JP2023072130A - Radio communication device, radio communication system, and roaming method - Google Patents

Abstract

To provide a radio communication device capable of executing stable roaming in a short time.SOLUTION: A radio communication device reads or acquires from the outside a roaming start condition in which position information showing a position of a mobile body, direction information showing a direction in which the mobile body approaches the position shown by the position information, and a radio wave intensity threshold showing a threshold of a lower limit of radio wave intensity for permitting connection by roaming are associated. The radio communication device sets the radio wave intensity threshold on the basis of a detection value of the position information on the mobile body, a detection value of the direction information on the mobile body, and the roaming start condition and determines whether a new access point device providing radio wave intensity equal to or higher than the radio wave intensity threshold exists. When it is determined that the new access point device providing radio wave intensity equal to or higher than the radio wave intensity threshold exists, the radio communication device disconnects connection between a radio communication module and an access point during connection and connects the radio communication module to the new access point device providing the radio wave intensity equal to or higher than the radio wave intensity threshold.SELECTED DRAWING: Figure 9

Description

The present invention relates primarily to wireless communication devices that perform roaming.

Patent Literature 1 discloses a method of appropriately switching the access point to which a communication terminal is connected when the communication terminal moves. When the radio wave reception level of the access point is lower than the threshold or the transmission packet error rate is higher than the threshold, the communication terminal starts the process of switching the access point. Moreover, Patent Document 1 also describes switching the magnitude of the threshold between two levels based on the reception level variation rate and the transmission packet error rate.

Japanese Patent No. 4993219

In the method of Patent Literature 1, the threshold to be applied is set after determining the communication environment at the current position. Therefore, it takes time to set the threshold, which may result in roaming delays. Therefore, the method of Patent Document 1 has room for improvement in the method of setting the threshold. In particular, in a wireless communication device that provides a wireless communication function to a mobile object, the position of the wireless communication device and the shape of the mobile object may affect the reception of radio waves, making it even more difficult to set an appropriate threshold. Met. In addition, with the method of Patent Document 1, roaming using an appropriate threshold may not be possible in a communication environment that changes moment by moment depending on the position of the mobile unit equipped with the wireless communication device and the moving direction of the mobile unit.

SUMMARY OF THE INVENTION The present invention has been made in view of the circumstances described above, and a main object thereof is to provide a wireless communication apparatus capable of performing stable roaming in a short time.

Means and Effects for Solving Problems

The problems to be solved by the present invention are as described above. Next, the means for solving the problems and the effects thereof will be described.

A first aspect of the present invention provides a wireless communication device having the following configuration. That is, the wireless communication device includes a wired communication module, a wireless communication module, and an arithmetic device. The wired communication module performs wired communication with the mobile control device. The wireless communication module wirelessly connects to an access point device to perform wireless communication. The computing device disconnects the currently connected access point device and the wireless communication module, and performs roaming to connect the wireless communication module to a new access point device. The computing device indicates position information indicating the position of the mobile object, direction information indicating the direction in which the mobile object enters the position indicated by the position information, and a lower limit threshold of radio wave intensity that permits connection by roaming. The roaming start condition associated with the radio field intensity threshold is read out or externally acquired. The computing device sets the radio field intensity threshold based on the detected value of the position information of the moving object, the detected value of the direction information of the moving object, and the roaming start condition, and sets the radio field intensity threshold. It is determined whether or not there are new access point devices above the threshold. The computing device disconnects the connected access point device and the wireless communication module when determining that the new access point device having the radio field intensity threshold or more exists, and Connect the wireless communication module to a new access point device.

As a result, since the radio field intensity threshold can be set based on the positional information and the direction information, roaming can be performed using an appropriate radio field intensity threshold according to the position and direction of approach of the moving body. In particular, by using the direction information, it is possible to cope with the case where the radio wave reception condition differs depending on the direction. As a result, appropriate roaming can be performed in a short time even under conditions of low radio wave intensity.

In the wireless communication device, the radio field intensity threshold of the roaming start condition is based on the radio field intensity of the access point device when the wireless communication module performed roaming in the past and connected to the access point device. preferably defined.

As a result, a highly reliable radio field intensity threshold can be set based on past performance.

