Off-line localisation of a mobile robot using ultrasonic measurements

Regarding assistance to disabled people for object manipulation and carryin g, the paper focuses on the localisation for mobile robot autonomy. In orde r to respect strong low-cost constraints, the perception system of the mobi le robot uses sensors of low metrological quality, ultrasonic ring and odom etry. That poses new problems for localisation, in particular. Among differ ent localisation techniques, we present only off-line localisation. With po or perception means, it is necessary to introduce a priori knowledge on sen sors and environment models. To solve the localisation problem, the ultraso nic image is segmented applying the Hough transform, well-adapted to ultras onic sensor characteristics. The segments are then matched with the room, m odelled and assumed to be rectangular. Several positions are found. A first sort, based on a cost function, reduces the possibilities. The remaining a mbiguities are removed by a neural network which plays the part of a classi fier detecting the door in the environment. Improvements of the method are proposed to take into account obstacles and nonrectangular room. Experiment al results show that the localisation operates even with one obstacle.