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多子芋收获机柔性挡板式输送分离装置设计与试验

Design and experiment of the flexible baffle-type conveying and separating device for multiple taro harvesting machine

  • 摘要: 针对传统杆条式升运链输送多子芋时存在根土复合体翻滚回落、输送效率低和芋头破损率高的问题,该研究设计了一种柔性挡板式输送分离装置,通过分析柔性挡板对根土复合体的碰撞解聚特性与抛送作用,明确了影响输送分离性能的主要因素;采用离散元-有限元-多体动力学三元耦合方法(DEM-FEM-MBD)开展单因素仿真试验,结果表明柔性挡板可有效防止根土复合体翻滚回落,对芋头的最大冲击力较刚性挡板降低55.66%,结合根土复合体尺寸与输送稳定性需求,确定柔性挡板间距为300 mm,开展网格收敛性验证,确定柔性挡板网格尺寸为4 mm。通过Box-Behnken响应面台架试验,探究了输送筛面倾角、升运线速度和抖动轮频率对芋头平均输送时间与土壤筛分率的影响规律,经多目标优化得到最优参数组合为:输送筛面倾角18°、升运线速度0.62 m/s、抖动轮频率2 Hz时,土壤筛分率为88.76%,芋头输送时间为1.91 s,与回归模型预测值相对误差分别为0.15和2.10个百分点,耦合仿真试验与台架试验相对误差分别为0.20和3.08个百分点,验证了耦合模型的可靠性。田间验证结果显示,柔性挡板式输送分离装置土壤筛分率和输送成功率分别提升4.72和17.97个百分点,芋头破损率和收获损失率分别降低12.11和0.97个百分点,分离效果和收获质量均优于传统杆条式输送分离装置,满足多子芋输送分离作业要求。研究结果可为芋头等根茎类作物高效低损收获装备优化设计提供参考。

     

    Abstract: Taro is one of the three major export specialty aquatic vegetables in China (along with lotus root and water chestnut), and it plays an important role in promoting the national strategy of rural revitalization. However, currently, the harvesting process of taro mainly relies on manual labor, with the labor cost accounting for 40% to 50%. The technical difficulty lies in that taro grows in a wet and sticky soil environment, and during harvesting, the root system is entangled and adhered to the soil, forming a conical spherical root-soil composite structure, making it difficult to separate the taro from the soil. At the same time, the moisture content of taro during the harvesting period is as high as 73.70%, and it is prone to mechanical damage when subjected to impact. Therefore, exploring the root-stem soil separation technology and optimizing the separation mode of transportation is an important scientific issue that urgently needs to be solved in the current mechanized harvesting of taro. When transporting taro using the traditional rod-bar type lifting chain, there are problems such as the root-soil composite body rolling back and falling, low transportation efficiency, and high damage rate of taro. This study designed a flexible baffle-type transportation separation device. It is mainly composed of rods, rubber baffles, vibrating wheels, frames and chain drives. By analyzing the collision and disintegration characteristics and throwing effect of the flexible baffle on the root-soil composite body, the main factors affecting the transportation separation performance were identified as the height of the flexible baffle, the lifting line speed, the inclination angle of the screen surface, the vibration frequency and amplitude of the vibrating wheel. The coupling method of discrete element - finite element - multi-body dynamics (DEM-FEM-MBD) was used to analyze the influence laws of the height of the flexible baffle, the inclination angle of the conveying screen surface, the lifting line speed, the vibration frequency and amplitude on the average transportation time and soil screening rate of taro. Through single-factor simulation experiments, the results showed that the flexible baffle could effectively prevent the root-soil composite body from rolling back, and the maximum impact force of the flexible baffle on the taro was 55.66% lower than that of the rigid baffle. The flexible baffle spacing was determined to be 300mm. Grid convergence verification was carried out, and the mesh size of the flexible baffle was determined to be 4 mm.The relative error between the fitting curve and the physical experiment was 1.78%. Through the Box-Behnken response surface bench test, the influence laws of the transportation screen inclination angle, lifting line speed and vibrating wheel frequency on the average transportation time and soil screening rate of taro were explored. After multi-objective optimization, the optimal parameter combination was determined to be: a transportation screen inclination angle of 18°, a lifting line speed of 0.62 m/s, and a vibrating wheel frequency of 2 Hz. The soil screening rate was 88.76%, and the taro transportation time was 1.91 s. The relative errors of the two with the regression model predictions were 0.15 and 2.10 percentage points respectively. The relative errors between the coupled simulation tests and the bench tests were 0.20 and 3.08 percentage points respectively, which verified the reliability of the coupled model. Field verification results showed that the soil screening rate and transportation success rate of the flexible baffle-type transportation separation device were increased by 4.72 and 17.97 percentage points respectively, while the damage rate and harvest loss rate of taro were reduced by 12.11 and 0.97 percentage points. The separation effect and harvest quality were superior to those of the traditional rod-bar type transportation separation device, meeting the requirements of multi-sub-taro transportation separation operations. The research results can provide a reference for the optimization design of efficient and low-loss harvesting equipment for taro and other root and tuber crops.

     

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