JP2003032267A - Device and method for switching master station in communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always transmit precise information in radio communication between a radio carrier and respective stages. SOLUTION: Whether the moving direction of a slave station 200 is the direction where it drives away from a specified master station 100. When the moving direction of the slave station 200 is determined to be the direction where it drives away form the specified master station 100, switch request data of the master station 100 is added to a token circulating in a communication path 300. When the master station 120 receives the token, to which switch request data is added, whether communication with the slave station 200 is possible. When communication with the slave station 200 is determined to be possible, switch response data of the master station 120 is added to the token circulating in the communication path 300. The object of communication with the slave station 200 is switched to the other master station 120 from the specified master station 100, according to switch response data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, wireless communication performed between an automated guided vehicle and each stage,
The present invention relates to a master station switching device and a master station switching method in a communication system, which switches a master station to perform wireless communication according to the movement of an automatic guided vehicle.

[0002]

2. Description of the Related Art A vehicle production line is provided with a plurality of stages for performing different operations on an automobile conveyed by a conveyor. Further, in the production line, a plurality of unmanned transport vehicles for transporting parts necessary for the work of each stage are arranged.

The automated guided vehicle wirelessly communicates with a production device provided in each stage in order to convey the components necessary for each stage without excess or deficiency. In order to perform this communication, a radio is connected to the automatic guided vehicle and the production device. In the present specification, hereinafter, the wireless device connected to the automated guided vehicle side is referred to as a "slave station", and the wireless device connected to the production device side is referred to as a "master station".

Usually, the master station is arranged along the transport route of the automatic guided vehicle so that it can communicate with the slave station mounted on the automated guided vehicle. And conventionally, in consideration of reliability, real-time property, and environmental resistance, for the communication, a cyclic transmission that can transmit information by circulating tokens between parent stations within a certain time is adopted. There is.
These master stations have a range (communication range) in which communication with the slave stations is possible. Therefore, each time the slave station approaches another stage, the slave station switches the communication target from the master station that has been communicating until then to the master station arranged in the next stage.

Conventionally, the switching of the master station by the master station switching device is performed by the following two methods. One is a method in which when the communication between the slave station and the master station becomes unstable or impossible, the master stations communicate with each other and switch to a master station that can communicate with the slave station. , A method in which a slave station selects a master station with which it can communicate and communicates.

[0006]

However, in such a conventional master station switching device as described above, both of the above two methods are effective when the communication between the slave station and the master station becomes unstable or impossible. , The communication between the master station and the slave station is temporary because the process of switching the communication target was performed for the first time, but there is a risk of disconnecting from the cyclic transmission, and information is transmitted accurately. It is possible that it will not be forgotten.

The present invention has been made in view of the above problems of the conventional master station switching device, and performs a process of switching the communication target according to the movement of the slave station, so that accurate information is always available. An object of the present invention is to provide a master station switching device and a master station switching method in a communication system, which enables transmission.

[0008]

[Means for Solving the Problems] In order to solve the above problems,
In order to achieve the object, a master station switching device in a communication system according to a first aspect of the present invention is a slave station in which a plurality of master stations are connected by wire communication and are movable with respect to each master station. Is a master station switching device in a communication system that circulates tokens in a communication path that is communicably connected to each master station wirelessly, and that communicates between the master station and the slave station, Communication range departure possibility determining means for determining whether or not there is a possibility that this mobile station will leave the communication range with a particular parent station that is in communication due to movement of the mobile station When it is determined by the means that there is a possibility of leaving the communication range with the specific master station, switching request data adding means for adding the master station switch request data to the token circulating in the communication path. , The switching request data When the token with the added data is received, the communication availability determination means for determining whether or not the communication with the slave station is possible, and when it is determined that the communication with the slave station is possible, Switching response data adding means for adding switching response data of the master station to the token circulating in the communication path, and a target of communication with the slave station from the specific master station according to the switching response data. It has a switching means for switching to another master station.

A master station switching device in a communication system according to a second aspect of the present invention is the master station switching device in the communication system according to the first aspect, wherein the communication area departure possibility determining means is the slave station. It is characterized in that it is judged whether or not there is a possibility that the slave station will leave the communication range with the specific master station with which it is communicating, based on a change in the intensity of the radio wave received during the communication.

A master station switching device in a communication system according to a third aspect of the present invention is the master station switching device in the communication system according to the first aspect, wherein the communication permission / inhibition determining means is in communication with the slave station. It is characterized in that whether or not communication with the slave station is possible is determined based on the strength of the received radio wave.

