KR101847366B1 - Time synchronization device and time synchronization system - Google Patents

Abstract

In the time synchronization device 300, the receiving unit 310 receives the first data 401 from the master device 200. [ After that, the transmitting unit 320 transmits the second data 402 to the master device 200. [ The correcting unit 340 corrects the reception time of the first data 401 and the transmission time of the second data 402 recorded using the slave clock 301 which is a software clock. The synchronizing unit 350 receives at least the transmission time of the first data 401 notified from the master device 200 and the reception time of the first data 401 corrected by the correcting unit 340, Which is a shift of the time between the master clock 201 and the slave clock 301 from the transmission time of the second data 402 corrected by the master device 200 and the reception time of the second data 402 notified from the master device 200, (405).

Description

Time synchronization device and time synchronization system

The present invention relates to a time synchronization device, a time synchronization system, and a time synchronization method.

In the PA (Process Automation) field, it has been promoted to realize wide-area smart communication by shifting from a closed network configuration to an open network configuration and applying new information technology. A concrete example is a smart grid. Precise time synchronization is required in order to simplify event synchronization and data correlation in the measurement and control of a plurality of devices.

In the closed network configuration, the time of a relatively small number of devices, such as several tens, is synchronized using a unique time synchronization method. The time synchronization precision is in microseconds. In order to increase the time synchronization accuracy, the time synchronization method is mainly implemented on a hardware basis.

As a time synchronization method that can be used in an open network configuration, the Institute of Electrical and Electronics Engineers (IEEE) has established a time synchronization standard IEEE 1588 using Ethernet (registered trademark). IEEE 1588 specifies a method of synchronizing the time by transmitting and receiving a synchronous frame in which time is recorded via a network. The IEEE 1588 implementation is divided into two types, hardware base implementation and software base implementation.

In the hardware base implementation, the time is recorded using the hardware time stamp function of the PHY that processes the physical layer of the OSI (Open Systems Interconnection) reference model (see, for example, Patent Document 1). Therefore, the time transmitter side records the time stamp when the PHY transmits the synchronous frame as the transmission time, and transmits the recorded transmission time. Similarly, the time receiver side records the time stamp when the PHY receives the synchronous frame as the reception time, and uses the recorded reception time in the application program. The time synchronization accuracy is theoretically 1 nanosecond, but actually it is up to 100 nanoseconds.

In the software base implementation, the time is recorded using the software time stamp function of the application program that performs processing of the application layer of the OSI reference model. Therefore, the time transmitter side records the time stamp when the application program instructs transmission of the synchronous frame to the lower process, as the transmission time, and transmits the recorded transmission time. Similarly, the time receiver side records the time stamp when the application program is notified of the reception of the synchronization frame from the lower process, as the reception time, and uses the recorded reception time in the application program. The time synchronization precision is degraded to about 100 milliseconds in the worst case. In addition, the time synchronization precision of the software base implementation greatly fluctuates depending on the OS (Operating System) in which the application program operates and the hierarchical structure of the communication function.

(Prior art document)

(Patent Literature)

(Patent Document 1) Japanese Unexamined Patent Publication No. 256965

When a system is changed from a closed network configuration to an open network configuration, the system is connected to another system. From the viewpoint of asset utilization, it is conceivable to use the existing time synchronization method for time synchronization in the system, and to use IEEE 1588 for time synchronization with the outside of the system. However, in this case, a terminal corresponding to both of the existing time synchronization method and IEEE 1588 is required. When IEEE 1588 is newly introduced, high-speed synchronization accuracy can be obtained by adopting hardware base mounting, but it is costly. Therefore, from the viewpoint of cost saving, it is preferable to employ a software base mounting.

An object of the present invention is to improve the time synchronization precision of the time synchronization method by software base implementation.

A clock synchronizing apparatus according to an aspect of the present invention includes: a receiving unit that receives first data from a master device having a master clock; and a second synchronizing unit that synchronizes the second data with the master device after the first data is received by the receiving unit A recording section for recording the reception time of the first data and the transmission time of the second data in the transmission section using a slave clock which is a software clock; And a control unit configured to control at least the transmission time of the first data at the master device notified from the master device and the transmission time of the first data corrected by the correcting unit 1 < / RTI > data, the transmission time of the second data corrected by the correction section, From the reception time of the second data in the master device that is notified from, and comprising a synchronizing master clock and calculating the deviation of the time offset of the slave clock.

In the present invention, since the time recorded using the software clock is corrected, the time synchronization precision of the time synchronization method by software base implementation is improved.

1 is a diagram showing an example of a configuration of a time synchronization system according to a first embodiment;
2 is a block diagram showing a configuration of a master device and a time synchronization device according to a first embodiment;
3 is a flowchart showing the operation of the time synchronization system according to the first embodiment;
4 is a flowchart showing the operation of the time synchronization system according to the first embodiment;
5 is a flowchart showing the operation of the time synchronization system according to the first embodiment;
6 is a block diagram showing an example of mounting of a master device and a time synchronization device according to the first embodiment;
7 is a sequence diagram showing a communication procedure between a master device and a time synchronization device according to the first embodiment;
8 is a diagram showing an example of the configuration of a time synchronization system according to the second embodiment;
9 is a diagram showing an example of a configuration of a time synchronization system according to a third embodiment;
10 is a diagram showing an example of a hardware configuration of a time synchronization device according to an embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or equivalent parts are denoted by the same reference numerals. In the description of the embodiments, the same or corresponding parts are appropriately omitted or simplified.

Embodiment Mode 1.

In the conventional time synchronization method based on software base mounting, there is a problem of deterioration of the time synchronization accuracy as described above. The cause of this problem is the asymmetry of the software timestamp fluctuation and the internal processing delay of the terminal in which the time synchronization is implemented. In the present embodiment, at least part of such factors are removed or suppressed by correcting the recorded value of time.

