COMMUNICATION DEVICE, COMMUNICATION CONTROL METHOD, AND COMMUNICATION CONTROL PROGRAM

Abstract

To provide a novel mechanism for maintaining stability in redundant networks.SOLUTION: A communication device includes a communication unit connected to a network configured such that frames circulate around. At least some pathways in the network are made redundant. One or a plurality of devices are connected to the network. The communication device includes: a gathering unit for gathering statistical information pertaining to the frames being delivered through the network; a connection management unit for transmitting a command to two devices to thereby logically disconnect a segment between the two devices; and an identification unit for identifying a segment included in the network in which a hindrance has occurred, the segment being identified on the basis of a change in statistical information when the segment is logically disconnected.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a communication device connected to a network, a communication control method in the communication device, and a communication control program for implementing the communication control method in the communication device. [Background technology]

[0002] For example, in a network conforming to EtherCAT (registered trademark), a communication frame (hereinafter also simply referred to as a "frame") transmitted by a communication master (hereinafter also simply referred to as a "master") circulates through all communication slaves (hereinafter also simply referred to as "slaves") before returning to the master. Normally, if a portion of the path along which the frame circulates is cut off, the frame cannot be transmitted between all slaves.

[0003] In order to improve the resistance to failures that occur in such networks, networks with redundant frame transmission paths have also been put to practical use. For ease of explanation, a network with redundant paths is referred to as a "redundant network" or a "ring configuration," and a network without redundant paths is referred to as a "non-redundant network" or a "non-ring configuration."

[0004] Meanwhile, techniques and methods for detecting faults occurring in a network have been proposed. For example, Japanese Patent Laid-Open Publication No. 2008-244714 (Patent Document 1) discloses a line testing device and a line testing method capable of performing an out-of-service line test without causing a communication interruption of the main signal. Japanese Patent Laid-Open Publication No. 11-112539 (Patent Document 2) discloses a technique for preventing the communication function of the entire ring network from being stopped even if a failure occurs in one of the elements of the ring network. Japanese Patent Laid-Open Publication No. 64-16145 (Patent Document 3) discloses a network configuration control method suitable for quickly recovering communication functions when an abnormality occurs. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-244714 A [Patent Document 2] Japanese Patent Application Publication No. 11-112539 [Patent Document 3] Japanese Patent Application Publication No. 16145 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, a redundant network has the advantage of being able to continue transmitting frames even in the event of a permanent fault such as a disconnection, but faults that occur in a network are not only permanent but also temporary. An example of a temporary fault is a situation in which frames are lost due to intermittent noise generated by a device close to the network. When such a situation occurs, the stability of frame transmission decreases. It is also possible that frames cannot be transmitted stably due to deterioration of parts, etc.

[0007] An object of one aspect of the present invention is to provide a new mechanism for maintaining stability in a redundant network. [Means for solving the problem]

[0008] A communication device according to an embodiment of the present invention includes a communication unit connected to a network configured to circulate frames. At least a portion of the paths of the network are made redundant. One or more devices are connected to the network. The communication device includes a collection unit that collects statistical information about frames transmitted through the network, a connection management unit that logically disconnects a section between two devices by sending a command to the two devices, and an identification unit that identifies a section in which a failure has occurred based on a change in the statistical information when a section included in the network is logically disconnected.

[0009] According to this configuration, when a section between two devices is logically disconnected, if a fault occurs in that section, a change in the statistical information may occur. Based on such a change in the statistical information, the section in which the fault occurs can be reliably identified. By identifying the section in which the fault occurs, the effects of the fault can be more easily eliminated.

[0010] The connection management unit may maintain the section in which the failure occurs isolated from the network, thereby eliminating the influence of the section in which the failure occurs.

[0011] The connection management unit may be configured to separate a section in which a failure has occurred from the network in accordance with a user operation. With this configuration, for example, when failures have occurred in multiple sections, the user can determine which section should be preferentially separated.

[0012] The statistical information may include an error occurrence rate indicating the ratio of the number of lost frames and frames in which errors occurred to the number of frames transmitted from the communication device. With this configuration, it is possible to quantitatively evaluate errors that may occur in frames transmitted through the network.

[0013] The identification unit may determine the likelihood that a fault has occurred in a section based on the degree to which the error occurrence rate in each logically connected section is suppressed. With this configuration, when faults have occurred in multiple sections, it is possible to easily identify the fault that is likely to have the greatest impact.

[0014] The identification unit may be configured to start a process of identifying a section in which a failure has occurred when the statistical information satisfies a predetermined condition. With this configuration, unless some kind of failure occurs, the process of identifying a section in which a failure has occurred is not started, so that the processing load on the communication device can be reduced.

[0015] The connection management unit may be configured to sequentially select two adjacent devices, transmit a command to close the ports to the two selected devices, and then transmit a command to open the ports to the two selected devices. With this configuration, two devices are arbitrarily selected sequentially, and the section between each of the two selected devices can be evaluated sequentially.

[0016] The communication device further includes a notification unit for notifying an external party of the section in which the failure has occurred. With this configuration, it is possible to notify a user or the like of the section in which the failure has occurred.

[0017] According to another embodiment of the present invention, there is provided a communication control method executed in a communication device connected to a network configured to circulate frames. At least a part of the paths of the network are made redundant. One or more devices are connected to the network. The communication control method includes the steps of: collecting statistical information about frames transmitted through the network; logically disconnecting a section between the two devices by sending a command to the two devices; and identifying a section in which a fault has occurred based on a change in the statistical information when the section included in the network is logically disconnected.

