JP7634278B2 - Slave device, method and program for controlling slave device - Google Patents

Description

The present invention relates to a slave device, a control method for a slave device, and a program.

There is known technology for exchanging machine-related data between a master device and a slave device according to a master-slave communication protocol (see, for example, Patent Document 1).

The slave device acquires data related to the machine from the machine and stores the acquired data in the memory unit of the slave device. The master device transmits a request signal to the slave device, and the slave device transmits the data stored in the memory unit of the slave device to the master device as a response to the request signal from the master device. In this way, the master device retains the data from the slave device in the memory unit of the master device.

JP 2017-98762 A

However, if the master device is unable to obtain data from the slave device, the master device is unable to determine whether communication is lost between the master device and the slave device, or between the slave device and the machine.

The present invention was made in consideration of these problems, and its purpose is to provide a slave device, a control method for a slave device, and a program that can be used for troubleshooting communications.

In order to achieve the above object, a slave device according to one aspect of the present invention is a slave device that communicates with each of a master device and a machine according to a master-slave communication protocol, and includes a first communication unit that acquires data related to the machine and machine configuration information indicating the configuration of the machine from the machine, a control unit that constructs first link information indicating a link relationship with the data related to the machine based on the machine configuration information acquired by the first communication unit when the first communication unit can communicate with the machine, and constructs second link information indicating a link relationship with predetermined data when the first communication unit cannot communicate with the machine, and a second communication unit that transmits data linked to the first link information to the master device in response to a request from the master device when the first communication unit can communicate with the machine, and transmits data linked to the second link information to the master device in response to a request from the master device when the first communication unit cannot communicate with the machine.

According to this aspect, when the master device receives data linked with the first link information from the slave device, it can determine that communication is normal between the master device and the slave device, and between the slave device and the machine. Also, when the master device receives data linked with the second link information from the slave device, it can determine that communication is disabled between the slave device and the machine. Furthermore, when the master device cannot receive any data from the slave device, it can determine that communication is disabled between the master device and the slave device. This can be used for troubleshooting communications to determine whether communication is disabled between the master device and the slave device, or between the slave device and the machine.

For example, the control unit may be configured to discard the first link information if data related to the machine is acquired by the first communication unit after the first link information is constructed and the acquired data related to the machine is not linked to the first link information.

According to this aspect, for example, when the machine to which the slave device is connected is switched, the first link information can be discarded and reconstructed. As a result, the master device can receive data related to the switched machine.

For example, the control unit may be configured to discard the second link information when the first communication unit is able to communicate with the machine after constructing the second link information, and the machine configuration information is acquired by the first communication unit, and the acquired machine configuration information does not correspond to the second link information.

According to this aspect, for example, when the machine is started after the control unit constructs the second link information, the second link information can be discarded and the first link information can be constructed based on the machine configuration information acquired by the first communication unit.

In addition, a method for controlling a slave device according to one aspect of the present invention is a method for controlling a slave device that communicates with each of a master device and a machine according to a master-slave communication protocol, and includes the steps of: (a) acquiring data related to the machine from the machine; (b) acquiring machine configuration information indicating the configuration of the machine from the machine; (c) constructing first link information indicating a link relationship with the data related to the machine based on the machine configuration information acquired in (b) if the slave device can communicate with the machine, and constructing second link information indicating a link relationship with predetermined data if the slave device cannot communicate with the machine; and (d) transmitting data linked to the first link information to the master device in response to a request from the master device if the slave device can communicate with the machine, and transmitting data linked to the second link information to the master device in response to a request from the master device if the slave device cannot communicate with the machine.

According to this aspect, when the master device receives data linked with the first link information from the slave device, it can determine that communication is normal between the master device and the slave device, and between the slave device and the machine. Also, when the master device receives data linked with the second link information from the slave device, it can determine that communication is disabled between the slave device and the machine. Furthermore, when the master device cannot receive any data from the slave device, it can determine that communication is disabled between the master device and the slave device. This can be used for troubleshooting communications to determine whether communication is disabled between the master device and the slave device, or between the slave device and the machine.

In addition, a program according to one aspect of the present invention causes a computer to execute the above-mentioned slave device control method.

