Observer-Based Event-Triggered Sliding Mode Control for Secure Formation Tracking of Multi-UAV Systems

This article is concerned with the problem of the secure formation tracking of multiple unmanned aerial vehicles (UAVs) subject to replay attacks, where an observer-based event-triggered sliding mode control approach is adopted. First, a novel attack model is established for multi-UAV systems considering replay attacks, in which the issue of the replay attack beginning and ending within a sampling period is solved. Then, a switched event-triggered scheme is developed for multi-UAV systems subject to replay attacks, under which the corresponding communication mechanisms are invoked for different attack states. This communication scheme brings lower data releasing rate and less energy consumption based on the severity level of replay attacks while the desired tracking performance is ensured. On the basis of the sliding mode control theory, observer-based event-triggered formation tracking strategies are developed for multi-UAV systems with nonlinearities under replay attacks by combining the interactive information from neighbors. Sufficient conditions of the multi-UAV system to achieve the desired formation are obtained by utilizing Lyapunov stability approach. Finally, a simulation example with multiple UAVs is performed to demonstrate the validity of the developed formation control strategy.