Slave device, control method thereof, and communication anomaly location identification system

Abstract

To easily identify a place where communication abnormality has occurred.SOLUTION: A slave device (40) receives communication frames that are periodically transmitted from a master device (20) and circulate through slave devices (40A to 40C) to return to the master device (20). If communication times out without receiving a communication frame, the slave device 40 records reception result information representing that the communication did not receive a communication frame. The slave device (40) transmits the reception result information to the master device (20).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a slave device, a control method thereof, and a communication error Location identification Regarding the system. [Background technology]

[0002] In the field of factory automation (FA), various types of devices that share the work process are controlled. In order to link various controllers, remote I / O, and manufacturing devices used for work in a certain area such as a factory facility, industrial network systems, also called field networks, are constructed to connect these devices.

[0003] A typical industrial network system uses a master-slave network consisting of various slave devices and a master device. The slave devices are devices that control or collect data from equipment installed in a factory. The master device is a device that centrally manages these slaves, such as a programmable logic controller (PLC). EtherCAT (registered trademark) and Ethernet / IP are examples of such industrial network system types (ETHERNET: registered trademark). In such industrial network systems, communication cables are stretched between each device to create a network.

[0004] During operation of an industrial network system, some communication abnormality may occur in a slave device or a communication cable. Several techniques have been proposed to identify the location where such a communication abnormality has occurred.

[0005] Patent document 1 discloses a wireless communication device characterized by having an acquisition unit that acquires data transmitted and received in a wireless section between a relay device and a terminal device, a memory unit that stores the data, and a transmission unit that transmits the data stored in the memory unit to a server when a communication failure occurs between the relay device and the terminal device.

[0006] Patent Document 2 discloses an information processing device that collects the operating status of a communication system formed by a master device that manages communications on a network and at least one slave device that is connected to the network and capable of communicating according to instructions from the master device, in which the master device and the slave device record communication logs related to time information and communication status according to communication processing, and the information processing device includes an acquisition unit that acquires the communication log from at least one of the master device and the slave device, a log editing unit that edits the communication log acquired based on the time information, and a log extraction unit that extracts communication logs within a predetermined time from the occurrence of a communication log that has communication anomaly information indicating that an abnormality has occurred in communication as the communication status from among the communication logs edited by the log editing unit.

[0007] Patent document 3 discloses a management device that manages a network including a master device and a slave device connected to the master device, characterized in that the management device includes a network configuration diagram display unit that displays a network configuration diagram based on design information of the network designed by a user, a status information acquisition unit that acquires status information regarding the status of the slave device, and a status display unit that displays the status on the network configuration diagram in association with the slave device based on the status information. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2018-148485 A [Patent Document 2] JP 2015-1758 A [Patent Document 3] JP 2019-169089 A Summary of the Invention [Problem to be solved by the invention]

[0009] The above-mentioned conventional technology has a problem in that it is difficult to identify the location where a communication abnormality has occurred.

[0010] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to easily identify the location where a communication abnormality occurs. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems, a slave device according to one embodiment of the present invention is one of a plurality of slave devices linked to a master device and connected in series with each other, and is equipped with a receiving unit that receives a communication frame that is transmitted periodically from the master device and returns to the master device after making a round around the plurality of slave devices, a recording unit that, when communication times out without the receiving unit receiving the communication frame, records reception result information indicating that the communication frame was not received, and a transmitting unit that transmits the reception result information to the master device.

[0012] According to the above configuration, the slave device receives a communication frame periodically transmitted from the master device. The slave device executes, for example, I / O control of its own device based on the received communication frame. If the slave device times out without receiving a communication frame, it transmits reception result information indicating that the communication frame was not received to the master device. The master device can identify the location (slave device) where the communication abnormality occurred based on the received reception result information. In this case, the master device does not need to transmit a signal such as a ping to each slave device to check whether communication with each slave device is normal. Therefore, the master device can easily identify the location (slave device) where the communication abnormality occurred.

[0013] In one embodiment, the communication device further includes a monitor unit that periodically monitors a communication quality value that indicates the quality of the communication, the recording unit further records the communication quality value at the estimated reception time of the communication frame in association with the reception result information, and the transmitting unit transmits the recorded reception result information and the communication quality value to the master device.

[0014] According to the above configuration, if the master device displays the communication quality value, the administrator can refer to the displayed communication quality value and determine whether the cause of the communication abnormality is noise or not.

[0015] In one embodiment, the recording unit records the reception result information and the communication quality value in association with time information indicating the time of the estimated reception time, and the transmitting unit transmits the recorded reception result information, the communication quality value, and the time information to the master device.