The slave device according to one aspect of the present invention can be used for troubleshooting communications.

1 is a block diagram showing an overview of a communication system according to a first embodiment; FIG. 2 is a block diagram showing a functional configuration of a slave device according to the first embodiment. FIG. 2 is a diagram showing an example of an address space according to the first embodiment; FIG. 2 is a diagram showing an example of a minimum address space according to the first embodiment; 5 is a flowchart showing the flow of operations of the slave device according to the first embodiment. FIG. 11 is a block diagram showing a functional configuration of a slave device according to a second embodiment. FIG. 11 is a sequence diagram showing the flow of operations of a slave device and a machine according to the second embodiment. FIG. 11 is a block diagram showing a functional configuration of a slave device according to a third embodiment. FIG. 13 is a diagram showing an example of an address space according to the third embodiment; FIG. 11 is a sequence diagram showing the flow of operations of the slave device and the machine according to the third embodiment.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection forms, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, components that are not described in an independent claim are described as optional components.

(Embodiment 1)
[1-1. Overview of communication system]
First, an overview of a communication system 2 according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram showing an overview of a communication system 2 according to a first embodiment.

As shown in FIG. 1, the communication system 2 includes a slave device 4, a machine 6, and a master device 8. In this embodiment, the communication system 2 is a communication system constructed, for example, in a factory.

In the present embodiment illustrated in FIG. 1, the communication system 2 includes one machine 6, but is not limited to this and may include multiple machines 6. In the present embodiment, the communication system 2 includes one master device 8, but is not limited to this and may include multiple master devices 8.

The slave device 4 and the machine 6 are connected via a communication line 10. The communication line 10 is a communication line capable of communication using a communication protocol such as Ethernet (registered trademark), IP (Internet Protocol), or RS-232C (serial communication). The communication realized by the communication line 10 may be wired communication or wireless communication. Specifically, the communication line 10 is constructed, for example, by a wired network composed of a wired LAN (Local Area Network), a wireless network conforming to the IEEE 802.11 standard, or a wired cable for local connection.

The slave device 4 and the master device 8 are connected via a network 12. The communication realized by the network 12 may be wired communication or wireless communication. Specifically, the network 12 is constructed, for example, as a wired network constructed using a wired LAN, or a wireless network conforming to the IEEE 802.11 standard.

The slave device 4 is a server device for communicating with each of the machine 6 and the master device 8 according to a master-slave communication protocol. More specifically, the slave device 4 is a relay device that relays various data between the machine 6 and the master device 8 according to the master-slave communication protocol. In this embodiment, the master-slave communication protocol is OPCUA (OPC Unified Architecture), and the slave device 4 is described as an OPCUA server.

The machine 6 is, for example, a CNC (Computer Numerical Control) machine tool such as a lathe for performing a predetermined machining process on a workpiece. The machine 6 has a first movement axis and a second movement axis for moving a machining tool relative to the workpiece along a first axial direction and a second axial direction, respectively.

Furthermore, the machine 6 transmits data relating to the machine 6 (hereinafter also referred to as "machine data") to the slave device 4 via the communication line 10. The data relating to the machine 6 includes, for example, a data value "ABC (Inc.)" indicating the manufacturer of the machine 6, a data value "0001" indicating the serial number of the machine 6, a data value "0100 (mm)" indicating the axial position of the first movement axis of the machine 6, and a data value "0200 (mm)" indicating the axial position of the second movement axis.

Furthermore, the machine 6 transmits machine configuration information indicating the configuration of the machine 6 to the slave device 4 via the communication line 10. The machine configuration information includes, for example, "Manufacture" indicating the manufacturer of the machine 6, "Serial Number" indicating the serial number of the machine 6, "Spindle 1" indicating the first movement axis of the machine 6, and "Spindle 2" indicating the second movement axis of the machine 6. The machine configuration information is used when the slave device 4 constructs an address space (described later).

The master device 8 is a client device for communicating with the slave device 4 according to the above-mentioned master-slave communication protocol, and is, for example, one of various terminal devices such as a personal computer operated by the user 14. The master device 8 receives various data from the slave device 4 via the network 12, and presents the received data to the user 14. Note that the master device 8 is not limited to being operated by the user 14, and may be operated, for example, by an administrator of the communication system 2. More specifically, the administrator of the communication system 2 may remotely operate the master device 8 in the factory, for example, from outside the factory, using an external network.

