JP2013175852A - Time synchronization system, master unit, slave unit, time synchronization method and time synchronization program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a synchronization pull-in time at an initial activation of a slave unit.SOLUTION: A time synchronization system 1 has a master unit 10 and a slave unit 20. The slave unit 20 has a synchronous state determination part 21 which determines whether the time synchronous state of the slave unit 20 is stable or not, and a transmission part 22 which sends a stable state notification message to the master unit 10 via a network 3 when the time synchronous state is determined to be stable by the synchronous state determination part 21. The master unit 10 has a receiving part 12 which receives the stable state notification message from the slave unit 20, and a priority change part 11 which decreases a time correction message transmission priority for the slave part 20 when the receiving part 12 receives the stable state notification message.

Description

  The present invention relates to a time synchronization system, a master device, a slave device, a time synchronization method, and a time synchronization program, and in particular, a time synchronization system, a master device, a slave device, and a time synchronization method for synchronizing the time of a slave device with the time of a master device. And a time synchronization program.

  As a time synchronization method for a system using a network such as Ethernet (registered trademark), a method based on the IEEE 1588 standard is known. For example, Patent Document 1 describes a related time synchronization method using the IEEE 1588 standard. The IEEE 1588 standard is a PTP (Precision Time Protocol) standard, and communication of a time packet (a packet for performing time synchronization stipulated in the IEEE 1588 standard) from a master device to a slave device makes the time of the slave device a master device. This is a method of synchronizing with the time.

  FIG. 6 shows a related time synchronization method for performing time synchronization between the master device and the slave device by PTP.

  First, the master device sends a Sync message to the slave device at the master time “00:00” (S101). The slave device receives the Sync message at the slave time “00:06” and stores this reception time. The Sync message is broadcast from the master device to a plurality of slave devices.

  Next, the master device sends a Follow_up message to the slave device to notify that the Sync message has been sent at the master time “00:00” (S102). By receiving the Follow_up message from the master device, the slave device acquires the master time “00:00” at which the Sync message was transmitted.

  Since the master device transmits the Sync message at the master time “00:00” and the slave device receives the Sync message at the slave time “00:06”, by subtracting “00:00” from “00:06”, It is determined that the offset time difference between the master time and the slave time is “00:06”. Then, the offset time difference “00:06” is subtracted from the current slave time “00:08”, and the slave time after the offset is set to “00:02” to adjust the time of the slave device (S103).

  Next, in order to obtain the propagation delay time between the master device and the slave device, the slave device sends a Delay_request message to the master device at the slave time “00:06”, and stores this transmission time (S104). . The master device receives the Delay_request message from the slave device at the master time “00:12”. Then, the master device sends a Delay_response message for notifying that the Delay_request message has been received at the master time “00:12” to the slave device that has transmitted the Delay_request message (S105). The slave device acquires the master time “00:12” at which the Delay_request message is received by receiving the Delay_response message from the master device.

  Since the slave device transmits the Delay_request message at the slave time “00:06” and the master device receives the Delay_request message at the master time “00:12”, the value obtained by subtracting “00:06” from “00:12” By setting the value to 1/2, it is determined that the propagation delay time between the master and the slave is “00:03”. Then, the propagation delay time “00:03” is added to the current slave time “00:15”, and the slave time after the offset and propagation delay time correction is set to “00:18”. S106). As described above, time synchronization between the master device and the slave device is performed.

JP 2010-197320 A

  In the case of a system having a network configuration of a master device and a plurality of slave devices in the IEEE 1588 system implemented as described above, the time synchronization accuracy of the slave device is generally large in the number of times of time packet communication with the master device. It improves.

  Therefore, if the number of times of communication of the time packet with the master device exceeds a certain level, the subsequent packet communication with the master device is performed as a role for maintaining the time synchronization state rather than the role of time correction.