[0016] According to the above configuration, the master device can accurately identify the number of the communication cycle in which the communication abnormality occurred, based on the received time information.

[0017] In one embodiment, the communication quality value is an SQI value.

[0018] According to the above-described configuration, the administrator can refer to the displayed SQI value and determine whether the cause of the communication abnormality is noise or not.

[0019] A control method for a slave device according to one embodiment of the present invention is a control method for one of multiple slave devices linked to a master device and connected in series with each other, the control method including a step of receiving a communication frame that is periodically transmitted from the master device and returns to the master device after making a round around the multiple slave devices; if communication times out without receiving the communication frame, a step of recording reception result information indicating that the communication did not receive the communication frame; and a transmission step of transmitting the reception result information to the master device.

[0020] According to the above configuration, the master device can easily identify the location (slave device) where the communication abnormality has occurred.

[0021] Communication abnormality according to one aspect of the present invention part The specific system includes any one of the slave devices and a master device. part In the identification system, the master device includes a receiving unit that receives reception result information transmitted from the slave device, and an identification unit that identifies the slave device in which a communication abnormality has occurred based on the received reception result information.

[0022] According to the above configuration, the master device can easily identify the location (slave device) where the communication abnormality has occurred. Effect of the Invention

[0023] Advantageous Effects of Invention According to one aspect of the present invention, an effect is achieved in that the location where a communication abnormality occurs can be easily identified. [Brief description of the drawings]

[0024] [Figure 1]1 is a schematic configuration diagram showing an industrial network in a production factory or the like to which a communication anomaly location locating system according to an application example of the present invention is applied. [Diagram 2] FIG. 2 is a block diagram showing a configuration of a master device. [Diagram 3] FIG. 2 illustrates a configuration of a slave device. [Figure 4] FIG. 2 is a diagram illustrating a transmission path of a communication frame in an industrial network system. [Diagram 5] 10 is a flowchart showing the flow of a series of processes executed by the master device. [Figure 6] FIG. 11 is a diagram illustrating a process flow in a slave device AC. [Figure 7] FIG. 2 is a diagram illustrating a transmission path of a communication frame for each communication cycle. [Figure 8] FIG. 13 is a diagram showing an example of a list of communication quality values ​​and reception result information of slave devices collected by the master device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] [Embodiment] Hereinafter, an embodiment according to one aspect of the present invention (hereinafter, also referred to as "the present embodiment") will be described with reference to the drawings.

[0026] §1 Examples of application First, an example of a scene in which the present invention is applied will be described. Fig. 1 is a schematic diagram showing an industrial network system 1 in a production factory or the like to which a communication anomaly location identifying system according to this application example is applied. The industrial network system 1 includes a master device 20 and a plurality of slave devices 40. Each slave device 40 is controlled by the master device 20 through the industrial network system 1, and implements various required processes in the production factory or the like. The slave device 40 is provided with a communication unit (not shown in Fig. 1) and is connected to other devices via a cable 300.

[0027] Each slave device 40 is one of the slave devices 40A to 40C that are linked to the master device 20 and connected in series with each other. The slave device 40 receives a communication frame that is periodically transmitted from the master device 20 and returns to the master device 20 after making a round of the slave devices 40A to 40C. When communication times out without receiving a communication frame, each slave device 40 records reception result information indicating that the communication frame was not received. Each slave device 40 further transmits the reception result information to the master device 20. This allows the master device 20 to easily identify the location (slave device 40) where the communication abnormality occurred in the industrial network system 1 by analyzing the received reception result information.

[0028] §2 Configuration Example (Industrial Networks) An industrial network system 1 to which a communication anomaly location identifying system according to an embodiment is applied will be described in further detail with reference to Fig. 1. The industrial network system 1 includes a master device 20 and a plurality of slave devices 40. EtherCAT (registered trademark) or Ethernet / IP is applied to the industrial network system 1 as a specific example (ETHERNET: registered trademark).

[0029] A programmable logic controller can be applied to the master device 20. The slave devices 40 managed or controlled by the master device 20 are linked to the master device 20 via a hub 30. The hub 30 is a communication device that branches a communication path from the master device 20 side (upstream side).

[0030] The master device 20, the hub 30, and the slave device 40 are connected to each other by a communication cable 300, which is generally called a LAN cable (Local Area Network Cable). As shown in the figure, the slave device 40 is connected to the cable 300 not only on the master side but also on the opposite side (downstream side), and is further linked to other slave devices (other machines).

