Active Disturbance Rejection Control System Design For Quadrotor UAV

Flight control technology is the core technology of quadrotor UAV,and its design level directly determines the flight performance of quadrotor UAV.In this paper,we focus on the flight control system of quadrotor UAV and hope to design a flight control system which has superior control performance.Firstly,the dynamic model of quadrotor UAV is derived based on Newton-Euler method.The dynamic model shows that quadrotor UAV is a complex nonlinear system,which has the dynamic characteristics of underactuated,strong coupling and vulnerability to external disturbances.The above dynamic characteristics increase the difficulty of flight control system design.In the case of neglecting the coupling among the different channels,the flight control system is designed based on PID control,and the stable flight control of quadrotor UAV is realized.The simulation results show that PID control can achieve the stability control of quadrotor UAV,but considering the coupling effect and external disturbances,the control performance is significantly reduced and it is unable to realize the high efficiency and high precision control.In order to solve the problem of attitude coupling and to improve the anti-disturbance ability of controller,the attitude controller and height controller are designed based on linear active disturbance rejection control(LADRC).By analyzing the attitude dynamic equations,the attitude coupling are divided into two parts: static coupling part and dynamic coupling part.For the static coupling,a set of virtual control variables are introduced to eliminate the effect of coupling.For the dynamic coupling,it is taken as the system internal disturbance which is estimated by linear extended state observer(LESO)and compensated in the control law.In addition,LESO can also estimate and compensate external disturbances precisely.The simulation results show that the control system can realize attitude decoupling control and can eliminate the impact of external disturbances on the system.In order to further improve the flight quality of quadrotor UAV,the controllers is designed based on nonlinear active disturbance rejection control(NLADRC).Nonlinear active disturbance rejection controller adopts nonlinear extended state observer(NLESO)and nonlinear state error feedback(NLSEF),the controller has superior performance in both decoupling control and anti-disturbance ability.