JP7545141B2 - Pallet Management System - Google Patents

Description

The present invention relates to a technology for managing the status of pallets using wireless tags attached to the pallets.

Generally, pallets used for transporting and storing cargo are stored in a warehouse either with cargo on it or without cargo on it. To efficiently use the pallets in the warehouse, it is necessary to manage the status of the pallets stored in the warehouse. In particular, it is important to know the number of empty pallets that do not have cargo on them that can be used immediately.

Empty pallets that do not have any cargo on them are stored in a stacked state on the warehouse floor in order to make effective use of the space inside the warehouse. Patent Document 1 proposes a technique for managing such stacked pallets, in which the stacked pallets are photographed with a forklift camera, and the stacking state of the pallets is determined based on the vertical lengths of the start bar and stop bar attached to the front of the pallet that are included in the photographed image.

JP 2015-084139 A

However, understanding the condition of pallets using images requires additional equipment such as cameras to take images of the stacked pallets, as well as image processing software to extract the vertical length from the images.

In addition, if there are pallets in the warehouse that do not have start or stop bars on the front, it may not be possible to accurately grasp the condition of the pallets, and it may be necessary to change the configuration of existing pallets in use.

As such, conventional technology had the problem of needing to add equipment to manage the state of the pallets or change the configuration of the pallets.

The present invention was made to solve the above problems, and aims to provide a pallet management technology that can manage the status of pallets without adding equipment or changing the configuration of the pallets.

In order to solve the above-mentioned problems, a pallet management system according to the present invention is a pallet management system comprising a radio tag installed on a pallet, a radio tag reader that receives a beacon signal transmitted by the radio tag, and a pallet management device, wherein the radio tag comprises radio transmission means that transmits a beacon signal including identification information unique to the radio tag, and beacon detection means that detects beacon signals transmitted by other stacked radio tags, and a first radio tag is configured to transmit, by the beacon detection means, the beacon signal including detection information of the detection of a beacon signal transmitted by a second radio tag to the radio tag reader, and the radio tag reader associates identification information of the first radio tag with the detection information and transmits them to the pallet management device, and the pallet management device manages a status of the pallet on which the first radio tag is installed based on the identification information of the first radio tag and the detection information, and when the detection information associated with the identification information of the first radio tag indicates that a beacon signal transmitted by the second radio tag has been detected, it is determined whether the pallet on which the first radio tag is installed is an empty pallet on which no cargo is placed .

The beacon detection means may also be a passive wireless element that does not require power supplied from a power source.

The pallet may be constructed by combining metal structural members, and the wireless tag may be surrounded by the metal structural members and disposed in a space above and below the pallet that is free of the metal structural members, and further, the wireless tag may be disposed in the center of the pallet in a plan view.

The pallet may also have four support columns at predetermined positions on the edge of the pallet when viewed in a plan view, and at least two of the support columns may have alignment means for aligning the upper pallet with the lower pallet when the pallets are stacked.

The pallet may also be configured such that the at least two support members have alignment means consisting of protrusions or holes at their upper and lower parts, and when the pallets are stacked, the upper pallet and the lower pallet are aligned by the protrusions and the holes engaging with each other.

The present invention makes it possible to provide a pallet management technology that can manage the status of pallets without adding equipment or changing the configuration of the pallets.

FIG. 1 shows an example of the configuration of a pallet management system according to the first embodiment. FIG. 2 is an example of a functional block diagram of a wireless tag and a wireless tag reader according to the first embodiment. FIG. 3 shows an example of an operation mode of the wireless tag in the first embodiment. FIG. 4 shows an example of detection of a beacon signal from a wireless tag in the first embodiment. FIG. 5 shows an example of pallet state management data in the first embodiment. FIG. 6 is an example of a sequence for explaining the palette management method according to the first embodiment. FIG. 7 is an example of a control flowchart of the palette management method according to the first embodiment. FIG. 8A is a configuration example (top view) of a pallet according to the second embodiment. FIG. 8B is a configuration example (side view A) of a pallet in the second embodiment. FIG. 8C is a configuration example (side view of B) of a pallet in the second embodiment. FIG. 9A is a configuration example (side view A) of a pallet in the second embodiment. FIG. 9B is a configuration example (side view A) of stacked pallets in the second embodiment. FIG. 9C is a configuration example (side view B) of stacked pallets in the second embodiment. FIG. 10 shows an example of the configuration of stacked pallets in the second embodiment. FIG. 11 shows the verification results of beacon signal detection in the second embodiment.

