The Path Tracking Control Methods Research Of Small Fixed Wing UAV

The fixed wing unmanned aerial vehicle(UAV)has unique advantages due to its high payload capacity,long range and fast flight speed,and is widely used in military and civilian applications.Flight control system is an important component of fixed wing UAV,which plays a significant role in improving the flight performance of fixed wing UAV.path tracking is one of the key technologies of flight control system.In this paper,for the longitudinal,lateral control and path tracking problems in the flight control of small fixed wing UAVs,an improved active disturbance rejection control method is used to achieve accurate control.Based on sliding mode control,the S-plane control is introduced to achieve high precision tracking of the desired path.Finally,the simulation verification was carried out under external wind disturbance conditions using Matlab/Simulink.After obtaining the coordinate transformation relationship of each coordinate system,the kinematics model of the fixed wing UAV is constructed.Based on Newton’s second law and the theorem of moment of momentum,the dynamic equations of fixed wing unmanned aerial vehicles are obtained.Then,the longitudinal motion equation and the lateral motion equation are linearized using the small perturbation principle.at the same time,modeling research is carried out on the composition of external wind.First the mathematical model of basic wind、gust model、random wind and arbitrary wind are established.and then construct corresponding wind models according to the requirements of the external wind environment and complete simulation verification.The nonlinear state error feedback control law(NLSEF)module in the active disturbance rejection control(ADRC)algorithm is replaced by an improved sigmoid two-dimensional function to improve the control accuracy when the six degrees of freedom model of a fixed wing UAV is decoupled into longitudinal and lateral directions.The improved ADRC can normalize the output value of the NLSEF control to between [-1,1].Aiming at the problems of low tracking accuracy and weak anti-interference ability in path tracking of fixed wing UAV,a global stable integral sliding mode Radial Basis Function S-Plane(GSISM+RBF S-plane)control is desired,and the controller is desired by combining the inner and outer loops.The outer loop adopts integral sliding mode control based on global stability,and the inner loop uses S-Plane control.In addition,the unknown part of the modeling is estimated using radial basis function neural network functions.The second order differentiator is used to solve the integral explosion problem in the derivation of the S-plane control.Finally,the designed algorithm was simulated and validated using Matlab/Simulink in two cases: wind interference and no wind interference.Under the condition of given expected speed and roll Angle changes,the simulation of the longitudinal and lateral states of the fixed wing UAV is realized.In path tracking control,the algorithm’s feasibility and control performance are verified by tracking desired spatial straight line,spiral line,and spatial special curve.Simultaneously,the control performance of the designed algorithm was verified through Matlab/Ros.