JP2008009533A - Position detection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detection system easily correcting the current position and azimuth of a mobile object only by detecting one reference mark. <P>SOLUTION: Passages A and B extending east and west and passages C-E extending north and south are formed in a warehouse 1. The positions of RFID tags 3 and the azimuths of the passages A-E having the RFID tags 3 are associated and stored in a tag information storage section in response to the ID information of each RFID tag 3. When a position calculation section determines the current position of a forklift 2 with a dead reckoning technology during operation of the forklift 2, and a reader reads the ID information of the RFID tag 3, a calibration section reads the tag position and passage azimuth associated with the ID information from the tag information storage section, and inputs, into the position calculation section, the tag position and passage azimuth as the current position and azimuth of the forklift 2, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a position detection system, and more particularly to a system for detecting the position of a moving body such as a forklift.

In recent years, for mobile units such as forklifts, the position detection system detects the position of the mobile unit every predetermined time, and based on the detection results, grasps the operating status of the mobile unit, analyzes the travel route, etc., and improves work efficiency. It is hoped that
For example, a position detection system that detects the position of a moving body by receiving radio waves from GPS satellites is known. However, because it is difficult to receive radio waves from GPS satellites indoors, work indoors. There is a problem that this position detection system cannot be applied to a moving object to be performed.

On the other hand, as a position detection system capable of grasping the position of a moving object outdoors or indoors, a system using dead reckoning technology is widely known. In this system, the moving distance of the moving object from the coordinates of the known position and the azimuth angle of the moving object with respect to a preset reference direction are measured, and the moving object is measured based on the measured moving distance and azimuth angle. The coordinates of the current position are obtained by calculation.
However, it is generally known that the value obtained using this dead reckoning technique includes an error, and therefore, it is between the calculated current position of the moving body and the actual current position of the moving body. Misalignment will occur.

  Thus, for example, in the position detection system disclosed in Patent Document 1, a plurality of reference marks are arranged at intervals on the floor surface on which the moving body moves, and each reference mark is detected by the detection unit of the moving body. The coordinates of the current position of the moving object are calibrated based on the coordinates of the position where the reference mark is installed. Further, based on the measurement results by the gyro, the steering angle sensor, the movement distance sensor, etc. from when one reference mark is detected until the next reference mark is detected, the coordinates of the positions of these two reference marks, and the like The azimuth angle of the moving body is calculated, and the azimuth value of the moving body is calibrated based on the calculated value.

JP 2000-89827 A

However, in the position detection system of Patent Document 1 described above, an accurate azimuth angle of the moving object is calculated by detecting two reference marks. For example, the moving object stops after detecting one reference mark. If it takes time until the next reference mark is detected, an error occurs in the measured value of the gyro between the detection of one reference mark and the detection of the next reference mark due to gyro drift or the like. The accurate azimuth angle of the mobile object may not be calculated.
Further, in Patent Document 1, an accurate azimuth angle of the moving body cannot be calculated until two or more reference marks are detected. Therefore, an operator or the like needs to set an initial azimuth angle of the moving body. is there.
The present invention has been made to solve such problems, and provides a position detection system that can easily calibrate the current position and azimuth angle of a moving object by detecting only one reference mark. With the goal.

  The position detection system according to the present invention includes a plurality of reference marks that are spaced apart from each other along a predetermined path for moving the moving body and each have unique ID information, and are attached to the moving body. And a reader for reading the ID information of the reference mark, and for each reference mark ID information, the mark position where the reference mark is arranged and the path azimuth corresponding to the path where the reference mark is arranged When the ID information of the reference mark is read by the reader, the mark information storage unit for storing the reference mark, the position calculation unit for calculating the current position of the moving object based on the azimuth and the moving distance of the moving object, The path azimuth and mark position related to information are read from the mark information storage unit, and the path azimuth and mark position are moved respectively. Azimuth of and in which and a calibration unit for inputting the position calculation unit as the current position.

