Research On The Vibration Harvesting Exciter For Forest Fruit Based On Two Dimensional Excitation

With the rapid development of the economy and the continuous optimization of the agricultural industrial structure,the forest and fruit industry has gradually become the leading industry and important pillar industry for fruit farmers to increase their income and become rich,and also an industry that pays equal attention to ecological and economic benefits.It has strong international competitiveness and broad prospects for development.After analyzing the research status at home and abroad and combining with the requirements of the tree trunk holding and shaking two-dimensional excitation harvesting,this paper designs a vibration exciter that can output two-dimensional excitation.Design the overall scheme of the vibration exciter and complete the calculation and selection;The structural design and theoretical analysis of the key excitation components are carried out.Based on multi-body dynamics and finite element method,the vibration exciter-fruit tree system is simulated and analyzed to optimize its working parameter combination;After the trial production of the prototype,the field test was carried out to verify the working reliability of the vibration exciter and the effectiveness of the binary excitation to optimize the vibration response of the fruit tree.The main research contents and conclusions are as follows:（1）Overall scheme design of two-dimensional excitation type forest fruit vibration exciter.According to the actual operation requirements of the trunk holding type of forest and fruit and the production conditions of the two-dimensional Lissajou image,the design requirements of the two-dimensional excitation type vibration exciter are clarified.Compared with the crank slider mechanism,the cam structure and the eccentric block mechanism that are mainly used at present,the vibration generating mechanism and the eccentric block mechanism are determined according to the design requirements,and the simplicity of the vibration exciter design is guaranteed through calculation,Semi-circular eccentric block is determined as the type of eccentric block in this study.Determine the overall scheme of the vibration exciter,which is mainly composed of power components,transmission system,vibration mechanism,etc.According to the scheme,establish the dynamic model of the output excitation of the vibration exciter,and determine the key factors affecting the output excitation of the vibration exciter through the model derivation and solution,specifically the equivalent mass M2 of the single-shaft eccentric block and the single-shaft speedω₂ and eccentricity r only determine the overall amplitude of the output excitation force,while the mass ratio of the two shaftsμ、Two-shaft speed ratioξAnd initial phase difference of two axesψThree parameters determine the form of output excitation.（2）Analysis of influencing factors affecting two-dimensional excitation output.In order to obtain the rule of the influence of parameters on the output excitation of the exciter,this paper uses Matlab language to develop the output excitation visualization applet in the APP Designer module based on the Matlab2022 platform.Through comparison and verification,it is found that the applet can achieve the expected function.Using this small program to carry out single factor analysis of each parameter,it is found that:1)with the mass ratio of two axlesμwith the increase of the value,the ratio of the long axis to the short axis of the excitation image output by the exciter becomes larger and larger.At this time,the Lissajous image of two-dimensional excitation is closer to"circle",but the decline rate of eccentricity will also decrease;2)When the speed ratio of two shaftsξwith the increase of,the"petal number"of the output excitation Lissajou image will also increase,and the maximum number of intersection points of the line segment intersection image will also increase,and the overall amplitude of the image will also increase.However,if it is increased to a certain amount,the periphery of the curve will become dense,and the whole image is very close to a circle;3)With initial phase differenceψthe amplitude and shape of the output excitation Lissajou image will not change,but will rotate along the center of the image to change its vibration direction.The influence of parameters on the output excitation of the exciter is obtained.（3）Determination of optimal excitation parameters based on resonance frequency.According to the mechanical characteristics of fruit trees in vibration harvesting,a dynamic model of fruit trees under two-dimensional excitation is established based on the Euler-Bernoulli beam model,and the key factors affecting the vibration response of fruit trees are obtained by solving the model.Then establish the finite element model of fruit tree,and use Comsol 16.0 software to carry out modal analysis and harmonic response analysis on the finite element model.The results show that the changes of fruit tree under different excitation frequencies are not the same,but they are basically manifested as the torsion and bending of branches while the vibration response of the trunk part is not large,and when the excitation frequency is 23 Hz,the acceleration response of each measuring point around the crown is large and the displacement response is small,which can achieve good shaking effect.The rigid-flexible coupling simulation model of the fruit tree-vibration exciter is established,and the orthogonal simulation test is carried out.The key parameter combination is optimized by taking the maximum acceleration dispersion coefficient of each measuring point around the tree crown as the index to obtain the bestμis 5.3,ξis 3.0,ψis 148.5°.（4）Design of two-dimensional exciting vibration exciter.According to the actual working conditions and excitation requirements of the operation,carry out theoretical calculation of key components,determine the size parameters,and check their strength.The maximum stress of eccentric block and transmission main shaft are 0.6Mpa and40Mpa respectively,and the maximum strain is 0.014mm and 0.07mm respectively,which meet the operation requirements and design requirements.At the same time,carry out modal analysis of the two parts to confirm that resonance will not occur under their working conditions,Determine the operation stability of the key stressed parts,and complete the overall hardware design of the vibration exciter according to the assembly requirements;According to the operation requirements and adjustment parameters of the vibration exciter,the overall scheme design of the control module is carried out,（5）Trial production and verification test of two-dimensional excitation type vibration exciter.The determination of the size chain of the entire two-dimensional excitation exciter was improved,and on this basis,the trial production and assembly of the exciter were completed.A fruit tree vibration response testing platform has been built,which can achieve functions such as adjusting excitation input parameters,issuing excitation start and stop commands,and obtaining acceleration data during the excitation process through remote control.Based on this platform,validation experiments of the exciter have been carried out.The experimental results show that:1)This type of exciter can achieve the function of outputting predetermined excitation forms by changing parameters.2)Under the optimal excitation parameter combination,the discrete coefficient of the maximum acceleration at each measurement point on the tree crown is0.301,which is smaller than the other two excitation forms,but slightly larger than the theoretical value,with a relative error of 6.64%,verifying the accuracy of the optimization results.