JP2024051216A - Position detection system and mobile object - Google Patents

Abstract

[Problem] To make it easier to detect the position of a moving object moving along a track, regardless of the number of moving objects. [Solution] A position detection system detects the position of a moving object moving along a track. This position detection system includes a magnet that is placed on the moving object so that the direction of the magnetic field forms a predetermined angle with the moving direction of the moving object, a plurality of sensors that are placed along the track and each detects the direction of the magnetic field of the magnet when facing the moving object, and a position detection unit that identifies the position of the moving object on the track based on the detection information of the sensors. [Selected Figure] Figure 2

Description

The present invention relates to a system for detecting the position of a moving object moving along a track.

One method for identifying vehicles traveling on a curved track without active communication means is to attach a passive RFID tag to the vehicle and read its ID information with an RFID reader placed on the track (see Patent Document 1).

International Publication No. 2016/147714

Problems with this method include the fact that metal and moisture reduce the communication distance of RFID, and when multiple conveyors approach one RFID reader, it is not possible to distinguish between the positions of the two conveyors.

One aspect of the present invention is a position detection system that detects the position of a moving object moving along a track. This position detection system includes a magnet that is placed on the moving object so that the direction of the magnetic field forms a predetermined angle with the direction of movement of the moving object, a number of sensors that are placed along the track and detect the direction of the magnetic field of the magnet when facing the moving object, and a position detection unit that identifies the position of the moving object on the track based on the detection information of the sensors.

Another aspect of the present invention is a moving body that moves on a track. The moving body has an opposing surface that can face a plurality of sensors arranged along the track, and a magnet that is provided on the opposing surface and whose magnetic field direction is detected by the sensor. The magnet is arranged on the opposing surface at an angle specific to the moving body so that the direction of the magnetic field forms a predetermined angle with respect to the moving direction of the moving body.

The present invention makes it easier to detect the position of moving objects regardless of the number of moving objects moving along a track.

FIG. 1 is a plan view illustrating a position detection system according to an embodiment. FIG. 2 is a plan view illustrating a schematic configuration of a moving body. 10 is a diagram showing an analysis result of magnetic flux density distribution on the surface of an angle detection magnet. FIG. FIG. 2 is a diagram illustrating a configuration of a magnetic sensor. FIG. 4 is a partially enlarged view that illustrates a schematic diagram of a detection head disposed on a curved track. FIG. 2 is a block diagram showing the function of a magnetic sensor.

FIG. 1 is a plan view that illustrates a position detection system according to an embodiment.
The position detection system 1 detects the position of a mobile object 4 moving along a track 2 by using magnetic sensors 6 laid along the track 2. The track 2 is configured by connecting a straight track 2a of a predetermined length and a curved track 2b (circular track) with a curvature radius r, and multiple mobile objects 4 can run on the track 2. In this embodiment, the magnetic sensors 6 include a magnetic sensor 6S arranged on the straight track 2a and a magnetic sensor 6R arranged on the curved track 2b. When there is no particular distinction between these, they will be simply referred to as "magnetic sensors 6."

The mobile body 4 is a transport machine that transports a predetermined object such as a tool, and its movement is controlled by an external device (described later). Rails (not shown) are provided on the track 2, and the mobile body 4 has wheels that are guided by the rails. Therefore, the direction of movement of the mobile body 4 is along the track 2. A magnetic medium 8 is provided on the bottom surface of the mobile body 4, i.e., the surface of the mobile body 4 that faces the track 2. Meanwhile, a plurality of magnetic sensors 6 are arranged in series at approximately equal intervals along the track 2. When any of the plurality of magnetic sensors 6 detects the presence of the magnetic medium 8, the position of the mobile body 4 can be detected.

FIG. 2 is a plan view that illustrates a schematic configuration of the moving body 4. As shown in FIG.
For ease of explanation, the horizontal directions are the X and Y directions, and the vertical direction is the Z direction. In the following explanation, the moving direction of the moving body 4 is set as the "reference direction" (see the dashed line arrow), and this is set as the X direction.

