Distributed control system

Abstract

To ensure the real time of control communication for continuous operation.SOLUTION: A distributed control system 01 includes a communication master station 0101 and a plurality of communication slave stations 0102 connected downstream from the communication master station, with the communication master station being the most upstream station. The communication master station and the communication slave stations are connected to each other directly or indirectly via communication lines, and each of the plurality of communication slave stations has a plurality of communication ports 0103 for communication. The plurality of communication ports includes, as communication port status types, active ports that are capable of performing communication and spare ports 01033 that are only connected and not used for communication. When the communication function of a first communication slave station included in the plurality of communication slave stations stops, a second communication slave station downstream of the first communication slave station changes the status of at least one of the plurality of communication ports of the second communication slave station and transmits, from the communication port, a communication path notification to change the communication path before the communication function of the first communication slave station stopped to another communication path.SELECTED DRAWING: Figure 3A

Description

[Technical Field]

[0001] The present disclosure relates to distributed control systems. [Background technology]

[0002] Currently, various network-based communication control technologies are in use. One example of this application is industrial equipment. Industrial equipment, such as biochemistry and immunoassay analyzers, typically uses electronic systems with analog transmission paths from multiple centralized control boards to control devices such as sensors and motors installed on the equipment. In recent years, to improve the efficiency of equipment design, manufacturing, and maintenance, distributed control systems have been adopted, which modularize and distribute control boards to reduce the amount of analog transmission paths and improve the equipment's control performance. To reduce equipment downtime, such distributed control systems often use redundant networks with multiple communication paths to ensure continued control communication even when equipment is partially broken or shut down for maintenance. A redundant network allows multiple communication paths between boards connected to the network, but failure to create appropriate communication paths can cause malfunctions. Furthermore, when a failure occurs, it is necessary to create a detour path that bypasses the broken part and continues communication using the remaining redundant paths.

[0003] As a means for solving this problem, a commonly known technology is to generate a communication path by having a communication master station send a communication packet for routing so that the packet is distributed throughout the network when a failure occurs in a redundant network. For example, Patent Document 1 discloses that a communication master station sends a routing packet, and the communication slave station that receives the packet forwards it from its own communication port, thereby distributing the packet to all available communication lines within the network. This is said to enable the generation of an optimal communication path based on the number of times the routing packet passes through the communication lines. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-146599 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the technology described in Patent Document 1, because communication between the communication master station and all communication slave stations that are not stopped is performed, communication slave stations that do not need to change their communication paths also need to generate communication paths. Therefore, in a distributed control system for devices that require continuous operation even for operable parts, there is contention between control communications between the communication master station and communication slave stations, and bandwidth pressure makes it difficult to guarantee real-time control communications.

[0006] In view of such circumstances, the present disclosure proposes a technique for ensuring real-time control communication for continuous operation in a distributed control system including a communication master station and multiple communication slave stations. [Means for solving the problem]

[0007] In order to solve the above problem, the present disclosure provides, as an example, a communication system including a communication master station and a plurality of communication slave stations connected in a downstream direction relative to the communication master station, with the communication master station being the most upstream station; the communication master station and the communication slave stations are connected to each other directly or indirectly via communication lines, and each of the plurality of communication slave stations has a plurality of communication ports for performing communication, and the plurality of communication ports include, as status types of the communication ports, valid ports that are available for communication and spare ports that are only connected and not used for communication; When the communication function of a first communication slave station included in a plurality of communication slave stations is stopped, a second communication slave station downstream of the first communication slave station: a process of changing the status of at least one of the plurality of communication ports of the second communication slave station; a process of transmitting a communication path notification from the communication port whose status has been changed to change the communication path that was used before the communication function of the first communication slave station was stopped to another communication path; We propose a distributed control system that executes the above.

