Design And Energy Optimization For Morphing Wing Solar-Powered UAV

The solar-powered unmanned aerial vehicles(SPUAVs)can carry out intelligence surveillance reconnaissance(ISR)missions conveniently and quickly with visible light camera,infrared camera,synthetic aperture radar(SAR)and other device.However,most solar-powered UAVs can only achieve perpetual flight during summer days.The weak solar radiation during winter days in middle and high latitude regions still pose great challenges for achieving perpetual flight.The design scheme of morphing wing SPUAV has the potential to increase solar energy conversion utilization in winter.As a new concept,there are few studies on morphing wing SPUAVs that have been carried out.In this investigation,the energy optimization models for morphing wing SPUAVs are established.Based on the energy optimizing model,the optimal flight strategy and energy acquisition advantages over planar wing SPUAV are studied.The main contents of this paper are shown as follows:(1)The relation function between solar irridiance intens ity and latitude,height and date is obtained by establishing the high altitude and low altitude solar radiation model.At the same time,the calculation model of solar incidence angle under different flight attitude is derived.A Z-shaped sun-tracking morphing wing SPUAV is designed,and the aerodynamic performace and trim characteristics during the Z-shaped wing morphing process are studied.The additional solar power harvesting models of the Z-shaped morphing wing SPUAV under different flight conditions are derived considering of the sun shadow problem and the decrease of sun elevation angle of partial wing.The coupling of additional solar power harvesting and extra power consumption is solved with the net power input model which can be used to the optimization calculation of morphing wing SPUAV.(2)An optimal flight planning method for the morphing wing SPUAV is proposed which can be used to study the optimal morphing angle and the optimal flight trajectory during the daylight flight.The optimal flight strategies of the Z-shaped morphing wing configuration are studied based on the variable of time and sun elevation angle.It is verified that the proposed optimization method can effectively increase the net power input at low sun elevation angle.(3)Based on the optimization model and combined with the different conversion efficiency of solar cells,the maximum net energy input and maximum theoretical perpetual flight latitude of the example Z-shaped sun-tracking morphing SPUAV on the winter solstice are investigated numerically.The results shows that,with the optimal flight planning method,the higher conversion efficiency of solar cells can enhance the Z-shaped morphing SPUAV to achieve more net energy input.The maximum net energy input increases and then decreases with the latitude increasing,and reaches themaximum values near 51 degrees of north latitude.The optimization method for the Z-shaped morphing wing can improve the perpetual flight latitude significantly,and the increase of perpetual flight latitude increases with the solar cell conversion efficiency increasing.(4)An N-shaped morphing wing solar-powered UAV is proposed which can be used to solve the sun shadow problem and the decrease of sun elevation angle of the Z-shaped morphing wing.The drive mechanism of wing morphing is designed and a design scheme for achieving adaptive wing morphing and tracking the sunlight is proposed.The aerodynamic characteristics during the N-shaped wing morphing process are studied which show that the aerodynamic characteristics variation is acceptable,the control surfaces' trimming angles are relatively small to counteract the moments caused by the antisymmetric wing morphing.Investigation on the flight dynamic modes shows that the morphing wing has a relatively larger impact on lateral-directional dynamics than longitudinal dynamics.The pitching static margin increases with the dihedral angle increasing.(5)The optimization model for the N-shaped morphing wing SPUAV is proposed by deserving the net power input model.The comparison and analysis of energy balance margin and maximum perputual flight latitude of conventional planar wing and N-shaped morphing wing are carried out based on the optimization model.The investigaiton shows that the N-shaped sun-tracking morphing wing configuration can significantly increase the net energy input,achieve more energy balance allowance,and theoretically achieve perpetual flight at higher latitude.In addition,a successful flight test is carried out that indicates that the wing morphing design is feasible.