JP2005159483A - Duplexing communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a configuration wherein data transmission/reception is ordinarily carried out by duplexing communication systems in parallel, to efficiently utilize both the communication systems, and to prevent occurrence of a data delay and loss of data on the occurrence of a fault in one of the communication systems. <P>SOLUTION: A communication control section 12 stores data received from a data collection section 10 to one or both transmission queues 13a, 13b including free slots and transmits the data to a corresponding communication path in a normal state. When reply data are not returned within a prescribed time, time-out takes place and the original transmission data are deleted from the transmission queues, and when time-out takes place while the slots are fully occupied, it is discriminated that the communication system at the transmission queue side is faulty. The oldest transmission data, not being all un-transmitted data, among the transmission data stored in the other transmission queue are searched and stored to a newly generated free slot and transmitted. Thus, duplexing data is guaranteed in the normal state, and loss of data is surely be prevented even in an abnormality state. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a duplex communication device used for exchange of various measurement data, control data, and the like in a control / monitoring system such as process control and a remote monitoring system.

  In a distributed control / monitoring system for factories, power generation facilities, plants, etc., data communication is performed between a computer (operator console) and a control / monitoring terminal via a communication path such as a LAN. In this type of system, data reliability is very important, and it is required to continue necessary control / monitoring as much as possible even when a communication path failure or some other device malfunction occurs. Therefore, conventionally, a duplex configuration in which a communication system including a communication path and a communication unit on the control / monitoring terminal side is duplexed is often employed (see, for example, Patent Document 1).

  In such a duplex communication device in which the communication system is duplexed, two systems are roughly used as the two communication systems. One of them is a dual system in which bi-directional communication is performed almost always through both communication systems, and communication is performed using data obtained by the communication system that can obtain a good communication state as a result. . The other one is a switching method in which bidirectional communication is normally performed only through one main communication system, and switching to bidirectional communication via the other standby communication system is performed when a failure occurs in the communication. . In the former method, a communication path that always passes through two communication systems is established, so that even if a failure occurs suddenly in one communication system, it is possible to quickly take over to the other communication system. There is.

  In the dual method, in general, when certain data is sent in parallel via two communication systems, a synchronization process is performed to synchronize both transmission timings (see, for example, Patent Document 2). In this case, since the same data is always transmitted to both communication paths, even if a failure occurs in one communication system, data can be exchanged through the other normal communication path. Further, in the communication system in which an abnormality has occurred, the response data corresponding to the transmission data is not sent back from the control / monitoring terminal within a predetermined time, so that it can be detected that there is an abnormality in the communication system. . However, since it takes a certain amount of time to detect the abnormality, it is necessary to wait for transmission of the next data on the normal communication system side during that period. For this reason, when it is desired to send transmission data one after another, the data may be delayed.

  The problem of such retention of transmission data during the standby time is caused by providing a buffer or the like for temporarily storing data between a circuit that generates transmission data and a communication circuit that sends the data to the communication path. To some extent. However, when such a buffer is provided, asynchronous communication will be temporarily performed during the period from when an abnormality occurs in one communication system until it can be detected, and when an abnormality occurs or recovery from the abnormality If switching of time etc. cannot be performed appropriately, there is a possibility that certain data will not be transmitted from any communication path, and data loss may occur.

Japanese Utility Model Publication No. 6-2407 JP 2003-23415 A

  The present invention has been made in view of these points, and the object of the present invention is to guarantee duplexing of transmission / reception data when both communication systems are normal and a failure occurs in one communication system. It is an object of the present invention to provide a duplex communication device that can reliably prevent transmission / reception data from being lost even in such a case.

