条状组培苗负压拾取手设计与试验

目前,组培苗移植设备中针对组培苗抓取主要采用尺寸定位方式夹持,夹持手结构复杂,占用空间大,且对幼嫩的组培苗会有一定的损伤,影响后期成活率。为克服以上问题,该研究设计了一基于负压吸附的力定位单株条状组培苗拾取手,并对负压拾取手吸嘴内腔体,吸嘴材料及吸嘴口尺寸进行了设计。该论文对吸嘴内腔体形式采用CFD(computational fluid dynamic)软件进行了仿真分析,并通过拾取对比试验验证,确定吸嘴内腔体采用变形腔体结构为宜;对吸嘴材料及吸嘴口尺寸进行正交试验、单因素试验及交互作用试验,试验结果表明在组培苗吸嘴采用厚度为0.5 mm,内径为6 mm硅胶管,吸嘴口处长圆形半径为0.7 mm,吸嘴口唇高为1.5 mm的组合下,拾取手吸嘴对苗径在1.2~2.0 mm范围内的单株条状组培苗拾取效果稳定。在较优组合条件下,整体性能试验证明组培苗负压拾取手拾取系统吸附成功率可达到98%,能够满足下一步的移植插入作业要求。

Design and experiment on vacuum pickup hand for banding tissue culture seedlings

Abstract: At present, dimension-positioning method is adopted as the main method for grasping tissue culture seedlings in tissue culture transplanting equipments. But the majority of gripper structure based on dimension-positioning is complex, which causes that the precision of the operation can not be improved. Meanwhile, young tissue culture seedlings will certain be damaged by the gripper in the process of clipping , which affects the survival rate of the transplanted tissue culture seedlings. To solve such problems, this study designed a force-positioning pickup system based on vacuum adsorption, which can transplant banding tissue culture seedlings. The pickup system for tissue culture seedlings mainly consists of three parts, including vacuum production part, negative pressure detection part and the suction nozzle part. The suction nozzle part is the key part, which decides the holding effect of tissue culture seedlings. The core of suction nozzle is inner soft tube made of silicone rubber with a metal shaping pipe sleeved outside. To increasing the adsorption area, the suction nozzle lip is shaped as oblong. In this paper, design and experiments are both mainly focused on the structure and parameter of suction nozzle. The process that suction nozzle picks up a tissue culture seedling can be divided into two phases: adsorption phase and holding phase. In adsorption phase, negative pressure flow field in the suction nozzle, which is generated by the vacuum generator, will help the seedling overcome its gravity, so that the seedling can be absorbed and adhered to the suction nozzle lip closely. In holding phase, the suction nozzle lip and the stem of tissue culture seedling joint closely, and a vacuum cavity emerges with less leakage in the suction nozzle, then the vacuum cavity generates the force for holding the tissue culture seedling. In adsorption phase, there are two schemes about negative pressure inner cavity of suction nozzle, and they are deformed cavity and parallel cavity. To get the average velocity of flow field near suction nozzle lip, simulation analysis have been carried out based on each of the two cavity with CFD (computational fluid dynamic) software in adsorption phase. The corresponding verification test also have been done, and the results supported that deformed cavity will be used in the pickup hand system because the suction nozzle using deformed cavity can produce flow field with higher velocity, and hold tissue culture seedling more steadily. In holding phase, a series of orthogonal experiment, single factor experiment and interaction experiment were carried out, to test the impact factor about tissue culture seedling holding strength, including thickness of suction nozzle tube, diameter of suction nozzle tube, radius of oblong suction nozzle lip and height of suction nozzle lip. The experiments results show that the optimum parameters for the tissue culture seedlings of suction nozzle are 0.5 mm thickness of suction nozzle tube, 6 mm diameter of suction nozzle tube, 0.7 mm radius of oblong suction nozzle lip and 1.5 mm height of oblong suction nozzle lip in experiments. With these optimum impact factors, suction nozzle can hold banding tissue culture seedlings steadily whose diameters range from 1.2 to 2 mm. It is noteworthy that overall success rate of negative pressure pickup system for banding tissue culture seedling can reach up to 98%, which successfully meets the requirements of insertion in next operation for transplantation.