WO2022172463A1

WO2022172463A1 - Slave device, method for controlling same, and communication abnormality location detection system

Info

Publication number: WO2022172463A1
Application number: PCT/JP2021/007843
Authority: WO
Inventors: 孝史武田; 竜一手嶌; 一樹久米
Original assignee: オムロン株式会社
Priority date: 2021-02-10
Filing date: 2021-03-02
Publication date: 2022-08-18
Also published as: JP2022122692A

Abstract

The present invention makes it possible to easily identify the location of occurrence of a communication abnormality. A slave device (40) receives a communication frame that is regularly transmitted from a master device (20), passes through slave devices (40A to 40C), and returns to the master device (20). The slave device (40) records reception result information indicating that communication did not receive a communication frame when communication times out without receiving the communication frame. The slave device (40) transmits the reception result information to the master device (20).

Description

SLAVE DEVICE, CONTROL METHOD THEREOF, AND COMMUNICATION ABNORMAL POINT DETECTION SYSTEM

The present invention relates to a slave device, its control method, and a communication error detection system.

In the field of Factory Automation (FA), various types of devices are controlled that share work processes. In order to operate various controllers, remote I/O, and manufacturing equipment used for work in a certain area such as a factory facility in cooperation with each other, an industrial network system, also called a field network, is constructed to connect these equipment. ing.

A typical industrial network system uses a master-slave network consisting of various slave devices and master devices. A slave device is a device that controls equipment installed in a factory or collects data. The master device is a device called (PLC: Programmable Logic Controller) that centrally manages these slaves. EtherCAT (registered trademark) or Ethernet/IP is an example of such an industrial network system scheme (ETHERNET: registered trademark). In such an industrial network system, communication cables are stretched between devices to construct a network.

　While the industrial network system is in operation, some kind of communication abnormality may occur in the slave device or communication cable. Several techniques have been proposed for identifying the location where such communication anomalies have occurred.

Patent Document 1 discloses an acquisition unit that acquires data transmitted and received in a wireless section between a relay device and a terminal device, a storage unit that stores the data, and communication between the relay device and the terminal device. A wireless communication device is disclosed, comprising: a transmission unit that transmits the data stored in the storage unit to a server when a failure occurs.

In Patent Document 2, operation states of a communication system formed by a master device that manages communication on a network and at least one slave device that is connected to the network and can communicate according to instructions from the master device are collected. An information processing device, wherein the master device and the slave device record a communication log regarding time information and a communication state according to communication processing, and the information processing device receives the communication from at least one of the master device and the slave device. An acquisition unit that acquires a log, a log editing unit that edits the communication log acquired based on the time information, and a communication state in the communication log edited by the log editing unit that indicates that an abnormality has occurred in communication. An information processing apparatus is disclosed that includes a log extraction unit that extracts a communication log within a predetermined period of time from the occurrence of a communication log having communication abnormality information.

Patent Document 3 discloses a management device that manages a network including a master device and a slave device connected to the master device, in which network a network configuration diagram display unit that displays a configuration diagram; a state information acquisition unit that acquires state information regarding the state of the slave device; and based on the state information, the state corresponds to the slave device on the network configuration diagram. and a status display section attached to display.

Japanese Patent Publication "JP 2018-148485" Japanese patent publication "JP 2015-1758" Japanese Patent Publication "JP 2019-169089"

With the conventional technology described above, there is the problem that it is difficult to identify the location where a communication error has occurred.

The present invention has been made to solve the above problems, and its purpose is to easily identify the location of a communication abnormality.

In order to solve the above problems, a slave device according to an aspect of the present invention is one of a plurality of slave devices linked to a master device and serially connected to each other, comprising: a receiving unit that receives a communication frame that is periodically transmitted from a master device and returns to the master device after circulating through the plurality of slave devices; and a case where communication times out without the receiving unit receiving the communication frame. a recording unit for recording reception result information indicating that the communication frame has not been received; and a transmission unit for transmitting the reception result information to the master device.

　According to one aspect of the present invention, it is possible to easily identify the location of the communication abnormality.

