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Publications (10 of 637) Show all publications
Yi, X., Li, X., Xie, L. & Johansson, K. H. (2020). Distributed Online Convex Optimization With Time-Varying Coupled Inequality Constraints. IEEE Transactions on Signal Processing, 68, 731-746
Open this publication in new window or tab >>Distributed Online Convex Optimization With Time-Varying Coupled Inequality Constraints
2020 (English)In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 68, p. 731-746Article in journal (Refereed) Published
Abstract [en]

This paper considers distributed online optimization with time-varying coupled inequality constraints. The global objective function is composed of local convex cost and regularization functions and the coupled constraint function is the sum of local convex functions. Adistributed online primal-dual dynamic mirror descent algorithm is proposed to solve this problem, where the local cost, regularization, and constraint functions are held privately and revealed only after each time slot. Without assuming Slater's condition, we first derive regret and constraint violation bounds for the algorithm and show how they depend on the stepsize sequences, the accumulated dynamic variation of the comparator sequence, the number of agents, and the network connectivity. As a result, under some natural decreasing stepsize sequences, we prove that the algorithm achieves sublinear dynamic regret and constraint violation if the accumulated dynamic variation of the optimal sequence also grows sublinearly. We also prove that the algorithm achieves sublinear static regret and constraint violation under mild conditions. Assuming Slater's condition, we show that the algorithm achieves smaller bounds on the constraint violation. In addition, smaller bounds on the static regret are achieved when the objective function is strongly convex. Finally, numerical simulations are provided to illustrate the effectiveness of the theoretical results.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2020
Keywords
Distributed optimization, dynamic mirror descent, online optimization, time-varying constraints
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-268797 (URN)10.1109/TSP.2020.2964200 (DOI)000511378400001 ()
Note

QC 20200221

Available from: 2020-02-21 Created: 2020-02-21 Last updated: 2020-02-21Bibliographically approved
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
Li, Y., Johansson, K. H. & Mårtensson, J. (2019). A hierarchical control system for smart parking lots with automated vehicles: Improve efficiency by leveraging prediction of human drivers. In: Proceedings 2019 18TH EUROPEAN CONTROL CONFERENCE (ECC): . Paper presented at 18th European Control Conference (ECC), Naples, ITALY, JUN 25-28, 2019 (pp. 2675-2681). IEEE
Open this publication in new window or tab >>A hierarchical control system for smart parking lots with automated vehicles: Improve efficiency by leveraging prediction of human drivers
2019 (English)In: Proceedings 2019 18TH EUROPEAN CONTROL CONFERENCE (ECC), IEEE , 2019, p. 2675-2681Conference paper, Published paper (Refereed)
Abstract [en]

In this work, we introduce a hierarchical architecture for management of multiple automated vehicles in a parking lot provided the existence of human-driven vehicles. The proposed architecture consists of three layers: behavior prediction, vehicle coordination and maneuver control, with the first two sitting in the infrastructure and the third one equipped on individual vehicles. We assume all three layers share a consistent view of the environment by considering it as a grid world. The grid occupancy is modeled by the prediction layer via collecting information from automated vehicles and predicting human-driven vehicles. The coordination layer assigns parking spots and grants permissions for vehicles to move. The vehicle control embraces the distributed model predictive control (MPC) technique to resolve local conflicts occurred due to the simplified vehicle models used in the design of the prediction and coordination layers. Numerical evaluation shows the effectiveness of the proposed control system.

Place, publisher, year, edition, pages
IEEE, 2019
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-263395 (URN)10.23919/ECC.2019.8796055 (DOI)000490488302111 ()2-s2.0-85071574054 (Scopus ID)
Conference
18th European Control Conference (ECC), Naples, ITALY, JUN 25-28, 2019
Note

QC 20191113

Available from: 2019-11-13 Created: 2019-11-13 Last updated: 2019-11-13Bibliographically 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
van de Hoef, S., Mårtensson, J., Dimarogonas, D. V. & Johansson, K. H. (2019). A predictive framework for dynamic heavy-duty vehicle platoon coordination. ACM Transactions on Cyber-Physical Systems, 4(1), Article ID A5.
Open this publication in new window or tab >>A predictive framework for dynamic heavy-duty vehicle platoon coordination
2019 (English)In: ACM Transactions on Cyber-Physical Systems, ISSN 2378-962X, Vol. 4, no 1, article id A5Article in journal (Refereed) Published
Abstract [en]