The present embodiment realizes time synchronization in a distributed system in which a plurality of devices exist by software base implementation. In the time synchronization method based on software base implementation according to the present embodiment, the principle of IEEE 1588 is used. This time synchronization method can be implemented in any terminal existing in the distributed system. The OS installed in the terminal is a real-time OS. The terminal on the time transmitting side is the master. The terminal on the visual receiving side is a slave and is a terminal for performing time synchronization.

Hereinafter, the configuration of the system according to the present embodiment, the operation of the system according to the present embodiment, and the effect of the present embodiment will be described in turn.

*** Description of configuration ***

An example of the configuration of the time synchronization system 100 which is a system according to the present embodiment will be described with reference to Fig.

The time synchronization system 100 is a distributed system. The time synchronization system 100 includes a GM 110 (Grand Master), a plurality of PLCs 120 (Programmable Logic Controllers), and a plurality of field devices 130,

In this example, a network topology in the form of a tree is employed. The GM 110 is the root and at least three PLCs 120 are connected to the GM 110 as lower nodes of the route. At least one PLC 120 or at least three field devices 130 are connected as lower nodes to form a sub-network.

The GM 110 provides a time reference. The first time synchronization method 101 is applied to the time synchronization between the GM 110 and the PLC 120 connected to the GM 110. [ The first time synchronization method 101 is a time synchronization method based on software base implementation according to the present embodiment and uses the principle of IEEE 1588. [ The procedure of time synchronization by the first time synchronization method 101 will be described later.

The second time synchronization method 102 is applied to the time synchronization in each sub-network. The second time synchronization method 102 is a unique time synchronization method of each sub-network. With respect to the procedure of the time synchronization by the second time synchronization method 102, an arbitrary procedure can be applied, and a description thereof will be omitted.

The PLC 120 connected to the GM 110 corresponds to the second time synchronization method 102 of each sub network and corresponds to the first time synchronization method 101. [

In addition, the number of PLCs 120 connected to the GM 110 and the configuration of each sub-network can be appropriately changed. The PLC 120 may be replaced by another type of device such as an NC (Numerical Controller).

The configuration of the master device 200 and the time synchronization device 300 according to the present embodiment will be described with reference to FIG.

The master device 200 has a master clock 201. The master clock 201 is not a hardware clock but a software clock. The hardware clock is a clock mounted on the hardware. The hardware clock is used for the hardware timestamp function. A software clock is a software-managed clock. The software clock is used for the software timestamp function.

The master device 200 includes a transmitting unit 210, a receiving unit 220, a recording unit 230, and a correcting unit 240.

The GM 110 shown in Fig. 1 is a terminal on the time transmitting side in the first time synchronization method 101, and corresponds to the master device 200. Fig.

The time synchronization device 300 has a slave clock 301. [ The slave clock 301, like the master clock 201, is not a hardware clock but a software clock.

The time synchronization device 300 includes a reception unit 310, a transmission unit 320, a recording unit 330, a correction unit 340, and a synchronization unit 350.

The PLC 120 connected to the GM 110 shown in FIG. 1 is a terminal on the side of the receiving side in the first time synchronization method 101 and corresponds to the time synchronization device 300.

The master device 200 and the time synchronization device 300 transmit and receive data to each other via the network 400 in accordance with the communication procedure of the first time synchronization method 101 described below. Thereby, the time synchronization apparatus 300 can adjust the time of the slave clock 301 to the time of the master clock 201. [

The transmitting unit 210 of the master device 200 transmits the first data 401 to the time synchronization device 300. [

The receiving unit 310 of the time synchronization device 300 receives the first data 401 from the master device 200. [

The transmitting unit 320 of the time synchronizing apparatus 300 transmits the second data 402 to the master device 200 after the receiving unit 310 receives the first data 401. [

The receiving unit 220 of the master device 200 receives the second data 402 from the time synchronization device 300.

The recording unit 230 of the master device 200 uses the master clock 201 to compare the transmission time of the first data 401 in the transmission unit 210 and the transmission time of the second data 402 in the reception unit 220 Record the reception time.

The correction unit 240 of the master device 200 corrects the transmission time of the first data 401 recorded by the recording unit 230 and the reception time of the second data 402. [

The transmitter 210 of the master device 200 transmits the third data 403 for notifying the time synchronization device 300 of the transmission time of the first data 401 corrected by the correction unit 240, At least the fourth data 404 for notifying the reception time of the second data 402 corrected by the correction unit 240. [ The transmission unit 210 notifies the time synchronization apparatus 300 of the transmission time of the first data 401 corrected by the correction unit 240 and the reception time of the second data 402 .

The receiving unit 310 of the time synchronization device 300 receives the third data 403 and the fourth data 404 from the master device 200. [

The recording unit 330 of the time synchronization device 300 uses the slave clock 301 to determine the reception time of the first data 401 in the reception unit 310 and the reception time of the second data 402 in the transmission unit 320. [ And the transmission time of the recording medium.

The correction unit 340 of the time synchronization device 300 corrects the reception time of the first data 401 and the transmission time of the second data 402 recorded by the recording unit 330. [

The synchronizing unit 350 of the time synchronizing apparatus 300 determines whether or not at least the transmission time of the first data 401 in the master device 200 notified from the master device 200, 1 data 401 and the transmission time of the second data 402 corrected by the correcting unit 340 and the transmission time of the second data 402 in the master device 200 notified from the master device 200 From the reception time, an offset 405 is calculated. The offset 405 is a time difference between the master clock 201 and the slave clock 301. The synchronizing unit 350 refers to the third data 403 and the fourth data 404 received by the receiving unit 310 when calculating the offset 405. [ That is, the synchronization unit 350 obtains the transmission time of the first data 401 in the master device 200 from the third data 403 received by the reception unit 310. [ The synchronization unit 350 obtains the reception time of the second data 402 in the master device 200 from the fourth data 404 received by the reception unit 310. [

