JP2008180665A - Position detection system. - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detection system capable of accurately detecting the position of an object even when the same obstacle is interposed between the object and the receiver or between a plurality of positions whose positions have been confirmed in advance and the receiver. To provide.
A first signal from a tag RFt attached to an object 2 to be position-detected, a second signal from reference tags RFa to RFe at a plurality of positions whose positions have been confirmed in advance, and a first signal Three receivers RSa to RSc (tag readers) that receive the signal and the second signal, and the position of the object 2 is detected using the first and second signals received by the receivers RSa to RSc. The position detection system detects the position of the object 2 from the state of the electric field strength of each of the first signal and the second signal and the timing of the change in the state of the electric field strength.
[Selection] Figure 2

Description

  The present invention relates to a technique for detecting the position of an object based on signal transmission from an IC tag.

As a conventional technique related to the present invention, there is a position detection system described in Patent Document 1. A receiver for receiving a first signal from an object to be position-detected and a plurality of second signals whose positions have been confirmed in advance, and an electric field of the first signal and the second signal received by the receiver The position of the object is detected by comparing the intensities.
JP 2002-98749 A

  However, in the prior art described in Patent Document 1, the first signal from the object whose position is to be detected and the second signal from the position whose position has been confirmed in advance are in the same state (for example, between the object and the receiver). Alternatively, unless the same obstacle is interposed between a plurality of positions whose positions have been confirmed in advance and the receiver, the electric field strength becomes unstable, and the position cannot be detected with high accuracy.

  The present invention has been made in view of the above problems, and even when an obstacle is interposed between an object and a receiver or between a plurality of positions whose positions have been confirmed in advance and the receiver, the object is accurately obtained. It is an object of the present invention to provide a position detection system capable of detecting the position of the camera.

  In order to solve the above-mentioned problem, the invention described in claim 1 is characterized in that a first transmitter that generates a first signal from an object to be position-detected and a plurality of positions from a plurality of positions that have been previously confirmed. A second transmitter for generating two signals; a plurality of receivers for receiving the first signal and the second signal; and the first signal and the second signal received by the receiver. A position detection unit that detects a position of the object using the position detection unit, wherein the position detection unit includes a state of the electric field strength of each of the first signal and the second signal, and the electric field. The position of the object is detected from the time when the intensity state changes.

  In the invention according to claim 2, the electric field intensity changes from the stable state to the unstable state, or from the unstable state to the stable state.

  Further, in the invention according to claim 3, the position of the object is detected by an obstacle between the object and the receiver, or between a plurality of positions that have been previously confirmed and the receiver, The position of the object is detected every time the electric field strength changes.

  According to a fourth aspect of the present invention, the first signal and the second signal are signals of a wireless tag having identification information, and the receiver is a tag reader for identifying the identification information.

  According to the first aspect of the present invention, in order to detect the position of the object from the state of the electric field strength of each of the first signal and the second signal and the timing of the change in the state of the electric field strength, Compared with the position detection by intensity, it is possible to detect the position of the target object with high accuracy and less affected by the obstacle.

  In the invention described in claim 2, since the position of the object is detected by using a change in the state in which the electric field intensity changes from the stable state to the unstable state or from the unstable state to the stable state, Similarly to the conventional position detection with electric field strength, it is possible to detect the position of the target object with high accuracy and less affected by the obstacle.

  In the invention according to the third aspect, since the position of the object is detected every time the state of the electric field intensity changes, position detection with higher accuracy than in the prior art becomes possible.

  In the fourth aspect of the invention, the first signal and the second signal have identification information, and the receiver identifies the identification information, so that the positions of a plurality of objects can be detected. Further, the cost can be reduced by using an inexpensive tag and tag reader.

  Embodiments of the present invention will be described below in detail with reference to FIGS. 1 to 6, but the present invention is not limited to these embodiments. Here, a case where a wireless tag (RFID) is employed as the position detecting means will be described, but the same principle can be applied even when other wireless systems such as PHS and GPS are used. Although only the position detection in the two-dimensional space is described here, it can be easily extended to the three-dimensional space. In addition, the position detection system of the present embodiment detects the position of a detection target (object) that exists in a limited space such as a room or a warehouse.

  FIG. 1 is a position detection system of the present invention, in which a person 1 moves to a shelf 3a with an object 2 and places the object 2 on the shelf 3a and leaves the space 4 to detect the position of the object 2. It is explanatory drawing of. The object 2 in the space 4 is attached with a tag RFt as a first transmitter for generating a first signal, and the five shelves 3a to 3e are used as second transmitters for generating a second signal. Reference tags RFa to RFe are respectively installed. Further, in the space 4, three receivers RSa to RSc (tag readers) are arranged.

