Robotic Sensing for the Guidance of the Visually Impaired

This paper describes ongoing work into a portable mobility aid, worn by the visually impaired. The system uses stereo vision and sonar sensors for obstacle avoidance and recognition of kerbs. Because the device is carried, the user is given freedom of movement over kerbs, stairs and rough ground, not traversable with a wheeled aid. Motion of the sensor due to the walking action is measured using a digital compass and inclinometer. This motion has been modelled and is tracked to allow compensation of sensor measurements. The vision obstacle detection method uses comparison of image feature disparity with a ground feature disparity function. The disparity function is continually updated by the walk-motion model and by scene ground-plane fitting. Kerb detection is achieved by identifying clusters of parallel lines using the Hough transform. Experimental results are presented from the vision and sonar parts of the system.