Quad-rotor Aircraft Control Based On Fractional PID

The quadrotor aircraft is a kind of flying equipment with symmetrical structure,light weight,which also has the performance of autonomous takeoff,landing,hovering and reverse flight.Many advantages of the quadrotor have attracted widespread attention from scientific research institutions and technology companies.However,quadrotor has the characteristics of non-linearity,strong coupling,under-actuation and disturbance sensitivity,which brings great challenges to the stability control of quadrotor.In this dissertation,Qball2 quadrotor aircraft is taken as the research object,aiming at designing a controller with anti-disturbance and strong robustness.The main contents of this dissertation are as follows:Firstly,the main components and flight principle of Qball2 quadrotor aircraft are introduced,and stress analysis of the quadrotor is discussed.The mathematical model of the quadrotor is deduced based on Newton's second law and angular momentum theorem.According to the mathematical model and flight principle of the quadrotor,the control strategy of the double closed loop is designed.Secondly,aiming at the disadvantage of poor robustness and anti-disturbance of traditional PID controller,the fractional order PID controller is designed by introducing integral order,and differential order,u.The rational realization of fractional order calculus operator s? is obtained by using improved approximation method.The attitude simulation and position tracking simulation verify that the fractional order PID controller has better dynamic performance and strong anti-disturbance.The control effects of PID and fractional order PID are compared under the condition of parameter perturbation,and the results show that the fractional order PID controller has better dynamic performance and stronger robustness.Thirdly,in order to improve the influence of the parameter perturbation of the active disturbance rejection PD controller,fractional order PD is used to replace the traditional PD controller,and the feedback control law is improved by measuring value instead of observing value.The improved fractional-order PD active disturbance rejection controller(FOPD-ADRC)is applied to the attitude and position control of the quadrotor.The simulation results show that the FOPD-ADRC controller has better rapidity than the integer-order PD ADRC(IOPD-ADRC).Under the condition of system parameter perturbation,the adjustment time and overshoot of FOPD-ADRC controller are less.In the case of controller parameter perturbation,the adjustment time of the FOPD-ADRC controller is smaller and shows stronger robustness.Finally,the designed fractional order PID controller is applied to the attitude and altitude control of Qball2 quadrotor,and satisfactory control results are obtained.Further,in the hovering experiment,in order to make full use of the high differential information collected by the experimental platform,a second-order low-pass filter is designed to extract the change rate of the height given value.The difference between the actual and the height given change rate is proportional controlled,thereby replacing the differential term of the fractional-order PID controller.By comparison,it is proved that the second-order filter extraction change rate has smaller stable time and static error.And then,the FOPD-ADRC is applied to the attitude and height control of Qball2 quadrotor.