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Publications (10 of 617) Show all publications
Pirani, M., Nekouei, E., Sandberg, H. & Johansson, K. H. (2019). A game-theoretic framework for security-aware sensor placement problem in networked control systems. In: Proceedings of the American Control Conference: . Paper presented at 2019 American Control Conference, ACC 2019; Philadelphia; United States; 10 July 2019 through 12 July 2019 (pp. 114-119). Institute of Electrical and Electronics Engineers (IEEE), Article ID 8814443.
Open this publication in new window or tab >>A game-theoretic framework for security-aware sensor placement problem in networked control systems
2019 (English)In: Proceedings of the American Control Conference, Institute of Electrical and Electronics Engineers (IEEE), 2019, p. 114-119, article id 8814443Conference paper, Published paper (Refereed)
Abstract [en]

This paper studies the sensor placement problem in a networked control system for improving its security against cyber-physical attacks. The problem is formulated as a zero-sum game between an attacker and a detector. The attacker's decision is to select f nodes of the network to attack whereas the detector's decision is to place f sensors to detect the presence of the attack signals. In our formulation, the attacker minimizes its visibility, defined as the system L2 gain from the attack signals to the deployed sensors' outputs, and the detector maximizes the visibility of the attack signals. The equilibrium strategy of the game determines the optimal locations of the sensors. The existence of Nash equilibrium for the attacker-detector game is studied when the underlying connectivity graph is a directed or an undirected tree. When the game does not admit a Nash equilibrium, it is shown that the Stackelberg equilibrium of the game, with the detector as the game leader, can be computed efficiently. Our results show that, under the optimal sensor placement strategy, an undirected topology provides a higher security level for a networked control system compared with its corresponding directed topology.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Series
Proceedings of the American Control Conference, ISSN 07431619
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-262596 (URN)2-s2.0-85072277874 (Scopus ID)9781538679265 (ISBN)
Conference
2019 American Control Conference, ACC 2019; Philadelphia; United States; 10 July 2019 through 12 July 2019
Note

QC 20191016

Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2019-10-16Bibliographically approved
Bagloee, S. A., Johansson, K. H. & Asadi, M. (2019). A hybrid machine-learning and optimization method for contraflow design in post-disaster cases and traffic management scenarios. Expert systems with applications, 124, 67-81
Open this publication in new window or tab >>A hybrid machine-learning and optimization method for contraflow design in post-disaster cases and traffic management scenarios
2019 (English)In: Expert systems with applications, ISSN 0957-4174, E-ISSN 1873-6793, Vol. 124, p. 67-81Article in journal (Refereed) Published
Abstract [en]

The growing number of man-made and natural disasters in recent years has made the disaster management a focal point of interest and research. To assist and streamline emergency evacuation, changing the directions of the roads (called contraflow, a traffic control measure) is proven to be an effective, quick and affordable scheme in the action list of the disaster management. The contraflow is computationally a challenging problem (known as NP-hard), hence developing an efficient method applicable to real-world and large-sized cases is a significant challenge in the literature. To cope with its complexities and to tailor to practical applications, a hybrid heuristic method based on a machine-learning model and bilevel optimization is developed. The idea is to try and test several contraflow scenarios providing a training dataset for a supervised learning (regression) model which is then used in an optimization framework to find a better scenario in an iterative process. This method is coded as a single computer program synchronized with GAMS (for optimization), MATLAB (for machine learning), EMME3 (for traffic simulation), MS-Access (for data storage) and MS-Excel (as an interface), and it is tested using a real dataset from Winnipeg, and Sioux-Falls as benchmarks. The algorithm managed to find globally optimal solutions for the Sioux-Falls example and improved accessibility to the dense and congested central areas of Winnipeg just by changing the direction of some roads.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Contraflow, Disaster management, Emergency evacuation, Machine-learning, Post-disaster
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-246405 (URN)10.1016/j.eswa.2019.01.042 (DOI)000461529600006 ()2-s2.0-85060331157 (Scopus ID)
Note

QC 20190319

Available from: 2019-03-19 Created: 2019-03-19 Last updated: 2019-04-09Bibliographically approved
Wei, J., Fridman, E. & Johansson, K. H. (2019). A PDE approach to deployment of mobile agents under leader relative position measurements. Automatica, 106, 47-53
Open this publication in new window or tab >>A PDE approach to deployment of mobile agents under leader relative position measurements
2019 (English)In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 106, p. 47-53Article in journal (Refereed) Published
Abstract [en]