1 is a schematic configuration diagram showing an industrial network in a production factory or the like, to which a communication abnormality location identification system according to this application example is applied; FIG. 3 is a block diagram showing the configuration of a master device; FIG. It is a figure which shows the structure of a slave device. FIG. 2 is a diagram showing transmission paths of communication frames in an industrial network system; 4 is a flow chart showing the flow of a series of processes executed by the master device; 4 is a diagram for explaining the flow of processing in a slave device AC; FIG. FIG. 4 is a diagram showing transmission paths of communication frames for each communication cycle; FIG. 4 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;

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

§1 Application Example First, an example of a scene to which the present invention is applied will be described. FIG. 1 is a schematic configuration diagram showing an industrial network system 1 in a production factory or the like, to which a communication abnormality point identification system according to this application example is applied. The industrial network system 1 includes a master device 20 and multiple slave devices 40 . Each slave device 40 is controlled by the master device 20 through the industrial network system 1 and constructs various required processes in a production factory or the like. The slave device 40 is provided with a communication unit (not shown in FIG. 1) and connected to another device via a cable 300 .

Each slave device 40 is one of the slave devices 40A-40C linked to the master device 20 and serially connected to each other. The slave device 40 receives communication frames that are periodically transmitted from the master device 20 and return to the master device 20 through the slave devices 40A to 40C. Each slave device 40 records reception result information indicating that the communication frame was not received when the communication timed out without receiving the communication frame. Each slave device 40 further transmits reception result information to the master device 20 . As a result, the master device 20 can easily identify the location (slave device 40 ) where the communication error occurred in the industrial network system 1 by analyzing the received reception result information.

§2 Configuration example (industrial network)
An industrial network system 1 to which a communication abnormality location identification system according to an embodiment is applied will be described in more detail using FIG. The industrial network system 1 includes a master device 20 and multiple slave devices 40 . As a specific example, EtherCAT (registered trademark) or Ethernet/IP is applied to the industrial network system 1 (ETHERNET: registered trademark, Ethernet: registered trademark).

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

The master device 20, hub 30, and slave device 40 are connected by a communication cable 300 generally called a LAN cable (Local Area Network Cable). As illustrated, the cable 300 is connected not only on the master side but also on the opposite side (downstream side) of the slave device 40 to link to other slave devices (other devices).

A plurality of slave devices 40 are connected by a daisy chain method. In other words, the slave devices 40A-40C are connected in series with each other. FIG. 1 shows an example in which three slave devices 40 are daisy-chained. Hereinafter, these slave devices 40 are described as slave device 40A, slave device 40B, and slave device 40C to distinguish them from each other.

Of the three slave devices 40, the slave device 40A is positioned furthest upstream, the slave device 40B is positioned in the middle, and the slave device 40C is positioned furthest downstream. Slave device 40A is connected to master device 20 via hub 30 . Slave device 40B is connected to both slave devices 40A and 40 . 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 linked to master device via slave devices 40A and 40B. 20 indirectly linked.

The master device 20 may be linked to the server 10, which is an upper information processing system. For the link between the master device 20 and the server 10, a communication network method such as Ethernet (registered trademark) or Ethernet/IP can be applied. The display device 11 may similarly be linked to the master device 20 . The display device 11 may further include input means such as a touch panel, and may be capable of inputting instructions to the master device 20 .

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

(Configuration of master device 20 and slave device 40)
FIG. 2 is a block diagram showing the configuration of the master device 20. As shown in FIG. The master device 20 includes a control section 21 , a communication section 22 (transmitting section), a specifying section 23 and a display section 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 the slave device 40 in which the communication abnormality has occurred. The display unit 24 displays various information on the display device 11 .

FIG. 3 is a diagram showing the configuration of the slave device 40. As shown in FIG. Of the three slave devices 40, only slave device 40A and slave device 40B are shown in this figure. The slave device 40 includes a control section 41, a communication section 42 (receiving section, transmitting section), and a communication quality monitoring section 43 (monitoring section, recording section). Slave device 40 further comprises a non-volatile memory (not shown). The control unit 41 comprehensively controls the 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 signals to the slave device 40B, and conversely receives signals transmitted from the communication unit 42 of the slave device 40B. Similarly, the communication unit 42 of the slave device 40B transmits signals to the slave device 40A and conversely receives signals transmitted from the slave device 40A.