[0018] According to yet another embodiment of the present invention, there is provided a communication control program executed by a computer connected to a network configured to circulate frames. At least a portion of the paths of the network are made redundant. One or more devices are connected to the network. The communication control program causes the computer to execute the steps of: collecting statistical information about frames transmitted through the network; logically disconnecting a section between the two devices by sending a command to the two devices; and identifying a section in which a fault has occurred based on a change in the statistical information when the section included in the network is logically disconnected. Effect of the Invention

[0019] According to an embodiment of the present invention, stability in a redundant network can be maintained. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic diagram showing an example of a network configuration of a communication system according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic diagram showing an example of a hardware configuration of a PLC in the communication system according to the present embodiment. [Diagram 3] FIG. 2 is a schematic diagram showing an example of a hardware configuration of a device in the communication system according to the present embodiment. [Figure 4] 2 is a schematic diagram showing an example of a hardware configuration of a relay device in the communication system according to the present embodiment. FIG. [Diagram 5] 1 is a diagram for explaining an example of a process for identifying and isolating a fault location in a communication system according to the present embodiment. FIG. [Figure 6] 10 is a flowchart showing a processing procedure for identifying and isolating a fault location in the communication system according to the present embodiment. [Figure 7] FIG. 11 is a diagram for explaining a processing example when there is one failure point in the communication system according to the present embodiment. [Figure 8] FIG. 11 is a diagram for explaining a processing example when there are two failure points in the communication system according to the present embodiment. [Figure 9] 10 is a diagram for explaining an example of processing when a failure occurs in a non-redundant path in the communication system according to the present embodiment. FIG. [Figure 10] FIG. 2 is a schematic diagram showing an example of a hardware configuration of a support device in the communication system according to the present embodiment. [Figure 11] 10 is a schematic diagram showing an example of a user interface screen provided by a support device of the communication system according to the present embodiment. FIG. [Figure 12] 13 is a schematic diagram showing another example of a user interface screen provided by a support device of the communication system according to the present embodiment. FIG. [Figure 13] It is a schematic diagram showing still another example of a user interface screen provided by a support device of a communication system according to the present embodiment. [Figure 14] It is a diagram showing an example of a redundant network that can be adopted in a communication system according to the present embodiment.

Mode for Carrying Out the Invention

[0021] Embodiments of the present invention will be described in detail with reference to the drawings. For the same or corresponding parts in the drawings, the same reference numerals are given and the description thereof will not be repeated.

[0022] <A. Application Example> First, an example of a scenario to which the present invention is applied will be described.

[0023] FIG. 1 is a schematic diagram showing an example of a network configuration of a communication system 1 according to the present embodiment. Referring to FIGS. 1(A) and 1(B), the communication system 1 includes a communication device (as an example, PLC100) that functions as a communication master (master), and functional devices 200-1 to 200-5 such as input / output devices that function as communication slaves (slaves) (hereinafter, also collectively referred to as "functional devices 200") and a relay device 300. Further, the functional devices 200 and the relay device 300 may also be collectively referred to as "devices" or "slave devices". Both the master and the devices are connected to the network.

[0024] In the following description, as an example of a communication device, a PLC (programmable logic controller) that executes arbitrary control operations is assumed for description, but the present invention is applicable not only to a PLC but also to any device that can function as a master.

[0025] The PLC 100 has a port 151 for transmitting and receiving frames. Each of the functional devices 200-1 to 200-5 has a first port 251 and a second port 252 for transmitting and receiving frames.

[0026] In each of the functional devices 200, the first port 251 is normally used as a port (IN port) for inputting a frame, and the second port 252 is used as a port (OUT port) for outputting a frame. However, when a part of a path constituting the network is disconnected, each of the first port 251 and the second port 252 is used as a port (IN port) for inputting a frame and / or a port (OUT port) for outputting a frame.

[0027] The relay device 300 has a first port 351, a second port 352, and a third port 353 for transmitting and receiving frames. When the relay device 300 receives a frame at a certain port, the relay device 300 transmits the received frame from another port determined according to a predetermined rule. In the example shown in FIG. 1(A), a cyclic rule such as first port 351→second port 352→third port 353→first port 351→.. may be adopted as the predetermined rule.

[0028] In normal frame transmission, a frame transmitted from port 151 of PLC 100 travels in the following order: cable 20, first port 351 of relay device 300, second port 352 of relay device 300, cable 21, first port 251 of functional device 200-1, second port 252 of functional device 200-1, cable 22, first port 251 of functional device 200-2, second port 252 of functional device 200-2, cable 23, first port 251 of functional device 200-3, second port 252 of functional device 200-3, cable 24, first port 251 of functional device 200-4, second port 252 of functional device 200-4, cable 25, first port 251 of functional device 200-5, second port 252 of functional device 200-5, cable 26, third port 353 of relay device 300, and cable 20, before returning to port 151 of PLC 100.

[0029] 1, the route from the relay device 300 to the terminal functional device 200-5 includes the route of the cables 21 to 25 and the route of the cable 26. That is, the network has two routes, and at least a part of the routes is made redundant.

[0030] The PLC 100 includes, as its functional components, a collection module 50, a connection management module 60, and a specification module 70.

[0031] A collection module 50 collects statistics about frames transmitted through the network.

[0032] The connection management module 60 manages the disconnection / connection of any section of the network by sending any command to devices (the functional device 200 and the relay device 300) connected to the network. Typically, the connection management module 60 logically disconnects the section between two adjacent devices by sending a command to logically close a port to the two devices. Also, the connection management module 60 logically connects the section between the two adjacent devices by sending a command to logically open a port to the two devices.

[0033] The identification module 70 identifies a section in which a failure has occurred based on a change in statistical information when a section included in a network is logically disconnected.

[0034] In this specification, the term "fault" is a concept that encompasses any event that adversely affects the transmission of frames. Examples of "faults" include those caused by external noise that inhibits the transmission of frames, those caused by deterioration of parts, and those caused by disconnection or breakage of cables.

[0035] A typical example of identifying a section where a fault occurs by the identifying module 70 will be described below.

[0036] As shown in FIG. 1(A), assume that a failure has occurred between the functional device 200-2 and the functional device 200-3. In this state, the frame transmission on the network is affected, and the statistical information collected by the collection module 50 will include features indicating that some abnormality has occurred in the frame transmission.

[0037] Here, as shown in FIG. 1(B), assume that the connection management module 60 logically disconnects the section between the functional device 200-2 and the functional device 200-3. Then, since the frame is folded back at the functional device 200-2 and the functional device 200-3 respectively, it will no longer pass through the section between the malfunctioning functional device 200-2 and the functional device 200-3. As a result, the influence on the frame transmission is eliminated, and the statistical information collected by the collection module 50 will have the features indicating that some abnormality has occurred in the frame transmission suppressed.

