Distributed control system and distributed control method

Abstract

The present invention addresses the problem of specifying an abnormality occurrence place in a network of a distributed control system over a plurality of layers.　In order to solve the problem, this distributed control system comprises: a plurality of master stations; a plurality of slave stations; hubs that connect master stations to each other; and a plurality of communication paths for connection between the master stations and the hubs, between the hubs, between the master stations and the slave stations, and between the slave stations, and is provided with a first network composed of the master stations and the hubs, and a second network composed of the master stations and the slave stations. An abnormality occurrence place of the first network is specified by sharing, between the master stations via the second network, communication state information including information relating to the master stations with which the master stations can communicate.

Description

Distributed control system and distributed control method

[0001] The present invention relates to a technique for identifying a location where an abnormality occurs in a network, particularly a distributed control network.

[0002] Currently, various communication control technologies using networks are being utilized. One application example of this communication technology is industrial equipment. In industrial equipment such as biochemical and immunoassay devices, it is common to use an electronic system having an analog transmission path from a plurality of centrally concentrated control boards to control devices such as sensors and motors mounted on the device.

[0003] In recent years, for the purpose of improving the efficiency of device design, manufacturing, and maintenance, a distributed control system has been applied to reduce the amount of analog transmission paths and improve the control performance of the device by modularizing and distributing control boards. When constructing a system including a plurality of industrial devices, the master stations of such a distributed control system are further connected by a network so that unified management is possible, and cooperation between devices is enabled by communication between the master stations. In such a distributed control system, in order to reduce device downtime, it is necessary to be able to identify the location where an abnormality occurs when an abnormality occurs in the network of the master station.

[0004] As a means for solving this, there is known a technique in which a monitoring device in a network automatically detects the path information of communication devices, holds it as management information, and determines the location where a failure occurs (the location where an abnormality occurs) from the management information when a failure occurs. Regarding this technique, for example, Patent Document 1 has been proposed. In Patent Document 1, the location where a network failure occurs is identified by defining the parent-child relationship of IP addresses.

[0005] Japanese Patent Application Laid-Open No. 2001-86117

[0006] However, in the technique described in Patent Document 1, although the location where an abnormality occurs closest to the monitoring device in the network can be identified, the operating state beyond that cannot be determined. In order to reduce the device downtime, it is necessary to comprehensively and specifically identify the location where an abnormality occurs. Therefore, in the present invention, the master station has an issue of identifying the location where an abnormality occurs in the network.

[0007] To solve the above problems, the present invention provides a distributed control system having a first network in which multiple master stations are connected to each other, and a second network in which multiple slave stations are connected to any of the multiple master stations. By sharing communication status information, which includes information on the master stations that each of the multiple master stations can communicate with, among the multiple master stations, the location of an anomaly in the first network is identified.

[0008] More specifically, the distributed control system comprises a plurality of master stations, a plurality of slave stations constituting a plurality of control ranges by the master stations, a first network in which the plurality of master stations are connected to each other, and a second network in which the plurality of slave stations are connected to each other and each slave station in the control range is connected to one of the plurality of master stations, wherein the plurality of master stations control the slave stations via the second network, each of the plurality of slave stations communicates with other slave stations connected to itself, and when an abnormality occurs in the first network, the first master station included in the plurality of master stations acquires first communication status information to determine which master stations can communicate with the first master station, the first master station receives second communication status information via the second network from the second master station included in the plurality of master stations to determine which master stations can communicate with the first master station, and the first master station compares the first communication status information and the second communication status information to identify the location of the abnormality in the first network.

[0009] Furthermore, the present invention also includes distributed control methods executed by a distributed control system, the devices that constitute a distributed control system, and combinations thereof.

[0010] According to the present invention, if a communication anomaly occurs in the network of the master station of a distributed control system, it is possible to identify the location of the anomaly. Further issues, configurations, and effects will be clarified by the following description of the embodiments.

