On Redundant Observability: From Security Index to Attack Detection and Resilient State Estimation

TL;DR

This paper introduces redundant observability as a unifying concept for control system security, proposing an efficient estimator design that enhances attack detection and resilience by leveraging redundancy and Kalman decomposition.

Contribution

It presents a novel framework linking security notions with redundant observability and develops an efficient estimator design for resilient control system operation under attacks.

Findings

Redundant observability unifies security notions like security index and attack detectability.

The proposed estimator improves resilience and computational efficiency.

The scheme effectively detects and mitigates sensor attacks in control systems.

Abstract

The security of control systems under sensor attacks is investigated. Redundant observability is introduced, explaining existing security notions including the security index, attack detectability, and observability under attacks. Equivalent conditions between redundant observability and existing notions are presented. Based on a bank of partial observers utilizing Kalman decomposition and a decoder exploiting redundancy, an estimator design algorithm is proposed enhancing the resilience of control systems. This scheme substantially improves computational efficiency utilizing far less memory.