[1-2. Functional configuration of the slave device]
The functional configuration of the slave device 4 according to the first embodiment will be described with reference to Figures 2 to 4. Figure 2 is a block diagram showing the functional configuration of the slave device 4 according to the first embodiment. Figure 3 is a diagram showing an example of the address space 24 according to the first embodiment. Figure 4 is a diagram showing an example of the minimum address space 28 according to the first embodiment.

As shown in FIG. 2, the slave device 4 includes a first communication unit 16, a control unit 18, a memory unit 20, and a second communication unit 22.

After starting the slave device 4, the first communication unit 16 acquires machine configuration information for constructing an address space 24 (described later) from the machine 6 via the communication line 10 (see FIG. 1). The first communication unit 16 outputs the acquired machine configuration information to the control unit 18.

In addition, after the control unit 18 constructs the address space 24, the first communication unit 16 acquires machine data 26 (described later) from the machine 6 via the communication line 10. The first communication unit 16 outputs the acquired machine data 26 to the control unit 18.

When the first communication unit 16 is capable of communicating with the machine 6, the control unit 18 constructs an address space 24 as shown in FIG. 3 based on the machine configuration information acquired by the first communication unit 16. The control unit 18 stores the constructed address space 24 in the memory unit 20.

The address space 24 is information indicating a link relationship with the machine data 26, and is an example of first link information. As shown in FIG. 3, the address space 24 is a tree-like hierarchical structure having a group of data items related to the machine 6 at a lower level than "Machine Tools", for example.

The data item group has, in a lower hierarchy than the data item "Machine" that indicates machine 6, a data item "Identification" that indicates the identification information of machine 6, etc. Furthermore, in a lower hierarchy than the data item "Identification", the data item group has, in a lower hierarchy than the data item "Identification", a data item "Manufacture" that indicates the manufacturer of machine 6, a data item "Serial Number" that indicates the serial number of machine 6, a data item "Spindle 1" that indicates the axial position of the first movement axis of machine 6, and a data item "Spindle 2" that indicates the axial position of the second movement axis of machine 6, etc. Here, each data item in address space 24 is constructed based on the machine configuration information.

The control unit 18 also stores the machine data 26 acquired by the first communication unit 16 in the memory unit 20. As shown in FIG. 3, the machine data 26 includes, for example, a data value "ABC (Inc.)" indicating the manufacturer of the machine 6, a data value "0001" indicating the serial number of the machine 6, a data value "0100 (mm)" indicating the axial position of the first movement axis of the machine 6, and a data value "0200 (mm)" indicating the axial position of the second movement axis of the machine 6. Here, the data values "ABC", "0001", "0100" and "0200" of the machine data 26 are linked to the data items "Manufacture", "Serial Number", "Spindle 1" and "Spindle 2" of the address space 24, respectively.

In addition, when the first communication unit 16 cannot communicate with the machine 6, the control unit 18 cannot obtain machine configuration information through the first communication unit 16 and therefore cannot construct the address space 24 described above. Therefore, when the first communication unit 16 cannot communicate with the machine 6, the control unit 18 constructs a minimum address space 28 as shown in FIG. 4. The control unit 18 stores the constructed minimum address space 28 in the memory unit 20.

The minimum address space 28 is information indicating a link relationship with the fixed data 30, which is predetermined data, and is an example of second link information. As shown in FIG. 4, the minimum address space 28 has, as a data item group, a data item "Manufacture" indicating the manufacturer of the machine 6 and a data item "Serial Number" indicating the serial number of the machine 6, in a lower hierarchy than the data item "Identification". Here, each data item "Manufacture" and "Serial Number" of the minimum address space 28 is linked to each data value "ABC" and "0001" of the fixed data 30, respectively. Note that each data item "Manufacture" and "Serial Number" of the minimum address space 28 is minimum configuration information that can determine a fixed data value to be linked even if the first communication unit 16 does not communicate with the machine 6.

