Model based fallback control for networked control system via switched Lyapunov function

This paper aims to propose a fallback system isolated from man-in-the-middle attack (MITM) for networked control systems. In this paper, fallback is an incident response of the control system in which facilities are preferentially protected and a minimal system operates during MITM. Since the communication contents of the networked control systems can be tampered with by MITM, the proposed system named a "fallback system" is installed in a control target side, and the fallback system detects MITM without the communication contents. This system detects MITM based on the bilinear observer and switched Lyapunov function. When MITM is detected, normal operation is switched to fallback operation automatically. As a first step of this study, a selector and a fallback unit of the fallback system are developed. A practical experiment simulating a simple defective discriminator is shown.