[0038] The connection management module 60 sequentially switches the section to be logically disconnected, and the specific module 70 identifies the section where the failure has occurred based on the change in the statistical information for each section that is logically disconnected.

[0039] Hereinafter, the configuration, processing, functions, etc. for realizing such a mechanism will be described in detail. <B. Hardware Configuration Example> Next, a hardware configuration example of each device constituting the communication system 1 according to the present embodiment will be described.

[0040] (b1: Communication Device (PLC100)) FIG. 2 is a schematic diagram showing a hardware configuration example of the PLC100 of the communication system 1 according to the present embodiment. Referring to FIG. 2, the PLC100 includes, as main hardware components, a processor 102, a main memory 104, a storage 110, a field network controller 112, and a local bus controller 114. These hardware components are electrically connected via an internal bus 118.

[0041] The processor 102 corresponds to an arithmetic processing unit that executes control calculations, and is composed of a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc. Specifically, the processor 102 reads out a program stored in the storage 110, expands it in the main memory 104, and executes it to realize control calculations according to a control target and various processes as described later.

[0042] The main memory 104 is configured with a volatile storage device such as a dynamic random access memory (DRAM) or a static random access memory (SRAM). The storage 110 is configured with a non-volatile storage device such as a solid state drive (SSD) or a hard disk drive (HDD).

[0043] The storage 110 stores a system program 1102 for implementing basic functions, a user program 1104 created according to a control target, and the like. The system program 1102 implements basic functions in the PLC 100 and can therefore be regarded as at least a part of the communication control program.

[0044] Typically, the system programs 1102 include instructions for implementing the connection management module 60 and the specific modules 70 (FIG. 1).

[0045] The field network controller 112 corresponds to a communication unit, and is connected to a network configured to circulate frames. More specifically, the field network controller 112 has a port 151, and is responsible for transmitting and receiving frames. The field network controller 112 of the PLC 100 has a network management module 1122 for functioning as a master. The network management module 1122 collects statistical information about frames transmitted through the network. That is, the network management module 1122 includes the collection module 50 (FIG. 1). Furthermore, the field network controller 112 may have a synchronization counter for periodically transmitting and receiving frames.

[0046] The local bus controller 114 is electrically connected to one or more functional units 116 via an internal bus 118. The functional units 116 include functions for exchanging various signals with the controlled object. The functional units 116 have, for example, one or more of a DI (Digital Input) function for receiving a digital signal from the controlled object, a DO (Digital Output) function for outputting a digital signal to the controlled object, an AI (Analog Input) function for receiving an analog signal from the controlled object, and an AO (Analog Output) function for outputting an analog signal to the controlled object. Furthermore, the functional units 116 may include a controller that implements special functions such as PID (Proportional Integral Derivative) control and motion control.

[0047] FIG. 2 shows an example of a configuration in which the processor 102 executes a program to provide the necessary functions, but some or all of these provided functions may be implemented using a dedicated hardware circuit (e.g., an Application Specific Integrated Circuit (ASIC) or a Field-Programmable Gate Array (FPGA)). Alternatively, the main part of the PLC 100 may be realized using hardware that conforms to a general-purpose architecture (e.g., an industrial PC based on a general-purpose PC). In this case, virtualization technology may be used to run multiple operating systems (OSs) with different uses in parallel, and necessary applications may be executed on each OS.

[0048] Furthermore, each of the collection module 50, the connection management module 60, and the identification module 70 shown in FIG. 1 may be implemented in any manner.

[0049] Furthermore, a configuration may be adopted in which the functions of a display device, a support device, etc. are integrated into the PLC 100.

[0050] (b2: functional device 200) Fig. 3 is a schematic diagram showing an example of a hardware configuration of a functional device 200 of a communication system 1 according to the present embodiment. Referring to Fig. 3, the functional device 200 includes, as main hardware components, a control circuit 206, a field network controller 212, and a functional module 220.

[0051] The control circuit 206 is an arithmetic processing unit that mainly executes processing in the functional device 200. The control circuit 206 typically includes a processor 202, a main memory 204, and a storage 210. The processor 202 is configured with a CPU, a GPU, or the like. The main memory 204 is configured with a volatile storage device such as a DRAM or an SRAM, or the like. The storage 210 is configured with a non-volatile storage device such as an SSD, or the like. Note that a ROM (Read Only Memory) may be adopted as the storage 210.

[0052] The control circuit 206 may be implemented using a dedicated hardware circuit (eg, ASIC or FPGA).

[0053] The field network controller 212 has a first port 251 and a second port 252, and is responsible for transmitting and receiving frames. The field network controller 212 of the functional device 200 functions as a communication slave. The field network controller 212 may have a synchronization counter for periodically transmitting and receiving frames.

[0054] The functional module 220, like the functional unit 116 shown in FIG. 2, is responsible for processing such as exchanging various signals with the controlled object.

[0055] (b3: Relay device 300) 4 is a schematic diagram showing an example of a hardware configuration of the relay device 300 of the communication system 1 according to the present embodiment. Referring to Fig. 4, the relay device 300 includes, as main hardware components, a control circuit 306 and a field network interface 312.

[0056] The control circuit 306 is an arithmetic processing unit that mainly executes frame transmission processing in the relay device 300. The control circuit 306 typically includes a processor 302, a main memory 304, and a storage 310. The processor 302 is composed of a CPU, a GPU, etc. The main memory 304 is composed of a volatile storage device such as DRAM or SRAM. The storage 310 is composed of a non-volatile storage device such as an SSD, for example. Note that a ROM may be adopted as the storage 310.

[0057] Note that the control circuit 306 may be implemented using a dedicated hardware circuit (such as an ASIC or an FPGA).

[0058] The field network interface 312 has a first port 351, a second port 352, and a third port 353 for transmitting and receiving frames. Note that the relay device 300 is also treated as one slave when viewed from the master.

[0059] <C. Identification and Isolation of Fault Locations> Next, the process of identifying and isolating fault locations in the communication system 1 according to this embodiment will be described. The communication system 1 according to this embodiment identifies (or estimates) a location where some fault has occurred (hereinafter also referred to as a "fault location") based on changes in statistical information collected by the PLC 100 that functions as a master.

[0060] More specifically, the PLC 100 logically disconnects each section of the network sequentially, and identifies the fault location from the changes in statistical information that occur according to the disconnected section.