[0008] Further features related to the present disclosure will become apparent from the description and accompanying drawings of this specification, and aspects of the present disclosure may be realized and realized by the elements and combinations of various elements and aspects set forth in the following detailed description and the appended claims. The descriptions herein are exemplary and illustrative only and are not intended to limit the scope or application of the present disclosure in any way. [Effects of the Invention]

[0009] The technology disclosed herein enables the creation of a communication path using only the communication of the downstream communication slave station when a communication slave station in a distributed control system is stopped. In addition, the sending and receiving of upstream port change notifications for creating a communication path does not constrict the control communication bandwidth between the communication master station and the communication slave station, so it is possible to maintain real-time control communication for continuous operation. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating an example of the configuration of a distributed control system 01 according to a first embodiment. [Figure 2] 10 is a flowchart illustrating a process in which a communication slave station 0102 changes an upstream port 01031 in each embodiment. [Figure 3A] FIG. 10 is a diagram illustrating a state after C4 of the communication slave station 0102 is stopped (intentionally stopped for maintenance) in the first embodiment. [Figure 3B] 10A and 10B are diagrams illustrating changes in the status of ports in each communication slave station 0102 when C4 of the communication slave station 0102 stops. [Figure 3C] 10 is a diagram for explaining an operation in which C5 of the communication slave station 0102 transmits a communication path change notification 0303 and receives the communication path change notification 0303 by itself. [Figure 3D] 10 is a diagram for explaining the operation of starting to change the upstream port again when C5 of the communication slave station 0102 receives the communication path change notification 0303 sent by itself. [Figure 4] This figure shows the state when C4 of a communication slave station 0102 stops due to a failure when each communication slave station 0102 of a distributed control system 01 according to Example 2 has a configuration that allows it to recognize a communication interruption with the communication master station 0101 using a watchdog timer. [Figure 5] FIG. 10 is a diagram illustrating a state after a communication path has been changed according to the second embodiment. [Figure 6] FIG. 10 is a diagram illustrating an example of the configuration of a distributed control system 06 according to a third embodiment. [Figure 7] FIG. 10 is a diagram showing a state when C4 of the communication slave station 0102 stops in the distributed control system 06. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present disclosure will be described below with reference to the accompanying drawings. The present embodiment relates to a technology for reconfiguring a communication path when a device in a network is stopped. [Example]

[0012] <Example of distributed control system configuration> 1 is a diagram illustrating an example of the configuration of a distributed control system 01 according to a first embodiment. The distributed control system 01 includes a communication master station 0101 and a plurality of communication slave stations 0102. The communication master station 0101 forms a network connected to the communication slave stations 0102 via communication lines. The communication slave stations 0102 have a plurality of communication ports 0103 and relay communications between the communication master station 0101 and each of the communication slave stations 0102.

[0013] One of the communication ports 0103 of the communication slave station 0102 is stored as the upstream port 01031 used for communication with the communication master station 0101. In a certain communication slave station 0102 or communication master station 0101, the communication port 0103 connected to the upstream port 01031 of the downstream communication slave station 0102 is stored as the downstream port 01032. A communication port 0103 that is not one of these and is connected is stored as a spare port 01033 (a port that is not currently relaying communication (does not form a communication path) and is simply connected). In communication from P1 of the communication master station 0101 to C2 of the communication slave station 0102, a communication packet is transferred via the downstream port 01032 of P1, the upstream port 01031 of C1, the downstream port 01032 of C1, and the upstream port 01031 of C2.

[0014] The communication master station (P1) 0101 and each communication slave station (C1 to C9) 0102 have communication functions and can be configured as a device having a processor such as a CPU or MPU, an ASIC, or an integrated circuit such as an FPGA.

