无人机场景下基于轻量化YOLOv8的小目标检测算法

A Lightweight YOLOv8-Based Small Object Detection Algorithm in UAV Scenarios

  • 摘要: 基于图像的目标检测是无人机实现自主作业的关键。然而,无人机视角下的图像具有背景复杂、小目标众多等特点,并且机上有限的计算资源限制着模型的大小,以上两方面因素共同制约着模型的检测性能。本文针对无人机航拍场景下现有算法的不足,提出了一种改进YOLOv8的轻量级小目标检测算法Drone-YOLO。首先,针对YOLOv8骨干网络参数多、计算复杂度高的问题,本文结合Ghost模块,设计了一种轻量级特征提取网络CSPGhostNet,通过跨阶段生成特征图,压缩模型大小,高效提取目标特征;其次,针对YOLOv8算法颈部层特征退化、融合不充分的问题,本文提出了一种基于混合注意力机制的多尺度特征融合模块。结合通道注意力和空间注意力,强化局部细节特征同时提升全局特征的整体关联性,增强特征表达;最后,设计了共享小目标检测头,通过卷积共享机制,在减少模型计算量的同时,提高检测速度。并改进回归损失函数,引入基于动态非单调聚焦机制的边界框损失(Wise-IoU, WIoU),增大小预测框损失的权重,使模型更加关注小目标检测。在VisDrone2019数据集和MVSRD数据集上进行测试,相较于原算法,本文提出的算法在各项性能指标中均表现优异,mAP@50分别提升10.9%、9.1%,模型参数量和计算量分别压缩了45.2%、43.9%。在小目标类别检测中,平均精度均提升13%以上。与当前其他流行算法对比,本文提出的改进策略在精度和复杂度之间实现了有效平衡,为算法在无人机端侧的部署奠定了基础。

     

    Abstract: Image-based object detection is a key enabler for UAV to achieve autonomous operations. However, images captured from a drone perspective are characterized by complex backgrounds and numerous small objects. Meanwhile, the limited onboard computational resources restrict the size of the model. Together, these two factors constrain the detection performance of models. To address the shortcomings of existing algorithms in drone aerial photography scenarios, this study proposes Drone-YOLO, a lightweight small object detection algorithm improved from YOLOv8. First, to tackle the problems of excessive parameters and high computational complexity in the YOLOv8 backbone network, this study designed a lightweight feature extraction network called CSPGhostNet by integrating the Ghost module. Through cross-stage feature map generation, it compresses the model size and efficiently extracts object features. Second, aiming at the issues of feature degradation and insufficient fusion in the neck layer of the YOLOv8 algorithm, this study proposes a multi-scale feature fusion module based on a hybrid attention mechanism. By combining channel and spatial attention, it strengthens local detailed features while enhancing the overall correlation of global features, thereby improving feature expression. Finally, a shared small object detection head was designed. Through a convolutional sharing mechanism, the computational load of the model is reduced while increasing detection speed. In addition, the regression loss function was improved by introducing a bounding box loss based on the dynamic non-monotonic focusing mechanism (Wise-IoU, WIoU), which increased the weight of losses from small prediction boxes and made the model pay more attention to small object detection. Tests were conducted on the VisDrone2019 and MVSRD datasets. Compared with the original algorithm, the proposed algorithm performed excellently in all performance metrics: mAP@50 increased by 10.9% and 9.1%, respectively, and model parameters and computational load were reduced by 45.2% and 43.9%, respectively. In the detection of small object categories, the average precision increased by more than 13%. Compared with other popular algorithms currently available, the improved strategy proposed herein achieves an effective balance between accuracy and complexity, laying a foundation for the deployment of the algorithm on the drone edge side.

     

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