The present invention, which has been made to solve the above-mentioned problems, uses a first and second two-channel communication path connected in parallel between a control / monitoring device and a control / monitoring terminal. In the duplex communication apparatus in which predetermined transmission data is transmitted from the control / monitoring terminal to the control / monitoring terminal, and the control / monitoring terminal that receives the data transmits / receives response data to the control / monitoring apparatus to send / receive data. / Monitoring device
a) a first transmission queue for storing n pieces of transmission data transmitted through the first communication path;
b) a second transmission queue for storing m pieces of transmission data to be transmitted through the second communication path;
c) timeout determination means provided for each of the first and second communication paths, and determining a timeout when response data for the transmission data transmitted through the communication path is not sent back within a predetermined time;
d) Communication control means for controlling transmission / reception of data via the first and second communication paths using the first and second transmission queues, and for each of the first and second transmission queues,
When there is a vacancy in the transmission queue except for the occurrence of the vacancy in the transmission queue due to timeout, while sending the transmission data with a transmission request to the transmission queue and sending the transmission data through the corresponding communication path, When the response data for that is received, the original transmission data is deleted from the transmission queue,
If the timeout determination means determines that a timeout has occurred, delete the transmission data that has timed out from the transmission queue,
In addition, when a vacancy occurs in the transmission queue due to timeout, the vacant space is filled with the oldest transmission data in the other transmission queue instead of the transmission data requested to be transmitted, and the corresponding communication path is used. Communication control means for transmitting the transmission data;
It is characterized by having.

  In the duplex communication device according to the present invention, for example, when there is a vacancy in the first transmission queue, the transmission data requested to be transmitted is stored in the first transmission queue and transmitted through the first communication path. At the same time, if the second transmission queue is also free, the same transmission data is stored in the second transmission queue and transmitted through the second communication path. If the communication system including the first and second communication paths is normal, the response data for the transmission data is returned from the control / monitoring terminal through any of the communication paths. It is determined that the transfer has been successful, and the transmission data is deleted from the transmission queue.

  On the first transmission queue side, it is possible to wait for response data for up to n transmission data to return, and in this state, if there is a vacancy in the first transmission queue due to transmission data deletion as described above, Data with a transmission request can be transmitted. On the other hand, on the second transmission queue side, it is possible to wait for response data for up to m pieces of transmission data to return, and in this state, if the second transmission queue becomes empty due to transmission data deletion as described above, Next, data with a transmission request can be transmitted.

  Since both transmission queues are always empty at the start of transmission, the same transmission data is sent to both communication paths almost simultaneously, and if both communication paths are in good condition, a response is made via both communication paths. Data comes back almost simultaneously. Accordingly, transmission data is deleted almost simultaneously in both transmission queues. As a result, data is transmitted and received synchronously through both communication paths. That is, the same transmission data is sent to the control / monitoring terminal through both communication paths in parallel, and complete data duplication is achieved.

  From this state, a situation is assumed in which a failure has occurred in one of the communication channels, for example, the second communication channel. At this time, since the response data for the transmission data transmitted through the second communication path does not return, if transmission requests are generated one after another, the second transmission queue becomes full, and transmission of further data is temporarily stopped. Stop. On the other hand, since data transmission / reception through the first communication path is performed smoothly, some data is transmitted / received only through the first communication path during the temporary stop period. Since the response data does not return on the second communication path side, a timeout occurs when a certain time elapses, and the transmission data that has timed out is deleted from the second transmission queue. As a result, a new space is generated in the second transmission queue.

  At this time, if there is a vacancy due to this timeout, the communication control means estimates that there is a high possibility of occurrence of an abnormality on the transmission queue side. Therefore, instead of sending transmission data with a transmission request, instead of this, the oldest transmission data in time is used in the other first transmission queue, and the newly generated space resulting from timeout is filled. The data is transmitted through the second communication path. Since this data has already been sent through the first communication path, even if transmission / reception through the second communication path fails, there is a high possibility that transmission / reception will normally be performed through the other first communication path. . As a result, no untransmitted data is sent out to the second communication path that is likely to be abnormal before the first communication path that is normal, and all the transmission data is the first. It is guaranteed to be transmitted through the communication path. Of course, when a failure occurs in the first communication path, it is ensured that all transmission data is similarly transmitted through the second communication path.

