Abstract
Networked control systems have advantages such as flexibility, efficiency, but at the same time they are exposed to cyberattacks. Among many lethal attacks, the zero-dynamics attack is a model based attack and it is very hard to detect. In this paper, a new strategy for intrusion detection and defense against zero-dynamics attack is proposed, and it is based on the generalized sampler that takes a weighted average of multiple samples obtained during one sampling interval. By using the generalized sampler instead of the simple sampler, the zeros of the sampled-data system can be placed at arbitrary locations, and if all zeros are placed inside the unit circle, the attack signal becomes no longer effective. This strategy still works even if all the information is exposed to hackers and it is considerably insensitive to the shift of intrinsic zeros. A design procedure for the generalized sampler is provided under mild assumptions. Furthermore, optimal designs for the selection of desired zeros are formulated considering practical issues. Theoretical findings are validated through numerical simulations.
Highlights
A DVANCED communication technologies make it possible to control remote dynamic systems, monitor the status of geographically distributed systems such as power systems and smart factories, and make decisions for multiagent systems
We focus on the zerodynamics attack (ZDA) in this paper
In the case that the hacker assumes that zero-order hold (ZOH) and simple sampler (SS) are used and a ZDA is constructed using this information, the zero-dynamics will be quite different from the real one, it will be detected by the new signals from generalized sampler (GS)
Summary
A DVANCED communication technologies make it possible to control remote dynamic systems, monitor the status of geographically distributed systems such as power systems and smart factories, and make decisions for multiagent systems. [16] proposed a dual-rate control; construct a lifted discrete-time system by collecting a sufficient number of output measurements during a single sampling interval. It is shown that the lifted system has no unstable zeros except 1 This approach can be used to detect the intrusion of ZDA, a collection of output measurements should be transmitted, which requires fairly large communication load. We propose several metrics for the design considering practical issues such as output deviation of the newly generated signal from the original sampled output and the effect of noise. With these metrics, we present optimal designs that can be solved by using well known numerical tools for convex optimization. In is the n × n identity matrix and 0n denotes the n × 1 zero vector
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