The wireless communication device described above preferably has the following configuration. That is, when the new access point device having the radio field intensity threshold or more does not exist, the computing device sets a second radio field intensity threshold whose radio field intensity is smaller than the radio field intensity threshold, determines whether the new access point device exists. The computing device disconnects the currently connected access point device and the wireless communication module when determining that the new access point device having the second radio field intensity threshold or more exists, and Connect the wireless communication module to the new access point devices above the threshold.

Accordingly, even if there is no new access point device that satisfies the radio field intensity threshold, the wireless communication module can be connected to a new access point device with relatively high radio field intensity.

In the wireless communication device described above, it is preferable that the radio wave intensity threshold is divided into a plurality of stages according to the magnitude of the radio wave intensity.

This makes it possible to easily manage the radio field intensity threshold.

The wireless communication device described above preferably has the following configuration. That is, the computing device performs a process of storing the number of roaming executions for each access point device in association with the location information and the direction information. When the number of times of execution of roaming associated with the detected value of the position information of the mobile object and the detected value of the direction information of the mobile object is equal to or greater than a threshold, the arithmetic device performs access during connection. The connection between the point device and the wireless communication module is disconnected, and the wireless communication module is connected to the new access point device whose roaming execution count is equal to or greater than a threshold.

This allows connection to a new access point device based on past roaming results. In particular, by omitting the determination of the radio field intensity, appropriate roaming can be performed in a shorter time.

A second aspect of the present invention provides a wireless communication system including a plurality of wireless communication devices.

As a result, the present invention can be applied to a system in which a plurality of moving bodies exist.

Preferably, the wireless communication system further includes a storage device that stores the roaming start condition commonly used by the plurality of wireless communication devices.

As a result, when the roaming start condition is changed, it can be dealt with simply by updating the common roaming start condition.

According to a third aspect of the present invention, the following roaming method is provided. That is, in the roaming method, a wireless communication device that provides a wireless communication function to a mobile body control device located in a mobile body executes roaming. In the roaming method, positional information indicating the position of the mobile body, direction information indicating the direction in which the mobile body enters the position indicated by the positional information, and radio waves indicating the lower limit threshold of radio field strength for permitting connection by roaming A roaming start condition associated with a strength threshold is acquired. In the roaming method, the radio field intensity threshold is set based on the detected value of the position information of the mobile object, the detected value of the direction information of the mobile object, and the roaming start condition, and the radio wave intensity threshold is set. It is determined whether or not the new access point device described above exists. In the roaming method, when it is determined that the access point device having the radio field strength threshold or more exists, the connection between the currently connected access point device and the wireless communication device is disconnected, and the new access point having the radio field strength threshold or more is established. Connect the wireless communication device to the device.

As a result, since the radio field intensity threshold can be set based on the positional information and the direction information, roaming can be performed using an appropriate radio field intensity threshold according to the position and direction of approach of the moving body. In particular, by using the direction information, it is possible to cope with the case where the radio wave reception condition differs depending on the direction. As a result, appropriate roaming can be performed in a short time even under conditions of low radio wave intensity.

Schematic diagram of a wireless communication system. A block diagram of a carrier. 3 is a block diagram of a wireless communication device; FIG. 4 is a first half flowchart showing roaming by a wireless communication device; FIG. 4 is a second half of a flowchart illustrating roaming by a wireless communication device; FIG. A table showing radio field intensity threshold registration information. Ch. Table showing registration information. FIG. 4 is a diagram showing the travel area of the transport vehicle and the layout of the access point device; A table showing roaming related information. Flowchart showing forced roaming.

Embodiments of the present invention will now be described with reference to the drawings. First, with reference to FIG. 1, the overview of the wireless communication system 1 will be described.

The wireless communication system 1 of this embodiment is used in a workshop such as a factory or warehouse. As shown in FIG. 1, a work place is provided with a travel path 2 and a plurality of transport vehicles (moving bodies) 3 .

The running path 2 is, for example, a guiding tape such as a magnetic tape attached to the floor, or an identification tag such as a bar code. The transport vehicle 3 travels along the travel path 2 by detecting a guiding tape, an identification tag, or the like.

The transport vehicle 3 is, for example, an AGV (Automated Guided Vehicle) and can travel unmanned along the travel path 2 . The transport vehicle 3 receives and holds an article, travels to a destination, and delivers the article. Alternatively, the traveling path 2 may be a rail member, and the transport vehicle 3 may travel along the rail.

