【作者】 刘伟；

【导师】 胡建平；

【作者基本信息】 江苏大学 ， 农业工程， 2020， 博士

【摘要】 为得到理想的小麦单产,小麦种子需要保证准确的播种量且在所播地块均匀分布。传统的小麦播种机播种量控制系统通过控制排种轴转速间接控制小麦播种量。然而,当外槽轮受到诸如种箱内储种高度降低、外槽轮工作长度变化等干扰时,外槽轮的单转排量会发生变异,传统的排种轴转速控制系统虽然可以使排种轴转速逼近理论值,但是无法消除由于外槽轮受到干扰而导致的播种量误差,因此需要实时监测排种流量,对实际播种量进行反馈调控。为达到上述目标,本文开展了基于排种流量信息的小麦播种机播种量监测调控技术研究。主要研究内容与结果如下:(1)小麦大流量排种种子流重构技术研究针对传统光学传感器在小麦大流量条件下多粒种子同时遮挡监测光线会产生漏测的问题,提出了一种小麦种子流重构技术,减小种子通过监测光线时的重叠现象。设计了弧形分散板结构与平行通道监测结构,用于将密集的小麦种子流进行分散,再重构为种子间有明显间隔的断续种子流。以各通道间落种数变异系数为评价指标,探究了单弧形分散板与双弧形分散板对种子流的分散效果,结合离散元虚拟仿真与响应面试验设计,得到两种弧形分散板的较优结构参数。实际验证试验表明,在单弧板分散结构与双弧板分散结构的最优结构参数下,小麦种子流在各通道间落种数变异系数分别为26.32%与21.63%,由此确定双弧板分散结构为排种流量传感器的种子流分散结构。(2)基于种流重构技术的排种流量监测方法研究为给播种量反馈控制系统提供准确的播种量反馈信息,需要突破大播量小麦种子流排种流量监测技术。融合双弧形分散板结构与信号处理电路,研发了排种流量传感器。针对重构后的断续种子流,统计单粒种子、双粒连续下落种子通过监测光线的穿越时间,针对不同落种数穿越监测光线的时间区间,确定了用于判断具体落种数的时间阈值;开展自研颗粒计数法与传统质量估计法监测准确率对比试验,在理论排种流量为50粒/s至185粒/s的范围内,自研颗粒计数方法监测结果的准确率均大于95%,而传统排种流量估计方法中有57.7%的监测结果准确率大于95%。在任意理论排种流量水平下,颗粒计数法监测值的平均绝对百分比误差均低于质量估计法预测值的平均绝对百分比误差,两者的平均值分别为1.89%与5.91%。上述结果表明,自研排种流量传感器可以满足大流量条件下小麦种子流排种流量精确监测的要求。(3)基于排种流量信息的播种量反馈调控技术研究融合排种流量传感器,研发了一种可以实时监测排种流量的播种量反馈调控系统。与此同时,提出了一种基于排种流量信息的播种量反馈控制方法,该方法可以根据小麦播种机第i反馈距离内的播种量误差对第(i+1)反馈距离内的播种量进行补偿。小麦播种机恒速行驶条件下,对比了自研播种量反馈控制系统在2.5 m、5 m与7.5 m三种反馈距离下的播种性能,试验结果表明,当反馈距离为7.5 m时,播种量反馈调控系统的播种性能较优,此时播种量准确率与播种量变异系数分别为94.12%与6.77%;相同条件下,排种轴转速控制系统的播种量准确率与播种量变异系数分别为89.00%与8.95%。小麦播种机变速状态下,自研播种量反馈控制系统的播种量准确率与播种量变异系数分别为91.58%与11.08%,排种轴转速控制系统的播种量准确率与播种量变异系数分别为88.48%与13.08%。上述结果表明:不论小麦播种机在恒速状态还是变速状态,自研播种量反馈控制系统的播种性能均优于排种轴转速控制系统。(4)播量反馈控制系统田间性能试验研究在大田环境下作业,排种流量传感器与播种量反馈控制系统会受到播种机震动的影响,因此首先需要对排种流量传感器与控制系统进行改进,提高其抗震性能。之后,开展了排种流量传感器田间性能验证试验,两个受测排种流量传感器的平均准确率分别为92.39%与93.44%;将两排种流量传感器监测值总和视为总监测值,则排种流量传感器在各试验水平组合下的平均监测准确率为92.91%。之后,开展了播种量反馈控制系统与排种轴转速控制系统对比试验,播种量反馈控制系统与排种轴转速控制系统的地块总播种量准确率分别为97.71%与96.33%;在单个反馈距离内,播种量反馈控制系统与排种轴转速控制系统的平均播种量准确率分别为92.88%与90.46%;将10 cm内的种子视为一个检测分段,播种量反馈控制系统与排种轴转速控制系统的播种量变异系数分别为30.19%与32.63%。综上所述,本研究提出的基于排种流量信息的小麦播种量监测调控技术可以有效提高小麦播种准确性与均匀性,为提高小麦单产奠定基础。更多还原