[0061] Note that since the communication system 1 adopts a redundant network (ring configuration), even if a part of the path constituting the network is logically disconnected, frame transmission continues.

[0062] Here, the statistical information is a result of aggregating the status of frames transmitted through a network over a predetermined period of time, and includes, for example, information on frame loss and occurrence of error frames. More specifically, frame loss refers to a state in which a frame transmitted from the PLC 100 does not return to the PLC 100 within a predetermined time (times out). Moreover, occurrence of an error frame refers to a state in which data in the frame is corrupted based on error detection information (such as a check bit or parity bit) contained in the frame. Hereinafter, the frequency at which some abnormality contained in the statistical information occurs is also collectively referred to as the "error occurrence rate." The error occurrence rate corresponds to the number of errors occurring per unit time. More specifically, the error occurrence rate indicates the ratio of the number of lost frames and frames in which errors occur to the number of frames transmitted from the PLC 100.

[0063] The PLC 100 can send commands to any device (the functional device 200 and the relay device 300) to logically open / close a port. Meanwhile, each device logically opens / closes a specified port according to the command from the PLC 100. By logically closing a port, it becomes impossible to send or receive frames via the target port, which is essentially the same as if the target port were physically disconnected. Conversely, by logically opening a port, it is essentially the same as if the target port were physically connected.

[0064] As a specific processing order, first, the PLC 100 detects the occurrence of some kind of fault by detecting an increase in the error occurrence rate in the statistical information 160. Then, the PLC 100 sequentially disconnects each section of the network by sending a command to the functional device 200, and determines whether the disconnected section is the fault location based on the change in the statistical information 160 in each state. Finally, the PLC 100 isolates the section corresponding to the identified fault location.

[0065] Fig. 5 is a diagram for explaining an example of a process for identifying and isolating a fault location in the communication system 1 according to the present embodiment. Fig. 5 shows an example in which a fault occurs between the functional device 200-2 and the functional device 200-3.

[0066] 5A, first, the PLC 100 disconnects the section between the relay device 300 and the functional device 200-1. More specifically, the PLC 100 transmits a command to close the second port 352 of the relay device 300 and a command to close the first port 251 of the functional device 200-1. Then, frames are no longer transmitted between the second port 352 of the relay device 300 and the first port 251 of the functional device 200-1.

[0067] In this state, in the relay device 300, a frame received at the first port 351 is transmitted from the third port 353, not the second port 352. Furthermore, when the functional device 200-1 receives a frame at the second port 252, it transmits the processed frame from the second port 252. That is, the frame is returned at the second port 252 of the functional device 200-1. By changing the transmission path of the frame in this way, the transmission of the frame continues.

[0068] The PLC 100 judges whether the error occurrence rate in the statistical information 160 continues to be relatively high with the section disconnected. In the state of FIG. 5(A), the disconnected section does not include the fault location, so the error occurrence rate continues to be relatively high. Therefore, the PLC 100 judges that the fault location is in another section. Then, the PLC 100 reconnects the disconnected section. More specifically, the PLC 100 transmits a command to open the second port 352 of the relay device 300 and a command to open the first port 251 of the functional device 200-1.

[0069] 5(B), next, the PLC 100 disconnects the section between the functional device 200-1 and the functional device 200-2. More specifically, the PLC 100 transmits a command to close the second port 252 of the functional device 200-1 and a command to close the first port 251 of the functional device 200-2. Then, frames are no longer transmitted between the second port 252 of the functional device 200-1 and the first port 251 of the functional device 200-2.

[0070] In this state, when the functional device 200-1 receives a frame at the first port 251, it transmits the processed frame from the first port 251. That is, the frame is returned at the first port 251 of the functional device 200-1. Similarly, when the functional device 200-2 receives a frame at the second port 252, it transmits the processed frame from the second port 252. That is, the frame is returned at the second port 252 of the functional device 200-2. By changing the frame transmission path in this way, the frame transmission continues.

[0071] With the section disconnected, the PLC 100 judges whether the error occurrence rate in the statistical information 160 continues to be relatively high. In the state of FIG. 5(B), the disconnected section does not include the fault location, so the error occurrence rate continues to be relatively high. Therefore, the PLC 100 judges that the fault location is in another section. Then, the PLC 100 reconnects the disconnected section. More specifically, the PLC 100 transmits a command to open the second port 252 of the functional device 200-1 and a command to open the first port 251 of the functional device 200-2.

[0072] 5(C), next, the PLC 100 disconnects the section between the functional device 200-2 and the functional device 200-3. More specifically, the PLC 100 transmits a command to close the second port 252 of the functional device 200-2 and a command to close the first port 251 of the functional device 200-3. As a result, frames are no longer transmitted between the second port 252 of the functional device 200-2 and the first port 251 of the functional device 200-3.

[0073] In this state, when the functional device 200-2 receives a frame at the first port 251, it transmits the processed frame from the first port 251. That is, the frame is returned at the first port 251 of the functional device 200-2. Similarly, when the functional device 200-3 receives a frame at the second port 252, it transmits the processed frame from the second port 252. That is, the frame is returned at the second port 252 of the functional device 200-3. By changing the frame transmission path in this way, the frame transmission continues.

[0074] With the section disconnected, the PLC 100 judges whether the error occurrence rate in the statistical information 160 continues to be relatively high. In the state of FIG. 5(C), the disconnected section includes the fault location, so the error occurrence rate is suppressed. Therefore, the PLC 100 judges that the fault location exists in the currently connected section. The PLC 100 then maintains the target section in the disconnected state. In this state, the process of identifying and isolating the fault location is completed.

[0075] Fig. 6 is a flowchart showing a procedure for identifying and isolating a fault location in the communication system 1 according to the present embodiment. Each step shown in Fig. 6 may be realized by the processor 102 of the PLC 100 functioning as the master executing a system program 1102 (an example of a communication control program).

[0076] 6, the PLC 100 collects statistical information 160 about frames transmitted through a network. More specifically, the PLC 100 acquires an error occurrence rate from the statistical information 160 (step S2). The PLC 100 then determines whether the acquired error occurrence rate satisfies a predetermined failure occurrence criterion (step S4). The failure occurrence criterion includes, for example, that the error occurrence rate exceeds a predetermined threshold value. If the acquired error occurrence rate does not satisfy the failure occurrence criterion (NO in step S4), the processing from step S2 onwards is repeated.