The transport vehicle 3 is equipped with a wireless communication device 16 as will be described later, and can perform wireless communication using this. In addition, a plurality of access point devices 4 are provided in the workplace. The access point device 4 can wirelessly communicate with the carrier 3 around itself. The access point device 4 is also connected to the wired LAN network of the workplace. A management device 5 is provided in the wired LAN network. That is, the carrier 3 can communicate with the management device 5 via the access point device 4 .

The management device 5 is, for example, a PC or a server, and manages and instructs transportation of articles. The management device 5 instructs a specific transport vehicle 3 to transport an article when an operation to transport an article occurs. Specifically, the management device 5 transmits the article receiving position and the article delivery position to the transport vehicle 3 . The route along which the carrier 3 travels from the receiving position to the delivery position may be searched and created by the management device 5 or may be searched and created by the carrier 3 .

Next, referring to FIG. 2, the configuration of the carrier 3 will be described in detail.

As shown in FIG. 2, the transport vehicle 3 includes a transport vehicle control device (moving body control device) 10, a wheel drive device 11, wheels 12, a lifter drive device 13, a lifter 14, a detector 15, and a wireless communication device 16 .

The carrier control device 10 has a CPU, ROM, RAM, storage, and the like. The CPU executes a program stored in the ROM to control the transport vehicle 3 . The wheel drive device 11 is a motor that drives the wheels 12 . The lifter drive device 13 is an actuator that drives the lifter 14 . The lifter 14 is a device for receiving articles, holding articles, and delivering articles. The wheel driving device 11 and the lifter driving device 13 are controlled by the carrier control device 10 .

The detector 15 is a reading device that detects the travel path 2 . The detector 15 detects the position and moving direction of the transport vehicle 3 based on the detection result of the travel path 2 . The position and moving direction of the carrier 3 detected by the detector 15 are output to the wireless communication device 16 via the carrier control device 10 . Further, the detector 15 may detect the position and moving direction of the carrier 3 by a method different from that of the present embodiment. For example, the position of the transport vehicle 3 may be detected using a BLE beacon, and the moving direction may be detected based on the change in the position of the transport vehicle 3 . Further, when the wireless communication system 1 is installed indoors, infrared rays or laser beams are emitted in a certain direction, changes in the infrared rays striking an object, or reflection timings are measured to determine the position of the transport vehicle 3. The moving direction may be detected based on the change in the position of the transport vehicle 3 . Alternatively, when the wireless communication system 1 is installed outdoors, a GNSS sensor may be used as the detector 15 to detect the position and moving direction of the carrier 3 .

The wireless communication device 16 provides the carrier control device 10 with a wireless communication function. The wireless communication device 16 will be described in detail below with reference to FIG. As shown in FIG. 3 , the wireless communication device 16 includes an arithmetic device 20 , a ROM 21 , a RAM 22 , a storage 23 , a wireless communication module 24 and a wired communication module 25 .

The arithmetic unit 20 is an SoC (System-on-a-chip) and includes a CPU, a communication modem, and the like. Arithmetic device 20 performs various controls over wireless communication device 16 by reading programs stored in ROM 21 into RAM 22 and executing them. Also, the storage 23 is, for example, a flash memory such as eMMC. The storage 23 stores information necessary for control (details will be described later).

The wireless communication module 24 is for performing wireless communication with the access point device 4 described above. The wireless communication module 24 includes a wireless antenna 24a, an unillustrated amplifier, and the like. The wired communication module 25 is for performing wired communication with the guided vehicle control device 10 . The wired communication module 25 includes a connector, a circuit for transmitting signals, and the like.

Next, roaming by the wireless communication device 16 will be described. In the following description, "the computing device 20 instructs to connect the wireless communication module 24 to the access point device 4" is simply referred to as "the wireless communication device 16 connects to the access point device 4". Describe.

In the workshop of this embodiment, one access point device 4 cannot cover all the travel paths 2 . Therefore, a plurality of access point devices 4 are provided. The wireless communication device 16 performs roaming when the radio wave strength of the connected access point device 4 (in other words, the strength of the received signal from the access point device 4 in the guided vehicle 3) decreases while the guided vehicle 3 is traveling. Execute. Roaming is switching the access point device 4 to which the wireless communication device 16 is connected.

