Memory Event-triggered Sliding Mode Control for UAV Formation Under Communication Delay and Wake Interferences

This paper studies the formation control for unmanned aerial vehicles (UAVs) under communication delay and wake disturbances, in which the inner-loop and outer-loop control strategy is adopted. Firstly, as for the dynamical models of follower UAVs, the wake interferences are considered and their influences are respectively estimated by using the sliding model disturbance observers (SMDOs). Secondly, since the outer-loop information in the UAVs exchanges via communication network, by adding an internal dynamic variable, an adaptive memory-based event-triggered mechanism (METM) is proposed to alleviate transmission burden with maintaining ideal control performance. Thirdly, by using the designed METM and an intermediate vector, a sliding mode controller is derived to accomplish the desired control target, which can compensate the communication delay in control input. Fourthly, as for the overall closed-loop system, a sufficient condition on asymptotical stability is established and a co-design method of checking the triggering parameters and controller gains is expressed in term of linear matrix inequalities (LMIs). Moreover, in order to tackle the wake interferences of the inner-loop, an adaptive attitude tracking controller is put forward to ensure the bounded stability of tracking errors by solving the reference signal. Finally, a simulated example is exploited to illustrate the validity of the proposed scheme.