The fixed data 30 also includes data values that can be determined without the first communication unit 16 communicating with the machine 6, such as the data value "ABC (Inc.)" indicating the manufacturer of the machine 6 and the data value "0001" indicating the serial number of the machine 6. Before the first communication between the slave device 4 and the machine 6, the control unit 18 registers, in advance in the storage unit 20, for example, the data value "ABC (Inc.)" indicating the manufacturer of the machine 6 and the data value "0001" indicating the serial number of the machine 6 as fixed data 30. When the control unit 18 constructs the minimum address space 28, it reads out the fixed data 30 from the storage unit 20 and links the data values "ABC" and "0001" of the read fixed data 30 to the data items "Manufacturer" and "Serial Number" of the minimum address space 28, respectively.

Returning to FIG. 2, the second communication unit 22 transmits and receives various data to and from the master device 8 via the network 12 (see FIG. 1). Specifically, when the first communication unit 16 can communicate with the machine 6, the second communication unit 22 reads the address space 24 and the machine data 26 from the storage unit 20 in response to a request from the master device 8, and transmits each data value of the machine data 26 linked to each data item of the address space 24 to the master device 8. When the first communication unit 16 cannot communicate with the machine 6, the second communication unit 22 reads the minimum address space 28 and the fixed data 30 from the storage unit 20 in response to a request from the master device 8, and transmits each data value of the fixed data 30 linked to each data item of the minimum address space 28 to the master device 8.

[1-3. Operation of Slave Device]
The operation of the slave device 4 according to the first embodiment will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the flow of the operation of the slave device 4 according to the first embodiment.

As shown in FIG. 5, first, the slave device 4 is started (S101). Next, the control unit 18 determines whether communication between the first communication unit 16 and the machine 6 is possible (S102).

When the first communication unit 16 can communicate with the machine 6 (YES in S102), the first communication unit 16 acquires machine configuration information from the machine 6 via the communication line 10 (S103). The first communication unit 16 outputs the acquired machine configuration information to the control unit 18.

The control unit 18 then constructs an address space 24 based on the machine configuration information acquired by the first communication unit 16 (S104). The control unit 18 stores the constructed address space 24 in the memory unit 20. The second communication unit 22 then waits for connection with the master device 8 (S105). Thereafter, the first communication unit 16 acquires machine data 26 from the machine 6 via the communication line 10, and the control unit 18 stores the machine data 26 acquired by the first communication unit 16 in the memory unit 20. At this time, the control unit 18 links each data value of the machine data 26 to each data item in the address space 24.

In this case, when a connection between the second communication unit 22 and the master device 8 is established, the second communication unit 22 reads the address space 24 and the machine data 26 from the memory unit 20 in response to a request from the master device 8, and transmits each data value of the machine data 26 that is linked to each data item of the address space 24 to the master device 8.

Returning to step S102, if the first communication unit 16 cannot communicate with the machine 6 (NO in S102), the first communication unit 16 cannot obtain machine configuration information from the machine 6 via the communication line 10. In this case, the control unit 18 constructs a minimum address space 28 (S106). The control unit 18 stores the constructed minimum address space 28 in the memory unit 20.

Then, the second communication unit 22 waits for a connection with the master device 8 (S105). In this case, when a connection between the second communication unit 22 and the master device 8 is established, the second communication unit 22 reads the minimum address space 28 and the fixed data 30 from the storage unit 20 in response to a request from the master device 8, and transmits each data value of the fixed data 30 that is linked to each data item in the minimum address space 28 to the master device 8.

[1-4. Effects]
As described above, when the first communication unit 16 is able to communicate with the machine 6, the control unit 18 constructs an address space 24 based on the machine configuration information acquired by the first communication unit 16. Then, in response to a request from the master device 8, the second communication unit 22 transmits to the master device 8 each data value of the machine data 26 linked with each data item of the address space 24. As a result, the master device 8 can normally receive each data value of the machine data 26, and can therefore determine that communication is normally performed between the master device 8 and the slave device 4, and between the slave device 4 and the machine 6.