In general roaming, a threshold value of radio wave intensity is set, an access point device 4 having a radio wave intensity equal to or higher than the threshold value is searched, and connection is established with the access point device 4 . However, since the radio wave environment changes according to the position of the wireless communication device 16, etc., it is not easy to set an appropriate threshold.

Factors affecting the radio wave environment will be explained. For example, as the distance to the access point device 4 increases, the intensity of the radio wave received by the wireless communication device 16 from the access point device 4 decreases. In addition, the radio wave environment may deteriorate due to shielding of radio waves or generation of multipaths due to the influence of devices, pillars, walls, etc., placed in the workplace. Thus, the radio wave environment changes according to the position of the wireless communication device 16 .

Furthermore, even if the position of the wireless communication device 16 is the same, the direction of approaching this position (for example, traveling in the first direction to enter the position, or), the radio wave environment may differ. This is because the radio antenna 24a may be attached at a position shifted from the center of the transport vehicle 3, so the positional relationship between the access point device 4 and the radio antenna 24a varies depending on the direction of approach to the position. be. Alternatively, only when approaching a location in a specific direction, a metal part of the transport vehicle 3 may be positioned between the access point device 4 and the wireless antenna 24a and the radio wave environment may deteriorate.

In particular, depending on the position and the direction of approaching the position, there is a possibility that a so-called dead spot, in which the radio wave intensity is significantly lower than the surroundings, may occur. If the guided vehicle 3 stops or travels at a low speed in a dead spot, as a result of the wireless communication device 16 attempting roaming, there may be no access point device 4 that satisfies the radio wave intensity condition, resulting in communication failure. As a result, a situation may arise in which the wireless communication device 16 cannot communicate with the management device 5 .

Considering the above, in the present embodiment, the radio wave intensity threshold is set according to not only the position but also the direction of approaching the position. Specific processing will be described below with reference to the flowcharts of FIGS. 4 and 5. FIG.

First, the wireless communication device 16 initializes the radio field intensity threshold Index to N=1 (S101). As shown in FIG. 6, the radio wave intensity threshold index is information for identifying stepwise radio wave intensity thresholds. In the present embodiment, the radio field intensity threshold is classified into four stages from N = 1 to 4, the index value of the radio field intensity threshold with the highest radio field intensity is 1 (N = 1), and the radio field intensity threshold with the lowest radio field intensity is 4 (N=4). It should be noted that the four stages are an example, and the radio wave intensity threshold may be divided into two stages, three stages, or five or more stages. In this embodiment, as shown in FIG. 6, the radio wave intensity threshold is represented by received power (dBm), but it may be represented by an S/N ratio (dB).

Next, the wireless communication device 16 selects Ch. Information Index is initialized to M=1 (S102). Ch. The information index is, as shown in FIG. 7, information for identifying a channel (frequency band) used by the access point device 4 for wireless communication. The channels used by the access point device 4 are predetermined. In this embodiment, as shown in FIG. 8, four access point devices 4 are provided, so the channel used by each access point device 4 is Ch. It is registered using the information index.

In this embodiment, the radio wave intensity threshold registration information shown in FIG. 6 and the Ch. The registration information is stored in advance in the wireless communication device 16 of each transport vehicle 3 . Note that the radio wave intensity threshold registration information and Ch. The registration information may be stored in the management device 5 or one specific wireless communication device 16 (hereinafter referred to as master device), and the wireless communication device 16 may access the master device to obtain the information.

Next, the wireless communication device 16 determines whether or not the radio field intensity confirmation interval has elapsed (S103). The radio field intensity confirmation interval is a time interval for confirming the radio field intensity of the connected access point device 4 in order for the wireless communication device 16 to determine whether or not roaming is to be executed.

When the wireless communication device 16 determines that the radio field intensity confirmation interval has elapsed, the radio communication device 16 determines the radio field intensity of the connected access point device and the Ch. Information is stored (S104). Further, the wireless communication device 16 stores position information and direction information of the carrier 3 (S105). In this embodiment, as shown in FIG. 8, the travel path 2 is divided into, for example, 46 blocks, and an ID (1 to 46) is assigned to each block to specify the position of the transport vehicle 3 . That is, the position information is the ID of the block shown in FIG.

