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马铃薯播种机
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马铃薯播种机性能评估【中文】,马铃薯播种机
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马铃薯播种机的性能评估 大多数马铃薯播种机都是通过勺型输送链对马铃薯种子进行输送和投放。当种植精度只停留在一个可接受水平的时候这个过程的容量就相当低。主要的限制因素是：输送带的速度以及取薯勺的数量和位置。假设出现种植距离的偏差是因为偏离了统一的种植距离，这主要原因是升运链式马铃薯播种机的构造造成的.一个理论的模型被建立来确定均匀安置的马铃薯的原始偏差，这个模型计算出两个连续的马铃薯触地的时间间隔。当谈到模型的结论时，提出了两种假设，一种假设和链条速度有关，另一种假设和马铃薯的形状有关。为了验证这两种假设，特地在实验室安装了一个种植机，同时安装一个高速摄像机来测量两个连续的马铃薯在到达土壤表层时的时间间隔以及马铃薯的运动方式。结果显示：（a）输送带的速度越大，播撒的马铃薯越均匀；（b）筛选后的马铃薯形状并不能提高播种精度。主要的改进措施是减少导种管底部的开放时间，改进取薯杯的设计以及其相对于导种管的位置。这将允许杯带在保持较高的播种精度的同时有较大的速度变化空间。介绍说明升运链式马铃薯种植机（图一）是当前运用最广泛的马铃薯种植机。每一个取薯勺装一块种薯从种子箱输送到传送链。这条链向上运动使得种薯离开种子箱到达上链轮，在这一点上，马铃薯种块落在下一个取薯勺的背面，并局限于金属导种管内.在底部，输送链通过下链轮获得足够的释放空间使得种薯落入地沟里。 图一，杯带式播种机的主要工作部件：（1）种子箱；（2）输送链；（3）取薯勺；（4）上链轮；（5）导种管；（6）护种壁；（7）开沟器；（8）下链轮轮；（9）释放孔；（10）地沟。 株距和播种精确度是评价机械性能的两个主要参数。高精确度将直接导致高产以及马铃薯收获时的统一分级(McPhee et al, 1996；Pavek & Thornton, 2003)。在荷兰的实地测量株距（未发表的数据）变异系数大约为20%。美国和加拿大早期的研究显示，相对于玉米和甜菜的精密播种，当变异系数高达69%(Misener, 1982；Entz & LaCroix, 1983；Sieczka et al, 1986)时，其播种就精度特别低。输送速度和播种精度显示出一种逆相关关系，因此，目前使用的升运链式种植机的每条输送带上都装备了两排取薯勺而不是一排。双排的取薯勺可以使输送速度加倍而且不必增加输送带的速度。因此在相同的精度上具有更高的性能是可行的。该研究的目的是调查造成勺型带式种植机精度低的原因，并利用这方面的知识提出建议，并作设计上的修改。例如在输送带的速度、取薯杯的形状和数量上。为了便于理解，建立一个模型去描述马铃薯从进入导种管到触及地面这个时间段内的运动过程，因此马铃薯在地沟的运动情况就不在考虑之列。由于物理因素对农业设备的强烈影响(Kutzbach, 1989)，通常要将马铃薯的形状考虑进模型中。两种零假设被提出来了：（1）播种精度和输送带速度无关；（2）播种精度和筛选后的种薯形状（尤其是尺寸）无关。这两种假设都通过了理论模型以及实验室论证的测试。材料及方法2.1 播种材料几种马铃薯种子如圣特、阿玲达以及麻佛来都已被用于升运链式播种机测试，因为它们有不同的形状特征。对于种薯的处理和输送来说，种薯块茎的形状无疑是一个很重要的因素。许多形状特征在结合尺寸测量的过程中都能被区分出来(Du & Sun, 2004； Tao et al, 1995； Zdler, 1969)。在荷兰，马铃薯的等级主要是由马铃薯的宽度和高度（最大宽度和最小宽度）来决定的。种薯在播种机内部的整个输送过程中，其长度也是一个不可忽视的因素。形状因子S的计算基于已经提到的三种尺寸： 此处l是长度，w是宽度，h是高度（单位：mm），且hw001 m时，这种关系是线性的。 ，测量数据；，数学模型的数据； ，延长到R 0 01米； -，线性关系；R2，决定系数。3.2 马铃薯的尺寸和形状 实验数据由表三给出。显示固定进料率为每分钟400个种薯的时间间隔的标准偏差。这些结果与期望值刚好相反，即高的标准偏差将使得形状因子增加。球状马铃薯的结果尤其令人吃惊：球的标准偏差高过阿玲达马铃薯50%以上。时间间隔的正态分布如图七所示，球和马铃薯之间的差异明显。两个不同品种的马铃薯之间的差异不明显。 表三 马铃薯品种对种植间距的精确度的影响 品种 标准偏差，ms CV, % 阿玲达 8.60 30 麻佛来 9.92 35 高尔夫球 13.24 46 图七，固定进料率下不同形状的沉积的马铃薯时间间隔的正态分布。球状马铃薯的这种结果是因为球可以以不同的方式在取薯勺背部定位。临近杯中球的不同定位导致沉积精度降低。杯带的三维视图显示了取薯勺与导种管之间的间隔的形状，显然获得不同大小的开放空间是可行的。图八，取薯勺呈45度时的效果图；马铃薯在护种壁的位置对其释放具有决定性影响。阿玲达块茎种薯在沉积时比麻佛来的精度高。通过对记录的帧和马铃薯的分析，结果表明：阿玲达这种马铃薯总是被定位平行于最长的轴线的护种壁。因此，除了形状因子外，宽度与高度的高比例值也将造成更大的偏差。阿玲达的这个比例是1.09，麻佛来的为1.15。3.3 实验室对抗模型测试平台该数学模型预测了不同情况下的流程性能。相对于马铃薯，该模型对球模拟了更好的性能，然而实验测试的结果却恰然相反。另外实验室试验是为了检查模型的可靠性。在该模型里，两个马铃薯之间的时间间隔被计算出来。起始点出现在马铃薯开始经过A点的时刻，终点出现在马铃薯到达C点的时刻。通过实验平台，从A到C点的马铃薯的时间间隔被测出。每个马铃薯的长度、宽度和高度也通过测量获得，同时记录了马铃薯的数量。测量过程中马铃薯在取薯杯上的位置是已经确定好的。这个位置和马铃薯的尺寸将作为模型的输入量，测量过程将阿玲达与麻佛来以400个马铃薯每分的速率下进行。测量时间间隔的标准偏差如表四所示。测量的标准误差与模型的标准误差只是稍稍不同。对这种不同现象的解释是：（1）模型并没有把图八中出现的情况考虑进去；（2）从A点到C点的时间不一致。块状马铃薯如阿玲达可能从顶部或者最远距离下落，这将导致种薯到达C点底部的时间增加6ms表四 通过实验室测量和模型计算出来的开放时间的标准误差的差异 品种 形状因子 标准偏差, ms 测量值 计算值 阿玲达 326 8.02 5.22 麻佛来 175 6.96 4.404. 总结这个模拟马铃薯从输送带开始释放的运动的数学模型是一个非常有用的证实假设和设计实验平台的工具。模型和实验室的测试都表明：链速越高，马铃薯在零速度水平沉积得更均匀。这是由于开口足够大使得马铃薯下降得越快，这对马铃薯的形状和种薯在取薯杯上的定位有一定的影响，与链条速度的关系也就随之明确，因此，在保持高的播种精度时，应该提供更多的空间以减小链条的速度。建议降低链轮的半径，直至低到技术上的可行度。该研究显示，播种机的取薯勺升运链链对播种精度（播种的幅宽）有很大的影响。更规格的形状（形状因子低）并不能自动提高播种精度。小球（高尔夫球）在很多情况下沉积的精度低于马铃薯，这是由导向的导种管和取薯勺的形状决定的。因此建议重新设计取薯勺和导种管的形状，要做到这一点还应该将小链轮加以考虑。