Although not shown, the communication unit 42 of the slave device 40B receives signals from the slave device 40C and receives signals transmitted from the communication unit 42 of the slave device 40C. Also, 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 . Also, 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. Since the slave device 40C is a re-downstream device, the communication unit 42 of the slave device 40C does not transmit signals to other devices located downstream of the slave device 40C.

<Communication frame transmission route>
FIG. 4 is a diagram showing transmission paths of communication frames in the industrial network system 1. As shown in FIG. In the industrial network system 1, the slave devices 40A-40C control the input and output of information in their own devices. This control is hereinafter referred to as I/O control. I/O control in each of the slave devices 40A-40C is centrally controlled by the master device 20. FIG. That is, each slave device 40A-40C executes I/O control in its own device based on a predetermined control signal transmitted from the master device 20. FIG.

The master device 20 periodically transmits communication frames for controlling the I/O control of each slave device 40A-40C to each slave device 40A-40C. This communication frame is a kind of control signal flowing through the industrial network system 1 . A communication frame transmitted from the master device 20 circulates through a plurality of slave devices 40 and returns to the master device 20 . A 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, as shown in FIG. Slave device 40C sends back the received communication frame to master device 20 . That is, a communication frame is transmitted from slave device 40C to slave device 40B and then reaches master device 20 via

slave devices

40B and 40A in sequence. In this way, the communication frames periodically transmitted from the master device 20 move in a single stroke within the communication path, and finally return to the master device 20 . In other words, the communication frame goes around the communication path starting from the master device 20 and returning to the master device 20 by looping back at the slave device 40C.

Hereinafter, a communication frame when moving from the master device 20, which is the transmission starting point, toward the most downstream slave device 40C will be referred to as an outgoing communication frame. A communication frame when moving from the slave device 40C to the master device 20 is called a return communication frame. These names are expressions for distinguishing the same communication frame according to its transmission path. That is, the forward communication frame and the return communication frame are the same communication frame.

As shown in FIG. 4, the slave devices 40A-40C have two different communication ports 61 and 52. The communication port 61 is a communication port for the slave devices 40A to 40C to receive outgoing communication frames. A communication port 62 is a communication port for the slave devices 40A to 40C to receive return communication frames.

Slave devices

40A and 40B use both communication ports 61 and 52 to receive both outgoing and return communication frames. The slave device 40C uses the communication port 61 to receive outgoing communication frames. 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 downstream of the slave device 40C.

The slave devices 40A to 40C periodically monitor the communication quality value at the communication port used by the device itself to receive communication frames. The communication quality value is a value that indicates the quality of communication in the slave devices 40A-40C. The communication quality value is, for example, an SQI value (Signal Quality Indicator). The communication quality value may be the S/N ratio. As described above, the communication quality monitor unit 43 monitors communication quality values. The communication quality monitor unit 43 records the monitored communication quality value in the nonvolatile 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 manner, the communication quality monitor unit 43 continuously records the monitor log of the communication quality value in the nonvolatile memory.

The communication quality monitor unit 43 monitors any value from 0 to 10, for example, as a communication quality value. 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 used as communication quality values.

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. FIG. In this way, there are a total of five locations where communication quality values are monitored in the industrial network system 1 .

§3 Control Example FIG. 5 is a flow chart 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 so as to transmit a communication frame for I/O control in the slave devices 40A to 40C each time a certain communication cycle time elapses. Based on this control, the communication unit 22 waits until the communication cycle time elapses (S1). When the communication cycle time elapses, the communication unit 22 transmits communication frames to the slave devices 40A to 40C (S2). Each time the communication unit 22 transmits a communication frame, the communication unit 22 acquires time information representing the time when 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 referred to as the communication cycle number), and stores them in a predetermined correspondence table. When the communication frame is transmitted in the n-th communication cycle (n is an integer equal to or greater than 1), the communication unit 42 associates the communication cycle number “n” with time information representing the time when the communication frame was transmitted, and creates a correspondence table. store in For example, when the communication frame is transmitted in the first communication cycle, the communication unit 42 associates the communication cycle number “1” with time information representing the time when the communication frame was transmitted, and stores the time information in the correspondence table.