[0077] If the acquired error occurrence rate satisfies the fault occurrence criterion (YES in step S4), PLC 100 determines that some fault has occurred in the network (step S6). Then, PLC 100 starts the process of identifying and isolating the fault location as described below. In this way, PLC 100 may start the process of identifying the section in which the fault has occurred when statistical information 160 satisfies a predetermined condition.

[0078] The PLC 100 logically disconnects the section between the two devices by sending commands to the two devices. More specifically, the PLC 100 selects a target section from among the sections included in the network (step S8). The PLC 100 then sends commands to close each of the two ports connected to the selected target section (step S10). The closing commands logically disconnect the target section of the network.

[0079] Next, the PLC 100 acquires the error occurrence rate from the statistical information 160 (step S12). Then, the PLC 100 judges whether the acquired error occurrence rate satisfies a predetermined fault location identification criterion (step S14). The fault location identification criterion includes, for example, that the error occurrence rate is equal to or less than a predetermined threshold value. In other words, the PLC 100 judges whether the error occurrence rate has been suppressed by disconnecting the target section.

[0080] If the acquired error occurrence rate meets the failure occurrence criterion (YES in step S14), PLC 100 determines that a failure has occurred in the target section (step S16). PLC 100 performs necessary notification processing, etc. (step S18), and maintains the current target section in a disconnected state (step S20). In this way, PLC 100 maintains the state in which the section in which the failure has occurred is isolated from the network. Then, the process ends.

[0081] On the other hand, if the acquired error occurrence rate does not satisfy the fault occurrence criterion (NO in step S14), PLC 100 determines that no fault has occurred in the target section, and sends commands to open each of the two ports connected to the selected target section (step S22).

[0082] In this way, PLC 100 identifies the section in which the failure has occurred based on the change in statistical information 160 when the section included in the network is logically disconnected. At this time, PLC 100 sequentially selects two adjacent devices, transmits a command to close the ports to the two selected devices, and then transmits a command to open the ports to the two selected devices.

[0083] Next, the PLC 100 determines whether or not all of the sections included in the network have been selected (step S24).

[0084] If all of the sections included in the network have not been selected (NO in step S24), the PLC 100 selects a target section from among the sections included in the network that have not been selected (step S26), and then the processes from step S10 onwards are repeated.

[0085] If all sections included in the network have been selected (YES in step S24), the PLC 100 determines that it cannot uniquely identify the failure location (step S28). The PLC 100 executes a process for estimating the failure location as necessary (step S30). Then, the process ends.

[0086] <D. Estimation of Failure Location> Next, several examples of estimating the failure location will be described. Specifically, depending on how the error occurrence rate changes for each section, the possibility of a section being the failure location is estimated, and the sections to be separated are prioritized.

[0087] FIG. 7 is a diagram for explaining a processing example when there is one failure location in the communication system 1 according to the present embodiment. As shown in FIG. 7(A), assume an example where a failure has occurred between the functional device 200-2 and the functional device 200-3.

[0088] As shown in FIG. 7(B), assume that the error occurrence rate ( = number of error frames / number of frames transmitted), which is an example of the statistical information 160, was 10% before cutting the section of the network.

[0089] Note that the error occurrence rate is a value obtained in step S2 shown in FIG. 6, and is calculated as the error occurrence rate of the entire network ( = number of error frames / number of frames transmitted (or number of frames received)) based on the number of frames transmitted (or received) within a certain time and the number of error frames. Note that the number of error frames includes frames that have disappeared during transmission in addition to frames in which some error has occurred.

[0090] As described above, the PLC 100 identifies the failure location based on the change in the statistical information 160 while cutting each section. As shown in FIG. 7(C), the statistical information 160 includes the error occurrence rate when each section is cut.

[0091] The error occurrence rate when each section is disconnected is a value obtained in step S12 shown in FIG. 6, and is calculated as the error occurrence rate when each section is disconnected (=number of error frames / number of frames transmitted (or number of frames received)) based on the number of frames transmitted (or number of frames received) within a certain period of time and the number of error frames.

[0092] Based on the change in the error occurrence rate when each section is disconnected, the PLC 100 calculates a contribution rate as an effect of suppressing the error occurrence rate caused by disconnecting each section. The contribution rate indicates the degree to which the error occurrence rate of each logically connected section is suppressed. More specifically, the contribution rate means a ratio calculated based on the error occurrence rate before disconnection of the amount of reduction in the error occurrence rate when each section is disconnected. That is, the contribution rate is calculated as follows: contribution rate={(error occurrence rate before disconnection)-(error occurrence rate when each section is disconnected)} / (error occurrence rate before disconnection). In this way, the contribution rate is calculated based on the error occurrence rate of the entire network and the error occurrence rate when each section is disconnected.

[0093] 7C, the contribution rate of disconnecting between S3 and S4 (between the functional device 200-2 and the functional device 200-3) is 100%, and the contribution rate of the other sections is 0%, so the section to be disconnected is uniquely determined to be between S3 and S4. In other words, the priority level "1" is set only for the section between S3 and S4.

[0094] 8A and 8B are diagrams for explaining a processing example when there are two failure locations in the communication system 1 according to the present embodiment. As shown in FIG. 8A, an example is assumed in which failures occur between the functional device 200-2 and the functional device 200-3, and between the functional device 200-4 and the functional device 200-5.

[0095] As shown in FIG. 8B, it is assumed that the error occurrence rate (=number of error frames / number of transmitted frames), which is an example of the statistical information 160, was 10% before the network section was disconnected.

[0096] 8C, the contribution rate when S3-S4 (between the functional device 200-2 and the functional device 200-3) is disconnected is 70%, and the contribution rate when S5-S6 (between the functional device 200-4 and the functional device 200-5) is disconnected is 30%. Note that the contribution rate for other sections is 0%.

[0097] In this situation, the priority is set in descending order of contribution rate. That is, the priority level "1" is set for the section between S3 and S4, and the priority level "2" is set for the section between S5 and S6.