[0015] <Creating a communication path> Next, a method for generating a communication path in the distributed control system 01 will be explained. First, consider the case where C4 of the communication slave station 0102 is intentionally stopped. At this time, upon receiving a stop command, C4 of the communication slave station 0102 transmits a stop notification 0301 to C5 and C7 of the communication slave stations 0102 directly below it. FIG. 2 is a flowchart for explaining the process by which the communication slave station 0102 changes the upstream port 01031 in each embodiment. Note that, since the flowchart is executed by loading a corresponding program, the processor, ASIC, or FPGA of the communication master station 0101 or the communication slave station 0102 is the subject of operation in each step. However, the following description will be given assuming that the communication master station 0101 or the communication slave station 0102 is the subject of operation.

[0016] The relevant communication slave station 0102 executes the processing according to the flowchart of Figure 2 when it receives a stop notification 0301 (for example, received by C7 from C4) or an upstream port change notification 0302 (for example, received by C8 from C7) at its upstream port 01031, or when it receives a communication path change notification 0303 sent by itself at any of its communication ports (see Figures 3B to 3D).

[0017] (i) Step S201 The communication slave station 0102 determines whether it has the backup port 01033. If the communication slave station 0102 has the backup port 01033 (YES in step S201: for example, C5 in FIG. 1), the process proceeds to step S202. On the other hand, if the communication slave station 0102 does not have the backup port 01033 (NO in step S201: for example, C7 in FIG. 1), the process proceeds to step S203.

[0018] (ii) Step S202 The communication slave station 0102 (C5 in Figure 1) sets one of the backup ports 01033 (for example, the backup port 01033 connected to C2 in Figure 1) as the upstream port 01031, and sends an upstream port change notification 0302 from that communication port 0103 to the upstream communication slave station 0102 or communication master station 0101 (for example, C5 in Figure 1 sends the upstream port change notification 0302 to C2).

[0019] (iii) Step S203 The communication slave station 0102 determines whether it has a downstream port 01032. If the communication slave station 0102 has a downstream port 01032 (YES in step S203: for example, C7 in FIG. 1), the process proceeds to step S204. On the other hand, if the communication slave station 0102 does not have a downstream port 01032 (NO in step S203: for example, C6 in FIG. 7), the process proceeds to step S205.

[0020] (iv) Step S204 The communication slave station 0102 (e.g., C7) having the downstream port 01032 designates any of the downstream ports 01032 as the upstream port 01031 (see FIGS. 1 and 3: changing the downstream port 01032 to the upstream port 01031), and transmits an upstream port change notification 0302 from its communication port 0103 (the upstream port 01031 of C7) to the nearest communication slave station 0102 (C8: the communication slave station downstream of C7 is changed to the upstream communication slave station).

[0021] (v) Step S205 The communication slave station 0102 not having the downstream port 01032 determines that a communication interruption has occurred.

[0022] <Appearance after C4 stops> FIG. 3A is a diagram showing the state after C4 of the communication slave station 0102 stops (intentionally stopped for maintenance) in the first embodiment. When receiving a stop command input by an operator, C4 of the communication slave station 0102 transmits a stop notification 0301 to C5 and C7 of the communication slave station 0102.

[0023] C7 of the communication slave station 0102 changes its downstream port 01032 to the upstream port 01031, and transmits an upstream port change notification 0302 to C8 of the communication slave station.

[0024] C8 of the communication slave station 0102 changes its spare port 01033 (C5 side) to the upstream port 01031, and transmits an upstream port change notification 0302 to C5 of the communication slave station 0102.

[0025] C5 of the communication slave station 0102 changes its spare port 01033 to the upstream port 01031 (upstream side: C2 side) and the downstream port 01032 (downstream side: C8 side), and transmits an upstream port change notification 0302 to C2. Also, C5 of the communication slave station 0102 transmits a communication path change notification 0303 from the upstream port 01031 to C5 of the communication slave station 0102.

[0026] C2 of the communication slave station 0102 changes its own backup port 01033 (C5 side) to downstream port 01032, receives the upstream port change notification 0302 and the communication path change notification 0303 from C5 of the communication slave station 0102, and transmits the communication path change notification 0303 from the upstream port 01031 (C1 side) to the communication master station 0101 via C1 of the communication slave station 0102.