[0011] A diagram showing an example configuration of the distributed control system in Example 1. A diagram showing what happens when the communication path between the master station and the hub in the first network in Example 1 fails. A flowchart showing the communication status information sharing process in Example 1. A diagram showing what happens when a hub in the first network in Example 1 fails. A diagram showing what happens when the communication path between hubs in the first network in Example 1 fails. A diagram showing what happens when the master station in the first network in Example 1 fails. A diagram showing an example configuration of the distributed control system in Example 2. A diagram showing what happens when a hub in the first network in Example 2 fails. A diagram showing what happens when multiple locations in the first network in Example 3 fail.

[0012] Embodiments of the present invention will be described below. In this embodiment, the focus is on a distributed control system composed of control ranges, which are groups consisting of a master station and a plurality of slave stations that are the targets of its control. In this distributed control system, each control range is provided in a distributed manner, and various operations are controlled.

[0013] Furthermore, multiple master stations are connected to each other via communication paths to form a first network. In this embodiment, hubs are connected to the first network, and the master stations are connected to each other via the hubs. Moreover, in this embodiment, multiple hubs are provided, and these multiple hubs are also connected to each other via communication. Thus, the first network consists of multiple master stations and multiple hubs connecting them.

[0014] Each master station, together with multiple slave stations it controls, constitutes a control range. Furthermore, each master station stores a master station address to identify other master stations. The master station uses this master station address to obtain communication status information of other master stations. The master station then uses its own communication status information and the communication status information of other master stations to identify the location of the abnormality in the first network. Here, an abnormality in this embodiment refers to a situation where communication becomes impossible, or a decrease in performance or function such as a reduction in communication speed, and includes various malfunctions and failures.

[0015] Furthermore, each master station is connected via a communication path to multiple slave stations that together constitute a control range, and controls them. In this way, multiple slave stations form a second network with the master station of the corresponding control range. Moreover, multiple slave stations are connected to each other via the second network. Here, the second network is connected not only to slave stations within the control range, but also to slave stations outside the control range. The connection of slave stations can be realized by a daisy-chain communication path or a branched communication path. Thus, in this embodiment, the distributed control system is composed of the first network, the second network, and the master stations, slave stations, and hubs that constitute them. In this way, in this embodiment, the distributed control network is composed of multiple layers, such as each network or each group of devices.

[0016] In this embodiment, if an anomaly occurs in the first network of the distributed control system, the master station acquires first communication status information, which includes its own information. The master station also receives second communication status information, which includes information about other master stations with which it can communicate. More preferably, the second communication status information is communicated via the second network.

[0017] Then, the master station compares the acquired first and second communication status information to identify the location of the anomaly in the first network. In this comparison, the location of the anomaly is identified based on which of the predetermined patterns the communication status at each master station corresponds to.

[0018] In this embodiment, each master station collects the first and second communication status information, compares them, and identifies the location of the anomaly. The master station of interest can be referred to as the first master station. In the embodiments described later, master station P1 corresponds to the first master station. In this embodiment, master stations other than the first master station are referred to as second master stations. In the embodiments described later, master stations P2 to P6 correspond to the second master stations.

[0019] Furthermore, specific examples including this pattern will be described in the following embodiments. The embodiments of the present invention will be described below with reference to the drawings.

[0020] Figure 1 shows an example of the configuration of the distributed control system 1 in this embodiment. In Figure 1, the distributed control system 1 comprises a plurality of master stations P1 to P6, a plurality of slave stations C1 to C13, and hubs H1 to H3.

[0021] Furthermore, the first control range is formed by the master station P1 and slave stations C1 to C2. Similarly, the second control range is formed by the master station P2 and slave stations C3 to C4. In this way, Figure 1 shows that the control ranges up to the sixth control range are formed by the master station P6 and slave stations C11 to C13. In the following explanation, when a master station is common to master stations P1 to P6, it will be referred to as master station P. Similarly, it may also be referred to as slave station C or hub H.