The direction information is the direction to approach the position indicated by the position information. For example, when the transport vehicle 3 is positioned in block 1, it is information specifying whether it entered block 1 from the right (from block 2) or entered block 1 from below (from block 36).

Also, detection of position information and direction information is performed by the detector 15 as described above. FIG. 9 also shows position information, direction information, connected AP, used Ch. registered in steps S105 and S106. , a table showing roaming-related information is shown. Of the data shown in the table of FIG. 9, data in which position information, direction information, and a roaming execution index value, which will be described later, are associated with each other correspond to the roaming start condition.

The roaming-related information shown in FIG. 9 is created and updated independently by the wireless communication device 16 of each carrier 3 . Alternatively, common roaming-related information may be used by multiple wireless communication devices 16 . For example, the master device described above stores roaming-related information, and other wireless communication devices 16 access the master device to update or obtain roaming-related information. That is, the master machine corresponds to the "storage device" of the present application. Regarding the update of the roaming-related information shown in FIG. 9, if the information is different from the already stored information, it is additionally updated. Specifically, the line shown in FIG. 9 is added to store all items. On the other hand, if the information is the same as the stored information, all the items are not overwritten or recorded, and at least the value of the roaming execution count is incremented and updated.

Next, the wireless communication device 16 determines whether or not the radio field intensity of the connected access point device 4 is greater than or equal to the radio field intensity indicated by the radio field intensity threshold Index N=1 (S106). When determining that this condition is satisfied, the wireless communication device 16 returns to the process of step S103. If the wireless communication device 16 determines that this condition is not satisfied, that is, if the radio field strength of the currently connected access point device 4 is less than the maximum value of the radio field strength threshold, the process proceeds to step S107 and thereafter to execute roaming. do. Note that in the process of step S106, a different condition (threshold such as radio field intensity threshold Index N=2) may be set. Also, this threshold may be changed according to the position information and direction information.

If the wireless communication device 16 determines that the condition in step S106 is not satisfied (No in S106), it determines whether the roaming execution index value corresponding to the position information and direction information is 0 (S107). The roaming execution index value is the radio wave intensity threshold index value when roaming was executed in the past. If roaming has not been performed in the past, 0 is entered as the initial value. That is, in step S107, it is determined whether or not roaming was performed in the past with the same position information and direction information as at present.

When the roaming execution index value is not 0, the wireless communication device 16 refers to the roaming execution index value corresponding to the location information and direction information from the roaming related information table shown in FIG. 9, and updates the radio field intensity threshold index value. (S108). That is, if roaming was performed in the past with the same position and direction information as the current one, the radio field intensity threshold index value determined when roaming was performed in the past is set. When the roaming execution index value is 0, the wireless communication device 16 proceeds to the next step without updating the radio field intensity threshold index value (that is, maintaining N=1).

Further, in this embodiment, the wireless communication device 16 stores roaming-related information (including roaming start conditions), so the wireless communication device 16 reads the roaming-related information from the storage 23 . If the roaming-related information is stored in the master device other than the wireless communication device 16, the wireless communication device 16 accesses the master device to acquire the roaming-related information.

Next, the wireless communication device 16 selects Ch. Ch. is used to acquire the radio wave intensity (S109). Next, the wireless communication device 16 determines whether or not the acquired radio wave intensity of the access point device 4 is equal to or greater than the radio wave intensity threshold Index N (S110). In other words, in the situation where it was determined that roaming was performed in the past (situation where the location information and direction information are the same), whether or not the radio field strength (radio field strength indicated by the roaming execution index value) equal to or greater than that during past roaming could be obtained. judge.

If the acquired radio field intensity of the access point device 4 is less than the radio field intensity threshold Index N, the radio communication device 16 continues to perform Ch. , the access point device 4 is searched for. Specifically, Ch. When it is determined that the information Index M is not the upper limit (S111), Ch. The information index value is added (S112), and the processing of steps S109 and S110 is performed again.

When the wireless communication device 16 finds an access point device 4 with a radio field intensity threshold value equal to or higher than Index N (Yes in S110), the wireless communication device 16 receives the current location information, direction information, and AP information (name or ID of the access point device 4). , Ch. The information index value, the roaming execution index value, and the number of roaming executions are stored, and the roaming related information is updated (S113). Note that the storage of the number of roaming executions may be omitted.

