Distributed control system

Abstract

Provided is a distributed control system capable of dynamically changing a control range of a communication master station. A distributed control system according to the present disclosure is provided with a plurality of communication master stations, a plurality of communication slave stations, and a plurality of communication paths. Each communication master station: has a master station address for distinguishing the communication master station from the other communication master stations; controls at least one communication slave station; and allocates to each communication slave station controlled by the communication master station a slave station address for distinguishing the communication slave station. Each communication master station and each communication slave station controlled by the communication master station communicate with each other via a control communication path by means of a packet including the slave station address without including the master station address. Each communication slave station: has the slave station address allocated by the communication master station that controls the communication slave station; shares control information with other directly connected communication slave stations; executes processing for recognizing a control range boundary of the communication master station by sharing information of the master station address of the communication slave station that controls the communication slave station with the other communication slave stations directly connected to the communication slave station; and suppresses unnecessary communication at the control range boundary.

Description

Distributed Control System

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

[0002] Currently, various network-based communication technologies are in use. One example of the application of these communication technologies is industrial equipment. Industrial equipment such as biochemical and immunological analyzers generally uses electronic systems with analog transmission paths from multiple centralized control boards to control devices such as sensors and motors installed in the equipment.

[0003] In recent years, to improve the efficiency of equipment design, manufacturing, and maintenance, distributed control systems have been adopted, which reduce the number of analog transmission lines and improve equipment control performance by modularizing and distributing control boards. In such distributed control systems, a single communication master station controls input / output communications with other control boards as communication slave stations, or the control boards acting as communication slave stations communicate directly with each other to share necessary information, or both. Even if some communication slave stations are down due to a failure or maintenance, a distributed control system can continue to control the remaining communication slave stations, potentially reducing downtime for equipment that uses the system. When a communication master station controls input / output communications, the trade-off between control cycles and communication volume limits the number of communication slave stations that a single communication master station can control. Therefore, distributed control systems typically use multiple communication master stations. However, in distributed control systems where communication slave stations communicate directly with each other to share information, communication slave stations controlled by different communication master stations must also be connected to each other. In this case, it is necessary to prevent control commands sent by multiple communication master stations from interfering with each other and causing malfunctions.

[0004] As a means for solving this problem, a technique is known in which a gateway is provided at the boundary of the control range of a communication master station within a network, and the gateway selects packets to be forwarded to prevent malfunctions.Patent Document 1 discloses a technique for smoothly performing communication between networks by managing gateways via pseudo nodes within the network.

[0005] JP 2013-102338 A

[0006] However, in the technology described in Patent Document 1, the gateway is installed in a fixed location, so when applied to a distributed control system, the control range of the communication master station is limited. In this case, when only a portion of the distributed control system is stopped due to a failure or maintenance, depending on the stopped portion, communication with the remaining portion cannot be performed, making it impossible to control. This makes it difficult to continue operating the equipment to which the system is applied.

[0007] Therefore, the present disclosure provides a distributed control system that can dynamically change the control range of a communication master station.

[0008] In order to solve the above-mentioned problems, the present disclosure provides a distributed control system including a plurality of communication master stations, a plurality of communication slave stations, and a plurality of communication paths connecting the communication master stations with each other, between the communication master stations and the communication slave stations, and connecting the communication slave stations with each other, wherein a first network is configured by connecting the communication master stations with each other via the communication paths, all of the communication slave stations are connected via the communication paths, and a second network is configured by connecting the communication master station with at least one of the communication slave stations directly connected thereto, and the second network has at least one control communication path including the communication master station and one or more of the communication slave stations controlled by the communication master station, and the communication master station has a parent communication path for distinguishing it from other communication master stations. a communication master station and a communication slave station controlled by the communication master station, the communication master station having a station address and controlling at least one of the communication slave stations, and assigning a slave station address to the communication slave station for identifying the communication slave station that it controls; the communication master station and the communication slave station controlled by the communication master station communicate with each other via the control communication path using packets that do not include the master station address but include the slave station address; the communication slave station has the slave station address assigned by the communication master station that controls it, and shares control information with other communication slave stations that are directly connected to it, and by sharing information about the master station address of the communication master station that controls it with other communication slave stations that are directly connected to it, it executes a process to recognize the control range boundary of the communication master station and suppresses unnecessary communication at the control range boundary.

