Fertilizer applications from unmanned aerial vehicles (UAVs) have become increasingly common in crop farming. With the rise in UAV capacities for payload and batteries, and increases in application flight speeds, the demands on spreader performance, particularly discharge rate and uniformity, have grown. To address this, a design was developed which incorporates a horizontal screw auger, curved and straight vanes on the disc, and a cover with bumps. This was designed to enhance the distribution uniformity of a large discharge rate disc spreader for UAV fertilizer application. The discharge device featuring the horizontal screw auger achieved high, precise discharge rates within a compact structure. The fertilizer was sequentially scraped by the vanes, with the curved vanes delaying particle release as batches. Upon release, the fertilizer batches collided with the cover, causing some to rebound and form a non-hollow circular spreading distribution. This two-step process transformed the spreading distribution from arc-shaped to non-hollow circular, thereby enhancing the spreader's uniformity. Simulation using the discrete element method (DEM) investigated how innovative structures improve distribution uniformity. A static spreading numerical model, established through a DEM, explored the impact of four factors (deflection angle of curved vanes, thickness, number, and position of bumps) on spreading distribution. Simulation experiments, conducted using a Box-Behnken design (BBD), optimized bump parameters. The spreader, mounted on a DJI T60 UAV, underwent single-route flight tests, assessing the effects of screw auger rotation rate, disc rotation rate, and flight speed on distribution uniformity. Results indicated that disc rotation rate and flight speed had negligible effects on fertilizer distribution uniformity, while screw auger rotation rate had a significant effect. Recommendations were made to increase disc and flight speeds for low fertilization application rates, enabling the screw auger to work at a higher rotation rate and achieve better uniformity. Field tests demonstrated that a compound fertilizer achieved a discharge rate of 190.02 kg/min, with an 8 m operation width and low coefficient of variation (CV) of 14.04 % for urea application and 14.68 % for compound fertilizer application. The spreader exhibited good uniformity and robustness across various fertilizers and rates. This research successfully developed a high-performance spreader for large-load UAVs, with significant implications for UAV applications in agriculture.

中文翻译：

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无人机施肥大流量圆盘撒肥机分布均匀度改善方法

在农作物种植中，无人机 (UAV) 施肥变得越来越普遍。随着无人机有效载荷和电池容量的增加以及应用飞行速度的提高，对吊具性能（特别是放电率和均匀性）的要求也随之增加。为了解决这个问题，我们开发了一种设计，其中包含水平螺旋钻、圆盘上的弯曲和直叶片以及带凸块的盖子。这是为了提高无人机施肥大流量圆盘撒肥机的分布均匀性而设计的。采用水平螺旋钻的卸料装置在紧凑的结构内实现了高、精确的卸料率。肥料依次被叶片刮落，弯曲的叶片延迟了颗粒的批量释放。释放后，肥料批次与覆盖物碰撞，导致一些肥料反弹并形成非空心的圆形撒播分布。这两个步骤的过程将撒布分布从弧形转变为非空心圆形，从而提高了撒布机的均匀性。使用离散元法 (DEM) 进行模拟研究了创新结构如何提高分布均匀性。通过DEM建立的静态扩散数值模型探讨了四个因素（弯曲叶片的偏转角、凸块的厚度、数量和位置）对扩散分布的影响。使用 Box-Behnken 设计 (BBD) 进行模拟实验，优化凸块参数。该吊具安装在大疆T60无人机上，进行了单航线飞行测试，评估螺旋钻转速、圆盘转速和飞行速度对分布均匀性的影响。结果表明，圆盘转速和飞行速度对施肥均匀度的影响可以忽略不计，而螺旋钻转速的影响则显着。建议提高盘和飞行速度以应对低施肥率，使螺旋钻能够以更高的转速工作并实现更好的均匀性。田间试验表明，复合肥的施肥量为190.02 kg/min，作业宽度为8 m，变异系数（CV）较低，尿素施用14.04%，复合肥施用14.68%。该撒肥机在各种肥料和施用量下均表现出良好的均匀性和稳健性。该研究成功开发了一种用于大载荷无人机的高性能吊具，对无人机在农业中的应用具有重要意义。