In this embodiment, the third data 403 includes not only the transmission time of the first data 401 corrected by the correction unit 240 of the master device 200, but also the time of transmission of the first data 401 corrected by the correction unit 240 of the master device 200 230 of the first data 401 recorded in the first data 401. [ The fourth data 404 is used for notifying the reception time of the second data 402 corrected by the correcting unit 240 as well as the reception time of the second data 402 recorded by the recording unit 230 Data. That is, in the present embodiment, the transmitting unit 210 of the master device 200 transmits the time of transmission of the first data 401 recorded by the recording unit 230 and the time of the second data 402) is further notified. Therefore, when calculating the offset 405, the synchronizing unit 350 of the time synchronizing apparatus 300 determines the time of transmission of the first data 401 recorded by the recording unit 230 of the master device 200, Both of the transmission time of the first data 401 corrected by the correcting unit 240 of the apparatus 200 are transmitted to the master device 200 via the transmission of the first data 401 in the master device 200 It is used as time. The synchronizing unit 350 of the time synchronizing apparatus 300 calculates the offset 405 based on the reception time of the second data 402 recorded by the recording unit 230 of the master device 200, Both of the reception time of the second data 402 corrected by the correction unit 240 of the master device 200 and the reception time of the second data 402 of the master device 200 notified from the master device 200 .

In this embodiment, when calculating the offset 405, the synchronizing unit 350 not only records the reception time of the first data 401 corrected by the correcting unit 340, The reception time of the first data 401 is also used. The synchronizing unit 350 not only synchronizes the transmission time of the second data 402 corrected by the correcting unit 340 but also the second data recorded by the recording unit 330 when the offset 405 is calculated 402 is also used.

In other words, in this embodiment, the synchronizing unit 350 synchronizes the transmission time of the first data 401 recorded in the master device 200 with the transmission time of the first data 401 corrected in the master device 200 The time and the reception time of the first data 401 recorded by the recording unit 330 and the reception time of the first data 401 corrected by the correcting unit 340 and the second data 401 recorded by the recording unit 330 The transmission time of the second data 402 corrected by the correcting unit 340 and the reception time of the second data 402 recorded in the master device 200 and the transmission time of the second data 402 corrected by the correcting unit 340, From the reception time of the corrected second data 402, an offset 405 is calculated.

More specifically, the synchronization unit 350 calculates the sum of the transmission time of the first data 401 recorded by the master device 200 and the transmission time of the first data 401 corrected by the master device 200, The difference between the sum of the reception time of the first data 401 recorded by the recording unit 330 and the reception time of the first data 401 corrected by the correcting unit 340, The sum of the transmission time of the second data 402 and the transmission time of the second data 402 corrected by the correcting unit 340 and the sum of the transmission time of the second data 402 recorded in the master device 200 And the reception time of the second data (402) corrected by the master device (200).

The third data 403 may be data for notifying only the transmission time of the first data 401 recorded by the recording unit 230 of the master device 200. [ The fourth data 404 may be data for notifying only the reception time of the second data 402 recorded by the recording unit 230. [ Therefore, the master device 200 may not include the correcting unit 240. [

If the master device 200 does not include the correcting section 240 or if the correcting section 240 does not correct the transmission time of the first data 401 recorded by the recording section 230, The corrector 340 of the master device 300 may correct the transmission time of the first data 401 in the master device 200 notified from the master device 200. [ The synchronizing unit 350 of the time synchronizing apparatus 300 calculates the offset 405 based on the transmission time of the first data 401 in the master device 200 notified from the master device 200 In addition, the transmission time of the first data 401 corrected by the correction unit 340 can be used.

If the master device 200 does not include the correcting section 240 or if the correcting section 240 does not correct the time of receipt of the second data 402 recorded by the recording section 230, The correcting unit 340 of the master device 300 may correct the reception time of the second data 402 in the master device 200 notified from the master device 200. [ The synchronizer 350 of the time synchronizer 300 calculates the offset 405 based on the reception time of the second data 402 in the master device 200 notified from the master device 200 In addition, the reception time of the second data 402 corrected by the correction unit 340 can be used.

*** Description of operation ***

The operation of the time synchronization system 100 will be described with reference to Figs. 3, 4, and 5. Fig. The operation of the time synchronization system 100 corresponds to the time synchronization method according to the present embodiment.

Fig. 3 shows an operation related to transmission and reception of the first data 401. Fig. In the present embodiment, transmission and reception of the first data 401 are repeated.

In step S11, the transmitting section 210 of the master device 200 repeatedly transmits the first data 401 to the time synchronization apparatus 300. [

In step S12, the receiving section 310 of the time synchronization apparatus 300 repeatedly receives the first data 401 from the master device 200. [

In step S13, the recording unit 230 of the master device 200 uses the master clock 201 every time the first data 401 is transmitted by the transmitting unit 210, The transmission time of the first data 401 is recorded.

In step S14, the correcting unit 240 of the master device 200 generates a random number every time the transmission time of the first data 401 is recorded by the recording unit 230, and using the generated random number , And the correction value of the transmission time of the first data 401 recorded by the recording unit 230 is calculated.

The transmitting unit 210 of the master device 200 transmits data for notifying the time synchronization device 300 of the correction value of the transmission time of the first data 401 calculated by the correcting unit 240 As the third data 403.

In step S16, the receiving unit 310 of the time synchronization device 300 repeatedly receives the third data 403 from the master device 200. [

In step S17, the recording unit 330 of the time synchronization device 300 uses the slave clock 301 every time the first data 401 is received by the receiving unit 310, The reception time of the first data 401 is recorded.

In step S18, the correcting unit 340 of the time synchronization device 300 generates a random number every time the reception time of the first data 401 is recorded by the recording unit 330, and uses the generated random number And the correction value of the reception time of the first data 401 recorded by the recording unit 330 is calculated.

The synchronizing unit 350 of the time synchronizing apparatus 300 calculates the correction value of the reception time of the first data 401 calculated by the correcting unit 340 at the time of calculating the offset 405, As the reception time of the data 401.

Fig. 4 shows an operation related to transmission and reception of the second data 402. Fig. In the present embodiment, transmission and reception of the second data 402 are also repeated.

The transmitting section 320 of the time synchronizing apparatus 300 transmits the second data 402 to the master device 200 every time the receiving section 310 receives the first data 401 in step S21 do.

