Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Automatic route guidance vehicle
Reexamination Certificate
1999-04-20
2001-03-27
Zanelli, Michael J. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Automatic route guidance vehicle
C701S025000, C180S169000
Reexamination Certificate
active
06208916
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a navigating system for an automatic guided vehicle, and in particular, to the specification of a reflector without temporarily determining the present position of the automatic guided vehicle.
BACKGROUND OF THE INVENTION
In the prior art, there is a system in which a plurality of reflectors are disposed along the travelling path, and the reflectors are recognized by means of a laser scanner on an automatic guided vehicle to calculate their present position. When three reflectors can be recognized, the present position can be calculated using the principle of triangulation, therefore, the problem with this approach is that concerning whether such recognized reflector is to be specified which of the reflectors on the reflector map. In this case, this problem can be easily solved by assigning identification data such as bar codes to the reflectors, however, such reflectors are expensive and require much time to install. Therefore, in general, the reflectors must be identical.
In order to specify a reflector without assigning identification data to the reflector itself, the start position of an automatic guided vehicle is input to the automatic guided vehicle. First, presuming that the automatic guided vehicle starts from a known position, the recognized reflector is specified at the starting time. In subsequent recognition, the present position is assumed based on the previous recognized position, and to specify the reflectors, the laser scanner is assumed to have recognized those reflectors that can be recognized at the present position. However, when using this technique, if a reflector is incorrectly recognized, it becomes impossible to recognize the exact position of the automatic guided vehicle, thus making it uncontrollable.
It is an object of the present invention to specify reflectors without temporarily determining the present position of the automatic guided vehicle.
It is an additional object of the present invention to enable even newly appeared reflectors to be specified.
It is an additional object of the present invention to have a capability of determining the velocity and angular velocity of the automatic guided vehicle, as well as its position and orientation.
SUMMARY OF THE INVENTION
The present invention is an automatic guided vehicle system characterized by comprising a large number of reflectors arranged along a travelling path, a laser scanner provided in an automatic guided vehicle to determine the orientation of each reflector by means of periodic scanning, a reflector map, a means for storing the results of the specification of reflectors based on the previous scanning, a means for specifying reflectors recognized during the present scanning by determining a reflector located within a predetermined angle relative to the results of the previous recognition to be the same as the previous recognized reflector, and a means for determining the present position of the automatic guided vehicle based on the specified reflectors.
Preferably, the laser scanner determines the orientation of and the distance to the reflector, and the specifying means is configured to specify a newly appeared reflector using the reflector map and the distance relationship between the newly appeared reflector and the specified reflectors.
In addition, preferably, the velocity and angular velocity of the automatic guided vehicle are determined from at least three specified reflectors, and the velocities and angular velocities determined from a previously recognized position until the present time are integrated to determine the present position and orientation.
According to the present invention, the results of the specification of reflectors based on the previous scanning are stored, and reflectors recognized by the present scanning are specified by determining a reflector located within a predetermined angle relative to the results of the previous recognition to be the same as the previous recognized reflector. Preferably, the preceding scanning is used as the previous scanning. The present invention compares the previous recognized value with the present recognized values by means of the laser scanner, and to specify reflectors, treats similar recognized values as the same reflectors, thereby enabling the reflectors to be specified very promptly and easily. In this way, reflectors can be accurately specified.
The present invention also specifies a newly appeared reflector by using the distance relationship between the newly appeared reflector and the specified reflectors, and referencing the reflector map. This configuration enables the newly appeared reflector to be specified without temporarily determined the present position of the automatic guided vehicle.
Furthermore, the present invention uses the results of the recognition of three reflectors to determine the velocity and angular velocity of the automatic guided vehicle in order to determine its present position and orientation. Thus, compared to the determination of the present position and orientation based on the assumption that the automatic guided vehicle is stationary, this configuration can improve recognition accuracy, and in addition, even if a velocity sensor or an angular velocity sensor is provided on the automatic guided vehicle, the velocity or angular velocity can be determined independently of such sensors.
REFERENCES:
patent: 4811228 (1989-03-01), Hyyppa
patent: 5187662 (1993-02-01), Kamimura et al.
patent: 5367458 (1994-11-01), Roberts et al.
patent: 6012003 (2000-01-01), Angstrom
patent: 8-152323 (1996-06-01), None
Armstrong Westerman Hattori McLeland & Naughton LLP
Murata Kikai Kabushiki Kaisha
Zanelli Michael J.
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