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

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

The description of the processing flow of the master device 20 with reference to FIG. 5 will be temporarily interrupted here. The remaining steps S6 to S9 will be explained again after explaining the flow of the processes in the slave devices 40A to 40C.

FIG. 6 is a diagram explaining the flow of processing in the slave devices 40A-40C. In the slave device 40, the control unit 41 controls the communication unit 42 so as to wait for a certain period of time until receiving the forward communication frame and the return communication frame. Based on this control, the communication unit 42 starts a communication frame reception standby timer (S11). After starting the timer, the communication unit 42 determines whether or not a forward communication frame has been received (S12). When determining that the outgoing communication frame has been received (YES in S12), the communication unit 42 acquires the communication quality value at the time of receiving the outgoing communication frame from the communication quality value monitor log (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 at which 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 that, the process proceeds to step S19.

When the communication unit 42 determines that the forward communication frame is not received (NO in S12), it determines whether the communication has timed out (S15). The communication unit 42 determines that the communication has timed out when the timer expires without receiving the outgoing communication frame. On the other hand, if the timer has not expired, it is determined that the communication has not timed out. When the communication unit 42 determines that the communication has not timed out (NO in S15), the communication unit 42 returns to the process of step S2 and again determines whether or not the outgoing communication frame has been received.

When the communication unit 42 determines that the communication has timed out (YES in S15), it acquires the communication quality value at the estimated reception time of the outgoing communication frame from the communication quality value monitor log (S16). The "estimated reception time of the forward communication frame" here means the time at which the forward communication frame would have been normally received if there was no time-out. This time can be obtained from the reception time interval when each forward frame was received in the past and the time at which the forward communication frame was received last time. For example, the communication unit 42 may determine the point of time obtained by adding the reception time interval to the time when the forward communication frame was received last time as the "estimated reception point of the forward communication frame".

The communication quality monitor unit 43 monitors the communication quality value at regular time intervals regardless of whether or not an outgoing communication frame is received, and associates the monitored communication quality value with time information representing the time at the time of monitoring to perform communication. It is recorded in non-volatile memory as a quality value monitor log. Therefore, the communication unit 42 generates time information representing the estimated reception time of the outgoing communication frame, and uses the communication quality value stored in the communication quality value monitor log in association with this time information as the outgoing communication frame. Acquired as the communication quality value at the estimated reception time of the communication frame.

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 has been received and the acquired communication quality value in the non-volatile memory in association with the generated time information (S17). Next, the communication unit 42 acquires each communication quality value at each time from the time when the communication timed out until a certain time ago from the monitor log of the communication quality value (S18). The communication unit 42 records each acquired communication quality value in the non-volatile memory in association with the time information representing the estimated reception time of the outgoing communication frame (S19). After that, the process proceeds to step S20.

After receiving (or not receiving) an outgoing communication frame, the communication unit 42 determines whether or not a return communication frame has been received (S20). When determining that the return communication frame has been received (YES in S20), the communication unit 42 acquires the communication quality value at the time of receiving the return communication frame from the nonvolatile 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 the non-volatile memory in association with the generated time information (S22). 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 restarts the timer. This prepares for reception of the next communication frame.

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

When the communication unit 42 determines that the communication has timed out (YES in S24), it acquires the communication quality value at the time of estimated reception of the return communication frame from the nonvolatile memory (S25). Since the method of obtaining the estimated reception time of the return communication frame is the same as the method of obtaining the estimated reception time of the forward communication frame described above, detailed description thereof will be omitted. The communication unit 42 further generates reception result information indicating that the return 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 return communication frame has been received and the acquired communication quality value in the non-volatile memory in association with the generated time information (S26). Next, the communication unit 42 acquires from the nonvolatile memory each communication quality value at each time from when the communication timed out until a certain time ago (S27). The communication unit 42 further associates each acquired communication quality value with the time information and records it in the non-volatile memory (S28). The communication unit 42 then returns to the process of step S1 and restarts the timer. This prepares for reception of the next communication frame.

