Research On Fault Reconstruction And Fault Tolerant Control Of Multi-rotor Unmanned Aerial Vehicle System

In recent years,with the development of multi-rotor UAV control technology,UAVs have been widely used in various fields.However,UAVs are susceptible to actuator fault during flight and may cause unnecessary damage.Therefore,it is of great significance to study the multi-rotor UAV system with fault tolerance and improve the safety and reliability of UAV flight control.This paper mainly studies the fault reconstruction and fault-tolerant control technology of the six-rotor UAV,focusing on the following research work:(1)Taking the six-rotor UAV system as the research object and according to the structure and flight principle of the UAV,the mathematical model of six-rotor UAV is built combined with Newton’s second law and Newton’s Euler equation.According to several common fault modes of UAVs,models of stuck and loss-of-effectiveness fault are established respectively,and then mathematical models of the six-rotor UAV in the event of actuator faults are established.According to the modern control theory,the state space models of the six-rotor UAV system under the condition of motor stuck and loss-of-effectiveness fault are established.(2)Aiming at the problem of the stuck and loss-of-effectiveness fault of the actuator in six-rotor UAV,the fault reconstruction method of the six-rotor UAV is studied.For the situation that the state space model of the six-rotor UAV system does not satisfy the observer matching condition,the auxiliary output is constructed to enable the auxiliary output system to break the limitation of the matching condition.On the basis of constructing the auxiliary output,each type of fault is designed with an observer to achieve an online estimation of the actuator fault signal.(3)For the fault-tolerant control problem of the six-rotor UAV,the controller is layered to design the basic control law and the fault-tolerant control allocation law.In the design of the basic control law,the state feedback controller and composite controller combined with the state feedback and the adaptive sliding mode controller are designed for the six-rotor UAV model.So that the UAV is still able to fly stably under the influence of external disturbance.In the design of the fault-tolerant control allocation law,for stuck and loss-of-effectiveness fault of the actuator,the reconstruction information of the fault signal obtained by the observer in(2)and the control allocation method based on the pseudo-inverse are respectively designed to control the allocation matrix to reduce the adverse effects of faulty components on the UAV,so fault-tolerant flight control of the six-rotor UAV is achieved.(4)The active fault-tolerant method for(2)(3)needs to design the fault diagnosis module and it increases the difficulty of system design.So an adaptive sliding mode fault-tolerant control method without relying on fault diagnosis module is proposed.Establish a mathematical model that can comprehensively describe the types of failures of the UAV motor stuck and loss-of-effectiveness to reduce the complexity of different processing for different types of faults;An adaptive mechanism in the adaptive sliding mode controller is designed to achieve online estimating fault and disturbance information without additional design of the observer.So the difficulty of designing the entire fault-tolerant system is reduced without designing observer and considering the observer matching conditions.Finally the stable flight of the UAV system in the influence of actuator fault can be realized with fault tolerant control.