甘蓝切根作业力学分析与参数优化

Mechanical analysis and parameter optimization of cabbage root cutting operation

为获得甘蓝切根作业的最优切割要素组合,降低切根过程中的切根反作用力,该研究设计了一种可调式切根装置。首先基于显式非线性动力学分析理论建立切根作业数值模型,对双圆盘切刀切割甘蓝根茎的过程进行数值模拟,揭示切根作业力学机理,确定分力Fy可近似为切根力,切根反作用力Fy′为试验数据采集对象。并通过单因素试验研究,得到单个因素对切根反作用力的影响规律。进一步利用二阶正交旋转组合多因素试验,研究切刀转速、切割位置、行走速度、切刀重叠量和俯仰角度对最大切根反作用力的影响,并采用响应曲面法进行参数优化,建立最大切根反作用力与各因素之间的数学关系模型。结果表明,最优的切割要素组合为切刀转速200 r/min、切割位置17 mm、行走速度0.26 m/s、切刀重叠量22 mm、俯仰角度11°;此时最大切根反作用力为-22.5 N。在优化参数组合下进行验证试验,得到的最大切根反作用力为-21.8 N,切根合格率为96%。该研究可为甘蓝联合收获机切根装置的设计与改进提供理论依据和参考。

In order to obtain the optimal combination of cutting elements and reduce the root cutting reaction force during root cutting process, the adjustable device for root cutting was designed. The basic structure and working principle of the root cutting device were described. The device mainly consisted of connection mechanism, disconnected fixing mechanism, handle adjusting mechanism, bolt adjustment mechanism and transmission mechanism. The test platform of root cutting operation was set up. The test platform was composed of the adjustable root cutting device, the connection support frame, the chassis and the walking device, which can realize the adjustment of the cutting speed, cutting position, cutter overlap amount and pitch angle. Based on the explicit nonlinear dynamic analysis method, the numerical model of root cutting operation was established. Then, the process of cutting cabbage root with double disc cutter was numerically simulated, and the mechanical mechanism was revealed. The forces along X, Y and Z axes during root cutting were analyzed and the force Fy along Y axis was approximated to root cutting force, therefore, root cutting reaction force Fy’ was determined as the data acquisition object of tests. In order to reduce the damage of cabbage and the abrasion of disc cutter, the root cutting force Fy and the root cutting reaction force Fy’ should be reduced as much as possible. The single factor tests were carried out to obtain the influence law of single factor on the evaluation index. The second-order orthogonal rotating combination multi-factor tests were carried out to study the influence of cutter speed, cutting position, walking speed, cutter overlap amount and pitch angle on the maximum root cutting reaction force. The response surface method was used to optimize the parameters, and the mathematical model of the relationship between maximum root cutting reaction force and the factors was established. The results of the multi-factor tests showed that the optimal combination of cutting elements was cutter speed 200 r/min, cutting position 17 mm, walking speed 0.26 m/s, cutter overlap amount 22 mm and pitch angle 11°, and the maximum root cutting reaction force was-22.5 N at this time. Under the conditions of the optimal parameter combination, tests were carried out to verify the optimal results. The test results showed that the average value of the maximum root cutting reaction force was-21.8 N. The result error between the predicted value of the model and the test was 3%, which verified the credibility of the optimization model. The qualified rate of root cutting was 96%, indicating that the root cutting device and test platform designed in this paper could meet the basic requirements of root cutting. The research results can provide theoretical basis and reference for the design and improvement of root cutting device for cabbage combine harvester.