| 1. |
- Wiese, Moritz, et al.
(författare)
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Secure Estimation for Unstable Systems
- 2016
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Ingår i: 2016 IEEE 55th Conference on Decision and Control, CDC 2016. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509018376 ; , s. 5059-5064
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Konferensbidrag (refereegranskat)abstract
- We assume that the states of an unstable dynamical system are encoded and sent to an estimator through an uncertain channel, which is a channel disturbing its inputs in a nonstochastic manner. The encoder's codeword is also fed into another uncertain channel, at whose output an eavesdropper is listening. The estimator should obtain a uniformly bounded system state estimation error, whereas the eavesdropper's information about the system states should be subject to a security constraint. We find a condition on the relation between the uncertain channel from encoder to estimator and the uncertain channel from encoder to eavesdropper which if satisfied allows for at least one of the two following security criteria to hold: The volume of the set of states possible acccording to the eavesdropper's information tends to infinity at exponential speed-by itself (strong security) or if divided by the volume of the set of states possible according to the estimator's information (weak security).
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| 2. |
- Ahlen, Anders, et al.
(författare)
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Toward Wireless Control in Industrial Process Automation : A Case Study at a Paper Mill
- 2019
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Ingår i: IEEE Control Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 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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| 3. |
- Chen, J., et al.
(författare)
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Protecting Positive and Second-Order Systems against Undetectable Attacks
- 2017
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Ingår i: IFAC-PapersOnLine. - : Elsevier. - 2405-8963. ; 50:1, s. 8373-8378
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Tidskriftsartikel (refereegranskat)abstract
- Undetectable attacks in security studies of cyber-physical systems render the measurements of the system equal to a possible physical response. In this paper, we investigate defense strategies against the undetectable single-attack for positive systems and second-order systems, which both can be reinterpreted in terms of graphs with nodes and edges, while the undetectable attack is added through one of the nodes. We show that an arbitrary placement of a sensor prevents undetectable single-attack for these classes of systems. It is worth emphasising that we do not need to measure at the corrupted node to prevent the undetectable single-attack, but can measure at any node. The defense strategy is of a low complexity and can be readily implemented.
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| 4. |
- D'Innocenzo, A., et al.
(författare)
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Scalable scheduling algorithms for wireless networked control systems
- 2009
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Ingår i: 2009 IEEE INTERNATIONAL CONFERENCE ON AUTOMATION SCIENCE AND ENGINEERING. - : IEEE. - 9781424445783 ; , s. 409-414
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Konferensbidrag (refereegranskat)abstract
- In this paper, we address the problem of designing scalable scheduling and routing policies over a time-triggered multi-hop control network, when closing a considerable number of control loops on the same network. The key idea is to formally define by means of regular languages the set of schedules for each control loop that satisfy a given control specification, and to exploit operators on regular languages to compute the set of schedules for the whole system. In order to test our methodology, we address a mineral floatation control problem derived from the Boliden (a swedish mining company) mine in Garpenberg, and propose a scheduling solution that can be implemented on systems compliant with communication protocols for wireless networks (e.g. the WirelessHART specification).
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| 5. |
- Ishizakiy, T., et al.
(författare)
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Singular perturbation approximation of semistable linear systems
- 2013
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Ingår i: 2013 European Control Conference, ECC 2013. - : IEEE. - 9783033039629 ; , s. 4508-4513
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a singular perturbation approximation for semistable linear systems. In particular, we derive a novel expression of error systems in the Laplace domain. As a result, we obtain an h2-error bound in terms of the sum of eigenvalues of an index matrix, which coincides with a controllability gramian of the state-derivative. Furthermore, we show that the singular perturbation model appropriately preserves the semistability of the original system and also guarantees the stability of the error system. The efficiency of the proposed method is shown through a numerical example of a Markov chain model approximation.
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| 6. |
- Johansson, Alexander, et al.