[0031] The multiple slave devices 40 are connected in a daisy chain. In other words, the slave devices 40A to 40C are connected in series to one another. Fig. 1 shows an example in which three slave devices 40 are daisy chain connected. In the following, these slave devices 40 will be referred to as slave device 40A, slave device 40B, and slave device 40C to be distinguished from one another.

[0032] Of the three slave devices 40, slave device 40A is located at the most upstream position, slave device 40B is located in the middle, and slave device 40C is located at the most downstream position. Slave device 40A is connected to master device 20 via hub 30. Slave device 40B is connected to both slave devices 40A and 40C. Slave device 40C is connected to slave device 40B. Thus, slave device 40A is directly linked to master device 20, slave device 40B is indirectly linked to master device 20 via slave device 40A, and slave device 40C is indirectly linked to master device 20 via slave devices 40A and 40B.

[0033] The master device 20 may be linked to a server 10, which is a higher-level information processing system. For example, a communication network system such as Ethernet (registered trademark) or Ethernet / IP may be applied to the link between the master device 20 and the server 10. Similarly, the master device 20 may be linked to a display device 11. The display device 11 may further include an input means such as a touch panel, allowing instructions to be input to the master device 20.

[0034] Similarly, a control computer 50 also called a tool may be linked to the master device 20. Note that another method such as a Universal Serial Bus (USB) connection may be used to link the master device 20 and the display device 11 or to link the master device 20 and the control computer 50. Furthermore, a control computer 51 also called a tool may be connected to the hub 30 by a cable 300.

[0035] (Configuration of Master Device 20 and Slave Device 40) 2 is a block diagram showing the configuration of the master device 20. The master device 20 includes a control unit 21, a communication unit 22 (transmission unit), an identification unit 23, and a display unit 24. The control unit 21 comprehensively controls various processes in the master device 20. The communication unit 22 communicates with each slave device 40. The identification unit 23 identifies a slave device 40 in which a communication abnormality has occurred. The display unit 24 displays various information on the display device 11.

[0036] FIG. 3 is a diagram showing the configuration of the slave device 40. Of the three slave devices 40, only the slave device 40A and the slave device 40B are shown in this diagram. The slave device 40 includes a control unit 41, a communication unit 42 (receiving unit, transmitting unit), and a communication quality monitor unit 43 (monitoring unit, recording unit). The slave device 40 further includes a non-volatile memory (not shown). The control unit 41 controls the overall processing in the slave device 40. The communication unit 42 communicates with other devices connected to the slave device 40. As shown in FIG. 3, the communication unit 42 of the slave device 40A and the communication unit 42 of the slave device 40B can communicate with each other. That is, the communication unit 42 of the slave device 40A transmits a signal to the slave device 40B, and conversely, receives a signal transmitted from the communication unit 42 of the slave device 40B. Similarly, the communication unit 42 of the slave device 40B transmits a signal to the slave device 40A, and conversely, receives a signal transmitted from the communication unit 42 of the slave device 40A.

[0037] Although not shown, the communication unit 42 of the slave device 40B receives signals to the slave device 40C and receives signals transmitted from the communication unit 42 of the slave device 40C. The communication unit 42 of the slave device 40A receives signals transmitted from the communication unit 22 of the master device 20 and transmits signals to the master device 20. The communication unit 42 of the slave device 40C receives signals transmitted from the slave device 40B and transmits signals to the slave device 40B. The slave device 40C most Because slave device 40C is a downstream device, communication unit 42 of slave device 40C does not transmit signals to other devices located downstream of slave device 40C.

[0038] <Communication frame transmission path> 4 is a diagram showing a transmission path of a communication frame in the industrial network system 1. In the industrial network system 1, the slave devices 40A-40C control the input and output of information in their own devices. Hereinafter, this control will be referred to as I / O control. The I / O control in each of the slave devices 40A-40C is centrally controlled by the master device 20. That is, each of the slave devices 40A-40C executes I / O control in its own device based on a predetermined control signal transmitted from the master device 20.

[0039] The master device 20 periodically transmits a communication frame for controlling the I / O control of each of the slave devices 40A to 40C to each of the slave devices 40A to 40C. This communication frame is a type of control signal that flows through the industrial network system 1. The communication frame transmitted from the master device 20 returns to the master device 20 after going around the multiple slave devices 40. As shown in FIG. 4, the communication frame is first transmitted from the master device 20 to the slave device 40A, and then reaches the slave device 40C via the slave device 40B. The slave device 40C sends the received communication frame back to the master device 20. That is, the communication frame is transmitted from the slave device 40C to the slave device 40B, and then reaches the master device 20 via the slave devices 40B and 40A in this order. In this way, the communication frame periodically transmitted from the master device 20 travels in a single stroke within the communication path, and finally returns to the master device 20. In other words, the communication frame makes a full circuit within the communication path that starts from master device 20, loops back at slave device 40C, and returns to master device 20.