[0098] Ultimately, the section between S3 and S4, which has the highest priority, is determined to be the section to be disconnected. However, it is also possible that the section between S5 and S6, which has the next highest priority, may be selected as the section to be disconnected.

[0099] In this way, the PLC 100 may determine the possibility that a section is experiencing a failure based on a contribution rate that indicates the degree to which the error occurrence rate for each logically connected section is suppressed.

[0100] 9A and 9B are diagrams for explaining a processing example when a failure occurs in a non-redundant path in the communication system 1 according to the present embodiment. As shown in FIG. 9A, an example is assumed in which a failure occurs between the PLC 100 and the relay device 300.

[0101] As shown in FIG. 9B, it is assumed that the error occurrence rate (=number of error frames / number of transmitted frames), which is an example of the statistical information 160, was 10% before the network section was disconnected.

[0102] In the example shown in FIG. 9(C), the contribution rate is 0% regardless of which section is cut. Based on this result, the PLC 100 determines that there is no fault location in the cut section. Note that since the section between the PLC 100 and the relay device 300 is not redundant, it cannot be cut. Therefore, the PLC 100 notifies that some fault has occurred in the non-redundant path, etc.

[0103] As described above, the PLC 100 calculates the error occurrence rate for each section when cutting each section, and among the calculated error occurrence rates, determines that the section with a high degree of influence on the error occurrence rate of the entire network is likely to be a fault location, and determines it as a target for separation from the network. At this time, priority may be assigned to the targets for separation according to the degree of influence.

[0104] <E. Information provision to the user> Next, a configuration example in which the communication system 1 according to the present embodiment provides information to the user will be described.

[0105] (e1: Support device) The information provided by the communication system 1 may be provided to the user via a support device 400 connectable to the PLC 100.

[0106] FIG. 10 is a schematic diagram showing a hardware configuration example of the support device 400 of the communication system 1 according to the present embodiment. Referring to FIG. 10, the support device 400 is realized using, for example, hardware (e.g., a general-purpose personal computer) according to a general-purpose architecture.

[0107] The support device 400 provides an integrated development environment in which settings for the PLC 100 and the function device 200 of the communication system 1 and creation of the user program 1104 executed by the PLC 100 can be integrated. In the integrated development environment, debugging, simulation, etc. may also be possible.

[0108] 10, the support device 400 includes, as main hardware components, a processor 402, a main memory 404, an input unit 406, a display unit 408, a storage 410, a communication controller 412, an optical drive 416, and a USB controller 424. These hardware components are electrically connected via an internal bus 228.

[0109] The processor 402 is composed of a CPU, a GPU, and the like, and realizes the functions of the support device 400 by reading out a program stored in the storage 410, expanding it in the main memory 404, and executing it.

[0110] The main memory 404 is configured with a volatile storage device such as a DRAM or an SRAM, etc. The storage 410 is configured with a non-volatile storage device such as an HDD or an SSD, etc.

[0111] The storage 410 stores an OS 4102 for implementing basic functions, a development program 4104 for implementing an integrated development environment, and the like. The development program 4104 provides the integrated development environment by being executed by the processor 402.

[0112] The input unit 406 is composed of a keyboard, a mouse, and the like, and accepts user operations. The display unit 408 is composed of a display and various indicators, and outputs the processing results from the processor 402, etc.

[0113] The communication controller 412 exchanges data with any information processing device via any higher-level network.

[0114] The optical drive 416 can read any data from a storage medium 418 (eg, an optical storage medium such as a DVD) that non-transiently stores a computer-readable program, and can write any data to the storage medium 418 .

[0115] A USB controller 424 transmits and receives data to and from any information processing device via a USB connection.

[0116] A computer-readable program may be read from a storage medium 418 that non-transiently stores the program and installed in the storage 410. Alternatively, various programs executed by the support device 400 may be installed by downloading them from a server device on a network. In addition, the functions provided by the support device 400 according to this embodiment may be realized by using some of the modules provided by the OS 4102.

[0117] During operation of the communication system 1, the support device 400 may be removed from the PLC 100.

[0118] (e2: User interface example) In the communication system 1 according to the present embodiment, the PLC 100 has a notification function for externally notifying information such as a section where a fault has occurred. The information provided by the PLC 100 may be presented to a user via the support device 400 or the like. The information provided to the user may be, for example, the following:

[0119] -Identified fault locations - Isolated faults If the location of the failure cannot be identified, a failure occurs on a non-redundant path. FIG. 11 is a schematic diagram showing an example of a user interface screen provided by support device 400 of communication system 1 according to the present embodiment.

[0120] 11(A), the user interface screen 450 includes a network configuration diagram 452 showing a target network configuration. The network configuration diagram 452 shows the connection configuration of the PLC 100, the functional device 200, and the relay device 300 that make up the communication system 1. Among the nodes included in the network configuration diagram 452, sections identified as the fault location are superimposed with highlighting 454. The sections identified as the fault location by the highlighting 454 are displayed in a different manner from the other nodes. FIG. 11(A) shows an example in which two fault locations are identified, so two highlightings 454 are superimposed.

[0121] 11(A) further includes a separated mark 456 indicating a separated section. Even if multiple fault locations are identified, typically, only one section is separated, so that only one separated mark 456 is displayed.

[0122] 11(B) shows a user interface screen 450 when the user isolates the faulty portion from the network. The user uses cursor 460 to select the section to be isolated from among the sections with highlighting 454 superimposed on network configuration diagram 452. Then, a dialogue 458 for instructing isolation is displayed, and the user can isolate the selected section from the network by further selecting in the displayed dialogue 458. In this way, PLC 100 may isolate the section in which the fault has occurred from the network in accordance with a user operation.

[0123] Fig. 12 is a schematic diagram showing another example of a user interface screen provided by support device 400 of communication system 1 according to the present embodiment. Referring to Fig. 12, user interface screen 450 displays the contribution rate for a failure location. More specifically, user interface screen 450 includes network configuration diagram 452. When a user points to a failure location with cursor 460, contribution rate 462 of the target failure location is displayed. The user can refer to contribution rate 462 for each failure location to determine which failure location to isolate.

[0124] Fig. 13 is a schematic diagram showing yet another example of a user interface screen provided by support device 400 of communication system 1 according to the present embodiment. Referring to Fig. 13, a user interface screen 470 includes a contribution rate of each section.