[0022] Furthermore, each of the master stations P1 to P6 is connected to each other via hubs H1 to H3 and communication channels N1 to N8, forming a first network. In addition, a second network is formed by communication channels connecting each of the master stations P1 to P6 to slave stations C1, C3, C5, C7, C9, and C11, and by communication channels (dotted lines) connecting slave stations C1 to C13 to each other.

[0023] Furthermore, master stations P1 to P6 control slave stations C1 to C13, which are within their respective control ranges. For example, master station P1 controls slave stations C1 and C2, and master station P6 controls slave stations C11, C12, and C13. To this end, slave station C relays communication between master station P and other slave stations C.

[0024] Furthermore, slave station C can share information with other adjacent slave stations C. For example, information can be shared, or communicated, between slave stations C1 and C2 that belong to the same control range, and between slave stations C2 and C3 that belong to different control ranges. In addition, hub H relays communication between master stations P, enabling cooperation between master stations P.

[0025] Next, a method for identifying the location of an anomaly in the distributed control system 1 will be explained. Figure 2 shows a situation in this embodiment where the communication path N1 between the master station and the hub in the first network has failed. This failure is an example of an anomaly. Master station P1 collects communication status information 2 via the first network, which includes identifying other master stations P with which it can communicate. The collection of this communication status information 2 includes obtaining first communication status information 2A indicating the communication status of master station P1 itself and receiving second communication status information 2B indicating the communication status of other master stations P2 to P6.

[0026] Figure 2 shows the collected communication status information 2. Communication status information 2 indicates whether communication is possible from base station P to each of the other base stations P. First, base station P1 becomes unable to communicate with the other base stations P2 to P6. Therefore, the first communication status information 2A shows "○" (communication possible) for P1 and "×" (communication impossible) for the other base stations P2 to P6. In this embodiment and the embodiments described later, "communication impossible" includes not only cases where it has been confirmed that communication is impossible, but also cases where the communication status is unknown.

[0027] In this embodiment, and in embodiments 2 and 3 described later, the communication status information 2 records whether communication with each base station P is possible or impossible. However, it is also possible to record either a base station P that is possible to communicate with or a base station P that is not. Thus, the communication status information 2 is information that identifies a base station that is possible to communicate with from the base station P in question.

[0028] Furthermore, in communication status information 2, the master station address, which is the address of master station P, is used to identify master station P. In this case, each master station address will be associated with whether the corresponding master station P is able to communicate or not, and this will be recorded. Alternatively, communication status information 2 will record the master station addresses of master station P that are able to communicate or master station P that are not able to communicate.

[0029] On the other hand, the other master stations P2 to P6 will each be unable to communicate only with master station P1. Therefore, the second communication status information 2B will show "×" for P1 and "〇" for all the remaining master stations P2 to P6. Each master station P1 to P6 will share this communication status information 2 via the second network.

[0030] Next, the process for sharing communication status information 2 will be described. Figure 3 is a flowchart showing the communication status information sharing process in this embodiment. This is merely one example in this embodiment, and the communication status information sharing process of the present invention is not limited to this. In this embodiment, each master station P shares the communication status information 2, but it is sufficient for at least one master station P1 to collect the communication status information 2.

[0031] In the following steps in Figure 3, at step S301, the master station P determines whether there are any master stations P that cannot communicate via the first network. If there are any master stations P that cannot communicate (YES), the process proceeds to step S302. If there are no master stations P that cannot communicate (NO), the determination in step S301 is repeated. In Embodiment 1, each master station P performs the sharing process in parallel, but it is sufficient for at least one of the master stations P to perform the sharing process.

[0032] Furthermore, in step S302, the master station P uses the collected communication status information 2 to determine whether it is impossible to communicate with all other master stations P. For example, in the example in Figure 2, master station P1 determines that it is impossible to communicate with all other master stations P because the first communication status information 2A indicates that P2 to P6 are unable to communicate.

[0033] If this determination indicates that communication with other base stations P is impossible (YES), the process proceeds to step S304. If communication with all other base stations P is possible (NO), the process proceeds to step S303.