This article describes a system to facilitate dynamic en route formation of heavy-duty vehicle platoons with the goal of reducing fuel consumption. Safe vehicle platooning is a maturing technology that leverages modern sensor, control, and communication technology to automatically regulate the inter-vehicle distances. Truck platooning has been shown to reduce fuel consumption through slipstreaming by up to 10% under realistic highway-driving conditions. To further benefit from this technology, a platoon coordinator is proposed, which interfaces with fleet management systems and suggests how platoons can be formed in a fuel-efficient manner over a large region. The coordinator frequently updates the plans to react to newly available information. This way, it requires a minimum of customization with respect to the logistic operations.We discuss the system architecture in detail and introduce important underlying methodological foundations. Plans are derived in computationally tractable stages optimizing fuel savings from platooning. The effectiveness of this approach is verified in a simulation study. It shows that the coordinated platooning system can improve over spontaneously occurring platooning even under the presence of disturbances. A real demonstrator has also been developed. We present data from an experiment in which three vehicles were coordinated to form a platoon on public highways under normal traffic conditions. It demonstrates the feasibility of coordinated en route platoon formation with current communication and on-board technology. Simulations and experiments support that the proposed system is technically feasible and a potential solution to the problem of using vehicle platooning in an operational context.

Place, publisher, year, edition, pages
Association for Computing Machinery, 2019
Keywords
Cooperative adaptive cruise control, Platooning, Road freight transport, Adaptive cruise control, Fleet operations, Freight transportation, Fuel economy, Fuels, Communication technologies, Driving conditions, Fleet management system, Heavy duty vehicles, System architectures, Vehicle to vehicle communications
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-268046 (URN)10.1145/3299110 (DOI)2-s2.0-85074896008 (Scopus ID)
Note

QC 20200326

Available from: 2020-03-26 Created: 2020-03-26 Last updated: 2020-03-26Bibliographically 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 (IEEE)
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 (IEEE), 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 (IEEE), 2019
Series
Annual Allerton Conference on Communication Control and Computing, ISSN 2474-0195
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)978-1-5386-6596-1 (ISBN)
Conference
56th Annual Allerton Conference on Communication, Control, and Computing, Allerton 2018, 2 October 2018 through 5 October 2018
Projects
CERCES
Note

QC 20190801

Available from: 2019-08-01 Created: 2019-08-01 Last updated: 2019-12-09Bibliographically approved
Yang, T., Yi, X., Wu, J., Yuan, Y., Wu, D., Meng, Z., . . . Johansson, K. H. (2019). A survey of distributed optimization. Annual Reviews in Control, 47, 278-305
Open this publication in new window or tab >>A survey of distributed optimization
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2019 (English)In: Annual Reviews in Control, ISSN 1367-5788, E-ISSN 1872-9088, Vol. 47, p. 278-305Article, review/survey (Refereed) Published
Abstract [en]

In distributed optimization of multi-agent systems, agents cooperate to minimize a global function which is a sum of local objective functions. Motivated by applications including power systems, sensor networks, smart buildings, and smart manufacturing, various distributed optimization algorithms have been developed. In these algorithms, each agent performs local computation based on its own information and information received from its neighboring agents through the underlying communication network, so that the optimization problem can be solved in a distributed manner. This survey paper aims to offer a detailed overview of existing distributed optimization algorithms and their applications in power systems. More specifically, we first review discrete-time and continuous-time distributed optimization algorithms for undirected graphs. We then discuss how to extend these algorithms in various directions to handle more realistic scenarios. Finally, we focus on the application of distributed optimization in the optimal coordination of distributed energy resources. 

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Distributed optimization, Coordination of distributed energy resources
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-255519 (URN)10.1016/j.arcontrol.2019.05.006 (DOI)000474680200022 ()2-s2.0-85065858312 (Scopus ID)
Note

QC 20191022

Available from: 2019-10-22 Created: 2019-10-22 Last updated: 2019-10-22Bibliographically 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
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9940-5929

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