  However, some of the slave devices that exist for a single master device are stable for a long time because the power is not turned off for a long time after the power is turned on. In some cases, the time correction operation is frequently performed by pulling in the time synchronization at the time of initial startup.

  In the case of such a master-slave configuration, if the master device sends out the Delay_response message in the order received in response to the Delay_request message received from a plurality of slave devices, it is in the initial startup among the plurality of slave devices. For this slave device, the time correction processing for time synchronization is delayed, and as a result, the synchronization pull-in time after the initial activation is delayed.

  The synchronization pull-in is to synchronize the time of the slave device and the master device, and the synchronization pull-in time is the time until the time of the slave device and the master device is synchronized.

  As described above, the related time synchronization method has a problem that the synchronization pull-in time at the initial startup in the slave device may be delayed. An object of the present invention is to provide a time synchronization system, a master device, a slave device, a time synchronization method, and a time synchronization program that solve such problems.

  The time synchronization system according to the present invention is a time synchronization system that synchronizes the time of a slave device with the time of the master device by a time correction message transmitted from the master device via a network, and the slave device A synchronization state determination unit that determines whether or not the time synchronization state of the slave device is a stable state, and when the synchronization state determination unit determines that the time synchronization state is the stable state, a stable state notification message is sent to the network. A transmission unit that transmits to the master device via the master device, the master device receiving the stable state notification message from the slave device, and the reception unit receives the stable state notification message A priority changing unit that lowers the transmission priority of the time correction message to the slave device; And it has a.

  A master device according to the present invention is a master device provided in a time synchronization system that synchronizes the time of a slave device with the time of the master device by a time correction message transmitted from the master device via a network, and the slave device A receiving unit that receives a stable state notification message indicating that the synchronization state of the device is a stable state from the slave device, and when the receiving unit receives the stable state notification message, the time correction message for the slave device A priority changing unit that lowers the transmission priority.

  The slave device according to the present invention is a slave device provided in a time synchronization system that synchronizes the time of the slave device with the time of the master device by a time correction message transmitted from the master device via the network, A synchronization state determination unit that determines whether or not the time synchronization state of the device is a stable state, and when the synchronization state determination unit determines that the time synchronization state is the stable state, a stable state notification message is transmitted via the network. And a transmission unit for transmitting to the master device.

  The time synchronization method according to the present invention is a time synchronization method for synchronizing the time of a slave device with the time of the master device by a time correction message transmitted from the master device via a network, wherein the slave device It is determined whether or not the time synchronization state of the slave device is a stable state, and if the slave device determines that the time synchronization state is the stable state, a stable state notification message is sent to the master device via the network. And when the master device receives the stable state notification message from the slave device and the master device receives the stable state notification message, the transmission priority of the time correction message to the slave device is lowered. It is something to be made.

  The time synchronization program according to the present invention causes a time synchronization system to execute time synchronization processing for synchronizing the time of a slave device with the time of the master device by a time correction message transmitted from the master device via a network. In the time synchronization process, the slave device determines whether or not the time synchronization state of the slave device is a stable state, and the slave device determines that the time synchronization state is the stable state. A stable state notification message is transmitted to the master device via the network, the master device receives the stable state notification message from the slave device, and the master device receives the stable state notification message. The transmission priority of the time correction message to the slave device is reduced. Is shall.

  According to the present invention, it is possible to provide a time synchronization system, a master device, a slave device, a time synchronization method, and a time synchronization program that can shorten the synchronization pull-in time at the time of initial startup in the slave device.

It is a block diagram for demonstrating the characteristic of the time synchronization system which concerns on this invention. It is a block diagram which shows schematic structure of the time synchronization system which concerns on Embodiment 1 of this invention. It is a block diagram which shows the function structure of the time synchronization system which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the time synchronization system which concerns on Embodiment 1 of this invention. It is a sequence diagram which shows operation | movement of the time synchronization system which concerns on Embodiment 1 of this invention. It is a sequence diagram which shows the related time synchronization method.

