高级检索+

融合深度学习与形态学处理的玉米田间杂草生长点定位方法

Locating weed growth points in maize fields fusing deep learning and morphological processing

  • 摘要: 为实现激光除草机器人对杂草生长点的精准、快速定位,该文针对玉米田间环境下杂草目标尺度小、形状不规则及相互遮挡导致定位不准的问题,提出了一种融合YOLOv11检测与数学形态学的杂草生长点定位方法。首先,为解决小目标、不规则及遮挡杂草的检测精度不足问题,构建了YOLOv11n-LBD(YOLOv11n-LAE-BiFPN-DyHeadDCNv4)轻量级检测模型,集成了轻量自适应提取模块(Lightweight adaptive extraction,LAE)、双向特征金字塔网络(Bidirectional feature pyramid network, BiFPN)与DyHeadDCNv4检测头,显著增强了复杂田间环境下对多尺度杂草的特征提取能力,提升了小目标与遮挡杂草的检测精度。改进模型在玉米田间自建杂草数据集上平均精度均值(Mean average precision,mAP)为94.8%,相比基线模型参数量和计算量分别降低了0.4M和0.8G,检测速度为79.4帧/s。针对检测框几何中心与杂草真实生长点存在较大偏差的问题,提出基于骨架密度峰值分析的杂草生长点定位方法(Skeleton density peak analysis for apical meristem localization, SDPL):基于YOLOv11n-LBD模型检测结果截取杂草的感兴趣区域,通过高斯滤波与Otsu自适应阈值分割构建高质量二值化掩膜,有效抑制背景干扰,为后续分析提供清晰的二值化图像;在此基础上,引入Zhang-Suen骨架细化提取与B样条曲线拟合相结合的骨架优化策略,在保留杂草拓扑结构的同时实现骨架的平滑与连贯,解决了传统骨架提取中存在的断裂与毛刺问题;以优化后的骨架分支交点作为候选点,通过分析各候选点圆形邻域内的像素密度分布,识别局部密度峰值,实现杂草生长点的精准定位。试验结果表明,该方法杂草生长点定位准确率达81.2%,相较于检测框几何中心定位法与YOLOv8-pose方法,分别提升14.0与3.0个百分点,为激光除草机器人杂草生长点的精准定位提供技术支持。

     

    Abstract: Locating weed growth points is often required in laser weeding. However, the high accuracy is also confined to the small target size, irregular morphology, and mutual occlusion in cornfield environments. In this study, the apical meristem localization (SDPL) framework was proposed to integrate an improved deep learning detector with the skeleton and density peak analysis. Firstly, a lightweight model, named YOLOv11n-LBD, was developed to detect the small, irregular, and partially occluded weeds. Three enhancements were incorporated using YOLOv11n: a Lightweight Adaptive Extraction (LAE) module for efficient and adaptive feature encoding, a bidirectional feature pyramid network (BiFPN) for the multi-scale feature fusion with learnable weights, and a DyHeadDCNv4 detection head with dynamic attention and deformable convolution for refined spatial and scale-aware feature representation. The subtle features were then extracted under complex fields. A custom dataset was constructed to collect corn seedlings and five common weed species. A series of tests was also conducted to verify the framework. The results showed that the improved model achieved a mean average precision (mAP) of 94.8% and a recall of 93.2%. Compared with the baseline YOLOv11n, the parameter count and computational complexity were reduced by 0.4 million and 0.8 GFLOPs, respectively, with a real-time inference speed of 79.4 frames per second. There was a favorable balance between accuracy and efficiency suitable for mobile or embedded deployment in field robots. The SDPL localization was introduced to reduce the positional deviation between the bounding box geometric center and the actual biological growth point of a weed. The region of interest (ROI) was cropped using the YOLOv11n-LBD output. A high-quality binary mask was then generated for noise suppression using Gaussian filtering, followed by Otsu's adaptive thresholding for robust segmentation, effectively isolating the plant from the background. Morphological opening and closing operations were applied to suppress noise for the high connectivity. Subsequently, a skeleton optimization was implemented. The initial single-pixel skeleton was extracted using the Zhang-Suen parallel thinning algorithm, thus preserving the topological structure. The raw skeleton was smoothed and refined to reduce the artifacts, such as jaggedness and spurious branches. A continuous and natural skeletal representation was obtained after B-spline curve fitting. Candidate growth points were defined as the junction points of the refined skeleton branches. Finally, the precise growth points were identified to evaluate the local pixel density distribution within a circular neighborhood around each candidate. The final localization points were selected as the highest local density peak, indicating the most concentrated area of plant tissue near the stem base. Experimental validation on field images showed that there was a growth point localization accuracy of 81.2%. The accuracies were improved by 3.0 and 14.0 percentage points, respectively, compared with the key point detection and bounding box center positioning. The SDPL performed reliably for weeds with irregular shapes under partial occlusion, and even when overlapping with crop plants, where the geometrical method often failed. Robust detection and morphological-densitometric analysis can provide a precise, practical, and computationally efficient visual perception in laser weeding robots, contributing to targeted and energy-efficient weed control in sustainable agriculture.

     

/

返回文章
返回