Extensive Ultrasonic Local Positioning System for navigating with mobile robots

This paper presents an extensive local ultrasonic positioning system for mobile robots (MRs) based on the fusion of the information from the MR internal odometer sensor and the measurements of position obtained with a set of external ultrasonic beacons that form an Ultrasonic Local Positioning System (ULPS). The extensive ULPS is formed using several single ULPS, each one of them covering a particular area of the total working area. In each single ULPS, five ultrasonic beacons are used that emit simultaneously and are detected by an ultrasonic receiver on board the MR. Direct Sequence Code Division Multiple Access (DS-CDMA) techniques have been used to avoid interferences between them. When the MR navigates on the working area, it continuously obtains its relative position thanks to the internal odometer. The cumulative errors of the odometer are corrected when the robot is on a place where the positioning data obtained with any of the single ULPS are available. The fusion of information (from odometer and ULPS) is made using an H-Infinite filter. The extensive ULPS has been built and tested experimentally.