Since the

slave devices

40A and 40B may receive both outgoing communication frames and return communication frames, they operate according to the processing flow shown in FIG. On the other hand, since the slave device 40C has no possibility of receiving a return communication frame, it operates according to only part of the processing flow shown in FIG. That is, the slave device 40C does not execute each process related to the return communication frame in the process flow shown in FIG. Therefore, the slave device 40C does not record the reception result information and the communication quality value corresponding to the return communication frame in association with the time information.

FIG. 7 is a diagram showing transmission paths of communication frames for each communication cycle. In the example shown in this figure, the master device 20 transmits a communication frame six times in total for each communication cycle time. In the first communication cycle and the second communication cycle, the communication frame reaches the slave device 40C and returns to the master device 20 normally. That is, all of the slave devices 40A to 40C can normally receive and transmit communication frames. In the third to fifth communication cycles, the communication frame has not reached the slave device 40C and therefore has not been sent back to the master device 20. FIG. That is, the slave device 40C cannot normally receive the outgoing communication frame. Therefore, the

slave devices

40A and 40B have received the outgoing communication frame, but have not received the return communication frame. In the sixth communication cycle, the communication frame reaches the slave device 40C and returns to the master device 20 normally. That is, the communication abnormality in the slave device 40C is recovered between the fifth communication cycle and the sixth communication cycle.

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. FIG. The example 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.

Here, we return to the description of the processing of the master device 20 shown in FIG. As described above, when the communication unit 22 of the master device 20 determines not to receive the communication frame returned from the slave device 40, 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 examples of FIGS. 7 and 8, the communication unit 42 will transmit the message if it does not receive the third, fourth, and fifth communication frames in succession. The transmission path of the message is the same as the destination in the transmission path of the communication frame. That is, master device 20 transmits a message to 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 received messages to other devices. That is, the slave device 40C is the point of arrival of the message.

When the slave devices 40A to 40C receive the message, they transmit to the master device 20 the communication frame reception result information, the communication quality value, and the time information in each communication cycle. Here, in response to transmitting a message when the communication unit 22 does not receive three communication frames consecutively, the reception result information, communication quality value, and time information for the latest three consecutive communication frames are sent. The communication unit 22 of the master device 20 receives the communication frame reception result information, the communication quality value, and the time information in each communication cycle from the slave devices 40A to 40C (S5).

The specifying unit 23 of the master device 20 sorts the received reception status information based on the time information associated with the received reception status information (S6). For example, sorting is performed so that reception result information with older time information is arranged at the beginning. Similarly, each received communication quality value is sorted based on the time information associated with each received reception/non-reception information. The specifying unit 23 further refers to a correspondence table between time information and communication cycle numbers, and converts the time information associated with each piece of reception result information into a communication cycle number. For example, the correspondence table is searched for time information closest to the time information associated with certain reception result information, and the communication cycle number stored in the correspondence table in association with the found time information is acquired. Then, the time information associated with certain reception result information is converted into the acquired communication cycle number. Thereby, the identifying unit 23 can accurately identify the communication cycle number of the communication frame corresponding to each piece of reception result information.

The identifying unit 23 generates a table as shown in FIG. 8 as a result of executing these processes. The table in FIG. 8 stores forward communication frame reception result information and communication quality values in the slave devices 40A to 40C in the third to fifth communication cycles. Furthermore, return communication frame reception result information and communication quality values in the

slave devices

40A and 40B in the third to fifth communication cycles are stored. Since the slave device 40C does not receive the return communication frame, the table in FIG. 8 does not store the reception result information and the communication quality value of the return communication frame in the slave device 40C.

The specifying unit 23 refers to the table of FIG. 8, and in order of the communication cycle number, and in the order of the outgoing communication frames of the

slave devices

40A, 40B, and 40C and the incoming communication frames of the

slave devices

40A, 40B, and 40C, The result of presence/absence of communication frame reception is confirmed (S7). The communication unit 42 identifies the communication port for receiving the communication frame in which "none" is found first as the communication error cause port (S8).

