A Lightweight Three-Keypoint Recognition Method for Line-Laser-Based Robot Vision-Guided Adhesive Dispensing

Line-laser stripes in robot vision-guided adhesive dispensing exhibit narrow local structures, while keypoint localization is highly sensitive to spatial information and online processing imposes stringent requirements on computational efficiency. To address these challenges, this paper proposes a lightweight three-keypoint recognition method for line-laser-based adhesive dispensing. First, a two-stage top-down vision pipeline is adopted: an object detector locates the region of interest (ROI), after which the left, center, and right points are predicted within the local ROI. The keypoint network uses RepViT-M0.6 as a lightweight feature extraction backbone. To compensate for the low spatial resolution of its final-stage features, LiteFlattenSimCCHead is designed to transform deep features into position-sensitive representations better suited to keypoint localization through low-dimensional feature transformation, progressive spatial reconstruction, lightweight local feature fusion, and position-preserving feature flattening. SimCC coordinate classification and DARK distribution-aware decoding are then combined to obtain the coordinates of the three keypoints. Experimental results show that the proposed method achieves an AP of 0.9532, a mean localization error of 3.6385 px, an RMSE of 4.8272 px, and a PCK@5 of 0.7842. Compared with the Lite-HRNet-18 baseline, the mean error and RMSE are reduced by 16.5% and 20.1%, respectively, while AP increases by 3.80 percentage points. For single-ROI inference in the second stage, the final model reaches 116.34 FPS on the GPU and 49.32 FPS on the CPU. These results demonstrate that the proposed method improves localization accuracy while maintaining a lightweight model and high inference efficiency. Therefore, the reported results demonstrate the performance of the vision and keypoint-recognition method, rather than the positioning accuracy of the complete robotic adhesive-dispensing system.