The following describes an embodiment of the present invention with reference to the drawings. The present invention is not limited to the embodiment described below.

First Embodiment
<System Configuration>
1 shows an example of the configuration of a pallet management system in a first embodiment. The pallet management system is made up of a wireless tag 10 attached to a pallet 2 that is transported by a forklift 5 and stored in a warehouse 1 and used for transporting and storing cargo, a wireless tag reader 30 that receives a beacon signal containing unique identification information transmitted by the wireless tag, and a pallet management device 40 that is connected to the wireless tag reader 30 via a network 50 and manages the status of the pallet 2 in the warehouse 1. The wireless tag reader 30 may be configured to include the pallet management device 40.

The pallet 2 in the first embodiment is a resin pallet, and a wireless tag is housed in the space at the center of the pallet 2. For example, the wireless tag 10 may be housed in the center of a container box molded from resin and placed in the space at the center of the pallet 2. The present invention is not limited to resin, and can also be applied to pallets made of other materials, such as metal pallets.

The wireless tag 10 installed on the pallet 2 has the ability to detect beacon signals transmitted by other wireless tags 10, and when pallets 2 on which wireless tags 10 are installed are stacked, the wireless tag 10 can detect the presence of beacon signals transmitted by the wireless tags 10 on the upper and lower pallets, detect the presence of a pallet above or below, and know that the pallets are stacked.

Here, since the beacon signals transmitted by other stacked wireless tags are detected, it is desirable that the vertical positions of the wireless tags are aligned when stacked, but installation errors in the front-to-back or left-to-right directions between pallets when stacking are acceptable within a certain range. For example, if the pallet is made of resin and is about 150 mm thick, the distance between the wireless tags is close, so installation errors within the range of the wavelength of the radio waves used by the wireless tag 10 are acceptable. For example, if the frequency of the radio waves used by the wireless tag 10 is 920 MHz (wavelength: 325 mm), it is possible to detect beacon signals transmitted by other wireless tags even if there is an installation error of about 300 mm.

In addition, the location of the wireless tag on each pallet is preferably in the center of the pallet when viewed in a plan view, but is not limited to the center of each pallet as long as it can receive other beacon signals when stacked.

This wireless tag detects beacon signals from other wireless tags using a passive wireless element. A passive wireless element is an element that operates using radio waves transmitted by an external device such as a wireless tag, and does not require power supplied from a battery or other power source to operate. This passive element is installed in an active wireless tag in order to activate the wireless tag from the outside.

The receiving gain of a passive wireless element is small, so it cannot detect beacon signals transmitted by other wireless tags installed far away. However, when a wireless tag is stacked with other wireless tags and the tags are in close proximity to each other, the passive wireless element built into the wireless tag operates using the radio waves of the beacon signals transmitted by the other wireless tags, and can detect the presence of the other stacked wireless tags.

Each wireless tag cannot determine whether other wireless tags are present both above and below, but by detecting the beacon signals of other pallets, it can determine whether a wireless tag is present at least on either the top or bottom side.

The wireless tag 10 can notify the wireless tag reader 30 that the pallet on which the wireless tag is installed is in a stacked state, i.e., empty state, by including detection information indicating that the beacon signal of another wireless tag has been detected in the beacon signal that it transmits to the wireless tag reader 30.

The wireless tag reader 30 has the function of collecting information on multiple wireless tags by receiving beacon signals transmitted by the wireless tags and reading the identification information (tag ID). The wireless tag reader 30 transmits the identification information of the wireless tags it is receiving and detection information indicating that it has detected a beacon signal from another wireless tag to the pallet management device 40 via the network 50.

The pallet management device 40 can manage the status of pallets in the warehouse 1 based on the received identification information of the wireless tag and detection information indicating that a beacon signal from another wireless tag has been detected. If the beacon signal contains detection information of a beacon signal from another wireless tag, it can determine that the pallet is stacked and is an empty pallet with no cargo placed on it.

