Research On Active Disturbance Rejection Control Algorithms For Quadrotor UAV Attitude

The quadrotor unmanned aerial vehicle,also known as the quadrotor,is a multi-axis aircraft.Through the thrust provided by the four rotors,the drone will be lifted or maintain its attitude to achieve hover and flight.Because the four rotors are of the same size and symmetrically distributed,the drone can be controlled by adjusting the relative speed between different rotors to adjust the thrust of different positions and overcome the anti-torque between each rotor to maintain the posture or complete various maneuvers.For attitude control of quadrotor UAVs,the commonly used method is PID control,but the PID control has the defects of large overshoot or disturbance suppression.Therefore,this paper has completed the following research on attitude control algorithms based on active disturbance rejection control:1.In order to improve the effectiveness and accuracy of the control system and to solve the shortcomings that having too many parameters and failing to update the tuning of these control parameters timely of the nonlinear active disturbance rejection control,this paper puts forward a kind of attitude stability control method of the combination of seeker optimization algorithm with inertia term and active disturbance rejection control.The methods of inertia coefficient about the step and direction of searching are modified to achieve quadrotor UAV's attitude control during the disturbed flight process.The simulation experiment analysis presents that when compared with the seeker optimization algorithm parameters self-tuning active disturbance rejection control and the active disturbance rejection control without self-tuning,this control method improves the performance of the dynamic response,anti-disturbance and robustness,thus holding practical value to improve the attitude stability control of quadrotor UAV.2.The quadrotor UAV is susceptible to nonlinear and uncertain factors,which makes the attitude stability control difficult.A nonlinear control algorithm based on internal and external loop structure is proposed to stabilize attitude control to solve the decline of the attitude control performance brought by linear control and the phenomenon of "peaking" caused by initial state error.The external loop of the controller adopts nonlinear PD control,and the inner loop adopts nonlinear active disturbance rejection control.The tracking differentiator with finite-time convergent is used to improve the structure of the original active disturbance rejection controller,which makes the inner ring converge faster than the outer ring,and the stability of the closed-loop system is ensured.The simulation results show that the nonlinear controller can realize the UAV flight attitude control under any initial state,the response speed is faster than the linear control,and the stable attitude control are still maintained under the condition of interference.3.A sliding mode active disturbance rejection controller is designed based on active disturbance rejection control and sliding mode control for quadrotor UAV,which is susceptible to nonlinearity,multiple targets,limit of control and other uncertain disturbance.Considering the unknown attitude angle velocity of the controlled targets,the controller can observe the attitude angular velocity and unknown interference of UAV by designing the extended state observer.The estimated angular velocity is used to the feedback of controller,meanwhile the observed disturbance compensates the amount of control.Based on Lyapunov theory,the stability of the control system was proved.The simulation results show that sliding mode active disturbance rejection controller can guarantee the fast convergence of the observed error,realize the simplification of control parameters and the high-precision estimation of the observed measurement,and can maintain stable attitude control under the condition of unknown velocity of attitude.