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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
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
Wei, J., Yi, X., Sandberg, H. & Johansson, K. H. (2019). Nonlinear Consensus Protocols With Applications to Quantized Communication and Actuation. IEEE Transactions on Big Data, 6(2), 598-608
Open this publication in new window or tab >>Nonlinear Consensus Protocols With Applications to Quantized Communication and Actuation
2019 (English)In: IEEE Transactions on Big Data, ISSN 2325-5870, E-ISSN 2168-6750, Vol. 6, no 2, p. 598-608Article in journal (Refereed) Published
Abstract [en]

Nonlinearities are present in all real applications. Two types of general nonlinear consensus protocols are considered in this paper, namely, the systems with nonlinear communication and actuator constraints. The solutions of the systems are understood in the sense of Filippov to handle the possible discontinuity of the controllers. For each case, we prove the asymptotic stability of the systems with minimal assumptions on the nonlinearity, for both directed and undirected graphs. These results extend the literature to more general nonlinear dynamics and topologies. As applications of established theorems, we interpret the results on quantized consensus protocols.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Keywords
Networks of autonomous agents, nonlinear systems, nonsmooth analysis, stability
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-254088 (URN)10.1109/TCNS.2018.2860461 (DOI)000469874200012 ()2-s2.0-85050615718 (Scopus ID)
Note

QC 20190625

Available from: 2019-06-25 Created: 2019-06-25 Last updated: 2019-06-25Bibliographically approved
Xia, W., Shi, G., Meng, Z., Cao, M. & Johansson, K. H. (2019). Persis en Flows in Deterministic Chains. IEEE Transactions on Automatic Control, 64(7), 2766-2781
Open this publication in new window or tab >>Persis en Flows in Deterministic Chains
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2019 (English)In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 64, no 7, p. 2766-2781Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Consensus, multiagent systems, persistent graphs, products of stochastic matrices
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-255430 (URN)10.1109/TAC.2019.2893974 (DOI)000473489700009 ()2-s2.0-85068126768 (Scopus ID)
Note

QC 20190820

Available from: 2019-08-20 Created: 2019-08-20 Last updated: 2019-08-20Bibliographically approved
Jin, M., Lavaei, J. & Johansson, K. H. (2019). Power Grid AC-Based State Estimation: Vulnerability Analysis Against Cyber Attacks. IEEE Transactions on Automatic Control, 64(5), 1784-1799
Open this publication in new window or tab >>Power Grid AC-Based State Estimation: Vulnerability Analysis Against Cyber Attacks
2019 (English)In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 64, no 5, p. 1784-1799Article in journal (Refereed) Published
Abstract [en]

To ensure grid efficiency and reliability, power system operators continuously monitor the operational characteristics of the grid through a critical process called state estimation (SE), which performs the task by filtering and fusing various measurements collected from grid sensors. This study analyzes the vulnerability of the key operation module, namely ac-based SE, against potential cyber attacks on data integrity, also known as false data injection attack (FDIA). A general form of FDIA can be formulated as an optimization problem, whose objective is to find a stealthy and sparse data injection vector on the sensor measurements with the aim of making the state estimate spurious and misleading. Due to the nonlinear ac measurement model and the cardinality constraint, the problem includes both continuous and discrete nonlinearities. To solve the FDIA problem efficiently, we propose a novel convexification framework based on semidefinite programming (SDP). By analyzing a globally optimal SDP solution, we delineate the "attackable region" for any given set of measurement types and grid topology, where the spurious state can be falsified by FDIA. Furthermore, we prove that the attack is stealthy and sparse, and derive performance bounds. Simulation results on various IEEE test cases indicate the efficacy of the proposed convexification approach. From the grid protection point of view, the results of this study can be used to design a security metric for the current practice against cyber attacks, redesign the bad data detection scheme, and inform proposals of grid hardening. From a theoretical point of view, the proposed framework can be used for other nonconvex problems in power systems and beyond.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Keywords
Convexification, cyber attack, false data injection attack (FDIA), nonconvex optimization, power system, resilience, security, semidefinite programming (SDP), state estimation (SE)
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-254113 (URN)10.1109/TAC.2018.2852774 (DOI)000466226500002 ()2-s2.0-85049487678 (Scopus ID)
Note

QC 20190624

Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2019-06-24Bibliographically approved
Wiese, M., Oechtering, T. J., Johansson, K. H., Papadimitratos, P., Sandberg, H. & Skoglund, M. (2019). Secure Estimation and Zero-Error Secrecy Capacity. IEEE Transactions on Automatic Control, 64(3), 1047-1062
Open this publication in new window or tab >>Secure Estimation and Zero-Error Secrecy Capacity
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2019 (English)In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 64, no 3, p. 1047-1062Article in journal (Refereed) Published
Abstract [en]