In this way, according to this embodiment, in a pallet management system equipped with a wireless tag equipped with a passive element and a wireless tag reader, it is possible to provide a pallet management technology that can manage the availability of pallets without adding equipment or changing the configuration of the pallets.

<Configuration of wireless tag and wireless tag reader>
2 is an example of a functional block diagram of a wireless tag and a wireless tag reader in the first embodiment. Wireless tags #A and #B are wireless tags 10 on stacked pallets, and wireless tag #C is a wireless tag 10 installed on a pallet that is not stacked.

<Wireless tag>
Wireless tags #A, #B, and #C are active tags that are powered by an internal battery 15 and include an antenna 11 and a wireless unit 12 for transmitting a beacon signal including identification information, a vibration sensor 13 for detecting vibrations of the wireless tag, a passive wireless element 14 for detecting beacon signals transmitted by other wireless tags, a central processing unit 16 for controlling each part, and a memory 17.

The passive wireless element 14 is an element that does not require power supplied from a battery 15 for its operation, and is used as a beacon detection means for detecting beacon signals transmitted by other stacked wireless tags.

The central processing unit 16 controls the operating mode of the wireless tag 10 according to the state of the vibration sensor 13, controls the transmission interval of the beacon signal, and notifies the wireless tag reader 30 of the state of the wireless tag 10 using the beacon signal. In addition, when the passive wireless element 14 detects another beacon signal, the central processing unit 16 controls the information transmitted in the beacon signal so that it includes detection information of the beacon signal of the other wireless tag.

For example, a flag may be provided in the payload portion of the beacon signal to notify the detection information of the beacon signal of another wireless tag, and the wireless tag reader 30 may be notified of whether or not the beacon signal of another wireless tag has been detected by turning this flag ON/OFF.

<Wireless tag reader>
The wireless tag reader 30 is a device that receives a beacon signal transmitted by the wireless tag 10 and manages the status of the wireless tag 10. The wireless tag reader 30 includes an antenna 31 and a wireless unit 32 for receiving a beacon signal from the wireless tag 10, an I/F unit 33 for transmitting and receiving signals via the pallet management device 40 and a network 50, a central processing unit 34 for controlling the transmission and reception of the beacon signal and the like, and a memory 35.

In an embodiment of the present invention, the transmission frequency and transmission interval of the beacon signal in the wireless tag 10 are set for each predetermined operation mode, and the operation mode is changed based on information from each sensor etc. provided in the wireless tag 10, and the beacon signal is transmitted at the transmission frequency and transmission interval set for each operation mode. By setting the transmission interval of the beacon signal for each operation mode, the wireless tag 10 aims to achieve both low power consumption of the wireless tag and maintaining the reliability of management.

<Operation mode of wireless tag>
Fig. 3 shows an example of the operation modes of the wireless tag in the embodiment of the present invention. In Fig. 3, the wireless tag has a mode in which the pallet 2 is stationary in a warehouse or the like ("association mode"), a mode in which the pallet 2 is moving up and down ("vibration mode"), and a mode in which the pallet 2 is moving and moving up and down for a long period of time ("movement mode"), and the transmission frequency and transmission interval of the beacon signal are set for each mode.

For example, in the association mode, since the robot is stationary within warehouse 1, a beacon signal is transmitted at a predetermined interval (T1). The transmission period of the beacon in the association mode is set to be longer than that in the vibration mode in order to reduce power consumption.

Furthermore, if vertical movement of the pallet is detected, there is a high possibility that the pallet 2 will be moved to another location by a forklift 5 or the like, so the system transitions to a vibration mode that transmits beacon signals at shorter intervals (T2), improving the reliability of managing the pallet's position. Furthermore, if the vibration of the pallet continues for a long period of time, the system transitions to a movement mode with a longer transmission interval than the vibration mode (T3).

In this way, in this embodiment, the transmission interval of the beacon signal is changed depending on the state of the wireless tag 10, improving the reliability of pallet management while reducing power consumption. The transmission frequency (F1-F3) of the beacon signal in each mode is also predetermined, and each wireless tag 10 is configured to transmit the beacon signal at the transmission frequency and transmission interval set for each operating mode.

<Detection of beacon signals from wireless tags>
Next, detection of a beacon signal in the wireless tag in the embodiment of the present invention will be described below. Fig. 4 shows an example of detection of a beacon signal in the wireless tag in the first embodiment.