[0040] Hereinafter, a communication frame traveling from master device 20, which is the starting point of transmission, toward slave device 40C, which is the most downstream, will be referred to as an outgoing communication frame. Also, a communication frame traveling from slave device 40C toward master device 20 will be referred to as a returning communication frame. These names are used to distinguish the same communication frame according to its transmission path. In other words, an outgoing communication frame and a returning communication frame are the same communication frame.

[0041] As shown in FIG. 4, the slave devices 40A to 40C have two different communication ports 61 and 62 The communication port 61 is a communication port through which the slave devices 40A to 40C receive outgoing communication frames. The communication port 62 is a communication port through which the slave devices 40A to 40C receive return communication frames. The slave devices 40A and 40B have the communication port 61 and 625 to receive both outgoing and return communication frames. Slave device 40C receives outgoing communication frames using communication port 61. That is, slave device 40C does not use communication port 62, and therefore does not receive return communication frames. This is because no other slave device 40 is connected further downstream of slave device 40C.

[0042] The slave devices 40A to 40C periodically monitor the communication quality value of the communication port used by the slave device 40A to 40C to receive a communication frame. The communication quality value is a value indicating the quality of communication in the slave devices 40A to 40C. The communication quality value is, for example, a Signal Quality Indicator (SQI) value. The communication quality value may be an S / N ratio. As described above, the communication quality monitor unit 43 monitors the communication quality value. The communication quality monitor unit 43 records the monitored communication quality value in a non-volatile memory. The communication quality monitor unit 43 records the monitored communication quality value in the non-volatile memory in association with time information indicating the time of monitoring. In this way, the communication quality monitor unit 43 continuously records a monitor log of the communication quality value in the non-volatile memory.

[0043] The communication quality monitor unit 43 monitors the communication quality value, for example, any value from 0 to 10. The larger the communication quality value, the higher the communication quality. In this example, "0" represents the lowest communication quality, and "10" represents the highest communication quality. However, these values ​​are merely examples of values ​​that can be adopted as the communication quality value.

[0044] The communication quality monitor unit 43 monitors the communication quality value at the communication port used by the slave device 40 to receive communication frames. The communication quality monitor unit 43 of the slave device 40A monitors the communication quality value at the communication port 61 and the communication quality value at the communication port 62. The communication quality monitor unit 43 of the slave device 40B also monitors the communication quality value at the communication port 61 and the communication quality value at the communication port 62. However, the communication quality monitor unit 43 of the slave device 40C monitors the communication quality value at the communication port 61 but does not monitor the communication quality value at the communication port 62. In this way, there are a total of five locations where communication quality values ​​are monitored in the industrial network system 1.

[0045] §3 Control Example FIG. 5 is a flowchart showing a series of processes executed by the master device 20. The control unit 21 of the master device 20 controls the communication unit 22 to transmit a communication frame for I / O control in the slave devices 40A to 40C every time a certain communication cycle time has elapsed. Based on this control, the communication unit 22 waits until the communication cycle time has elapsed (S1). When the communication cycle time has elapsed, the communication unit 22 transmits the communication frame to the slave devices 40A to 40C (S2). Every time the communication unit 22 transmits a communication frame, it acquires time information indicating the time at which the communication frame was transmitted. The communication unit 22 further associates the acquired time information with the number of the communication cycle in which the communication frame was transmitted (hereinafter, communication cycle number), and stores the time information in a predetermined correspondence table. When the communication unit 42 transmits a communication frame in the nth communication cycle (n is an integer equal to or greater than 1), it associates the communication cycle number "n" with the time information indicating the time at which the communication frame was transmitted, and stores the time information in the correspondence table. For example, when the communication unit 42 transmits a communication frame in the first communication cycle, the communication unit 42 associates the communication cycle number "1" with time information indicating the time at which the communication frame was transmitted, and stores the association in the correspondence table.

[0046] After transmitting the communication frame, the communication unit 22 determines whether or not the communication frame returned from the slave device 40C has been received (S3). If the communication unit 22 determines that the communication frame has been received (YES in S3), the process returns to step S1 and waits until the next communication cycle time has elapsed. In this manner, the communication unit 22 continues to periodically transmit the communication frame to the slave devices 40A to 40C at regular communication cycle time intervals.