  As described above, according to the duplex communication device according to the present invention, when both of the two communication systems are normal, the duplex communication is completely guaranteed, and an abnormality occurs in any one of the communication systems. Even when communication is disabled, it is guaranteed that all data is sent without loss through other normal communication systems. Therefore, according to the duplex communication device according to the present invention, duplex communication can be achieved with high reliability.

  Hereinafter, an embodiment of a control / monitoring system using a duplex communication apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a control / monitoring system according to the present embodiment, and FIG. 2 is a functional configuration diagram of a main part of a computer which is a control / monitoring device in FIG.

  In the control / monitoring system of the present embodiment, the computer 1 which is the center of the control / monitoring device has an operator console function, and has two communication paths such as two independent LANs (first communication path 2a, first communication path). 2 are mutually connected to the control / monitoring terminal 3 via the communication path 2b). The control / monitoring terminal 3 includes two independent communication units (first communication unit 31a and second communication unit 31b), a control unit 32 incorporating a CPU and the like, and a predetermined physical quantity or chemical for a control / monitoring target. The control unit 32 includes a storage unit 33 for accumulating measurement data obtained by the measurement unit 34. As is apparent from FIG. 1, in this system, the area from the input / output of the computer 1 to the control unit 32 of the control / monitoring terminal 3 is duplicated.

  Although only one control / monitoring terminal 3 is shown in FIG. 1, the computer 1 can collect data from many control / monitoring terminals 3 connected to the communication paths 2a and 2b. . Further, a plurality of computers 1 themselves may be connected to the communication paths 2a and 2b.

  The basic operation of this system is as follows. In the control / monitoring terminal 3, the measurement unit 34 performs measurement on the control / monitoring target at predetermined time intervals under the control of the control unit 32 to acquire measurement data, and sequentially accumulates the data in the storage unit 33. To do. The computer 1 transmits a control command for data collection to the control / monitoring terminal 3 as transmission data at a predetermined timing. This control command includes information such as a range of data to be collected (such as a memory address range or a time range specification in the storage unit 33). Upon receiving this control command, the control unit 32 reads out data in the designated range from the storage unit 33 and sends it back to the computer 1 as response data via the communication paths 2a and 2b.

  Therefore, when viewed from the computer 1, measurement data can be received as a response to the transmitted control command. Based on the measurement data collected from each control / monitoring terminal 3 in this way, the computer 1 performs various displays such as a trend graph on the monitor screen or performs warning notification. Of course, data for controlling the operation is sent to the control / monitoring terminal 3 as a control command, and a confirmation signal that the control / monitoring terminal 3 has received the control command is sent back to the computer 1 as response data. Also good.

  When a plurality of control / monitoring terminals 3 are provided, each control / monitoring terminal 3 is assigned a different address number, and the control / monitoring terminal 3 is assigned with the address number to a control command or the like. Can identify whether the control command is addressed to its own terminal or to another terminal.

  As shown in FIG. 2, in the computer 1, the data collection unit 10 has a function of generating transmission data such as the above-described control commands related to data collection, and a communication control unit (first and second communication of the present invention). The measurement data received via the control means) 12 is stored in the data storage unit 11 such as a hard disk. The communication control unit 12 includes a first transmission queue 13a and a second transmission queue 13b, which are a kind of transmission data buffer, and has a function of appropriately distributing transmission data received from the data collection unit 10 to two transmission / reception units described later. At the same time, the response data received via the transmission / reception unit is selected and transferred to the data collection unit 10.

  The first and second transmission / reception units 14a and 14b are provided independently for the first and second communication paths 2a and 2b, and response data is obtained by performing various checks such as error detection of response data as shown in the figure. Response confirmation units (response data confirmation means in the present invention) 15a, 15b, the elapsed time from the time each transmission data is sent to the communication paths 2a, 2b, and whether there is response data within a predetermined time In addition to the time-out determination unit (time-out detection means in the present invention) 16a and 16b for checking whether or not, a function of modulation / demodulation processing is included. Note that some or all of the functions of these units are achieved by causing a CPU to execute a predetermined control program.