The moving body 4 has a scale 10 and an angle detection magnet 12 as a magnetic medium 8. The scale 10 includes an incremental track 14 and an absolute track 16. The incremental track 14 has an incremental pattern (magnetic pattern) that is periodically magnetically recorded at a recording wavelength λ. On the other hand, the absolute track 16 has an absolute pattern (magnetic pattern) that is magnetically recorded based on a bit string of 0s and 1s generated by an LFSR (linear feedback shift register) of a certain tap sequence.

The angle detection magnet 12 is uniformly magnetized in a certain direction in the XY plane, and is placed on the moving body 4 so that the direction of the magnetic field forms a predetermined angle θb(k) with respect to the reference direction (see dashed-dotted arrow), which is the direction of movement of the moving body 4. Here, "k" is an integer equal to or greater than 0 that indicates the ID (identification information) of the moving body 4, where k<kn and θb(k)=k×360/kn. "kn" is the total number of IDs. In other words, the angle detection magnet 12 is provided so that the magnetic field direction θb(k) differs for each of the multiple moving bodies 4 that can travel on the track 2. This sets a physically unique ID for each of the multiple moving bodies 4.

Near the surface of the angle detection magnet 12, there is an area A extending in the XYZ space where the magnitude of the magnetic flux density in the XY plane is equal to or greater than Bt, and the angle θa between the direction of the magnetic field and the reference direction (X direction) of the moving body 4 satisfies θb(k)-δθb<θa<θb(k)+δθb. For the XYZ coordinates where the magnetic sensor 6 (angle sensor 25 described below) is located, outside the range of area A, the magnitude of the magnetic flux density on the XY plane from the angle detection magnet 12 is less than Bt. In other words, the position facing area A is a position suitable for detecting the strength and direction of the magnetic field produced by the angle detection magnet 12.

Figure 3 shows the analysis results of the magnetic flux density distribution on the surface of the angle detection magnet 12. This figure shows the analysis results when the direction of the magnetic field of the angle detection magnet 12 is aligned with the X direction (i.e., θa = 0). The angle detection magnet 12 set in the analysis is a plate magnet measuring 30 x 20 x 2 mm. This figure also shows the analysis results on a plane located 10 mm in the Z direction from the surface of the angle detection magnet.

In the area surrounded by the solid lines near the center of this figure, the magnetic flux density is 17.3 mT or more. In this area, the direction of the magnetic field is within a range of ±1° with respect to the reference direction. Therefore, if Bt = 17.3 mT and δθb = 1°, the area within the solid lines can be considered as area A. Note that, as shown in FIG. 2, the line in the Y direction that passes through the center of area A in a plan view of the moving body 4 is taken as the reference line L1. In this embodiment, the reference line L1 corresponds to the center line of the moving body 4.

4A and 4B are diagrams showing the configuration of the magnetic sensor 6. Fig. 4A is a schematic diagram showing a detection head disposed on the linear track 2a, and Fig. 4B is an enlarged view showing the arrangement of angle sensors.
As shown in Fig. 4A, the magnetic sensor 6S includes a detection head 18S (straight section detection head) for detecting the magnetic medium 8 of the moving body 4. Here, the numbers of adjacent detection heads 18S on the straight track 2a are indicated by subscripts 0, 1, ..., n, ..., nmax in order (see Fig. 1). When there is no particular distinction between the multiple detection heads 18S, the subscripts are omitted.

The detection head 18S is equipped with three series of sensor units: an incremental sensor unit 20, an absolute sensor unit 22, and an angle sensor unit 24. All of the sensor units extend in the reference direction (X direction) of the detection head 18S. When the moving body 4 faces the detection head 18S, the reference directions of both coincide. The angle sensor unit 24 includes multiple angle sensors 25 arranged at equal intervals in the reference direction.

The angle sensor unit 24 is provided from one end to the other end of the reference direction of the detection head 18, but the incremental sensor unit 20 and the absolute sensor unit 22 are provided toward the center of the detection head 18S. In the reference direction, the angle sensor unit 24 is larger than the incremental sensor unit 20 and the absolute sensor unit 22, but the individual angle sensors 25 that make up the angle sensor unit 24 are smaller than the incremental sensor unit 20 and the absolute sensor unit 22, and a large number of them are arranged in the detection head 18. Since it is necessary to arrange the angle sensors 25 so that at least one is present in the area A no matter where the moving body 4 is located, when the angle detection magnet 12 is the size shown in FIG. 2, a configuration in which many small angle sensors 25 are arranged as shown in FIG. 4 is obtained.