(Features of the present invention)
Prior to the description of the embodiment of the present invention, the outline of the features of the present invention will be described with reference to FIG.

  As shown in FIG. 1, the time synchronization system 1 according to the present invention includes a master device (master node) 10 and a slave device (slave node) 20 connected via a network 3. The time synchronization system 1 is a system that synchronizes the slave time of the slave device 20 with the master time of the master device 10 by a time correction message (such as a Delay_response message) transmitted from the master device 10 via the network 3.

  When the slave device 20 determines that the time synchronization state is the stable state and the synchronization state determination unit 21 that determines whether or not the time synchronization state is the stable state, and the synchronization state determination unit 21 determines that the time synchronization state is the stable state, And a transmission unit 22 that transmits an Announce message or the like) to the master device 10 via the network 3. In addition, the master device 10 receives the stable state notification message from the slave device 20, and when receiving the stable state notification message by the receiving unit 12, the time correction message for the slave device 20 that has transmitted the stable state notification message. And a priority changing unit 11 that lowers the transmission priority.

  According to the present invention, when the slave device is in the time synchronization stable state, the slave device transmits a stable state notification message, and the master device reduces the transmission priority of the time correction message in accordance with the stable state notification message. The communication process of the device is preferentially executed. Thereby, priority can be given to the communication processing with respect to the slave apparatus in the initial activation, and the synchronization pull-in time at the initial activation can be shortened.

(Embodiment 1 of the present invention)
Embodiment 1 of the present invention will be described below with reference to the drawings. First, the configuration of the time synchronization system 1 according to the first embodiment of the present invention will be described using FIG. 2 and FIG. FIG. 2 shows a schematic configuration of the time synchronization system 1. The example of FIG. 2 is a configuration example in which the master device 10 is connected to x slave devices 20 (20_1 to 20_x).

  The master device 10 and the slave device 20 are connected by a path 30, and the master device 10 performs time synchronization with the slave devices 20_1 to 20_x by PTP using the paths 30_1 to 30_x, respectively. That is, the configuration of the network that connects the master device 10 and the slave device 20 is not limited as long as the master device 10 and the slave device 20 can communicate via the path 30.

  In the present embodiment, there are two types of transmission modes for the Delay_response message transmitted from the master device 10 to the slave device 20: a normal mode and a synchronous stable mode. The normal mode is a mode that immediately responds to the Delay_request message received from the slave device 20, and the synchronization stable mode is lower than the Delay_request message received from the slave device 20 whose time synchronization state is stable for a long time. This mode corresponds to the priority. A normal mode or a synchronous stable mode is set for each slave device 20.

  FIG. 3 shows a functional block configuration of the time synchronization system 1 according to the first embodiment of the present invention. The master device 10 and the plurality of slave devices 20 are connected via the network 3. The plurality of slave devices 20 all have the same configuration. The master device 10 and the slave device 20 may include a CPU (Central Processing Unit), a storage device, a communication interface, and the like, and each functional configuration may be realized by the CPU executing a time synchronization program.

  The master device 10 includes a clock generation unit 101, a master clock unit 102, a message processing unit 103, and a message transmission / reception unit 104.

  The clock generation unit 101 generates a reference clock for the master device 10. The master clock unit 102 generates a master time that is the time of the master device 10 based on the reference clock generated by the clock generation unit 101. For example, the master clock unit 102 is a time stamp counter that counts according to a reference clock.

  The message processing unit 103 performs message processing for performing time synchronization with the slave device in accordance with the IEEE 1588 (PTP) standard. For example, the message processing unit 103 generates a Sync message and a Follow_up message for transmission to the slave device 20 at startup and periodically. Further, when the message processing unit 103 receives a Delay_request message from the slave device 20, the message processing unit 103 generates a Delay_response message.