[0009] Further features related to the present disclosure will become apparent from the description of this specification and the accompanying drawings. Also, aspects of the present disclosure are achieved and realized by the elements and combinations of various elements and the aspects of the following detailed description and the appended claims. The description of this specification is merely exemplary and does not limit the scope or application of the claims of the present disclosure in any way.

[0010] According to the technology of the present disclosure, it is possible to dynamically change the control range of a communication master station in a distributed control system. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiment.

[0011] 1 is a diagram showing an example of the configuration of a distributed control system according to a first embodiment; FIG. 2 is a diagram showing an example of the configuration of a communication packet; FIG. 3 is a flowchart showing the recognition process of a control range boundary by a communication slave station; FIG. 4 is a diagram showing the state of a communication master station after the recognition process of the control range boundary; FIG. 5 is a diagram showing the state of a distributed control system after the recognition process of a control range boundary by another communication master station when one communication master station stops in the second embodiment; FIG. 6 is a diagram showing the state of a distributed control system after the recognition process of a control range boundary; FIG. 7 is a diagram showing an example of the configuration of a distributed control system according to a third embodiment; FIG. 8 is a diagram showing an example of the resetting of a slave station address by another communication master station when one communication master station stops in the third embodiment; FIG. 9 is a diagram showing another example of the resetting of a slave station address by another communication master station when one communication master station stops in the third embodiment;

[0012] Hereinafter, embodiments of a distributed control system according to the present disclosure will be described with reference to the drawings. The distributed control system of each embodiment can be applied to industrial equipment such as biochemical and immunological analyzers, various manufacturing equipment, and robots. The industrial equipment includes multiple centralized control boards, various devices such as sensors and motors, and analog transmission lines connecting the control boards and the various devices.

[0013] [First Embodiment] <Configuration Example of a Distributed Control System> FIG. 1 is a diagram showing a configuration example of a distributed control system 1 according to a first embodiment. As shown in FIG. 1, the distributed control system 1 includes a plurality of (two) communication master stations 101, a plurality of communication slave stations 102, and a plurality of communication paths (dotted or solid lines in FIG. 1). The communication paths connect the communication master stations 101 to each other, the communication slave stations 102 to each other, and the communication master stations 101 to the communication slave stations 102. The communication master stations 101 are connected to each other by the communication paths (dotted lines) to form a first network 103. The communication master station 101 is connected to adjacent communication slave stations 102 by communication paths (solid lines). The adjacent communication slave stations 102 are connected to each other by communication paths (solid lines). In this way, the communication master station 101 forms a second network 104 connected to the plurality of communication slave stations 102 via the communication paths. The communication master station 101 transmits a control command for the distributed control system 1 to the communication slave stations 102 by using a communication packet 105. The control command includes information such as a target speed or angle of the motor, for example.

[0014] 1, the identifiers of the communication master stations 101 are represented as P1, P2, etc., with the final number indicating the master station address 1011. The identifiers of the communication slave stations 102 are represented as C1-1, C1-2, etc. The final number of the identifier of the communication slave station 102 indicates the slave station address 1021, and the number following the "C" indicates the master station address 1011 of the communication master station 101 that controls the communication slave station 102. In this way, the communication slave stations 102 are each assigned a slave station address 1021 by the communication master station 101 that controls the communication slave station 102, and information about the master station address 1011 is set.

[0015] In the example of Figure 1, the multiple communication master stations 101 are composed of two communication master stations P1 and P2. The multiple communication slave stations 102 are composed of communication slave stations C1-1 to C1-6 and communication slave stations C2-1 to C2-6. Under normal circumstances, the communication master station P1 controls the communication slave stations C1-1 to C1-6. Under normal circumstances, the communication master station P2 controls the communication slave stations C2-1 to C2-6.