When a reference line L2 is set at the center position of the detection head 18 in the reference direction, each sensor unit is arranged approximately symmetrically with respect to the reference line L2.

When the moving body 4 faces the detection head 18S, the incremental sensor unit 20 faces the incremental track 14, the absolute sensor unit 22 faces the absolute track 16, and the angle sensor unit 24 faces the angle detection magnet 12. Then, each sensor unit reads the magnetic signal generated from the corresponding magnetic medium 8. That is, the incremental sensor unit 20 detects the incremental pattern, the absolute sensor unit 22 detects the absolute pattern, and one of the angle sensors 25 detects the strength and direction of the magnetic field of the angle detection magnet 12.

The magnetic sensor 6S can detect the relative position between the moving body 4 and the detection head 18S by combining the outputs of the incremental sensor unit 20 and the absolute sensor unit 22. When the moving body 4 travels between adjacent detection heads 18S, each sensor unit of the adjacent detection heads 18S detects the magnetic field generated from each track of the moving body 4, and can detect the relative position between the moving body 4 and the detection head 18S.

The angle sensor 25 can also detect the direction of the magnetic field on the XY plane generated by the angle detection magnet 12 and the magnitude of the magnetic flux density. As shown in FIG. 4B, the center of the magnetically sensitive portion of the angle sensor 25 is the reference point Po, and the direction of the magnetic field on the XY plane where the angle sensor 25 indicates 0° is the reference direction (X direction). The reference direction of the angle sensor 25 is parallel to the reference direction of the moving body 4. Regardless of the direction of the magnetic field on the XY plane, whether inside or outside the detection head 18S, or the type, when the angle detection magnet 12 of the moving body 4 passes through the area between adjacent angle sensors 25, both of the adjacent angle sensors 25 are configured to enter area A (see FIG. 2) of the angle detection magnet 12.

FIG. 5 is a partially enlarged view that diagrammatically illustrates the detection head disposed on the curved track 2b.
The magnetic sensor 6R includes a detection head 18R (curved portion detection head) that is aligned with the curved track 2b. Here, the numbers of adjacent detection heads 18R on the curved track 2b are sequentially indicated by subscripts 0, 1, ..., n, ..., nmax (see FIG. 1). Furthermore, regardless of the type of detection head 18R, the numbers of adjacent angle sensors 25 on the curved track 2b are sequentially indicated by subscripts 0, 1, ..., m, ..., mmax (see FIG. 1). Note that when there is no particular distinction between the multiple angle sensors 25, the subscripts are omitted.

The detection head 18R has an angle sensor 25 like the one in the linear track 2a, but does not have an incremental sensor unit 20 or an absolute sensor unit 22. The angle sensor 25 detects the direction and strength (magnitude of magnetic flux density) of the magnetic field on the XY plane generated by the angle detection magnet 12 of the moving body 4.

When the moving body 4 travels on the curved track 2b, the reference point Po (see FIG. 4B) of the angle sensor 25 is positioned so that the angle detection magnet 12 passes above it. When the moving body 4 is in a position where the reference line L1 of the moving body 4 and the reference point Po of the angle sensor 25 overlap, the reference direction of the moving body 4 and the reference direction of the angle sensor 25 are configured to be parallel. In this embodiment, these reference directions are tangent directions (parallel to the tangent) of the curved track 2b.

As shown in Fig. 1, the angle sensor _25R0 is located at the connection between the straight track 2a and the curved track 2b. Meanwhile, as shown in Fig. 5, the interval between adjacent angle sensors 25 is the difference in arc length from the center of the curved track 2b, which is lc. Regardless of whether inside or outside the detection head 18R or the type, when the angle-detecting magnet 12 travels through the area between adjacent angle sensors 25, both of the adjacent angle sensors 25 are configured to enter area A (see Fig. 2) of the angle-detecting magnet 12.

FIG. 6 is a block diagram showing the function of the magnetic sensor 6.
Each component of the magnetic sensor 6 is realized by an electronic circuit such as a processor, a storage device such as a memory or storage, and a wired or wireless communication line connecting them. Some functions of the magnetic sensor 6 may be realized as software stored in a storage device and executed by a computing unit. Each block described below represents a functional block, not a hardware configuration.

