Research On Flight Control Of Receiver Aircraft In Flying-boom Aerial Refueling Phase

Aerial refueling has been developed into an effective method to enlarge the range,endurance,and payload of aircraft.Flying-boom refueling has the advantage of the fast fuel transfer rates,which however puts high demands on the performance of receiver aircraft's flight controller during the refueling operation.Hence this paper studies receiver's flight control in flying-boom refueling phase.First of all,the tasks of each stage and requirements of receiver flight control system in the process of flying-boom refueling are analyzed,which draws a conclusion that the key points that need to be solved during the refueling process are modeling and relative position-keeping control of receiver with mass variation.Then the six degrees of freedom model of receiver is established with considering the varying fuel mass of receiver.Secondly,a fuel tank of receiver is modeled and then three refueling strategies are designed to study the impact of the fuel transfer on receiver.The nonlinear model of receiver is utilized to analyze the influence of fuel transfer on the receiver in terms of the center of gravity,inertia matrix and natural characteristics of receiver.The results show that fuel transfer has a considerable influence on the receiver's longitudinal motion under the three fueling strategies.Thirdly,a hierarchical approach is used to design the relative position-keeping control system of receiver.The active disturbance rejection control technique based inner-loop controller is developed to stabilize receiver.Extended state observer is utilized for online estimation and compensation of the influence of the fuel transfer on receiver.Then outer-loop controller is designed based on double power reaching law based sliding mode control with considering the uncertainty of the model.It is proved that closed-loop system is asymptotically stable via Lyapunov function.Finally,a detailed aerial refueling simulation system is established based on MATLAB/Simulink where the simulation system is used to test the effectiveness and robustness of the designed receiver's relative position-keeping control system.The simulation system consists of a tanker model with flight control system,a receiver model with flight control system,and aerodynamic disturbance model.The simulation results demonstrate that under the different fuel rates,the designed control system can keep receiver's receptacle within the refueling envelope in the presence of air disturbances.