  As described above, in this system, the communication system is duplicated between the communication control unit 12 of the computer 1 and the control unit 32 of the control / monitoring terminal 3, and each communication system is provided with transmission queues 13a and 13b, respectively. And a communication protocol in a duplex communication system using the transmission queues 13a and 13b. Hereinafter, this communication protocol will be described in detail.

  FIG. 3 is a functional conceptual diagram for explaining a normal communication operation in this control / monitoring system, and FIG. 4 is a sequence diagram showing a standard processing procedure at that time. In this example, each of the first transmission queue 13a and the second transmission queue 13b is a kind of buffer memory (FIFO) having slots for storing three pieces of transmission data, but the number of slots in the transmission queue is this. It is not limited to. At this time, the communication control unit 12 performs the communication operation via the first transmission / reception unit 14a to send the transmission data input from the data collection unit 10 to the first communication 2a and the second communication path 2b in parallel. The communication operation via the second transmission / reception unit 14b is executed independently. That is, the sequence shown in FIG. 4 is basically executed for both communication paths 2a and 2b. Here, the first communication path 2a side will be described here.

  When there is a transmission data transmission request from the data collection unit 10, the communication control unit 12 transmits data using the path with the empty slot of the first transmission queue 13 a and the second transmission queue 13 b. That is, if both transmission queues 13a and 13b have empty slots, transmission is performed in parallel from both paths, and if there is only an empty slot in one transmission queue, transmission is performed using the path on the transmission queue side. .

  Specifically, when there is a transmission request, the communication control unit 12 checks whether or not there is an empty slot in the first transmission queue 13a. Since it is assumed that transmission starts, all slots are empty, and it is determined that data can be transmitted to the first communication path 2a through the first transmission / reception unit 14a. The transmission data received from the data collection unit 10 is sent to the first communication path 2a through the first transmission / reception unit 14a, and the transmission data is stored in the first transmission queue 13a. The response confirmation unit 15a starts monitoring whether the response data has been returned for the transmitted data. When the control / monitoring terminal 3 receives the transmission data, for example, a control command, the control / monitoring terminal 3 executes processing / control according to the command, and returns, for example, the collected measurement data as response data through the first communication path 2a. When the response confirmation unit 15a confirms the response data, it can be determined that the original transmission data of the response data has reached the control unit 32 through the first communication unit 31a, that is, the data has been successfully exchanged. Therefore, in that case, the communication control unit 12 deletes the original transmission data stored in the first transmission queue 13a.

  The processing operation as described above is similarly executed on the second communication path 2b side. Assuming the start of transmission, all slots in the second transmission queue 13b are also empty, so that the same transmission data is transmitted almost simultaneously (that is, with almost no time difference) through the first communication path 2a and the second communication path 2b. It is done. Since the response data for this also returns almost simultaneously, the transmission data in the transmission queues 13a, 13b is also deleted almost simultaneously, thereby generating a slot empty. Accordingly, although the processing is basically performed independently in both communication systems, if there is no problem in the communication system, data transmission / reception is substantially achieved in two communication systems in a synchronous manner. However, since the response data received through both communication paths 2a and 2b are the same, only the response data received first is passed to the data collection unit 10, and the other is discarded.

  In the example of FIG. 3, each transmission queue 13a, 13b has three slots, so even if a transmission request for the next transmission data occurs before response data for a certain transmission data returns. As long as there are empty slots, the transmission process can be performed as described above. For example, in FIG. 3, before transmitting the transmission data [A] and returning the response data [A ′], the next transmission data [B] is transmitted, and the response data [A ′] is returned. It is possible to transmit the next transmission data [C] before coming. If the response data [A ′], [B ′], and [C ′] for the transmission data [A], [B], and [C] transmitted in this manner are returned, further transmission data [D When a transmission request is generated, since there is no empty slot in the transmission queues 13a and 13b, the process waits until an empty slot occurs, and response data [A '], [B'] or [C As soon as any of '] returns and an empty slot occurs, transmission data [D] is transmitted.

