A Volumetric Sensor for Real-Time 3d Mapping and Robot Navigation

The use of robots for (semi-) autonomous operations in complex terrains such as urban environments poses difficult mobility, mapping, and perception challenges. To be able to work efficiently, a robot should be provided with sensors and software such that it can perceive and analyze the world in 3D. Real-time 3D sensing and perception in this operational context are paramount.. To address these challenges, DRDC Valcartier has developed over the past years a compact sensor that combines a wide baseline stereo camera and a laser scanner with a full 360 degree azimuth and 55 degree elevation field of view allowing the robot to view and manage overhang obstacles as well as obstacles at ground level. Sensing in 3D is common but to efficiently navigate and work in complex terrain, the robot should also perceive, decide and act in three dimensions. Therefore, 3D information should be preserved and exploited in all steps of the process. To achieve this, we use a multiresolution octree to store the acquired data, allowing mapping of. large environments while keeping the representation compact and memory efficient. Ray tracing is used to build and update the 3D occupancy model. This model is used, via a temporary 2.5D map, for navigation, obstacle avoidance and efficient frontier-based exploration. This paper describes the volumetric sensor concept, describes its design features and presents an overview of the 3D software framework that allows 3D information persistency through all computation steps. Simulation and real-world experiments are presented at the end of the paper to demonstrate the key elements of our approach.