We study the deployment of a first-order multi-agent system over a desired smooth curve in 2D or 3D space. We assume that the agents have access to the local information of the desired curve and their relative positions with respect to their closest neighbors, whereas in addition a leader is able to measure his relative position with respect to the desired curve. For the case of an open C-2 curve, we consider two boundary leaders that use boundary instantaneous static output-feedback controllers. For the case of a closed C-2 curve we assume that the leader transmits his measurement to other agents through a communication network. The resulting closed-loop system is modeled as a heat equation with a delayed (due to the communication) boundary state, where the state is the relative position of the agents with respect to the desired curve. By choosing appropriate controller gains (the diffusion coefficient and the gain multiplying the leader state), we can achieve any desired decay rate provided the delay is small enough. The advantage of our approach is in the simplicity of the control law and the conditions. Numerical example illustrates the efficiency of the method.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Distributed parameters systems, Multi-agent systems, Time delays, Deployment
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-255403 (URN)10.1016/j.automatica.2019.04.040 (DOI)000473380000006 ()2-s2.0-85065528878 (Scopus ID)
Note

QC 20190814

Available from: 2019-08-14 Created: 2019-08-14 Last updated: 2019-08-14Bibliographically approved
Milosevic, J., Sandberg, H. & Johansson, K. H. (2019). A Security Index for Actuators Based on Perfect Undetectability: Properties and Approximation. In: 2018 56th Annual Allerton Conference on Communication, Control, and Computing, Allerton 2018: . Paper presented at 56th Annual Allerton Conference on Communication, Control, and Computing, Allerton 2018, 2 October 2018 through 5 October 2018 (pp. 235-241). Institute of Electrical and Electronics Engineers Inc.
Open this publication in new window or tab >>A Security Index for Actuators Based on Perfect Undetectability: Properties and Approximation
2019 (English)In: 2018 56th Annual Allerton Conference on Communication, Control, and Computing, Allerton 2018, Institute of Electrical and Electronics Engineers Inc. , 2019, p. 235-241Conference paper, Published paper (Refereed)
Abstract [en]

A novel security index based on the definition of perfect undetectability is proposed. The index is a tool that can help a control system operator to localize the most vulnerable actuators in the network. In particular, the security index of actuator i represents the minimal number of sensors and actuators that needs to be compromised in addition to i, such that a perfectly undetectable attack is possible. A method for computing this index for small scale systems is derived, and difficulties with the index once the system is of large scale are outlined. An upper bound for the index that overcomes these difficulties is then proposed. The theoretical developments are illustrated on a numerical example. 

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2019
Keywords
Computer programming, Computer science, Control engineering, Security indices, Sensors and actuators, Small-scale systems, System operator, Theoretical development, Upper Bound, Actuators
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-252077 (URN)10.1109/ALLERTON.2018.8635906 (DOI)000461021200034 ()2-s2.0-85062843906 (Scopus ID)
Conference
56th Annual Allerton Conference on Communication, Control, and Computing, Allerton 2018, 2 October 2018 through 5 October 2018
Note

QC 20190801

Available from: 2019-08-01 Created: 2019-08-01 Last updated: 2019-08-01Bibliographically approved
Dibaji, S. M., Pirani, M., Flamholz, D. B., Annaswamy, A. M., Johansson, K. H. & Chakrabortty, A. (2019). A systems and control perspective of CPS security. Annual Reviews in Control, 47, 394-411
Open this publication in new window or tab >>A systems and control perspective of CPS security
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2019 (English)In: Annual Reviews in Control, ISSN 1367-5788, E-ISSN 1872-9088, Vol. 47, p. 394-411Article, review/survey (Refereed) Published
Abstract [en]

The comprehensive integration of instrumentation, communication, and control into physical systems has led to the study of Cyber-Physical Systems (CPSs), a field that has recently garnered increased attention. A key concern that is ubiquitous in CPS is a need to ensure security in the face of cyber attacks. In this paper, we carry out a survey of systems and control methods that have been proposed for the security of CPS. We classify these methods into three categories based on the type of defense proposed against the cyberattacks: prevention, resilience, and detection & isolation. A unified threat assessment metric is proposed in order to evaluate how CPS security is achieved in each of these three cases. Also surveyed are the risk assessment tools and the effect of network topology on CPS security. Furthermore, an emphasis has been placed on power and transportation applications in the overall survey.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Cyber-physical systems, Cyber-security, Cyber-physical security, Secure control, Resilient control
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-255516 (URN)10.1016/j.arcontrol.2019.04.011 (DOI)000474680200027 ()2-s2.0-85065925819 (Scopus ID)
Note

