to improve a previously proposed security index by also considering the attack impact, which may be used for allocation and prioritization of protective measures. Additionally, we propose an analytical expression for the optimal solution of a simplified OPF problem with corrupted measurements. A small analytical example is discussed to illustrate and motivate our contributions.

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    tdsj_ACC12
  • 30.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Shames, Iman
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed Fault Detection and Isolation Resilient to Network Model Uncertainties2014In: IEEE Transactions on Cybernetics, ISSN 2168-2267, E-ISSN 2168-2275, Vol. 44, no 11, p. 2024-2037Article in journal (Refereed)
    Abstract [en]

    The ability to maintain state awareness in the face of unexpected and unmodeled errors and threats is a defining feature of a resilient control system. Therefore, in this paper, we study the problem of distributed fault detection and isolation (FDI) in large networked systems with uncertain system models. The linear networked system is composed of interconnected subsystems and may be represented as a graph. The subsystems are represented by nodes, while the edges correspond to the interconnections between subsystems. Considering faults that may occur on the interconnections and subsystems, as our first contribution, we propose a distributed scheme to jointly detect and isolate faults occurring in nodes and edges of the system. As our second contribution, we analyze the behavior of the proposed scheme under model uncertainties caused by the addition or removal of edges. Additionally, we propose a novel distributed FDI scheme based on local models and measurements that is resilient to changes outside of the local subsystem and achieves FDI. Our third contribution addresses the complexity reduction of the distributed FDI method, by characterizing the minimum amount of model information and measurements needed to achieve FDI and by reducing the number of monitoring nodes. The proposed methods can be fused to design a scalable and resilient distributed FDI architecture that achieves local FDI despite unknown changes outside the local subsystem. The proposed approach is illustrated by numerical experiments on the IEEE 118-bus power network benchmark.

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    preprint
  • 31.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Shames, Iman
    University of Melbourne, Melbourne, Australia.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Revealing Stealthy Attacks in Control Systems2012In: 2012 50th Annual Allerton Conference On Communication, Control, And Computing (Allerton), IEEE conference proceedings, 2012, p. 1806-1813Conference paper (Refereed)
    Abstract [en]

    In this paper the problem of revealing stealthy data-injection attacks on control systems is addressed. In particular we consider the scenario where the attacker performs zero-dynamics attacks on the system. First, we characterize and analyze the stealthiness properties of these attacks for linear time-invariant systems. Then we tackle the problem of detecting such attacks by modifying the system's structure. Our results provide necessary and sufficient conditions that the modifications should satisfy in order to detect the zero-dynamics attacks. The results and proposed detection methods are illustrated through numerical examples.

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    fulltext
  • 32.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Shames, Iman
    University of Melbourne, Melbourne, Australia.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A Secure Control Framework for Resource-Limited Adversaries2015In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 51, no 1, p. 135-148Article in journal (Refereed)
    Abstract [en]

    Cyber-secure networked control is modeled, analyzed, and experimentally illustrated in this paper. An attack space dened bythe adversary's model knowledge, disclosure, and disruption resources is introduced. Adversaries constrained by these resourcesare modeled for a networked control system architecture. It is shown that attack scenarios corresponding to denial-of-service,replay, zero-dynamics, and bias injection attacks on linear time-invariant systems can be analyzed using this framework.Furthermore, the attack policy for each scenario is described and the attack's impact is characterized using the concept ofsafe sets. An experimental setup based on a quadruple-tank process controlled over a wireless network is used to illustrate theattack scenarios, their consequences, and potential counter-measures.

    Download full text (pdf)
    preprint
  • 33.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sou, Kin C.
    Chalmers University of Technology and University of Gothenburg,.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Quantifying Cyber-Security for Networked Control Systems2013In: Control of Cyber-Physical Systems: Workshop held at Johns Hopkins University, March 2013 / [ed] Danielle C. Tarraf, Switzerland: Springer International Publishing , 2013, p. 123-142Chapter in book (Refereed)
    Abstract [en]

    In this paper we consider a typical architecture for a networked control system under false-data injection attacks. Under a previously proposed adversary modeling framework, various formulations for quantifying cyber-security of control systems are proposed and formulated as constrained optimization problems. These formulations capture trade-offs in terms of attack impact on the control performance, attack detectability, and adversarial resources. The formulations are then discussed and related to system theoretic concepts, followed by numerical examples illustrating the various trade-offs for a quadruple-tank process.

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    tssj_CCPS_2013
  • 34.
    Teixeira, André
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Sou, Kin C.
    Chalmers University of Technology and University of Gothenburg,.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Secure control systems: A quantitative risk management approach2015In: IEEE Control Systems, ISSN 1066-033X, Vol. 35, no 1, p. 24-45Article in journal (Refereed)
    Abstract [en]

    Critical infrastructures must continuously operate safely and reliably, despite a variety of potential system disturbances. Given their strict operating requirements, such systems are automated and controlled in real time by several digital controllers receiving measurements from sensors and transmitting control signals to actuators. Since these physical systems are often spatially distributed, there is a need for information technology (IT) infrastructures enabling the timely data flow between the system components. These networked control systems are ubiquitous in modern societies [1]. Examples include the electric power network, intelligent transport systems, and industrial processes.

1 - 34 of 34
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