  The message processing unit 103 according to the present embodiment corresponds to the priority changing unit 11 in FIG. 1, and when receiving an Announce message indicating a long-term stable state from the slave device 20, sets the message processing priority of the slave device 20. The message processing of the other slave device 20 is preferentially executed. In particular, the priority of the transmission process of the Delay_response message with respect to the reception of the Delay_request message is changed as will be described later.

  The message transmission / reception unit 104 transmits the message generated by the message processing unit 103 to the slave device 20 via the network 3 and notifies the message processing unit 103 of the message received from the slave device 20 via the network 3.

  The slave device 20 includes a clock generation unit 201, a slave clock unit 202, a message processing unit 203, a clock correction unit 205, and a message transmission / reception unit 204.

  The clock generation unit 201 generates a reference clock for the slave device 20. The slave clock unit 202 generates a slave time that is the time of the slave device 20 based on the reference clock generated by the clock generation unit 201. For example, the slave clock unit 202 is a time stamp counter that counts according to a reference clock.

  The message processing unit 203 performs message processing for performing time synchronization with the master device in accordance with the IEEE 1588 (PTP) standard. For example, when the message processing unit 203 receives a Sync message or a Follow_up message from the master device 10, the message processing unit 203 calculates an offset and notifies the clock correction unit 205 of the offset. Further, the message processing unit 203 generates a Delay_request message, calculates a delay time when receiving the Delay_response message from the master device 10, and notifies the clock correction unit 205 of the delay time.

  The message processing unit 203 of the present embodiment corresponds to the synchronization state determination unit 21 in FIG. 1, determines whether or not the synchronization state of the slave device 20 is a long-term stable state, and if it is determined to be a long-term stable state, an Announce message is output. Generate.

  The clock correction unit 205 corrects the slave time of the slave clock unit 202 based on the offset and delay time calculated by the message processing unit 203. As a result, the clock correction unit 205 synchronizes the slave time with the master time.

  The message transmission / reception unit 204 transmits the message generated by the message processing unit 203 to the master device 10 via the network 3 and notifies the message processing unit 203 of the message received from the master device 10 via the network 3.

  Next, the operation of the time synchronization system 1 according to the first embodiment of the present invention will be described using FIG. 4 and FIG. FIG. 4 shows an example of a time synchronization method executed by the master device 10 and the slave device 20 of the time synchronization system 1.

  First, when the slave device 20 is activated, the slave device 20 synchronizes time with the master device 10 by PTP, and enters a state of time synchronization (S201). Here, the slave device 20_1 is in a state immediately after the power is turned on and immediately before the time synchronization is stabilized for a long time, and the slave device 20_x is in the state of being initially activated and performing a time correction operation for time synchronization. In addition, it is assumed that the other slave devices 20 are time-synchronized and stable for a long time, and time packet communication with the master device 10 is being performed for confirmation of the time-synchronized state.

  Next, the slave device 20 determines whether or not the time synchronization with the master device 10 is in the long-term stable state (S202). For example, the slave device 20 determines the long-term stable state when the synchronization state continues for a predetermined period such as one week or one month. Whether or not the state is stable can be determined by the reception interval and the number of receptions of the Sync message (synchronization message) received by the slave device 20. For example, as a determination criterion for the slave device 20 to be in a synchronized long-term stable state, the time interval for receiving a Sync message periodically transmitted from the master device 10 is continuously within an arbitrary time range for a long period of time. The time interval for receiving the Sync message periodically transmitted from the master device 10 may be within a predetermined time range as long as it exceeds an arbitrary number of times. This is because, since the synchronization state is maintained by receiving the Sync message, it can be determined that the synchronization state is stable if the Sync message can be received within a predetermined range.

  In S202, when the slave device 20 determines that the time synchronization state is not stable for a long period of time, nothing is notified from the slave device 20 to the master device 10, so the master device 10 processes the Delay_response message in the normal mode. (S203). That is, in the normal mode, when receiving the Delay_request message from the slave device 20, the master device 10 immediately transmits a Delay_response message to the slave device 20.

