Formation Control For Multi-UAVs System With Communication Constraint

Nowadays,technology about unmanned aerial vehicles has been applied to many fields such as business,scientific research and military.The formation control of unmanned aerial vehicles system has also become a hot topic.During the observation of biological systems,scientists discovered that many formation movements do better than the individual movements.For example,the formation of geese formed a herringbone echelon to reduce the resistance,and the formation of fish improved the efficiency of swimming and predation.The formation movement of the UAV system is a coordinated movement with a large number of UAVs composed of a specific geometry.The formation movement of the UAV system has higher efficiency,stronger stability and robustness than the single individual movement,and it does better in performing high-intensity tasks such as disaster monitoring,searching and rescuing.Formation control is a control technique that maintains the relative distance between the UAVs,but the existing level of technology cannot support the multi-UAV formation control in the full sense.Therefore,more researches on information sensing technology,data fusion technology,task distribution technology,track planning technology,formation control technology,communication networking technology,virtual / physical verification experimental platform technology,as well as a number of inter-technology collaborative research are very significant for China to achieve the United States Air Force’s 2016-2036 small drone development plan,such as "bee colony","grouping","loyalty machine" and other multi-UAV cooperative formation.As an important characteristic of multi-UAVs system,communication constraint is the hot spot in the past ten years.Due to the complexity of the real multi-UAVs system,many uncontrollable faults are occured on the system.The scale and damage are still increasing,which destroy the synchronization of multi-UAVs system.It is critical to find more effective measures to prevent and control malfunctions which ensure the system stability.Therefore,we must fully consider the actual situation,contact characteristics of multi-UAVs system,establish a reasonable dynamic model,and apply different fault tolerant control strategies to achieve synchronization of multi-UAVs system for different communication constraint.This is of great significance to the practical application of multi-UAVs system.The main contents of this paper are as follows:Firstly,when multi unmanned aerial vehicles work with formation,individual information needs to be exchanged between each other.During this process,the interactive information between the individuals may occur transmission time-delay because of communication bandwidth,the amount of data and other restrictions.In this paper,the design problem of formation control of multi-UAVs is considered in the case of transmission time-delay.The Lyapunov-Krasovskii function is established by using the random variables of Bernoulli distribution to describe the transmission time-delay.The random analysis and Lyapunov stability theory are used to derive the delay-dependent stability conditions of UAV formation control.Secondly,the multi-UAVs formation controller design problem is considered under the premise of multi-UAVs limited bandwidth.Event-triggered mechanism based on composite error information is used to reduce the amount of information which is needed to be transported and reduce the bandwidth.The Lyapunov function is established.The event-triggered mechanism and Lyapunov stability theory are used to derive the stability conditions of UAV formation control.Thirdly,for the difficulty of linear velocity measurements of the multi-UAVs system,the design problem of formation control of multi-UAVs is considered without velocity measurement.transmission time-delay.More precisely,we consider the force as a virtual control input for the translational dynamics,from which we extract the required system attitude and thrust achieving the tracking objective.Thereafter,the control torque is designed to drive the actual attitude to the desired one.A nonlinear observer,as well as some instrumental auxiliary variables are used to obviate the need for the linear velocity.Then,considering random time-delay and achieve formation control for multi-UAVs system without velocity measurement.