[0016] The second network 104 may be configured, for example, using (1) a daisy-chain connection such as the communication master station P1, the communication slave station C1-1, and the communication slave station C1-2, or (2) a branching connection such as from the communication slave station C1-1 to the communication slave station C1-2 and from the communication slave station C1-1 to the communication slave station C1-3. Each communication slave station 102 is connected to the communication master station 101 that controls it, or to the communication master station 101 that controls it and other communication slave stations 102, via the second network 104. In other words, the second network 104 has a control communication path from a certain communication master station 101 through one or more communication slave stations 102 that it controls. For example, for the communication slave station C1-2, the control communication path is the series of routes from the communication master station P1, the communication slave station C1-1, and the communication slave station C1-2. The communication slave station 102 transmits a control response to the communication master station 101 using a communication packet 105. A communication slave station 102 shares control information with other communication slave stations 102 that are directly connected to it through communication packets 105. The control information includes, for example, information such as detected values ​​from sensors and current values.

[0017] 2 is a diagram showing an example of the configuration of a communication packet 105. The communication packet 105 has a slave station address 1021 indicating the source or destination of the communication packet, and communication data 201. The communication slave station 102 reads the slave station address 1021 and communication data 201 from the received communication packet 105, and controls the device or transfers the communication packet 105.

[0018] <Control Range Boundary Recognition Method> Next, a method for recognizing a control range boundary in the distributed control system 1 will be described. First, the communication master station 101 uses a communication packet 105 to instruct the communication slave stations 102 that it controls to recognize the control range boundary. Specifically, the communication master station P1 instructs the directly connected communication slave station C1-1 to recognize the control range boundary. The communication master station P2 instructs the directly connected communication slave station C2-1 to recognize the control range boundary. The control range boundary recognition process can be executed, for example, when a failure or abnormality occurs in the distributed control system 1 and the presence or absence of an abnormality is to be confirmed.

[0019] 3 is a flowchart showing a control range boundary recognition process performed by the communication slave station 102. In step S300, the communication slave station 102 determines whether or not it has received a control range boundary recognition command. If the determination in step S300 is YES, the process proceeds to step S301. If the determination in step S300 is NO, the process proceeds to step S302.

[0020] In step S301, the communication slave station 102 transmits a master station information packet including the master station address 1011 set for itself in the communication data 201 to another communication slave station 102 directly connected to itself, and then proceeds to step S303. In step S302, the communication slave station 102 determines whether or not it has received the master station information packet. If the answer is YES in step S302, the process proceeds to step S307. If the answer is NO in step S302, the process proceeds to step S300.

[0021] In step S303, the communication slave station 102 determines whether or not it has received a master station information packet within a certain time period after the transition. If the determination in step S303 is YES, the process proceeds to step S304. If the determination in step S303 is NO, the process ends.

[0022] In step S304, the communication slave station 102 determines whether the master station address 1011 in the master station information packet matches the master station address 1011 set for itself. If the determination in step S304 is YES, the process proceeds to step S305. If the determination in step S304 is NO, the process proceeds to step S306.

[0023] In step S305, the communication slave station 102 determines that the boundary between the communication slave station 102 and the other communication slave station that transmitted the parent station information packet is not a control range boundary, and the process proceeds to step S303. In step S306, the communication slave station 102 determines that the boundary between the communication slave station 102 and the other communication slave station that transmitted the parent station information packet is a control range boundary, and the process proceeds to step S303.

[0024] In step S307, the communication slave station 102 determines whether the master station address 1011 in the master station information packet matches the master station address 1011 set for itself. If the determination is YES in step S307, the process proceeds to step S308. If the determination is NO in step S307, the process proceeds to step S309.