  In S202, when the slave device 20_1 determines that the time synchronization state has continued and has become a long-term stable state, the slave device 20_1 transmits an Announce message that notifies the master device 10 that the long-term stable state has been achieved. (S204).

  When the master device 10 receives the Announce message from the slave device 20_1, the master device 10 switches the transmission mode of the Delay_response message to the slave device 20_1 from the normal mode to the synchronous stable mode (S205). That is, in the synchronous stable mode, after receiving the Delay_request message from the slave device 20_1, the master device 10 preferentially executes the processing of the other slave devices 20, and sends the Delay_response to the slave device 20_1 in a time delayed from the normal mode. Send a message.

  This makes it possible to delay the time packet communication with the master device 10 from the normal operation for the slave device 20_1 whose time synchronization has been in a stable state for a long time. Thus, it becomes possible to perform time packet communication with the master device 10 preferentially for the slave device 20_x that is performing the time correction.

  FIG. 5 shows a specific operation example of the time synchronization method in the time synchronization system 1 according to the first embodiment of the present invention.

  First, the slave device 20 and the master device 10 perform time synchronization according to the IEEE 1588 standard. Specifically, as in FIG. 6, a sync message (S301), a Follow_up message (S302), a Delay_request message (S303), and a Delay_response message (S304) are periodically repeated between the master device 10 and the slave device 20. The slave time is corrected by being transmitted and received, and the master time and the slave time are synchronized.

  Then, when the Sync message (S305) and the Follow_up message (S306) are transmitted from the master device 10, the slave device 20 determines the time synchronization state (S307, corresponding to S202 in FIG. 4). When it is determined that the long-term stable state is established based on the reception interval of the Sync message or the like, the slave device 20 transmits an Announce message indicating the long-term stable state to the master device 10 (S308, corresponding to S204 in FIG. 4). When receiving the Announce message, the master device 10 switches the transmission mode of the Delay_response message in the slave device 20 that has transmitted the Announce message to the synchronous stable mode (corresponding to S309 and S205 in FIG. 4).

  Next, the slave device 20 transmits a Delay_request message to the master device 10 (S310). The master device 10 delays the Delay_response message because the slave device that has transmitted the Delay_request message is in the synchronous stable mode (S311). The master device 10 preferentially executes message processing of the other slave devices 20, and then transmits a Delay_response message to the slave device 20 in the long-term stable state (S312).

  As described above, in the present embodiment, when the slave device is in a long-term stable state, a message indicating the synchronization stable state is transmitted to the master device, and the master device delays the order of sending the Delay_response message to the slave device. I did it. Thereby, there exists an effect as described below.

  The first effect is that the master device side determines the sending order of the Delay_response message to the slave device by transmitting a message indicating the synchronization stable state to the master device in accordance with the Delay_request message from the slave device. Thus, the time packet communication with the master device can be prioritized over the slave device that is initially activated, and the synchronization pull-in time at the initial activation can be shortened.

  The second effect is that the load on the network can be reduced by reducing the number of packet communications between the slave device and the master device whose time synchronization has been stabilized for a long time within an arbitrary time.

(Another embodiment of the present invention)
In the first embodiment, the transmission timing of the Delay_response message in the master device 10 is adjusted. However, in addition to the first embodiment, the transmission timing of the Delay_request message in the slave device 20 may be further adjusted.

  For example, when the slave device detects a long-term stable state of time synchronization, the transmission interval of the Delay_request message may be increased. In addition, the master device may detect the long-term stable state of the slave device and specify that the transmission interval of the Delay_request message is increased for the slave device.