The receiving unit 220 of the master device 200 repeatedly receives the second data 402 from the time synchronization device 300 in step S22.

In step S23, the recording unit 230 of the master device 200 uses the master clock 201 every time the second data 402 is received by the receiving unit 220, The reception time of the second data 402 is recorded.

In step S24, the correcting unit 240 of the master device 200 generates a random number every time the reception time of the second data 402 is recorded by the recording unit 230, and using the generated random number , The correction value of the reception time of the second data 402 recorded by the recording unit 230 is calculated.

The transmission unit 210 of the master device 200 transmits data for notifying the time synchronization device 300 of the correction value of the reception time of the second data 402 calculated by the correction unit 240 As the fourth data 404.

In step S26, the receiving unit 310 of the time synchronization device 300 repeatedly receives the fourth data 404 from the master device 200. [

The recording unit 330 of the time synchronization device 300 in the step S27 uses the slave clock 301 every time the second data 402 is transmitted by the transmission unit 320 to the transmission unit 320 The transmission time of the second data 402 is recorded.

In step S28, the correcting unit 340 of the time synchronization device 300 generates a random number every time the transmission time of the second data 402 is recorded by the recording unit 330, and uses the generated random number And the correction value of the transmission time of the second data 402 recorded by the recording unit 330 is calculated.

The synchronizing unit 350 of the time synchronizing apparatus 300 calculates the correction value of the transmission time of the second data 402 calculated by the correcting unit 340 at the time of calculating the offset 405, And uses it as the transmission time of the data 402.

In this embodiment, as described above, the communication procedure for transmitting and receiving the first data 401, the second data 402, the third data 403, and the fourth data 404 one by one in order is repeated.

FIG. 5 shows an operation for calculating the offset 405. FIG.

In step S31, the synchronization unit 350 of the time synchronization device 300 calculates the offset 405 every time the first data 401 is received by the reception unit 310. [ That is, the synchronization unit 350 calculates one offset 405 for one communication procedure.

In step S32, the synchronization unit 350 of the time synchronization device 300 accumulates a plurality of calculated values of the offset 405. [ That is, the synchronization unit 350 accumulates two or more offsets 405 corresponding to two or more communication procedures.

In step S33, the synchronization section 350 of the time synchronization apparatus 300 performs statistical processing of the accumulated plurality of calculated values. The synchronization unit 350 adjusts the time of the slave clock 301 according to the result of the statistical process. Specifically, the synchronization section 350 adjusts the time of the slave clock 301 by using an average of the accumulated calculation values as a result of the statistical processing. As a result, the time of the master clock 201 and the time of the slave clock 301 are synchronized.

In this embodiment, as described above, the principle of IEEE 1588 is used. That is, the first data 401, the second data 402, the third data 403, and the fourth data 404 are transmitted and received as a synchronous frame. More specifically, the first data 401 is transmitted / received as a Sync message, the second data 402 is transmitted / received as a Follow_Up message, the third data 403 is transmitted / received as a Delay_Req message, Delay_Resp message.

Assuming that the delay of the one-way between the master device 200 and the time synchronization device 300 is half of the round trip delay, the reception time of the first data 401 recorded by the recording unit 330 and the reception time of the first data 401 recorded by the recording unit 330 The transmission time of the first data 401 recorded by the master device 200 and the transmission time of the first data 401 recorded by the master device 200, which are notified by the third data 403, from the sum of the reception times of the first data 401, And the transmission time of the second data 402 recorded in the master device 200, which is notified by the fourth data 404, and the reception time of the second data 402 recorded in the master device 200, The transmission time of the second data 402 recorded by the recording unit 330 and the transmission time of the second data 402 recorded by the correction unit 340 from the sum of the reception times of the second data 402 corrected by the master device 200 A value obtained by dividing the sum of the values obtained by subtracting the sum of the transmission times of the data 402 by 4 is a delay of one way. Then, from the sum of the reception time of the first data 401 recorded by the recording unit 330 and the reception time of the first data 401 corrected by the correcting unit 340, A value obtained by dividing a value obtained by subtracting the sum of the transmission time of the first data 401 and the transmission time of the first data 401 corrected by the master device 200 by 2 and a value obtained by dividing the second data From the sum of the reception time of the first data 402 and the reception time of the second data 402 corrected by the master device 200, the transmission time of the second data 402 recorded by the recording unit 330, ) Obtained by dividing the value obtained by dividing the value obtained by dividing the value obtained by subtracting the sum of the transmission times of the second data (402) corrected by the offset (405).

That is, the offset 405 is T_offset, the transmission time of the first data 401 recorded by the recording unit 230 of the master device 200 is T_m1, the correction value of T_m1 is T_m1 ' The reception time of the first data 401 recorded by the time synchronization unit 330 is T_s1, the correction value of T_s1 is T_s1 ', the transmission time of the second data 402 recorded by the recording unit 330 of the time synchronization device 300 T_m2 ', and the correction value of T_m2 is T_m2', the correction value of T_s2 and T_s2 is T_s2 ', the reception time of the second data 402 recorded by the recording unit 230 of the master device 200 is T_m2, T_s1 + T_s1 ') - (T_m1 + T_m1')) / 2 - ((T_s1 + T_s1 ') - (T_m1 + T_m1')) + T_m2 + T_m2 ' (T_m2 + T_m2 ') - (T_s2 + T_s2')) / 4 or T_offset = ((T_m2 + T_m2 ') - (T_s2 + T_s2 ')) / 2 - (((T_s1 + T_s1') - (T_m1 + T_m1 ')) + ((T_m2 + T_m2' T_s1 + T_s1 ') - (T_m1 + T_m1')) - ((T_m2 + T_m2 ') - (T_s2 + T_s2')) / 4. In step S31, the offset 405 can be obtained by using such a calculation formula.

