Research On Attitude Control Method For Quadrotor UAVs

Quadrotor unmanned Aerial Vehicle(UAV)has the advantages of simple structure,light body weight,high flexibility and can take off,land vertically,hover at a fixed point.It has been widely used in environmental monitoring,target search,accident rescue and other fields.The dynamic model of quadrotor is an underactuated nonlinear system with strong coupling and it is susceptible to external disturbances during flight.In order to improve the performance of quadrotor UAV control system,the paper focuses on the attitude control of UAV.The main contents are provided as follows:(I)Considering the attitude control problem of UAV with unknown upper bound of uncertain disturbance,a finite-time attitude controller design method based on adaptive multivariable disturbance compensation is proposed.Firstly,an adaptive multivariable disturbance observer based on supertwisting sliding mode is designed,and sufficient conditions for finite-time stability of the disturbance observer are derived by using Lyapunov technique.Secondly,the integrated design of controller-observer is completed,and the stability of the closed-loop system is strictly proved by homogeneity theory and Lyapunov technology,which ensures that UAV can realize the finite-time stable tracking control for a given reference command while completing the online estimation of the external synthetic disturbance.(II)Considering the fixed-time tracking control problem of UAV under the circumstance of uncertain influence and output feedback,a method of fixed-time controller based on double-limit homogeneity theory is proposed.Firstly,a fixed-time observer based on the double limit homogeneity theory and arbitrary order robust sliding mode differentiator is designed to simultaneously observe unknown states and external disturbances of UAV.Secondly,a fixed-time attitude controller is designed based on the double-limit homogeneity theory and Lyapunov technology,and the stability of the fixed-time controller-observer is analyzed to ensure that the system can realize fast tracking control of a given reference command in a fixed time while observing unknown states and external disturbances of UAV.(III)Considering the effects of uncertainties,dynamic and steady-state characteristics on the attitude control performance of UAV,a method of attitude controller based on adaptive multivariable prescribed performance is proposed.Firstly,a time-varying prescribed performance function with exponential attenuation characteristics is designed,and an adaptive law based on prescribed performance is constructed to ensure dynamic adaptive gain that can suppress synthetic interference.Secondly,an adaptive multivariable prescribed performance controller is designed.Based on Lyapunov technology,the stability of the system is analyzed,and the prescribed performance boundaries of attitude tracking errors of UAV are deduced to ensure that the system can effectively suppress external disturbances and achieve comprehensive control of the steady-state performance and dynamic performance of UAV.