[0025] In step S308, the communication slave station 102 determines that the boundary between it and the other communication slave station 102 that transmitted the parent station information packet is not a control range boundary, and the process proceeds to step S310. In step S309, the communication slave station 102 determines that the boundary between it and the other communication slave station 102 that transmitted the parent station information packet is a control range boundary, and the process proceeds to step S310.

[0026] In step S310, the communication slave station 102 returns the master station information packet to the communication slave station 102 that transmitted the master station information packet, and ends the process. After ending the process, the communication slave station 102 suppresses unnecessary transfer (communication) of communication packets in communication with the communication slave station 102 that it has recognized as being at the control range boundary.

[0027] FIG. 4 is a diagram showing the state after the control range boundary recognition process of the communication master station 101. As shown in FIG. 4, a control range boundary 401 is set between the communication slave stations C1-5 and C1-6 and the communication slave stations C2-5 and C2-6. The communication slave station 102 transmits information about the recognized control range boundary 401 to the communication master station 101. The communication master station 101 compares the control range boundary set in advance with the information about the control range boundary 401 received from the communication slave station 102. If these match, the communication master station 101 recognizes that the configuration is as set in advance. If they differ, the communication master station 101 recognizes that a failure (abnormality) such as a communication path error or disconnection has occurred within the second network 104.

[0028] Summary of First Embodiment As described above, the distributed control system 1 of this embodiment includes a plurality of communication master stations 101, a plurality of communication slave stations 102, and a plurality of communication paths connecting the communication master stations 101 with each other, between the communication master stations 101 and the communication slave stations 102, and between the communication slave stations 102. A first network 103 is formed by connecting the communication master stations 101 with each other via the communication paths. A second network 104 is formed by connecting all of the communication slave stations 102 via the communication paths and connecting the communication master station 101 with at least one communication slave station 102 directly connected thereto. The second network 104 has at least one control communication path including the communication master station 101 and one or more communication slave stations 102 controlled by the communication master station 101. The communication master station 101 has a master station address for distinguishing itself from other communication master stations 101, controls at least one communication slave station 102, and assigns a slave station address 1021 for identifying the communication slave station 102 it controls to the communication slave station 102. Each communication slave station has a slave station address 1021 assigned by the communication master station 101 that controls it, and shares control information with other directly connected communication slave stations 102. The communication master station 101 and the communication slave stations 102 controlled by the communication master station 101 communicate with each other via a control communication path using communication packets 105 (control commands and control responses) that do not include a master station address 1011 but include a slave station address 1021. The communication slave stations 102 share information about the master station address 1011 of the communication master station 101 that controls them with other directly connected communication slave stations 102, thereby executing processing to recognize the control range boundary of the communication master station 101 and suppressing unnecessary communication at the control range boundary.

[0029] According to the distributed control system 1 of the first embodiment, the control range boundary 401 of the communication master station 101 in the second network 104 is set by communication between the communication slave stations 102, eliminating the need for dedicated equipment. Therefore, the control range can be dynamically changed by changing the master station address 1011 and slave station address 1021 (identifiers of the communication slave stations 102) set in the communication slave stations 102. Furthermore, because the communication slave stations 102 recognize the control range boundary 401 in accordance with the actual situation, they can discover abnormalities such as connection errors and broken wires within the second network 104.

[0030] Second Embodiment In the first embodiment described above, the recognition of the control range boundary 401 of the communication master station 101 under normal circumstances has been described. In the second embodiment, the resetting of the control range boundary and the slave station address in the case where one communication master station 101 (communication master station P2) of the multiple communication master stations 101 stops will be described.

[0031] 5 is a diagram showing how the communication master station P1 resets the slave station addresses when the communication master station P2 of the distributed control system 1 stops. When the communication master station P2 stops, the communication master station P1 recognizes the stop of the communication master station P2 via the first network 103. The communication master station P1 assigns a new slave station address 1021 to the communication slave station 102 controlled by the communication master station P2 using a communication packet 105, and sets its own master station address 1011. The communication master station P1 commands the communication slave station 102, which has been assigned the new slave station address 1021, to recognize the control range boundary 401. The communication slave station 102 then executes the process of recognizing the control range boundary 401 (FIG. 3).