On the other hand, if the first communication unit 16 is unable to communicate with the machine 6, the control unit 18 constructs a minimum address space 28. Then, in response to a request from the master device 8, the second communication unit 22 transmits to the master device 8 each data value of the fixed data 30 that is linked to each data item in the minimum address space 28. As a result, the master device 8 can determine that communication between the slave device 4 and the machine 6 is unable to be performed by receiving a smaller number of data values of the fixed data 30 than the data values of the machine data 26.

Furthermore, if the master device 8 requests the slave device 4 to transmit a data value but does not receive any data value from the slave device 4, it can determine that communication between the master device 8 and the slave device 4 is not possible.

As described above, this embodiment can be used to troubleshoot communication problems to determine whether communication is lost between the master device 8 and the slave device 4, or between the slave device 4 and the machine 6.

(Embodiment 2)
[2-1. Functional configuration of the slave device]
The functional configuration of the slave device 4A according to the second embodiment will be described with reference to Fig. 6. Fig. 6 is a block diagram showing the functional configuration of the slave device 4A according to the second embodiment. Note that in each of the following embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 6, in the slave device 4A according to the second embodiment, the processing of the control unit 18A is different from the processing of the control unit 18 of the slave device 4 according to the first embodiment. Specifically, when the control unit 18A is initially unable to communicate with the machine 6 and establishes a minimum address space 28 (see FIG. 4), and then becomes able to communicate with the machine 6, and machine configuration information is acquired by the first communication unit 16, if the machine configuration information does not correspond to the minimum address space 28, the control unit 18A discards the minimum address space 28 and reconstructs the address space 24 (see FIG. 3). The discarding of the minimum address space 28 is performed, for example, by restarting a service (e.g., access to data, monitoring of alarms and events, etc.) that complies with the OPCUA standard in the slave device 4A.

[2-2. Operations of Slave Devices and Machines]
Each operation of the slave device 4A and the machine 6 according to the second embodiment will be described with reference to Fig. 7. Fig. 7 is a sequence diagram showing the flow of each operation of the slave device 4A and the machine 6 according to the second embodiment.

The following describes a case where the machine 6 is not started when the slave device 4A is started, and the machine 6 is started when a predetermined time has elapsed since the slave device 4A was started.

As shown in FIG. 7, first, the first communication unit 16 of the slave device 4A transmits a request signal to the inactive machine 6 to request the transmission of machine configuration information (S201). At this time, the machine 6 is not active and the first communication unit 16 is unable to communicate with the machine 6, so no response is received from the machine 6. When the first communication unit 16 is unable to communicate with the machine 6 in this manner, the control unit 18A constructs a minimum address space 28 (S202). Note that in the slave device 4A according to the second embodiment, even if the first communication unit 16 does not receive any response from the machine 6, the active state of the slave device 4A is maintained.

Next, the first communication unit 16 of the slave device 4A repeatedly transmits a request signal to the machine 6 to request the machine configuration information to be sent until a response is received from the machine 6 (S203, S204).

After that, the machine 6 is started (S205), and the first communication unit 16 of the slave device 4A becomes able to communicate with the started machine 6. The first communication unit 16 transmits a request signal to the machine 6 to request the machine 6 to transmit machine configuration information (S206), and obtains the machine configuration information responded by the machine 6 (S207).

The control unit 18A of the slave device 4A compares the machine configuration information acquired by the first communication unit 16 with the minimum address space 28. For example, in each data item of the minimum address space 28 shown in FIG. 4, "Spindle 1" indicating the first movement axis of the machine 6 and "Spindle 2" indicating the second movement axis of the machine 6, which are included in the acquired machine configuration information, are not present. In this case, the control unit 18A detects that the machine configuration information acquired by the first communication unit 16 does not correspond to the minimum address space 28 (S208). Then, the control unit 18A discards the minimum address space 28 by restarting the slave device 4A (restarting the service) (S209).

Next, the first communication unit 16 of the slave device 4A again transmits a request signal to the machine 6 to request the machine configuration information to be sent (S210), and acquires the machine configuration information responded to by the machine 6 (S211). The control unit 18A constructs an address space 24 based on the machine configuration information acquired by the first communication unit 16 (S212).

