Dense Papaya Target Detection in Natural Environment Based on Improved YOLOv5s

Abstract

Due to the fact that the green features of papaya skin are the same colour as the leaves, the dense growth of fruits causes serious overlapping occlusion phenomenon between them, which increases the difficulty of target detection by the robot during the picking process. This study proposes an improved YOLOv5s-Papaya deep convolutional neural network for achieving dense multitarget papaya detection in natural orchard environments. The model is based on the YOLOv5s network architecture and incorporates the Ghost module to enhance its lightweight characteristics. The Ghost module employs a strategy of grouped convolutional layers and weighted fusion, allowing for more efficient feature representation and improved model performance. A coordinate attention module is introduced to improve the accuracy of identifying dense multitarget papayas. The fusion of bidirectional weighted feature pyramid networks in the PANet structure of the feature fusion layer enhances the performance of papaya detection at different scales. Moreover, the scaled intersection over union bounding box regression loss function is used rather than the complete intersection over union bounding box regression loss function to enhance the localisation accuracy of dense targets and expedite the convergence of the network model training. Experimental results show that the YOLOv5s-Papaya model achieves detection average precision, precision, and recall rates of 92.3%, 90.4%, and 83.4%, respectively. The model’s size, number of parameters, and floating-point operations are 11.5 MB, 6.2 M, and 12.8 G, respectively. Compared to the original YOLOv5s network model, the model detection average precision is improved by 3.6 percentage points, the precision is improved by 4.3 percentage points, the number of parameters is reduced by 11.4%, and the floating-point operations are decreased by 18.9%. The improved model has a lighter structure and better detection performance. This study provides the theoretical basis and technical support for intelligent picking recognition of overlapping and occluded dense papayas in natural environments.