[0032] In the example of Figure 5, the identifier of communication slave station C2-5 is set to C1-7. The identifier of communication slave station C2-6 is set to C1-8. The identifier of communication slave station C2-3 is set to C1-9. The identifier of communication slave station C2-4 is set to C1-10. The identifier of communication slave station C2-1 is set to C1-11. The identifier of communication slave station C2-2 is set to C1-12.

[0033] 6 is a diagram showing the state of the distributed control system 1 after the recognition process of the control range boundary 401. The control range boundary 401 that existed when the communication master station P2 was stopped has disappeared, and the communication master station P1 now controls all of the communication slave stations 102.

[0034] Summary of the Second Embodiment According to the method of resetting the control range boundary 401 and the slave station address 1021 of the communication master station 101 in the distributed control system 1 according to the second embodiment, even if one communication master station 101 stops, it is possible for another communication master station 101 to take over control. In this way, continuous operation is possible even when the communication master station 101 stops, so it is possible to reduce the downtime of a device to which the distributed control system 1 is applied. Other effects when the distributed control system 1 is applied are the same as those of the first embodiment.

[0035] [Third Embodiment] In the first and second embodiments, a description has been given of a distributed control system 1 including two communication master stations 101. In the third embodiment, a description will be given of resetting of control range boundaries and slave station addresses in a case where the distributed control system includes three communication master stations 101.

[0036] FIG. 7 is a diagram showing an example of the configuration of a distributed control system 2 according to the third embodiment. The distributed control system 2 includes three communication master stations 101 (communication master stations P1, P2, and P3). Under normal circumstances, the communication master station P1 controls the communication slave stations C1-1 to C1-6. Under normal circumstances, the communication master station P2 controls the communication slave stations C2-1 to C2-6. Under normal circumstances, the communication master station P3 controls the communication slave stations C3-1 to C3-6. A control range boundary 401 is set between the communication slave stations C1-5 and C1-6 and the communication slave stations C2-1 and C2-2. In addition, a control range boundary 401 is set between the communication slave stations C2-5 and C2-6 and the communication slave stations C3-5 and C3-6.

[0037] 7 shows a situation in which communication master station P2 (first communication master station) has stopped operating. In this case, as described in the second embodiment, communication master stations P1 and P3 (second and third communication master stations) that have not failed assign a new slave station address 1021 to the communication slave station 102 that was controlled by communication master station P2. The method of assigning this slave station address can be determined in advance by the user of distributed control system 2.

[0038] 8 is a diagram showing an example of resetting of slave station addresses by communication master station P3 when communication master station P2 stops in the distributed control system 2. For example, as shown in FIG. 8, all of the communication slave stations 102 C2-1 to C2-6 can be assigned to be controlled by communication master station P3. Specifically, the identifier of communication slave station C2-1 is set to C3-11. The identifier of communication slave station C2-2 is set to C3-12. The identifier of communication slave station C2-3 is set to C3-9. The identifier of communication slave station C2-4 is set to C3-10. The identifier of communication slave station C2-5 is set to C3-7. The identifier of communication slave station C2-6 is set to C3-8.

[0039] After the new slave station address is assigned, the communication slave station 102 executes the process (FIG. 3) for recognizing the control range boundary 401. As shown in FIG. 8, after the process for recognizing the control range boundary 401 is executed, the control range boundary 401 is set only between the communication slave stations C1-5 and C1-6 and the communication slave stations C3-11 and C3-12.

[0040] 9 is a diagram showing another example of resetting of slave station addresses by communication master stations P1 and P3 when communication master station P2 stops in the distributed control system 2. As shown in FIG. 9, it is also possible to divide and assign the slave station addresses of the communication slave stations 102 controlled by communication master station P2 between communication master stations P1 and P3. Specifically, the identifier of communication slave station C2-1 is set to C1-7. The identifier of communication slave station C2-2 is set to C1-8. The identifier of communication slave station C2-3 is set to C1-9. The identifier of communication slave station C2-4 is set to C1-10. The identifier of communication slave station C2-5 is set to C3-7. The identifier of communication slave station C2-6 is set to C3-8.

