Take-off And Landing Control For Flying-wing Unmanned Aerial Vehicle

With advantages of high lift-drag ratio and prominent stealth performance,the flying-wing has been the preferred layout of unmanned aerial vehicle(UAV).Because of blended wing-body and configuration,the nonlinearity of pitch moment,low longitudinal static stability,less range of attack angle with longitudinal static stability,low directional static stability,strong channel coupling,nonlinearity of drag rudder efficiency and actuators coupling,have been serious problems of flying-wing UAV.Above problems limits the performance of take-off and landing control system,which based on classical control theory and gain scheduling method.In addition,the dangerous microburst and unsatisfactory runway condition are threats to the safety of take-off and landing.Therefore,to solve the problems of flying-wing UAV while take-off and landing,in this paper,the robust take-off and landing control method which is easy to realize in engineering project,the control method of flying-wing UAV during penetration of microburst,the robust lateral deviation correction control metod are in-depth research,the comprehensive design and simulation of the take-off and landing control system are completed.The main research results are follows:(1)The flying-wing UAV nonlinear dynamic model both aerial and on ground is built.According to related literature,the nonlinear aerodynamic force and moment model,wind shear model including microburst,ground force and moment model including consideration of landing gear elasticity and runway condition,are given.The difference of aerodynamic characteristics between flying-wing UAV and conventional airplane are compared.The flight qualities while take-off and landing,the influence of ground effect and landing gear on longitudinal flight qualities,and the influence of aerodynamical characteristics nonlinearity and actuators coupling of drag rudder are analyzed.(2)For the problems of the strong longitudinal aerodynamical characteristics nonlinearity,strong channel coupling,nonlinearity of drag rudder efficiency and actuators coupling,the attitude control law base on cascade active disturbance rejection control(ADRC)is modified.A method to solve effect of drag rudder efficiency nonlinearity on LESO is proposed.The simulate results shows that the command track precision and dynamic performance of modified cascade ADRC attitude control system is satisfactory.(3)For the problem of excessive airspeed during landing due to the narrow range of attack angle with longitudinal static stability,and unsatisfactory wind-resistance performance.The take-off and landing control method which is easy to realize in engineering project is proposed based on ADRC.With the proposed control method the airspeed during landing is reduced,and the wind-resistance performance is improved.The hardware-in-the-loop simulation is carried out and the result proves the effectiveness,easy implementation,and good real-time performance of the control method.(4)For reducing the altitude loss of flying-wing UAV duing penetrating microburst,a compound control method combines the fast-response elevator additional lift control with aerodynamic control is proposed.The compound control system is designed based on ADRC.The simulated result shows the proposed control method reduces the altitude loss of flying-wing UAV to no more than 0.6m during penetration of microburst.(5)For reducing the lateral deviation in the effects of unsatisfactory runway condition and crosswind during take-off and landing roll,a method of nonlinear lateral deviation control based on ADRC is proposed.The control allocation based on reallocation weighted generalized inverse method is adopted for the rational use of front-wheel steering,drag rudder and main wheel differential brake.The simulated result shows the proposed control method keeps flying wing UAV near the runway center line during roll while part of runway covered with snow and in the effect of crosswind.(6)The complete take-off and landing control system of flying-wing UAV is designed,whitch is synthesized by the take-off and landing control method,the control method for penetration of microburst,and the method of nonlinear lateral deviation control proposed in this paper.The simulated result shows the designed control system could trace control command accurately and realize high-precision take-off and landing,in the effects of the aerodynamical characteristics nonlinearity,strong channel coupling,actuators coupling of drag rudder,crosswind and microburst,groud effect,and the partial snow-covered runway.