【Abstract】 In order to obtain a desired wheat yield,wheat seeds need to be sown at an accurate sowing amount and are uniformly distributed in the sown field.The conventional seeding rate control system of the wheat drill controls the seeding rate indirectly by regulating the rotation speed of the seeding shaft.However,when the seed metering device is interfered with the disturbances,such as the decrease of the seeds’ mass in the hopper and the change of the working length of the flute roller.The seeds’ mass discharged per rotation of the flute roller will be changed.Although the conventional roller speed control system can enable the roller speed to approach to the theoretical value,the error of the seeding rates caused by the interference of the flute roller cannot be eliminated.In order to solve the aforementioned problems,a seeding rate regulating technology based on the real-time monitoring information of seeding flow rates was studied.Specific research contents and results are listed as follows:(1)Seed flow reconstruction technique for large wheat-seed flow rateConventional photoelectric sensors will miss the detection,if more than one seed pass through the monitoring beam together.Thus,a reconstruction technique of seed flow rate was proposed for reducing the overlap phenomenon.A dispersing board structure and a parallel-channel structure were designed.They were used to separate the dense seed flow and then reconstruct several intermittent seed flows.When the dispersing uniformity of the seeds was set as the assessment criterion,the dispersing performance of the single-dispersing-board structure and that of the double-dispersing-board structure were compared.Combining the numerical simulations of the discrete element method and the experimental design of response surface method,the optimized structural parameters of the aforementioned two dispersing structures were obtained.The simulation results showed that the coefficient of variation of seeds’ number in every channels was 26.32% when using the single-dispersing-board structure,while the coefficient of variation of seeds’ number in every channels was 21.63% when the double-dispersing-boards structure was used to separate the seed flow,and thus the double-dispersing-boards structure was ascertained as the seed flow dispersion structure of the seed flow rate sensor.(2)The seed flow rate monitoring method based on the seed flow reconstruction techniqueIn order to provide the accurate seeding rate to the seeding rate control system,the seed flow rate monitoring technique needs breakthrough.Based on the double-dispersing-boards structure and signal processing circuit,a seed flow rate sensor was developed.The passing time of a single seed and double seeds through the monitoring beam was measured.According to the passing time of seeds of a different number,a threshold of passing time,for judging the number of seeds,was ascertained.Experiments were carried out to compare the accuracies of the proposed seed-number counting method and a conventional seed-mass estimating method.When the interval of the theoretical seed flow rate was from 50 particles per second to 185 particles per second,all of the accuracies of results of the proposed seed-number counting method were more than 95%.While only 57.7% accuracies of the results of the conventional seed-mass estimating method was more than 95%.At any theoretical level of the seed flow rate,the average absolute percentage error of monitored values by the seed-number counting is lower than that of the predicted values by the seed-mass estimating method,are 1.89% and 5.91% respectively.The comparison experimental results revealed that the proposed seed-number counting method can be used to monitor the seed flow rate at the condition of the large seeding rate.(3)The seeding rate control technique based on the real-time seed flow rate monitoring informationA seeding rate control system,which integrated the self-designed seed flow rate sensor,was developed.Also,a seeding rate control method based on the real-time monitoring values of the seed flow rates was proposed.The core part of the control method was a modified expert control algorithm which can compensate the seeding rate in the(i+1)th feedback distance according to the error of the seeding rate in the ith feedback distance.The seeding performances of the developed control system with the feedback distances of 2.5 m,5 m and 7.5 m were compared.The results showed that 7.5 m was the optimal feedback distance.Under this condition,the accuracy(SA)and the coefficient of variation(SCV)of the seeding rate of the developed seeding control system were 94.12% and 6.77%,respectively.Under the same condition,the SA and the SCV of the conventional roller speed control(RSC)system were 89.00%and 8.95%,respectively.When the wheat drill travelled at various velocities,the SA and SCV of the proposed system were 91.58% and 11.08%,respectively,while the SA and SCV of the conventional roller speed control system were 88.48% and 13.08%,respectively.The aforementioned results indicated that no matter under the constant-velocity or various-velocity conditions,the performance of the proposed seeding rate control method was better than that of the conventional RSC method.(4)The field experiments for the validation of the performance of the developed seeding rate control systemIn the field condition,the performance of the self-designed seed flow rate sensor and the developed seeding rate control system may be affected by the vibrations of the wheat drill.Therefore,at first,the developed sensor and control system were modified for obtaining a better performance of anti-vibration.Afterwards,the verification experiments for seed flow rate sensor were conducted and the average accuracy of the two tested sensors were 92.39% and 93.44%,respectively.If the monitoring results of two sensors were viewed as a total one,the average accuracy of the results was92.91%.Moreover,the comparison experiment of the developed seeding rate control system and the conventional roller speed control(RSC)system were carried out.Concerning the seeding amount in the holistic sown field,the SA values of the developed system and the RSC system were 97.71% and 96.33%,respectively.In each feedback distance,the SA value of the developed system and that of the RSC system were 92.88% and 90.46%,respectively.The number of seeds in 10 cm was taken as a sowing unit,the SCV of the developed system and the RSC system were30.19% and 32.63%,respectively.In conclusion,the developed seeding rate control system can effectively improve the sowing accuracy and sowing uniformity,which laid the foundation of desired crop yield.更多还原