Vibration Behavior Analysis And Test Verification Based On 3WQF80-10 Engine Driving Unmanned Helicopter Frame

The agricultural plant protection engine driving unmanned helicopter is excited by the dynamic loading from the engine when the unmanned helicopter is in the air,leading to the vibration of fuselage and lance.Therefore,this paper studies the problem of frame vibration caused by engine vibration,and the influence of the excitation frequency of the engine on the vibration of the whole machine is analyzed.On the basis of this,a solution to the vibration problem of the frame is proposed.In this paper,the vibration behavior of a certain type of oil dynamic plant protection unmanned helicopter frame rod are analyzed by the finite element analyze.At the same time,the static stress analysis of the frame structure is carried out.The vibration characteristic of frame has been deeply and systematically comprehended through the Modal Analysis and Harmonic Response Analysis.The frequency response curve of two spray lance connection points is extracted,and founded the cause of the vibration of the frame.It provides the important basis of solving the vibration of frame,and has some theoretical significance and important practical value.The main working and researches have been completed as follows:(1)Based on the vibration characteristic of the structure,the plans and methods of research and design were be designed.(2)Analyzing the composition of the oil moving unmanned helicopter system,and using three-dimensional entity unit as the basic element of finite element.The frame structure is separated by high order unit,on the basis of it the practical finite element model has been established.Based on the finite element model of the frame,the linear static analysis is carried out,the results show that the stress value is the most in the joint position of the tank support plate and the two sides plates,the maximum value for 15.248 MPa,and the strain value is the highest,deformation of the largest.It is suggested that when designing the uav,the strength and rigidity of the medicine cabinet and the fuel tank support plate should be paid attention to.On this basis,the quality should be minimized and the lightweight design of unmanned helicopter should be realized.(3)Analyzing the finite element model of the frame under free vibration condition and the finite element model of frame is divided by Patch method.Using program controlled solver to solve the natural frequencies and modes of vibration of the frame model,in order to obtain the natural frequencies and modes of the first six non-rigid modes.In order to ensure the reliability of the frame finite elementmodel in practical engineering,the accuracy of the model is verified by modal test,the modal information of the frame structure is extracted by single-input multiple-output.The similarity between numerical modal and experimental mode is compared by modal correlation.The results show that the modal frequency difference between the experimental mode and the numerical mode is less than 10%,the modal confidence criterion of vibration mode is greater than 0.8.The finite element model of frame structure has the reference value of engineering application.(4)Based on the ANSYS finite element analysis platform,modal superposition method is used to analyze the harmonic response of engine frame model under harmonic load excitation,the vibration of each part of the helicopter was investigated.According to the calculation,it can be determined that the problem of the vibration of the frame caused by the unbalance of the engine is mainly caused by the excitation frequency around 31 Hz,and the results of modal analysis and the accuracy of finite element model are verified.(5)According to modal analysis and harmonic response analysis results,proposing two solutions for vibration of frame: First option is that by adjusting the transmission ratio of the transmission,making Engine working speed that needed by rotor working speed avoiding the speed corresponding to the resonant frequency,making the frequency of the engine's excitation avoiding the natural frequency of the frame;Second option is optimizing the design frame structure,avoiding the occurrence of frame resonance.