A value obtained by subtracting the transmission time of the first data 401 notified by the third data 403 from the reception time of the first data 401 corrected by the correction unit 340 and a value obtained by subtracting the fourth data A value obtained by dividing the sum of values obtained by subtracting the transmission time of the second data 402 corrected by the correcting unit 340 from the reception time of the second data 402 notified by the transmission delay times 404 and 404 May be considered to be. In this case, a value obtained by subtracting the transmission time of the first data 401 notified by the third data 403 from the reception time of the first data 401 corrected by the correction unit 340, A value obtained by subtracting the delay of the one-way from the value obtained by subtracting the transmission time of the second data 402 corrected by the correcting unit 340 from the reception time of the second data 402 notified by the correction unit 404 Becomes an offset 405. [

That is, in step S31, T_offset = (T_s1'-T_m1 ') - ((T_s1'-T_m1') + T_m2'-T_s2 ') / 2 = T_m1 '- (T_m1' - T_m2 ') / 2 or T_offset = (T_m2'-T_s2') - ((T_s1'-T_m1 ') + '-T_s2')) / 2, the offset 405 may be obtained.

An example of mounting of the master device 200 and the time synchronization device 300 will be described with reference to Fig.

The functions of the receiving unit 310 and the transmitting unit 320 of the time synchronization device 300 are implemented in the PHY 302 and the MAC 303 (Media Access Control). The PHY 302 and the MAC 303 are hardware incorporated in the time synchronization apparatus 300. [ Specifically, the PHY 302 is a chip for processing the physical layer of the OSI reference model, and the MAC 303 is a chip for processing the data link layer of the OSI reference model. The PHY 302 and the MAC 303 may be integrated on the same chip.

Similarly, the functions of the transmitting unit 210 and the receiving unit 220 of the master device 200 are also implemented in the PHY 202 and the MAC 203. [ The PHY 202 is a chip for performing processing of the physical layer, and the MAC 203 is a chip for processing the data link layer.

The function of the recording unit 330 of the time synchronization device 300 is implemented in the MAC driver 304. [ The MAC driver 304 is software installed in the time synchronization device 300. Specifically, the MAC driver 304 is middleware used by the OS 305 to control and manipulate the MAC 303. The MAC driver 304 has a software time stamp function for generating a time stamp using the slave clock 301. [

Similarly, the function of the recording unit 230 of the master device 200 is also implemented in the MAC driver 204. [ The MAC driver 204 is middleware used by the OS 205 to control and manipulate the MAC 203. The MAC driver 204 has a software time stamp function for generating a time stamp using the master clock 201. [

The functions of the correction unit 340 and the synchronization unit 350 of the time synchronization device 300 are implemented in the time synchronization application 306. [ The time synchronization application 306 is software installed in the time synchronization device 300. [ Concretely, the time synchronization application 306 is an application program operating on the OS 305 together with another application 307. [ The time synchronization application 306 manages a correction table 308 for correcting the variation of the time stamp generated by the MAC driver 304. [

Likewise, the function of the correction unit 240 of the master device 200 is also implemented in the time synchronization application 206. [ The time synchronization application 206 is an application program operating on the OS 205 together with other applications 207. [ The time synchronization application 206 manages the correction table 208 for correcting the variation of the time stamp generated by the MAC driver 204. [

The master device 200 for transmitting time and the time synchronization device 300 for synchronizing time have the same hierarchical structure with respect to time synchronization. This hierarchical structure is composed of an application layer corresponding to the OSes 205 and 305 and the time synchronization applications 206 and 306, a data link layer corresponding to the MAC drivers 204 and 304 and MACs 203 and 303, a PHY 202 , 302 corresponding to the physical layer. As described above, in the time synchronization protocol according to the present embodiment, the data link layer is directly accessed from the application layer without changing the transport layer and the network layer of the OSI reference model.

Operations of the master device 200 and the time synchronization device 300 in the example shown in Fig. 6 will be described with reference to Fig.

In step S41 in which the master device 200 transmits a Sync message as a synchronization frame, the time synchronization application 206 generates a synchronization frame that is a Sync message. The time synchronization application 206 does not store the time in this synchronization frame. When the time synchronization application 206 detects that a synchronous frame is generated, the OS 205 activates a priority interrupt and inputs the synchronous frame to the MAC driver 204 before another frame. The MAC driver 204 generates the software time stamp at the time when the synchronization frame is input, thereby recording the transmission time T_m1 of the synchronization frame. Thereafter, the MAC driver 204 inputs the synchronization frame to the MAC 203. [ The MAC 203 transmits the synchronization frame from the PHY 202. [ The MAC driver 204 feeds back the recorded transmission time T_m1 to the time synchronization application 206. [ The time synchronization application 206 stores the transmission time T_m1 fed back from the MAC driver 204 in the first column among the blank columns of the first row of the correction table 208. [ The time synchronization application 206 generates a random number according to the normal distribution and stores the generated random number in the same column in the second row of the correction table 208. [ The time synchronization application 206 corrects the variation of the transmission time T_m1 by subtracting the random number stored in the second row of the correction table 208 from the transmission time T_m1 stored in the first row of the correction table 208. [ The time synchronization application 206 stores the corrected transmission time T_m1 'in the same column of the third row of the correction table 208. [ The transmission time T_m1 may be corrected by another method such as adding a random number to the transmission time T_m1 instead of subtracting the random number from the transmission time T_m1. In addition, it is possible to appropriately change the transmission time T_m1, the random number, and the corrected transmission time T_m1 'in which number of the second row of the correction table 208 is stored.

