Precision Improvement of Position Measurement Using Two Ultrasonic Land Markers

Abstract

We have been developing a position measurement system for navigation of automated guided vehicles (AGVs) called SPARS. In this system, the AGV’s ultrasonic position measurement module communicates via ultrasonic waves with ultrasonic transponders that serve as land markers on a path to measure its relative position during travel. In previous studies, we conducted experiments and introduced improvements using the relative position between the AGV and land marker estimated from position information from a single land marker. It was found, however, that the ultrasonic communication S/N ratio decreases, lowering position accuracy, when the land marker distance and its direction angle are great. To solve this problem and improve accuracy, we examine position measurement based on distance information from two land markers.