QC 20191017

Available from: 2019-10-17 Created: 2019-10-17 Last updated: 2019-10-17Bibliographically approved
McCann, J. A., Picco, G. P., Gluhak, A., Johansson, K. H., Törngren, M. & Gide, L. (2019). Connected Things Connecting Europe. Communications of the ACM, 62(4), 46-51
Open this publication in new window or tab >>Connected Things Connecting Europe
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2019 (English)In: Communications of the ACM, ISSN 0001-0782, E-ISSN 1557-7317, Vol. 62, no 4, p. 46-51Article in journal, Editorial material (Refereed) Published
Place, publisher, year, edition, pages
Association for Computing Machinery (ACM), 2019
National Category
Computer Sciences
Identifiers
urn:nbn:se:kth:diva-249869 (URN)10.1145/3312563 (DOI)000462529000019 ()2-s2.0-85063420959 (Scopus ID)
Note

QC 20190424

Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-10-09Bibliographically approved
Yang, T., Wu, D., Fang, H., Ren, W., Wang, H., Hong, Y. & Johansson, K. H. (2019). Distributed Energy Resource Coordination Over Time-Varying Directed Communication Networks. IEEE Transactions on Big Data, 6(3), 1124-1134
Open this publication in new window or tab >>Distributed Energy Resource Coordination Over Time-Varying Directed Communication Networks
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2019 (English)In: IEEE Transactions on Big Data, ISSN 2325-5870, E-ISSN 2168-6750, Vol. 6, no 3, p. 1124-1134Article in journal (Refereed) Published
Abstract [en]

In this paper, we consider the optimal coordination problem for distributed energy resources (DERs), including distributed generators and energy storages. We first propose an algorithm based on the push-sum and gradient method to solve the optimal DER coordination problem in a distributed manner. In the proposed algorithm, each DER only maintains a set of variables and updates them through information exchange with a few neighboring DERs over a time-varying directed communication network. We show that the proposed distributed algorithm with appropriately chosen diminishing step sizes solves the optimal DER coordination problem if the time-varying directed communication network is uniformly jointly strongly connected. Moreover, in order to improve the convergence speed and to reduce the communication burden, we propose an accelerated distributed algorithm with a fixed step size. We show that the new proposed algorithm exponentially solves the optimal DER coordination problem if the cost functions satisfy an additional assumption and the selected step size is less than a certain critical value. Both proposed distributed algorithms are validated and evaluated using the IEEE 39-bus system.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Distributed coordination, energy storage (ES), multiagent systems, multistep optimization, push-sum and gradient method, smart grid
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-261978 (URN)10.1109/TCNS.2019.2921284 (DOI)000487200900019 ()
Note

QC 20191014

Available from: 2019-10-14 Created: 2019-10-14 Last updated: 2019-10-14Bibliographically approved
Yi, X., Yang, T., Wu, J. & Johansson, K. H. (2019). Distributed event-triggered control for global consensus of multi-agent systems with input saturation. Automatica, 100, 1-9
Open this publication in new window or tab >>Distributed event-triggered control for global consensus of multi-agent systems with input saturation
2019 (English)In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 100, p. 1-9Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Event-triggered control, Global consensus, Input saturation, Multi-agent systems
National Category
Computer and Information Sciences
Identifiers
urn:nbn:se:kth:diva-244103 (URN)10.1016/j.automatica.2018.10.032 (DOI)000456902200001 ()2-s2.0-85056671408 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research Swedish Research Council
Note

QC 20190219

Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-02-19Bibliographically approved
Yi, X., Liu, K., Dimarogonas, D. V. & Johansson, K. H. (2019). Dynamic Event-Triggered and Self-Triggered Control for Multi-agent Systems. IEEE Transactions on Automatic Control, 64(8), 3300-3307
Open this publication in new window or tab >>Dynamic Event-Triggered and Self-Triggered Control for Multi-agent Systems
2019 (English)In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 64, no 8, p. 3300-3307Article in journal (Refereed) Published
Abstract [en]