A master station switching device in a communication system according to a fourth aspect of the present invention is the master station switching device in the communication system according to the first aspect, wherein the communication area departure possibility determining means and the switching request data addition The means, the communication availability determining means, and the switching response data adding means are provided in each master station.

A master station switching device in a communication system according to a fifth aspect of the invention is the master station switching device in the communication system according to the first aspect, wherein the switching means is
It is characterized in that it is provided in either each slave station or each master station.

According to a sixth aspect of the present invention, there is provided a master station switching method in a communication system, wherein a plurality of master stations are connected by wire so that they can communicate with each other. A master station switching method in a communication system in which a token is circulated in a communication path wirelessly connected to a master station and communication is performed between the master station and the slave station, There is a possibility that the mobile station may leave the communication range with the specific master station with which it is communicating, and the possibility that the mobile station may leave the communication range with the specific master station. When it is determined, the step of adding the switching request data of the master station to the token circulating in the communication path, and the communication with the slave station when the token to which the switching request data is added is received. Determine whether or not And floor, when it is determined that it is possible to communicate with the slave station includes the steps of adding a switch response data of the master station to the token circulating on the communication path,
Switching the target of communication with the slave station from the specific master station to another master station according to the switch response data.

[0014]

As described above, according to the present invention, since the communication target is switched according to the movement of the slave station, the communication between the slave station and the master station becomes unstable or impossible. Before that, the master station that communicates with the slave station can be switched, and accurate information can always be transmitted.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a master station switching device in a communication system according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of a communication system to which the present invention is applied.

This communication system is provided, for example, in an automobile production line. This communication system includes two master stations 100 and 120 and three slave stations 20.
0, 220, 240. Master station 100, 12
0 is usually fixedly provided on a stage for assembling an automobile, and is connected to a production machine provided on the stage. The parent station 100 and the parent station 120 are connected by wire to form a wired LAN 300 such as Ethernet. On the other hand, the respective slave stations 200, 220, 240 and the respective master stations 100, 120 are wirelessly connected via the antennas 110, 130, 210, 230, 250 provided respectively. The slave stations 200, 220, 240 are attached to an automated guided vehicle that travels on a transport route set in the production line.

The parent stations 100 and 120 include slave stations 200 and 2
There is a unique range (communication range) in which communication with 20, 240 is possible. Therefore, the slave stations 200, 220, 240
Switches between the parent stations 100 and 120 to communicate with, depending on which parent station 100 or 120 the communication area of the automated guided vehicle is traveling in. In order to perform this switching, each master station 10
0, 120 and each slave station 200, 220, 240 are configured as follows.

FIG. 2 is a block diagram showing a schematic configuration of the master station, and FIG. 3 is a block diagram showing a schematic configuration of the slave station.
It should be noted that any of the master stations and slave stations has the same configuration as those shown in the block diagrams.

As shown in FIG. 2, the master station 100 includes a moving direction judging section 102, a switching request data adding section 104, a communication availability judging section 106, and a switching response data adding section 108.

The moving direction determining unit 102 includes an antenna 110.
It is determined whether or not the moving direction of the slave station connected to the master station 100 is away from the master station 100 based on the change in the radio wave intensity of the slave station received via the antenna 110. For example, as shown in FIG.
If the strength of the radio wave received from the slave station 200 is decreasing with time while communicating with the slave station 200, it is determined that the slave station 200 is moving away from the master station 100. By this determination, it is determined whether or not there is a possibility that the child station 200 will leave the communication range of the parent station 100.

In this embodiment, it is determined whether or not communication may be interrupted based on the distance between the slave station and the master station. However, if there is an obstacle between the two stations, However, since communication may be interrupted, the positional relationship between the master station and the slave station may be recognized. That is, it may be possible to determine whether or not the communication between the slave station and the master station may be interrupted by recognizing the position of the slave station, such as when the slave station is behind the machine.

When it is determined that the slave station 200 is moving away from the master station 100, the moving direction determining section 102 outputs a start signal to the switching request data adding section 104 to inform that effect.

The switching request data addition unit 104 receives the activation signal from the moving direction determination unit 102 and receives the wired LAN 30.
Receive the token circulating in 0, add the master station switching request data to the received token,
Output to AN300.

The communication propriety determining unit 106 includes a wired LAN 30.
When a token circulating in 0 is received and the switching request data is added to the token, it is determined whether there is a communicable slave station while switching the communication frequency.