[0034] Furthermore, in step S303, the master station P determines whether communication status information 2 has not been shared by another master station P within a certain period of time. In other words, the master station P determines whether a certain period of time has elapsed without receiving the second communication status information 2B from another master station P. Here, the certain period of time is an example of a predetermined time, and is the time from the moment when YES was determined in step S301.

[0035] If the result of this determination is that sharing does not occur (YES), the process proceeds to step S304. If sharing occurs (NO), this flow terminates. Also, in step S304, the master station P will share the communication status information 2 via the second network.

[0036] Now, let's explain the details of step S304. First, the master station P shares the communication status information 2. At this time, the communication status information 2 transmitted from the master station P1 to the slave station C is shared within the second network through information sharing among the slave stations C.

[0037] Substation C transmits its contents to the master station P that controls it. As a result, the communication status information 2 is shared between the master station P that sent the communication status information 2 and the other master stations P. Note that if the communication status information 2 has been shared by one of the master stations P, the other master stations P may proceed to step S305 without sharing the communication status information 2.

[0038] Furthermore, in step S305, the master station P compares the collected communication status information 2, that is, the first communication status information 2A and the second communication status information 2B.

[0039] Then, in step S306, the master station P identifies the location of the anomaly in the first network according to the pattern determined to be applicable in step S305. The details of this will be explained below using the example of communication status information 2 shown in Figure 2.

[0040] When the communication status information 2 is checked, it is found that communication is impossible only between the master station P1 and the other master stations P2 to P6. From this, master station P1 can identify that the hub H1 or communication channel N1 between master station P1 and a subset of the first network consisting of master stations P2 to P6, hubs H1 to H3, and communication channels N2 to N8 of the first network is a candidate for the location of the anomaly. Since only communication channel N1 exists between this subset and P1, master station P1 can identify communication channel N1 as the location of the anomaly. Here, checking the communication status information 2 refers to checking the first communication status information 2A and the second communication status information 2B (including 2B-1 to 2B-3 described later). This checking includes, for example, determining which of the pre-prepared patterns these correspond to.

[0041] Incidentally, in step S306, the location where an abnormality has occurred may be specified based on which of the patterns prepared in advance as follows. First, the master station P1 indicates a pattern in which only the master station P1 can communicate with itself, and the other master stations P2 to P6 cannot communicate with the master station P1. Therefore, in the first network, the communication path N1, which is a location specialized for the master station P1, is regarded as the location where an abnormality has occurred. Note that this pattern is stored in the master station P.

[0042] Further, considering the second communication status information 2B, although there is a possibility that the master station P1 itself is determined to be the location where an abnormality has occurred, since the master station P1 itself can communicate in the first communication status information 2A, it is excluded that the master station P1 is the location where an abnormality has occurred.

[0043] As described above, in the example of FIG. 2, when the master station P1 is unable to communicate only with each of the other master stations P2 to P6 as a result of collating the communication status information 2, the communication path N1 between the master station P1 and the hub H1 connected to this master station P1 is specified as the location where an abnormality has occurred.

[0044] This concludes this flow. Note that steps S302 and S303 may be skipped, and the process may transition from step S301 to step S304.

[0045] Next, an example of a case where an abnormality has occurred at a location different from that in FIG. 2 will be described. FIG. 4 is a diagram showing a state in which the hub H1 has failed in the first network in the first embodiment. The master station P collects the communication status information 2 for discriminating the master stations with which it can communicate via the first network. FIG. 4 shows the first communication status information 2A, the second communication status information 2B-1, and the second communication status information 2B-2, which are the communication status information 2 when the hub H1 has failed.

[0046] In this first communication status information 2A, since the master station P1 cannot communicate with the other master stations P2 to P6, the first communication status information 2A does not include any master stations that can communicate. Similarly, for the master station P2, since it cannot communicate with the other master stations P1, P3 to P6, the second communication status information 2B-1 does not include any master stations that can communicate.

