Research And Implementation Of Distributed Formation Control For Multiple UAVs Based On Consensus Theory

With the development of science and technology,unmanned aerial vehicles(UAVs)have been playing an increasingly important role in various fields.The formation of multiple UAVs can make full use of the limited capability of each UAV to complete the large and complex missions,such as large-scale surveillance and reconnaissance,coordinated encirclement,etc.Hence multi-UAV formation has become the current frontier research field.This thesis takes quadrotor UAV as the research object and researches the formation control problem of multiple UAVs based on consensus theory.The main contents are as follows.Firstly,considering the situation that multiple UAVs need to adjust their formation in real-time according to mission requirements in a complex dynamic environment,and the communication link between UAVs is limited,the time-varying formation control problem with directed communication topology of the multi-UAV system modeled by the second-order integrator is studied.Based on the consensus theory,a distributed formation control protocol is designed.And the time-varying formation control problem is transformed into the stability problem of the closed-loop system.The sufficient conditions for the stability of the multi-UAV systems and the parameters’ calculation method of the distributed formation control protocol are given in the form of linear matrix inequality.The stability of the multi-UAV systems is proved by constructing the Lyapunov candidate function.Considering the problem of obstacle avoidance during the formation process,a collision avoidance term based on the potential field function is added to the distributed formation control protocol.Secondly,considering that in actual missions,the multi-UAV systems not only need to form and maintain a predefined time-varying formation,but also needs to track the leader UAV or predefined trajectories.And in the communication link of physical systems,there are inevitable communication delays,which affect the stability and performance of the multi-UAV formation.Therefore,the time-varying formation tracking problem for multi-UAV systems with directed communication topology and communication delays is studied.Based on the consensus theory,a distributed formation tracking control protocol with communication delays is designed,and the time-varying formation tracking problem is transformed into a closed-loop time-delayed system stability problem for analysis.The sufficient conditions for the multi-UAV systems to realize the time-varying formation tracking are given in the form of linear matrix inequality.The stability of the system is proved by constructing the Lyapunov-Krasovskii function.And finally,the designed formation tracking control protocol is implemented to the target encirclement application.The encirclement of a dynamic target is realized based on a multi-UAV experimental platform.Finally,a distributed multi-UAV simulation platform based on the Gazebo simulator is constructed.The proposed simulation platform has good scalability and fidelity.A distributed multi-UAV experimental platform based on quadrotors is constructed as well.The communication network between UAVs in the multi-UAV experimental platform is realized based on Message Queuing Telemetry Transport(MQTT)protocol and wireless local area network,which can easily implement the directed communication topology considered in the thesis.The experimental platform supports the implementation of the proposed control protocol to each quadrotor to realize a distributed control architecture.The proposed control protocols are verified and analyzed comprehensively based on the aforementioned simulation and experimental platform.