For example, as shown in FIG.
When the master station 100 is moving away from the master station 100, the switch request data adding section 104 of the master station 100 sends the switch request data. However, when the master station 120 receives the switch request data, whether the master station 120 can communicate or not. The determination unit 106 tunes the communication frequency to the slave station 200, tries the communication with the slave station 200, and determines whether or not communication is possible based on the strength of the radio wave received at that time. The determination as to whether communication is possible is based on the strength of the radio wave.
06 is determined to be communicable because communication will be normally performed if a radio wave having a certain strength or more is received,
Communication is determined to be impossible unless radio waves of a certain strength or more are received.

When it is determined that the communication is possible, the communication availability determination unit 106 outputs a start signal to the switching response data addition unit 108 in order to notify that effect.

The switching response data adding unit 108 receives the activation signal from the communication availability determining unit 106 and receives the wired LAN 30.
Receives a token that circulates within 0, adds switching response data to the received token, and
Output to 00.

On the other hand, the slave station 200 is provided with a master station switching section 202 as shown in FIG. Master station switching unit 202
Is for switching the communication target (master station) with the slave station 200 based on the switch response data included in the communication data with the master station. The switching of the master station to be the target of communication is performed by switching the communication frequency.

For example, when the slave station 200 is communicating with the master station 100 and the communication target is switched from the master station 100 to the master station 120, the master station switching section 202 changes the communication frequency to the master station. From the communication frequency with the station 100, the master station 1
Switch to the communication frequency with 20.

In the case of the present embodiment, it is assumed that the communication frequency of each master station has its own frequency and is fixed. Therefore, when switching master stations, the slave stations switch frequencies. Must be done by. Therefore, the master station switching unit 202 is provided on the slave station side. However, conversely, assuming that the communication frequency of each slave station has its own frequency and is fixed, the switching of the master station must be performed by the master station switching the frequency. Therefore, in this case, the master station switching unit 202 needs to be provided on the master station side.

Next, a specific operation of the master station switching device in the communication system according to the present invention configured as described above will be described with reference to the drawings. FIG. 4 shows the master station 10.
5 is a flowchart showing the operation of the parent station 120, and FIG. 6 is a flowchart showing the operation of the child station 200. In addition, FIG.
(B) is a diagram for explaining the operation of the flowchart,
8A, 8B, and 8C are diagrams showing the switching request data and the switching response data added to the token.

As shown in FIG. 7, the slave station 200 is replaced by the master station 1
When moving in the direction of the master station 120 while communicating with 00, the slave station 200 is moving in a direction away from the master station 100, so that the moving direction determination unit 102 of the master station 100 decreases the strength of the received radio wave. That is detected (S11: YE
S). The moving direction determination unit 102 of the parent station 100 causes the switching request data addition unit 104 due to the decrease in the intensity of the received radio wave.
The start signal is output to. On the other hand, if the decrease in the strength of the received radio wave is not detected, is the slave station 200 stopped?
Since it is moving in the direction approaching 00, the activation signal is not output from the movement direction determination unit 102 (S11: NO).

Switching request data addition unit 104 of the master station 100
Receives the activation signal from the moving direction determination unit 102, receives the token having the configuration as shown in FIG. 8A, which is circulating in the wired LAN 300, and receives the switch information of the received token. The switching request data of the master station 100 is added to the portion and output to the wired LAN 300. That is, as shown in FIG. 8B, the master station 100 (data on communication is “1”) communicating with the slave station 200 (data on communication “A”) requests switching of communication. That is, the data indicating that it is present is added to the token and output (S12).

The token to which the switching request data is added is
Since it circulates in the wired LAN 300, the communication availability determination unit 106 of the master station 120 receives this token. When the switching request data is added to the token (S21: YES), the communication availability determining unit 106 determines whether or not it is possible to communicate with the slave station 200 while switching the communication frequency. If the switching request data is not added to the received token, nothing is done and the reception of the token to which the switching request data is added is waited (S21: NO). When it is determined that the master station 120 can communicate with the slave station 200 as a result of checking whether communication is possible (S22: YES), the communication possibility determining unit 106 adds switching response data to notify that effect. An activation signal is output to the unit 108. On the other hand, when the master station 120 is not determined to be able to communicate with the slave station 200, the communication propriety determination unit 106 does not output a start signal (S22: NO). The switching response data addition unit 108 of the master station 120 communicates. In response to the activation signal from the availability determination unit 106, the wired LAN 30
8 receives a token having a configuration as shown in FIG. 8A, which circulates within 0, adds the switching response data of the master station 120 to the switch information portion of the received token, and then the wired LAN 300 Output to. That is, as shown in FIG. 8C, the master station 120 (communication data is “2”) capable of communicating with the slave station 200 (communication data is “A”) requests switching of communication. That is, the data indicating that the operation is being performed is added to the token and output (S23).