Next, the first communication unit 16 of the slave device 4A transmits a request signal to the machine 6 to request transmission of the machine data 26 (see FIG. 3) (S213), and acquires the machine data 26 responded to by the machine 6 (S214). The control unit 18A stores the machine data 26 acquired by the first communication unit 16 in the memory unit 20. At this time, the control unit 18A links each data value of the machine data 26 to each data item in the address space 24.

[2-3. Effects]
As described above, when the machine 6 starts up after the control unit 18A constructs the minimum address space 28, the control unit 18A detects that the machine configuration information acquired by the first communication unit 16 does not correspond to the minimum address space 28. At this time, the control unit 18A discards the minimum address space 28 by automatically restarting the slave device 4A (restarting the service). This allows the control unit 18A to construct the address space 24 based on the machine configuration information acquired by the first communication unit 16 thereafter.

In the second embodiment, an example is described in which the slave device 4A cannot communicate with the machine 6 because the machine 6 is not started when the slave device 4A is started, but this is not limited to the above example, and the present invention can also be applied to a case in which the communication line 10 (see FIG. 1) is restored from a state in which communication is temporarily disabled (for example, a state in which the wired cable is disconnected from the connection connector, etc.).

(Embodiment 3)
[3-1. Functional configuration of the slave device]
The functional configuration of the slave device 4B according to the third embodiment will be described with reference to Fig. 8 and Fig. 9. Fig. 8 is a block diagram showing the functional configuration of the slave device 4B according to the third embodiment. Fig. 9 is a diagram showing an example of the address space 32 according to the third embodiment.

As shown in FIG. 8, in the slave device 4B according to the third embodiment, the first communication unit 16 can communicate with either the machine 6a or the machine 6b by switching the connection destination via the communication line 10 (see FIG. 1) between the machine 6a and the machine 6b. The configuration of the machine 6a is the same as the configuration of the machine 6 described in the first embodiment above, and therefore the description thereof is omitted.

The machine 6b has a first movement axis, a second movement axis, and a third movement axis, etc., for moving the machining tool relative to the workpiece along the first axial direction, the second axial direction, and the third axial direction, respectively.

Furthermore, machine 6b transmits machine data 34 to slave device 4B via communication line 10. As shown in FIG. 9, machine data 34 transmitted from machine 6b includes, for example, a data value "ABC (Inc.)" indicating the manufacturer of machine 6b, a data value "0002" indicating the serial number of machine 6b, a data value "0150 (mm)" indicating the axial position of the first movement axis of machine 6b, a data value "0250 (mm)" indicating the axial position of the second movement axis, and a data value "0100 (mm)" indicating the axial position of the third movement axis.

Furthermore, machine 6b transmits machine configuration information indicating the configuration of machine 6b to slave device 4B via communication line 10. The machine configuration information includes, for example, "Manufacture" indicating the manufacturer of machine 6b, "Serial Number" indicating the serial number of machine 6b, "Spindle 1" indicating the first movement axis of machine 6b, "Spindle 2" indicating the second movement axis of machine 6b, and "Spindle 3" indicating the third movement axis of machine 6b. The machine configuration information is used when slave device 4B constructs address space 32 (described later).

In addition, in the slave device 4B according to the third embodiment, the processing of the control unit 18B differs from the processing of the control unit 18 and the control unit 18A according to the first and second embodiments. Specifically, after constructing an address space 24 (see FIG. 3) based on the machine configuration information from the machine 6a acquired by the first communication unit 16, the control unit 18B discards the address space 24 when the connection destination of the communication line 10 is switched from the machine 6a to the machine 6b, the machine data 34 from the machine 6b is acquired by the first communication unit 16, and the acquired machine data 34 and the address space 24 are not linked. The discarding of the address space 24 can be performed, for example, by restarting the slave device 4B (restarting the service).

When the first communication unit 16 is capable of communicating with the machine 6b, the control unit 18B constructs an address space 32 as shown in FIG. 9 based on the machine configuration information from the machine 6b acquired by the first communication unit 16. The address space 32 is information indicating a link relationship with the machine data 34, and is an example of first link information. As shown in FIG. 9, the address space 32 is, for example, a tree-like hierarchical structure having a group of data items related to the machine 6b at a lower level than the "Machine Tools" level.