(författare)
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Optimization of the H∞-norm of Dynamic Flow Networks
- 2018
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Ingår i: 2018 Annual American Control Conference (ACC). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 1280-1285
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Konferensbidrag (refereegranskat)abstract
- In this paper, we study the H∞-norm of linear systems over graphs, which is used to model distribution networks. In particular, we aim to minimize the H∞-norm subject to allocation of the weights on the edges. The optimization problem is formulated with LMI (Linear-Matrix-Inequality) constraints. For distribution networks with one port, i.e., SISO systems, we show that the H∞-norm coincides with the effective resistance between the nodes in the port. Moreover, we derive an upper bound of the H∞-norm, which is in terms of the algebraic connectivity of the graph on which the distribution network is defined.
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| 7. |
- Sadamoto, T., et al.
(författare)
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Weak resilience of networked control systems
- 2017
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Ingår i: 2016 European Control Conference, ECC 2016. - : IEEE. - 9781509025916 ; , s. 977-982
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a method to establish a networked control system that maintains its stability in the presence of certain undesirable incidents on local controllers. We call such networked control systems weakly resilient. We first derive a necessary and sufficient condition for the weak resilience of networked systems. Networked systems do not generally satisfy this condition. Therefore, we provide a method for designing a compensator which ensures the weak resilience of the compensated system. Finally, we illustrate the efficiency of the proposed method by a power system example based on the IEEE 14-bus test system.
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| 8. |
- Wei, Jieqiang, et al.
(författare)
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Asymptotic and finite-time almost global attitude tracking : Representations free approach
- 2018
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Ingår i: 2018 European Control Conference, ECC 2018. - : Institute of Electrical and Electronics Engineers (IEEE). - 9783952426982 ; , s. 3126-3131
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Konferensbidrag (refereegranskat)abstract
- In this paper, the attitude tracking problem is considered using the rotation matrices. Due to the inherent topological restriction, it is impossible to achieve global attractivity with any continuous attitude control system on SO(3). Hence in this work, we propose some control protocols achieving almost global tracking asymptotically and in finite time, respectively. In these protocols, no world frame is needed and only relative state information are requested. For finitetime tracking case, Filippov solutions and non-smooth analysis techniques are adopted to handle the discontinuities. Simulation examples are provided to verify the performances of the control protocols designed in this paper.
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| 9. |
- Wei, J., et al.
(författare)
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Finite-time consensus protocols for multi-dimensional multi-agent systems
- 2020
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Ingår i: Control Theory and Technology. - : South China University of Technology. - 2095-6983 .- 2198-0942. ; 18:4, s. 419-430
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Tidskriftsartikel (refereegranskat)abstract
- A finite-time consensus protocol is proposed for multi-dimensional multi-agent systems, using direction-preserving signum controls. Filippov solutions and nonsmooth analysis techniques are adopted to handle discontinuities. Sufficient and necessary conditions are provided to guarantee infinite-time convergence and boundedness of the solutions. It turns out that the number of agents which have continuous control law plays an essential role in finite-time convergence. In addition, it is shown that the unit balls introduced by ℓp norms, where p∈ [1 , ∞] , are invariant for the closed loop.
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| 10. |
- Johansson, Anders J, et al.
(författare)
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Random Number Generation by Chaotic Double Scroll Oscillator on Chip
- 1999
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Ingår i: Proceedings of the 1999 IEEE International Symposium on Circuits and Systems, ISCAS '99.. - 0780354710 ; 5, s. 407-409
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Konferensbidrag (refereegranskat)abstract
- Generation of good non-repeatable and non-predictable random number sequences is of increasing importance, both in security applications and in simulations. A novel, compact system is presented in which a secure random number is generated by sampling a chaotic system and using this bitstream as the input to a pseudo-random generator. An optional hash function can be used on the seed in order to decrease the correlation. As all of the components can be implemented in a mixed-mode CMOS process, a totally self-contained non-repeatable random-number generator can be fabricated. This increases the security of the system, as very few of the systems parameters is observable from the outside. It also makes it possible to easily have available good random numbers in simulations if the chip is incorporated as a subsystem in an ordinary computer.
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