JPH04149683A - Identifying method for magnetic marker - Google Patents

Abstract

PURPOSE:To prevent the erroneous identification of an article from occurring by reducing a white noise due to an external magnetic field and the function of a detection circuit itself by integrating and averaging a pulse voltage string signal. CONSTITUTION:Detection coils 7a-7c which detect magnetic flux change according to the reversal of magnetization of a magnetic marker 1 generated by an AC magnetic field as an induced electromotive voltage are connected to a measuring instrument 8 and a personal computer 9 in series. The level of the pulse voltage sequence signal is reduced depending on the relative position relation of the magnetic marker 1 and the detection coils 7a-7c, and it goes to the one equal to or less than the signal level of the white noise, which makes the pattern of the pulse voltage sequence signal difficult to identify. In such a case, the output level of the white noise is reduced by integrating and averaging the pulse voltage sequence signal, and the S/N of the signal is heightened, thereby, the recognition of a pulse voltage sequence and the identification of a pulse voltage string pattern can be performed. In such a way, it is possible to perform the identification of the article by detecting the pulse voltage sequence generated in the detection coil.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting a magnetic marker attached to an article and used for counting the type and quantity of the article.

[Conventional technology]

It is known that attaching a marker to an article, using a magnetic material as the marker, and applying an alternating magnetic field to it is used to prevent the article from being stolen. When an article to which an amorphous magnetic wire or ribbon marker is attached passes through an alternating current magnetic field, the change in magnetic flux caused by the magnetization of the marker being reversed by the alternating magnetic field can be extracted from the detection coil.

Amorphous magnetic materials have unprecedented soft magnetic properties, making it possible to obtain small and lightweight markers with high sensitivity. By arranging thin strips in combination, the magnitude of the magnetic field differs when magnetization is reversed in an alternating current magnetic field, so this can be detected as a time-series pulse voltage to identify the type of magnetic marker, that is, the article. is possible.

This method determines whether a pulse voltage is generated by the combination of each magnetic marker at a predetermined phase of an alternating magnetic field corresponding to the coercive force of each magnetic material, that is, by using a pattern sequence of 1.0, or by using a predetermined phase of an alternating magnetic field that corresponds to the coercive force of each magnetic material. The type of article is identified by the difference in the pulse voltage level that occurs in the phase of the article.

[M problems that the invention attempts to solve]

As described above, it is effective to identify items using magnetic markers based on the presence or absence of pulse voltages that occur in a predetermined phase of an alternating current magnetic field, or differences in pulse voltage levels, but these methods are Depending on the relative positional relationship between the marker and the detection coil, the detection coil may not be able to effectively detect the magnetic flux generated by the magnetic marker.
The brightness level of the pulse voltage train may become small. That is, if the output level of the white noise generated by the external magnetic field and the detection circuit itself is large enough to make it difficult to recognize and identify the pulsed voltage train signal, it becomes impossible to identify the magnetic marker, i.e., the article. It may happen.

The present invention has been made in view of the above-mentioned points, and its purpose is to correctly detect the pulse voltage generated by the magnetic marker on the detection film even under the above-mentioned conditions, and to identify articles without error. The objective is to provide a detection method that allows for

Means for solving cma] In order to solve problem S1 above, the method of the present invention integrates and averages pulse voltage train signals to reduce white noise caused by external magnetic fields and the action of the detection circuit itself.
S of the pulse voltage and white noise generated in the detection coil
This increases the N ratio.

[Effect]

Depending on the relative positional relationship between the magnetic marker and the detection coil, the pulse voltage train signal level becomes small and becomes comparable to or lower than the white noise signal level.
It becomes difficult to identify the pattern of the pulse voltage train signal, but even in such a case, the present invention integrates and averages the pulse voltage train signal n times to reduce the white noise output level to 1/J'i-. Since the SN ratio of the signal can be increased, it is possible to recognize the pulse voltage train and identify the pulse voltage train pattern.

〔Example〕

The present invention will be explained below based on examples.

First, an outline of an article identification device to which the magnetic marker detection method according to the present invention is applied will be described. FIG. 1 is a schematic diagram showing the main part configuration of an example of the device. In FIG. 1, an article 2 to which a magnetic marker 1 is affixed is on a belt 4 stretched between two pulleys 3, and the article 2 is placed on a belt 4 that travels together with the magnetic marker 1 by the rotation of each slide. Move in the direction of the arrow. Two excitation coils 5a generate an alternating magnetic field so as to sandwich the belt 4 from both sides.

