Voxel-Based Representation Learning for Place Recognition Based on 3D Point Clouds.

Place recognition is a critical component towards addressing the key problem of Simultaneous Localization and Mapping (SLAM). Most existing methods use visual images; whereas, place recognition using 3D point clouds, especially based on the voxel representations, has not been well addressed yet. In this paper, we introduce the novel approach of voxel-based representation learning (VBRL) that uses 3D point clouds to recognize places with long-term environment variations. VBRL splits a 3D point cloud input into voxels and uses multi-modal features extracted from these voxels to perform place recognition. Additionally, VBRL uses structured sparsity-inducing norms to learn representative voxels and feature modalities that are important to match places under long-term changes. Both place recognition, and voxel and feature learning are integrated into a unified regularized optimization formulation. As the sparsity-inducing norms are non-smooth, it is hard to solve the formulated optimization problem. Thus, we design a new iterative optimization algorithm, which has a theoretical convergence guarantee. Experimental results have shown that VBRL performs place recognition well using 3D point cloud data and is capable of learning the importance of voxels and feature modalities.