Camera-laser projector stereo system based anti-collision system for robotic wheelchair users with cognitive impairment

This paper presents a camera-laser projector based system for the real-time estimation of distance to obstacles designed to assist wheelchair users with cognitive impairment. Upon falling under the specified safe distance to an obstacle an alarm alerts that it can be used by the control system to act immediately to avert a possible collision even before the user stops the wheelchair. This system consists of a fisheye camera, which allows to cover a large field of view (FOV) to enable the pattern to be available at all times, and a laser circle projector mounted on a fixed baseline. The approach uses the geometrical information obtained by the projection of the laser circle onto the plane simultaneously perceived by the camera. We show a theoretical study of the system in which the camera is modelled as a sphere and show that the estimation of a conic on this sphere allows to estimate the distance between wheel chair and obstacle. We propose some experiments based on simulated data followed by real sequences. The estimated distances from our method are comparable with commercial sensors in terms of its accuracy and correctness. The results from our cheaper system over the expensive commercial sensors prove its suitability for a cheap wheelchair able to assist users with cognitive impairments. The proposed solution is functional in low light to dark environments, where the decision making can be a challenge by the user.