The magnetic sensor 6 includes an external interface unit 100 that processes signals detected by the detection head 18. The external interface unit 100 transmits and receives data to and from an external device 120 via wired or wireless communication. A plurality of magnetic sensors 6 are arranged on the track 2, and each magnetic sensor 6 has unique identification information (hereinafter also referred to as "sensor ID"). The external device 120 can identify the magnetic sensor 6 that sent the sensor information and its position (position on the track 2) based on the sensor ID.

The external interface unit 100 includes a position detection unit 110 and an ID determination unit 112. The position detection unit 110 identifies the presence of the moving object 4 based on the magnitude of the magnetic flux density (magnetic field strength) detected by the angle sensor 25, and identifies the detailed position of the moving object 4 based on the detection values of the incremental sensor unit 20 and the absolute sensor unit 22.

As described above, on the straight track 2a, the position detection unit 110 locates the presence of the moving body 4 based on the magnitude of the magnetic flux density detected by the angle sensor 25, and locates the exact position of the moving body 4 based on the detection values of the incremental sensor unit 20 and the absolute sensor unit 22. That is, when the magnetic flux density detected by the angle sensor 25 is equal to or greater than a predetermined value, it is determined that the moving body 4 is present on the detection head 18. Then, the exact position of the moving body 4 is identified by a combination of the detected incremental pattern and absolute pattern. Furthermore, on the curved track 2b, the position detection unit 110 locates the approximate position of the moving body 4 based on the magnitude of the magnetic flux density detected by the angle sensor 25.

When the position detection unit 110 has identified the presence of a moving body 4 in this manner, the ID determination unit 112 determines the ID of the moving body 4 (hereinafter also referred to as "moving body ID") based on the detection value of the angle detection magnet 12. That is, the moving body ID is identified based on the direction of the magnetic field generated by the angle detection magnet 12, that is, it is identified as one of multiple moving bodies 4. The external interface unit 100 outputs the moving body ID and position information of the identified moving body 4 to the external device 120. The position information includes the sensor ID of the magnetic sensor 6 that is the source of the moving body ID. This allows the external device 120 to determine which moving body 4 is located at which position on the track 2.

The method for detecting the position of the moving object 4 will now be described in more detail.
With the above configuration, it is possible to obtain the ID and coordinates on the track 2 (also called "track coordinates") of the moving object 4 traveling on the track 2 including a curved portion. First, the position detection unit 110 obtains the track coordinates of the moving object 4. For the straight track 2a, the track coordinates are obtained using the incremental sensor unit 20 and the absolute sensor unit 22. For the curved track 2b, the track coordinates are obtained by determining the angle sensor 25 where the angle detection magnet 12 of the moving object 4 is located.

When the moving body 4 travels on the track 2, one or two of the angle sensors 25 are located in area A of the angle detection magnet 12. This can be determined by whether the magnitude of the magnetic flux density on the XY plane detected by the angle sensor 25 is equal to or greater than Bt. To make this determination, a predetermined determination table is set. In this determination table, when the magnitude of the magnetic flux density detected by the angle sensor 25 is equal to or greater than Bt, the combination of angle sensors 25 that detect this corresponds to the on-track coordinates for each combination.

When the moving body 4 is on the linear trajectory 2a, the relative position p between the scale 10 and the detection head 18 obtained from the incremental sensor unit 20 and the absolute sensor unit 22 is used to identify the trajectory coordinates where the moving body 4 is located. Therefore, the resolution of the relative position p is the resolution of the trajectory coordinates P. Here, the relative position p is set to 0 when the reference line L1 of the moving body 4 and the reference line L2 of the detection head 18 coincide with each other.

When the moving body 4 is on a curved track 2b, the track coordinates are obtained based on the presence or absence of an angle detection magnet 12 on the angle sensor 25. Therefore, each time the angle sensor 25 in area A changes, the track coordinates change with a resolution of lc. The position detection unit 110 outputs the track coordinates of the moving body 4 by referring to the judgment table, and can output position data that follows the actual track coordinates while maintaining continuity.

