Laser and Optical Flow Fusion for a Non-Intrusive Obstacle Detection System on an Intelligent Wheelchair

In this paper, a method to combine a low-cost 16 beam solid state laser sensor and a conventional video camera for obstacle detection is presented. The system is intended to form a non-intrusive virtual barrier at both sides of an intelligent wheelchair, in order to protect the user in everyday outdoor and indoor environments, like office, home, or pedestrian areas. In this type of environments, the shape of the obstacles is very heterogeneous (for instance, having a variable width along their height), so their detection via the conventional sensors installed in the wheelchair presents difficulties, especially in the most exposed areas of the user that are the sides of their torso. With the proposed system, when an obstacle intersects a beam, the intersection point is projected in the associated image and optical flow is calculated at both sides of this point. Using the optical flow, several classifiers have been trained and tested in order to automatically discern between intersections produced by the user and those produced by external obstacles. Results show that the method accurately detects the presence of obstacles and the direction of their movement.