[0027] By performing the above operations, new communication paths are generated from each communication slave station 0102 to P1 of the communication master station 0101, such as C6 → C5 → C2 → C1 → P1, C7 → C8 → C5 → C2 → C1 → P1, and C9 → C8 → C5 → C2 → C1 → P1.

[0028] <Example of operation when the communication slave station 0102 receives the communication path change notification 0303 that it sent> 3B to 3D are diagrams illustrating an example of an operation in which, after C4 of the communication slave station 0102 stops, the communication slave station 0102 receives the communication path change notification 0303 that it sent itself and starts changing the upstream port again. Here, an example is given in which C6 of the communication slave station 0102 changes the upstream port.

[0029] 3B is a diagram showing changes in the port status in each communication slave station 0102 when C4 of the communication slave station 0102 is stopped. As shown in FIG. 3B, when C4 of the communication slave station 0102 is stopped (for example, due to maintenance), C5 and C7 of the communication slave stations 0102 receive a stop notification 0301 from C4 of the communication slave station 0102. Upon receiving the stop notification 0301, C5 and C7 of the communication slave station 0102 each transmit an upstream port change notification 0302 to C8 of the communication slave station 0102. As can be seen from comparing FIG. 1 with FIG. 3B, at this time, the backup port 01033 (the backup port on the C8 side) of C5 of the communication slave station 0102 is changed to the upstream port 01031, and the downstream port 01032 (the downstream port on the C8 side) of C7 of the communication slave station 0102 is changed to the upstream port 01031. Then, C8 of the communication slave station 0102 sends an upstream port change notification 0302 to C9 of the communication slave station 0102. C9 of the communication slave station 0102 also sends an upstream port change notification 0302 to C6 of the communication slave station 0102. Looking at the state in which the necessary port change operation has been performed in each communication slave station 0102 (FIG. 3B), it can be seen that there is no communication slave station 0102 that is most upstream among C5, C6, C8, and C9 of the communication slave stations 0102. In other words, C8 is upstream of C5, C9 is upstream of C8, C6 is upstream of C9, and C5 is upstream of C6, so the upstream and downstream statuses of the communication slave stations 0102 are cyclical.

[0030] Fig. 3C is a diagram for explaining the operation in which C5 of the communication slave station 0102 transmits a communication path change notification 0303 and receives the communication path change notification 0303. In the state shown in Fig. 3B, when C5 of the communication slave station 0102 transmits the communication path change notification 0303 as shown in Fig. 3C, the communication path change notification 0303 is transmitted in the order of C8 → C9 → C6 → C5 of the communication slave station 0102. Therefore, C5 of the communication slave station 0102 receives the communication path change notification 0303 that it itself transmitted.

[0031] 3D is a diagram illustrating the operation of starting to change the upstream port again when C5 of the communication slave station 0102 receives the communication path change notification 0303 that it has sent. When C5 of the communication slave station 0102 receives the communication path change notification 0303 that it has sent, it changes the port connected to C6 of the communication slave station 0102, which is the sender of the communication path change notification 0303, from the downstream port 01032 to the backup port 01033 (at this time, C5 may be configured to send a backup port change notification (not shown) to C6). Furthermore, when C6 of the communication slave station 0102 receives the backup port change notification from C5 of the communication slave station 0102, or when a predetermined time has elapsed since sending the communication path change notification 0303 to C5 of the communication slave station 0102, it changes the upstream port 01031 (on the C5 side) to the backup port 01033. Then, C6 of the communication slave station 0102 changes the backup port on the C3 side of the communication slave station 0102 to the upstream port 01031, and transmits an upstream port change notification 0302 to C3 of the communication slave station 0102. In this state, C3 of the communication slave station 0102 is the communication slave station 0102 that is the most upstream of C3, C6, C5, C9, C8, and C7 of the communication slave stations 0102, and therefore transmits a communication path change notification 0303 to P1 of the communication master station 0101 via C of the communication slave station 0102 that is located upstream. This completes the change of the communication path caused by the stoppage of C4 of the communication slave station 0102.