[0125] The user can refer to the user interface screen 470 and check the contribution rate for each section to more easily select which fault location to isolate.

[0126] (e3: Form of information provision) The information provision as described above is not limited to the form using the user interface screen displayed on the support device 400 as described above, but any form as described below is possible.

[0127] (1) Support equipment As described above, the identified fault location and related information may be displayed using a user interface screen displayed on the support device 400.

[0128] Furthermore, the support device 400 may read and display the values ​​of system definition variables (for example, flags indicating the presence or absence of a fault and the location of the fault) managed by the PLC 100.

[0129] Further, the support device 400 may read and display an event log (including messages such as the details of a failure occurrence, etc.) managed by the PLC 100.

[0130] (2) HMI (Human Machine Interface) An HMI capable of communicating with the PLC 100 may be provided in the communication system 1. Similar to the support device 400, the HMI may provide various information read from the PLC 100 in an arbitrary manner.

[0131] (3) User program Dedicated instructions described in the user program 1104 executed by the PLC 100 may be used to provide various information in an arbitrary manner. The dedicated instructions may include instructions for acquiring failure information, instructions for starting / stopping the identification of the failure location, instructions for separating / reconnecting the failure location, etc.

[0132] By providing the user with the information as described above, it is possible to prompt the user of the occurrence of a failure and the repair of the failure location. Even in a redundant network, if any failure occurs, the stability decreases. Therefore, by repairing the failure location, it becomes possible to ensure the original stability earlier.

[0133] <F. Modification example> In addition to the typical embodiments described above, the following modifications are possible. Note that the modifications shown below can be applied in any appropriate combination of one or more. (1) Start conditions for the process of identifying and separating the failure location In the above-described embodiment, when the error occurrence rate satisfies a predetermined failure occurrence criterion, the process of identifying and separating the failure location is started. In this way, the PLC 100 may monitor the error occurrence rate and the number of error frames, and automatically start the process of identifying and separating the failure location when the predetermined conditions are satisfied.

[0134] Alternatively, the user may provide a dedicated command to the PLC 100 via the support device 400 to automatically initiate the process of identifying and isolating the fault location.

[0135] Alternatively, any start condition, including a dedicated command, may be written in the user program 1104, and the PLC 100 may execute the user program 1104 to automatically start fault location and isolation processing when the written start condition is satisfied.

[0136] The failure occurrence criteria may also be set arbitrarily by the user. For example, an arbitrary threshold may be used as the failure occurrence criteria, so that if the error occurrence rate is equal to or lower than a predetermined threshold, it is not regarded as a failure occurring in the network. (2) Statistical information As the statistical information, information from any viewpoint can be used.

[0137] For example, the frequency of abnormalities occurring per unit time (e.g., per second) may be used as statistical information, or the degree of abnormalities per unit frame (e.g., per 1000 frames) may be used as statistical information. Furthermore, the change over time in the number of abnormalities (error count) may be used as statistical information.

[0138] Furthermore, the unit time and the number of unit frames used as statistical information may be set arbitrarily by the user. (3) Separation and restoration Although an example of a process for identifying a fault location and then maintaining the identified fault location in an isolated state has been described, the user may be allowed to arbitrarily select whether or not to isolate the fault location. In this case, for example, the fault location may be isolated only when an instruction to isolate the fault location is received from the user while notifying the user of information that allows the user to identify the fault location.

[0139] The instruction to separate from the user may be given to the PLC 100 by the user operating the support device 400, or may be given to the PLC 100 using a dedicated instruction described in the user program 1104 executed by the PLC 100.

[0140] Also, when the cause of the failure occurring in the network is removed, the separation of the section including the failure location may be released (restored) by any method. For example, when the PLC 100 detects that the cable is physically removed and reconnected in the logically disconnected section, the PLC 100 may release the separation of the logically disconnected section. Alternatively, the user may operate the support device 400 to instruct the PLC 100 to reconnect the disconnected section. (4) Execution entity of the process In the above description, an example in which the PLC 100 functioning as a master executes all processes has been described. However, the present invention is not limited to this, and in addition to the PLC 100 functioning as a master, other devices may execute part or all of the processes.

[0141] As the other device, it may be the support device 400 connected to the PLC 100, or may be any information processing device other than the support device 400. Furthermore, the processes according to the present embodiment may be realized using computing resources on so-called clouds.

[0142] <G. Redundant network> In the above description, an example of a redundant network using the relay device 300 has been described. However, the present invention is not limited to this, and other configurations may be adopted.

[0143] FIG. 14 is a diagram showing an example of a redundant network that can be adopted in the communication system 1 according to the present embodiment.

[0144] FIG. 14(A) shows an example of a redundant network using a relay device 300 having three or more ports. The relay device 300 provides junction redundancy by having three or more ports. In the redundant network shown in FIG. 14(A), it includes a relay device 300 connected to the field network controller 112 (communication unit) of the PLC 100 and a plurality of functional devices 200.

[0145] FIG. 14(B) shows an example of a redundant network using a PLC 100 having two or more ports 151, 152. The PLC 100 provides cable redundancy by having two or more ports. In the redundant network shown in FIG. 14(B), the field network controller 112 (communication unit) of the PLC 100 has a plurality of ports connected to different functional devices 200 respectively.

[0146] Also, a redundant network may be configured by arbitrarily combining the relay device 300 shown in FIG. 14(A) and the PLC 100 shown in FIG. 14(B).

[0147] The communication control method according to the present embodiment is applicable not only to the above-described configuration examples but also to any redundant network. Also, as the communication protocol, it is applicable not only to EtherCAT but also to communication protocols that sequentially transfer data such as frames or packets.

[0148] <H. Supplementary Note> The present embodiment as described above includes the following technical ideas.

[0149] [Configuration 1] It includes a communication unit (112) connected to a network configured such that a frame makes a round trip, at least a part of the path of the network is redundant, and one or more devices (200, 300) are connected to the network. a collection unit (50; 1122) for collecting statistical information (160) about frames transmitted through the network; a connection management unit (60) that logically disconnects a section between two devices by sending a command to the two devices; and a determination unit (70) that determines a section in which a failure has occurred based on a change in the statistical information when a section included in the network is logically disconnected.

