| Unmanned Aerial Vehicles are relatively versatile,persistent,with low injuries and maneuverability and have been widely used in expanding areas such as military,civil and commercial fields.However,an quadrotor UAV system is an inherently unstable,under-actuated,multi-variable,and strongly coupled nonlinear system beyond the difficulties of the control systems design.There is also a demand of reliability and safety to maintain stability and an acceptable system performance in the presence of actuator faults,which may lead to the crash of the UAV and increase financial burden.The fault tolerant flight control aims to increase the survivability of a failed aircraft by reconfiguring the control laws.In this paper,based on active disturbance rejection control,flight control systems are designed to ensure flight performances when there actuator faults are absent,while fault tolerant flight control is designed to accommodate actuator faults to ensure UAV safety with delicate performance degradation.The main research contents and innovative achievements are as follows:(1)The structural arrangement and flight principle of the quadrotor UAVs are analyzed,based on Newton-Eulerian method,the kinematics equations and dynamic equations of the quadrotor UAV and the mathematical model of the actuator damage faults are established.This will be the basis of the design of flight control.(2)Aiming at the problem that the quadrotor UAV system is under-driven and susceptible to external interference,the flight control method is designed to realize the digital simulation of the control algorithm based on the active disturbance rejection control.The simulation results show that the active disturbance rejection controller has strong resistance to external disturbances,and it can make the quadrotor UAV respond quickly without wind disturbance and wind disturbance.The attitude control is stable and meets the requirements of high fixed point.(3)Aiming at the problems of many parameters in the active disturbance rejection controller and the difficulty of setting,the fuzzy active disturbance rejection controller is used as the reference controller.On this basis,the time delay control technology is used and a passive fault-tolerant control method is proposed.The simulation results show that under the condition of no fault of the actuator,there is a short-term oscillation in the response process,and the attitude angle and height tend to be steady-state values within 6 seconds.Under the condition of damage fault of the actuator,the fault is treated as an unknown dynamical part to approximate and compensate the possible fault of the actuator,the fault-tolerant adjustment time of attitude angle and height is no more than 2 seconds,and the maximum deviation is no more than 1.5° and 0.35 meters respectively,which meets the requirements of fault-tolerant control rapidity and stability.(4)Aiming at the problem that the passive fault-tolerant control method can not guarantee the stability of the system in the unknown fault and does not have the initial recovery,based on the extended state observer theory and adaptive control technology,a nonlinear adaptive fault diagnosis of the quadrotor UAV is proposed.Simulation results show that: when there is no fault,the attitude angle and height are fast and stable within 5 seconds,and the overshoot is small;when the motor 1 has 30% damage fault,the designed The active fault-tolerant control method can make the error of the estimated value of the fault and the given value tend to zero after about 20 seconds,and the maximum error does not exceed 10% during the fault adjustment process;when the motor 1 and the motor 2 are damaged by 30%,about 10 seconds later The error between the estimated value of the fault and the given value tends to zero,and the maximum error in the fault adjustment process does not exceed 7.5%,which satisfies the requirements of the rapidity and stability of fault-tolerant control. |