  In addition to a traveling direction sensor for detecting the traveling direction of the moving body, the mark information storage unit stores two azimuth angles corresponding to the passage where the reference mark is arranged as the passage azimuth, and the calibration unit The azimuth angle is selected from two azimuth angles based on the moving direction detected by the moving direction sensor, and the azimuth angle is input to the position calculation unit as the azimuth angle of the moving body. You can also.

  According to the present invention, it is possible to easily calibrate the current position and azimuth angle of the moving body by detecting only one reference mark.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows a warehouse 1 to which a position detection system according to an embodiment of the present invention is applied. A plurality of passages A to E are formed inside the warehouse 1, and the forklift 2 as a moving body arbitrarily travels on the plurality of passages A to E to convey the load. Has been. Among the plurality of passages A to E, the passages A and B are formed so as to extend in the east-west direction, respectively, and the passages C to E are formed so as to extend in the north-south direction, respectively.
A plurality of RFID tags 3 are arranged as reference marks on the floors of the passages A to E, respectively, and the plurality of RFID tags 3 are arranged at intervals from each other along the passages A to E. ing. In each RFID tag 3, ID information unique to the RFID tag 3 is written.

As shown in FIG. 2, the forklift 2 includes a position calculation unit 4 that calculates the current position of the forklift 2 using dead reckoning technology, and a calibration unit 5 that is electrically connected to the position calculation unit 4. Have. The position calculation unit 4 is electrically connected to an angular velocity sensor 6 including a gyro for measuring the angular velocity of the forklift 2 and a distance meter 7 including an encoder for measuring the moving distance of the forklift 2. The calibration unit 5 detects a traveling direction of the forklift 2 and a reader 8 for reading the ID information of the RFID tag 3, a tag information storage unit 9 for storing information corresponding to the ID information of the RFID tag 3, and the forklift 2. A traveling direction sensor 10 made of an electronic compass or the like is electrically connected to each other.
The traveling direction sensor 10 detects the direction in which the forklift 2 is traveling, and may be any sensor that can detect, for example, which direction is east, west, south, or north. The position calculation unit 4 includes a timer (not shown).

Here, in the warehouse 1, a two-dimensional coordinate system with a certain point as the origin O is set and a reference direction is set, and the position and azimuth angle in the warehouse 1 are recognized based on them. Can do.
In addition, the tag information storage unit 9 corresponds to the ID information of each RFID tag 3, the coordinates of the tag position where the RFID tag 3 is disposed, and the paths A to E where the RFID tag 3 is disposed. The azimuth is stored in association with each other. The tag information storage unit 9 stores two azimuth angles corresponding to the extending directions of the passages A to E in which the RFID tag 3 is disposed as the passage azimuth angle.
In addition, here, for example, when the east direction is set as a reference direction (0 °), in the RFID tag 3 located in the passages A and B, the east-west that is the extending direction of the passages A and B is the ID information Two azimuth angles of 0 ° and 180 ° corresponding to the direction are stored in association with each other. Further, in the RFID tag 3 located in the passages C to E, two azimuth angles of 90 ° and 270 ° corresponding to the north-south direction, which is the extending direction of the passages C to E, are stored in association with the ID information. Is done.

  Next, the operation of the position detection system according to the embodiment of the present invention will be described. The forklift 2 arbitrarily travels in the plurality of passages A to E to carry the load. During the operation of the forklift 2, the position calculation unit 4 of the forklift 2 uses the dead reckoning navigation technique at a predetermined very short period T based on the azimuth angle θ and the movement distance ΔL of the forklift 2 to determine the current position (X, Y ) As follows. Note that the azimuth angle θ of the forklift 2 represents an angle formed by the direction in which the forklift 2 is currently traveling with respect to a preset reference direction, and the moving distance ΔL of the forklift 2 is the current value of the previous forklift 2. It is assumed that the distance traveled by the forklift 2 during the period T from when the position is obtained to the present is represented.

