Safe teleoperation of a quadrotor using FastSLAM

Unmanned Aerial Vehicles (UAV) provide many advantages in Search and Rescue (SaR) scenarios, such as the capacity for remote inspection over areas that are difficult to reach by ground vehicles. Moreover, it can carry small payloads, such as first aid equipment, over large distances. However, the teleoperation of UAVs often demands extensive training, since even well trained pilots are prone to mistakes, resulting frequently in collisions of the vehicle with obstacles. This paper presents a method to assist the tele-operation of a quadrotor using an obstacle avoidance approach. The target scenario is SaR operation in unknown, unstructured, GPS-denied environments, such as warehouses or other buildings. A short-term rough map of the nearby environment is constructed using sonar sensors. This map is constructed using FastSLAM to allow tracking of the vehicle position with respect to the map. The map is then used to (1) override operator commands that may lead to a collision, and (2) perform evasive maneuvers whenever collision is imminent. A simple active perception routine is used to orient one of the sensors to an unknown area, in case the UAV is ordered to move towards an unmapped area. Experimental results using the USARsim simulator are presented. Further testing was conducted in a real quadcopter, allowing a preliminary validation of the proposed methods.