核桃组合式主干柔性夹持振动采摘臂设计与试验

Design and Test of Combined Main Stem Flexible Clamping Vibratory Picking Arm for Walnuts

摘要:

针对当前平板式夹持机构因封闭性差、夹持力与主干直径不匹配，造成落果率低和树皮易损伤等问题，本文设计了一种"夹持力可控、平板定夹与浮动V形动夹"的组合式主干柔性夹持振动采摘臂。基于自走式振动采摘机作业原理，对采摘臂激振机构和夹持机构等关键部件进行设计，通过单因素柔性夹持振动采摘试验，确定柔性垫块为硬度60 HD和宽度11 cm的硅胶材质。通过建立核桃枝条-果柄-果实动力学模型和果实脱落理论条件，得到影响核桃振动脱落的主要因素为核桃自身性质、激振频率、夹持高度和激振时间。以落果率和含水率变化率开展三因素三水平正交组合核桃果园振动采摘试验。试验结果表明，安装组合式主干柔性夹持振动采摘臂的核桃采摘机，面向主干直径为[14,17) cm的核桃树振动采摘最佳作业参数为激振频率25 Hz、夹持高度110 cm、激振时间20 s。在最佳作业参数下开展组合式与平板式对比试验，试验结果表明，组合式落果率、树皮擦伤率和撕裂率分别为91.70%±0.74%、5%和0%，相较平板式落果率提升5.11个百分点、树皮擦伤率和撕裂率分别下降10个百分点和5个百分点，有效提升自走式核桃采摘机作业性能。

Abstract:

Aiming at the problems of low fruit drop rate and easy bark damage caused by the current flat plate clamping mechanism due to poor closure and mismatch between clamping force and trunk diameter, a combined trunk flexible clamping vibratory picking arm with controllable clamping force, flat plate fixed clamping and floating V-type movable clamping was designed.Based on the operating principle of the self-propelled vibratory picker, key components such as the excitation mechanism and clamping mechanism of the picking arm were designed, and through the one-factor flexible clamping vibratory picking test, it was determined that the flexible cushion was made of silica gel with a hardness of 60 HD and a width of 11 cm.Through the establishment of walnut branch-stalk-fruit kinetic model and theoretical conditions of fruit drop, the main factors affecting the vibration drop of walnuts were obtained as the nature of the walnuts themselves, the excitation frequency, clamping height and excitation time.The three-factor and three-level orthogonal combination walnut orchard vibration picking test was carried out with the fruit drop rate and moisture change rate, and the test results showed that the optimal operating parameters of the walnut picker installed with the combined trunk flexible clamping vibration picking arm, facing the walnut tree with the trunk diameter of [14,17) cm, were excitation frequency of 25 Hz, clamping height of 110 cm, and the excitation time of 20 s.Under the optimal operating parameters, a comparison test between the combined type and the flatbed type was conducted, and the test results showed that the combined type dropped fruit rate, bark abrasion rate and tear rate were 91.70%±0.74%, 5% and 0%, respectively, compared with the flatbed type, the dropped fruit rate was increased by 5.11 percentage point, and the bark abrasion rate and tear rate was decreased by 10 percentage point and 5 percentage point, respectively, which effectively enhanced the operational performance of the self-propelled walnut picking machine.