[0047] When communication unit 22 determines that a communication frame has not been received from slave device 40 (NO in S3), it transmits a message to slave devices 40A-40C (S4). This message is a message requesting that each slave device 40A-40C provide the master device 20 with a reception result of the communication frame and a communication quality value. In one aspect, communication unit 22 transmits the message immediately when it determines that a communication frame for I / O control has not been received. In another aspect, communication unit 22 transmits the message after a certain time has elapsed after determining that a communication frame for I / O control has not been received, in order to wait for recovery from the communication abnormality in slave devices 40A-40C.

[0048] Here, the description of the process flow of the master device 20 with reference to Fig. 5 will be temporarily suspended. The remaining processes of steps S6 to S9 will be described again after the process flow of the slave devices 40A to 40C has been described.

[0049] FIG. 6 is a diagram for explaining the flow of processing in the slave devices 40A to 40C. In the slave device 40, the control unit 41 controls the communication unit 42 to wait for a certain period of time until an outgoing communication frame and a return communication frame are received. Based on this control, the communication unit 42 starts a timer for waiting for reception of a communication frame (S11). After starting the timer, the communication unit 42 determines whether or not an outgoing communication frame has been received (S12). When the communication unit 42 determines that an outgoing communication frame has been received (YES in S12), it acquires a communication quality value at the time when the outgoing communication frame was received from a monitor log of the communication quality value (S13). The communication unit 42 further generates reception result information indicating that the outgoing communication frame has been received and time information indicating the time when the outgoing communication frame was received. The communication unit 42 records the reception result information indicating that the outgoing communication frame has been received and the acquired communication quality value in the non-volatile memory in association with the generated time information (S14). After this, the processing proceeds to step S19.

[0050] If the communication unit 42 determines that an outgoing communication frame has not been received (NO in S12), it determines whether or not the communication has timed out (S15). If the timer has expired without the communication unit 42 receiving an outgoing communication frame, it determines that the communication has timed out. On the other hand, if the timer has not expired, it determines that the communication has not timed out. If the communication unit 42 determines that the communication has not timed out (NO in S15), it returns to the processing of step S2 and again determines whether or not an outgoing communication frame has been received.

[0051] When the communication unit 42 determines that the communication has timed out (YES in S15), it obtains the communication quality value at the time of the estimated reception time of the outgoing communication frame from the monitor log of the communication quality value (S16). The "estimated reception time of the outgoing communication frame" here refers to the time when the outgoing communication frame would have been normally received if there had been no timeout. This time can be obtained from the interval between the reception times when each outgoing frame was received in the past and the time when the outgoing communication frame was previously received. For example, the communication unit 42 may obtain the "estimated reception time of the outgoing communication frame" by adding the interval between the reception times to the time when the outgoing communication frame was previously received. The communication quality monitor unit 43 monitors the communication quality value at regular time intervals regardless of whether an outgoing communication frame is received, and records the monitored communication quality value in a non-volatile memory as a communication quality value monitor log in association with time information indicating the time of monitoring. Therefore, the communication unit 42 generates time information indicating the time of the estimated reception of the outgoing communication frame, and obtains the communication quality value stored in the communication quality value monitor log in association with this time information as the communication quality value at the estimated reception of the outgoing communication frame.

[0052] The communication unit 42 further generates reception result information indicating that the outgoing communication frame was not received, and time information indicating the time when the communication timed out. The communication unit 42 records the reception result information indicating that the outgoing communication frame was received and the acquired communication quality value in the non-volatile memory in association with the generated time information (S17). The communication unit 42 then acquires each communication quality value at each time from the time when the communication timed out until a certain time before from the communication quality value monitor log (S18). The communication unit 42 records each acquired communication quality value in the non-volatile memory in association with time information indicating the time of the estimated reception of the outgoing communication frame (S19). After this, the process proceeds to step S20.

[0053] After receiving (or not receiving) an outgoing communication frame, the communication unit 42 judges whether or not a return communication frame has been received (S20). When the communication unit 42 judges that a return communication frame has been received (YES in S20), the communication unit 42 acquires a communication quality value at the time when the return communication frame was received from the non-volatile memory (S21). The communication unit 42 further generates reception result information indicating that the return communication frame has been received and time information indicating the time at which the return communication frame was received. The communication unit 42 records the reception result information indicating that the return communication frame has been received and the acquired communication quality value in association with the generated time information in the non-volatile memory (S22). The master device 20 then executes a predetermined I / O control based on the received communication frame (S23). The communication unit 42 then returns to the process of step S1 and starts the timer again. This prepares for reception of the next communication frame.