Radio tags #A, #B, and #C are radio tags 10 installed on pallets 2. As described in FIG. 3, the radio tags transmit beacon signals including identification information at transmission frequencies and transmission intervals determined for each operating mode. In FIG. 4, radio tags #A and #B are radio tags 10 on stacked pallets 2, and radio tag #C is a radio tag 10 installed on a pallet 2 that is not stacked.

Note that Figure 4 illustrates an example in which wireless tags #A, #B, and #C are stationary and operating in association mode, but the same applies when they operate in other modes.

For example, even when stacked pallets 2 are being moved together, each wireless tag can detect beacon signals from wireless tags installed on other stacked pallets. In this case, by managing the state of the pallets together with information from the vibration sensor, multiple stacked pallets can be managed together as a group of pallets.

The wireless tag reader 30 receives beacon signals transmitted by wireless tags #A, #B, and #C, and can use the beacon signals to collect information on the status of the wireless tags and manage the status of the wireless tags.

In this embodiment, a flag is provided in the payload portion of the beacon signal to notify the detection information of the beacon signal of another wireless tag, and by turning this flag ON/OFF, the wireless tag reader 30 is notified of whether or not the beacon signal of another wireless tag has been detected. For example, a beacon signal transmitted from wireless tag #A that has been detected by another wireless tag is described as a beacon signal (A/ON), and a beacon signal that has not been detected is described as a beacon signal (A/OFF).

Wireless tag #A transmits a beacon signal (A/OFF), and similarly, wireless tags #B and #C transmit beacon signals (B/OFF, C/OFF). At this point, wireless tag #A has not detected the beacon signals of the other wireless tags, so in the beacon signal it transmits, the detection information for the beacon signals transmitted by the other wireless tags is "OFF".

When a pallet with wireless tag #B installed is stacked on top of a pallet with wireless tag #A installed, the passive wireless element enables wireless tag #A to detect that another wireless tag has been stacked above or below wireless tag #A.

Although wireless tag #A cannot identify that the other stacked wireless tag is wireless tag #B, it can detect at least that other wireless tags are stacked by detecting the beacon signal. On the other hand, the pallet on which wireless tag #C is installed is not stacked, so wireless tag #A cannot detect the beacon signal of wireless tag #C.

When wireless tag #A detects the presence of a beacon signal transmitted by another wireless tag, it transmits a beacon signal (A/ON) including the identification information of the wireless tag and detection information of the beacon signal transmitted by the other wireless tag to the wireless tag reader 30. Here, after transmitting the beacon signal (A/ON) including the detection information, wireless tag #A resets the detection information of the other beacon to the "OFF" state.

When the wireless tag reader 30 receives a beacon signal (A/ON) from wireless tag #A that includes detection information of a beacon signal transmitted by another wireless tag, it transmits the detection information to the pallet management device.

When a pallet with wireless tag #B installed is stacked on top of a pallet with wireless tag #A installed, the passive wireless element enables wireless tag #B to detect that another wireless tag has been stacked above or below wireless tag #B.

When wireless tag #B detects the presence of a beacon signal transmitted by another wireless tag, it transmits a beacon signal (B/ON) including the identification information of the wireless tag and detection information of the beacon signal transmitted by the other wireless tag to the wireless tag reader 30. Here, after transmitting the beacon signal (B/ON) including the detection information, wireless tag #B resets the detection information of the other beacon to the "OFF" state.

When the wireless tag reader 30 receives a beacon signal (A/ON) from wireless tag #A that includes detection information of a beacon signal transmitted by another wireless tag, it transmits the detection information to the pallet management device. When wireless tags #A and #B are no longer stacked, a beacon signal that sets the detection information to "OFF" is transmitted. The wireless tag reader 30 may be configured to set the detection information of the wireless tag to "OFF" when it receives beacon signals that set the detection information to "OFF" multiple times.

The pallet on which wireless tag #C is installed is not stacked, so wireless tag #C will continue to transmit a beacon signal (C/OFF) at a specified interval.

