JP5458904B2 - Communication system synchronization method, communication system, master station - Google Patents

Communication system synchronization method, communication system, master station Download PDF

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JP5458904B2
JP5458904B2 JP2010009842A JP2010009842A JP5458904B2 JP 5458904 B2 JP5458904 B2 JP 5458904B2 JP 2010009842 A JP2010009842 A JP 2010009842A JP 2010009842 A JP2010009842 A JP 2010009842A JP 5458904 B2 JP5458904 B2 JP 5458904B2
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communication line
transmission delay
delay time
slave
master station
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JP2011151530A (en
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道彦 佐藤
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富士電機株式会社
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  The present invention relates to a synchronization method, a communication system, and a master station for temporally synchronizing a plurality of slave stations with a master station in a communication system including a master station and a plurality of slave stations.

  In a control system having slave stations such as servo equipment and inverter equipment, each slave station may be operated in synchronization with the time of the master station. In order for each slave station to synchronize with the master station, it is necessary to consider transmission delays resulting from different distances from the master station and operating environments. Patent Documents 1 and 2 have been proposed as prior arts that consider such transmission delay.

Japanese Patent No. 4097891 Japanese Patent No. 2752883

However, in the prior arts of Patent Documents 1 and 2, for example, in a communication system consisting of a main system and a sub system, if the transmission path is changed due to a transmission failure, the transmission delay cannot be compensated, and therefore the master station and the plurality of slave stations The communication system consisting of could not be synchronized.
The present invention has been made to solve the above-described problem, and an object of the present invention is to synchronize a communication system when a transmission path is changed due to a transmission failure.

In order to solve the above problem, according to the synchronization method of the communication system of the present invention, a first communication line in which n (n ≧ 2) slave stations are connected in series, and n slave stations are in series A second communication line connected to the first communication line, n slave stations of the first communication line and n slave stations of the second communication line in association with each other, In a synchronization method of a communication system comprising a master station connected to a first communication line and a second communication line, the master station normally uses a first communication line to synchronize with the first communication line. When a transmission failure occurs in the first communication line when communicating with the n slave stations to be connected, the master station becomes a slave station connected to the first communication line before and after the location where the transmission failure occurs. Make the corresponding relay device ready for relaying and relay A step of configuring a path for bypassing communication to the first communication line via the apparatus and the second communication line, and the master station transmitting resynchronization request information to the slave station connected to the first communication line And when the slave station connected to the first communication line receives the resynchronization request information, it calculates a transmission delay time caused by communication with the master station, and synchronizes with the master station based on the transmission delay time. In this step, the slave station connected to the first communication line transmits the transmission delay time calculated by receiving the resynchronization request information to the master station. The transmission delay time of each slave station connected to one communication line is updated using the transmission delay time received from the slave station, and the size of the transmission delay time of each slave station is preset. When following location order, it determines that the synchronization of all slave stations complete.

  According to the present invention, when a transmission path is changed due to a transmission failure, a communication system composed of a master station and a plurality of slave stations can be synchronized.

It is a system block diagram in the communication system of this invention. 2 is a functional block diagram of a master station M. FIG. It is a figure which shows that the transmission failure occurred in the communication line. 2 is a functional block diagram of a slave station S. FIG. 3 is a flowchart showing the operation of a master station M.

A preferred embodiment of a synchronization method of a communication system according to the present invention will be described with reference to the accompanying drawings as appropriate.
FIG. 1 is a system configuration diagram in a communication system according to the present invention.
In FIG. 1, M denotes a master station, S1 to S4 and S1 ′ to S4 ′ denote slave stations, and D1 to D4 denote devices that function as relay apparatuses. The slave stations S1 to S4 are connected in series and constitute a first communication line as a main system. The slave stations S1 ′ to S4 ′ are connected in series and constitute a second communication line as a slave. That is, by configuring as a redundant parallel network topology composed of the first and second communication lines, the reliability against transmission failures is improved. The devices D1 to D4 connect the slave stations S1 to S4 and the slave stations S1 ′ to S4 ′ in a one-to-one correspondence.
The master station M is connected to the slave station S1 located at the end (start point) of the first communication line and the slave station S1 ′ located at the end (start point) of the second communication line. The devices D1 to D4 normally have the relay function turned off, and can be configured, for example, as switches that are turned on in a state in which the relay function can be relayed by a command from the master station M.