[0041] After the new slave station address is assigned, the communication slave station 102 executes the recognition process (FIG. 3) of the control range boundary 401. As shown in FIG. 9, after the recognition process of the control range boundary 401 is executed, the control range boundary 401 is set only between the communication slave stations C1-9 and C1-10 and the communication slave stations C3-7 and C3-8. As described with reference to FIGS. 8 and 9, it is possible to set the control range boundary in accordance with the actual situation.

[0042] <Summary of the Third Embodiment> As in the second embodiment, according to the method of resetting the control range boundary 401 and the slave station address 1021 of the communication master station 101 in the distributed control system 2 according to the third embodiment, even if one communication master station 101 stops, it is possible for another communication master station 101 to take over control. Therefore, it is possible to reduce the downtime of a device to which the distributed control system 2 is applied. In addition, the effects of applying the distributed control system 2 are similar to those of the first and second embodiments.

[0043] [Fourth Embodiment] In the first to third embodiments, the resetting of the control range boundary and the slave station address when one of the communication master stations 101 stops is described. In the fourth embodiment, the resetting of the control range boundary and the slave station address when the communication slave station 102 stops is described.

[0044] 10 is a diagram showing an example of the configuration of a distributed control system 3 according to the fourth embodiment. In the distributed control system 3, the number of communication master stations 101 and the number of communication slave stations 102 are the same as those in the distributed control system 1 ( FIG. 1 ) of the first embodiment, but differs from the distributed control system 1 of the first embodiment in that the most downstream communication slave stations 102 are not directly connected to each other. The communication slave stations 102 that are under control of the communication master station 101 in normal operation and the control range boundary 401 are also the same as those in the distributed control system 1 of the first embodiment.

[0045] In FIG. 10 , the communication slave station 102 C1-3 stops, and communication from the communication master station P1 to the communication slave stations C1-5 and C1-6 is interrupted. In such a case, the communication master station P2 resets the slave station addresses. When the communication slave station C1-3 stops, the communication master station P1 notifies the other communication master stations 101 of the stop of the communication slave station C1-3 via the first network 103. The communication master station P2 assigns a new slave station address 1021 to the communication slave station 102 that the communication master station P1 has become unable to control due to the stop of the communication slave station C1-3, among the communication slave stations 102 that the communication master station P1 controlled, using a communication packet 105, and sets its own master station address 1011. Specifically, the identifier of the communication slave station C1-5 is set to C2-7. The identifier of the communication slave station C1-6 is set to C2-8. After the new slave station address is assigned, the communication slave station 102 executes the recognition process of the control range boundary 401 (FIG. 3).

[0046] 11 is a diagram showing the state of the distributed control system 3 after the recognition process of the control range boundary 401. When the communication slave station C1-3 was stopped, the control range boundary 401 was set between the communication slave stations C1-5 and C1-6 and the communication slave stations C2-5 and C2-6. In contrast, after the control range boundary is reset, the control range boundary 401 is set between the communication slave stations C1-3 and C1-4 and the communication slave stations C2-7 and C2-8. In this way, the communication master station P2 is reset to control the communication slave stations C1-5 and C1-6 (C2-7 and C2-8) that have become uncontrollable by the communication master station P1.

[0047] <Summary of the Fourth Embodiment> According to the distributed control system 3 of the fourth embodiment, even if one communication slave station 102 stops, another communication master station 101 can take over control of the remaining communication slave station 102. This makes it possible to reduce downtime of a device to which the distributed control system 3 is applied. Other effects achieved by applying the distributed control system 3 are similar to those of the first embodiment.

