Research On Fault Diagnosis And Fault-Tolerant Control Of Quadrotor UAV

Quadrotor unmanned aerial vehicle(QUAV)has many advantages such as vertical take-off and landing,small size,simple structure and so on,so it is more and more widely used compared with other UAV systems.With the in-depth study of the quadrotor UAV,the range of tasks it performs is greatly increased than in the past.Meanwhile,the continuous improvement of the performance of the UAV system makes the control system more complex.In the flight process of the quadrotor UAV,there will inevitably be a variety of faults,such as actuator fault,sensor fault,etc.In addition,it will be affected by disturbance.Therefore,in order to improve the reliability and safety of the quadrotor UAV,fault diagnosis and fault-tolerant control is very necessary.In this dissertation,the quadrotor UAV is taken as the research object,considering the UAV nonlinear term,time delay and the disturbance in the flight process,based on the observer method,the fault diagnosis and fault-tolerant control algorithm is studied.It mainly includes the following parts:(1)The attitude control system of a quadrotor UAV is modeled.Firstly,the flight principle of the quadrotor UAV is explained.Then the coordinate system is established and the coordinate transformation matrix is derived.Secondly,the dynamics equation of UAV attitude control system is established by Newton-Euler equation.Finally,the dynamic equation is transformed into state-space equation to prepare for the following research content.(2)The fault diagnosis method of a quadrotor UAV with disturbance is studied.Firstly,the system is augmented by considering actuator fault,sensor fault and external disturbance.Then,an intermediate observer is designed for the augmented system.The Lyapunov function is used to prove that the error system is uniformly and ultimately bounded.Finally,through the simulation of the QUAV system,the effectiveness of the method is verified.(3)The fault diagnosis method of the quadrotor UAV with time delay is studied.Firstly,an intermediate variable is introduced for the actuator fault system of the quadrotor UAV with time delay,and an intermediate observer is designed to obtain the estimated values of the system states and actuator fault.Secondly,considering the simultaneous faults of the actuator and sensor,unknown input disturbance and measurement noise disturbance are added to the model to augment the system.Then,two intermediate variables are introduced to the augmented system to design an intermediate observer.The Lyapunov-Krasovskii functional is used to prove that the estimation error system is uniformly and ultimately bounded.Simulation results verify the feasibility and effectiveness of the proposed fault estimation method.(4)The fault-tolerant control method for nonlinear system of quadrotor UAV is studied.Considering the simultaneous faults of the actuator and sensor and the presence of external disturbance,the fault diagnosis observer is designed.By using the estimated values of the system states,the actuator fault and external disturbance obtained by the observer,a state feedback fault-tolerant control algorithm based on intermediate observer is designed.The states of the closed loop system are proved to be uniformly and ultimately bounded by Lyapunov function.The effectiveness of the algorithm is demonstrated by comparing the system states before and after fault-tolerant.Finally,the work done in the whole dissertation is summarized,the innovation points of the dissertation are explained,and the direction of future work is pointed out.