Real-time distant 3D tracking by 3D laser scanner (Developments of new scan function for RobotEye RE05 and algorithms for real-time 3D tracking)

Abstract

This article presents the algorithm for real-time distant 3D tracking by RobotEye RE05, the 3D laser scanner using gimbal mirror mechanism. It is comprised of real-time extraction of moving objects by 3D background subtraction for 3D point cloud scanned by the scanner, tracking of a moving object, and scanning densely around it. For recognizing moving objects, high-speed background subtraction and clustering algorithms for point cloud data are developed. In the background subtraction, background data which contains no moving object is measured, and the distance map is generated, which contains distances of points in sections divided into every small azimuth and elevation angles. The map is adjusted to reduce noises caused by the measurement error and noises around object edges. Then, current data is measured which contains data of moving objects and the distance map is generated. If the distance in the map of current data is nearer than background data, the point is remained as the foreground data. Before clustering, edge noises in the foreground data are removed by the filter newly developed based on statistical outlier removal. This filter is improved by adjusting the number of neighbor points used for searching and mean distance with the neighbor points using the distance of each point. In the clustering, intervals of azimuth, elevation angles and distances of each point are considered to obtain proper results in any distances. Finally, the position and the width of moving objects are computed from the clusters. For following and scanning the moving object, the new function named Tracking Scan was developed, which is new scan motion of RobotEye RE05 for tracking application. This scanner can scan appointed range in azimuth 360deg and elevation ±35deg by desired density. Moreover, the range and density can be updated during scan in Tracking Scan. At last, the experiment result of moving person tracking is described.