Analysis On Mechanical Performance Of Oil-powered Quadcopter

In recent years,multi-rotor aircraft has become a rising type in the field of aircraft,it is widely used in military,agricultural,fire protection and other fields due to the advantages of its various functions,powerful ability to adapt to the environment,and the flexibility to take off and land.The oil-driven rotorcraft has good development prospects because of its outstanding advantages of heavy load and long flight time.However,most researchers were devoted to the research in flight control of aircraft in the past time,it is not mature in the analysis of its mechanical properties,and the stability of the aircraft needs to be improved now.The mechanical properties of a heavy-duty oil-powered quadcopter is analyzed in this thesis.After the structural characteristics and flight principles of the heavy-duty oil-powered four-rotor aircraft is analyzed in detail,the engine,frame,gearbox-arm components,etc.are simplified and the finite element pre-processing is done,then the mechanical properties of the model is analyzed.Based on the finite element solution theory,first of all,the Lanczos eigenvalue solver is used to solve the free modal of the aircraft to verify whether the overall structure will resonate;Then,according to the stress condition of the aircraft,the static performance of the aircraft is analyzed,the stress and deformation cloud images of the structure are obtained,and the rationality of the structural strength and rigidity is verified by the verification formula;Then the modal analysis of the gearbox-arm components is carried out to obtain the natural frequency and vibration mode of this part;Then the dynamic equations of the position under different conditions are solved by using Runge-Kutta method,the influencing factors and changing rules of vibration acceleration are obtained,which showed that the rational addition of the inclined brace can reduce vibration effectively.The vibration acceleration of gearbox-arm components was tested through the experiment,and the vibration at different speeds was obtained.The collected time-domain datas are converted into the frequency-domain datas based on the fourier transform,and combined the above modal analysis results,the resonance frequency is obtained,the dangerous parts of the structure are determined.Because the length-to-diameter ratio of the thin-walled mandrel is too large and easily causes bending vibration,the structure is optimized by properly reducing the aspect ratio of the mandrel,results the modal frequency is changed to avoid the frequency multiplication and sub-multiplication of the excitation frequency,then prevent the danger of resonance in the structure.The simulation results show that the whole model of the aircraft will not resonate when it is in free motion;The structure of the aircraft meets the requirements of strength and rigidity and no damage will occur under static conditions;For the gearbox-arm components,the influencing factors of vibration are clarified based on the simulation and test results,then a diagonal support rod is added reasonably,vibration reduction is achieved,and the diameter of mandrel is optimized to avoid the resonance area.The CAD/CAE technology and the method for solving dynamic equations are used,and the simulation results are verified in combination with the relevant experiment.Achieve the integration of structural design,analysis and optimization,the accuracy of the design is improved,the costs of research and development are reduced,a strong reference for the design and improvement of heavy-duty oil-powered quadcopter is provided.