  By increasing the sending interval of the Delay_request message from the slave device, the number of time packet communication processes between the master device and a plurality of slave devices is reduced. As a result, priority is given to the time packet communication processing to the slave device that is initially activated. Can be performed. Therefore, the synchronization pull-in time can be further shortened and the network load can be reduced.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, in the above example, the Follow_up message is transmitted following the Sync message. However, the Sync_message may be synchronized only without transmitting the Follow_up message.

DESCRIPTION OF SYMBOLS 1 Time synchronization system 3 Network 10 Master apparatus 11 Priority change part 12 Reception part 20 (20_1-20_x) Slave apparatus 21 Synchronization state determination part 22 Transmission part 30 (30_1-30_x) Path 101 Clock generation part 102 Master clock part 103 Message Processing unit 104 Message transmission / reception unit 201 Clock generation unit 202 Slave clock unit 203 Message processing unit 204 Message transmission / reception unit 205 Clock correction unit

Claims (10)

A time synchronization system that synchronizes the time of the slave device with the time of the master device by a time correction message transmitted from the master device via the network,
The slave device is
A synchronization state determination unit that determines whether or not the time synchronization state of the slave device is a stable state;
A transmission unit that transmits a stable state notification message to the master device via the network when the synchronization state determination unit determines that the time synchronization state is the stable state;
The master device is
A receiver that receives the stable state notification message from the slave device;
A priority changing unit that lowers the transmission priority of the time correction message to the slave device when the receiving unit receives the stable state notification message,
Time synchronization system. The synchronization state determination unit determines that the slave device is in the stable state when the time synchronization state of the slave device is stable for a predetermined period;
The time synchronization system according to claim 1. The synchronization state determination unit determines that the synchronization state is the stable state when a reception interval of synchronization messages received from the master device is continuously within a predetermined range.
The time synchronization system according to claim 2. The synchronization state determination unit determines that the synchronization state is the stable state when the number of times the reception interval of the synchronization message received from the master device is within a predetermined range is a predetermined number of times.
The time synchronization system according to claim 2. When the time synchronization state is the stable state, the transmission unit increases the transmission interval of the time request message for requesting the time correction message.
The time synchronization system according to any one of claims 1 to 4. The time correction message is a Delay_response message of the IEEE 1588 standard.
The time synchronization system according to any one of claims 1 to 5. A master device provided in a time synchronization system that synchronizes the time of a slave device with the time of the master device by a time correction message transmitted from the master device via a network,
A receiving unit that receives a stable state notification message from the slave device indicating that the synchronization state of the slave device is a stable state;
A priority changing unit that lowers the transmission priority of the time correction message to the slave device when the receiving unit receives the stable state notification message,
Master device. A slave device provided in a time synchronization system that synchronizes the time of the slave device with the time of the master device by a time correction message transmitted from the master device via the network,
A synchronization state determination unit that determines whether or not the time synchronization state of the slave device is a stable state;
A transmission unit that transmits a stable state notification message to the master device via the network when the synchronization state determination unit determines that the time synchronization state is the stable state;
Slave device. A time synchronization method for synchronizing the time of the slave device with the time of the master device by a time correction message transmitted from the master device via the network,
The slave device determines whether the time synchronization state of the slave device is a stable state,
When it is determined that the time synchronization state is the stable state, the slave device transmits a stable state notification message to the master device via the network,
The master device receives the steady state notification message from the slave device;
When the master device receives the stable state notification message, the transmission priority of the time correction message to the slave device is reduced.
Time synchronization method. A time synchronization program for causing a time synchronization system to execute time synchronization processing for synchronizing the time of a slave device with the time of the master device by a time correction message transmitted from the master device via a network, wherein the time synchronization processing is ,
The slave device determines whether the time synchronization state of the slave device is a stable state,
When it is determined that the time synchronization state is the stable state, the slave device transmits a stable state notification message to the master device via the network,
The master device receives the steady state notification message from the slave device;
When the master device receives the stable state notification message, the transmission priority of the time correction message to the slave device is reduced.
Time synchronization program.

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