The wireless tag reader 30 transmits the identification information of the wireless tag and the detection information of the beacons of other wireless tags to the pallet management device 40. The pallet management device 40 manages the identification information and the detection information of the beacons of other wireless tags in association with each other, thereby being able to grasp the status of the pallet carrying the wireless tag. If the detection information of the beacon signals of other wireless tags is included, it can be determined that the pallet is stacked and is an empty pallet with no cargo placed on it.

<Pallet status management data>
5 shows an example of pallet status management data in an embodiment of the present invention. This status management data is recorded in pallet management device 40. Pallet management device 40 manages the status of a pallet based on the identification information of the wireless tag and detection information of beacon signals from other wireless tags.

The status management data for a pallet consists of the pallet ID of the pallet, the radio tag ID of the radio tag installed on the pallet, beacon detection information, and pallet information. The pallet ID and radio tag ID are associated in advance, and the stacking status of each pallet can be determined using detection information of the beacon signals of other radio tags of the radio tag, thereby ascertaining the vacancy status of the pallet. The example in Figure 5 shows the status of the pallets in the example in Figure 4, and the pallets with radio tags #A and #B installed have been determined to be vacant with no cargo placed on them.

<Sequence>
6 is an example of a sequence for explaining the pallet management method in the first embodiment of the present invention. In the following explanation, the case where the beacon signal includes a detection signal of a beacon signal of another wireless tag is described as "ON", and the case where the detection signal of a beacon signal of another wireless tag is not included is described as "OFF".

The pallet management device preregisters the identification information of the pallets to be managed and the wireless tags attached to those pallets. Figure 6 shows an example of a case where a pallet with a wireless tag attached is stored in a warehouse and operates in association mode where the wireless tag is stationary.

When a pallet on which wireless tag #A is installed is moving, wireless tag #A operates in moving mode and transmits a beacon signal including identification information (A) at the transmission interval in moving mode. When a pallet on which wireless tag #A is installed is stored in a warehouse, the operating mode of wireless tag #A changes (from moving to association), and wireless tag #A transmits a beacon signal including identification information (A) at a specified transmission interval determined in association mode.

The wireless tag reader receives the beacon signal transmitted by wireless tag #A. At this point, wireless tag #A has not detected the beacon signals of other pallets, so in the beacon signal transmitted by wireless tag #A, the detection information for the beacon signals of other wireless tags is "OFF".

The wireless tag reader transmits the received identification information and detection information (A/OFF) of wireless tag #A to the pallet management device. The pallet management device can confirm that the pallet with wireless tag #A attached has been stored in the warehouse.

When a pallet on which wireless tag #B is installed is moving, wireless tag #B operates in moving mode and transmits a beacon signal including identification information (A) at the transmission interval in moving mode. When a pallet on which wireless tag #B is installed is stored in a warehouse, the operating mode of wireless tag #B changes (from moving to association), and wireless tag #B transmits a beacon signal including identification information (B) at a specified transmission interval determined in association mode.

The wireless tag reader receives the beacon signal transmitted by wireless tag #B. At this point, wireless tag #B has not detected the beacon signals of other pallets, so in the beacon signal transmitted by wireless tag #B, the detection information for the beacon signals of other wireless tags is "OFF".

The wireless tag reader transmits the received identification information and detection information (B/OFF) of wireless tag #B to the pallet management device. The pallet management device can confirm that the pallet with wireless tag #B attached has been stored in the warehouse.

Wireless tag #A detects the beacon signal transmitted by other wireless tag #B using its built-in passive wireless element, and upon detecting the presence of other wireless tag #B, it transmits a beacon signal (A/ON) containing the identification information of wireless tag #A and the detection information of the beacon signal of other wireless tag B to the wireless tag reader. Because wireless tag #A has detected the beacon signal of another pallet, in the beacon signal transmitted by wireless tag #A, the detection information of the beacon signal of the other wireless tag becomes "ON".

When the wireless tag reader 30 receives a beacon signal (A/ON) from wireless tag #A, which includes detection information indicating that a beacon signal transmitted by another wireless tag has been detected, it associates the received identification information of wireless tag #A with the detection information of the beacon signal from the other wireless tag, and transmits the associated information to the pallet management device.

The pallet management device receives the identification information of wireless tag #A and the detection information of the beacons of other wireless tags, updates the wireless tag status management data in Figure 5, and changes the status of the pallet on which wireless tag #A is installed to "empty."

