| The tilt-wing aircraft is a new concept aircraft proposed to solve the problem of aerodynamic interference among the rotor,wing and fuselage of tilt-rotor aircraft,which is characterized by the simultaneous rotation of the external wing and the rotor,and can greatly reduce the aerodynamic influence caused by the interaction of the rotor downwash flow on the upper wing.In this paper,the return section of tilt-wing UAV(namely,the tilt-wing UAV changes from the forward-flying fixed-wing mode to the vertical take-off and landing helicopter mode)is the main research object.Compared with the take-off stage,the actual landing conditions are more complex,and the aircraft is prone to stall or face other unstable conditions,if the speed is too fast,the aircraft is more difficult to control,and the control design of its high tilt is much more difficult.In this paper,transition corridor curve is obtained by simulating the return transition of tilt-wing UAV,which can provide theoretical basis for its stable tilting control system.Compared with tilt-wing UAV,technology of multi-rotor UAV is relatively mature and has a wider application range,such as in weather forecasting.In order to explore the influencing factors of wind measuring accuracy of multi-rotor meteorological UAV,this paper carries out numerical calculation of multi-rotor meteorological UAV under various working conditions and compares it with actual flight data,so as to further verify the influencing factors of wind measuring accuracy.The main contents of this paper are as follows:The first part introduces aerodynamic analysis and performance optimization of the return translation section of tilt-wing UAV.The tilt-wing UAV model is firstly built in proportion in CATIA,the exported.stp file is then imported into the Mesh module of Workbench for grid division,and the.msh file is imported into Fluent for calculation.Since the aerodynamic characteristics of translation section are nonlinear and strongly coupled,the establishment of momentum source method and slip grid technology can effectively capture the aerodynamic characteristics of continuous translation section of tilt-wing UAV,and shorten the time needed for its return tilting by adjusting rotor speed and tilting angle speed.On this basis,the fit curves of different functions are written into the program through Matlab to ensure certain stability and improve efficiency while shortening the time,and the corridor curve of the transition section is obtained.This result reduces the difficulty of the control design during return transition section.The second part studies the influence of wind field measuring accuracy of multi-rotor meteorological UAV.This part carries out numerical simulation under various working conditions in different ascending speeds of air flow,different crosswind speeds and different wind direction angles,and compares it with the actual flight data of multi-rotor meteorological UAV at high altitude to obtain the influencing factors of wind measurement accuracy,so as to verify in which cases the wind measurement effects are the best and more consistent with the real flight situation.The rotation of UAV rotor will affect the flow field and cause errors in wind measurement results.Under the same flow field conditions,the higher the wind speed and the bigger the tilt angle of the UAV fuselage,the more accurate the measured wind speed will be. |