外文原文Assessment of the Behaviour of Potatoes in a Cup-belt PlanterThe functioning of most potato planters is based on transport and placement of the see potatoes by a cup-belt. The capacity of this process is rather low when planting accuracy has to stay at acceptable levels. The main limitations are set by the speed of the cup-belt and the number and positioning of the cups. It was hypothesized that the inaccuracy in planting distance, that is the deviation from uniform planting distances, mainly is created by the construction of the cup-belt planter. To determine the origin of the deviations in uniformity of placement of the potatoes atheoretical model was built. The model calculates the time interval between each successive potato touching the ground. Referring to the results of the model, two hypotheses were posed, one with respect to the effect of belt speed, and one with respect to the inuence of potato shape. A planter unit was installed in a laboratory to test these two hypotheses. A high-speed camera was used to measure the time interval between each successive potato just before they reach the soil surface and to visualize the behaviour of the potato. The results showed that: (a) the higher the speed of the cup-belt, the more uniform is thedeposition of the potatoes; and (b) a more regular potato shape did not result in a higher planting accuracy. Major improvements can be achieved by reducing the opening time at the bottom of the duct and by improving the design of the cups and its position relative to the duct. This will allow more room for changes in the cup-belt speeds while keeping a high planting accuracy. 1. Introduction The cup-belt planter (Fig. 1) is the most commonly used machine to plant potatoes. The seed potatoes are transferred from a hopper to the conveyor belt with cups sized to hold one tuber. This belt moves upwards to lift the potatoes out of the hopper and turns over the upper sheave. At this point, the potatoes fall on the back of the next cup and are confined in a sheet-metal duct. At the bottom, the belt turns over the roller, creating the opening for dropping the potato into a furrow in the soil. Capacity and accuracy of plant spacing are the main parameters of machine performance.High accuracy of plant spacing results in high yield and a uniform sorting of the tubers at harvest (McPhee et al., 1996; Pavek & Thornton, 2003). Field measurements (unpublished data) of planting distance in The Netherlands revealed a coefficient of variation (CV) of around 20%. Earlier studies in Canada and the USA showed even higher CVs of up to 69% (Misener, 1982; Entz & LaCroix, 1983; Sieczka et al., 1986), indicating that the accuracy is low compared to precision planters for beet or maize. Travelling speed and accuracy of planting show an inverse correlation. Therefore, the present cup-belt planters are equipped with two parallel rows of cups per belt instead of one. Doubling the cup row allows double the travel speed without increasing the belt speed and thus, a higher capacity at the same accuracy is expected. The objective of this study was to investigate the reasons for the low accuracy of cup-belt planters and to use this knowledge to derive recommendations for design modifications, e.g. in belt speeds or shape and number of cups. For better understanding, a model was developed, describing the potato movement from the moment the potato enters the duct up to the moment it touches the ground. Thus, the behaviour of the potato at the bottom of the soil furrow was not taken into account. As physical properties strongly inuence the efficiency of agricultural equipment (Kutzbach, 1989), the shape of the potatoes was also considered in the model. Two null hypotheses were formulated: (1) the planting accuracy is not related to the speed of the cup-belt; and (2) the planting accuracy is not related to the dimensions (expressed by a shape factor) of the potatoes. The