[0032] <Summary of Example 1> According to the first embodiment, the operation of transmitting and receiving the upstream port change notification 0302 for generating a communication path for the communication slave station 0102 in the distributed control system 01 is not affected by the stoppage of C4 of the communication slave station 0102. Furthermore, the operation of transmitting and receiving the upstream port change notification 0302 does not conflict with the communication between C1, C2, and C3 of the communication slave station 0102 and P1 of the communication master station 0101. Therefore, it is possible to re-establish the communication path between the communication master station 0101 and the non-stopped communication slave station 0102 while continuing to control C1, C2, and C3 of the communication slave station 0102. [Example]

[0033] <Operations when communication disruption is recognized (detected)> 4 is a diagram showing a state when C4 of the communication slave station 0102 stops due to a failure when each communication slave station 0102 of the distributed control system 01 has a configuration capable of recognizing a communication interruption with the communication master station 0101 using a watchdog timer according to the second embodiment. When C4 of the communication slave station 0102 fails, C5 and C7 determine the communication interruption with the communication master station 0101 using the watchdog timer. C5 and C7 of the communication slave stations 0102 transmit a watchdog timer stop notification 0401 from their downstream ports so that the communication slave stations 0102 downstream of them (downstream communication slave stations: C6 for C5 and C8 for C7) do not detect the communication interruption due to the watchdog timer and start changing the communication path independently.

[0034] <Operation after changing communication path> FIG. 5 is a diagram illustrating a state after a change in the communication path according to the second embodiment. In the second embodiment, it is assumed that P1 of the communication master station 0101 and each communication slave station 0102 have a watchdog timer, and are configured to recognize a communication interruption when no communication is detected after a predetermined time has elapsed. Furthermore, P1 of the communication master station 0101 can recognize that each communication slave station 0102 has stopped by using the watchdog timer. P1 of the communication master station 0101 can recognize that it is unable to communicate with, for example, C4 of the communication slave station 0102 and the communication slave stations 0102 downstream of C4, and can thereby determine that a failure has occurred. Since P1 of the communication master station 0101 communicates with C4 of the communication slave station 0102 via C1 of the communication slave station 0102 (C1 relays the communication between P1 and C4), it can determine whether communication has been interrupted by receiving notification from C1 of the communication slave station 0102 that communication with C4 of the communication slave station 0102 has been interrupted, or by detecting that a communication response (an acknowledgement notification (Ack) from each communication slave station 0102) has not been returned.

[0035] When communication paths from C5, C6, C7, C8, and C9 of the communication slave stations 0102 to P1 of the communication master station 0101 are generated (reconfigured), communication with the communication master station 0101 is resumed. At this time, when P1 of the communication master station 0101 resumes communication with C5, C6, C7, C8, and C9 of the communication slave stations 0102, it transmits a watchdog timer restart command 0501 to each of the communication slave stations 0102 so that each of the communication slave stations 0102 can once again recognize the communication interruption.

[0036] <Fault detection without a watchdog timer> If P1 of the communication master station 0101 or each communication slave station 0102 does not have a watchdog timer, for example, the communication slave station 0102 (target communication slave station) can be configured to constantly send a constant signal to P1 of the communication master station 0101, so that P1 of the communication master station 0101 or a communication slave station 0102 located upstream of the communication slave station 0102 that transmits the signal can determine whether or not there is a fault in the target communication slave station. This allows the distributed control system 01 (including the distributed control system 06 according to Example 3) to be configured.