Thereafter, after disconnecting from the connected access point device 4 (S114), the wireless communication device 16 connects to the new access point device 4 found by the search, that is, Ch. A connection is established with the access point device 4 of the information Index M (S115).

Also, the wireless communication device 16 is configured to use all Ch. If the access point device 4 having the radio wave intensity threshold value Index N or higher is not found even using the information index value (Yes in S111), Ch. Information Index M is initialized to 1 (S116).

Next, the wireless communication device 16 determines whether or not the radio field intensity threshold Index N is the upper limit (S117). The upper limit of the radio wave intensity threshold Index N means that the radio wave intensity threshold with the lowest radio wave intensity is set. When determining that the radio field intensity threshold Index N is not the upper limit, the radio communication device 16 adds the radio field intensity threshold Index value to lower the radio field intensity threshold (S118). After that, the wireless communication device 16 performs the processing from S109 to S117. In other words, the wireless communication device 16 gradually decreases the radio field intensity threshold until it finds an access point device 4 that satisfies the radio field intensity threshold.

Note that if it is determined in step S117 that the radio field intensity threshold Index N is the upper limit, there is no access point device 4 that meets the roaming conditions. Therefore, after a predetermined period of time has passed (S119), the wireless communication device 16 performs a process of disconnecting from the connected access point device 4 (S120). After that, although not shown in FIG. 5, the wireless communication device 16 that has performed disconnection processing (S120) with the currently connected access point device 4 is connected to the access point device 4 at startup that is registered in advance in the wireless communication device 16. for Ch. The radio field intensity of beacons transmitted from all access point devices 4 corresponding to the information is confirmed, and connection is established with the access point device 4 with the highest radio field strength.

As described above, in this embodiment, since the radio field intensity threshold is set according to the situation when roaming was performed in the past, an appropriate radio field intensity threshold can be set. As a result, appropriate roaming can be performed in a short time even under conditions of low radio wave intensity (for example, dead spots).

Also, if roaming has not been executed in the past under the same conditions as the present, the optimum radio field strength threshold must be determined and registered in order to search for the access point device 4 in order from the radio field strength threshold with the highest radio field strength. can be done.

Next, forced roaming will be described with reference to FIG.

Forced roaming is a process of connecting to a corresponding access point device 4 by omitting confirmation of the presence of the access point device 4 and confirmation of radio wave intensity when past roaming results are high. For example, if the forced roaming condition is met, forced roaming is performed, and if the forced roaming condition is not met, the above-described roaming (hereinafter referred to as normal roaming) is performed. A specific description will be given below.

Since the processing of steps S201 to S206 in FIG. 10 is the same as the processing in steps S101 to S106 of FIG. 4, description thereof will be omitted. If No in step S206, the wireless communication device 16 determines whether or not the number of roaming executions corresponding to the current location information and direction information is equal to or greater than a threshold (S207).

If the wireless communication device 16 determines that the number of roaming executions is equal to or greater than the threshold, the wireless communication device 16 stores the same information as in step S113 (S208), and then disconnects from the connected access point device 4 (S209). Then, the wireless communication device 16 connects to the access point device 4 corresponding to the location information and direction information in the roaming-related information (S210).

Further, when determining that the number of roaming executions is not equal to or greater than the threshold, the wireless communication device 16 executes normal roaming (S211). Specifically, the wireless communication device 16 performs the processes after step S109. In the description of normal roaming, the number of roaming executions in step S113 can be omitted, but when performing forced roaming, it is necessary to store the number of roaming executions.

Forced roaming can be switched between execution and non-execution. For example, when an access point device 4 is added or a device affecting transmission and reception of radio waves is introduced, the radio wave environment may change. In this case, temporarily disable forced roaming and update the roaming-related information. After that, after the administrator or the management device 5 determines that sufficient roaming-related information has been collected, the forced roaming can be enabled to cope with changes in the radio wave environment.

