Experimental And Theoretical Research On Vibration Characteristics Of Ginkgo Tree Based On Crown Characteristics

With the continuous development of China’s forest fruit industry,forest fruit output continues to rise.Problems such as insufficient harvesting capacity during forest fruit harvest and high labor cost for forest fruit harvest have been exposed.Existing research shows that the use of mechanical vibration recovery is an effective way to improve recovery efficiency and reduce production costs.Many scholars have conducted field trials and research results have shown that changing the tree structure of fruit trees can improve the mechanical recovery efficiency.In this paper,the ginkgo tree is used as the test object to study the influence of the crown structure,leaves and fruits on the vibration characteristics of fruit trees.The research process is divided into indoor test and outdoor verification test.The indoor test uses transient impact method to obtain spectral characteristics of single-axis branched ginkgo tree and Y-shaped axis-shaped ginkgo tree with fruit-leaf,fruitless-leaf and fruitless-leafless three state.By comparing the distribution characteristics of the resonance peak amplitude,natural frequency and natural frequency quantity of the two crown-shaped ginkgo treesspectrum curves in different states,the influence law of the crown structure on the spectrum curve of the ginkgo tree is summarized.We also summarize the influence of leaves and fruits on the spectrum characteristics of ginkgo trees with different crown structures.To conform the indoor test resluts,we select outdoor fruit trees to experiment.The test results show that the natural frequency consistency of the different branches of the Y-shaped branched fruit tree is better than that of the single-axis branched ginkgo tree;The leaves have obvious damping effects in the vibration of the single-axis branched ginkgo tree,but have little effect on tthe Y-shaped branched trees;The fruit mainly reflects the mass effect during the vibration process,and its damping effect is very small.This paper proposes a method for constructing vibration models of fruited and leafy fruit trees.The accuracy of the fruit tree model has been experimentally verified.The method combines laser scanning and finite element method.Using Point Cloud Information gotten from laser scanning device extracts the skeleton points and the radius of the branch to construct a spatial finite element model of fruitless and leafless fruit trees.Through the statistical analysis of the distribution of fruits and leaves on fruit trees,the distribution rules of fruits and leaves on fruit trees are determined.The fruit mass and leaf quality are added to the model nodes to construct a spatial vibration theory model of fruit trees with leaves.The verification test results show that: the calculated natural frequency is more than the measured natural frequency;But the measured natural frequency can find very similar values in the simulated frequency;The amplitude of each branch of the fruit tree of the simulated model is the same as the measured acceleration response amplitudes of the branches;The maximum relative error of the calculated model is 5.76%.Using the eigenvectors calculated by the simulation model,the energy method is used to study the energy distribution of each branch of the fruit tree under different vibrations.The vibration energy distribution of the whole fruit tree was used to select the vibration harvesting frequency of the fruit tree.The results can reflect the actual vibration response of fruit trees to a certain extent.In order to apply the fruit tree model described in this article to practical vibration applications,this paper designed a small orchard harvesting machine that integrates point cloud information collection and vibration harvesting.The finite element analysis was used to analyze the stress and deformation of the vibration device and the modal analysis to verify the rationality of the whole structure.