Four strategically-placed Polaroid vergence sonar pairs on an electric scooter are controlled by a PIC16877 microcontroller interfaced to the joystick and the wheelchair controller. The sonar vergence pair below the foot stand determines if the obstacle is to the left or right. A sonar vergence pair on each side of the chair (at knee level) determines if the chair can pass by an obstacle without collision. A right-side-looking vergence pair maintains the distance and a parallel path to the wall. When sonar detects obstacles, the user
joystick commands are overridden to avoid collision with those obstacles. The blindfolded user navigates a cluttered hallway by holding the joystick in a constant forward position.