In step S51 in which the time synchronization apparatus 300 receives the Sync message as a synchronization frame, the PHY 302 receives the synchronization frame from the master apparatus 200. [ The PHY 302 inputs the received synchronization frame to the MAC 303. The MAC driver 304 generates a software time stamp at the time when it detects that a synchronization frame has been input to the MAC 303, thereby recording the reception time T_s1 of the synchronization frame. Thereafter, the MAC driver 304 immediately inputs the recorded reception time T_s1 to the time synchronization application 306. Then, The time synchronization application 306 stores the reception time T_s1 input from the MAC driver 304 in the first column among the blank columns of the first row of the correction table 308. [ The time synchronization application 306 generates a random number according to the normal distribution and stores the generated random number in the same column of the second row of the correction table 308. [ The time synchronization application 306 corrects the variation in the reception time T_s1 by subtracting the random number stored in the second row of the correction table 308 from the reception time T_s1 stored in the first row of the correction table 308. [ The time synchronization application 306 stores the corrected reception time T_s1 'in the same column of the third row of the correction table 308. [ The reception time T_s1 may be corrected by another method such as adding a random number to the reception time T_s1 instead of subtracting the random number from the reception time T_s1. In addition, it is possible to appropriately change the reception time T_s1, the random number, and the corrected reception time T_s1 'to what number of the subsequent rows of the correction table 308 are stored.

In step S42, in which the master device 200 transmits a Follow_Up message as a synchronization frame, the time synchronization application 206 generates a synchronization frame which is a Follow_Up message. The time synchronization application 206 stores in the synchronization frame the values before and after the correction stored in the last column of the set of corrected transmission times T_m1 and T_m1 'before correction and stored in the first and third rows of the correction table 208, The set transmission time T_m1, T_m1 ', that is, the corrected transmission time T_m1, T_m1' of the immediately preceding Sync message. When the time synchronization application 206 detects that a synchronous frame is generated, the OS 205 activates a priority interrupt and inputs the synchronous frame to the MAC driver 204 before another frame. The MAC driver 204 generates a software time stamp at the time when a synchronization frame is input. However, the MAC driver 204 detects that the synchronization frame is a Follow_Up message, and does not feed back the generated time stamp to the time synchronization application 206, only maintaining the generated time stamp in the buffer or the like for a predetermined time. Thereafter, the MAC driver 204 inputs the synchronization frame to the MAC 203. [ The MAC 203 transmits the synchronization frame from the PHY 202. [

In step S52 at which the time synchronization device 300 receives the Follow_Up message as a synchronization frame, the PHY 302 receives the synchronization frame from the master device 200. [ The PHY 302 inputs the received synchronization frame to the MAC 303. The MAC driver 304 generates a software time stamp at a point in time when it detects that a synchronization frame is input to the MAC 303. [ However, the MAC driver 304 detects that the synchronization frame is a Follow_Up message, and does not input the generated time stamp to the time synchronization application 306, which is maintained for a predetermined time in the buffer or the like. Thereafter, the MAC driver 304 inputs the synchronization frame to the time synchronization application 306 via the OS 305. [ The time synchronization application 306 detects that the synchronization frame input from the MAC driver 304 is a Follow_Up message, and extracts the pre-correction and corrected transmission times T_m1 and T_m1 'stored in the synchronization frame.

In step S53 in which the time synchronization apparatus 300 transmits a Delay_Req message as a synchronization frame, the time synchronization application 306 generates a synchronization frame which is a Delay_Req message. The time synchronization application 306 does not store the time in this synchronous frame. When the time synchronization application 306 detects that a synchronous frame is generated, the OS 305 activates a priority interrupt and inputs the synchronous frame to the MAC driver 304 before another frame. The MAC driver 304 generates a software time stamp at the point in time when the synchronous frame is input, thereby recording the synchronous frame transmission time T_s2. After that, the MAC driver 304 inputs the synchronization frame to the MAC 303. [ The MAC 303 transmits the synchronization frame from the PHY 302. [ The MAC driver 304 feeds back the recorded transmission time T_s2 to the time synchronization application 306. [ The time synchronization application 306 stores the transmission time T_s2 fed back from the MAC driver 304 in the first column among the empty columns of the fourth row of the correction table 308. [ The time synchronization application 306 generates a random number according to the normal distribution and stores the generated random number in the same column of the fifth row of the correction table 308. [ The time synchronization application 306 corrects the variation in the transmission time T_s2 by subtracting the random number stored in the fifth row of the correction table 308 from the transmission time T_s2 stored in the fourth row of the correction table 308. [ The time synchronization application 306 stores the corrected transmission time T_s2 'in the same column of the sixth row of the correction table 308. [ The transmission time T_s2 may be corrected by another method such as adding a random number to the transmission time T_s2 instead of subtracting the random number from the transmission time T_s2. In addition, it is possible to appropriately change the transmission time T_s2, the random number, and the corrected transmission time T_s2 'in which rows of the correction table 308 are stored.

In step S43, in which the master device 200 receives the Delay_Req message as a synchronization frame, the PHY 202 receives the synchronization frame from the time synchronization device 300. [ The PHY 202 inputs the received synchronization frame to the MAC 203. The MAC driver 204 generates a software time stamp at the time of detecting that the MAC frame 203 is input to the MAC 203, thereby recording the reception time T_m2 of the synchronization frame. Thereafter, the MAC driver 204 immediately inputs the recorded reception time T_m2 to the time synchronization application 206. [ The time synchronization application 206 stores the reception time T_m2 inputted from the MAC driver 204 in the first column among the empty columns in the fourth row of the correction table 208. [ The time synchronization application 206 generates a random number according to the normal distribution and stores the generated random number in the same column of the fifth row of the correction table 208. [ The time synchronization application 206 corrects the variation in the reception time T_m2 by subtracting the random number stored in the fifth row of the correction table 208 from the reception time T_m2 stored in the fourth row of the correction table 208. [ The time synchronization application 206 stores the corrected reception time T_m2 'in the same column of the sixth row of the correction table 208. [ The reception time T_m2 may be corrected by another method such as adding a random number to the reception time T_m2 instead of subtracting the random number from the reception time T_m2. In addition, it is possible to appropriately change the reception time T_m2, the random number, and the corrected reception time T_m2 'in which number of the second row of the correction table 208 is stored.