The data item group has, in a lower hierarchy than the data item "Machine" indicating machine 6b, a data item "Identification" indicating the identification information of machine 6b. Furthermore, in a lower hierarchy than the data item "Identification", the data item group has, in a lower hierarchy than the data item "Identification", a data item "Manufacture" indicating the manufacturer of machine 6b, a data item "Serial Number" indicating the serial number of machine 6b, a data item "Spindle 1" indicating the axial position of the first movement axis of machine 6b, a data item "Spindle 2" indicating the axial position of the second movement axis of machine 6b, and a data item "Spindle 3" indicating the axial position of the third movement axis of machine 6b. Here, each data item in address space 32 is constructed based on the machine configuration information.

Furthermore, each data value "ABC", "0002", "0150", "0250" and "0100" in the machine data 34 is linked to each data item "Manufacture", "Serial Number", "Spindle 1", "Spindle 2" and "Spindle 3" in the address space 32, respectively.

[3-2. Operations of Slave Devices and Machines]
The operations of the slave device 4B, the machine 6a, and the machine 6b according to the third embodiment will be described with reference to Fig. 10. Fig. 10 is a sequence diagram showing the flow of the operations of the slave device 4B, the machine 6a, and the machine 6b according to the third embodiment.

The following describes a case where the first communication unit 16 and machine 6a are connected via the communication line 10 when the slave device 4B is started, and then the connection destination of the first communication unit 16 is switched from machine 6a to machine 6b. In addition, in the third embodiment, it is assumed that the master device 8 (operated by the user 14) requests the machine 6a and machine 6b to transmit machine data 26 (see FIG. 3) via the slave device 4B.

As shown in FIG. 10, first, the first communication unit 16 of the slave device 4B transmits a request signal to the machine 6a to request the machine 6a to transmit machine configuration information (S301), and acquires the machine configuration information in response from the machine 6a (S302). The control unit 18B constructs the address space 24 (see FIG. 3) based on the machine configuration information acquired by the first communication unit 16 (S303).

Then, the first communication unit 16 of the slave device 4B transmits a request signal to the machine 6a to request the transmission of the machine data 26 (see FIG. 3) (S304), and acquires the machine data 26 responded to by the machine 6a (S305). The control unit 18B stores the machine data 26 acquired by the first communication unit 16 in the memory unit 20. At this time, the control unit 18B links each data value of the machine data 26 to each data item in the address space 24.

Then, the connection between the first communication unit 16 and the machine 6a is cut off (S306), and the connection between the first communication unit 16 and the machine 6b is started (S307). That is, the connection destination of the first communication unit 16 is switched from the machine 6a to the machine 6b. Here, this switching is performed autonomously by the control unit 18B based on a request to send machine data 26 (see FIG. 3) from the slave device 4B to the machine 6b after the connection between the first communication unit 16 and the machine 6a is cut off (S306).

Next, the first communication unit 16 of the slave device 4B transmits a request signal to the machine 6b to request the transmission of the machine data 34 (S308), and acquires the machine data 34 responded from the machine 6b (S309). The control unit 18B stores the machine data 34 acquired by the first communication unit 16 in the memory unit 20.

At this time, the control unit 18B attempts to link each data value of the machine data 34 with each data item of the address space 24. However, the data value "0100 (mm)" indicating the axis position of the third movement axis of the machine 6b, which is included in the machine data 34, does not link with either of the data items "Spindle 1" or "Spindle 2" in the address space 24. Therefore, the control unit 18B detects that the machine data 34 and the address space 24 are not linked (S310). The control unit 18B then automatically restarts the slave device 4B (restarts the service) (S311) to discard the address space 24.

Next, the first communication unit 16 of the slave device 4B transmits a request signal to the machine 6b to request the machine 6b to transmit its machine configuration information (S312), and acquires the machine configuration information responded by the machine 6b (S313). The control unit 18B constructs an address space 32 based on the machine configuration information acquired by the first communication unit 16 (S314).

Then, the first communication unit 16 of the slave device 4B transmits a request signal to the machine 6b to request the transmission of the machine data 34 (S315), and acquires the machine data 34 responded to from the machine 6b (S316). The control unit 18B stores the machine data 34 acquired by the first communication unit 16 in the memory unit 20. At this time, the control unit 18B links each data value of the machine data 34 to each data item in the address space 32.

