Journal of Jilin University(Engineering and Technology Edition) ›› 2025, Vol. 55 ›› Issue (4): 1307-1318.doi: 10.13229/j.cnki.jdxbgxb.20230779

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Dense small object vehicle detection in UAV aerial images using improved YOLOX

He-shan ZHANG1,2(),Meng-wei FAN1,Xin TAN1,Zhan-ji ZHENG1,2,Li-ming KOU3,Jin XU1,2()   

  1. 1.School of Traffic & Transportation,Chongqing Jiaotong University,Chongqing 400074,China
    2.Chongqing Key Laboratory of "Human-Vehicle-Road" Cooperation and Safety for Mountain Complex Environment,Chongqing Jiaotong University,Chongqing 400074,China
    3.Chongqing Transportation Planning and Research Institute,Chongqing 400074,China
  • Received:2023-07-25 Online:2025-04-01 Published:2025-06-19
  • Contact: Jin XU E-mail:hszhang@cqjtu.edu.cn;yhnl_996699@163.com

Abstract:

Aiming at the issues of severe missed detections and low detection accuracy for small targets in the perspective of drone aerial photography, an improved YOLOX network is proposed for the detection of drone aerial images. To enhance the feature learning ability of the network, the ASFF module is introduced in the feature fusion part, and the CA mechanism is embedded in the neck of the network. To enhance the network's learning of positive samples, the binary cross-entropy loss function is replaced with the varifocal loss function. Experimental results show that the improved YOLOX network has better detection efficiency, and its mAP@50 reaches 91.50% and mAP@50_95 reached 79.65%. The visualization results in various traffic scenarios show that compared with other algorithms, the optimized network has a lower missed detection rate and higher detection accuracy, which can be competent for the detection task of small target vehicles, and can provide a reference for vehicle multi-target tracking applications from a high-altitude perspective.

Key words: engineering of communications and transportation system, small target vehicle detection, loss function, coordinate attention mechanism, adaptive spatial feature fusion, YOLOX

CLC Number: 

  • U491

Fig.1

Original YOLOX network"

Fig.2

Improved YOLOX network"

Fig.3

ASFF module"

Fig.4

Coordinate attention mechanism"

Table 1

Parameter configuration"

实验平台型号参数
CPU12 vCPU Intel(R) Xeon(R) Platinum 8255C CPU @2.50 GHz
GPUGeForce RTX 3080(10 GB)
操作系统Windows 10
框架Pytorch
编程环境Python

Fig.5

UAV and its operation interface"

Fig.6

Some images in the dataset"

Table 2

Evaluation index of network detection performance"

指标公式意义
PrecisionP=TPTP+FP

在所有检测到的目标中

检测到正确的概率

RecallR=TPTP+FN

在所有阳性样本中正确

识别的概率

F1_scoreF1=2×R×PR+P

准确率和召回率的

调和均值

APAP=PRdR

同一召回率下精度的

平均值

mAPmAP=1CKCAPK

数据集中所有平均精度

之和的平均值

Table 3

Parameter settings during training"

参 数
训练轮次200
类别3
批次8
初始学习率0
动量0.9
权重衰减5×10-4
检测阈值0.35
解冻训练30
非极大值抑制0.65

Fig.7

Comparison of the descent curve of loss value in training"

Fig.8

mAP@50,and mAP@50_95 in ablation experiment"

Table 4

Comparative results of ablation experiments"

网络mAP@50/%mAP@50_95/%Parameters/M
Original YOLOX89.378.448.94
ASFF89.778.8314.38
ASFF+CA89.979.3514.40
Improved YOLOX91.579.6514.40

Fig.9

Changes in precision, recall, and F1 measurements in training"

Fig.10

Precision-recall curves."

Table 5

Compare the results of different object detection algorithms"

网 络mAP/%Parameters/MPrecision/%Recall/%F1_scoreGflops/G
Original YOLOX89.38.9495.8993.6993.9726.8
Faster R-CNN62.8137.0046.2072.4756.33185.1
SSD88.626.2978.3893.7585.33140.9
YOLOv589.37.1084.9191.3381.0016.5
Improved YOLOX91.514.4095.3394.9494.1335.2

Fig.11

Comparison of visualization results of different object detection algorithms"

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