In this paper, we present a modular method of environment perception for a mobile robot by local mapping. This map building process is done in order to authorize the motions of a mobile robot in unknown indoor environment. To validate it, we have implemented a reactive navigation on a mobile robot which perceives its near environment with two range finders. The map building process is the cluster of several functions: sort of measures in subsets, model of these subsets, elaboration of a map, and updating it with previous measures. Furthermore this process must be quick and sufficiently robust to deliver in real time a safe map to the robot.

An autonomous mobile robot needs externals sensors for its own localization and modeling environment. In order to perform the angular precision of ultrasonic sensor and to improve the number of informations for a given time, we developed an ultrasonic sensor network using the multiple receivers mode. In this paper we introduce the ultrasonic network with its hardware architecture and its functioning mode. We also present a method to localize an echo source with the multiple receivers mode and show how to simply model this echo in the robot frame. We then describe the extraction of environment primitives (segment) by the inertia matrix and Hough transform. Finally, we validate the all process by experiments.