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| 2. |
- Leong, Alex S., et al.
(author)
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On Remote State Estimation in the Presence of an Eavesdropper
- 2017
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In: IFAC-PapersOnLine. - : Elsevier. ; , s. 7339-7344
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Conference paper (peer-reviewed)abstract
- This paper studies a remote state estimation problem in the presence of an eavesdropper. A sensor transmits local state estimates over a packet dropping link to a remote estimator, which at the same time can be overheard by an eavesdropper with a certain probability. The objective is to determine when the sensor should transmit, in order to minimize the estimation error covariance at the remote estimator, while trying to keep the eavesdropper error covariance above a certain level. This is done by solving an optimization problem that minimizes a linear combination of the expected estimation error covariance and the negative of the expected eavesdropper error covariance. Structural results on the optimal transmission policy are derived, and shown to exhibit thresholding behaviour in the estimation error covariances. In the infinite horizon situation, it is shown that with unstable systems one can keep the expected estimation error covariance bounded while the expected eavesdropper error covariance becomes unbounded. (C) 2017, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
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| 3. |
- Demirel, Burak, et al.
(author)
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Optimal Control of Linear Systems With Limited Control Actions : Threshold-Based Event-Triggered Control
- 2018
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In: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870. ; 5:3, s. 1275-1286
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Journal article (peer-reviewed)abstract
- We consider a finite-horizon linear-quadratic optimal control problem where only a limited number of control messages are allowed for sending from the controller to the actuator. To restrict the number of control actions computed and transmitted by the controller, we employ a threshold-based event-triggering mechanism that decides whether or not a control message needs to be calculated and delivered. Due to the nature of threshold-based event-triggering algorithms, finding the optimal control sequence requires minimizing a quadratic cost function over a nonconvex domain. In this paper, we first provide an exact solution to this nonconvex problem by solving an exponential number of quadratic programs. To reduce computational complexity, we then propose two efficient heuristic algorithms based on greedy search and the alternating direction method of multipliers technique. Later, we consider a receding horizon control strategy for linear systems controlled by event-triggered controllers, and we further provide a complete stability analysis of receding horizon control that uses finite-horizon optimization in the proposed class. Numerical examples testify to the viability of the presented design technique.
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| 4. |
- Demirel, Burak, et al.
(author)
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Threshold Optimization of Event-Triggered Multi-Loop Control Systems
- 2016
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In: 2016 13TH INTERNATIONAL WORKSHOP ON DISCRETE EVENT SYSTEMS (WODES). - : IEEE conference proceedings. - 9781509041909 ; , s. 203-210
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Conference paper (peer-reviewed)abstract
- This paper considers multiple linear stochastic control systems whose feedback loops are closed over a shared communication medium. A threshold-based event-triggering rule is used to transmit control commands from the controllers to the actuators, and network access is arbitrated using a static priority mechanism. Under these conditions, we study deadbeat control laws and compute the expected linear-quadratic loss of the closed-loop system as a function of the event-thresholds of the individual loops. Also, we present analytical expressions that quantify the trade-off between the communication cost and the control performance of such event-triggered control systems. Using a multi-dimensional exhaustive search method, we determine the set of event thresholds that attains the minimal expected linear-quadratic loss of the closed-loop systems. Simulation studies highlight the trade-off between the communication and control cost.
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| 5. |
- Ding, Kemi, et al.
(author)
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A multi-channel transmission schedule for remote state estimation under DoS attacks
- 2017
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In: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 78, s. 194-201
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Journal article (peer-reviewed)abstract
- This paper considers a cyber-physical system (CPS) under denial-of-service (DoS) attacks. The measurements of a sensor are transmitted to a remote estimator over a multi-channel network, which may be congested by a malicious attacker. Among these multiple communication paths with different characteristics and properties at each time step, the sensor needs to choose a single channel for sending data packets while reducing the probability of being attacked. In the meanwhile, the attacker needs to decide the target channel to jam under an energy budget constraint. To model this interactive decision making process between the two sides, we formulate a two-player zero-sum stochastic game framework. A Nash Q-learning algorithm is proposed to tackle the computation complexity when solving the optimal strategies for both players. Numerical examples are provided to illustrate the obtained results.
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| 6. |
- Ding, Kemi, et al.
(author)
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A Secure Cross-Layer Design for Remote Estimation under DoS Attack : When Multi-sensor meets Multi-channel
- 2016
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In: 2016 IEEE 55Th Conference On Decision And Control (CDC). - New York : IEEE. - 9781509018376 ; , s. 6297-6302
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Conference paper (peer-reviewed)abstract
- This paper considers security issues of a cyberphysical system (CPS) under denial-of-service (DoS) attacks. The measurements of multiple sensors are transmitted to a remote estimator over a multi-channel network, which may be congested by an intelligent attacker. Aiming at improving the estimation accuracy, we first propose a novel aggregation scheme for the estimator to produce accurate state estimates, from which we obtain a closed-form expression of the expected estimation error covariance. We further develop a sensor attacker game to design the cooperative and defensive channel selection strategy, which avoids the sensors being attacked in an energy-efficient way. Numerical examples are provided to illustrate the developed results.
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| 7. |
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| 8. |
- Ding, K, et al.
(author)
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Stochastic game in remote estimation under DoS attacks
- 2017
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In: IEEE Control Systems Letters. - 2475-1456. ; 1:1, s. 146-151
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Journal article (peer-reviewed)abstract
- This letter studies remote state estimation under denial-of-service (DoS) attacks. A sensor transmits its local estimate of an underlying physical process to a remote estimator via a wireless communication channel. A DoS attacker is capable to interfere the channel and degrades the remote estimation accuracy. Considering the tactical jamming strategies played by the attacker, the sensor adjusts its transmission power. This interactive process between the sensor and the attacker is studied in the framework of a zero-sum stochastic game. To derive their optimal power schemes, we first discuss the existence of stationary Nash equilibrium for this game. We then present the monotone structure of the optimal strategies, which helps reduce the computational complexity of the stochastic game algorithm. Numerical examples are provided to illustrate the obtained results.
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| 9. |
- Jurado, Isabel, et al.
(author)
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Cooperative Dynamic MPC for NCSs
- 2013
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In: Distributed MPC Made Easy. - : Springer-Verlag New York.
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Book chapter (peer-reviewed)abstract
- This work studies cooperative MPC for Networked Control Systems with multiple wireless nodes. Communication between nodes is affected by random packet dropouts. An algorithm is presented to decide at each time instant which nodes will calculate the control input and which will only relay data. The nodes chosen to calculate the control values solve a cooperative MPC by communicating with their neighbors. This algorithm makes the control architecture flexible by adapting it to the possible changes in the network conditions.
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| 10. |
- Jurado, Isabel, et al.
(author)
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Cooperative Dynamic MPC for NCSs
- 2013
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In: Distributed MPC Made Easy. - Berlin, Heidelberg Tyskland : Springer-Verlag.
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Book chapter (peer-reviewed)
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