Date of Award

Summer 2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical and Computer Engineering

Committee Director

W. Steven Gray

Committee Member

Luis A. Duffaut Espinosa

Committee Member

Oscar R. González

Abstract

Critical infrastructure requires a safe and secure operating environment because of its significant impact on society. Its large-scale size and distributed sensors and actuators make it vulnerable to cyber-physical attacks. A zero dynamics attack is a type of cyber-physical attack where an adversary keeps the output of the target constant (classically zero), while forcing some of the internal states to deviate from their nominal values. Most of the existing work in the literature assumes the system dynamics are linear and available to an adversary. The first goal of this dissertation is to show that an adversary can successfully execute a malicious zero dynamics attack on an unknown bilinear system. The main motivation is to understand the nature of the vulnerability so that appropriate defensive measures can be taken. The second goal is to develop an algorithm for attack detection so that the system can be secured against such attacks. To demonstrate the methodology, a bilinear model of a petro-chemical plant was chosen. Two types of zero dynamics attacks are considered, an observer-based approach and an analytical approach. Both approaches are simulated numerically and found to be effective. Then an observer-based attack detection method is developed. The proposed state observer for a bilinear system is designed using Lyapunov theory and convex optimization concepts. The observer monitors all the unmeasurable states so that any deviation in any state from it’s nominal value can be immediately detected in the event of an attack. The designed observer is implemented for the petro-chemical plant and found to be effective in detecting the onset of zero dynamics attacks.

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DOI

10.25777/w7rg-e216

ISBN

9798384456124

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