| 1. |
- Ahlén, Anders, et al.
(författare)
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Towards Wireless Control in Industrial Process Automation : A Case Study at a Paper Mill
- 2019
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Ingår i: IEEE CONTROL SYSTEMS MAGAZINE. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1066-033X .- 1941-000X. ; 39:5, s. 36-57
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Tidskriftsartikel (refereegranskat)abstract
- Wireless sensors and networks are used only occasionally in current control loops in the process industry. With rapid developments in embedded and highperformance computing, wireless communication, and cloud technology, drastic changes in the architecture and operation of industrial automation systems seem more likely than ever. These changes are driven by ever-growing demands on production quality and flexibility. However, as discussed in "Summary," there are several research obstacles to overcome. The radio communication environment in the process industry is often troublesome, as the environment is frequently cluttered with large metal objects, moving machines and vehicles, and processes emitting radio disturbances [1], [2]. The successful deployment of a wireless control system in such an environment requires careful design of communication links and network protocols as well as robust and reconfigurable control algorithms.
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| 2. |
- Wei, Jieqiang, et al.
(författare)
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Nonlinear Consensus Protocols With Applications to Quantized Communication and Actuation
- 2019
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870. ; 6:2, s. 598-608
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Fang, Song, et al.
(författare)
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Two-Way Coding in Control Systems Under Injection Attacks : From Attack Detection to Attack Correction
- 2019
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Ingår i: ICCPS '19. - New York, NY, USA : Association for Computing Machinery (ACM). ; , s. 141-150
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Konferensbidrag (refereegranskat)abstract
- In this paper, we introduce the method of two-way coding, a concept originating in communication theory characterizing coding schemes for two-way channels, into (networked) feedback control systems under injection attacks. We first show that the presence of two-way coding can distort the perspective of the attacker on the control system. In general, the distorted viewpoint on the attacker side as a consequence of two-way coding will facilitate detecting the attacks, or restricting what the attacker can do, or even correcting the attack effect. In the particular case of zero-dynamics attacks, if the attacks are to be designed according to the original plant, then they will be easily detected; while if the attacks are designed with respect to the equivalent plant as viewed by the attacker, then under the additional assumption that the plant is stabilizable by static output feedback, the attack effect may be corrected in steady state.
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| 4. |
- He, Xingkang, et al.
(författare)
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Secure Distributed Filtering for Unstable Dynamics Under Compromised Observations
- 2019
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Ingår i: 2019 IEEE 58th Conference on Decision and Control (CDC). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 5344-5349
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Konferensbidrag (refereegranskat)abstract
- In this paper, we consider a secure distributed filtering problem for linear time-invariant systems with bounded noises and unstable dynamics under compromised observations. A malicious attacker is able to compromise a subset of the agents and manipulate the observations arbitrarily. We first propose a recursive distributed filter consisting of two parts at each time. The first part employs a saturation like scheme, which gives a small gain if the innovation is too large. The second part is a consensus operation of state estimates among neighboring agents. A sufficient condition is then established for the boundedness of estimation error, which is with respect to network topology, system structure, and the maximal compromised agent subset. We further provide an equivalent statement, which connects to 2s-sparse observability in the centralized framework in certain scenarios, such that the sufficient condition is feasible. Numerical simulations are finally provided to illustrate the developed results.
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| 5. |
- Jin, Ming, et al.
(författare)
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Power Grid AC-Based State Estimation : Vulnerability Analysis Against Cyber Attacks
- 2019
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Ingår i: IEEE Transactions on Automatic Control. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9286 .- 1558-2523. ; 64:5, s. 1784-1799
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Milosevic, Jezdimir, et al.
(författare)
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A Security Index for Actuators Based on Perfect Undetectability : Properties and Approximation
- 2019
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Ingår i: 2018 56th Annual Allerton Conference on Communication, Control, and Computing, Allerton 2018. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538665961 ; , s. 235-241
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 7. |
- Pare, Philip E., et al.
(författare)
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Multi-Layer Disease Spread Model with a Water Distribution Network
- 2019
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Ingår i: Proceedings of the IEEE Conference on Decision and Control. - : Institute of Electrical and Electronics Engineers Inc.. - 9781728113982 ; , s. 8335-8340
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a layered networked SIWS (Susceptible-Infected-Water-Susceptible) model, for an SIS-type waterborne disease spreading over a human contact network connected to a water distribution network that has a pathogen spreading in it. Conditions for local and global stability of the healthy state, where no one is sick and the water network is not contaminated, are provided. We also pose an observability problem, and show under certain conditions if you observe some of the human contact network you can recover the pathogen levels in the water network.
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| 8. |
- Pare, Philip E., et al.
(författare)
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Networked Model for Cooperative Adaptive Cruise Control
- 2019
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Ingår i: IFAC PAPERSONLINE. - : ELSEVIER. - 2405-8963. ; , s. 151-156
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a cooperative adaptive cruise control model, adding a communication network structure to an existing model that has been shown to capture real commercial adaptive cruise control vehicle behavior. The proposed model is interesting because it only requires minimal information sharing, facilitating the creation of platoons comprised of vehicles from different manufacturers. We prove the stability of the model and discuss string stability. Algorithms for estimating the velocity of the vehicles locally and for estimating the velocities of all the vehicles in the platoon are presented. We simulate vehicle platoon control with the lead vehicle following an experimentally collected trajectory, showing that adding communication can cause a string unstable platoon to become stable.
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| 9. |
- Pirani, Mohammad, et al.
(författare)
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A game-theoretic framework for security-aware sensor placement problem in networked control systems
- 2019
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Ingår i: Proceedings of the American Control Conference. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538679265 ; , s. 114-119
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 10. |
- Pirani, Mohammad, et al.
(författare)
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A Graph-Theoretic Approach to the H ∞ Performance of Leader-Follower Consensus on Directed Networks
- 2019
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Ingår i: IEEE Control Systems Letters. - : IEEE. - 2475-1456. ; 3:4, s. 954-959
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Tidskriftsartikel (refereegranskat)abstract
- We study a graph-theoretic approach to the H∞ performance of leader following consensus dynamics in the presence of external disturbances when the underlying graph is a directed network. We first provide graph-theoretic necessary and sufficient conditions for the consensus dynamics to have the system H∞ norm from external disturbances to the state of each agent to be lower than a certain value. Moreover, we discuss the tightness of the proposed conditions via examples. Then, we study the relation between the system H∞ norm for directed and undirected networks for specific classes of graphs, i.e., balanced digraphs and directed trees. Moreover, we investigate the effects of adding directed edges to a directed tree on the resulting system H∞ norm.
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