Ultrasonic data representation: application to mobile robots localisation

A method with a new representation of ultrasonic data is proposed in order to calculate the position and the orientation of a robot placed in a room. This representation is based on occupancy grids. Two grids are necessary to locate the robot. The first one is the global map which stores all the information of the environment. The second one is the local map which enables to store the information around the robot obtained by the use of ultrasonic sensors. The two grids are compared to determine their relative translation and rotation. This paper deals with the improvement of occupancy grids by a finest analysis of the cells affected along the arc, those situated simultaneously in two different cones and those included in the robots area. Tests have been achieve to evaluate this discretisation which proves its effectiveness.