Research On Unpowered Landing Technology Of Stratospheric Unmanned Aerial Vehicles

The stratosphere is valued by more and more countries due to its special environmental characteristics and potential military value.The unpowered landing can reduce the fuel carrying and energy losses of the aircraft.Aircraft with unpowered landing mode can even not install an engine.This paper studies the unpowered landing technology of stratospheric unmanned aerial vehicles.When the aircraft's cruising stage is over and the aircraft engine is shut down,the aircraft begins a landing research program from the stratosphere.The main research contents are as follows:Firstly,the landing trajectory of the aircraft is roughly planned.Based on the threedegree-of-freedom longitudinal model of the aircraft,the landing trajectory of the aircraft is divided into the entry section,the energy management section,the approach landing section,the grounding leveling section and the ground sliding section.The attack Angle of the aircraft is calculated based on the force balance of the aircraft,and the elevator deflection Angle of the aircraft is calculated based on the longitudinal stability and torque balance.According to the angle of attack of the aircraft and the yaw angle of the elevator,it is judged whether the trajectory is suitable.Finally,the simulation in MATLAB/Simulink environment verifies the feasibility of the method.Then,a vertical energy consumption scheme based on track change is proposed for the case where the energy of the aircraft in energy management section is too high.The program increases the voyage by adjusting the glideslope of the aircraft to increase the energy dissipation.The range of energy in the energy management section that the aircraft can land safely is calculated.When the aircraft energy is too high,it will slide down with a deeper glideslope.Until the energy is the same as the nominal energy line,the aircraft will complete the shallow glide at the glide angle that can slide to the junction of high and low air.Finally,in the MATLAB/Simulink environment,the longitudinal energy consumption scheme of nominal condition and deflection is simulated and analyzed.It is verified the feasibility of the scheme.Finally,an energy consumption scheme based on cross rudder is proposed for the case where the energy of the aircraft in energy management section is too high.The program changes the elevator structure and splits each elevator structure into two pieces.When the aircraft energy is normal,the two rudders of the aircraft as a whole are deflected together.When the energy of the aircraft is too high,the rudders of the aircraft are deflected positively and negatively to increase the resistance of the unit voyage.Then,according to the aerodynamic characteristics of the aircraft,the feasibility of the scheme was demonstrated.Also,in the MATLAB/Simulink environment,the initial energy of the aircraft is increased for simulation analysis,which verifies the feasibility of the scheme.Finally,the cross rudder energy consumption scheme and the vertical energy consuming scheme are compared,and the advantages and disadvantages of the two schemes are analyzed.