Structural Design And Stability Analysis Of Heavy Duty Four Rotor UAV Frame

Four rotor aircraft has developed rapidly in recent years.With the advantages of automatic control,simple operation and strong mobility,it is widely used in civil and military fields.It is a hot spot in the UAV market at home and abroad.Based on the shortage of load capacity and endurance time of traditional four rotor UAV,design an oil powered heavy-duty four rotor UAV and focus on the mechanical characteristics and stability analysis of the frame.After determining the transmission layout of the UAV and briefly describing its flight principle,the pretreatment of the frame,transmission system,gearbox,etc.Firstly,the pretreatment of the frame,transmission system and gearbox are carried out,and the mechanical analysis of the whole structure is carried out;According to the stress conditions of the UAV,the static analysis of the UAV frame,frame,landing gear and other structures are carried out to obtain the stress and strain nephogram,and its rationality is verified by the verification formula;The buckling deformation of the UAV arm under the maximum overload state is verified by experiments,and the rationality of the arm is verified by the finite element analysis results.Then the block Lanczos mode extraction method is used to solve the free mode of the UAV.According to the natural frequency and vibration mode,it is verified whether the structure will have resonance.The superposition mode method is used for harmonic response dynamic analysis to obtain the excitation frequency of the UAV under sinusoidal excitation,and further analyze its vibration characteristics;The buckling stability of the end frame of the UAV is analyzed,and the load coefficient and buckling load are obtained by using the finite element buckling analysis module;The fatigue of the end frame is checked according to the calculation formula of asymmetric cyclic stress,which provides a basis for judging the stability and fatigue characteristics of the structure.Finally,according to the analysis results of the vibration characteristics of the frame,the frame structure is optimized.The natural frequency of the optimized frame structure can avoid the working frequency of the engine,and the structure design meets the design requirements.The results show that the UAV model and its components meet the strength and stiffness requirements under dynamic and static loads;After structural optimization,the frame structure will not resonate under free motion and sinusoidal excitation,and can effectively avoid the excitation frequency.In the experiment,the outer shaft of the UAV support arm did not yield under the tension of limit load,limit load and failure load.The overall design work of heavy-duty four rotor UAV is summarized to provide ideas for the follow-up design of heavy-duty multi rotor UAV.