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基于改进YOLOv8n的密集分布猕猴桃花期检测方法

Densely distributed kiwifruit flowering period detection method based on improved YOLOv8n

  • 摘要: 为解决不同花期猕猴桃花朵大量遮挡、重叠现象导致检测困难的问题,该研究提出一种基于改进YOLOv8n的密集分布猕猴桃花期检测模型YOLOv8-KFP。首先,以YOLOv8n为基准模型,采用StarBlock改进YOLOv8n的C2f,保持模型轻量同时增强特征表达能力。其次,引入SSFF(scale sequence feature fusion)模块、TFE(triple feature encoder)模块、DySample上采样器改进Neck网络,动态适应不同尺度、形状、边界的花朵目标,提升模型多尺度信息提取能力,减少对遮挡、重叠猕猴桃花朵的误检和漏检。最后,利用Soft-NMS进行后处理,减少目标候选框的误删。结果表明,YOLOv8-KFP模型的精确率、召回率和平均精度均值分别达到了89.1%、88.7%和92.4%,相比于YOLOv8n模型分别提高了4.9、5.1和3.8个百分点,浮点运算量和参数量分别降低了6.2%和11.6%。与主流目标检测模型SSD、YOLOv9t、YOLOv10n、YOLOv11n和YOLOv12n进行对比,YOLOv8-KFP模型的平均精度均值分别提高了7.0、4.0、5.5、4.2和4.1个百分点,其在花苞期、半开期、全开期和凋落期上的召回率分别为90.8%、85.9%、90.0%和88.1%。YOLOv8-KFP模型在保持模型轻量化的同时提高了检测精度,能够实现对密集分布猕猴桃花期的有效检测,可为猕猴桃花朵的自动化授粉提供技术支撑。

     

    Abstract: In order to solve the problem of difficult detection caused by the heavy occlusion and overlap of kiwifruit flowers at different flowering periods, this study proposes YOLOv8-KFP, a densely distributed kiwifruit flowering period detection model based on improved YOLOv8n. Firstly, taking the lightweight YOLOv8n as the benchmark model, StarBlock is used to improve the C2f of YOLOv8n, and the "Star operation" is used to enhance the ability of feature expression, so as to reduce the amount of model parameters and calculation and improve the ability of feature extraction. Secondly, the scale sequence feature fusion (SSFF) module and the triple feature encoder (TFE) module are introduced into the neck network to fuse the feature maps of different scales, so as to enhance the ability of the model to capture the multi-scale details and alleviate the problem of false detection and missing detection of blocked and overlapping kiwifruit flowers; The DySample upsampler is used to replace the traditional interpolation method to dynamically adapt to flower targets with different scales, shapes and boundaries, alleviate the fuzzy problem of dense flower edges, and improve the target positioning accuracy. Finally, the Soft-NMS post-processing algorithm is introduced to further optimize the detection effect of dense targets by adjusting the confidence of overlapping candidate boxes to reduce false deletion. 3 853 images of kiwifruit flowers densely distributed under natural conditions were collected and labeled according to the bud stage, half open stage, full open stage and withering stage. Combined with a variety of data enhancement strategies, 300 epochs of iterative training were completed on NVIDIA A40 GPU platform. Ablation experiments show that the use of C2f_Star module to improve the backbone network, the introduction of SSFF module and TFE module to improve the neck network, the use of DySample upsampler, and the use of Soft-NMS post-processing algorithm can respectively improve the performance of the model to a certain extent, and the improved module has a significant synergy. The final model achieved the precision (P) of 89.1%, the recall (R) of 88.7%, and the mean average precision (mAP) of 92.4% at an intersection over union (IoU) ratio of 0.5, while reducing the number of parameters and floating point of operations (FLOPs) to 2.66 M and 7.6 G, respectively. The improvement effect of the feature fusion network using SSFF module and TFE module and various feature fusion networks such as BiFPN, Slim-Neck, RepGFPN, HS-FPN on YOLOv8n were compared. The YOLOv8n using SSFF module and TFE module to improve the feature fusion network achieved the best effect in precision, recall and mAP0.5, showing its excellent performance in multi-scale feature fusion of kiwifruit flowers. Compared with the mainstream lightweight target detection models SSD、YOLOv9t、YOLOv10n、YOLOv11n and YOLOv12n, the mAP0.5 of YOLOv8-KFP is increased by 7.0, 4.0, 5.5, 4.2 and 4.1 percentage points respectively. Compared with the more complex YOLOv8s, YOLOv8-KFP is increased by 2.7 percentage points on mAP0.5, the amount of FLOPs is reduced by 73.2%, and the amount of parameters is reduced by 76.1%, giving good consideration to the detection accuracy and the lightweight of the model. Moreover, the visualization results show that the improved model significantly reduces the missed detection rate in complex scenes such as branches and leaves occlusion and flowers occlusion, and can more accurately distinguish flower targets in different flowering periods, and has stronger robustness in the densely distributed kiwifruit flowering period detection task. The research results provide a high-precision and lightweight detection method reference for kiwifruit intelligent pollination robot, and have practical application value for improving the level of orchard automation management.

     

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