Attitude Platform Design And Control Of A Quadrotor

In this paper,the attitude control of a quadrotor under the influence of internal uncertain dynamics and external disturbances is investigated.The control problems of a quadrotor can be generally divided into attitude control,position control,trajectory tracking control and autonomous flight control.In order to meet a series of practical applications and mission requirements of a quadrotor,high-precision attitude control is very important,and it is also the premise of other three control problems.Especially in the outdoor environment,the quadrotor is easily affected by the wind disturbance,which is the main part of the external disturbances.Traditionally,in order to simplify the processing and analysis,the system model of a quadrotor is often linearized,and the existence of external wind disturbance is ignored.In fact,in the process of a quadrotor flying,the external wind disturbance will significantly reduce its attitude control performance,while the traditional linear controller is difficult to achieve high-precision attitude control.Therefore,it is an urgent problem to find a more suitable controller to ensure the attitude control effect with high accuracy under the influence of internal uncertain dynamics and external wind disturbance.First of all,the application background,research status,difficulties and challenges in flight control of a quadrotor are introduced,and explains the practical significance of the research content.In addition,the related control technologies,such as PID control technology,active disturbance rejection control(ADRC)technology,sliding mode control(SMC)technology,which are involved in the attitude control algorithm design of the quadrotor in this paper are also summarized.Secondly,the basic structure,working principle,the establishment of coordinate system and the relationship of coordinate transformation of the quadrotor are described in detail.Through the flying principle,the mathematical model of the quadrotor dynamics system is established,and the established system model is processed and analyzed,which lays the foundation for the next theoretical design of the quadrotor attitude control.Thirdly,a double closed-loop attitude control strategy is designed to solve the problem that it is difficult to achieve high-precision attitude control in the actual flyingenvironment when the quadrotor is affected by external wind disturbance.The control strategy combines the advantages of ADRC and SMC.In the inner loop,a state error feedback controller based on a nonlinear extended state observer is designed to compensate the total disturbances of the quadrotor system.In the outer loop,the integral sliding mode controller can drive the quadrotor to the desired target attitude with fast response speed.In addition,by using Lyapunov theory,it is further proved that the estimation errors of the designed nonlinear extended state observer and the inner and outer loop tracking errors of the double closed-loop control strategy are convergent.Finally,in order to verify the effectiveness of the double closed-loop attitude control strategy proposed in this paper,a set of quadrotor experimental platform and attitude debugging experimental platform are designed and built.Through a series of outdoor free flight experiments and indoor three degree of freedom comparative experiments,it is proved that the control algorithm designed in this paper is effective in dealing with the attitude control problem of the quadrotor under the influence of internal uncertain dynamics and external disturbances.