We propose two novel dynamic event-triggered control laws to solve the average consensus problem for first-order continuous-time multiagent systems over undirected graphs. Compared with the most existing triggering laws, the proposed laws involve internal dynamic variables, which play an essential role in guaranteeing that the triggering time sequence does not exhibit Zeno behavior. Moreover, some existing triggering laws are special cases of ours. For the proposed self-triggered algorithm, continuous agent listening is avoided as each agent predicts its next triggering time and broadcasts it to its neighbors at the current triggering time. Thus, each agent only needs to sense and broadcast at its triggering times, and to listen to and receive incoming information from its neighbors at their triggering times. It is proved that the proposed triggering laws make the state of each agent converge exponentially to the average of the agents' initial states if and only if the underlying graph is connected. Numerical simulations are provided to illustrate the effectiveness of the theoretical results.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Consensus, dynamic event-triggered control, multiagent systems, self-triggered control
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-257567 (URN)10.1109/TAC.2018.2874703 (DOI)000478694300016 ()2-s2.0-85054510419 (Scopus ID)
Note

QC 20190923

Available from: 2019-09-23 Created: 2019-09-23 Last updated: 2019-09-23Bibliographically approved
Xia, W., Liu, J., Cao, M., Johansson, K. H. & Basar, T. (2019). Generalized Sarymsakov Matrices. IEEE TRANSACTIONS ON AUTOMATIC CONTROL, 64(8), 3085-3100
Open this publication in new window or tab >>Generalized Sarymsakov Matrices
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2019 (English)In: IEEE TRANSACTIONS ON AUTOMATIC CONTROL, Vol. 64, no 8, p. 3085-3100Article in journal (Refereed) Published
Abstract [en]

Within the set of stochastic, indecomposable, aperiodic (SIA) matrices, the class of Sarymsakov matrices is the largest known subset that is closed under matrix multiplication, and more critically whose compact subsets are all consensus sets. This paper shows that a larger subset with these two properties can be obtained by generalizing the standard definition for Sarymsakov matrices. The generalization is achieved by introducing the notion of the SIA index of a stochastic matrix, whose value is 1 for Sarymsakov matrices, and then exploring those stochastic matrices with larger SIA indices. In addition to constructing the larger set, this paper introduces another class of generalized Sarymsakov matrices, which contains matrices that are not SIA, and studies their products. Sufficient conditions are provided for an infinite product of matrices from this class, converging to a rank-one matrix. Finally, as an application of the results just described and to confirm their usefulness, a necessary and sufficient combinatorial condition, the "avoiding set condition," for deciding whether or not a compact set of stochastic matrices is a consensus set is revisited. In addition, a necessary and sufficient combinatorial condition is established for deciding whether or not a compact set of doubly stochastic matrices is a consensus set.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Cooperative control, doubly stochastic matrices, multi-agent systems, products of stochastic matrices, Sarymsakov matrices, GROOT MH, 1974, JOURNAL OF THE AMERICAN STATISTICAL ASSOCIATION, V69, P118 uri Behrouz, 2014, IEEE TRANSACTIONS ON AUTOMATIC CONTROL, V59, P437 ndrickx Julien M., 2014, 2014 IEEE 53RD ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC)53rd IEEE Annual Conference on Decision and Control (CDC), DEC 15-17, 2014, Los Angeles, CA, P2118 u Ji, 2012, 2012 IEEE 51ST ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC)51st IEEE Annual Conference on Decision and Control (CDC), DEC 10-13, 2012, HI, P3991 itsiklis J. N., 1984, Problems in decentralized decision making and computation, ndrickx Julien M., 2011, 2011 50TH IEEE CONFERENCE ON DECISION AND CONTROL AND EUROPEAN CONTROL CONFERENCE (CDC-ECC)50th IEEE Conference of Decision and Control (CDC)/European Control Conference (ECC), DEC 12-15, 2011, Orlando, FL, P5070 u Ji, 2015, 2015 54TH IEEE CONFERENCE ON DECISION AND CONTROL (CDC)54th IEEE Conference on Decision and Control (CDC), DEC 15-18, 2015, Osaka, JAPAN, P2835 vaei Javad, 2012, IEEE TRANSACTIONS ON AUTOMATIC CONTROL, V57, P19 ao L, 2005, 2005 Fourth International Symposium on Information Processing in Sensor Networks4th International Symposium on Information Processing in Sensor Networks, APR 25-27, 2005, Los Angeles, CA, P63 uri Behrouz, 2012, IEEE TRANSACTIONS ON AUTOMATIC CONTROL, V57, P2718
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-257569 (URN)10.1109/TAC.2018.2878476 (DOI)000478694300001 ()2-s2.0-85055720326 (Scopus ID)
Note

QC 20190923

Available from: 2019-09-23 Created: 2019-09-23 Last updated: 2019-09-23Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9940-5929

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