基于DEM-MBD 耦合的大白菜仿形切根过程仿真与试验

Simulation and Parameter Optimization Experiment of Chinese Cabbage Root-Cutting Process Based on DEM-MBD

摘要:

针对大白菜机械化收获作业中因地表起伏导致仿形效果差、切根合格率低等问题，结合陕西太白地区大白菜种植农艺要求，设计了一种搭载龙门式履带底盘且具备“主动高度调节与被动机械缓冲”功能的仿形切根装置。基于DEM-MBD耦合仿真构建了“土壤-大白菜-机具”多体互作模型，从颗粒层面探明了仿形切根过程动态响应特征与切削破坏行为。开展了单因素试验与多因素Box-Behnken响应面优化试验，以平均切根高度及切根高度一致性变异系数为评价指标，探明了机具前进速度、弹簧刚度、横连杆长度对切根质量的影响规律，并得到最佳参数组合为机具前进速度0.36 m/s、弹簧刚度3.94 N/mm、横连杆长度196.08 mm，此时平均切根高度为24.86 mm，切根高度一致性变异系数为5.08%。在此基础上开展田间验证试验，实际作业参数圆整为机具前进速度0.40 m/s、弹簧刚度4 N/mm、横连杆长度200 mm进行测试。结果表明，该装置平均切根高度为25.84 mm，切根高度一致性变异系数为7.56%，切根合格率达95.89%，能够有效适应地表起伏，切根高度一致性良好。研究结果可为我国大白菜低损高效收获装备设计提供理论依据与技术支撑。

Abstract:

Aiming to address the issues of poor terrain profiling and low qualified root-cutting rates caused by uneven ground during the mechanized harvesting of Chinese cabbage, a profiling root-cutting device was designed based on the agronomic planting requirements in Taibai area of Shaanxi Province. This device was mounted on a gantry-type crawler chassis and featured "active height adjustment and passive mechanical buffering" functions. A "soil-Chinese cabbage-machine" multi-body interaction model was constructed by using DEM-MBD coupled simulation to reveal the dynamic response characteristics and cutting failure behavior during the profiling root-cutting process at the particle level. Single-factor tests and multi-factor Box-Behnken response surface optimization experiments were conducted. Using the average root-cutting height and the coefficient of variation (CV) of the root-cutting height consistency as evaluation indices, the comprehensive effects of the machine's forward speed, spring stiffness, and horizontal link length on root-cutting quality were investigated. The optimal theoretical parameter combination was determined as follows: a forward speed of 0.36 m/s, a spring stiffness of 3.94 N/mm, and a horizontal link length of 196.08 mm. Under these conditions, the average root-cutting height was 24.86 mm, and the CV of the root-cutting height consistency was 5.08%. Subsequently, field validation tests were conducted by rounding the actual operating parameters to a forward speed of 0.40 m/s, a spring stiffness of 4 N/mm, and a horizontal link length of 200 mm. The field test results showed an average root-cutting height of 25.84 mm, a CV of 7.56%, and a qualified root-cutting rate of 95.89%. These results demonstrated that the device can effectively adapt to terrain undulations and maintain excellent root-cutting consistency. The research findings can provide a theoretical basis and technical support for the structural innovation and parameter optimization of low-loss, high-efficiency Chinese cabbage harvesting equipment in China.