基于有限元方法的沙棘果实振动采收机理研究

Lots of sea buckthorn (SB) was planted in the western region of China for ecological environment management. However, its economic value is far from development because the SB fruit is very difficult to be harvest, and thus, the enthusiasm of farmer to plant SB is affect deeply. Therefore, it is necessary to develop mechanical device for harvesting SB fruit. Nevertheless, current researches on designing and developing harvester of SB fruit are short in theoretical foundation and scientific basis. Thereby, this project is aim to study the mechanism on vibration harvesting of SB fruit and the methodology for designing vibration harvester. Firstly, the growth characteristics of the sea buckthorn and its fruit will be analyzed and the way how SB fruit being separated from the branch will be studied, for establishing the tree-machine and fruit-stem dynamics models. Then, the Lagrange theory will be introduced to study the mechanism of vibration harvesting on SB fruit. In that case, the key factor that affecting separation efficiency between SB fruit and branch can be identified. After that, the design methodology and factors of vibration harvesting system will be proposed by combining with resonance principle. Next, the finite element method will be used for simulation research of vibration harvesting. It is not only going to explore the various parameters on the effects of vibration harvesting, but also going to find out their interaction relationship through a combination of field trails. Besides, it will provide data support for the theory of model modification and improvement, and analyze the relationships between the key influencing factors and related physical parameters of SB tree and fruit, then establish its mathematical model. Finally, the mechanism on vibration harvesting of SB fruit and the methodology for designing vibration harvester will be clarified and developed. This project will provide the theoretical foundation and scientific basis for designing and developing vibration harvester of sea buckthorn fruit, increase the economical benefits of planting sea buckthorn by directly guide the practical production and improve harvesting efficiency, and finally to aid the improvement of the ecological environment in China.

为进行生态治理，我国在西部地区种植了大量的沙棘，但由于果实采收困难问题，经济价值远未得到开发而影响了种植积极性。针对沙棘采收设备的设计开发缺乏理论基础和科学依据的现状，本项目通过分析沙棘果实的生长特性和脱落特点，建立"果树-机械"和"果实-果柄"的收获系统动力学模型，引入拉格朗日动力学理论研究振动采收机理，从而确定影响果实与树枝分离效果的关键因素，进而结合共振原理提出振动采收系统的设计方法和设计要素；再利用有限元方法进行振动采收的仿真研究，结合实地试验，探索各参数对振动采收效果的影响及互作用关系，为模型修正和理论完善提供数据支持，并分析关键影响因素与相关果树物理指标的关系，以建立其数学模型，最终阐明沙棘果实的振动采收机理。本项目将为沙棘果实振动采收设备的设计和开发提供理论基础和科学依据，并可直接指导实际生产，提高采收效率，通过增加沙棘种植的经济效益，进一步改善我国日益恶化的生态环境。

为进行生态治理，我国在西部地区种植了大量的沙棘，但由于果实采收困难问题，经济价值远未得到开发而影响了种植积极性。针对沙棘采收设备的设计开发缺乏理论基础和科学依据的现状，本项目研究了沙棘果实的振动采收机理。具体内容和方法为：① 沙棘的力学特性与形态特征：测量常见沙棘的果柄-果实及果柄-树枝分离力，及其物料与几何特性等；② 沙棘果实-果柄系统仿真研究：研究沙棘果实与果柄脱离的振动采摘机理，建立双自由度受迫振动物理模型，采用数理微分方程求解沙棘果实-果柄系统稳态受迫振动输出解及采摘惯性力，应用贝塞尔函数曲线模拟果实的几何形状，利用Pro/E画出三维模型，导入ANSYS进行模态分析，研究沙棘果实-果柄系统的固有频率属性及影响因素；③ 沙棘果树的动力学仿真分析：通过Pro/E构造沙棘树的三维模型并导入ANSYS进行模态分析，研究其自然振动属性以及不同频率的振型，谐响应分析观察模型在正弦谐波载荷下的稳态响应，研究果树对不同正弦谐波载荷响应，分析不同位置加载时达到果实脱离所需的最小作用力以及频率范围；④ 沙棘果树-机械系统动力学研究：分析振动式收获机械的工作原理，提取主要力学特性，建立沙棘果树-机械系统的动力学模型，引入动力学理论分析系统特性，研究果树-机械系统在受迫振动过程中的响应特性及影响因素；⑤ 实验与仿真的对比：在固定位置施加振动，测量果树上不同部位的加速度响应，研究不同振动频率下果树的加速度响应特性，分析不同频率对振动传递的影响，开展果树-机械系统的有限元仿真分析，应用瞬态动力学方法在仿真系统中施加相同的作用力和频率，探索仿真结果与实验结果的相关性。研究结果表明影响果实振动脱落的关键因素为振动频率和振动位置，频率为20-30 Hz的载荷作用在主要枝干时，效果较好；有限元仿真模拟振动采收与试验的加速度响应相关性最高达0.8，通过有限元仿真的方法模拟果树的振动采收实验，部分解决田间实验的环境和时间限制等困难。