Omni-Directional Power Assisted Cart with Collision Avoidance Function

This paper describes an omni-directional power assisted cart with a collision avoidance function. At each four corner of the vehicle, we installed two ultrasonic sensors, one directed to the side of the vehicle and on along its diagonal. There are three features. (1) The distance sensed by the front-side ultrasonic sensors is memorized. As the relative displacement of the cart can be calculated, it is possible to incrementally built-up the topology of the surrounding environment of the cart and thus follow the position of obstacles even in the areas where no ultrasonic sensors have been installed. (2) It is possible to set up the position of the rotation center of the vehicle by adapting its control laws. Collision with obstacles in the in-course and out-course of the vehicle can be avoided by shifting the rotation center. (3) The collision can be avoided in the forward, backward and side directions by, first, slowing down the cart and then eventually stopping it. These three capabilities enabled us to reduce the number of ultrasonic sensors to the minimum necessary (8 pieces) ; and also to ensure comfortable conditions of use to the user even if one of the sensors performs a wrong measurement.