| 基于有限元方法的整形果树振动收获机理分析 |
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| 引用本文： | 王冬,陈度,王书茂,陈志,张锋.基于有限元方法的整形果树振动收获机理分析[J].农业工程学报,2017,33(Z1):56-62. |
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| 作者姓名： | 王冬 陈度 王书茂 陈志 张锋 |
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| 作者单位： | 1. 中国农业大学工学院,北京,100083;2. 中国农业大学工学院,北京 100083;现代农业装备优化设计北京市重点实验室,北京 100083;3. 中国机械工业集团,北京,100080 |
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| 基金项目： | 国家自然科学基金资助项目（51305445）；北京市科委项目（Z151100001615017） |
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| 摘 要： | 为提升振动式采收机械的设计效率,该文在分析常见振动收获机工作机理的基础上,建立了3种典型整形果树实体模型,利用有限元方法得到其在1~50 Hz低频范围内的固有频率和模态振型,并进行了振动响应特性仿真试验。结果表明,整形果树固有频率和模态振型受果树形态影响较大,3种典型整形果树的低阶固有频率主要集中在7~11阶范围,分别在13.5、12.0和7.5 Hz时振动响应最为剧烈,且一致性较好;同时,不同加载方式对于整形果树振动响应特性具有较大影响,其中双体多向加载较为适合于纺锤形果树,而单体回旋型加载则更适合于自然开心型和直立平面形果树。该方法可为不同类型整形果树振动式收获机械的设计提供参考。
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| 关 键 词： | 有限元方法 收获 振动 果树 振动响应 模态分析 |
| 收稿时间： | 2016/8/8 0:00:00 |
| 修稿时间： | 2016/12/30 0:00:00 |
Analysis on vibratory harvesting mechanism for trained fruit tree based on finite element method |
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| Wang Dong,Chen Du,Wang Shumao,Chen Zhi and Zhang Feng.Analysis on vibratory harvesting mechanism for trained fruit tree based on finite element method[J].Transactions of the Chinese Society of Agricultural Engineering,2017,33(Z1):56-62. |
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| Authors: | Wang Dong Chen Du Wang Shumao Chen Zhi and Zhang Feng |
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| Institution: | 1. College of Engineering, China Agricultural University, Beijing 100083, China;,1. College of Engineering, China Agricultural University, Beijing 100083, China; 2. Beijing Key Laboratory of Optimized Design for Modern Agricultural Equipment, Beijing 100083, China;,1. College of Engineering, China Agricultural University, Beijing 100083, China; 2. Beijing Key Laboratory of Optimized Design for Modern Agricultural Equipment, Beijing 100083, China;,3. China National Machinery Industry Corporation, Beijing 100080, China; and 1. College of Engineering, China Agricultural University, Beijing 100083, China; |
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| Abstract: | Abstract: Currently, mass shake-and-catch tree fruit harvesting approach could cause fruit detachment efficiency in low level. Tree structure plays an important role in both harvest efficiency and machine performance for tree fruit. To obtain better harvest efficiency, it is important to optimize the machine parameters and provide proper excitation to the trees according to their growth morphology. This paper presented a finite element modeling method for the trained tree dynamic response study in relation to shaker type. Firstly, mathematic models of 3 types of shakers, including reciprocal shaker, orbital shaker and multidirectional shaker, were built, which were further used to analyze the basic working principles of these shakers. The basic principle of developed shaking models was analyzed according to their characteristics. In order to study the influence of different shakers on the dynamic response of trained tree, 3 training structures i.e. spindle, open center and vertical plane were selected. Their 3D (three-dimensional) physical models including trunk and secondary limbs were constructed in Pro/Engineer. Other elements, such as leaves and twigs, were removed from the model. Then, these models were imported into ANSYS software to analyze their modal shapes. The modal shape and resonance frequency were obtained in a frequency range of 1-50 Hz. Results showed that the resonance frequency and modal shape were influenced by the growth morphology of trees. Three types of trained tree model (spindle, open center and vertical plane) could obtain ideal response at the 10th, 14th, and 19th phase respectively. For the developed trained tree model, the natural frequency range was mainly contained from 7.0 to 20.0 Hz, corresponding to 420-1200 r/min of mechanical shaker. As having thick tree truck, the initial mode frequency of spindle-shape tree was greater than the other 2 types. To further study the dynamic response of the developed tree models, harmonic response simulation was conducted with 3 types of excitation patterns. For the spindle-shape tree, 3 excitations could all induce violent vibration at far-end of the limb (i.e. NODE4 and NODE5). Simulation results showed that multidirectional excitation could cause a relatively ideal response at 13.5 Hz (10th phase) for spindle-shape tree model. Multidirectional excitation could also induce the most violent response among the 3 methods and obtain the maximum displacement at featured location up to 1.844 m. Orbital excitation with 12.0 Hz (11st phase) could cause evident response with the maximum displacement of 2.485 m, and also provide relatively uniform response for open center tree model. However, a small part of area could only achieve a relatively low vibration response, as a portion of vibration energy was absorbed by the tree crotch. To obtain higher detachment efficiency, shaking from different directions would increase the machine performance for this type of trained tree. For vertical plane tree model, both reciprocal and orbital shaker could cause superior response considering mechanical harvest. Results obtained from field experiment validated the correctness of simulation results. The illustration method including modal analysis and harmonic response simulation, could be useful for new mechanical shaker design for trained fruit tree harvest. |
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| Keywords: | finite element method harvesting vibrations fruit tree vibratory response modal analysis |
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