[0047] Further, in the second communication state information 2B-2, the master stations P3 to P6 cannot communicate only with P1 and P2. That is, the second communication state information 2B-2 includes the master stations P3 to P6 as the communicable master stations. Thus, since the master stations P1 and P2 cannot communicate with all the other master stations P3 to P6, the communication state information 2 is shared via the second network.

[0048] Further, since the communication state information 2 from the master stations P1 and P2 is shared by the master stations P3 to P6, the master stations P1 and P2 may identify the location of the occurrence of an abnormality without sharing the communication state information 2. The master station P, preferably the master stations P3 to P6, collates the collected communication state information 2. As a result, since the master station P cannot communicate between the master stations P in the combination via the hub H1, it can be identified that the hub H1 is the location of the occurrence of an abnormality.

[0049] As described above, in the example of FIG. 4, as a result of collating the communication state information 2, if the master station P1 and the adjacent master station P2 can communicate with each other and the master stations P1 and P2 cannot communicate with the other master stations P3 to P6, the hub H1 connected to the master stations P1 and P2 is identified as the location of the occurrence of an abnormality.

[0050] Next, an example in the case where an abnormality occurs at a location further different from FIGS. 2 and 4 will be described. FIG. 5 is a diagram showing a state where the communication path N7 in the first network in the first embodiment has failed. For any master station P, there is another master station P that can communicate via the first network. Therefore, a certain period of time will pass without the master station P sharing the communication state information 2 (see step S303). Thereafter, all the master stations P share the communication state information 2 via the second network, that is, collect the communication state information 2. Then, the master station P collates the collected communication state information 2 (the first communication state information 2A, the second communication state information 2B-1, 2B-2). As a result, since the master stations P1, P2 passing between the hubs H1 and H2 and the master stations P3, P4 cannot communicate, it can be identified that the communication path N7 of the first network is the location of the occurrence of an abnormality.

[0051] As described above, in the example shown in Figure 5, if, as a result of checking the communication status information 2, base station P1 determines that communication is possible between base station P1 and the adjacent base station P2, but base stations P1 and P2 are unable to communicate with other base stations P3 to P6, then the communication path N7 provided between base stations P1 and P2 is identified as the location of the abnormality.

[0052] Next, we will explain an example of what happens when an anomaly occurs at yet another location. Figure 6 shows the situation when the master station P1 in the first network in Embodiment 1 fails. Master stations P2 to P6 will not receive communication status information 2 from the other master stations P for a certain period of time (see step S303). In other words, master station P1 identifies itself as the location of the anomaly, based on the result of comparing the communication status information, as a master station P1 whose communication status is impossible. This process may be performed by at least one of the other master stations P2 to P6. Then, master station P shares the communication status information 2 via the second network, that is, it collects the communication status information 2.

[0053] In response, the master station P checks the collected communication status information 2. As a result, since the communication status information 2 for master station P1 is unknown or otherwise unavailable, master station P1 can be identified as the location of the malfunction. Note that in Figure 6, the first communication status information 2A was not acquired because master station P1 malfunctioned. However, information where each master station's item is marked as "unavailable" ("×") may be used as the first communication status information 2A.

[0054] According to this embodiment, the location of an anomaly in the first network of the distributed control system 1 can be identified. In this embodiment, by utilizing the fact that communication between the master station P and the slave station C and information sharing between adjacent slave stations C are possible, communication status information 2 is shared between master stations P, so slave stations C do not need to separately prepare functions for communication between master stations P, such as routing tables. Furthermore, since communication status information 2 is shared via the second network, by improving the redundancy of the second network, such as by increasing the number of communication paths in the second network that facilitates communication between slave stations C, it is possible to more reliably identify the location of the anomaly.

[0055] In Example 2, the location of an anomaly is identified in a distributed control system 1 having hierarchically connected hubs H. In Example 1, the hubs H are connected in parallel, but in this example, lower-level hubs H4 and H5 are provided in a portion of the space between hub H and the master station P. In this example, communication status information 2 is used to identify the master station P and hub H that can communicate. The details are described below.