Next, the ID determination unit 112 determines the ID (mobile body ID) of the mobile body 4. The mobile body ID is determined using the direction of the magnetic field on the XY plane detected by the angle sensor 25. Here, we consider the direction of the magnetic field detected by the angle sensor 25 when the reference point Po, which is the magnetically sensitive portion of the angle sensor 25, is within the area A of the mobile body 4.

The ID determination unit 112 can determine that the ID of the moving body 4 is k if the angle θ between the direction of the magnetic field and the reference direction of the angle sensor 25 satisfies θb(k)-360/2/kn<θ<θb(k)+360/2/kn. Here, the angle between the reference direction of the moving body 4 and the reference direction of the angle sensor 25 is θh. In the case of the detection head 18S installed on the linear track 2a, θh=0° is always the case.

When the moving body 4 passes the angle sensor 25 of the detection head 18 provided on the curved track 2b, the length of the track that the angle sensor 25 traces in area A is assumed to be 2×la. In this case, when a certain angle sensor 25 is within area A, θh satisfies -la/r×180/π<θh<la/r×180/π. Therefore, no matter what track the moving body 4 is located on, θh satisfies -la/r×180/π<θh<la/r×180/π.

On the other hand, as described above, with regard to the angle θa between the direction of the magnetic field and the reference direction (X direction) for the moving body 4, within region A, θb(k) - δθb < θa < θb(k) + δθb. Since θ = θa + θh, θ satisfies θb(k) - δθb - la/r x 180/π < θ < θb(k) + δθb + la/r x 180/π.

From the above, when δθb + la/r × 180/π < 360/2/kn, the moving object ID can be identified as k in the entire region. For example, if la = 4 mm, the radius of curvature r = 360/π, and kn = 45, then δθb + la/r × 180/π = 3°, 360/2/kn = 4°, which satisfies the above inequality, and therefore the moving object ID can be identified as k.

The position detection system 1 has been described above based on the embodiment.
According to this embodiment, a plurality of magnetic sensors 6 are arranged along the track 2, while an angle-detecting magnet 12 is disposed on the moving body 4 so that the direction of the magnetic field forms a predetermined angle with respect to the moving direction of the moving body 4. Since the predetermined angle is set to be unique to the moving body 4, the presence and type of the moving body can be identified based on the detection information of the angle-detecting magnet 12, such as the magnitude of the magnetic flux density and the direction of the magnetic field detected by the magnetic sensor 6. Since the detection range of the magnetic sensor 6 is localized, the position of each moving body 4 can be easily detected regardless of the number of moving bodies 4.

In addition, in this embodiment, the magnetic medium 8 is provided on the movable side, i.e., the moving body 4 side, and the magnetic sensor 6 is provided on the fixed side, i.e., the track 2 side. In other words, the moving body 4 side only has a magnet. This has the advantage of making it easier to supply power to the magnetic sensor 6. The scale 10, which requires highly accurate installation, does not need to be installed over the entire length of the track 2, but only needs to be installed on the moving body 4 side, which reduces installation costs and improves maintainability.

The present invention is not limited to the above-described embodiment and modifications, and can be embodied by modifying the components without departing from the spirit of the invention. Various inventions may be formed by appropriately combining multiple components disclosed in the above-described embodiment and modifications. In addition, some components may be deleted from all the components shown in the above-described embodiment and modifications.

[Modification]
In the above embodiment, the scale 10 and the angle detection magnet 12 are provided as the magnetic medium 8 of the movable body 4, and the scale 10 includes the incremental track 14 and the absolute track 16. The detection head 18S installed on the straight track 2a is provided with the incremental sensor unit 20, the absolute sensor unit 22, and the angle sensor unit 24, while the detection head 18R installed on the curved track 2b is provided with only the angle sensor unit 24.

This requires high accuracy in detecting the position of the moving object 4 on the straight track 2a, but relaxes the requirement for the curved track 2b. This setting is possible depending on the application and specifications of the position detection system 1. If the curved track 2b does not require the same level of accuracy as the straight track 2a, costs can be reduced by simplifying the configuration of the magnetic sensor.

In a modified example, the detection head 18S may have only the absolute sensor unit 22, without the incremental sensor unit 20. The scale 10 of the magnetic sensor 6 may include only the absolute track 16, and not the incremental track 14. As long as at least an absolute pattern is formed, the base position of the moving body 4 can be identified.

