Research On Fault Diagnosis Of UAV Formation Flight Control Systems Based On Transient Performance

Flight control system(FCS)is the core of unmanned aerial vehicle(UAV),and its reliability is related to the safety of UAV.The timely and effective fault diagnosis of FCS is the basis to ensure the safe flight of UAV.Therefore,the research on fault diagnosis of UAV flight control system has important research significance and application value.Moreover,since multi-UAV formation flight is a highly sophisticated and highly-invested activity,the fault diagnosis technology of UAV formation needs more rapidity,accuracy and good robustness besides the stability(usually the Lyapunov sense).This makes a request for the transient performance of the UAV formation fault diagnosis.In this paper,the UAV formation FCS is taken as the research object.Considering the actuator failure,the fault diagnosis method based on transient performance is studied.Firstly,this paper introduces the background and significance of the project,the research status of UAV formation FCS,fault diagnosis technology as well as the control methods based on transient performance.The model of UAV flight control system,the main types of communication topological structure of UAV formation FCS and the required graph theory knowledge are introduced in this paper.Secondly,a finite time bounded robust observer is designed for the Leader-follower UAV Formation FCS with time-varying disturbances to complete the fault diagnosis.Firstly,the connection diagram of Leader-Follower UAV formation FCS is constructed and shown with a directed graph.The state equation and output equation of each UAV are established,then the state vectors and fault vectors are expanded into new vectors.A global error equation based on digraphs is established,and based on the finite-time bounded robust control,a finite-time robust fault diagnosis observer is constructed to achieve fault diagnosis with effectively,accurately and good transient performance,for the failure of any UAV in the UAV formation or the simultaneous failure of several UAV.The finite-time-bounded robust observer designed in this chapter can guarantee the boundedness of fault diagnosis.Thirdly,for the UAV flight control system with actuator failure,a connection diagram of Leader-Follower UAV formation flight control system is constructed and shown with undirected graph.The global dynamic equation of the UAV Formation FCS is established based on the obtained Leader-follower undirected graph.Then,an adaptive sliding mode observer is established,the residual signal of the observer is composed of the relative output of the observer and the UAV formation for each follower UAV.When the global error equation is established and the Lyapunov function is constructed,it is proved that the error convergence time can be adjusted by adjusting the set parameters and that the state of the error system can converge to a minimum range in a certain time.The transient performance of fault diagnosis is ensured both in terms of boundedness and rapidity.Finally,the method in this chapter can further optimize the transient performance from the bounded and rapid research,and the convergence time of the system can be set in advance.Different from the traditional observer based multi-agent system fault diagnosis method which constructs the observer in each agent,in this chapter,by designing observers in one or two UAVs,the fault diagnosis of the entire UAV formation can be achieved,this can greatly reduce the cost of observer construction and maintenance.Specifically,a UAV is selected arbitrarily in the formation of a UAV and its global dynamic equation is reconstructed.At this time,the system output is composed of the local dynamic information available to the selected UAV.Then,Based on the finite-time theory,an unknown input observer(UIO)can be constructed which converges in the preset time and keeps the state bounded in the process of convergence.According to the state estimation value obtained from the preset-time UIO and a fault diagnosis law,the fault diagnosis of neighbor UAVs can be completed in a preset finite time.