[0056] Figure 7 shows an example of the configuration of the distributed control system 1 in this embodiment. In this embodiment, the first network is configured such that the master station P1 connects to all other master stations P2 to P5 via a plurality of hubs H1 to H5.

[0057] In this embodiment, compared to Embodiment 1, a hub H4 is provided between hub H1 and master station P1. Furthermore, a hub H5 is provided between hub H2 and master station P2. In this embodiment, communication status information 2 is used, which also includes information on hubs H that each master station P can communicate with. The communication status information 2 in this embodiment is information that identifies the master stations and hubs H that can communicate with the given master station P. The communication status information 2 in this embodiment can also use the addresses of the master stations P and hubs H, i.e., the master station address and the hub address, to identify the master stations P and hubs H. Also, as in Embodiment 1, the communication status information 2 may record whether communication is possible or impossible with each master station P and each hub H, or it may record either the master stations P and hubs H that can communicate or the master stations P and hubs H that cannot communicate.

[0058] Next, the method for identifying the location of an anomaly in the distributed control system 1 in this embodiment will be explained. Figure 8 shows a situation in which hub H1 in the first network in this embodiment has failed. The master station P collects communication status information 2 via the first network to determine which master stations P and hubs H it can communicate with. This communication status information 2 includes first communication status information 2A and second communication status information 2B, as shown in Figure 8.

[0059] Master station P1 can communicate only with hub H4. Therefore, the first communication status information 2A indicates that master station P1 and hub H4 can communicate. Master stations P2 to P5 can communicate with hubs H2, H3, and H5. Therefore, the second communication status information 2B indicates that master stations P2 to P5 can communicate with hubs H2, H3, and H5.

[0060] In this embodiment, we assume that all master stations P share communication status information 2 via a second network. Then, the master station P compares the first communication status information 2A and the second communication status information 2B and determines that all master stations P are unable to communicate with hub H1. As a result, the master station P identifies hub H1 as the location of the malfunction. In this embodiment, the master station P1 identifies hub H1, which shows that communication is impossible according to the first communication status information 2A and the second communication status information 2B, as the location of the malfunction based on the comparison of communication status information 2.

[0061] According to this embodiment, by determining which hubs H each master station P can communicate with based on the communication status information 2, it is possible to pinpoint the location of the abnormality in more detail. Furthermore, the effects of applying the distributed control system 1 are the same as in Embodiment 1.

[0062] Next, we will describe Example 3. In Example 3, we will describe how to identify the location of an anomaly when multiple failures occur in a distributed control system 1 with the same configuration as in Example 2. Figure 9 shows the situation when multiple locations in the first network, including hub H1, communication paths N5 and N9, have failed in this example. In this example, as in Example 2, communication status information 2 is used to determine the communication status of the master station P and hub H.

[0063] The method for identifying the location of an anomaly in the distributed control system 1 in this embodiment will be explained below with reference to Figure 9. The master station P collects communication status information 2 via the first network to determine which master stations P and hubs H it can communicate with. As shown in Figure 9, the communication status information 2 in this embodiment includes the first communication status information 2A, the second communication status information 2B-1, the second communication status information 2B-2, and the second communication status information 2B-3. The reason why there are multiple second communication status information 2Bs is that, as in Figure 4, the master stations P and hubs H that it can communicate with differ depending on the master station P.

[0064] First, since base station P1 can communicate only with hub H4, the first communication status information 2A indicates that base station P1 can communicate with hub H4. Also, since base station P2 can communicate only with hub H5, the second communication status information 2B-1 indicates that base station P2 can communicate with hub H5.

[0065] Furthermore, master stations P3 and P4 can communicate with hubs H2 and H3. Therefore, the second communication status information 2B-3 indicates that master stations P3 and P4 can communicate with hubs H2 and H3. Moreover, master station P5 cannot communicate with any of the master stations P or hubs H. Therefore, the second communication status information 2B-3 indicates that only master station P5 can communicate. This communication status information 2 will be shared among each master station P via the second network.

