Research On Fault-Tolerant And Precision Altitude Control Strategy Of Hexarotor UAV

Compared with the quadrotor,the hexarotor unmanned aerial vehicle(UAV)has redundant actuators and a larger load capacity,so it has a stronger anti-interference ability,higher safety,and is able to adapt to more severe flight environment and complete more complex tasks.Therefore,this paper takes the hexarotor UAV as the experimental platform to carry out a series of research work.Firstly,this paper introduces the hardware structure,flight principle,coordinate system definition and attitude angle representation of the hexarotor UAV.And the dynamics and kinematics models of the hexarotor UAV were established,which lay a foundation for the simulation and actual flight experiment of the attitude control,fault-tolerant control and precision altitude control of the hexarotor UAV.Secondly,three different attitude control algorithms are designed: cascade PID control,active disturbance rejection control(ADRC)and PID control based on BP neural network.And they are applied to the attitude control scheme of the hexarotor UAV.The dynamic characteristics of three different schemes are analyzed through the simulation experiment data,and cascade PID control is selected as the basic control law of the following fault-tolerant control by comparison.Thirdly,the mathematical model of the hexarotor UAV under the fault is established for the fault of the actuator,and a fault-tolerant control scheme based on cascade PID control and control allocation is designed.The control effect of this control scheme is verified by simulation experiment.At the same time,the fault-tolerant control scheme was transplanted to the PIXHAWK platform for real flight experiments,and experimental data were analyzed according to the flight log of the ground station.Finally,the application scenario and significance of precise altitude control of the hexarotor UAV are introduced,and the fault-tolerant control scheme designed above is still effective for altitude control.At the same time,double closed-loop ADRC scheme and cascade PID control scheme based on feedforward are designed and verified by MATLAB/Simulink simulation experiment and real flight experiments.The fault-tolerant control scheme and the altitude control scheme proposed in this paper have both carried out simulation experiments and real flight experiments,and the experimental data have been analyzed.The experimental results show that the fault-tolerant control scheme and the altitude control scheme can guarantee the stable flight of the UAV and improve the altitude control accuracy.They provide valuable reference for fault tolerant control and altitude control of UAV,and have certain theoretical significance and practical value.