Then, the master station switching unit 202 of the slave station 200
If the communication data with the master station 100 includes the switching response data (S31: YES), the frequency of the communication is changed from the communication frequency with the master station 100 to the master station 120 based on the switching response data. Switch to the communication frequency with (S3
2). On the other hand, if the communication data with the master station 100 does not include the switching response data (S31: NO), communication with the master station 100 is continued without switching the communication frequency.

As described above, the master station switching device in the communication system according to the present invention has a possibility that the communication may be interrupted based on the movement of the mobile station before the communication between the mobile station and the master station is interrupted. Can switch to the master station from which communication can be continued. Therefore, since the slave station is always in a state where it can communicate with any of the master stations, the communication between the master station and the slave stations will not be interrupted, and information will always be transmitted accurately. Become.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a communication system to which the present invention is applied.

FIG. 2 is a block diagram showing a schematic configuration of a master station.

FIG. 3 is a block diagram showing a schematic configuration of a slave station.

FIG. 4 is a flowchart showing an operation of the master station 100.

FIG. 5 is a flowchart showing an operation of the master station 120.

6 is a flowchart showing an operation of the child station 200. FIG.

7A and 7B are diagrams for explaining the operation of the flowchart.

8A, 8B, and 8C are diagrams showing switching request data and switching response data added to a token.

[Explanation of symbols]

100, 120 ... Master station, 110, 130 ... antenna, 200, 220, 240 ... Child stations, 210, 230, 250 ... Antenna, 300 ... Wired LAN.

Claims (6)

[Claims] 1. A communication path in which a plurality of parent stations are communicatively connected to each other in a wired manner, and a slave station movable to each parent station is communicatively connected to each parent station in a wireless manner. A master station switching device in a communication system in which a token is circulated and communication is performed between the master station and the slave station, the movement of the slave station causes the slave station to communicate with a specific master station in communication. It is possible that there is a possibility of leaving the communication area with a specific master station by the communication area departure possibility determining means for determining whether there is a possibility of leaving the communication area and the communication area leaving possibility determination means. When judged, the switching request data adding means for adding the switching request data of the master station to the token circulating in the communication path, and the child when the token to which the switching request data is added is received, Is it possible to communicate with the station Communication availability determination means for determining whether or not, when it is determined that the communication with the slave station is possible,
Switching response data adding means for adding switching response data of the master station to the token circulating in the communication path, and a target of communication with the slave station according to the switching response data, the specific master station From a master station to another master station, the master station switching device in a communication system. 2. The communication area leaving possibility determining means leaves the communication area with a specific parent station with which the child station is communicating, based on a change in the intensity of a radio wave received during communication with the child station. The master station switching device in the communication system according to claim 1, wherein it is determined whether or not there is a possibility. 3. The communication availability determination means determines whether or not communication with the slave station is possible based on the strength of a radio wave received during communication with the slave station. 1. A master station switching device in the communication system according to 1. 4. The communication range leaving possibility determining means, the switching request data adding means, the communication availability determining means, and the switching response data adding means are provided in respective master stations. A master station switching device in the communication system according to Item 1. 5. The master station switching device in a communication system according to claim 1, wherein the switching means is provided in either each slave station or each master station. 6. A communication path formed by connecting a plurality of parent stations so that they can communicate with each other in a wired manner, and a slave station that is movable with respect to each of the parent stations so as to communicate with each of the parent stations wirelessly. A method of switching a master station in a communication system in which a token is circulated and communication is performed between the master station and the slave station, wherein by the movement of the slave station, the slave station is communicating with a specific master station. At the stage of determining whether there is a possibility of leaving the communication range, and when it is determined that there is a possibility of leaving the communication range with a specific master station, the token circulating in the communication path is A step of adding switching request data of the master station; a step of determining whether or not communication with the slave station is possible when the token to which the switching request data is added is received; When it is determined that communication is possible,
A step of adding switching response data of the master station to the token circulating in the communication path, and a target of communication with the slave station from the specific master station to another parent according to the switching response data. A master station switching method in a communication system, comprising: switching to a station.