hypotheses were tested both theoretically with the model and empirically in the laboratory. Fig 1. Working components of the cup-belt planter: (1) potatoes in hopper; (2) cup-belt; (3) cup; (4) upper sheave; (5) duct; (6) potato on back of cup; (7) furrower; (8) roller; (9) release opening; (10) ground level 2 .Materials and methods 2.1. Plant material Seed potatoes of the cultivars (cv.) Sante, Arinda and Marfona have been used for testing the cup-belt planter, because they show different shape characteristics. The shape of the potato tuber is an important characteristic For handling and transporting. Many shape features, usually combined with size measurements, can be distinguished (Du & Sun, 2004; Tao et al., 1995; Zodler,1969).In the Netherlands grading of potatoes is mostly done by using the square mesh size (Koning de et al.,1994),which is determined only by the width and height (largest and least breadth) of the potato. For the transport processes inside the planter, the length of the potato is a decisive factor as well. A shape factor S based on all three dimensions was introduced: (1)Where/ is the length, w the width and h the height of the potato in mm, with hw0.01 m, measurement data; data from mathematica model; ,extended for r0.01m) and the accuracy of the deposition of the potatoes. The model was used to estimate standard deviations for different radii at a feeding rate of 300 potatoes min -1.The results are given in Fig. 6, showing that the model predicts a more gradual decrease in accuracy in comparison with the measured data. A radius of 0.025 m, which is probably the smallest radius technically possible, should have given a decrease in standard deviation of about 75% compared to the original radius.3.2 Dimension and shape of the potatoes The results of the laboratory tests are given in Table 3. It shows the standard deviations of the time interval at a fixe feeding rate of 400 potatoes min-1. These results were contrary to the expectations that higher standard deviations would be found with increasing shape factors. Especially the poor results of the balls were amazing. The standard deviation of the balls was about 50% higher than the oblong potatoes of cv. Arinda. The normal distribution of the time intervals is shown in Fig. 7. Significant differences were found between the balls and the potatoes. No significant differences were found between the two potato varieties. The poor performance of the balls was caused by the fact that these balls could be positioned in many ways on the back of the cup. Thus, different positions of the balls in adjacent cups resulted in a lower accuracy of deposition. The three-dimensional drawing of the cup- belt shows the shape of the gap between cup and duct illustrating that different opening sizes are possible (Fig.8).Table 3Effect of cultivars on the accuracy of plant spacing; CV, coefficient of variation Cultivar Standard deviation, ，ms CV, %Arinda 8.60 30Marfona 9.92 35Golf balls 13.24 46Fig.7. Normal distribution of the time interval (x, in ms) of deposition of the potatoes for different shaps factors at a fixedFig 8. View from below to the cup at an angle of 45 degrees; position of the potato on the back of the cup is decisive for its release Arinda tubers were deposited with a higher accuracy than Marfona tubers. Analysis of the recorded frames and the potatoes, demonstrated that the potatoes of cv. Arinda always were positioned with their longest axis parallel to the back of he cup. Thus, apart from the shape factor, a higher ratio