[0150] [Configuration 2] 2. The communication device according to claim 1, wherein the connection management unit maintains a state in which the section in which the failure has occurred is isolated from the network.

[0151] [Configuration 3] 3. The communication device according to configuration 1 or 2, wherein the connection management unit isolates the section in which the failure is occurring from the network in accordance with a user operation.

[0152] [Configuration 4] The communication device according to any one of configurations 1 to 3, wherein the statistical information includes an error rate indicating a ratio of the number of lost frames and frames in which an error occurred to the number of frames transmitted from the communication device.

[0153] [Configuration 5] The communication device according to configuration 4, wherein the identification unit determines the possibility that the section is one in which a failure has occurred based on a degree to which the error occurrence rate is suppressed for each logically connected section.

[0154] [Configuration 6] 6. The communication device according to any one of configurations 1 to 5, wherein the identifying unit starts a process of identifying the section in which the failure has occurred when the statistical information satisfies a predetermined condition.

[0155] [Configuration 7] The communication device according to any one of configurations 1 to 6, wherein the connection management unit sequentially selects two adjacent devices, sends a command to close the ports to the two selected devices, and then sends a command to open the ports to the two selected devices.

[0156] [Configuration 8] 8. The communication device according to any one of configurations 1 to 7, further comprising a notification unit for notifying an outside party of the section in which the failure has occurred.

[0157] [Configuration 9] A communication control method executed by a communication device (100) connected to a network configured to circulate frames, at least a part of the network is made redundant, and one or more devices (200; 300) are connected to the network, the communication control method comprising: collecting statistical information about frames transmitted through the network (S2, S12); A step of logically disconnecting a section between the two devices by sending a command to the two devices (S8, S10); and identifying a section in which a failure has occurred based on a change in the statistical information when a section included in the network is logically disconnected (S14, S16).

[0158] [Configuration 10] A communication control program (1102) executed on a computer (100) connected to a network configured to circulate frames, at least a part of the network is made redundant, and one or more devices (200; 300) are connected to the network, and the communication control program is configured to: collecting statistical information about frames transmitted through the network (S2, S12); A step of logically disconnecting a section between the two devices by sending a command to the two devices (S8, S10); A communication control program that causes steps (S14, S16) to be executed to identify a section in which a failure has occurred based on a change in the statistical information when a section included in the network is logically disconnected.

[0159] <I. Advantages> The communication system according to the present embodiment can surely determine whether or not a failure has occurred in each section included in the network. Therefore, when any failure has occurred, the failure can be surely removed or the like. By executing a function capable of specifying and isolating such a failure, the stability of the redundant network can be maintained.

[0160] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Description of Reference Numerals

[0161] 1 Communication system, 20, 21, 22, 23, 24, 25, 26 Cable, 50 Collection module, 60 Connection management module, 70 Specific module, 100 PLC, 102, 202, 302, 402 Processor, 104, 204, 304, 404 Main memory, 110, 210, 310, 410 Storage, 112, 212 Field network controller, 114 Local bus controller, 116 Functional unit, 118, 228 Internal bus, 151, 152 Port, 160 Statistics, 200 Functional device, 206, 306 Control circuit, 220 Functional module, 251, 351 First port, 252, 352 Second port, 300 Relay device, 312 Field network interface, 353 Third port, 400 Support device, 406 Input section, 408 Display unit, 412, communication controller, 416, optical drive, 418, storage medium, 424, USB controller, 450, 470, user interface screen, 452, network configuration diagram, 454, highlighting, 456, separation mark, 458, dialog, 460, cursor, 462, contribution rate, 1102, system program, 1104, user program, 1122, network management module, 4102, OS, 4104, development program.

Claims

1. a communication unit connected to a network configured to circulate frames, at least a part of the network has redundant paths, and one or more devices are connected to the network; a collection unit for collecting statistical information about frames transmitted through the network; a connection management unit that logically disconnects a section between two devices by sending a command to the two devices, the frame being looped back at each of the two devices located on either side of the logically disconnected section, A communication device comprising: an identification unit that identifies a section in which a failure is occurring based on a change in the statistical information when a section included in the network is logically disconnected.

2. The communication device according to claim 1 , wherein the connection management unit maintains a state in which the section in which the failure has occurred is isolated from the network.

3. The communication device according to claim 1 , wherein the connection management unit isolates the section in which the failure has occurred from the network in accordance with a user operation.

4. The communication device according to any one of claims 1 to 3, wherein the statistical information includes an error rate indicating a ratio of the number of lost frames and frames in which an error occurred to the number of frames transmitted from the communication device.

5. The communication device according to claim 4 , wherein the identifying unit determines the possibility that the section is a section in which the failure has occurred based on a degree to which the error occurrence rate is suppressed for each logically connected section.

6. The communication device according to claim 1 , wherein the identifying unit initiates a process of identifying the section in which the failure has occurred when the statistical information satisfies a predetermined condition.

7. The communication device according to any one of claims 1 to 6, wherein the connection management unit sequentially selects two adjacent devices, transmits a command to close a port to the two selected devices, and then transmits a command to open a port to the two selected devices.

8. The communication device according to claim 1, further comprising a notification unit for notifying an outside party of the section in which the failure has occurred.

9. A communication control method executed by a communication device connected to a network configured to circulate frames, wherein at least a part of paths in the network is made redundant, and one or a plurality of devices are connected to the network, the communication control method comprising: collecting statistics about frames transmitted over said network; a step of logically disconnecting a section between two devices by sending a command to the two devices, the frame being folded back at each of the two devices located on both sides of the logically disconnected section; A communication control method comprising a step of identifying a section in which a failure has occurred based on a change in the statistical information when a section included in the network is logically disconnected.

10. A communication control program executed on a computer connected to a network configured to circulate frames, wherein at least a portion of the network is made redundant, and one or more devices are connected to the network, and the communication control program is configured to include: collecting statistics about frames transmitted over said network; and transmitting a command to the two devices to logically disconnect the section between the two devices, the frame being folded back at each of the two devices located on either side of the logically disconnected section. A communication control program that executes a step of identifying a section in which a failure has occurred based on a change in the statistical information when a section included in the network is logically disconnected.

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