LET-SE2-VINS: A Hybrid Optical Flow Framework for Robust Visual–Inertial SLAM

This paper presents SE2-LET-VINS, an enhanced Visual-Inertial Simultaneous Localization and Mapping (VI-SLAM) system built upon the classic Visual-Inertial Navigation System for Monocular Cameras (VINS-Mono) framework, designed to improve localization accuracy and robustness in complex environments. By integrating Lightweight Neural Network (LET-NET) for high-quality feature extraction and Special Euclidean Group in 2D (SE2) optical flow tracking, the system achieves superior performance in challenging scenarios such as low lighting and rapid motion. The proposed method processes Inertial Measurement Unit (IMU) data and camera data, utilizing pre-integration and RANdom SAmple Consensus (RANSAC) for precise feature matching. Experimental results on the European Robotics Challenges (EuRoc) dataset demonstrate that the proposed hybrid method improves localization accuracy by up to 43.89% compared to the classic VINS-Mono model in sequences with loop closure detection. In no-loop scenarios, the method also achieves error reductions of 29.7%, 21.8%, and 24.1% on the MH_04, MH_05, and V2_03 sequences, respectively. Trajectory visualization and Gaussian fitting analysis further confirm the system's good robustness and accuracy. SE2-LET-VINS offers a robust solution for visual-inertial navigation, particularly in demanding environments, and paves the way for future real-time applications and extended capabilities.