[0054] When the communication unit 42 determines that a return communication frame has not been received (NO in S20), it determines whether or not the communication has timed out (S24). When the timer has expired without the communication unit 42 receiving a return communication frame, it determines that the communication has timed out. On the other hand, when the timer has not expired, it determines that the communication has not timed out. When the communication unit 42 determines that the communication has not timed out (NO in S24), it returns to the process of step S20 and determines again whether or not a return communication frame has been received. Note that when the communication unit 42 has not received an outgoing communication frame, the timer has already expired, and the determination result in step S24 is always false (NO).

[0055] When the communication unit 42 determines that the communication has timed out (YES in S24), it acquires the communication quality value at the estimated reception time of the return communication frame from the non-volatile memory (S25). The method of calculating the estimated reception time of the return communication frame is the same as the method of calculating the estimated reception time of the outgoing communication frame described above, so detailed description will be omitted. The communication unit 42 further generates reception result information indicating that the return communication frame has not been received and time information indicating the time at which the communication timed out. The communication unit 42 records the reception result information indicating that the return communication frame has been received and the acquired communication quality value in association with the generated time information in the non-volatile memory (S26). The communication unit 42 then acquires each communication quality value at each time from the time the communication timed out until a certain time before that from the non-volatile memory (S27). The communication unit 42 records each acquired communication quality value in association with time information in the non-volatile memory (S28). The communication unit 42 then returns to the process of step S1 and restarts the timer, thereby preparing to receive the next communication frame.

[0056] Since the slave devices 40A and 40B may receive both outgoing and return communication frames, they operate according to the process flow shown in Fig. 6 as appropriate. On the other hand, the slave device 40C may not receive return communication frames, so it operates according to only a part of the process flow shown in Fig. 6 as appropriate. In other words, the slave device 40C does not execute any of the processes related to return communication frames in the process flow shown in Fig. 6. Therefore, the slave device 40C does not record the reception result information and communication quality value corresponding to the return communication frame in association with time information.

[0057] FIG. 7 is a diagram showing a transmission path of a communication frame for each communication cycle. In the example of this diagram, the master device 20 transmits a communication frame for each communication cycle time a total of six times. In the first and second communication cycles, the communication frame reaches the slave device 40C and is returned normally to the master device 20. That is, all of the slave devices 40A to 40C are able to receive and transmit the communication frame normally. In the third to fifth communication cycles, the communication frame does not reach the slave device 40C and is therefore not returned to the master device 20. That is, the slave device 40C is unable to receive the outgoing communication frame normally. Therefore, the slave devices 40A and 40B are able to receive the outgoing communication frame but are unable to receive the returning communication frame. In the sixth communication cycle, the communication frame reaches the slave device 40C and is returned normally to the master device 20. That is, the communication abnormality in the slave device 40C is restored between the fifth and sixth communication cycles.

[0058] Fig. 8 is a diagram showing an example of a list of communication quality values ​​and reception result information of the slave devices 40A to 40C collected by the master device 20. The example shown in this figure is a list generated when the slave device 40C does not receive a communication frame in the third to fifth communication cycles as shown in Fig. 7.

[0059] Here, we return to the description of the process of the master device 20 shown in FIG. 5. As described above, when the communication unit 22 of the master device 20 determines that the communication frame returned from the slave device 40 is not received, it transmits a message to the slave devices 40A to 40C (S4). Here, it is assumed that the message is transmitted when the communication frame is not received three times in succession. Therefore, in the example of FIG. 7 and FIG. 8, the communication unit 42 transmits a message when the third, fourth, and fifth communication frames are not received in succession. The transmission path of the message is the same as the outgoing point in the transmission path of the communication frame. That is, the master device 20 transmits a message to the slave device 40A. The communication unit 42 of the slave device 40A receives the message transmitted from the master device 20, and further transmits the message to the slave device 40B. The communication unit 42 of the slave device 40B receives the message transmitted from the slave device 40A and transmits it to the slave device 40C. The communication unit 42 of the slave device 40C receives the message transmitted from the slave device 40B. Slave device 40C does not transmit the message it receives to other devices, i.e., slave device 40C is the destination point for the message.

[0060] When the slave devices 40A-40C receive a message, they transmit reception result information, communication quality values, and time information of the communication frames in each communication cycle to the master device 20. Here, in response to transmitting a message when the communication unit 22 does not receive a communication frame three consecutive times, the reception result information, communication quality values, and time information of the most recent three consecutive communication frames are transmitted. The communication unit 22 of the master device 20 receives the reception result information, communication quality values, and time information of the communication frames in each communication cycle from the slave devices 40A-40C (S5).

