Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Automatic route guidance vehicle
Reexamination Certificate
2000-02-22
2001-07-03
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Automatic route guidance vehicle
C701S069000, C701S210000, C318S568120, C180S168000
Reexamination Certificate
active
06256560
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an automated-guided vehicle (hereinafter referred to as “AGV”) system, and more particularly, to a method for correcting a stop position of the AGV and an apparatus therefor.
BACKGROUND OF THE INVENTION
Automated-guided vehicles are usually used in severe environments where a worker has a difficulty or an inefficiency in direct performance of a task. That is, the AGVs transfer articles or carry out a predetermined task by a manipulator through an automatic control, while stopped at work stations provided along a predetermined travelling path.
FIG. 1
is a perspective view of a conventional AGV, and
FIG. 2
is a top plan view of the AGV located on a travelling path, for illustrating a conventional method for correcting a stop position of the AGV.
The AGV is formed with a vehicle body
51
and a manipulator
52
mounted on the top of the vehicle body
51
for carrying out a predetermined task. Under both sides of the vehicle body
51
a pair of drive wheels
53
are installed for driving the AGV. Wheel driving motors
55
for driving the drive wheels
53
are installed beside the drive wheels
53
. In the front and rear ends of the vehicle body
51
a pair of track sensors
57
are installed for detecting electromagnetic waves from a travelling direction mark (not shown) on the travelling path
70
. A controller (not shown) controls the wheel driving motors
55
and determines the travelling direction of the AGV, according to the values of the electromagnetic waves detected by the track sensors
57
.
On the travelling path
70
a stop mark
75
made of magnetic material is attached at the point or workplace at which the AGV has to stop. On the bottom of the vehicle body
51
a stop sensor
60
is installed for sensing a magnetic field from the stop mark
75
. On one lateral side of the vehicle body
51
first and second sensor groups
62
and
64
are installed along the longitudinal direction of the vehicle body
51
. Each of the first and second sensor groups
62
is comprised of a plurality of ultrasonic wave sensors. On a side wall
71
installed beside the travelling path
70
of the AGV, first and second reflectors
72
and
74
are installed for reflecting ultrasonic waves from the sensor groups
62
and
64
. The first and second reflectors
72
and
74
are installed with the same interval as that of the first and second sensor groups
62
and
64
and at the same height as that of these sensor groups
62
and
64
, to correspond to each other.
With this configuration, when the AGV stops according to the signal that the stop mark
75
is detected from the stop sensor
60
, ultrasonic waves are (a) generated from the first and second sensor groups
62
and
64
, (b) reflected by the first and second reflectors
72
and
74
, and (c) then returned to the first and second sensor groups
62
and
64
. The controller determines an actual stop position of the AGV based on the strength of the returned ultrasonic waves.
More particularly, coordinates are set initially wherein the center of the vehicle body
51
is the origin (
0
), the travelling path
70
is a Y-axis, and the perpendicular axis to the Y-axis and passing through the origin is an X-axis. Then, the distance a between the first sensor group
62
and the first reflector
72
on the X-axis, and the distance b between the second sensor group
64
and the second reflector
74
on the X-axis, are calculated. These distances a and b can be obtained by multiplying the speed of the ultrasonic waves by the time consumed in returning to the sensor groups. The angle &thgr; by which the vehicle body
51
deviates from the travelling path
70
is obtained by using the difference a−b between a and b and the distance d between the first and second sensor groups
62
and
64
.
To determine how far the vehicle body
51
is deviated from the stop mark
75
in the travelling direction thereof, a distance c between the sensor group
62
or
64
and the reflector
72
or
74
on the Y-axis is calculated. The distance c can be calculated by using the strength of the ultrasonic waves generated by the sensor group
62
or
64
and returned thereto after reflecting from the reflector
72
or
74
.
According to the actual stop position of the vehicle body
51
of the AGV determined as described above, the controller controls the wheel driving motors
55
and relocates the vehicle body
51
at a predetermined correct working position.
However, in the conventional AGV position correcting method, a multiplicity of ultrasonic wave sensors are required, thereby raising the cost of production. Further, since the reflectors
72
and
74
have to be installed corresponding to the ultrasonic wave sensor groups
62
and
64
of the AGV, the work of installation is complicated.
In the conventional art, after relocation of the vehicle body
51
is conducted according to the value calculated from the comparison of the actual stop position of the vehicle body
51
and the predetermined correct stop position of the vehicle body, the manipulator carries out the predetermined work. Therefore, the AGV has to be inactive until the relocation of the vehicle body
51
is finished, thereby increasing an overall time for completing the task.
With the conventional art using the ultrasonic waves sensors, only a relative position of the vehicle body
51
to the travelling path is determined. Therefore, an extra device is needed to determine a reference position by which a correct working position of the vehicle body on the travelling path is taught, thereby increasing the cost of production.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method for correcting an actual stop position of an AGV and an apparatus therefor in which a predetermined reference position on a travelling path at a workplace and an actual stop position of the AGV relative to the reference position are easily detected.
Another object of the present invention is to provide a method for correcting an actual stop position of an AGV and an apparatus therefor in which a reference position and an actual stop position of the AGV relative thereto are determined at the same time, by which an actual stop position of a vehicle body of the AGV or an actual stop position of a manipulator mounted on the AGV can be easily corrected.
Still another object of the present invention is to provide a method for correcting an actual stop position of an AGV and an apparatus therefor in which a reference position and an actual stop position of the AGV relative thereto are determined, and at the same time, an actual stop position of a vehicle body of the AGV or an actual stop position of a manipulator mounted on the AGV can be corrected.
To accomplish the objects, according to one aspect of the present invention, there is provided a method for correcting an actual stop position of an AGV for carrying out a task while the AGV is stopped at a workplace located along a travelling path for the AGV, comprising the steps of: a) establishing at least one reference position at the workplace which serves as a reference for determining an actual stop position of the AGV stopped at that workplace on the travelling path; b) ascertaining the reference position of the workplace where the AGV actually stops, based on image data at the actual stop position, and calculating a difference between the reference position and the actual stop position; c) ascertaining whether the difference is within an allowable limit of a predetermined reference value; and d) controlling the AGV to make the difference within the allowable limit of the predetermined reference value if the difference is not within the allowable limit.
Preferably, a position of a vehicle body of the AGV or a manipulator mounted on the AGV is corrected in the step (d). Preferably, the reference value is an offset value of the reference position corresponding to a predetermined correct working position for the AGV, relative to the correct working position.
Preferabl
Kal Myung-joon
Kim Jin-Ki
Arthur Gertrude
Cuchlinski Jr. William A.
Larson & Taylor PLC
Samsung Electronics Co,. Ltd.
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