A Novel Defense Strategy Against Zero-Dynamics Attacks in Multi-Agent Systems

This paper studies strategic topology switching for a second-order multi-agent system under zero-dynamics attack (ZDA) whose attack-starting time is allowed to be not the initial time. We first study the detectability of ZDA, which is a sufficient and necessary condition of switching topologies in detecting the attack. Based on the detectability, a Luenberger observer under switching topology is proposed to detect the stealthy attack. The primary advantages of the attack-detection algorithm are twofold: (i) in detecting ZDA, the algorithm allows the defender (system operator) to have no knowledge of the attack-starting time and the misbehaving agents (agents under attack); (ii) in tracking system in the absence of attacks, Luenberger observer has no constraint on the magnitude of observer gains and the number of observed outputs. Numerical simulations verify the effectiveness of the strategic topology-switching algorithm.