First, the angular velocity of the forklift 2 measured by the angular velocity sensor 6 is multiplied by a period T to calculate the displacement amount Δθ of the azimuth angle of the forklift 2. Next, as shown in the following equation (1), the current azimuth angle θ of the forklift 2 is calculated by adding the displacement amount Δθ of the azimuth angle of the forklift 2 to the previous azimuth angle θ1 of the forklift 2. To do.
θ = θ1 + Δθ (1)

From the azimuth angle θ of the forklift 2 calculated by the equation (1) and the movement distance ΔL of the forklift 2 measured by the distance meter 7, the movement amounts dX and dY of the forklift 2 in the X-axis direction and the Y-axis direction are
dX = ΔL cos θ (2)
dY = ΔLsin θ (3)
It is expressed.

DX and dY are calculated from the above formulas (2) and (3), and these dX and dY are respectively calculated as shown in the following formulas (4) and (5). The current position (X, Y) of the forklift 2 is calculated by adding to the position coordinates (X1, Y1).
X = X1 + dX (4)
Y = Y1 + dY (5)
In this way, the current position (X, Y) of the forklift 2 can be obtained by the position calculation unit 4.

On the other hand, when the ID information of the RFID tag 3 is read by the reader 8 of the forklift 2, the ID information is input to the calibration unit 5. At this time, as shown in the flowchart of FIG. 3, the calibration unit 5 firstly determines the coordinates of the tag position related to the ID information based on the ID information of the RFID tag 3 input from the reader 8 in step S1. Two azimuth angles as passage azimuth angles are read from the tag information storage unit 9.
For example, when the reader 8 reads the ID information of the RFID tag 3 located in the passages A and B extending in the east-west direction, the coordinates of the tag position where the RFID tag 3 is arranged and the extension of the passages A and B are shown. Two azimuth angles of 0 ° and 180 ° corresponding to the current direction are read out. On the other hand, when the reader 8 reads the ID information of the RFID tag 3 located in the passages C to E extending in the north-south direction, the coordinates of the tag position where the RFID tag 3 is arranged and the length of the passages C to E are extended. Two azimuth angles of 90 ° and 270 ° corresponding to the current direction are read out.

Next, in step S <b> 2, the calibration unit 5 selects one azimuth angle from two azimuth angles as passage azimuth angles based on the traveling direction of the forklift 2 detected by the traveling direction sensor 10. At this time, the calibration unit 5 selects the one closer to the traveling direction of the forklift 2 detected by the traveling direction sensor 10 out of the two azimuth angles as the passage azimuth angle.
In step S3, the calibration unit 5 inputs the selected one azimuth angle and the coordinates of the tag position to the position calculation unit 4 as the azimuth angle and the current position of the forklift 2, respectively.
Thus, the current position and azimuth angle of the forklift 2 of the position calculation unit 4 are calibrated by the calibration unit 5.

Therefore, the position calculation unit 4 obtains the current position (X, Y) of the forklift 2 based on the coordinates and azimuth of the position input from the calibration unit 5 in this way at the next calculation.
That is, when calculating the current azimuth angle θ of the forklift 2, the position calculation unit 4 calculates the azimuth angle input from the calibration unit 5 as the previous azimuth angle θ1 of the forklift 2 and inputs the equation (1). When calculating the current position (X, Y) of the forklift 2, the coordinates of the position input from the calibration unit 5 are the coordinates (X1, Y1) of the current position of the forklift 2 the previous time (4) And it inputs into (5) and calculates.

As described above, in this position detection system, not only the position of the forklift 2 but also the azimuth angle can be calibrated only by reading one RFID tag 3 as a reference mark. Therefore, the calibration can be easily performed as compared with the conventional case where the two azimuths of the forklift 2 are detected and calibrated by detecting the two reference marks.
Further, in this position detection system, the accurate current position and azimuth angle of the forklift 2 can be immediately grasped at the time when one RFID tag 3 is detected without setting an initial azimuth angle by an operator or the like. .
Further, in this position detection system, the azimuth angle of each passage A to E is used as the azimuth angle of the forklift 2 traveling along the passages A to E, so that the forklift at the point where each RFID tag 3 is disposed. The azimuth angle of 2 can be easily grasped.

