A high precision ultrasonic docking system used for automatic guided vehicle

With the more and more wide applications of automatic guided vehicle (AGV) in the material handling of modem manufactory system, its docking techniques have drawn extensive attention. The objective of this paper is to investigate the ultrasonic sensor based AGV 2D docking. As an established and cost-effective method, the application of classic ultrasonic sensor still faces certain drawbacks, e.g., low accuracy. In the present work, a novel high-precision, low-cost ultrasonic docking system is developed to locate the AGV relative to the docking workstation. In the proposed scheme, with electromagnetic wave used as system synchronization to trigger the time of flight (TOF) counter, the docking system consists of the ultrasound reception and emission beacons positioned at the same height of docking workstation and AGV, respectively. The 2D position of AGV is obtained from the TOF of ultrasonic signal from the emitter to two receivers. To ensure docking accuracy on low-cost narrow bandwidth ultrasonic transducer, a transducer equalizer based on the adaptive training algorithm is employed to realize high ranging precision (1 mm). Experimental results obtained on a demo AGV are presented and discussed, confirming the validity of the proposed solution, with an AGV docking precision of around +/-3 = mm x and y, +/-1degrees in bearing. (C) 2004 Elsevier B.V. All rights reserved.