[3-3. Effects]
As described above, after constructing the address space 24 based on the machine configuration information from the machine 6a acquired by the first communication unit 16, if the connection destination of the first communication unit 16 is switched from the machine 6a to the machine 6b and the first communication unit 16 acquires machine data 34 from the machine 6b and the acquired machine data 34 is not linked to the address space 24, the control unit 18B discards the address space 24 by automatically restarting the slave device 4B (restarting the service).

The control unit 18B can then construct the address space 32 based on the machine configuration information from the machine 6b acquired by the first communication unit 16. By linking each data value of the machine data 34 with each data item of the address space 32, the master device 8 can receive the machine data 34 relating to the switched machine 6b.

(Other Modifications, etc.)
Although the slave device of the present invention has been described above based on the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments. The present invention also includes forms obtained by applying modifications to the above-mentioned embodiments that would come to mind by a person skilled in the art, and other forms realized by arbitrarily combining the components in the above-mentioned embodiments.

In the above embodiments, the master-slave communication protocol is OPCUA, but it is not limited to this and may be any other master-slave communication protocol such as MTConnect. When the master-slave communication protocol is MTConnect, the first link information is device information. In this case, the second link information has "n.avail-" indicating the data reception status, and the fixed data linked to the "n.avail-" of the second link information is "UNAVAILABLE" indicating that communication with the machine 6 (6a, 6b) is not possible.

In each of the above embodiments, the machine 6 (6a, 6b) is a machine tool, but is not limited to this and may be, for example, an industrial robot, a measuring machine, or any other type of industrial machine.

In each of the above embodiments, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

The present invention can be applied to, for example, a slave device that communicates with a machine and a master device according to a master-slave communication protocol.

Reference Signs List 2 Communication system 4, 4A, 4B Slave device 6, 6a, 6b Machine 8 Master device 10 Communication line 12 Network 14 User 16 First communication unit 18, 18A, 18B Control unit 20 Memory unit 22 Second communication unit 24, 32 Address space 26, 34 Machine data 28 Minimum address space 30 Fixed data

Claims (5)

A slave device that communicates with each of a master device and a machine according to a master-slave communication protocol,
a first communication unit that acquires data related to the machine and machine configuration information indicating a configuration of the machine from the machine;
a control unit that, when the first communication unit is capable of communicating with the machine, constructs first link information indicating a link relationship with data related to the machine based on the machine configuration information acquired by the first communication unit, and, when the first communication unit is unable to communicate with the machine, constructs second link information indicating a link relationship with predetermined data;
a second communication unit that, when the first communication unit is capable of communicating with the machine, transmits data linked to the first link information to the master device in response to a request from the master device, and, when the first communication unit is unable to communicate with the machine, transmits data linked to the second link information to the master device in response to a request from the master device. 2. The slave device according to claim 1, wherein the control unit, when data related to the machine is acquired by the first communication unit after the first link information is constructed and the acquired data related to the machine is not linked to the first link information, discards the first link information. 2. The slave device according to claim 1, wherein the control unit, when the first communication unit becomes able to communicate with the machine after constructing the second link information and the machine configuration information is acquired by the first communication unit, discards the second link information if the acquired machine configuration information does not correspond to the second link information. A method for controlling a slave device that communicates with a master device and a machine according to a master-slave communication protocol, comprising the steps of:
(a) obtaining data relating to the machine from the machine;
(b) acquiring machine configuration information from the machine, the machine configuration information indicating a configuration of the machine;
(c) constructing first link information indicating a link relationship with data related to the machine based on the machine configuration information acquired in (b) when the slave device is capable of communicating with the machine, and constructing second link information indicating a link relationship with predetermined data when the slave device is unable to communicate with the machine;
(d) when the slave device is capable of communicating with the machine, transmitting data linked to the first link information to the master device in response to a request from the master device, and when the slave device is unable to communicate with the machine, transmitting data linked to the second link information to the master device in response to a request from the master device. A program that causes a computer to execute the slave device control method according to claim 4.