FIG. 2 is a diagram illustrating functional blocks of the master station M.
The master station M specifies the communication unit 1 that communicates with the slave station S and the device D, the control unit 2 that controls the operation of the master station M, and where the failure has occurred in the first and second communication lines. The failure location specifying unit 3 is included. For example, when the failure location specifying unit 3 can communicate with the slave station S2 and cannot communicate with the slave station S3, the failure location specifying unit 3 transmits a transmission failure (path failure) to the communication line between the slave station S2 and the slave station S3. Is determined to have occurred.
The master station M includes a detour path configuration unit 4, a synchronization request unit 5, a transmission delay time table 6, and a transmission delay time update unit 7.
For example, when a transmission failure occurs in the first communication line, the detour path configuration unit 4 turns on the two devices corresponding to the slave stations connected to the first communication line before and after the location of the transmission failure. A path for bypassing communication to the first communication line via the turned-on device and the second communication line is configured. Specifically, as shown in FIG. 3, when a transmission failure occurs in the communication line between the slave station S2 and the slave station S3, it corresponds to the slave stations S2 and S3 located before and after the occurrence point. The devices D2 and D3 are turned on. Therefore, the communication from the master station M to the slave station S3 arrives via “device D2−slave station S2′−slave station S3′−device D3”.

The master station M communicates with the slave stations S1 to S4 connected to the first communication line in which synchronization is established in advance using the first communication line in normal times. When a transmission failure occurs in the first communication line, the master station M communicates with the slave stations S1 to S4 using the path configured by the detour path configuration unit 4.
The synchronization request unit 5 is a function for requesting synchronization to each slave station S. The timing for establishing the synchronization of each slave station S is performed, for example, when the system is started up. The slave station S that receives the synchronization request from the synchronization request unit 5 transmits the transmission delay time calculated for synchronization with the master station M and the other slave stations S, that is, the reference clock of the own slave station S and the master station M The deviation from the reference clock is transmitted to the master station M. The master station M stores the station numbers S1 to S4 and S1 ′ to S4 ′ of the slave stations in association with the transmission delay time in the transmission delay time table 6. The synchronization request unit 5 transmits resynchronization request information to the slave station S when the detour path configuration unit 4 reconfigures the communication path. When the transmission delay time calculated in response to the resynchronization request is received from the slave station S, the transmission delay time update unit 7 updates the transmission delay time table 6. Note that synchronization is periodically performed because of a difference in time synchronization due to an individual difference between the reference clock of the timer unit 10 of the master station M and the reference clock of the timer unit 14 of the slave station S.

The master station M includes an arrangement order storage unit 8, a synchronization completion determination unit 9, and a time measuring unit 10. The arrangement order storage unit 8 stores an order determined based on the distance between each slave station S and the master station M.
The synchronization completion determination unit 9 determines that the synchronization of each slave station has been completed. The synchronization completion determination unit 9 compares the order of the transmission delay time of each slave station S held in the transmission delay time table 6 with the order of the arrangement order storage unit 8, and the synchronization of each slave station is completed. Determine whether or not. For example, when considering the first communication line, the transmission delay time of the slave station S1 closest to the master station M is the shortest, and the transmission delay time of the slave station S4 farthest from the master station M is the longest. . Therefore, if the magnitudes of the transmission delay times of the slave stations are arranged according to the arrangement order of the slave stations S, it can be determined that the synchronization of the slave stations has been completed.
FIG. 4 is a diagram illustrating functional blocks of the slave station S.
The slave station S calculates a transmission delay time caused by communication with the master station M, another slave station S, and a communication unit 11 that communicates with the device D, a control unit 12 that controls the operation of the slave station S, and the master station M. A transmission delay time calculator 13 and a timer 14.
The transmission delay time calculation unit 13 is an arithmetic unit that calculates a transmission delay time generated in communication with the master station M in order to operate in synchronization with the master station M and other slave stations S. When the slave station S receives the resynchronization request information from the master station M in accordance with the reconfiguration of the communication path by the detour path configuration unit 4, the transmission delay time calculation unit 13 first masters the frame for measuring the transmission delay. Time until transmission to the station M and reception of a response signal from the master station M is measured. The response signal generated by the master station M includes processing time information required for processing for receiving a transmission delay measurement frame from the slave station S and transmitting the response from the master station M to the slave station. Therefore, the transmission delay time calculation unit 13 of the slave station S measures the time from when the transmission delay measurement frame is transmitted to the master station M until the response signal is received, and the master station included in the response signal. The difference from the processing time information required for M is taken, and 1/2 of this difference is calculated as the transmission delay time. Here, it is assumed that the transmission rate is symmetric between upstream and downstream.

