Interval Observers for Secure Estimation in Cyber-Physical Systems

Stealthy attacks on the sensors and actuators embedded in cyber-physical systems could hinder the safe operation of these systems if the state estimators monitoring them cannot detect such attacks in time. In this paper, we study stealthy attacks in the framework of interval observers. We consider two classes of attacks: when a malicious agent compromises the sensors and when it is able to alter the system's actuators. For each type of attack, we design a dedicated interval observer for the system's state and we construct bounds for the attack signal. We investigate the ability of such interval observer to provide accurate estimates when the system is under the attack. Numerical simulations for a lateral model of an aircraft illustrate the capabilities of the synthesized observers.

I. Introduction

Security vulnerabilities in Cyber-Physical Systems (CPS), i.e., systems that tightly integrate computing and communication resources to control physical processes, allow for new types of cyberattacks that can lead to disastrous physical damage. Some recent examples include the StuxNet malware [1] and the Maroochy Sewage Control Incident [2]. Smaller systems such as commercial drones [3] and military vehicles [4] were also targeted.