  The above description is about a case where there is no problem in the communication system. However, even if it is not actually a communication abnormality, for example, a very short communication failure due to external interference such as noise, or control / The response data is slow to return due to a sudden increase in the load on the monitoring terminal 3 or the like, or there is an error even if the response data returns, and the reliability of the information is low Can happen. Therefore, the time-out determining units 16a and 16b start timing from the time when certain transmission data is sent out, and if the timing reaches a predetermined time before the response data returns, the response data returns slowly. Judgment is made and a retransmission request is sent to the communication control unit 12.

  Upon receiving this retransmission request, the communication control unit 12 sends the transmission data again to the communication paths 2a and 2b via the transmission / reception units 14a and 14b. This retransmission operation is performed a predetermined number of times (for example, two times or three times), and if the response data does not return after a predetermined number of retransmissions, it is determined that a timeout has occurred. Even if the response data is returned, if it is confirmed that there is an error in the data as a result of the error check by the response confirmation units 15a and 15b (error that cannot be corrected), the retransmission process is performed in the same manner. Just do it. For example, when normal response data can be received by resending such transmission data, the transmission data in the transmission queue is deleted, and the transmission data requested for transmission from the data collection unit 10 is continuously transmitted as described above. What is necessary is just to process.

  Next, processing operations when an abnormality occurs in one communication system will be described with reference to FIGS. As an example, it is assumed that some trouble occurs in the second communication path 2b from the state where normal communication is performed as shown in FIG. In this case, since the response data does not return through the second communication path 2b, for example, as shown in FIG. 5, the second transmission queue 13b stores [A], [B], [C] and transmission data. As a result, there is no empty slot. When there is a transmission request for transmission data one after another from the data collection unit 10, this transmission data is transmitted through a path (first communication path 2a) on the first transmission queue 13a side where the response data has returned smoothly. .

  Now, as shown in FIG. 5, at a certain point in time, response data [D ′] to the transmission data [D] is returned, and [D] is deleted in the first transmission queue 13a. Assume that three items [E], [F], and [G] are stored. At this time, if the response data [A ′] does not return on the second transmission / reception unit 14b side and it is determined that a timeout has occurred, the transmission data [A] that has remained in the second transmission queue 13b is deleted. A new empty slot is generated. In this way, when an empty slot occurs and transmission data to be transmitted next is prepared in the data collection unit 10, normally, this completely untransmitted transmission data ([H] in FIG. 5) is used. The data is stored in the second transmission queue 13b and sent to the second communication path 2b via the second transmission / reception unit 14b. However, in this device, when a slot is newly generated by deleting data due to timeout from a state where the slot of the transmission queue is full in this way, the control is changed from that in the case where the other slots are free. To do.

  That is, as shown in FIG. 6, in the second transmission queue 13b, when the transmission data [A] is deleted due to a time-out and a slot is vacant, the transmission data given from the data collection unit 10 is stored in that slot. Instead, the oldest transmission data in the transmission data stored in the first transmission queue 13a is found, stored in the empty slot of the second transmission queue 13b, and via the second transmission / reception unit 14b. To the second communication path 2b. In other words, if an empty slot occurs due to a time-out from a slot full in one transmission queue, it is highly probable that some abnormality has occurred in the communication system on the transmission queue side. However, in the communication system, transmission of data that has not been transmitted on both paths is stopped, and processing is changed so that data that has already been transmitted (but response data has not yet returned) is transmitted on the other communication system. . In the example of FIG. 6, when an empty slot occurs in the second transmission queue 13b, the oldest data in the first transmission queue 13a is [E], so this is stored in the empty slot of the second transmission queue 13a. At the same time, it is sent to the second communication path 2b.

