| 1. |
- Kim, Dohwan, et al.
(författare)
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Sampling Rate Optimization for IEEE 802.11 Wireless Control Systems
- 2019
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Ingår i: ICCPS '19. - New York, NY, USA : ASSOC COMPUTING MACHINERY. - 9781450362856 ; , s. 87-96
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Konferensbidrag (refereegranskat)abstract
- Design of wireless control systems has been extensively studied, which is one of the fundamental issues in cyber-physical systems. In this paper, we empirically investigate heterogeneous sampling rate assignment with a testbed when multiple physical systems are controlled through an IEEE 802.11 network. Among the critical design variables in wireless control systems, we focus on the sampling rates because they are always key control knobs regardless of network protocols. There has been little experimental research on heterogeneous sampling rate optimization for IEEE 802.11 wireless control systems, where the sampling rates of each control loop may have different values. We first formulate the co-design problem in an optimization framework with respect to the heterogeneous sampling rates by explicitly taking into account the relations of the sampling rates with the control cost, network energy consumption, and network delay. We further relax the problem as convex optimization, which is provably solved in polynomial time. Our empirical study ensures that the approximate solution is tightly close to the original optimum. To validate the proposed optimization framework, we build a disk-levitation tube testbed, which wirelessly controls the height of 20 disks at the same time. Our empirical study confirms that our optimization formulation is highly effective in practice.
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| 2. |
- Park, Gyunghoon, et al.
(författare)
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Stealthy Adversaries Against Uncertain Cyber-Physical Systems : Threat of Robust Zero-Dynamics Attack
- 2019
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Ingår i: IEEE Transactions on Automatic Control. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0018-9286 .- 1558-2523. ; 64:12, s. 4907-4919
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we address the problem of constructing a robust stealthy attack that compromises uncertain cyber-physical systems having unstable zeros. We first interpret the (non-robust) conventional zero-dynamics attack based on Byrnes-Isidori normal form, and then present a new robust zero-dynamics attack for uncertain plants. Different from the conventional strategy, our key idea is to isolate the real zero-dynamics from the plants input-output relation and to replace it with an auxiliary nominal zero-dynamics. As a result, this alternative attack does not require the exact model knowledge anymore. The price to pay for the robustness is to utilize the input and output signals of the system (i.e., disclosure resources). It is shown that a disturbance observer can be employed to realize the new attack philosophy when there is a lack of model knowledge. Simulation results with a hydro-turbine power system are presented to verify the attack performance and robustness.
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| 3. |
- Park, Gyunghoon, et al.
(författare)
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When Adversary Encounters Uncertain Cyber-physical Systems : Robust Zero-dynamics Attack with Disclosure Resources
- 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. 5085-5090
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Konferensbidrag (refereegranskat)abstract
- In this paper we address the problem of designing a robust stealthy attack for adversaries to compromise an uncertain cyber-physical system without being detected. We first re-interpret the zero-dynamics attack based on the normal form representation. Then, a new alternative zero dynamics attack is presented for uncertain systems. This alternative employs a disturbance observer and does not require exact system knowledge in order to remain stealthy. The proposed robust zero-dynamics attack needs a nominal model of the system and, in addition, utilizes the input and output signals of the system. The proposed attack illustrates how the adversary is able to use disclosure resources instead of exact model knowledge. A simulation result with a hydro-turbine power system is presented to verify the attack performance.
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