5b are arranged, and these are connected to an AC oscillator 6. Detection coils 7a, 7b, and 7e, which detect changes in magnetic flux accompanying magnetization reversal of the magnetic marker 1 caused by an alternating magnetic field as induced electromotive voltages, are connected in series to a measuring device 8 and a personal computer 9. The measuring device 8 is a detection coil 7a
, 7b, 7c are subjected to signal processing, and a state in which a pattern can be recognized, for example, 1.
The personal computer 9 has the S ability to identify the M class of the magnetic marker 1.

With the above device configuration, the magnetic marker 1 as shown in FIG.
When the article 2 to be detected, that is, the object to be detected, rides on the belt 4 and passes between the excitation coils 5a and Sb, the magnetic marker 1 is magnetized by the alternating magnetic field generated there, and the magnetic flux is reversed. Among the pulse voltage trains generated in the detection coils 7a, 7b, and 7c due to the change in magnetic flux at the time, the optimum signal for detection is selected, and the pulse voltage train is compared and contrasted with a reference pulse voltage train to determine the pulse voltage. 1.
By 0 conversion and pattern recognition, magnetic marker 1
That is, it identifies 20 types of articles.

Next, the configuration of the magnetic marker used in the present invention and its identification method will be described.0Mi magnetic marker 1 For example, iron-based amorphous magnetic thin wire or ribbon having rectangular magnetic hysteresis characteristics is used. Are suitable. Although a plurality of magnetic markers 1 can be used as they are, a case will be described in which a plurality of magnetic markers 1 are arranged and configured as one detection element. Fig. IK2 f8+, (bl is a partially peeled perspective view showing the detection element. Fig. 2 1al shows four amorphous magnetic wires 1-, 1b, 1c, and It), which are oriented in the longitudinal direction. The magnetic markers U are arranged in parallel and configured as magnetic markers U, and the magnetic markers U are embedded in, for example, two thin plastic fixing plates 13.On the other hand, in FIG. all failure 1
．． ．． A magnetic marker U is constructed using three markers, lb and 1*, and serves as a detection element hill.

In other words, these detection elements are shown in Figure 2 (in Figure 2).
Compared to , the lV crystal W magnetic thin wire 1c is missing. The coercive force Hc of these magnetic wires 1-1lb, 1c, and 14 increases, and their magnetic characteristic diagram is shown in FIG. 3. As shown in FIG. 3, the magnetic wires 1-11. .

The respective coercive forces Hc corresponding to 1c and 1a are Hcm
The relationship is <Hcb < Hec < Hcl1.

Fig. 4 1j1), tb), (e) shows the detection coils 7a, 7b,
Figure 4 (al is the AC magnetic field waveform, Figure 4 (bl is the magnetic marker when a magnetic marker is used, Figure 4 (C1 is the magnetic marker waveform) is shown. Detection coils 7a, 7b, 7c when using ■
The horizontal axis represents time.

In FIG. 4) and (C), the numbers of the magnetic thin wires corresponding to the pulse voltage trains are added. Here, the alternating current magnetic field waveform of Fig. 4 (al is shown in the case of a triangular wave). It can be seen that pulse voltages are generated at predetermined phases H, , H, , Hc, H- of the magnetic field.Ho represents the maximum value of the alternating magnetic field. If the presence or absence is expressed as 1.0, it will be as shown in Table 1.

Table 1, Figure 5, 1al, (bl, (cl) and Figure 6, 1
81. (b), fcl is Fig. 4 1al, (bl,
(This is a diagram similar to C1, but detection coils 7a, 7
The coils 7a, 7b detect leakage magnetic flux generated from the magnetic marker U or U based on the relative value Wl relationship between the magnetic marker U or U and either of the coils 7a and 7c.

This shows the relationship between the pulse voltage train signal and white noise when one of the detection coils 7c cannot be picked up effectively and the output level of the pulse voltage train induced in any of the detection coils 7m, 7b, and 7e is small. be. Figure 5(a),
Figure 6 (5) shows the alternating current magnetic field waveform in exactly the same way as Figure 4 1al, and Figure 5 (crest) 7 Figure 6 ('b) shows the pulse voltage train signal 1 5 Figures (C) and 6 (C) show pulse voltage train signals when using magnetic marker ears.
In both cbl and (c), the area in which white noise is drawn by two solid lines is shown, and the threshold value for determining 0.1 for a pulse voltage train is shown in a dashed-dotted line.