When referring to the table in FIG. 8, the specifying unit 23 first checks the reception result information of the communication frame going to the slave device 40A in the third communication cycle with the smallest communication cycle number. Since this is "yes", the specifying unit 23 next 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 specifying unit 23 next checks the value of the reception result information of the communication frame to the slave device 40C in the third communication cycle. Since this is "none", the specifying unit 23 stops searching the table. The specifying unit 23 specifies the communication port 61 of the slave device 40C for receiving the outgoing communication frame corresponding to the reception result information that is first recognized as "none" as the communication error cause port. In this way, the identifying unit 23 identifies the slave device 40 in which the communication abnormality has occurred in the industrial network system.

The identifying unit 23 acquires the communication quality value of the communication frame to the slave device 40C in the third communication cycle from the table of FIG. 8 as the communication quality value of the communication error cause port. The display unit 24 displays the recognized communication error cause port and the communication quality value of the port on the display device 11 (S9). For example, a message such as "Abnormal occurrence in communication port 61 of slave device 40C, communication quality value=3" is displayed. By checking this display, the administrator of the industrial network system 1 can know that some kind of abnormality has occurred in the communication port 61 of the slave device 40C while the industrial network system 1 is in operation. The administrator can further consider that the communication quality value of the communication port 61 of the slave device 40C is "3" and examine whether the abnormality is noise generated in the slave device 40C.

As described above, the communication units 42 of the daisy-chained slave devices 40A to 40C store the reception result information indicating whether or not the communication frame has been received in the non-volatile memory when the reception of the periodically transmitted communication frame times out. Record. If the communication frame transmitted to the slave devices 40A-40C does not return to the master device 20, the master device 20 acquires the reception result information from each of the slave devices 40A-40C, and further confirms the content of each reception result information. . Thereby, the master device 20 can easily identify the communication port in which the abnormality has occurred in the industrial network system 1 . 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 in order to confirm that each communication unit 22 has a communication error.

<Modification>
The communication unit 22 of the master device 20 can also transmit to the slave devices 40A to 40C communication frames pre-associated with the communication cycle numbers in which the communication frames are transmitted. In this case, when receiving a communication frame, the communication units 42 of the slave devices 40A to 40C acquire 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. Further, when receiving a message from the master device 20 , the communication section 42 transmits to the master device 20 the reception result information of the communication frame in each communication cycle, the communication quality value, and the communication cycle number. Therefore, the specifying 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 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.

The display unit 24 can display the table itself shown in FIG. In this case, the administrator can know that an abnormality has occurred in the communication port 61 of the slave device 40C during the transmission period of each of the third to fifth communication frames.

The display unit 24 can further display on the display device 11 each communication quality value for a certain period of time before the communication timed out at the communication error cause port together with the communication quality value of the communication error cause port. For example, each communication quality value a certain time before the communication timed out, which is associated with the communication quality value of the communication frame to the slave device 40C in the third communication cycle, is displayed in a graph format. This allows the administrator to know the temporal change in the communication quality value at the communication port 61 of the slave device 40C in which an error has occurred.

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

In the latter case, the control device is equipped with a computer that executes program instructions, which are software that implements each function. This computer includes, for example, one or more processors, and a computer-readable recording medium storing the program. In the computer, the processor reads the program from the recording medium and executes it, thereby achieving the object of the present invention.

As the processor, for example, a CPU (Central Processing Unit) can be used. As the recording medium, a "non-temporary 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 can be used.

In addition, a RAM (Random Access Memory) for expanding the program may be further provided. Also, the program may be supplied to the computer via any transmission medium (communication network, broadcast wave, etc.) capable of transmitting the program. Note that one aspect of the present invention can also be implemented in the form of a data signal embedded in a carrier wave in which the program is embodied by electronic transmission.