[0037] <Summary of Example 2> According to the second embodiment, each communication slave station 0102 in the distributed control system 01 can independently detect a communication interruption and can re-establish a communication path without using the stop notification 0301 shown in the first embodiment. Although the second embodiment describes the detection of a communication interruption using a watchdog timer, the second embodiment can also be applied to communication interruptions using other means. Other effects when the distributed control system 01 is applied are the same as those of the first embodiment. [Example]

[0038] <Examples of distributed control system configuration and operation> FIG. 6 is a diagram illustrating an example of the configuration of a distributed control system 06 according to a third embodiment. In the third embodiment, the communication slave station 0102 is configured to be able to output an alert 0601. FIG. 7 is a diagram illustrating a state when C4 of the communication slave station 0102 stops in the distributed control system 06. The C4 of the communication slave station 0102 can be stopped due to a failure as in the second embodiment, or it can be stopped intentionally during maintenance as in the first embodiment. These two cases will be described below.

[0039] (i) When C4 of communication slave station 0102 fails and stops When C4 of the communication slave station 0102 fails and stops, C5 of the communication slave station 0102 detects the stop of C4 of the communication slave station 0102 using a watchdog timer, as in the second embodiment. Then, C5 of the communication slave station 0102 transmits a watchdog timer stop notification 0401 to C6 of the communication slave station 0102. Furthermore, C5 of the communication slave station 0102 transmits an upstream port change notification 0302 to C6 of the communication slave station 0102, and the communication path is re-established between C5 and C6 of the communication slave station 0102. At this time, because C6 of the communication slave station 0102 does not have a backup port 01033 or a downstream port 01032, the process proceeds to step S205 in the flowchart of FIG. 2, and C6 of the communication slave station 0102 determines that communication has been interrupted. Then, C6 of the communication slave station 0102 notifies the user of the distributed control system 06 of the occurrence of communication disruption by outputting the communication disruption to the alert 0601.

[0040] (ii) When C4 of communication slave station 0102 is intentionally stopped Upon receiving a stop command from the operator (user), C4 of the communication slave station 0102 transmits a stop notification 0301 to C5 of the communication slave station 0102. Upon receiving the stop notification 0301, C5 of the communication slave station 0102, which does not have a backup port 01033 but has a downstream port 01032, changes the downstream port 01032 (the port on the C6 side) to the upstream port 01031, and transmits an upstream port change notification 0302 to C6 of the communication slave station 0102 (step S201 → step S203 → step S204 in FIG. 2).

[0041] On the other hand, when the stop notification 0301 is received from C5 of the communication slave station 0102, C6 of the communication slave station 0102 determines that communication has been interrupted because it does not have the backup port 01033 or the downstream port 01032 (step S201 → step S203 → step S205 in FIG. 2). Then, C6 of the communication slave station 0102 outputs the communication interruption to the alert 0601, thereby notifying the user of the distributed control system 06 of the occurrence of the communication interruption.

[0042] <Summary of Example 3> According to the third embodiment, each communication slave station 0102 in the distributed control system 06 can notify the user that it is impossible to re-establish a communication path with P1 of the communication master station 0101. This allows the user to understand that repairs are necessary, making it possible to reduce downtime of the distributed control system 06. Other effects when the distributed control system 01 is applied are the same as those of the first embodiment.

[0043] (i) The technical features of the present disclosure are not limited to the contents of the above-described first to third embodiments, but include various modifications. For example, each embodiment has been described in detail and specifically to clearly explain the technology of the present disclosure, and is not necessarily limited to those including all of the described configurations. Furthermore, it is also possible to replace part of the configuration of one embodiment with the configuration of another embodiment. Furthermore, it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is also possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0044] (ii) The functions of this embodiment and each example can also be realized by software program code. In this case, a storage medium on which the program code is recorded is provided to a system or device, and the computer (or CPU or MPU) of the system or device reads the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-mentioned embodiment, and the program code itself and the storage medium on which it is stored constitute the present disclosure. Examples of storage media for providing such program code include flexible disks, CD-ROMs, DVD-ROMs, hard disks, optical disks, magneto-optical disks, CD-Rs, magnetic tapes, non-volatile memory cards, and ROMs. Furthermore, the communication paths shown are those considered necessary for explanation, and do not necessarily represent all communication paths in products to which this distributed control system is applied.

