Citation: | Hu W X, Wang Z H, Yu C, et al. A laser inertial SLAM approach based on planar expansion and constrained optimization[J]. Opto-Electron Eng, 2024, 51(4): 230279. doi: 10.12086/oee.2024.230279 |
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The scarcity of features and narrow corners in indoor environments make the laser SLAM algorithm have low localization accuracy and even algorithm failure. To solve the above problems, a laser inertial SLAM method based on plane extension and constraint optimization is proposed. Fusion of IMU in laser SLAM, position compensation of laser point cloud, and judgment of key frames based on IMU state estimation results. Build a global planar map, planar extraction of key frames based on the RANSAC algorithm, and track planar features by combining the pre-extraction method to reduce the time cost, and the fitting results are optimized by iPCA to remove the effect of noise on RANSAC. Using the distance from the point to the plane, construct the plane constraint optimization equation. Integrate it with the edge point constraints and pre-integration constraints in a unified way to establish a nonlinear optimization model. Solve this model to get the optimized plane information and key frame bit position. To verify the effectiveness of the algorithm, experiments are carried out in the M2DGR public dataset and private dataset respectively. The results of plane extraction are shown in Table 1, facing different scenes and distances, the position accuracy error of the plane fitting method, which is based on the combination of RANSAC and iPCA and can be controlled within 10mm. Additionally, the attitude accuracy error is less than 2, meeting the initial value requirements. Figures 9 and 10 visualize the localization effect of this method and other algorithms. The experimental results show that the algorithm not only performs well on the open dataset, but also in the closed-loop dataset "Indoor_01", which has narrow corners and fewer features, the algorithm improves 61.9% compared with the comparison algorithm, which can effectively inhibit the drift caused by the corners and the lack of features (Fig. 10). The planar pre-extraction method effectively reduces the time cost of RANSAC, and the use of planar constraints instead of planar point constraints saves the unnecessary search and fitting process (Fig. 11), which provides the possibility of deploying the algorithm in mobile devices. The experimental results show that the comnbination of planar pre-extraction and the iPCA-based planar optimization scheme effectively eliminates noise and the error caused by the unstrict planes, while also saves the unnecessary RANSAC fitting iterations. The plane constraints also effectively replace the plane point constraints, which are uniformly fused with the edge point constraints and preintegration constraints to participate in the optimization after compression. The proposed method effectively improves the localization accuracy of laser SLAM in indoor environments, demonstrating robustness and real-time capabilities.
Algorithm flow chart
Postural transformation
Comparison chart of iPCA-based planar optimization
Block diagram of tightly coupled nonlinear optimization
Plane constraints
Experimental hardware platform
Realistic environments for different scenarios
Plane extraction. (a) Before extraction; (b) After extraction
Comparison of the estimated trajectories of room_02 and hall_01 sequence algorithms with the real trajectories
Comparison between the estimated trajectory of the Indoor_01 sequence algorithm and the actual trajectory
Running time analysis of each part of this algorithm