width/height will cause a greater deviation. For cv. Arinda, this ratio was 1.09, for cv. Marfona it was 1.15.3.3. Model versus laboratory test-rig The mathematical model predicted the performance of the process under different circumstances. The model simulated a better performance for spherical balls compared to potatoes whereas the laboratory test showed the opposite. An additional laboratory test was done to check the reliability of the model. In the model, the time interval between two potatoes is calculated. Starting point is the moment the potato crosses line A and end point is the crossing of line C (Fig. 2). In the laboratory test-rig the time-interval between potatoes moving from line A to C was measured (Fig. 3). The length, width and height of each potato was measured and potatoes were numbered. During the measurement it was determined how each potato was positioned on the cup. This position and the potato dimensions were used as input for the model. The measurements were done at a feeding rate of 400 potatoes min-1 with potatoes of cv. Arinda and Marfona. The standard deviations of the measured time intervals are shown in Table 4. They were slightly differen (higher)from the standard deviations calculated by the model. Explanations for these differences are: (1) the model does not take into consideration situations as shown in Fig. 8, (2) the passing moment at line A and C was disputable. Oblong potatoes such as cv. Arinda may fall with the tip or with the longest size down. This may cause up to 6 ms difference for the potato to reach the bottom line C.Table 4 Differences between the standard deviations of the opening time measured in the laboratory and calculated by the model Cultivar Shape factor Standard deviation, ms Measured Calculated Arinda 326 8.02 5.22 Marfona 175 6.96 4.404. Conclusions The mathematical model simulating the movement of the potatoes at the time of their release from the cup-belt was a very useful tool leading to the hypotheses to be tested and to design the laboratory test-rig. Both the model and the laboratory test showed that the higher the speed of the belt, the more uniform the deposition of the potatoes at zero horizontal velocity. This was due to the fact that the opening, allowing the potato to drop, is created quicker. This leaves less effect of shape of the potato and the positioning of the potato on the cup. A relationship with the belt speed was found. So, to provide more room for reductions in the cup-belt speeds while keeping a high planting accuracy it is recommended to decrease the radius of the roller till as low as technically possible. This study showed that the accuracy of planting (distance in the seeding furrow) is inuenced for a large part by the cup-belt unit of the planter. A more regular shape lower shape factor) does not automatically result in a higher accuracy. A sphere (golf ball) in most cases was deposited with a lower accuracy than a potato. This was caused by the shapes of the guiding duct and cups.It is recommended to redesign the geometry of the cups and duct, and to do this in combination with a smaller roller. Acknowledgements Acknowledgements are made to Miedema bv for financial support and making available a planting unit for the laboratory test-rig. The Animal Science group of Wageningen University provided the high-speed video camera. References DuCheng-Jin; SunDa-Wen (2004) Recent developments in the applications of image processing techniques for food quality evalua
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