[0045] In addition, an operating system (OS) running on a computer may perform some or all of the actual processing based on instructions in the program code, and the functions of the above-described embodiments may be realized by this processing. Furthermore, after the program code is read from a storage medium and written to a memory on a computer, a CPU of the computer may perform some or all of the actual processing based on instructions in the program code, and the functions of the above-described embodiments may be realized by this processing.

[0046] Furthermore, the program code of the software that realizes the functions of the embodiments and each example may be distributed via a network and stored in a storage means such as a hard disk or memory of the system or device, or in a storage medium such as a CD-RW or CD-R, so that when in use, the computer (or CPU or MPU) of the system or device reads and executes the program code stored in the storage means or storage medium.

[0047] The processes and techniques described herein are not inherently related to any specific device and can be implemented by a combination of components. Various types of general-purpose devices can also be added. A dedicated device may be constructed to perform the functions of this embodiment and each example. Various functions can also be formed by appropriately combining multiple components disclosed in this embodiment and each example. For example, some components may be omitted from all the components shown in the embodiment and each example, or components from different examples may be appropriately combined.

[0048] Although specific embodiments are described in this disclosure, they are intended to be illustrative and not limiting in all respects (to facilitate understanding of the technology of the present disclosure). Those skilled in the art will recognize that numerous combinations of hardware, software, and firmware are suitable for implementing the technology of the present disclosure. For example, the described software can be implemented in a wide variety of programming or scripting languages, such as assembler, C / C++, Perl, Shell, PHP, and Java (registered trademark). Furthermore, some or all of the above-described configurations, functions, processing means, etc. may be implemented in hardware, for example, by designing them as integrated circuits.

[0049] Furthermore, in the above-described embodiment, the control lines and information lines are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. All components may be interconnected.

[0050] In addition, other implementations of the present disclosure will be apparent to those skilled in the art from consideration of the present embodiments and examples. The specification and examples are exemplary only, with the scope and spirit of the present disclosure being indicated by the following claims. [Explanation of symbols]

[0051] 01, 06 Distributed Control System 0101 Communication master station 0102 Communication substation 0103 communication port 01031 Upstream port 01032 Downstream port 01033 Reserve port 0301 Stop notification 0302 Upstream port change notification 0303 Communication path change notification 0401 Watchdog timer stop notification 0501 Watchdog timer restart command 0601 Alert

Claims

1. A communications master station, the communication master station being the most upstream station; and a plurality of communication slave stations connected in a downstream direction relative to the communication master station, the communication master station and the communication slave stations are connected to each other directly or indirectly via a communication line; each of the plurality of communication slave stations has a plurality of communication ports for performing communication; the plurality of communication ports include, as status types of the communication ports, valid ports that are available for communication and spare ports that are only connected and not used for communication; When a communication function of a first communication slave station included in the plurality of communication slave stations is stopped, a second communication slave station downstream of the first communication slave station a process of changing the status of at least one communication port of the plurality of communication ports of the second communication slave station; a process of transmitting a communication path change notification from the communication port whose status has been changed, for changing the communication path that was used before the communication function of the first communication slave station was stopped to another communication path; A distributed control system that performs

2. In claim 1, A distributed control system in which, if there is a third communication substation that becomes an upstream communication substation of the second communication substation through the processing of changing the status of the communication port, the second communication substation sends a communication path change notification to the communication master station via the third communication substation.

