Automatic guided vehicle system and method for navigating automatic guided vehicle

• US 6,246,930 B1
• Filed: 04/13/1999
• Issued: 06/12/2001
• Est. Priority Date: 08/06/1998
• Status: Expired due to Fees

• Current Assignee: Murata Machinery Limited (Muratec)
• Original Assignee: Murata Machinery Limited (Muratec)
• Inventors: Hori, Kikuo
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Hernandez, Olga
• Application Number:
  US09/290,422
• Time in Patent Office: 791 Days
• Field of Search: 701/23, 701/26, 701/2, 701/11, 342/118, 342/126, 342/46, 342/47, 340/901, 340/933, 340/988, 340/425.5
• US Class Current: 701/23
• CPC Class Codes: G05D 1/0236 in combination with a laser lasers per se H01S

Abstract

A plurality of reflectors are disposed along a travelling path, an automatic guided vehicle is started up at a position where a laser scanner can recognize four or more reflectors, and data on the angles and distances of the reflectors is obtained. When the first reflector is recognized, there are N possible hypotheses that would specify the reflectors. When a second reflector is recognized, the distance to the first reflector is rational, therefore, there are kN possible hypotheses (k is 10 or less). When a third reflector is recognized, the triangle formed by the three reflectors cioncides with that on a reflector map, therefore, there are mN possible hypotheses (m<1). Then, the present position is estimated according to mN possible hypotheses. The fourth reflector is recognized and the conformity is checked, the present position of the automatic guided vehicle is specified. Its error rate is about equal to the standard deviation obtained from angular resolution/360 degrees x distance resolution/distance between the reflectors. To enable an automatic guided vehicle to be started up without initial position data.

Claims

1. A method for navigating an automatic guided vehicle comprising;

disposing a plurality of reflectors along a travelling path;

recognizing an orientation and a distance of at least three reflectors;

temporarily determining said reflectors by comparing the recognized distance with a reflector map storing positions of the reflectors along the travelling path;

obtaining a present position of the automatic guided vehicle on the basis of the temporarily specified reflector; and

obtaining the present position by confirming the temporarily obtained present position from the recognition values of the fourth and subsequent reflectors.

2. An automatic guided vehicle system comprising:

a plurality of reflector disposed along a travelling path;

an automatic guided vehicle including laser scanner for obtaining an orientation and a distance of the reflectors;

a reflector map storing positions of the reflectors along the travelling path;

a means for determining temporary specification of three reflectors by comparing recognition values of distances with respect to the recognized three reflectors with the reflector map; and

a means for obtaining a present position of the automatic guided vehicle based on the temporary specification.

3. The automatic guided vehicle system as claimed in claim 2, further comprising a means for checking conformity of said temporary specification based on a recognition values of fourth and subsequent reflectors.