  If the abnormality in the second communication system continues, transmission data [B], [C], [E] stored in the second transmission queue 13b will be timed out and deleted one after another. However, since the response data for these transmission data should have returned through the first communication path 2a, necessary data can be exchanged without any problem, and data loss or the like does not occur in the middle. On the other hand, if the above processing is not changed, when an empty slot is generated in the second transmission queue 13b as shown in FIG. 5, the transmission data [H Is stored in the second transmission queue 13b and transmitted through the second communication path 2b. At this time, the transmission data [H] has not yet been transmitted through the first communication path 2a. When an empty slot occurs in the first transmission queue 13a due to the response data being obtained, if the next [I] of the transmission data [H] is already waiting in the data collection unit 10, this transmission data [ I] is stored in an empty slot of the first transmission queue 13a. For this reason, transmission data [H] transmitted only to the second communication path 2b will not be transmitted / received, resulting in data loss. In this apparatus, by appropriately changing the processing as described above, such data loss can be prevented and reliable data exchange can be realized.

  If an abnormality occurs in the first communication system, contrary to the above description, if an empty slot occurs in the first transmission queue 13a due to a timeout, the transmission data stored in the second transmission queue 13b The oldest is stored in the empty slot of the first transmission queue 13a. Therefore, even if an abnormality occurs in any communication system, data loss does not occur as long as other communication systems are normal, and data can be transmitted and received reliably.

  It should be noted that the above embodiment is merely an example of the present invention, and it is apparent that modifications and corrections can be made as appropriate within the scope of the present invention.

1 is a schematic configuration diagram of a monitoring / control system including a duplex communication device according to an embodiment of the present invention. The functional block diagram of the principal part of the computer in FIG. The functional conceptual diagram for demonstrating the communication operation at the time of normal in the control / monitoring system of a present Example. The sequence diagram which shows the procedure of the standard process in the state of FIG. The functional conceptual diagram for demonstrating the communication operation | movement when there exists abnormality in one communication system in the control / monitoring system of a present Example. The functional conceptual diagram for demonstrating the communication operation | movement when there exists abnormality in one communication system in the control / monitoring system of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Computer 2a ... 1st communication path 2b ... 2nd communication path 10 ... Data collection part 11 ... Data storage part 12 ... Communication control part 13a ... 1st transmission queue 13b ... 2nd transmission queue 14a ... 1st transmission / reception part 14b ... 2nd transmission / reception part 15a, 15b ... Response confirmation part 16a, 16b ... Timeout determination part 3 ... Control / monitoring terminal 31a ... 1st communication unit 31b ... 2nd communication unit 32 ... Control part

Claims (1)

Using the first and second communication paths connected in parallel between the control / monitoring device and the control / monitoring terminal, the predetermined transmission data is sent from the control / monitoring device to the control / monitoring terminal. Then, in the duplex communication device in which the control / monitoring terminal that receives the data sends and receives the response data by sending back the response data to the control / monitoring device, the control / monitoring device includes:
a) a first transmission queue for storing n pieces of transmission data transmitted through the first communication path;
b) a second transmission queue for storing m pieces of transmission data to be transmitted through the second communication path;
c) timeout determination means provided for each of the first and second communication paths, and determining a timeout when response data for the transmission data transmitted through the communication path is not sent back within a predetermined time;
d) Communication control means for controlling transmission / reception of data via the first and second communication paths using the first and second transmission queues, and for each of the first and second transmission queues,
When there is a vacancy in the transmission queue except for the occurrence of the vacancy in the transmission queue due to timeout, while sending the transmission data with a transmission request to the transmission queue and sending the transmission data through the corresponding communication path, When the response data for that is received, the original transmission data is deleted from the transmission queue,
If the timeout determination means determines that a timeout has occurred, delete the transmission data that has timed out from the transmission queue,
In addition, when a vacancy occurs in the transmission queue due to timeout, the vacant space is filled with the oldest transmission data in the other transmission queue instead of the transmission data requested to be transmitted, and the corresponding communication path is used. Communication control means for transmitting the transmission data;
A duplex communication device comprising:

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