We study the problem of securely estimating the states of an unstable dynamical system subject to non-stochastic disturbances. The estimator obtains all its information through an uncertain channel, which is subject to nonstochastic disturbances as well, and an eavesdropper obtains a disturbed version of the channel inputs through a second uncertain channel. An encoder observes and block encodes the states in such a way that, upon sending the generated codeword, the estimator's error is bounded and a security criterion is satisfied, thereby ensuring that the eavesdropper obtains as little state information as possible. Two security criteria are considered and discussed with the help of a numerical example. A sufficient condition on the uncertain wiretap channel, i.e., the pair formed by the uncertain channel from the encoder to the estimator and the uncertain channel from the encoder to the eavesdropper is derived, which ensures that a bounded estimation error and security are achieved. This condition is also shown to be necessary for a subclass of uncertain wiretap channels. To formulate the condition, the zero-error secrecy capacity of uncertain wiretap channels is introduced, i.e., the maximal rate at which data can be transmitted from the encoder to the estimator in such a way that the eavesdropper is unable to reconstruct the transmitted data. Finally, the zero-error secrecy capacity of uncertain wiretap channels is studied.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Secure state estimation, uncertain wiretap channel, zero-error secrecy capacity
National Category
Computer and Information Sciences
Identifiers
urn:nbn:se:kth:diva-247828 (URN)10.1109/TAC.2018.2849620 (DOI)000460415600012 ()2-s2.0-85048871914 (Scopus ID)
Note

QC 20190326

Available from: 2019-03-26 Created: 2019-03-26 Last updated: 2019-03-26Bibliographically approved
Guo, Z., Shi, D., Johansson, K. H. & Shi, L. (2019). Worst-Case Innovation-Based Integrity Attacks With Side Information on mote State Estimation. IEEE Transactions on Big Data, 6(1), 48-59
Open this publication in new window or tab >>Worst-Case Innovation-Based Integrity Attacks With Side Information on mote State Estimation
2019 (English)In: IEEE Transactions on Big Data, ISSN 2325-5870, E-ISSN 2168-6750, Vol. 6, no 1, p. 48-59Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Keywords
Cyber-physical system (CPS) security, integrity attack, remote state estimation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-248352 (URN)10.1109/TCNS.2018.2793664 (DOI)000461857300005 ()2-s2.0-85041688663 (Scopus ID)
Note

QC 20190502

Available from: 2019-05-02 Created: 2019-05-02 Last updated: 2019-05-02Bibliographically approved
Fang, S., Ishii, H., Chen, J. & Johansson, K. H. (2018). A Frequency-Domain Characterization of Optimal Error Covariance for the Kalman-Bucy Filter. In: 2018 IEEE CONFERENCE ON DECISION AND CONTROL (CDC): . Paper presented at 57th IEEE Conference on Decision and Control (CDC), DEC 17-19, 2018, Miami Beach, FL (pp. 6366-6371). IEEE
Open this publication in new window or tab >>A Frequency-Domain Characterization of Optimal Error Covariance for the Kalman-Bucy Filter
2018 (English)In: 2018 IEEE CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2018, p. 6366-6371Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, we discover that the trace of the division of the optimal output estimation error covariance over the noise covariance attained by the Kalman-Bucy filter can be explicitly expressed in terms of the plant dynamics and noise statistics in a frequency-domain integral characterization. Towards this end, we examine the algebraic Riccati equation associated with Kalman-Bucy filtering using analytic function theory and relate it to the Bode integral. Our approach features an alternative, frequency-domain framework for analyzing algebraic Riccati equations and reduces to various existing related results.

Place, publisher, year, edition, pages
IEEE, 2018
Series
IEEE Conference on Decision and Control, ISSN 0743-1546
National Category
Computer and Information Sciences
Identifiers
urn:nbn:se:kth:diva-245013 (URN)10.1109/CDC.2018.8619084 (DOI)000458114805140 ()2-s2.0-85062165780 (Scopus ID)978-1-5386-1395-5 (ISBN)
Conference
57th IEEE Conference on Decision and Control (CDC), DEC 17-19, 2018, Miami Beach, FL
Note

QC 20190305

Available from: 2019-03-05 Created: 2019-03-05 Last updated: 2019-04-11Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9940-5929

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