穴盘幼苗机械手取苗基质完整率影响因素试验与分析

当前国内外移栽机械研究中取苗环节是制约自动移栽机发展的瓶颈,该文试验研究重点是判别拟定的影响因素对穴盘幼苗机械手取苗影响显著与否。测试的影响因素为基质含水率(35%~65%),取苗执行器的执行结构外形特征(指针形状、压舌板形状、U型形状3种)和作物生长初期幼苗根系对基质抗剪性能提升的效果,并将基质完整率作为试验指标值。通过试验给出夹持力与夹持量的对应关系,明确了各取苗执行器执行结构的最佳夹持量,采用正交试验法得出主次影响因素和优水平。试验结果表明:执行结构外形特征是主要影响因素,并确定U型形状为最佳;基质含水率对取苗结果有一定影响,含水率在50%左右为最佳;在幼苗长出第1对真叶时取苗,幼苗根系对基质抗剪性能提升的效果对取苗影响不大,对最优水平组合做验证试验基质完整率均在80%以上,样本全都成功移栽到营养钵内。该文为进一步研究和改善穴盘幼苗移栽设备的关键技术点提供参考。

Experiment and analysis of impact factors for soil matrix intact rate of manipulator for picking-up plug seedlings

Abstract: At present, in the research of transplanting machinery domestic and abroad, the link of pick-up plug seedlings is the bottleneck restricting the development of automatic transplanting machines. This research of test is focused on identifying whether the proposed influencing factors changes have significant impact on the soil matrix intact rate of manipulator pick-up plug seedlings. Tested influencing factors include 3 parts, i.e. soil moisture content, shape features of manipulator structures of pick-up plug seedlings and performance improvement of root system on soil matrix shear strength in the seedling stage. Among them, soil moisture content is from 35% to 65%, and water is mixed with the soil matrix to fill the matrix pore, which increases matrix compressive ability and improves the viscosity of soil inside, at the same time also affects the adhesion force between soil matrix and plug wall. Shape features of manipulator structures of pick-up plug seedlings contain finger-shaped, tongue-shaped and u-shaped, and with these 3 shapes the manipulator contacts with the soil matrix using contact type of line, plane, and closed profile line respectively. Research shows that the root system on soil matrix weaving, winding, reticular surround and twisting force between root system and matrix particles have a significant influence on soil shear strength. In this paper, the performance improvement of root system on soil matrix shear strength is tested in the seedling stage. And the soil matrix intact rate of seedlings is taken as test index. Through the test, the change rule that compression degree determines the compression quantity of pick-up plug seedlings manipulators with different structures is as follows: The force applied on soil matrix by finger-shaped manipulator is concentrated on a few lines, and there is strong pressure on the soil matrix under the same drawing force, so it has a big compression quantity and a big clamping quantity; The tongue-shaped has a large area and weak pressure on the soil matrix, so it needs a small clamping quantity; The U-shaped is also linear contact, but because its lower end is closed, which plays a role of holding up in the process of ascension, the clamping quantity is also small. At the same time, the compression quantity is reduced with the moisture content. Our test adopts the orthogonal experiment design, and chooses L9(34) orthogonal table; with the soil matrix intact rate of seedling as test index, through the analysis of variance and range, we obtain the primary and secondary influencing factors which affect pick-up plug seedlings, and also obtain the optimal level. Meanwhile, the causes are analyzed and a better environment in pick-up plug seedlings is proposed. The results of test show that the shape feature of manipulator structures of pick-up plug seedlings is the primary factor which obviously influences the effect of pick-up plug seedlings manipulator and determines the u-shaped structure is the best. For the moisture content, around 50% is the best. When the first pair of leaves of the seedlings grow up to pick-up plug seedlings, the performance improvement of root system on soil matrix shear strength in the seedling stage has little effect on soil reinforcement. The verification test is carried out, and the results show when the soil moisture content is 50%, the u-shaped manipulator of pick-up plug seedling can make the soil intact rate of seedling all above 80% and seedlings survival quickly, which proves that the selected factors' levels are reasonable. This test determines the key technical points for further study and improving the equipment of pick-up plug seedlings, so it establishes the important theoretical basis for exploring automatic transplanting for pick-up plug seedlings.