[0061] The determination unit 23 of the master device 20 sorts each of the received reception presence / absence information based on the time information associated with each of the received reception presence / absence information (S6). For example, the sorting is performed so that reception result information with older time information is placed closer to the beginning. Similarly, the received communication quality values ​​are sorted based on the time information associated with each of the received reception presence / absence information. The determination unit 23 further refers to a correspondence table of time information and communication cycle number, and converts the time information associated with each of the reception result information into a communication cycle number. For example, the determination unit 23 searches the correspondence table for time information closest to the time information associated with a certain reception result information, and obtains the communication cycle number stored in the correspondence table in association with the found time information. Then, the determination unit 23 converts the time information associated with a certain reception result information into the obtained communication cycle number. This allows the determination unit 23 to accurately identify the communication cycle number of the communication frame corresponding to each reception result information.

[0062] As a result of executing these processes, the identifying unit 23 generates a table as shown in Fig. 8. The table in Fig. 8 stores outgoing communication frame reception result information and communication quality values ​​for the slave devices 40A to 40C in the third to fifth communication cycles. In addition, return communication frame reception result information and communication quality values ​​for the slave devices 40A and 40B in the third to fifth communication cycles are stored. Since the slave device 40C does not receive return communication frames, the table in Fig. 8 does not store return communication frame reception result information and communication quality values ​​for the slave device 40C.

[0063] 8, the identifying unit 23 checks whether a communication frame has been received in ascending order of communication cycle number, and in the order of outgoing communication frames from the slave devices 40A, 40B, and 40C, and return communication frames from the slave devices 40A, 40B, and 40C (S7). The communicating unit 42 identifies the communication port for receiving the first communication frame for which "absent" is found as the port causing the communication abnormality (S8).

[0064] When referring to the table of FIG. 8, the identification unit 23 first checks the reception result information of the outgoing communication frame of the slave device 40A in the third communication cycle, which has the smallest communication cycle number. Since this is "Yes", the identification unit 23 then checks the value of the reception result information of the outgoing communication frame of the slave device 40B for the third communication cycle. Since this is also "Yes", the identification unit 23 then checks the value of the reception result information of the outgoing communication frame of the slave device 40C in the third communication cycle. Since this is "No", the identification unit 23 stops searching the table. The identification unit 23 identifies the communication port 61 of the slave device 40C for receiving the outgoing communication frame corresponding to the reception result information initially determined to be "No" as the communication abnormality causing port. In this way, the identification unit 23 identifies the slave device 40 in which the communication abnormality has occurred in the industrial network system.

[0065] The identifying unit 23 obtains the communication quality value of the outgoing communication frame of the slave device 40C in the third communication cycle from the table in FIG. 8 as the communication quality value of the communication abnormality causing port. The display unit 24 displays the recognized communication abnormality causing port and the communication quality value of the port on the display device 11 (S9). For example, "An abnormality has occurred in the communication port 61 of the slave device 40C, communication quality value = 3" is displayed. By checking this display, the manager of the industrial network system 1 can know that some abnormality has occurred in the communication port 61 of the slave device 40C during the operation of the industrial network system 1. The manager can further consider whether the abnormality is due to noise generated in the slave device 40C, taking into account that the communication quality value of the communication port 61 of the slave device 40C is "3".

[0066] As described above, when the communication units 42 of the slave devices 40A to 40C connected in a daisy chain have timed out for reception of a periodically transmitted communication frame, the communication units 42 record reception result information indicating whether the communication frame has been received in a non-volatile memory. When the communication frame transmitted to the slave devices 40A to 40C does not return to the master device 20, the master device 20 acquires reception result information from each of the slave devices 40A to 40C and further checks the contents of each piece of reception result information. This allows the master device 20 to easily identify the communication port in the industrial network system 1 where an abnormality has occurred. In this case, the master device 20 does not need to separately transmit an inquiry communication frame to each of the slave devices 40A to 40C to check whether a communication abnormality has occurred in each communication unit 22.

[0067] <Modification> The communication unit 22 of the master device 20 can also transmit, to the slave devices 40A-40C, a communication frame to which the number of the communication cycle in which the communication frame is transmitted is previously associated. In this case, when the communication unit 42 of the slave devices 40A-40C receives a communication frame, it acquires the communication cycle number associated with the received communication frame. The communication unit 42 further associates the acquired communication cycle number with the reception result information and the communication quality value and records them in the non-volatile memory. Furthermore, when the communication unit 42 transmits a message from the master device 20, it transmits the reception result information, the communication quality value, and the communication cycle number of the communication frame in each communication cycle to the master device 20. Therefore, the identification unit 23 of the master device 20 can know the communication cycle number corresponding to the reception result information and the communication quality value by referring to each piece of received information. That is, the identification unit 23 does not need to create a correspondence table that associates the communication cycle number with the time information.