As described above, the wireless communication device 16 of this embodiment includes the wired communication module 25, the wireless communication module 24, and the arithmetic device 20. FIG. The wired communication module 25 performs wired communication with the guided vehicle control device 10 . The wireless communication module 24 wirelessly connects to the access point device 4 to perform wireless communication. The computing device 20 disconnects the currently connected access point device 4 and the wireless communication module 24 and performs roaming to connect the wireless communication module 24 to a new access point device 4 . The computing device 20 receives position information indicating the position of the guided vehicle 3, direction information indicating the direction in which the guided vehicle 3 enters the position indicated by the position information, and radio waves indicating the lower limit threshold of the radio wave intensity for permitting connection by roaming. A roaming start condition associated with a strength threshold is read out or externally acquired. The computing device 20 sets a radio wave intensity threshold value based on the detected value of the position information of the guided vehicle 3, the detected value of the direction information of the guided vehicle 3, and the roaming start condition, and sets a new radio wave intensity threshold value or more. It is determined whether or not the access point device 4 exists. When the computing device 20 determines that there is a new access point device 4 with a radio field strength threshold or higher, the computing device 20 disconnects the currently connected access point device 4 and the wireless communication module 24, and allows new access with a radio field strength threshold or higher. A wireless communication module 24 is connected to the pointing device 4 .

As a result, since the radio field intensity threshold can be set based on the positional information and the direction information, roaming can be performed using an appropriate radio field intensity threshold according to the position and direction of approach of the moving body. In particular, by using the direction information, it is possible to cope with the case where the radio wave reception condition differs depending on the direction. As a result, appropriate roaming can be performed in a short time even under conditions of low radio wave intensity.

In the wireless communication device 16 of the present embodiment, the radio field intensity threshold of the roaming start condition is based on the radio field intensity of the access point device 4 when the wireless communication module 24 executed roaming in the past and connected to the access point device 4. Determined.

As a result, a highly reliable radio field intensity threshold can be set based on past performance.

In the wireless communication device 16 of the present embodiment, if there is no new access point device 4 having a radio field intensity threshold (for example, radio field intensity threshold Index N=1) or more, the computing device 20 has a radio field intensity smaller than the radio field intensity threshold. A second radio field intensity threshold (for example, radio field intensity threshold Index N=2) is specified, and it is determined whether or not there is a new access point device 4 having a radio field intensity threshold greater than or equal to the second radio field intensity threshold. When determining that there is a new access point device 4 with a radio field intensity equal to or higher than the second threshold, the computing device 20 disconnects the currently connected access point device 4 from the wireless communication module 24, The wireless communication module 24 is connected to the new access point device 4 in .

As a result, even if there is no new access point device 4 that satisfies the radio field intensity threshold, the wireless communication module 24 can be connected to a new access point device 4 with relatively high radio field intensity.

In the wireless communication device 16 of this embodiment, the radio field intensity threshold is divided into a plurality of stages according to the magnitude of the radio field intensity.

This makes it possible to easily manage the radio field intensity threshold.

In the wireless communication device 16 of the present embodiment, the computing device 20 stores the number of roaming executions for each access point device 4 in association with the location information and direction information. If the number of roaming executions associated with the detected value of the position information of the guided vehicle 3 and the detected value of the direction information of the guided vehicle 3 is equal to or greater than a threshold, the arithmetic device 20 determines whether the currently connected access point device 4 , the wireless communication module 24 is disconnected, and the wireless communication module 24 is connected to a new access point device 4 whose roaming execution count is equal to or greater than the threshold.

As a result, it is possible to connect to a new access point device 4 based on past roaming results. In particular, by omitting the determination of the radio field intensity, appropriate roaming can be performed in a shorter time.

The wireless communication system 1 of this embodiment includes a plurality of wireless communication devices 16 .

As a result, the present invention can be applied to a system in which a plurality of moving bodies exist.

The wireless communication system 1 of this embodiment includes a storage device (master device) that stores roaming start conditions commonly used by a plurality of wireless communication devices 16 .

As a result, when the roaming start condition is changed, it can be dealt with simply by updating the common roaming start condition.

Although the preferred embodiments of the present invention have been described above, the above configuration can be modified, for example, as follows.

The flowcharts shown in the above embodiments are examples, and some of the processes may be omitted, the contents of some of the processes may be changed, or new processes may be added.

In the above embodiment, information such as the roaming execution index value is updated, but updating is not essential. For example, a roaming execution index value corresponding to all position information and direction information may be determined by performing a test run, simulation, or the like before starting operation of the workplace.

In the above embodiment, each stage of the radio field intensity threshold is managed using the index value, but each process may be performed without using the index value (that is, by directly using the radio field intensity threshold).