[0048] [Modifications] The present disclosure is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present disclosure, and it is not necessary to include all of the described configurations. Furthermore, a part of one embodiment can be replaced with a configuration of another embodiment. Furthermore, a configuration of another embodiment can be added to a configuration of one embodiment. Furthermore, a part of the configuration of each embodiment can be added to, deleted from, or substituted for a part of the configuration of another embodiment.

[0049] 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. Furthermore, the above-described configurations, functions, etc. may be implemented in software by a processor interpreting and executing a program that implements each function. Information such as programs, tables, and files that implement each function can be stored in a storage device such as a memory, hard disk, or solid-state drive (SSD), or in a storage medium such as an IC card, SD card, or DVD. Furthermore, the communication paths shown are those considered necessary for explanation, and do not necessarily represent all communication paths in a product to which the distributed control system of the present disclosure is applied.

[0050] 1, 2, 3... Distributed control system 101... Communication master station 1011... Master station address 102... Communication slave station 1021... Slave station address 103... First network 104... Second network 105... Communication packet 201... Communication data 401... Control range boundary

Claims

1. A distributed control system comprising a plurality of communication master stations, a plurality of communication slave stations, and a plurality of communication paths connecting the communication master stations to each other, between the communication master stations and the communication slave stations, and between the communication slave stations, wherein a first network is formed by connecting the communication master stations to each other via the communication paths, all of the communication slave stations are connected via the communication paths, and a second network is formed by connecting the communication master station to at least one of the communication slave stations directly connected thereto, and the second network has at least one control communication path including the communication master station and one or more of the communication slave stations controlled by the communication master station, and the communication master station has a master station address for distinguishing it from other communication master stations, controls at least one of the communication slave stations, and assigns to the communication slave station a slave station address for identifying the communication slave station it controls, and the communication master station and the communication slave station controlled by the communication master station are A distributed control system in which communication slave stations communicate with each other via the control communication path using packets that do not include the parent station address but include the child station address, wherein the communication slave stations have the child station address assigned by the communication parent station that controls them, share control information with other communication slave stations that are directly connected to them, and share information about the parent station address of the communication parent station that controls them with other communication slave stations that are directly connected to them, thereby executing a process to recognize the boundary of the control range of the communication parent station and suppressing unnecessary communication at the boundary of the control range.

2. A distributed control system as claimed in claim 1, wherein the communication master station controls the communication slave stations by transmitting control commands to the communication slave stations via the packets, and the communication slave stations transmit control responses to the communication master station that controls them via the packets.

3. A distributed control system as claimed in claim 1, wherein the communication slave station executes a process of recognizing the control range boundary of the communication master station in response to a command to recognize the control range boundary from the communication master station or periodically.

4. A distributed control system as described in claim 1, wherein the communication slave station transmits information about the recognized control range boundary to the communication master station, and the communication master station compares the received control range boundary with a control range boundary that has been set in advance, thereby detecting connection errors within the second network.

5. A distributed control system as described in claim 1, wherein, when an abnormality occurs in any of the communication master stations, the other communication master stations detect the abnormality in that communication master station, assign a new slave station address to the communication slave station that was controlled by that communication master station, the communication slave station that has been assigned the new slave station address executes a process to recognize and update the control range boundary, and the communication master station resumes control.

6. A distributed control system as claimed in claim 1, wherein, when an abnormality occurs in any of the communication slave stations and communication between the communication master station and the communication slave station is interrupted, the other communication master stations detect the interruption of communication, assign a new slave station address to the communication slave station that the communication master station can no longer control, the communication slave station that has been assigned the new slave station address executes a process to recognize and update the control range boundary, and the communication master station resumes control.

7. A distributed control system as described in claim 1, wherein the plurality of communication master stations include a first communication master station, a second communication master station, and a third communication master station, and when an abnormality occurs in the first communication master station, at least one of the second communication master station or the third communication master station detects the abnormality in the first communication master station, and assigns a new slave station address to the communication slave station that was controlled by the first communication master station, and the communication slave station to which the new slave station address has been assigned executes a process to recognize and update the control range boundary, and the second communication master station and the third communication master station resume control.

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