In step S44, in which the master device 200 transmits a Delay_Resp message as a synchronization frame, the time synchronization application 206 generates a synchronization frame which is a Delay_Resp message. The time synchronization application 206 stores in the synchronization frame the values of the pre-correction values stored in the fourth row and the sixth row of the correction table 208 and the pre-correction values stored in the last column of the corrected set of the reception times T_m2 and T_m2 ' And stores the set reception times T_m2 and T_m2 ', that is, the corrected reception times T_m2 and T_m2' of the immediately preceding Delay_Req message. When the time synchronization application 206 detects that a synchronous frame is generated, the OS 205 activates a priority interrupt and inputs the synchronous frame to the MAC driver 204 before another frame. The MAC driver 204 generates a software time stamp at the time when a synchronization frame is input. However, the MAC driver 204 detects that the synchronization frame is a Delay_Resp message, holds the generated time stamp in a buffer or the like for a predetermined time, and does not feed back to the time synchronization application 206. [ Thereafter, the MAC driver 204 inputs the synchronization frame to the MAC 203. [ The MAC 203 transmits the synchronization frame from the PHY 202. [

In step S54 in which the time synchronization apparatus 300 receives the Delay_Resp message as a synchronization frame, the PHY 302 receives the synchronization frame from the master device 200. [ The PHY 302 inputs the received synchronization frame to the MAC 303. The MAC driver 304 generates a software time stamp at a point in time when it detects that a synchronization frame is input to the MAC 303. [ However, the MAC driver 304 detects that the synchronization frame is a Delay_Resp message, and does not input the generated time stamp to the time synchronization application 306, which is maintained for a predetermined time in the buffer or the like. Thereafter, the MAC driver 304 inputs the synchronization frame to the time synchronization application 306 via the OS 305. [ The time synchronization application 306 detects that the synchronization frame inputted from the MAC driver 304 is a Delay_Resp message, and extracts the pre-correction and corrected reception times T_m2 and T_m2 'stored in the synchronization frame.

After step S54, the time synchronization application 306 determines whether or not the correction before and after the correction, which are stored in the first and third rows of the correction table 308 in step S51 and the corrected reception times T_s1 and T_s1 ' Corrected transmission times T_s2 and T_s2 'stored in the fourth and sixth rows of the correction table 308 in step S53 and the corrected transmission times T_s2 and T_s2' T_m2, and T_m2 ', the offset 405 is calculated. As a calculation formula, T_offset = (((T_s1 + T_s1 ') - (T_m1 + T_m1')) - - ((T_s1 + T_s1 ') - (T_m1 + T_m1') - ((T_m2 + T_m2 ') - (T_s2 + T_s2')) / 4 may be used.

Thereafter, the procedure from step S41 to step S44 and the procedure from step S51 to step S54 are repeated.

*** Explanation of effects ***

In this embodiment, since the time recorded using the software clock is corrected, the time synchronization accuracy of the time synchronization method by the software base implementation is improved.

Embodiment 2:

The difference from the first embodiment will mainly be described with respect to this embodiment.

An example of the configuration of the time synchronization system 100 according to the present embodiment will be described with reference to Fig.

In this example, the same network topology as the example shown in Fig. 1 is adopted.

In the first embodiment, the second time synchronization method 102 is applied to the time synchronization in all the subnetworks. In this embodiment, the first time synchronization method 101 is used for the time synchronization within some subnetworks .

Therefore, some PLCs 120 among the PLCs 120 connected to the GM 110 are also terminals on the time transmitting side in the first time synchronization method 101, and are connected to the master device 200 and the time synchronization And corresponds to both sides of the apparatus 300. Fig. The field device 130 connected to a part of the PLC 120 is a terminal on the side of the receiving side in the first time synchronization method 101 and corresponds to the time synchronization device 300. [

The configuration and operation of the master device 200 and the time synchronization device 300 according to the present embodiment are the same as those of the first embodiment.

Embodiment 3

The difference from the first embodiment will mainly be described with respect to this embodiment.

An example of the configuration of the time synchronization system 100 according to the present embodiment will be described with reference to Fig.

In this example, a network topology in the form of a line is partially adopted. Three PLCs 120 are connected in series to the GM 110. [ At least one PLC 120 or at least two field devices 130 are connected to these three PLCs 120, and a tree-shaped sub-network is constituted.

The first time synchronization method 101 is applied to the time synchronization between the GM 110 and the PLC 120 connected in series with the GM 110. [ The first time synchronization method 101 is also applied to the time synchronization between the PLCs 120 serially connected to the GM 110. [

Therefore, among the PLCs 120 connected in series to the GM 110, the two intermediate PLCs 120 are terminals on the time transmitting side in the first time synchronization method 101, and are connected to the master device 200 And the time synchronizing apparatus 300, respectively. As described above, in the present embodiment, the master function is distributed to the GM 110 and the two PLCs 120.

Of the PLCs 120 connected in series to the GM 110, the two intermediate PLCs 120 are not the terminals on the time transmitting side in the first time synchronization method 101, ) And the other PLC 120 may be merely transmitted. In this case, the two intermediate PLCs 120 correspond to the time synchronization device 300 only. As described above, in the present embodiment, the master function can be changed into a form integrated with the GM 110. [

The configuration and operation of the master device 200 and the time synchronization device 300 according to the present embodiment are the same as those of the first embodiment.

Hereinafter, an example of the hardware configuration of the time synchronization apparatus 300 according to the embodiment of the present invention will be described with reference to FIG.

The time synchronization device 300 is a computer. The time synchronization device 300 includes hardware such as a processor 901, an auxiliary memory device 902, a memory 903, a communication device 904, an input interface 905, and a display interface 906. The processor 901 is connected to other hardware through a signal line 910 and controls these other hardware. The input interface 905 is connected to the input device 907. The display interface 906 is connected to the display 908.

The processor 901 is an IC (Integrated Circuit) that performs processing. The processor 901 is, for example, a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or a GPU (Graphics Processing Unit).

The auxiliary storage device 902 is a recording medium such as a ROM (Read Only Memory), a flash memory, or an HDD (Hard Disk Drive).

The memory 903 is, for example, a RAM (Random Access Memory).

The communication device 904 includes a receiver 921 for receiving data and a transmitter 922 for transmitting data. The communication device 904 is, for example, a communication chip or a NIC (Network Interface Card).

