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烟草小苗移栽的挖穴作业阻力和土壤回流分析

Analysis of operation resistance and soil reflux during hole digging for tobacco seedling transplanting

  • 摘要: 为解决烟草小苗挖穴移栽过程中出现的穴形不理想、挖穴-移栽难协调、苗穴不同心等问题,对挖穴过程、挖穴作业阻力、挖穴土壤回流状况等进行了分析,实测了土壤物理参数,并对土壤参数进行标定。结果表明,土壤与挖穴铲的动、静摩擦系数和碰撞恢复系数分别为0.14、0.98和0.48。以土壤堆积角44.6°为目标对堆积角回归模型进行优化,与堆积角实测值最接近的1组解为土壤颗粒之间的表面能11.8 J/m2、恢复系数0.34、静摩擦系数0.56、动摩擦系数0.10。在该最优解下,堆积角仿真值为42.9°,与实测值相对误差为3.8%。基于离散元接触理论,构建了3种适应烟田土壤环境的挖穴铲-土壤相互作用仿真模型,并对挖穴过程进行计算机仿真,通过田间试验与计算机仿真结果的对比,确定了与实际相吻合的土槽模型。对土壤回流分析表明,在入土阶段土壤回流较少,该阶段的土壤回流率为4.77%;在出土阶段铲板对土壤的扰动较大,该阶段的土壤回流率为16.41%;整个挖穴过程的总体土壤回流率为8.66%。通过对挖穴阻力变化规律的分析发现,在运行0.7 s时出现阻力最大峰值,为411.3 N,挖穴过程中的最大功率为137.2 W。

     

    Abstract: To solve the problems of unsatisfactory hole shape, difficult coordination between hole digging and transplanting and decentration of holes during tobacco seedling transplanting, the process, operation resistance, and soil reflux situations of hole digging were analyzed. The soil physical parameters were measured, and the soil parameters were standardized. The results showed that the dynamic and static friction coefficients and collision recovery coefficient of soil and hole digging shovels were 0.14, 0.98 and 0.48, respectively. The accumulation angle regression model was optimized to achieve a target soil accumulation angle of 44.6°. A set of optimal solution resulted in a surface energy between soil particles of 11.8 J/m2, with collision recovery and static friction coefficients of 0.34 and 0.56, and a dynamic friction coefficient of 0.10. The simulated stacking angle under this solution was 42.9°, with a relative error of 3.8% with the measured value. Three simulation models based on the discrete element contact theory were developed to simulate the interactions between the digging shovel and soil in the tobacco field, and computer simulation of the digging process was performed. The soil box model consistent with the actual situation was determined by comparing the results of field experiments with the results of computer simulation. The analysis results of soil reflux showed that there was less soil reflux in the entry phase and more soil reflux in the exit phase with a soil reflux rate of 4.77% in the central area. Disturbance caused by shovel blade in the exit phase was greater, and the soil reflux rate in this phase was 16.41%. The overall soil reflux rate of the whole digging process was 8.66%. The analysis of the change rule of digging resistance showed that the maximum peak of resistance occurred at 0.7 seconds, the maximum operation resistance was 411.3 N, and the maximum power required during the digging process was 137.2 W.

     

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