LIN Huan,XU Linyun*,XUAN Yan,et al.Modal analysis and experimental study of the multistage Y-type ginkgo tree using the finite element method[J].Journal of Forestry Engineering,2020,5(01):148-155.[doi:10.13360/j.issn.2096-1359.201903032]





Modal analysis and experimental study of the multistage Y-type ginkgo tree using the finite element method
1.常州信息职业技术学院智能装备学院,江苏 常州 213164; 2.南京林业大学机械电子工程学院,南京 210037
LIN Huan1 XU Linyun2* XUAN Yan2 ZHOU Jie2 LIU Guanhua2 CHEN Qing2
1. Department of Intelligent Equipment, Changzhou College of Information Technology, Changzhou 213164, Jiangsu, China; 2. College of Mechanical and Electronic Engineering, Nanjing Forestry University, Nanjing 210037, China
模态频率 有限元分析 激光扫描 三维重建 银杏树 林果采收
modal frequency finite element analysis laser scanning 3D reconstruction ginkgo tree harvest fruits
机械振动采收是林果采收目前最有效的方式,研究林果树的固有动力学特性能够为果树在振动采收过程中激振器激振参数的选择提供依据。利用移动二维激光扫描技术获取多级Y型银杏树的点云数据,通过点云数据的处理重建树木的三维模型并采用Creo进行实体化处理,使用ANSYS对银杏树进行有限元分析并与测试结果进行对比验证。结果表明:主干和分枝之间存在一定的运动独立性,随着侧枝的分级细化会出现除主干谐振频率点以外更多的谐振频率。在有限元分析条件下银杏树的各阶谐振频率均成对出现,在同一阶模态中,仅有一个或几个树枝能够同时出现显著的振动现象,并且最大变形位置均出现在树枝末梢,以某个特定频率对银杏树进行激振并不能引起所有树枝的振动。有限元分析与试验测试结果之间的最大相对误差在低于15 Hz的低频区和高于15 Hz的高频区分别为10.40%和6.75%,有限元方法可以有效地分析果树的动力学特性。
China is the world's leading producer of fruits. Due to various shapes and sizes of fruits, the harvesting of fruit is time-consuming and laborious. At the same time, the harvesting season is heavy-duty, the harvesting time is relatively concentrated, and the labor cost is high. Mechanical vibration harvesting is the most effective method to harvest fruits. The principle of the vibration harvesting is to stimulate the fruit tree by a certain form of vibration mechanism, so that the fruits are separated from the branch. The investigation of the inherent dynamics of forest fruit trees could provide the basis for the selection of excitation parameters during the vibration harvesting. In this paper, the point cloud data of the multistage Y-shaped ginkgo tree was obtained by the moving two-dimensional laser scanning technology. The three-dimensional model of tree was reconstructed by the point cloud data processing and was materialized by Creo. The finite element analysis of ginkgo tree was carried out by ANSYS and compared with the test results. The results showed that there was a certain degree of motion independence between the trunk and the branches. With the grading and thinning of the side branches, besides the main resonance frequency points, more resonance frequencies appeared. Under the condition of finite element analysis, all the resonant frequencies of the ginkgo tree appeared in pairs. In the same mode, only one or several branches could simultaneously achieve significant vibration phenomena. And the maximum deformation position appeared at the tip of branches. When the ginkgo tree was excited at a specific frequency, the vibration of all branches couldn't be simultaneously stimulated. The maximum relative error between the results of the finite element analysis and the test results was 10.40% and 6.75%, respectively, at the low frequency region below 15 Hz and high frequency region above 15 Hz. The method of finite element could be used to effectively analyze the dynamic characteristics of fruit trees.


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收稿日期:2019-03-27 修回日期:2019-05-24
基金项目:江苏省高等学校自然科学研究项目资助(19KJB210007); 常州市应用基础研究计划(CJ20190023); 常州信息职业技术学院科研课题青年基金资助(CXZK201804Q); 常州信息职业技术学院科研平台资助(PYPT201804G); 常州高技术重点实验室项目(CM20183004)。
作者简介:林欢,女,研究方向为现代机械设计理论与方法。通信作者:许林云,女,教授。E-mail: lyxu@njfu.co
更新日期/Last Update: 2019-12-10