[0068] 8 itself on the display device 11. In this case, the administrator can know that an abnormality has occurred in communication port 61 of slave device 40C during the transmission periods of the third to fifth communication frames.

[0069] The display unit 24 can further display on the display device 11 each communication quality value a certain time before the communication timed out at the port causing the communication abnormality together with the communication quality value of the port causing the communication abnormality. For example, each communication quality value a certain time before the communication timed out, which is associated with the communication quality value of the outgoing communication frame of the slave device 40C in the third communication cycle, is displayed in a graph format. This allows the administrator to know the change over time in the communication quality value at the communication port 61 of the slave device 40C where the abnormality occurred.

[0070] [Example of implementation] Each functional block of the slave device 40 (particularly, the communication unit 42 and the communication quality monitor unit 43) may be realized by a logic circuit (hardware) formed on an integrated circuit (IC chip) or the like, or may be realized by software.

[0071] In the latter case, the control device includes a computer that executes instructions of a program, which is software that realizes each function. The computer includes, for example, one or more processors, and a computer-readable recording medium that stores the program. The object of the present invention is achieved by having the processor read and execute the program from the recording medium in the computer.

[0072] The processor may be, for example, a CPU (Central Processing Unit).The recording medium may be a "non-transitory tangible medium" such as a ROM (Read Only Memory), a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like.

[0073] The computer may further include a RAM (Random Access Memory) for expanding the program. The program may be supplied to the computer via any transmission medium capable of transmitting the program (such as a communication network or broadcast waves). One aspect of the present invention may also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

[0074] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the different embodiments are also included in the technical scope of the present invention. New technical features can also be formed by combining the technical means disclosed in each embodiment. [Explanation of symbols]

[0075] 1. Industrial Network Systems 10 Server 11 Display device 20 Master Device 21, 41 Control unit 22, 42 Communications Department 23 Specific section 24 Display section 30 Hub 40, 40A, 40B, 40C Slave device 43 Communication quality monitor unit 50, 51, 52 Control computer 61, 62 Communication ports 300 Cable

Claims

1. A slave device among a plurality of slave devices linked to a master device and connected in series with each other, a receiving unit for receiving a communication frame that is periodically transmitted from the master device and that returns to the master device after making a round trip through the plurality of slave devices; a recording unit which, when a communication timeout occurs without the receiving unit receiving the communication frame, records reception result information indicating that the communication frame was not received in association with any one of timeout time information indicating the time when the communication timed out, estimated reception time information indicating the time when the communication frame would have been normally received if there had been no timeout, and a communication cycle number of the communication frame that was not received; a transmission section that transmits the reception result information and any one of the timeout time information, the estimated reception time information, and the communication cycle number associated with the reception result information to the master device.

2. The communication device further includes a monitor unit that periodically monitors a communication quality value that indicates a quality of the communication, the recording unit further records the communication quality value at the estimated reception time point of the communication frame in association with the reception result information; 2. The slave device according to claim 1, wherein the transmitting unit transmits to the master device the recorded reception result information, any one of the timeout time information, the estimated reception time information, and the communication cycle number associated with the reception result information, and the communication quality value associated with the reception result information.

3. the recording unit records the reception result information and the communication quality value at the estimated reception time point in association with the estimated reception time information; The slave device according to claim 2 , wherein the transmission section transmits the recorded reception result information, the communication quality value, and the estimated reception time information to the master device.

4. 4. The slave device according to claim 2, wherein the communication quality value is an SQI value.

5. A method for controlling one of a plurality of slave devices linked to a master device and connected in series with each other, comprising the steps of: receiving a communication frame that is periodically transmitted from the master device and that returns to the master device after making a round trip through the plurality of slave devices; when communication times out without receiving the communication frame, recording reception result information representing that the communication frame was not received in association with any one of timeout time information indicating the time when the communication times out, estimated reception time information indicating the time when the communication frame would have been normally received if there had been no timeout, and a communication cycle number of the communication frame that was not received; a transmission step of transmitting the reception result information and any one of the timeout time information, the estimated reception time information, and the communication cycle number associated with the reception result information to the master device.

6. A communication anomaly location locating system including a slave device according to any one of claims 1 to 4 and a master device, The master device a receiving unit for receiving reception result information transmitted from the slave device; and an identification unit that identifies the slave device in which a communication abnormality has occurred, based on the received reception result information and any one of the timeout time information, the estimated reception time information, and the communication cycle number that are associated with the reception result information.

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