The input interface 905 is a port to which the cable 911 of the input device 907 is connected. The input interface 905 is, for example, a USB (Universal Serial Bus) terminal.

Display interface 906 is the port to which cable 912 of display 908 is connected. The display interface 906 is, for example, a USB terminal or an HDMI (registered trademark) (High Definition Multimedia Interface) terminal.

The input device 907 is, for example, a mouse, a touch pen, a keyboard, or a touch panel.

The display 908 is, for example, an LCD (Liquid Crystal Display).

The auxiliary storage device 902 stores a program for realizing a function of "subsection" called a receiving section 310, a transmitting section 320, a recording section 330, a correcting section 340 and a synchronizing section 350. This program is loaded into the memory 903, read by the processor 901, and executed by the processor 901. [ In the auxiliary storage device 902, an OS is also stored. At least a part of the OS is loaded into the memory 903, and the processor 901 executes a program for realizing the function of "sub" while executing the OS.

In Fig. 10, one processor 901 is shown, but the time synchronization apparatus 300 may include a plurality of processors 901. Fig. A plurality of processors 901 may cooperatively execute a program for realizing the " sub-function ".

Information indicating the result of the processing of " part " and data and signal values and variable values are stored in the auxiliary memory device 902, the memory 903, or a register in the processor 901 or a cache memory.

Quot; part " may be provided as a " circuit tree ". Also, the term " part " may be read by switching to " circuit " or " process " Circuit " and " circuit tree " include not only the processor 901, but also other kinds of processing circuits, such as a logic IC, a gate array (GA), an application specific integrated circuit (ASIC), and a field-programmable gate array .

The hardware configuration shown in Fig. 10 can also be applied to the master device 200 according to the embodiment of the present invention.

Although the embodiment of the present invention has been described above, some of these embodiments may be combined. Alternatively, any one or several of these embodiments may be partially implemented. For example, in the description of the embodiment, any one of the components described as " part " may be employed, or any combination of several may be employed. The present invention is not limited to these embodiments, and various modifications are possible as needed.

100: Time synchronization system
101: First time synchronization method
102: Second time synchronization method
110: GM
120: PLC
130: Field device
200: Master device
201: Master Clock
202: PHY
203: MAC
204: MAC driver
205: OS
206: Time Synchronization Application
207: Other applications
208: correction table
210:
220:
230:
240:
300: time synchronization device
301: Slave clock
302: PHY
303: MAC
304: MAC driver
305: OS
306: Time Synchronization Application
307: Another application
308: correction table
310:
320:
330:
340:
350: Synchronization
400: Network
401: first data
402: second data
403: Third data
404: fourth data
405: Offset
901: Processor
902: Auxiliary storage
903: Memory
904: Communication device
905: input interface
906: Display Interface
907: Input device
908: Display
910: Signal line
911: Cable
912: Cable
921: Receiver
922: Transmitter

Claims (11)

A receiver for receiving first data from a master device having a master clock;
A transmitting unit that transmits second data to the master device after the first data is received by the receiving unit;
A recording unit for recording the reception time of the first data and the transmission time of the second data in the transmission unit using the slave clock which is a software clock,
Corrects the reception time of the first data recorded by the recording unit using a random number according to the normal distribution and corrects the transmission time of the second data recorded by the recording unit using a random number according to the normal distribution However,
A sum of a transmission time of the first data recorded in the master device notified from the master device and a transmission time of the first data corrected using a random number in accordance with a normal distribution in the master device, A difference between a reception time of the first data and a reception time of the first data corrected by the correction unit and a difference between a transmission time of the second data recorded by the recording unit and a correction time The second data being corrected using the sum of the transmission time of the second data transmitted from the master device and the reception time of the second data recorded by the master device notified from the master device, From the difference between the master clock and the time of the slave clock, Calculating synchronization
And a time synchronization unit.
The method according to claim 1,
Wherein the receiving unit repeatedly receives the first data from the master device,
Wherein the recording unit records the reception time of the first data at the reception unit every time the first data is received by the reception unit,
Wherein the correction section generates a random number according to the normal distribution every time the reception time of the first data is recorded by the recording section and uses the generated random number to receive the first data recorded by the recording section The correction value of the time is calculated,
Wherein the synchronizing unit uses the correction value of the reception time of the first data calculated by the correcting unit as the reception time of the first data when calculating the offset
Time synchronization device.
3. The method of claim 2,
Wherein the transmitting unit transmits the second data to the master device every time the first data is received by the receiving unit,
Wherein the recording unit records the transmission time of the second data at the transmission unit every time the second data is transmitted by the transmission unit,
Wherein the correction unit generates a random number according to the normal distribution every time the transmission time of the second data is recorded by the recording unit and uses the generated random number to transmit the second data recorded by the recording unit The correction value of the time is calculated,
And the synchronization unit uses the correction value of the transmission time of the second data calculated by the correcting unit as the transmission time of the second data when calculating the offset
Time synchronization device.
3. The method of claim 2,
Wherein the synchronizing unit calculates the offset each time the first data is received by the receiving unit, accumulates a plurality of calculated values of the offset, performs statistical processing on the stored plurality of calculated values, To adjust the time of the slave clock.
5. The method of claim 4,
Wherein the synchronization unit uses the average of the accumulated calculation values as a result of the statistical processing to adjust the time of the slave clock.
The method according to claim 1,
The receiving section receives from the master device third data for notifying the master device of the transmission time of the first data and fourth data for notifying the reception time of the second data in the master device and,
Wherein the synchronizing unit refers to the third data and the fourth data received by the receiving unit when calculating the offset
Time synchronization device.
A time synchronization device according to any one of claims 1 to 6,
A transmission time of the first data and a reception time of the second data are recorded by using a master clock which is a software clock and the transmission time of the first data and the reception time of the second data are corrected, The master device notifies the synchronizing apparatus of the transmission time of the first data recorded and the reception time of the second data and the transmission time of the corrected first data and the reception time of the second data,
And the time synchronization system. delete delete delete delete

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