In the same way, wireless tag #B detects the beacon signal transmitted by other wireless tag #A using its built-in passive wireless element, and when it detects the presence of another wireless tag, it transmits a beacon signal (B/ON) to the wireless tag reader, which has the identification information of wireless tag #B and the detection information of the beacon signal of the other wireless tag B set to "ON."

The pallet management device receives the identification information of wireless tag #B and the detection information of the beacons of other wireless tags, updates the wireless tag status management data in Figure 5, and changes the cargo status of wireless tag #B to "empty."

By associating and managing the identification information of the wireless tag with the detection information of the beacons of other wireless tags, it is possible to grasp the status of the pallet carrying the wireless tag. If the detection information includes information indicating that a beacon signal from another wireless tag has been received, it can be determined that the pallet is stacked and is an empty pallet with no cargo placed on it.

<Flowchart>
FIG. 7 is an example of a control flowchart for the wireless tag installed on the pallet in the first embodiment of the present invention.

The pallet on which the wireless tag is installed moves (S1-1), and the wireless tag transmits a beacon signal at a predetermined interval determined in the moving mode (S1-2).

When the pallet with the wireless tag attached is stored in the warehouse (S1-3), the operation mode is changed from the mobile mode to the association mode (S1-4). The wireless tag transmits a beacon signal at a predetermined interval determined in the association mode (S1-5).

When a wireless tag detects a beacon signal from another wireless tag (S1-6), the detection flag for the beacon signal from the other wireless tag turns "ON" (S1-7), and a beacon signal with the detection flag turned "ON" is transmitted (S1-8).

After that, while the pallet on which the wireless tag is installed is stored in the warehouse, beacon signals are repeatedly sent and received between the wireless tag reader and the pallet. Also, when the wireless tag no longer detects the beacon signals of other wireless tags, a beacon signal is transmitted that sets the detection flag of the beacon signal of the other wireless tag to "OFF." Here, the wireless tag reader may be configured to set the detection information of the wireless tag to "OFF" when it receives beacon signals that set the detection flag to "OFF" multiple times.

Second Embodiment
In the first embodiment, the present invention is described as being applied to a system using a plastic pallet, whereas in the second embodiment, the present invention is described as being applied to a system using a metal pallet combined with metal structural members.

<Palette composition>
Figures 8A-8C are configuration examples of a pallet in the second embodiment. The pallet in the second embodiment is configured by combining metal structural members. Figure 8A is a top view of a pallet 20, Figure 8B is a side view of the pallet 20 in Figure 8A, and Figure 8C is a side view of the pallet 20 in Figure 8A in B. In the configuration example of Figures 8A-8C, the wireless tag 10 is located in the center of the pallet 20 in a plan view, surrounded by a rectangular frame 26 made of a metal structural member, and is disposed in a space in the vertical direction of the pallet 20 where there are no metal structural members.

The wireless tag 10 may be positioned so that the metal structural members around the wireless tag 10 do not interfere with the radio waves transmitted by the wireless tag. For example, the wireless tag 10 may be placed in the center of a container molded from resin, and then surrounded by metal structural members formed on the pallet 20, and placed in a space that is free of metal structural members in the vertical direction.

In this embodiment, the rectangular frame 26 and the wireless tag 10 are configured to have a distance of at least 1/3 of the wavelength of the radio waves used by the wireless tag 10. This ensures the antenna gain of the wireless tag 10, and the beacon transmitted by the wireless tag 10 can be reliably received by the wireless tag reader 30.

For example, if the radio wave frequency used by the wireless tag 10 is in the 920 MHz band (wavelength: 325 mm), the distance between the rectangular frame 26 and the wireless tag 10 should be 150 mm. Note that as long as the distance between the wireless tag 10 and the surrounding metal structural members is secured, the shape of the metal structural members surrounding the wireless tag 10 is not limited to a rectangle.

A support section 21 is erected on the edge of the long side of the pallet 20. The support section 21 is composed of a base member 23 fixed to the pallet 20 and a support member 22 installed on the top of the base member. The support section 21 is equipped with an alignment means for aligning the upper pallet with the lower pallet when stacking the pallets. In the configuration example of Figures 8A-8C, a hole section 24 is provided in the lower part of the base member 23 as an alignment means. This hole section 24 is configured so that the upper end of the support member 22 can be fitted into it.