Here, when the master station M receives a transmission delay measurement frame from the slave station S and the master station M transmits a response to the slave station, the processing already known from Patent Documents 1 and 2 is performed. Briefly described. The timer unit 10 of the master station M is required for the master station M to receive a transmission delay measurement frame from the slave station S and to transmit a response signal from the master station M to the slave station S according to an instruction from the control unit 2. Measure the processing time. Then, the master station M transmits a response signal including information regarding the processing time to the slave station S. Strictly speaking, the processing time that can be measured by the time measuring unit 10 of the master station M is the time until a short time before the master station M transmits a response signal to the slave station S. That is, the processing time written in the response signal does not include the time from when the master station M generates the response signal including the processing time to when it is transmitted to the slave station S. Considering this, the processing time written in the response signal is obtained in advance by calculating the time required from the master station M generating the response signal including the processing time to transmitting it to the slave station S. The time obtained by adding this time as a correction value to the measurement value of the unit 10 may be the processing time for writing in the response signal.
The slave station S obtains the time of the slave station S by adding the transmission delay time calculated as described above to the time information of the master station M. The other slave stations S operate in the same manner by calculating the transmission delay time and obtaining the time of the slave station S, so that the entire system is synchronized with the time of the master station M.

FIG. 5 is a flowchart showing the operation of the master station M.
The synchronization request unit 5 of the master station M requests the first synchronization operation to each slave station S when the system is started up, and synchronizes the time of each slave station S (step S1). The master station M monitors a path fault (transmission fault), and when a path fault occurs, the fault location identifying unit 3 of the master station M identifies the fault location. Here, as shown in FIG. 3, when a path failure occurs between the slave station S2 and the slave station S3 connected to the first communication line (step S2, Yes), the detour path configuration unit 4 of the master station M Constitutes a detour route (step S3).
The detour path configuration unit 4 turns on the two devices D2 and D3 corresponding to the slave station S2 and the slave station S3 connected to the first communication line before and after the occurrence of the transmission failure and relays transmission data. In this state, a path for bypassing communication to the first communication line via the second communication line is configured. That is, the detour path configuration unit 4 configures a communication path so that communication from the master station M to the slave station S3 is performed via “device D2−slave station S2′−slave station S3′−device D3”. .
The synchronization request unit 5 of the master station M sends resynchronization request information to the slave station S connected to the first communication line in order to reestablish synchronization when the detour path configuration unit 4 reconfigures the communication path. Transmit and instruct the slave station S to calculate the transmission delay time (step S4).

The counterpart of the slave station S to which the synchronization request unit 5 transmits resynchronization request information may be all the slave stations S1 to S4 connected to the first communication line. Alternatively, the slave station S to which the synchronization request unit 5 transmits resynchronization request information is only the slave stations S3 and S4 connected to the first communication line after the location where the communication failure has occurred as viewed from the master station M. It is good. That is, the slave stations S1 and S2 that are already synchronized may be excluded from the synchronization targets. When the number of objects to be synchronized is reduced, it is possible to shorten the time for establishing synchronization of the entire system.
The synchronization completion determination unit 9 of the master station M determines whether the synchronization of each slave station has been completed (step S5).
The master station M stores the slave station numbers S1 to S4 and S1 ′ to S4 ′ in the transmission delay time table 6 in association with the transmission delay times. The master station M collects the transmission delay time from the slave station S responding to the resynchronization request information transmitted by the master station, and the transmission delay time update unit 7 updates the transmission delay time table 6. Then, the synchronization completion determination unit 9 compares the order regarding the magnitude of the transmission delay time of each slave station S held in the transmission delay time table 6 with the order stored in the arrangement order storage unit 8, and Determine if station synchronization is complete.
If the synchronization completion determination unit 9 determines that the synchronization is not completed (No at Step S5), the synchronization completion determination unit 9 instructs the calculation of the transmission delay time again (Step S4). If the synchronization completion determination unit 9 determines that the synchronization of each slave station has been completed (step S5, Yes), it instructs the end of the synchronization operation (step S6). The slave stations S1 to S4 operate in addition to the transmission delay times calculated by the slave stations S1 to S4 in addition to the time at which the slave stations S1 to S4 receive the master station M, so that the communication system including the master station M and the slave stations S1 to S4 operates in synchronization. To do.

  In the embodiment of the present invention, the synchronization completion determination unit 9 instructs the end of the synchronization operation after determining that the synchronization of each slave station is completed, but the synchronization completion determination unit 9 does not wait for the determination of the synchronization completion determination unit 9 to synchronize. The operation can also be terminated. That is, when each slave station S calculates the transmission delay time, the slave station S can be operated by adding the determined transmission delay time to the time of the slave station without waiting for the determination of the synchronization completion determination unit 9. However, if the synchronization completion determination unit 9 as in the present invention is provided, it is possible to determine that the slave station S is normally synchronized, and therefore, there is an effect that it is possible to prevent an unstable operation in a state of being out of synchronization.

