Research On Adaptive Fault-Tolerance Control Of Quadrotor Unmanned Aerial Vehicle Systems

With the advantages of high maneuverability,agility,less susceptibility,vertical take-off and landing,hovering and low expenditure,quadrotor unmanned aerial vehicles(UAVs)have been vastly utilized in areas such as reconnoiter,patrol duty,fire detection,search and rescues.In addition,with the problems of under-actuation,inherent coupling,and strong nonlinearity,it has been vastly studied theoretically.This paper studies the controller design of a Quadrotor Unmanned Aerial Vehicles(UAV),where external airflow disturbances,internal parametric uncertainties and actuator failures are respectively considered on its trajectory tracking problems.The main contributions are as follows:First,the flight principle of Quadrotor UAVs is detailed,in order to avoid Euler singularities,a model based on Unit-quaternions is introduced.Considering the under-actuated characteristic of the system,a virtual control input is introduced to enable the Quadrotor UAV to track a desired trajectory,and the control thrust input and the desired attitude can be extracted,the control torque input is designed to stabilize the desired attitude.Consider the fickleness of external airflow,disturbance observers are designed to estimate the slow time-varying disturbances,where the estimate errors are proven of exponential convergence.Based on the estimation value of the disturbance observer,a sliding mode control scheme is proposed,and the control thrust and torque are designed.With the proposed control scheme,closed-loop stability analysis is conducted and asymptotic stability of the system is proven.Consider the payloads are variable under different assignments;adaptive laws of physical parameters are designed to deal with internal parametric uncertainties.Based on the estimation value of the model parameters,an adaptive control scheme is proposed,and the control thrust and torque are designed.With the proposed control scheme,closed-loop stability analysis is conducted and ultimately uniformly bounded stability of the system is proven,and the state errors are of asymptotic convergence.Consider the latent faults in the motor of quadrotor UAV,which drives the propeller,a multiplicative factor matrix is introduced to represent the drift and the extent of the fault in the presence of actuator faults.An active fault tolerant control scheme based on adaptive method is proposed,and the control thrust and torque are designed.With the proposed control scheme,closed-loop stability analysis is conducted and ultimately uniformly bounded stability of the system is proven,and the state errors are of asymptotic convergence.Last,conclusions of this work are given,where the deficiency of this work and some valuable topics for future study are presented.