By fitting the upper ends of the support members 22 of the pallet 20 placed below into the holes 24 of the base member 23 of the pallet 20 placed above, multiple pallets 20 can be stacked one on top of the other with cargo loaded on the pallets 20.

<Configuration of stacked empty pallets>
Figures 9A to 9C are examples of the configuration of a pallet in the second embodiment. Figure 9A is a diagram showing a state in which the support members 22 in Figure 8B are bent. When the support members 22 are bent, they are configured so that the protruding height from the pallet 20 is the same as the height of the base member 23.

Even when the support member 22 is bent, the support section 21 has an alignment means for aligning the upper pallet with the lower pallet when stacking the pallets. In the configuration example of FIG. 9A, the upper end of the base member 23 is provided with a protrusion 25. The protrusion 25 is configured to appear at the upper end of the base member 23 when the support member 22 is bent, and is configured so that it can fit into a hole 24 provided in the lower part of the base member 23.

Figures 9B and 9C show a state in which multiple empty pallets 20 with no cargo loaded are stacked. When the support members 22 are bent, the protrusions 25 of the pallet 20 placed below can be fitted into the holes 24 of the pallet 20 placed above, allowing multiple empty pallets 20 with no cargo loaded to be stacked one above the other in close proximity to each other. When stacking the pallets, the protrusions 25 of the support members 21 are configured to fit into the holes 24. This makes it possible to achieve a stacking configuration in which the upper and lower pallets 20 are not misaligned, compared to the case in which the resin pallets of the first embodiment are stacked.

The wireless tag 10 is located in the center of the pallet 20 in a plan view, surrounded by a rectangular frame 26 made of metal structural members, and is arranged in a space that is free of metal structural members in the vertical direction of the pallet 20. This allows for a stacked configuration without misalignment of the upper and lower pallets 20, making it possible to accurately align the wireless tag 10 mounted on the pallet 20 in the vertical direction.

As with the first embodiment, the position of the rectangular frame 26 in which the wireless tags 10 are placed on each pallet is not limited to the center of each pallet as long as the beacon signals of other tags can be received when stacked, but it is preferable to place the tag in the center of the pallet in a planar view. If multiple pallets are placed adjacent to each other in a planar view, placing the rectangular frame 26 in which the wireless tags 10 are placed in the center of the pallet will result in adjacent wireless tags being placed at the furthest positions, preventing erroneous detection of the beacons of wireless tags 10 adjacent to the left and right.

Furthermore, in the center of the stacked pallets 20, a vertical space is formed by a rectangular frame 26 made of metal structural material surrounding the wireless tag 10. The rectangular frame 26 and the wireless tag 10 are configured to ensure a distance of at least 1/3 of the wavelength of the radio wave frequency used by the wireless tag 10, so that the waveguide effect of this space ensures that beacon signals transmitted by wireless tags installed on other pallets 20 can be reliably detected even when the distance between the wireless tags 10 is relatively large.

Note that due to the above-mentioned waveguide effect, the installation position of the wireless tag 10 within the rectangular frame 26 is tolerant of installation errors within the range in which the beacon signal can be detected. For example, if the frequency of the radio waves used by the wireless tag 10 is in the 920 MHz band, even if there is an installation error within the range of the wavelength of the radio waves used by the wireless tag 10, for example, about 300 mm, it is possible to detect the beacon signal transmitted by other wireless tags.

The results of the verification of beacon detection when metal pallets are stacked will be explained using Figures 10 and 11. Figure 10 shows an example of the configuration of stacked pallets used to verify beacon detection. In Figure 10, it is made up of 11 layers of metal pallets 20 (No. 1 to No. 11) with wireless tags 10 installed, and the vertical spacing between the pallets 20 is approximately 22 cm. In the case of the metal pallets in Figures 9A-9C, the distance between the pallets is greater than that of plastic pallets due to the presence of bent support members 22.

Figure 11 is an example of the verification result of beacon detection in the configuration of Figure 10. Figure 11 shows the result of receiving beacon signals multiple times from the wireless tags 10 installed on each pallet 20 in association mode, and measuring the percentage of beacon signals that contain detection information of beacon signals of other wireless tags (tag detection ON). For example, in the case of wireless tag No. 1, out of the 12 beacon signals received, 12 beacons contain detection information of beacon signals of other wireless tags.