〔summary〕
A slave device according to an aspect of the present invention is one of a plurality of slave devices linked to a master device and serially connected to each other, periodically transmitted from the master device, and a receiving unit for receiving a communication frame that goes through the plurality of slave devices and returns to the master device, and if communication times out without the receiving unit receiving the communication frame, the communication frame is not received. and a transmission unit for transmitting the reception result information to the master device.

According to the above configuration, the slave device receives communication frames 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. When communication times out without receiving a communication frame, the slave device 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 error occurred based on the received reception result information. In this case, the master device does not need to send a signal such as ping to each slave device to confirm whether or not communication with each slave device is performed normally. Therefore, the master device can easily identify the location (slave device) where the communication error occurred.

In one embodiment, a monitor unit is further provided for periodically monitoring a communication quality value representing the quality of the communication, and the recording unit records the communication quality value at the time of estimated reception of the communication frame as the reception result. Information is further recorded in association with the information, and the transmission unit transmits the recorded reception result information and the communication quality value to the master device.

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 noise is the cause of the communication abnormality.

In one embodiment, the recording unit records the reception result information and the communication quality value in association with time information representing the time of the estimated reception time, and the transmission unit records the recorded reception result information, the The communication quality value and the time information are transmitted to the master device.

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

In one embodiment, the communication quality value is the SQI value.

According to the above configuration, the administrator can refer to the displayed SQI value to determine whether the cause of the communication abnormality is noise.

A method of controlling a slave device according to an aspect of the present invention is a method of controlling one of a plurality of slave devices linked to a master device and connected in series with each other, comprising: receiving a communication frame that is periodically transmitted and that loops through the plurality of slave devices and returns to the master device; and if the communication times out without receiving the communication frame, the communication receives the communication frame. a step of recording reception result information indicating that the transmission was not performed; and a transmission step of transmitting the reception result information to the master device.

According to the above configuration, the master device can easily identify the location (slave device) where the communication error occurred.

A communication abnormality identification system according to an aspect of the present invention is a communication abnormality identification system including any of the slave devices described above and a master device, wherein the master device receives A receiving unit for receiving result information, and a specifying unit for specifying the slave device in which the communication abnormality has occurred based on the received reception result information.

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 technical means disclosed in different embodiments are also included in the technical scope of the present invention. A new technical feature can be formed by combining the technical means disclosed in each embodiment.

1 Industrial network system 10 Server 11 Display device 20

Master devices

21, 41

Control units

22, 42 Communication unit 23 Identification unit 24 Display unit 30

Hubs

40, 40A, 40B, 40C Slave device 43 Communication quality monitor

units

50, 51, 52

Control computers

61, 62 Communication port 300 Cable

Claims

one slave device of a plurality of slave devices linked to the master device and serially connected to each other,
a receiving unit that receives a communication frame that is periodically transmitted from the master device and returns to the master device after circulating through the plurality of slave devices;
a recording unit that records reception result information indicating that the communication frame has not been received when communication times out without the receiving unit receiving the communication frame;
a transmitting unit configured to transmit the reception result information to the master device.
further comprising a monitor unit that periodically monitors a communication quality value representing 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,
2. The slave device according to claim 1, wherein the transmission unit transmits the recorded reception result information and the communication quality value to the master device.
The recording unit records the reception result information and the communication quality value at the estimated reception time in association with time information representing the time at the estimated reception time,
3. The slave device according to claim 2, wherein the transmission unit transmits the recorded reception result information, the communication quality value, and the time information to the master device.
The slave device according to claim 2 or 3, wherein the communication quality value is an SQI value.
A method of controlling one of a plurality of slave devices linked to a master device and serially connected to each other, comprising:
receiving a communication frame periodically transmitted from the master device and looping through the plurality of slave devices and returning to the master device;
when communication times out without receiving the communication frame, recording reception result information indicating that the communication frame was not received;
and a transmission step of transmitting the reception result information to the master device.
A communication abnormality point identification system comprising a slave device according to any one of claims 1 to 4 and a master device,
The master device
a receiving unit that receives reception result information transmitted from the slave device;
and a specifying unit that specifies the slave device in which the communication error has occurred based on the received reception result information.