Using EM to detect motion with mobile robots

In this paper we present a new method to detect motion from mobile platforms using laser range data. Motion can be found as differences in successive scans. The main challenge in doing so from a mobile platform is to distinguish differences originating from the platforms own motion from those caused by objects moving in the robot´s vicinity. We tackle this combining localization and data association based on an a-priori obtained map. Localization and data association is done using the EM-algorithm. Elements, which are not in the map, are singled out as outliers. Subtracting them over time provides motion information. To reduce the complexity of each iteration step we chose a feature-based environment model, which reduces the computation required to a fraction. We use simulations to test our method against a known ground-truth. Results based on real-world data from the exhibition Robotics@Expo.02 are used to evaluate the proposed method under real-world conditions in highly dynamic situations with several hundred visitors per hour.