The verification results in Figure 11 show that in a stacking configuration of 11 high pallets 20, other beacon signals could be detected with a 100% probability. This confirms that when metal pallets are stacked, even if the distance between the pallets is greater than that of plastic pallets, other beacon signals can be detected with a high probability, thereby making it possible to determine the status of the pallet.
<Other embodiments>

In the above configuration example, a configuration in which the pallet 20 has four support sections 21 has been described as an example, but the number of support sections 21 is not limited to four. Depending on the size and shape of the pallet, a number of support sections greater than four may be provided.

In the above configuration example, the pallet 20 has four support posts 21 with protrusions at the top and holes at the bottom, but other configurations may be used as long as the upper and lower pallets can be aligned. For example, the support posts 21 may have holes at the top and protrusions at the bottom, or, instead of holes, a locking member may be provided that prevents the support posts 21 from sliding in a plan view.

Furthermore, the pallet 20 does not need to have projections and holes on all four support columns 21; for example, it may be configured so that two or three of the four support columns 21 have projections and holes.

In this way, according to an embodiment of the present invention, the status of a pallet carrying a wireless tag can be ascertained by associating and managing the identification information of a wireless tag with the detection information of the beacons of other wireless tags. If the beacon signal transmitted by the wireless tag contains detection information indicating that a beacon signal from another wireless tag has been received, the pallet can be determined to be stacked and is an empty pallet with no cargo placed on it.

According to this embodiment, it is possible to provide a pallet management technology that can manage the status of a pallet without adding equipment for acquiring an image of the pallet or changing the configuration of the pallet to measure the height of the pallet.

1...warehouse, 2...pallet, 5...forklift, 10...wireless tag, 11...antenna, 12...wireless unit, 13...vibration sensor, 14...passive wireless element, 15...battery, 16...central processing unit, 17...memory, 20...pallet (made of metal), 21...support unit, 22...support member, 23...base member, 24...hole, 25...projection, 26...rectangular frame, 30...wireless tag reader, 31...antenna, 32...wireless unit, 33...I/F unit, 34...central processing unit, 35...memory, 40...pallet management device, 50...network.

Claims (6)

A pallet management system including a wireless tag attached to a pallet, a wireless tag reader that receives a beacon signal transmitted by the wireless tag, and a pallet management device,
The wireless tag includes a wireless transmission means for transmitting a beacon signal including identification information unique to the wireless tag, and a beacon detection means for detecting a beacon signal transmitted by another wireless tag stacked thereon;
the first wireless tag is configured to transmit, to the wireless tag reader, a beacon signal including detection information indicating that the first wireless tag has detected a beacon signal transmitted by the second wireless tag using the beacon detection means;
the wireless tag reader transmits the identification information of the first wireless tag and the detection information to the pallet management device in association with each other;
The pallet management device manages the status of the pallet on which the first wireless tag is installed based on the identification information of the first wireless tag and the detection information, and when the detection information associated with the identification information of the first wireless tag indicates that a beacon signal transmitted by the second wireless tag has been detected, determines whether the pallet on which the first wireless tag is installed is an empty pallet with no cargo placed on it. A pallet management system. 2. The pallet management system according to claim 1 , wherein the beacon detection means is a passive wireless element that does not require power supplied from a power source. The pallet is constructed by combining metal structural members,
3. The pallet management system according to claim 1, wherein the wireless tag is surrounded by the metal frame material and is arranged in a space above and below the pallet that is free of the metal frame material. The pallet management system according to claim 3 , wherein the wireless tag is disposed at the center of the pallet in a plan view. 5. A pallet management system as described in claim 3 or 4, wherein the pallet has at least four support members at predetermined positions on the edge of the pallet when viewed in a plane, and at least two of the support members have alignment means for aligning an upper pallet with a lower pallet when the pallets are stacked. The pallet management system according to claim 5, wherein the at least two support members are provided with the alignment means consisting of a protrusion or a hole at their upper and lower parts, and when the pallets are stacked, the upper pallet and the lower pallet are aligned by the protrusion and the hole engaging with each other.

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