The Event-trggered Encirclement And Circumnavigation Control Of Multiple UAVs

The coordinated encirclement and circumnavigation of multiple UAVs has attractive considerable attentions because of its huge potential military and commercial application value in fields such as in coordinated monitoring and attack,target expelling,action limitation,artistic performance and so on.In order to reduce the dependence of multi-UAV coordination on sensors and communication as much as possible,this dissertation explores the problem of multi-UAV's bearing-based coordinated encirclement and circumnavigation for a specific target under the event-triggered framework.At the same time,based on the Gazebo simulator,a simulation platform for multi-UAVs is constructed,in which the effectiveness of the proposed control algorithms is verified.The main work and innovations of this dissertation are summarized as follows:(1)Proposing a bearing-only coordinated encirclement and circumnavigation control scheme for the static target.Firstly,the problem of encirclement and circumnavigation for a static target is modeled in mathematics.Then,with the aid of the bearing rigidity theory,the problem of coordinated encirclement and circumnavigation control is transferred into a problem of target formation achievement.In addition,a bearing-only coordinated encirclement and circumnavigation control algorithm is designed elaborately based on the formation achievement problem.Besides,the system's stability under proposed algorithm is proved in triple levels,which are bearing constraints,formation center and formation scale respectively.(2)Proposing a bearing-based coordinated encirclement and circumnavigation control scheme for the moving target based on the networked UAVs' coordinated estimation algorithm for the velocity of the target as well as the distance towards the target.Utilizing the inertial Measurement Unit(IMU)equipped on UAVs,this dissertation proposes an estimation algorithm for the target's velocity and UAV-target distance based on the velocity and bearing information of the local UAV network.Afterwards,the topology condition for the estimableness of the target's velocity is provided and proved mathematically.On the basis of the proposed estimation algorithm,the previously proposed encirclement and circumnavigation algorithm for the static target is expanded to track a moving target in a coordinated encirclement method.After that,the stability of the proposed algorithm is proved by using the Lyapunov stability theory and the cyclic input-to-state stability(ISS)theory.(3)Proposing a coordinated encirclement and circumnavigation control algorithm based on the event-trigger mechanism.In order to relieve the communication burden of the system,this dissertation introduces the event-trigger mechanism into the problem of coordinated encirclement and circumnavigation control.Firstly,the event as well as its trigger condition is reasonably defined for the problem of the encirclement and circumnavigation control.Based on that,a coordinated encirclement and circumnavigation control algorithm based on the event-trigger mechanism is proposed.This algorithm can reduce the communications between UAVs greatly,whileas the performance is only reduced more or lees.Meanwhile,it is proved theoretically further that the interval time between two triggered events is always larger than a strictly positive constant,which means that the unexpected Zeno phenomenon will not occured for the proposed algorithm.(4)Constructing a distributed multi-UAVs simulation environment based on Gazebo platform and Robot Operation System(ROS)framework as well as verifying the proposed control laws in this simulation environment.Gazebo platform is a widely used simulators in the field of robot research.In this dissertation,the Gazebo platform is combined with ROS framework and a distributed simulation environment connected by the internet of UDP protocol and of good expandability and practicability is then constructed.At last,the proposed control algorithms are verified and analyzed carefully based on this simulation environment.