3. In claim 2, a third communication substation, when receiving notification of a change in the status of the communication port from the second communication substation, maintaining the status of communication ports other than the communication port connected to the second communication substation without changing it;

4. In claim 2, the second communication slave station is connected to the third communication slave station via the backup port, The second communication slave station executes a process of changing the status of the spare port connected to the third communication slave station to the active port.

5. In claim 1, The valid ports include, as status types of the communication ports, an upstream port connected to an upstream communication slave station or a communication master station, and a downstream port connected to a downstream communication slave station; a second communication slave station, when changing the status of the communication port to the upstream port, if there is a spare port among its own communication ports, preferentially changes the spare port to the upstream port;

6. In claim 2, a fourth communication substation that is downstream of the first communication substation and different from the second communication substation executes a process to change the status of the communication port of the fourth communication substation so that a fifth communication substation that was downstream of the fourth communication substation before the communication function of the first communication substation was stopped is recognized as an upstream communication substation.

7. In claim 6, The valid ports include, as status types of the communication ports, an upstream port connected to an upstream communication slave station or a communication master station, and a downstream port connected to a downstream communication slave station; the fourth communication slave station transmits to the fifth communication slave station an upstream port change notification for changing a status of the downstream port of the fourth communication slave station to the upstream port; In response to the upstream port change notification, the fifth communication substation changes the upstream port connected to the fourth communication substation to the downstream port, and changes the status of one of its own communication ports that has never been changed to the upstream port to the upstream port.

8. In claim 6, the fifth communication slave station is connected to the second communication slave station via the backup port, A distributed control system in which the fifth communication substation executes a process to change the status of the backup port connected to the second communication substation to the active port, thereby generating a communication path from the communication master station to the fourth communication substation via the third communication substation, the second communication substation, and the fifth communication substation.

9. In claim 1, When the second communication slave station receives the communication path change notification transmitted by itself, the second communication slave station determines that the communication path change has failed, A distributed control system in which the second communication substation or at least one of the communication substations other than the second communication substation that received the communication path change notification again executes a process to change the status of at least one of its own communication ports.

10. In claim 1, In a distributed control system, the first communication substation responds to a communication function stop command input from outside by transmitting a notification of the stop of the communication function to the communication substations downstream of the first communication substation, thereby causing the communication substations downstream of the first communication substation to recognize the stop of the communication function of the first communication substation.

11. In claim 1, each of the plurality of communication slave stations includes a watchdog timer; The second communication slave station a process of detecting a stop of the communication function of the first communication slave station using the watchdog timer; a process of transmitting a watchdog timer stop notification to the communication slave station downstream of the second communication slave station, the watchdog timer stop notification instructing the communication slave station to stop the watchdog timer; A distributed control system that performs

12. In claim 11, when there is a third communication slave station that becomes an upstream communication slave station of the second communication slave station by the processing of changing the status of the communication port, the second communication slave station is connected to the third communication slave station via the backup port; the second communication slave station executes a process of changing the status of the backup port connected to the third communication slave station to the active port; a fourth communication slave station that is downstream of the first communication slave station and different from the second communication slave station executes a process of changing a status of the communication port of the fourth communication slave station so that a fifth communication slave station that was downstream of the fourth communication slave station before the communication function of the first communication slave station was stopped is recognized as an upstream communication slave station; the fifth communication slave station is connected to the second communication slave station via the backup port, the fifth communication slave station executes a process of changing the status of the backup port connected to the second communication slave station to the active port, thereby generating a new communication path; A distributed control system in which the communication master station performs a process of sending a timer restart command to the multiple communication slave stations other than the first communication slave station that are downstream of the communication master station on the new communication path, in order to make the watchdog timer operable again.

13. In claim 1, A distributed control system in which, if the processing of changing the status of the communication port does not result in a third communication substation being an upstream communication substation of the second communication substation, the communication substation connected to the second communication substation and downstream of the second communication substation determines that a communication interruption has occurred in which communication with the communication master station is impossible, and reports the communication interruption state.

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