设施果园自动对靶精准变量施肥控制系统

    Control system for auto-targeting precision variable-rate fertilization of fruit trees in a greenhouse orchard

    • 摘要: 针对目前果园条施肥过程中缺乏精准变量对靶施肥装置的问题,该研究研制了一种排肥轮槽口体积可根据果树目标施肥量及冠层直径大小自动调节,排肥轮转速随施肥车速自动变化的果园精准变量自动对靶施肥装置与控制系统。该装置采用外槽轮式结构,槽口体积可连续调节自动变化。采用激光雷达传感器实时探测果树冠层位置,使用霍尔传感器检测施肥车行驶速度,以STM32F407VET6单片机为核心设计了控制器。分别以尿素、复合肥、有机复合肥3种颗粒肥料为试验材料,标定了不同排肥轮槽口开度在不同排肥轮转速下的排肥量,单个槽口排肥量与排肥轮转速呈负线性关系,决定系数R2不小于0.93;建立了单棵果树目标施肥量与排肥轮转速、施肥车速、槽口体积以及果树冠层直径4个变量之间的关系及排肥轮转速控制规则。室内台架试验结果表明,单棵柑橘树实际施肥量与给定目标施肥量相对误差最大为5.17%,变异系数最大为1.47%,可在施肥车速变化情况下准确施用不同颗粒肥料。大棚柑橘果园自动对靶施肥试验结果表明,单棵柑橘树实际施肥量与给定目标施肥量相对误差最大为4.83%,变异系数最大为6.96%,且施肥均在果树冠层直径范围内完成。该装置能够根据果树冠层直径大小对靶按需施肥,适应不同种类颗粒肥的少量或较大量定量施肥,满足不同大小果树不同需肥量的精准变量自动施肥要求。

       

      Abstract: Abstract: Over or under-fertilization has normally resulted in environmental pollution or the reduction of fruit production, particularly in orchards. In this study, a precise target fertilization device with variable rates was developed for fruit trees in an orchard. The volume of the groove was automatically adjusted for the fertilizer discharging wheel, according to the diameter of the canopy of fruit trees, and the amount of fertilizer required by the target. The rotation speed of the fertilizer discharging wheel was continuously altered with the speed of the vehicle in the process of fertilization. The external groove wheel structure was adopted in the device to tailor the groove volume. A Lidar sensor was used to detect the canopy position of fruit trees in real time, thereby determining the starting and stopping position of fertilization. A hall sensor was used to detect the speed of the fertilization vehicle, and STM32F407VET6 microcontroller was used as the core to design the controller. Three kinds of granular fertilizers were selected as test materials, including urea, compound fertilizer, and organic compound fertilizer. The amount of fertilizer discharging was also calibrated under various speeds of fertilizer discharging wheels with different groove openings. The fertilizer discharging quantity of a single groove showed a negative linear relationship between the rotation speed of fertilizer discharging wheel, and the determination coefficient R2 was greater than or equal to 0.93. Some mathematical relationships were established between the target fertilizer amount of a single fruit tree and the rotation speed of fertilizer discharging wheel, the speed of fertilization vehicle, the volume of the groove of fertilizer discharging wheel, and the diameter of the canopy of the fruit tree. The control rules of rotation speed were also established for the fertilizer discharging wheel. An experiment of variable fertilization was performed on the citrus trees in a greenhouse, when the target fertilization amount of a single fruit tree was changed from 50 to 2 500 g. The results showed that the relative error of the maximum fertilization was 5.17% in a single fruit tree. Moreover, the average relative error was less than 3%, and the maximum coefficient of variation was 1.47%. Furthermore, the different granular fertilizers were accurately applied under the changing speed of the fertilization vehicle. The relative error of the maximum fertilization was 4.83% in a single citrus tree, the average relative error was less than 4.5%, and the maximum coefficient of variation was 6.96%, and the automatic fertilization was completed within the diameter of the canopy of the fruit tree. Consequently, the device can be expected to apply the fertilizer on the specific target, according to the diameter of the fruit tree canopy, suitable for a small or large amount of quantitative fertilization for the different kinds of granular fertilizer. Precise variable fertilization can contribute to different sizes of fruit trees.

       

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