Alternatively, regardless of whether the track is a straight line 2a or a curved line 2b, the incremental sensor unit 20 and absolute sensor unit 22 may be eliminated and only the angle sensor unit 24 may be provided. As the magnetic medium 8 of the magnetic sensor 6, the incremental track 14 and absolute track 16 may be eliminated and only the angle detection magnet 12 may be provided. Since identifying the presence of the moving body 4 based on the magnitude of the magnetic field of the angle detection magnet 12 leads to identifying the approximate position of the moving body 4, when the position detection accuracy of the moving body 4 is not required, the angle detection magnet 12 is sufficient for detecting the position and identifying the type of the moving body 4.

Conversely, if highly accurate position detection is required even on the curved track 2b, the detection head 18R may also be provided with an incremental sensor unit 20, an absolute sensor unit 22, and an angle sensor unit 24. In particular, when the radius of curvature r of the curved track 2b is large, there is an advantage to adopting a configuration similar to that of the straight track 2a.

In the above embodiment, the orbit 2 is configured with a straight orbit 2a and a curved orbit 2b (circular orbit). In a modified example, the orbit may be configured with only straight orbits, only curved orbits, a curved orbit other than a circular orbit, or a combination of these.

In the above embodiment, a configuration including a magnetic sensor (incremental sensor unit 20, absolute sensor unit 22, etc.) as a sensor for detecting the detailed position of the moving body 4 was exemplified. In a modified example, this may be replaced with an optical sensor. In this case, detection is still performed using the angle detection magnet 12 and angle sensor 25.

In the above embodiment, the direction of the detection head 18R on the curved trajectory 2b is the tangent direction of the curved trajectory 2b (see FIG. 5), but the arrangement of the detection head 18R and the angle sensor 25 is not limited to this. For example, the detection head 18R does not need to be arranged in the tangential direction, and the angle sensor 25 may be arranged on the detection head 18R so that its reference direction is the tangential direction. Alternatively, the angle sensor 25 may not be arranged in the tangential direction, but the direction of the magnetic field generated by the angle detection magnet 12 may be calculated taking into account an offset from the tangential direction.

1 Position detection system, 2 Track, 2a Straight track, 2b Curved track, 4 Moving body, 6 Magnetic sensor, 8 Magnetic medium, 10 Scale, 12 Angle detection magnet, 14 Incremental track, 16 Absolute track, 18 Detection head, 20 Incremental sensor unit, 22 Absolute sensor unit, 24 Angle sensor unit, 25 Angle sensor, 100 External interface unit, 110 Position detection unit, 112 ID determination unit, 120 External device, L1 Reference line, L2 Reference line, Po Reference point.

Claims (4)

A position detection system for detecting a position of a moving object moving along a track, comprising:
a magnet disposed on the moving body such that a direction of a magnetic field forms a predetermined angle with respect to a moving direction of the moving body;
a plurality of sensors arranged along the track, each of which detects a direction of the magnetic field of the magnet when facing the moving body;
a position detection unit that identifies a position of the moving object on the track based on detection information of the sensor;
A position detection system comprising: The moving body includes a plurality of moving bodies in which the directions of the magnetic fields of the magnets are different from each other,
the sensor detects the strength and direction of the magnetic field of the magnet when the moving body faces the magnet,
2. The position detection system according to claim 1, wherein the position detection unit identifies the presence of any of the plurality of moving bodies based on a magnetic field strength detected by any of the plurality of sensors, and identifies which of the plurality of moving bodies the moving body is based on a direction of the detected magnetic field. a scale having a magnetization pattern is further provided on a surface of the movable body facing the track;
a magnetic sensor capable of reading the magnetization pattern is provided at a position on the track that can face the scale,
The position detection system according to claim 1 , wherein the position detection unit identifies a detailed position of the moving object based on the detection information of the magnetic sensor. A moving body that moves on a track,
an opposing surface that is capable of opposing a plurality of sensors arranged along the track;
a magnet provided on the opposing surface, the direction of the magnetic field of which is detected by the sensor;
Equipped with
The magnet is disposed on the opposing surface at an angle specific to the movable body so that a direction of a magnetic field forms a predetermined angle with respect to a direction of movement of the movable body.

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