Reseach On Autonomous Aerial Refueling Docking Under Bow Wave

UAV has become an important air combat force in modern wars due to its increasingly diverse combat operations and outstanding combat capabilities.Autonomous aerial refueling can increase the range,endurance,load capacity,and combat effectiveness of UAV.But in the process of docking,when the receiver is drawing slowly near to the drogue,the drogue will be pushed far away from the head of the receiver under the action of the bow wave and thus results in docking failure which may endanger the vehicles.To improve the performance of load and stealth,UAVs usually adopt a flying wing layout.However,it is difficult to model the bow wave of flying wing UAV,which puts forward new requirements for the bow wave modeling method and docking control policy.This paper,according to the mission requirements of the autonomous aerial refueling,firstly establishes the 6 DOF nonlinear dynamic equation of the aircraft to have the aircraft trimmed in the normal state,then goes ahead with a formulation of the turbulence model and the wake model,and lastly,on this basis,derives the dynamic model of the hose-drogue.The bow wave models of the conventional layout aircraft are modeled by an integration of the Rankine body and the fitting Rankine body,and the bow wave models of flying wing layout aircraft are modeled by the bow wave model based on BP neural network.Furthermore,the movement of hose-drogue under the bow wave in different docking environment,docking mode,receiver layout,and hose material are analyzed.A comparison of the bow wave model based on BP neural network with the CFD data tells slight differences in data,and therefore the bow wave model based on BP neural network can establish the flying wing layout aircraft bow wave model accurately.The simulation results show that the bow wave of conventional layout aircraft pushes the drogue diagonally upward from the receiver,and the flying wing layout aircraft of the bow wave makes the drogue move straight upward,that the bow wave disturbance can be reduced by docking at high altitude,low speed and low docking speed from the lower back of the tank,and by a reasonable design plan of the hose material and cross-section.To suppress the disturbance of the bow wave effect,a control policy based on the prediction of the docking position is proposed,and a trajectory generator and a n LQR trajectory tracking controller are designed to control the receiver.By combining the control loop of the aircraft with the hose-drogue motion loop,and adding the visual simulation module,an autonomous aerial refueling simulation system is established.The predicted docking position required by the control policy can be obtained through multiple simulation iterations of the integrated simulation system.The simulation results show that the LQR control system can effectively control the docking trajectory of the receiver and that in the docking process,through the control policy proposed,the attitude of the receiver is stable,and the receiving plug is accurately inserted into the drogue,which fully verifies the feasibility of the docking policy.