Figure 5 Mountain 1. As shown in tel, if the white noise output level is higher than the threshold for judging the pulse voltage train as 0.1, the results when the pulse voltage train is judged as 0.1 are shown in Table 1. However, since the white noise is determined to be a pulse voltage and all signals are determined to be 1, it becomes impossible to read the pattern of the pulse voltage train signal. Therefore, in order to perform accurate identification, as shown in FIG. 6(b), (C1),
The white noise level must be lower than the threshold level set to judge the pulse voltage as 0.1.

Therefore, the present invention makes use of reducing the output level of the white noise generated in the detection coil to 1/fi by stacking and averaging the pulse voltage train signals n times.

That is, the measuring device 8 of the device shown in Fig. 331 is provided with a function of stacking and averaging the pulse voltage train signals, and when the white noise level is higher than the threshold value set for marker identification, the pulse voltage By integrating and averaging the column signals 0 times, the white noise level is reduced and the SN of the signal is
It increases the ratio and makes it possible to recognize pulse voltage trains and identify pulse voltage train patterns. The number of integrations n is determined optimally each time based on the magnitude relationship of the pulse voltage train signal level and the white noise level generated by external factors such as the type of article identification device, the location where the article identification device is used, and the type of identification marker. Set the number of times n.

〔Effect of the invention〕

A magnetic marker in which a plurality of amorphous magnetic thin wires or thin strips having a rectangular magnetic hysteresis curve and mutually exhibiting coercive force are selectively arranged in parallel in the longitudinal direction at desired intervals;
Alternatively, using a detection element in which this magnetic marker is fixed to a wire such as a plus wire, attach it to an article and pass an alternating magnetic field through it, and detect the magnetic marker, that is, the article, by pattern recognition of the time-series pulse voltage train generated in the detection coil. When identifying Class 11, in the present invention, as described in the embodiment,
The white noise generated by the external magnetic field and the action of the detection circuit itself is reduced by integrating and averaging the pulse voltage train signal, and the S/N ratio between the voltage generated in the detection coil and white noise by the magnetic marker is improved. This makes it possible to correctly detect the pulse voltage train generated in the detection coil and to identify the article without error.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the main part configuration of an article identification device to which the present invention is applicable, FIG. The figure shows the magnetic characteristics & I diagram of magnetic m*a, Figure 4 fa) is the AC 1 pulse waveform diagram, Figure 4 (1)) is the pulse voltage train diagram when using a magnetic marker, and Figure 4 fcl is the diagram. marker 12
Pulse voltage train diagram when using , Figure 5), Figure 6 (
at is an alternating current magnetic field waveform diagram, Fig. 5(b), Fig. 6 Q)l is a pulse voltage train signal when using a magnetic marker U, a threshold for determining white noise and a pulse voltage train as 0 or 1. Relationship diagram with value voltage, Fig. 5 (C), Fig. 6 ic)
is a relationship diagram between a pulse voltage train signal, white noise, and a threshold voltage for determining 0.1 of a pulse voltage train when a magnetic marker piece is used. 1, 11.12: Magnetic %ma:'l-2:'IPJ product,
3=Pulley 4=Belt, 5a, 5h, 14a,
14b: Excitation coil, 6: AC oscillator, ? , 15: detection coil, 8: measuring instrument, 9: personal computer,
10: detection element, 13: fixing plate.

Claims (1)

[Scope of Claims] 1) A magnetic marker or a magnetic marker in which a magnetic hysteresis curve exhibits a square shape and a plurality of amorphous magnetic thin wires or ribbons having different coercive forces are selectively arranged in parallel in the longitudinal direction at desired intervals. One of these detection elements with fixed magnetic markers is attached to an article, an alternating magnetic field is passed through it, and the time-series pulse voltage train generated in the detection coil is pattern-recognized to identify the type of magnetic marker. The phase of the pulse voltage train generated from an amorphous magnetic thin wire or ribbon in an alternating magnetic field is stored in the measuring instrument as a reference, and the pulse voltage train signal is integrated and averaged to detect white noise caused by the external magnetic field and the action of the detection circuit itself. A method for identifying a magnetic marker, comprising: reducing the phase of the magnetic marker, and identifying the type of magnetic marker by comparing and contrasting the obtained signal with the phase of a reference pulse voltage train. 2) A magnetic marker identification method according to claim 1, wherein the output level of white noise is reduced by 1/√n by integrating and averaging the pulse voltage train signal n times.