Research On Fault-tolerant Control Technology For UAV Based On Backstepping

The design concept of UAV originated from a British military top secret plan of "AT Program" in1914.As a kind of UAV with "unmanned aerial vehicle,manned system" instead of human beings to perform complex,arduous and dangerous tasks,it plays an important role in many fields.However,due to the extremely complex flying environment and the characteristics of the airframe itself,the system will inevitably have internal faults during the flight and execution of the UAV mission,which will lead to more serious accidents.Therefore,in order to ensure the safety and reliability of UAV as much as possible,the research topic of UAV fault diagnosis and fault-tolerant control has become particularly important and meaningful.In this paper,a fault-tolerant control algorithm for UAV flight control system with actuator faults is designed based on backstepping control method.At the same time,the practical engineering application value of the proposed method is tested on the Quanser UAV verification platform.This research is mainly divided into the following parts:Firstly,the research background and significance of this topic are briefly introduced,and the research status of fault-tolerant control technology of UAV flight control system is summarized.Then the force and moment of a UAV are analyzed,and a non-linear mathematical model is established.Secondly,considering the uncertainties of modeling,external disturbances and actuator failure of UAV flight control system,based on reasonable assumptions,the fault is diagnosed by using adaptive sliding mode observer.Based on the backstepping control algorithm,the active fault-tolerant control design of sliding mode dynamic surface is proposed,and the attitude tracking controller is reconstructed to ensure the stability of attitude control system.The system can track instructions asymptotically in case of actuator failure.The stability of the system is proved by Lyapunov theory to ensure that the trajectory tracking error is eventually uniformly bounded.Finally,the effectiveness of the proposed fault-tolerant control law is verified by a simulation example in MATLAB.Thirdly,considering more complex and difficult actuator failures,an adaptive backstepping fault-tolerant flight controller design is proposed for actuator failures which may concurrently occur without fault detection and diagnosis module.A new actuator multi-fault mathematical model is proposed,and each type of actuator fault is described.An improved tracking fault-tolerant controller is designed based on backstepping control algorithm and the bounded theorem.The Lyapunov function proves that the control scheme can guarantee the global boundedness of all closed-loop signals and converge the tracking error index to the adjustable residual range.Finally,the validity ofthe method is verified by simulation with MATLAB.Finally,in order to test the engineering application effect of the algorithm proposed in this paper,the verification experiment is carried out on the semi-physical verification platform of Quanser unmanned tool.A non-linear mathematical model is established for the attitude system of Qball-x4 UAV,and then the Qball-X4 Quad-rotor UAV body is calibrated.Under Simulink/QUARC environment,the attitude tracking fault-tolerant controller proposed in Chapter IV is built.The motor is allocated,and the gain is adjusted for attitude tracking flight..In the case of no fault,single actuator fault and two actuators fault,the stability of UAV attitude system and the validity of the self-adaptive inversion fault-tolerant controller designed are verified respectively which also shows that the algorithm in this paper has certain application value in engineering.