Spatial change detection using voxel classification by normal distributions transform

Detection of spatial change around a robot is indispensable in several robotic applications, such as search and rescue, security, and surveillance. The present paper proposes a fast spatial change detection technique for a mobile robot using an on-board RGB-D/stereo camera and a highly precise 3D map created by a 3D laser scanner. This technique first converts point clouds in a map and measured data to grid data (ND voxels) using normal distributions transform and classifies the ND voxels into three categories. The voxels in the map and the measured data are then compared according to the category and features of the ND voxels. Overlapping and voting techniques are also introduced in order to detect the spatial changes more robustly. We conducted experiments using a mobile robot equipped with real-time range sensors to confirm the performance of the proposed real-time localization and spatial change detection techniques in indoor and outdoor environments.