Autonomous/semi-autonomous navigation system of a wheelchair by active ultrasonic beacons

This paper describes the autonomous and semi-autonomous navigation system of a powered wheelchair for disabled people and nursing staffs. In order to detect its position reliably, this system utilizes active ultrasonic beacons on ceiling. 2 receivers on a wheelchair measure the time-of-flight of the ultrasonic pulses from 2 beacons. Since the distances from only 1 beacon can be obtained at once, the position should be dynamically estimated with its movement in a measurement interval during navigation. Three types of navigation mode by this positioning system are also proposed to assist users. "Automatic transfer mode" guides a wheelchair to a target position autonomously. "Operation assistance mode" helps a user's operation by moving a wheelchair straight toward a commanded direction. "Selective semi-automatic mode" runs path networks selecting a desired direction at each branch point. These navigations were successful in practice.