[0066] Then, the master station P1, which has shared the communication status information 2, checks the shared communication status information 2 and normally identifies the location where the anomaly occurred. For this reason, first, communication between master station P1 and the other master stations P2 to P5 is impossible. From this, it can be determined that a communication anomaly has occurred between master station P1 and a first subset of the network from master stations P2 to P5 that are able to communicate with each other. Here, master station P1 is able to communicate with hub H4, and master stations P3, P4, hubs H2, and H3 are able to communicate. From this, master station P1 can identify hub H1, which is located between them, as the location where the anomaly occurred.

[0067] Next, since communication between base station P2 and the other base stations P is impossible, it can be determined that a communication anomaly has occurred between base station P2 and a subset of the first network (among base stations P1, P3-P5) that are able to communicate with each other. Here, base station P2 is able to communicate with hub H5, and base stations P3, P4, and hubs H2 and H3 are able to communicate. From this, it can be identified that the communication path N5 of the first network located between them is the location where the anomaly occurred.

[0068] Next, since communication between base station P5 and the other base stations P is impossible, it can be determined that a communication anomaly has occurred between base station P5 and the first network subset of base stations P1 to P4 that are able to communicate with each other.

[0069] Here, master stations P3 and P4, and hubs H2 and H3 are able to communicate. From this, master station P can identify that master station P5 and the first network communication path N9 located between them are the locations where the abnormality occurred.

[0070] According to this embodiment, even if multiple communication anomalies occur in the first network, it is possible to narrow down the location of each anomaly by comparing the communication status information 2. Furthermore, the effects of applying the distributed control system 1 are the same as in Embodiments 1 and 2.

[0071] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. The embodiments described above are explained in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those having all the configurations described.

[0072] Here, we will describe some typical modifications. First, in Modification 1, the matching and identification of the location of the anomaly in steps S305 and S306 are determined by determining which of the communication status information 2 shown in each embodiment corresponds to. For this purpose, the master station P stores the communication status information 2 shown in Figures 2, 4, 5, 6, 8, and 9 as patterns and determines which of the collected communication status information 2 corresponds to. Then, the master station P identifies the location of the anomaly according to the corresponding pattern. This identification method is as shown in each embodiment.

[0073] Next, Modification 2 utilizes the identified location of the anomaly. Modification 2 includes (1) routing processing in the distributed control system 1, (2) notification and display to the management device, and (3) output by the master station P.

[0074] First, let's explain (1). When the master station P communicates with other master stations P, slave stations C, or hub H, it identifies a communication route that avoids the identified location of the anomaly and communicates using this route. Alternatively, the master station P may notify other master stations P, slave stations C, or hub H of the identified location of the anomaly, and these recipients may then identify a communication route that avoids the location of the anomaly.

[0075] Next, (2) will be explained. As a prerequisite for (2), a management device for managing the distributed control system 1 is connected to the distributed control system 1. The management device can be implemented as a computer and receives notifications of abnormal locations identified from the master station P.

[0076] The management device then displays the location of the detected anomaly. Alternatively, the management device may, as in (1), identify a communication route that avoids the anomaly location and notify each device in the distributed control system 1.

[0077] Finally, let's explain (3). As a prerequisite for (3), the master station P is equipped with a display device. Alternatively, the master station P is connected to a terminal device that can be implemented using a computer, such as a tablet terminal. The display device or terminal device then displays the location of the specific malfunction. As a result, the user can identify the location of the malfunction and take appropriate action, such as repair. Note that (1) to (3) may be implemented in combination.

[0078] Next, in the third modification, at least one of the following conditions is used as the starting condition for the processing flow in Figure 3 by each master station P: (1) Notification of the first communication status information 2A, which is its own communication status information, to other master stations P; (2) Use of the communication status information 2 (for example, if at least one master station P and hub H are unable to communicate, processing is started); (3) Completion of collection of communication status information 2 at all master stations P.

