双变量螺旋外槽轮排肥器控制序列对排肥性能的影响

Influence of Control Sequence of Spiral Fluted Roller Fertilizer Distributer on Fertilization Performance

施肥稳定性是评价变量施肥机作业性能的重要指标,为了研究排肥口开度(L)和排肥轴转速(n)的组合对排肥性能的影响规律,本文基于离散单元方法,对同一目标施肥量下,不同L和n组合下的施肥过程进行仿真。首先,通过标定试验,构建了基于广义回归神经网络GRNN的排肥量预测模型,经过验证,其决定系数达到0.9994,预测平均相对误差(MRE)为3.56%。其次根据螺旋外槽轮排肥装置的等排肥量曲线,选择3个排肥量1067.37、2323.04、4206.56 g/min为目标排肥量,并利用差分进化算法(DE)确定同一目标施肥量下的控制序列(L,n)的组合。最后,利用离散元仿真软件EDEM 2.8分别对3个目标施肥量,不同控制序列下的排肥过程进行仿真。采用排肥均匀性变异系数σ作为评价排肥稳定性的指标,仿真结果表明,在目标排肥量Q1下,当控制序列为(25 mm,17.78 r/min)时,σ最小,为5.27%;在其他控制序列,σ均高于20%,排肥稳定性较差,且出现断条现象。在目标排肥量Q2下,当控制序列为(65 mm,17.12 r/min)时,σ最小,为3.46%。在目标排肥量Q3下,σ均小于4%,且在控制序列(65 mm,32.85 r/min),σ达到最小,为2.08%。当目标施肥量较小时,控制序列的选择对排肥稳定性影响显著,工作时,应尽量避免开度、转速的边界量。当目标施肥量较大时,控制序列选择对外槽轮排肥稳定性的影响较小。结果表明,螺旋外槽轮排肥器具有较好的排肥稳定性。

Application uniformity is an essential aspect of the performance of a variable-rate fertilization(VRF)applicator.In order to study the relationship between fertilization uniformity and control sequence such as active feed-roll length(L)and rotational speed of the drive shaft(n)for a spiral fluted-roll fertilizer distributer for a bivariate fertilization applicator,the discrete element simulation model was established and the fertilization uniformity was studied by conducting discrete element simulation tests via the discrete element method(DEM)software.Firstly,a calibration was conducted at different active-feed roll length(L)and rotational speed of the drive shaft(n),and then the fertilization model was formed by general regression neural network(GRNN).To test model prediction accuracy,another 20 samples were utilized as test set,the validation result showed that the correlation coefficient(R2)was up to 0.9994 and the mean relative error(MRE)was 3.56%.In addition,three target fertilization,including Q1=1067.37 g/min,Q2=2323.04 g/min,Q3=4206.56 g/min,were chosen according to the equal discharge curve of spiral fluted-roll fertilizer distributer and control index(L,n)at the same target fertilization rate were found by differential evolution algorithm(DE)and formed GRNN model.Finally,the fertilization simulation tests at different control indexes for three different target rates were conducted via EDEM 2.8 software.The coefficient of variationσwas calculated as criteria to evaluate the fertilization uniformity.The result showed that,at target rate of Q1,the minimizedσoccurred at the control index of(25 mm,17.78 r/min),which was 5.27%.At target rate of Q2,the minimizedσwas occurred at control index of(65 mm,17.12 r/min),which was 3.46%.At target rate of Q3,σwas below 4%at all control index.The minimizedσoccurred at control index of(65 mm,32.85 r/min),which was 2.08%.In conclusion,at the small target fertilization rate,the selection of the control sequence had a significant impact on fertilization performance.In fertilization,the opening length and rotational speed boundaries should be avoided.At the large target fertilization rate,the selection of the control sequence had little effect on the fertilization uniformity of spiral fluted-roll fertilizer distributer.