  Radio waves (second signals) transmitted from the reference tags RFa to RFe include different identification information (CSID). A correspondence table between the respective identification information and the positions of the shelves 3a to 3e on which the reference tags RFa to RFe having the identification information are prepared separately. The radio wave (first signal) transmitted from the tag RFt has identification information different from the radio waves (second signal) transmitted from the reference tags RFa to RFe. The receivers RSa to RSc function as position detecting means for detecting the position of the object using the first signal and the second signal, and the radio wave (first signal) transmitted from the tag RFt and the reference tag RFa. The radio wave (second signal) transmitted from ~ RFe is received, each identification information is detected, and each electric field strength is measured.

  2 shows the electric field when the receivers RSa to RSc receive the radio wave (second signal) of the reference tag RFa on the shelf 3a of FIG. 1 and the radio wave (first signal) of the tag RFt attached to the object 2. It is strength. The electric field intensity of the tag RFt placed on the shelf 3a is in a stable state from 15 seconds after the object 2 is placed on the shelf 3a and left the place. The electric field strength of the reference tag RFa of the shelf 3a is in an unstable state from 10 seconds when the person 1 approaches the shelf 3a, and returns to a stable state again from 15 seconds. . This means that the radio wave is disturbed by the person 1 (obstacle) entering between the object 2 and the receiver RSb. From this, it can be determined that the object 2 is at the position of the reference tag RFa that has entered a stable state at the same time, and has been placed on the shelf 3a.

  The stable state of the electric field strength is a state where the position of the object 2 can be detected, and the unstable state of the electric field strength is a state where the position of the object cannot be detected. In this embodiment, when the change in electric field strength is within 5% of the latest value within a predetermined time, the state is stable, and when the change is larger than 5%, the state is unstable. More specifically, when the change in the electric field intensity detected by the receivers RSa to RSc is within a threshold value (0.1 V at the receiver voltage level) for 1 second, the stable state, and otherwise unstable State.

  FIG. 3 is an explanatory diagram of the position detection system of the object 2 when the person 1 of the present invention leaves the space 4 through the shelf 3a on which the object 2 is placed. 1 except that the object 2 is placed on the shelf 3a from the beginning.

  FIG. 4 shows the electric field strength when the radio waves of the tag RFt attached to the reference tag RFa and the object 2 on the shelf 3a in FIG. 3 are received by the receivers RSa to RSc. The electric field strength of the tag RFt placed on the shelf 3a and the electric field strength of the reference tag RFa on the shelf 3a both enter an unstable state from 12 seconds and enter a stable state from 15 seconds. This is because the person 1 (obstacle) has passed between the object 2 and the receiver RSb, and enters the unstable state at the same time and enters the stable state at the same time, so the object 2 is the same. It can be judged that it is in place. In addition, position detection (correction) can be performed each time the person 1 passes.

  In the present invention, since the position of the object 2 is detected from the state of the electric field strength and the timing of the change of the electric field strength state, the person 1 (obstacle) is compared with the conventional position detection with the electric field strength. It is possible to detect the position of the target object 2 with less accuracy and high accuracy. In addition, since the position of the object 2 is detected every time the state of the electric field strength changes, it is possible to detect the position with higher accuracy than in the past. Further, since the first signal of the tag RFt and the second signal of the reference tags RFa to RFe are RFID tags having identification information, the receivers RSa to RSc use a tag reader for identifying the identification information (CSID). Thus, it is possible to detect the positions of the plurality of objects 2 at a low cost.

  In the above-described embodiment, the case where there is one object 2 and three receivers RS has been described, but a plurality of detection targets may be provided, and there are two or four or more receivers RS. Also good.

It is explanatory drawing of the position detection system of the target object when the person of this invention moves to a shelf with a target object, puts a target object on a shelf, and leaves a space. This is the electric field intensity when the receiver of FIG. 1 receives the radio waves of the reference tag on the shelf and the tag attached to the object by each receiver. It is explanatory drawing of the position detection system of the target object when the person of this invention leaves in front of the shelf where the target object is placed. This is the electric field strength when the receiver of FIG. 3 receives the radio waves of the reference tag on the shelf and the tag attached to the object by each receiver.

Explanation of symbols

2 Object 3a-3e Shelf 4 Space RFt tag RFa-RFe Reference tag RSa-c Receiver

Claims (4)

A first transmitter for generating a first signal from an object to be located;
A second transmitter for generating second signals from a plurality of positions that have been previously located;
A plurality of receivers for receiving the first signal and the second signal;
Position detecting means for detecting the position of the object using the first signal and the second signal received by the receiver;
In a position detection system comprising:
The position detection means detects the position of the object from the state of the electric field strength of each of the first signal and the second signal and the time of change of the state of the electric field strength. Position detection system. The position detection system according to claim 1, wherein the state of the electric field intensity changes from a stable state to an unstable state, or from an unstable state to a stable state. The detection of the position of the object is performed by determining whether the electric field strength is in a state where an obstacle is interposed between the object and the receiver, or between a plurality of the positions that have been confirmed in advance and the receiver. 3. The position detection system according to claim 1, wherein the position of the object is detected every time it changes. 4. The first signal and the second signal are signals of a wireless tag having identification information, and the receiver is a tag reader for identifying the identification information. The position detection system according to one item.

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