[0079] Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0080] Furthermore, each of the above configurations, functions, and processing means may be implemented in hardware, either partially or entirely, by designing them as integrated circuits, for example. Alternatively, each of the above configurations and functions may be implemented in software by a processor interpreting and executing programs that implement each function. Information such as programs, tables, and files that implement each function can be stored in recording devices such as memory, hard disks, SSDs (Solid State Drives), or recording media such as IC cards, SD cards (SD is a registered trademark), or DVDs (registered trademark). In addition, the communication channels shown are those deemed necessary for explanation purposes and do not necessarily represent all communication channels N in products to which this distributed control system 1 is applied.

[0081] 1. Distributed control system 2. Communication status information 2A. First communication status information 2B. Second communication status information P1-P6 Master station C1-C13 Slave station H1-H5 Hub N1-N9 Communication channel

Claims

1. A distributed control system comprising: a plurality of master stations; a plurality of slave stations constituting a plurality of control ranges by the master stations; a first network to which the plurality of master stations are connected to each other; and a second network to which the plurality of slave stations are connected to each other and each slave station in the control range is connected to one of the plurality of master stations, wherein the plurality of master stations control the slave stations via the second network; each of the plurality of slave stations communicates with other slave stations connected to itself; when an abnormality occurs in the first network, the first master station included in the plurality of master stations acquires first communication status information to determine which master stations can communicate with the first master station; the first master station receives second communication status information to determine which master stations can communicate with the plurality of master stations via the second network; and the first master station compares the first communication status information and the second communication status information to identify the location of the abnormality in the first network.

2. A distributed control system according to claim 1, wherein the second master station is a plurality of master stations excluding the first master station, and the first master station is a distributed control system that receives the second communication status information via the second network.

3. A distributed control system according to claim 2, wherein the first network is a distributed control system in which the plurality of master stations are connected to each other via a plurality of hubs.

4. A distributed control system according to claim 3, wherein, if the first master station finds, as a result of the verification, that communication is impossible only between the first master station and the second master station, the first master station identifies the communication path between the first master station and the hub connected to it as the location of the abnormality.

5. A distributed control system according to claim 3, wherein, as a result of the verification, the first master station identifies a hub connected to the first master station and one of the second master stations as the location of the abnormality if, as a result of the verification, the first master station and one of the second master stations are each able to communicate with each other, and the first master station and one of the second master stations are unable to communicate with other master stations included in the second master station.

6. A distributed control system according to claim 3, wherein, as a result of the verification, the first master station is able to communicate with one of the second master stations, and if the first master station and one of the second master stations are unable to communicate with other master stations included in the second master station, the distributed control system identifies the communication path provided between the first master station and one of the second master stations as the location of the abnormality.

7. A distributed control system according to claim 3, wherein the first master station identifies a master station whose communication status is impossible as a result of the verification as the location of the abnormality.

8. A distributed control system according to claim 3, wherein the first communication status information and the second communication status information further determine which hubs are capable of communication.

9. A distributed control system according to claim 6, wherein the first master station identifies a hub that, as a result of the verification, indicates that the first communication status information and the second communication status information are unable to communicate as the location of the abnormality.

10. A distributed control method to be executed by a distributed control system having a plurality of master stations, a plurality of slave stations constituting a plurality of control ranges by the master stations, a first network to which the plurality of master stations are connected to each other, and a second network to which the plurality of slave stations are connected to each other and each slave station in the control range is connected to one of the plurality of master stations, wherein the plurality of master stations control the slave stations via the second network, each of the plurality of slave stations communicates with other slave stations connected to itself, if an abnormality occurs in the first network, the first master station included in the plurality of master stations acquires first communication status information to determine which master stations can communicate with the first master station, the first master station receives second communication status information to determine which master stations can communicate with the plurality of master stations via the second network, and the first master station compares the first communication status information and the second communication status information to identify the location of the abnormality in the first network.

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