M Master station S Slave station 1 Communication unit 2 Control unit 3 Fault location specifying unit 4 Alternate path configuration unit 5 Synchronization request unit 6 Transmission delay time table 7 Transmission delay time update unit 8 Arrangement order storage unit 9 Synchronization completion determination unit 10 Timing unit 11 Communication Unit 12 Control Unit 13 Transmission Delay Time Calculation Unit 14 Timekeeping Unit

Claims (4)

  1. a first communication line in which n (n ≧ 2) slave stations are connected in series, a second communication line in which n slave stations are connected in series, and n of the first communication lines N relay stations that connect and connect n slave stations of the second communication line in association with each other, and a master station connected to the first and second communication lines In a synchronization method of a communication system,
    During normal times, the master station communicates with n slave stations connected to the first communication line that is synchronized in advance using the first communication line;
    When a transmission failure occurs in the first communication line,
    The master station puts the relay device corresponding to the slave station connected to the first communication line before and after the transmission failure location into a relayable state, and the relay device and the second communication line Configuring a path to bypass communication to the first communication line via
    The master station transmitting resynchronization request information to a slave station connected to the first communication line;
    When a slave station connected to the first communication line receives the resynchronization request information, it calculates a transmission delay time caused by communication with the master station, and synchronizes with the master station based on the transmission delay time. And a slave station connected to the first communication line in the step transmits the transmission delay time calculated by receiving the resynchronization request information to the master station. The transmission delay time of each slave station connected to the first communication line possessed is updated using the transmission delay time received from the slave station, and the size of the transmission delay time of each slave station is determined in advance. Judging that all slave stations have been synchronized when the set arrangement order of slave stations is followed
    A synchronization method for a communication system.
  2. In the step of the master station transmitting resynchronization request information to a slave station connected to the first communication line,
    2. The communication system according to claim 1, wherein the master station transmits resynchronization request information to a slave station connected to the first communication line after the occurrence point when viewed from the master station. Synchronization method.
  3. a first communication line in which n (n ≧ 2) slave stations are connected in series, a second communication line in which n slave stations are connected in series, and n of the first communication lines N relay stations that connect and connect n slave stations of the second communication line in association with each other, and a master station connected to the first and second communication lines In a communication system,
    The master station includes a communication unit, and the failure point identification unit that identifies a fault point in a first communication line, a detour path forming portion constituting the path to bypass the failure point, the detour path forming section A synchronization request unit that transmits resynchronization request information to a slave station connected to the first communication line in response to the configuration of the detour path;
    The transmission delay time table that stores the slave station number and the transmission delay time in association with each other, the transmission delay time update unit that updates the transmission delay time table, and the distance between each slave station and the master station An arrangement order storage unit that stores an order determined based on the synchronization completion determination unit that determines that the synchronization of each slave station is completed,
    The slave station connected to the first communication line transmits the transmission delay time calculated by receiving the resynchronization request information to the master station,
    The transmission delay time update unit of the master station updates the transmission delay time table based on the transmission delay time received from the slave station,
    The synchronization completion determination unit of the master station is configured to arrange the slave stations in which the order of the transmission delay times of the slave stations stored in the updated transmission delay time table is stored in the arrangement order storage unit. If the order is followed, it is determined that all slave stations have been synchronized.
    A communication system characterized by the above.
  4. a first communication line in which n (n ≧ 2) slave stations are connected in series, a second communication line in which n slave stations are connected in series, and n of the first communication lines Connected to the first and second communication lines in a communication system comprising n relay apparatuses that associate and connect n slave stations of the second communication line and n slave stations of the second communication line. A master station,
    A communication unit, a failure point specifying unit that specifies a failure point in the first communication line, a detour path configuration unit that configures a route to bypass the failure point, and a synchronization request for requesting synchronization to the slave station A transmission delay time table that associates and stores a station number and a transmission delay time of the slave station, a transmission delay time update unit that updates the transmission delay time table, each of the slave stations, and the master station, An arrangement order storage unit that stores an order determined based on the distance of each, and a synchronization completion determination unit that determines that the synchronization of each slave station is completed,
    The detour path configuration unit makes the relay device corresponding to the slave station connected to the first communication line before and after the failure location identified by the failure location identification unit in a relayable state, and the relay device and Configuring a path to bypass communication to the first communication line via the second communication line;
    The synchronization request unit transmits resynchronization request information to a slave station connected to the first communication line in response to the detour path configuration unit configured a detour path,
    The transmission delay time update unit updates the transmission delay time table based on the transmission delay time received from the slave station in response to the transmitted resynchronization request information,
    The synchronization completion determination unit is configured such that the order of magnitude of the transmission delay time of each slave station stored in the updated transmission delay time table follows the arrangement order of the slave stations stored in the arrangement order storage unit. In addition, the master station determines that all slave stations have been synchronized.
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