The Research On Controller Design And Optimization Methods Of Fly-Wing UAV Based On Sliding Mode

UAV is a non-manned aerial vehicle that operates remotely or can achieve autonomous flight.It has the advantages of low cost,no casualties,and can perform tasks efficiently and accurately in many dangerous environments.Therefore,research on UAVs has become a research hotspot in various countries.The flying wing UAV in this paper is a kind of unconventional layout UAV.Compared with the traditional layout UAV,the biggest difference of the flying wing UAV is the elimination of the barrel fuselage and the tail wing.Due to highly integrated design,the flying wing UAV has the following advantages: high lift-to-drag ratio,low Radar cross section(RCS),high strength and light weight.Meanwhile,the elimination of the tail wing makes the flying wing UAV longitudinal static instability,which poses a huge challenge to the design of the controller.This paper focuses on the attitude control in the autonomous flight control of UAVs,considering the compensation and cancellation of external disturbances,the stability of the system,and the optimization of the performance of the controller.First of all,this paper establishes the common coordinate system of the UAV and defines various commonly used UAV motion parameters.On this basis,based on the second law of Newtonian mechanics,the dynamic equations and kinematics equations of the UAV system are derived,and the six-degree-of-freedom nonlinear equations of the flying-wing UAV are obtained.Secondly,based on the above nonlinear model and the sliding mode theory,the attitude controller of the flying wing UAV is designed.Firstly,a fast non-singular terminal sliding mode attitude controller is designed.The upper bound of external disturbance is estimated by adaptive method,and the Sigmoid function is used instead of the symbol function to suppress the chatting effect,and a certain effect is obtained.Considering that the chattering of the sliding mode controller is difficult to eliminate,this paper designs a high-order sliding mode attitude controller of the flying wing UAV using the integral sliding mode and the non-singular terminal sliding mode.In order to reduce the conservativeness of control,a finite-time disturbance observer is designed based on the super-twisting method to estimate the actual value of external disturbances.The effectiveness of the above controllers was verified by simulation.Finally,in order to further explore the performance of the system and suppress the chattering effect of the controller,this paper adopts an improved fireworks algorithm to optimize the parameters of the controller.In order to improve the dynamic performance of the system,the four indicators of response time,arrival time,overshoot and steady state error are used as indicators for evaluating the dynamic performance of the system.At the same time,in order to suppress the chatting effect of the system,the evaluation index of chatting is designed.Based on the traditional fireworks algorithm,the genetic crossover algorithm is used to improve the variation process of the fireworks algorithm,and the fitness information of the fireworks(or spark)particles is used to improve the selection strategy of the fireworks algorithm,so that the fireworks algorithm can utilize all the fitness information of the fireworks(or spark)particles to improve the diversity of the algorithm and prevent the algorithm from falling into a local optimal solution.The simulation proves that the optimized controller of the fireworks algorithm not only improves the dynamic performance of the system,but also strengthens the resistance to external disturbances.It also greatly suppresses the chattering effect of the control output and achieves the expected optimization effect.