基于多激励振动与能量传递的蓝莓采摘力建模与采摘机理研究

Blueberries have excellent sanitarian and medicinal value and are in the condition of demand exceeds supply, therefore,automatic picking are urgent need to expand planting area.Efficient and safe automatic picking and holding greenfruit and leaves are guaranteed by vibration.Separation of ripe fruit from branches under vibrational excitation is the key to picking and the basis of the design of automatic picking machine. When the blueberry bushes act by multi-incentive vibration from the harvester, forced vibration and self-excited vibration coexist, direct vibration and indirect vibration overlap, the single branch is not only transferring but also consuming the vibration energy, so the vibration force field is time-varying. This research is on shrub without main trunk at the time of multi-excitation stacking.The stress field of the bush and stacking of viration will be researched. The main and side branches are simplified to variable cross-section continuous vibration elastomer,and their physical vibration model and mathematical vibration model are established. The influence factors about the modulus of elasticity, shear modulus and poisson's ratio of the main and side branches are determined and analysed.The effective masses and their virtual positions of the crown ,branch ,root and soil mass under the vibration are confirmed, thus the rate of damping and energy consumption are determined on the basis of outline and size of the plant. According to the picking force of the ripe fruit, green fruit and leaves measured, the optimal vibration excitation frequency, amplitude, the initial phase angle, distance and quantity of excitation will be got, and the numerical simulation will be executed. The mechanism of vibration picking , which provides the theoretical basis for designing picking organization will be revealed, therefore, the automatic harvester which only ripe fruit could be picking out will come true.

蓝莓小浆果具有卓越的保健与药用价值，供不应求，目前人工采摘是蓝莓产业链发展的瓶颈，迫切需要自动采摘来扩大种植面积。而植株在振动激励下产生离心力使果、枝分离是采摘的关键，也是设计自动采摘机的核心与依据。无主干蓝莓灌木受自动采摘机多激励振动时，受迫振动和自激振动共存，直接振动和间接振动叠加，单枝既是振动能量的产生源和传递结构，又是能量的消耗体，因此振动力场是时变的。将主侧枝简化为变截面柔性体，测定和分析主侧枝弹性模量、剪切模量、泊松比等影响因素；确立多点激励下冠、根部振动和能耗物理模型，确定蓝莓灌木冠部、枝干及根部阻尼及能量消耗比；研究振动能量传递和消耗规律，建立主侧枝振动采摘力的物理模型和数学模型；根据实测的熟果、生果和树叶的采摘力范围，求得振动激励的频率、幅值、初始相位角、激励间距和数量等参数的最优解，并进行数值模拟；揭示蓝莓振动采摘机理，为采摘机设计提供理论基础，实现摘熟留青的自动采摘。

近年来，我国蓝莓产业发展迅速。目前，我国蓝莓的收获通常采用人工作业，蓝莓果实每年6-8月成熟，因蓝莓果实呈酸性，且蓝莓果实成熟期邻近雨季、成熟期短，需投入大量的人力进行蓝莓果实采收。据统计资料显示，每年因采收不及时造成了巨大的资源浪费和经济损失。研究蓝莓植株与果实生长机理，建立与完善蓝莓果实采摘理论，研制和推广蓝莓采摘机，对发展蓝莓产业、实现蓝莓果实收获现代化和自动化具有重要的意义。.建立蓝莓植株生长振动模型，采用超几何函数作为核函数对振动模型进行解算得到蓝莓植株的主振型、正则振型和杜哈梅积分式；采用多柔体大范围弹性变形理论求解采摘机与蓝莓植株相互作用时采摘碰撞力，并对采摘过程中的蓝莓植株振动形态进行分类；利用已求解得到的采摘碰撞力和杜哈梅积分式求解，得出蓝莓植株每类振动的振动输出响应和蓝莓果实振动采摘力；分析蓝莓采摘工作条件和蓝莓植株振动能耗，基于ANSYS软件建立蓝莓植株柔性体、基于ADAMS软件建立采摘机刚性体，在ADAMS下对采摘机和蓝莓植株进行刚柔耦合动力学分析以研究蓝莓振动采摘过程，为探索和完善蓝莓采摘振动机理奠定基础。.分析蓝莓植株与土壤相互作用能量损耗，分析理想状态下、自然条件下和采摘装置作用下的蓝莓植株生长形态并建立力学模型；采用 “静变形法”求解得到蓝莓植株与土壤之间相互作用的等效刚度，依据“动能守恒”的思想求解得到蓝莓植株等效质量，利用“衰减系数法”求解得到土壤作用的等效阻尼；建立起采摘机、蓝莓植株、土壤三者相互作用的等效力学模型，求解得到蓝莓植株与土壤相互作用振动能耗，完善蓝莓采摘振动理论。.通过对试验的观察与数据分析，验证了所建立的模型合理，假设条件与计算方法合理，所建立的基于刚柔耦合动力学分析的采摘理论合理；对实验数据进行分析处理，得到采摘机最佳工作参数，为采摘机工作参数的选择提供理论指导。