基于有限元瞬态结构仿真的嫁接夹渐进式上夹方法

Gradual Clamping Method for Grafting Clips Based on Transient Structural Finite Element Simulation

摘要:

自动上夹是机械嫁接过程中的关键环节。针对目前瓜类嫁接夹力学参数不明确、夹子瞬间释放易对幼嫩苗茎造成冲击损伤的问题，本文通过有限元瞬态结构仿真模拟自动上夹全过程，分析嫁接夹动态力学特性，明确了嫁接夹结构参数对苗茎夹持过程中瞬时冲击力及稳定夹持力的影响规律。构建了以不同钢圈直径下嫁接夹夹臂完全闭合时的夹口位移、夹口张开角度为结构参数，以瞬时夹持力和稳定夹持力为评价指标的五因素数学模型，实现了对任意苗茎直径条件下夹持力的理论计算。依托自主研制的嫁接机及其渐进式上夹机构，进行了嫁接夹指定角度渐进式释放与传统夹口张至最大瞬间释放两种方式对比试验。结果表明，在嫁接夹指定角度渐进式释放过程中，当钢圈直径为0.7mm时，嫁接苗表面瞬时冲击力为5.29N，小于接穗安全压缩力，上夹成功率达94%，苗茎表面未出现明显机械损伤，满足机械嫁接上夹环节对安全性和稳定性的要求。研究结果可为嫁接机器人自动上夹机构设计与优化提供理论支撑和参考依据。

Abstract:

Automatic clamping is a critical step in mechanical grafting processes. To address the issues of unclear mechanical parameters of grafting clips for cucurbits and the potential impact damage caused to tender seedlings by instantaneous release, the complete clamping process was simulated by using transient structural finite element analysis. The dynamic mechanical characteristics of the grafting clip were analyzed to clarify how structural parameters affected the instantaneous impact force and stable clamping force on seedling stems during the clamping operation. A mathematical model with five factors was developed, using the clamp mouth displacement and opening angle at full closure of the grafting clip arms under varying steel ring diameters as structural parameters, and instantaneous and stable clamping forces as evaluation criteria. This enabled the theoretical calculation of clamping force for seedlings of arbitrary diameters. Utilizing a self-developed grafting machine with a progressive clamping mechanism, comparative experiments were conducted between gradual-release clamping at specified angles and traditional instantaneous release at maximum opening. Results showed that during the gradual-release clamping process at a specified angle, when the steel ring diameter was 0.7 mm, the instantaneous impact force on the seedling surface was 5.29N, below the safe compression limit for scions. This resulted in a 94% successful clamping rate without significant mechanical damage to seedling surfaces, thus satisfying safety and stability requirements for mechanical grafting clamping. The research result can provide theoretical support and references for the design and optimization of automated clamping mechanisms in grafting robots.