Further, since the current position of the forklift 2 is calculated and obtained by dead reckoning technology based on the azimuth angle and the moving distance of the forklift 2, and calibration is performed by reading the ID information of the RFID tag 3, the forklift can be accurately used both outdoors and indoors. Thus, it is possible to detect a current position of 2 and to thereby realize a position detection system having high reliability.
Further, the current position of the forklift 2 detected at a predetermined cycle by the position detection system is accumulated in the forklift 2, or is transmitted and accumulated from the forklift 2 to the management server by wireless or the like, and based on the accumulated information. Thus, the work efficiency can be improved by grasping the operating status of the forklift 2 and analyzing the travel route.

  In the above-described embodiment, the position calculation unit 4 always uses the azimuth angle of the forklift 2 input from the calibration unit 5 to the position calculation unit 4 when reading the RFID tag 3 without using the angular velocity sensor 6. The current position of the forklift 2 may be calculated. In this way, since it is not necessary to provide the angular velocity sensor 6, the manufacturing cost of this position detection system can be reduced.

  In the above-described embodiment, the tag information storage unit 9 stores two azimuth angles corresponding to the extending directions of the passages A to E in which the RFID tag 3 is disposed as the passage azimuth angle. For example, when the direction in which the forklift 2 travels in each of the passages A to E is limited to one direction in advance, the tag information storage unit 9 uses this as the passage azimuth. One azimuth angle representing one direction may be stored in advance. In this case, the traveling direction sensor 10 is provided because it is not necessary to select one of the two azimuth angles based on the traveling direction of the forklift 2 detected by the traveling direction sensor 10 as in the above-described embodiment. There is no need, and therefore the manufacturing cost can be further reduced.

  Instead of the RFID tag 3, a bar code, a magnetic body, an infrared ID, or the like can be used as a reference mark.

Further, in the embodiment, the passages A and B are formed to extend in the east-west direction and the passages C to E are formed to extend in the north-south direction, but are not limited to these passages A to E. Any path may be used as long as it is set in advance as a travel path on which the forklift 2 travels. For example, even if a passage that obliquely crosses the warehouse 1 is formed, the position of the forklift 2 that travels on the passage can be detected using this position detection system.
In addition, the position detection system can be used effectively not only in the warehouse 1 but also in a factory or other various facilities as long as a passage where the forklift 2 travels is set in advance.

  In the above-described embodiment, the position of the forklift 2 is detected as a moving body. However, the present invention is not limited to this, and the present invention is not limited to this, as long as it is a moving body that moves on a preset path. The position can be detected using the position detection system. For example, a hand cart can be used as the moving body.

It is a top view which shows the structure in the warehouse where the position detection system which concerns on embodiment of this invention was applied. It is a block diagram which shows the position detection system which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the calibration part in embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Warehouse, 2 Forklift, 3 RFID tag, 4 Position calculation part, 5 Calibration part, 6 Angular velocity sensor, 7 Distance meter, 8 Reader, 9 Tag information storage part, 10 Travel direction sensor, AE path.

Claims (2)

A plurality of fiducial marks that are spaced apart from each other along a predetermined path for the mobile body to move and each have unique ID information;
A reader attached to the moving body and for reading the ID information of the reference mark;
For each reference mark ID information, a mark information storage unit that stores a mark position where the reference mark is disposed and a passage azimuth corresponding to the passage where the reference mark is disposed;
A position calculation unit that calculates the current position of the moving object based on the azimuth and moving distance of the moving object;
When the ID information of the reference mark is read by the reader, the passage azimuth and the mark position related to the ID information are read from the mark information storage unit, and the passage azimuth and the mark position are respectively read from the moving body. And a calibration unit that inputs the azimuth angle and the current position to the position calculation unit.   Further comprising a traveling direction sensor for detecting the traveling direction of the moving body, the mark information storage unit stores two azimuths corresponding to the passage where the reference mark is arranged as the passage azimuth, The calibration unit selects one azimuth angle from the two azimuth angles based on the traveling direction of the moving body detected by the traveling direction sensor, and uses the azimuth angle as the azimuth angle of the moving body. The position detection system according to claim 1, wherein the position detection system is input to.

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