In the above-described embodiment, the radio field intensity thresholds are divided in stages, but this division may be omitted. For example, a specific radio wave intensity (eg, -63.2 dBm) when roaming is performed may be registered, and the registered value (-63.2 dBm) may be used as it is as the radio wave intensity threshold.

Forced roaming is not a mandatory process and can be omitted.

In the above embodiment, an example in which the present invention is applied to a workshop such as a factory or warehouse has been described, but the present invention can also be applied to other places such as hospitals, schools, offices, and other facilities. Further, instead of the transport vehicle 3, a moving body that does not have a function of transporting articles can be used. Furthermore, instead of the transport vehicle 3, a moving object having no wheels (for example, an flying object) can be used.

1 wireless communication system 2 travel path 3 carrier (moving body)
4 access point device 5 management device 16 wireless communication device 20 arithmetic device 24 wireless communication module 25 wired communication module

Claims (8)

In a wireless communication device that provides a wireless communication function to a mobile control device located in a mobile,
a wired communication module that performs wired communication with the mobile control device;
a wireless communication module that wirelessly connects to an access point device and performs wireless communication;
a computing device that disconnects the currently connected access point device and the wireless communication module and executes roaming to connect the wireless communication module to a new access point device;
with
The arithmetic unit indicates position information indicating the position of the mobile object, direction information indicating the direction in which the mobile object enters the position indicated by the position information, and a lower limit threshold of radio wave intensity that permits connection by roaming. reading or externally acquiring the roaming start condition associated with the radio field intensity threshold,
The computing device sets the radio field intensity threshold based on the detected value of the position information of the moving object, the detected value of the direction information of the moving object, and the roaming start condition, and sets the radio field intensity threshold. determining whether or not there are new access point devices equal to or greater than a threshold;
The computing device disconnects the connected access point device and the wireless communication module when determining that the new access point device having the radio field intensity threshold or more exists, and A wireless communication device, wherein the wireless communication module is connected to a new access point device. The wireless communication device according to claim 1,
The radio wave intensity threshold of the roaming start condition is determined based on the radio wave intensity of the access point device when the wireless communication module executed roaming in the past and connected to the access point device. Communication device. The wireless communication device according to claim 1 or 2,
The computing device sets a second radio field intensity threshold whose radio field intensity is smaller than the radio field intensity threshold when the new access point device having the radio field intensity threshold or more does not exist, and determining whether a new access point device exists,
The computing device disconnects the currently connected access point device and the wireless communication module when determining that the new access point device having the second radio field intensity threshold or more exists, and A wireless communication device, wherein the wireless communication module is connected to the new access point device equal to or greater than a threshold. The wireless communication device according to any one of claims 1 to 3,
The radio communication apparatus, wherein the radio field intensity threshold is divided into a plurality of stages according to the magnitude of the radio field intensity. The wireless communication device according to any one of claims 1 to 4,
the computing device stores the number of roaming executions for each access point device in association with the location information and the direction information;
When the number of times of execution of roaming associated with the detected value of the position information of the mobile object and the detected value of the direction information of the mobile object is equal to or greater than a threshold, the arithmetic device performs access during connection. A wireless communication device that disconnects a point device and the wireless communication module, and connects the wireless communication module to the new access point device whose roaming execution count is equal to or greater than a threshold. A wireless communication system comprising a plurality of wireless communication devices according to any one of claims 1 to 5. A wireless communication system according to claim 6,
A radio communication system comprising a storage device for storing the roaming start condition commonly used by a plurality of the radio communication devices. In a roaming method for causing a wireless communication device that provides a wireless communication function to a mobile control device located in a mobile body to perform roaming,
location information indicating the location of the mobile object, direction information indicating the direction in which the mobile object enters the location indicated by the location information, and a radio wave intensity threshold indicating the lower limit of the radio wave intensity for permitting connection by roaming; Acquire the roaming start condition associated with
setting the radio field intensity threshold based on the detected value of the position information of the mobile object, the detected value of the direction information of the mobile object, and the roaming start condition; determining whether an access point device is present;
When it is determined that the new access point device having the radio field intensity threshold or more exists, the connection between the currently connected access point device and the wireless communication device is disconnected, and the new access point device having the radio field intensity threshold or more A roaming method, comprising connecting the wireless communication device.

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