KR20220026479A - Information processing apparatus, information processing system, and information processing method - Google Patents

Abstract

The present invention relates to an information processing apparatus, information processing system, and information processing method. Provided is a technology which is able to suppress the transmission and the reception of a packet between devices and increase the precision of time synchronization. A communication means (25) of the information processing apparatus (20) receives a time maintaining packet transmitted by an external apparatus (10) having a second counter (11) measuring the reference time, and a transmission time when the external apparatus (10) has transmitted the time maintaining packet, which is measured by the second counter (11), from the external apparatus (10). The information processing apparatus (20) comprises: a calculating means (26) calculating the difference between the reception time when a time maintaining packet measured by a first counter (21) is received and the transmission time; a first correcting means (26) correcting the counter value of the first counter (21) by the difference; a determining means (28) determining the timing for correcting the counter value of the first counter based on the difference; and a second correcting means (28) secondarily correcting the counter value of the first counter at the determining timing.

Description

INFORMATION PROCESSING APPARATUS, INFORMATION PROCESSING SYSTEM, AND INFORMATION PROCESSING METHOD

Cross-referencing of related applications

This application claims the priority of Japanese Patent Application No. 2020-142149 (filed on August 25, 2020), The whole indication of this application is taken in here for reference.

The present disclosure relates to an information processing apparatus, an information processing system, and an information processing method.

In control devices such as a programmable logic controller (PLC), a temperature controller, and a recorder, time synchronization is performed between devices.

Patent Document 1 describes a technique related to time synchronization between devices.

Japanese Patent Laid-Open No. 2019-101480

However, in the conventional configuration, in order to increase the time synchronization accuracy, it is necessary to transmit and receive packets more frequently between devices. Moreover, it was not always possible to increase the precision of time synchronization.

An object of the present disclosure is to provide an information processing apparatus, an information processing system, and an information processing method capable of increasing the precision of time synchronization while suppressing transmission and reception of packets between devices.

An information processing apparatus according to some embodiments is an information processing apparatus comprising: a first counter for measuring time by counting up a counter value at a constant time period; and a communication unit, wherein the communication unit measures a reference time receiving the time keeping packet transmitted by the external device having a second counter to a calculation means for calculating a difference between a reception time at which the packet for time maintenance received from the external device and measured by the first counter and the transmission time; first correction means for correcting a value; determining means for determining a timing for correcting the counter value of the first counter based on the difference; and at the determined timing, correcting the counter value of the first counter and second correction means. In this way, the information processing apparatus suppresses transmission and reception of packets between devices in order to automatically correct the counter value of the first counter at the correction timing determined based on the difference between the transmission and reception times of the time keeping packets. , it becomes possible to increase the precision of time synchronization.

In one embodiment, the communication means receives, from the external device, a correction period for performing drift correction, and the communication means, at a time interval of the correction period, the time keeping packet and Upon receiving the transmission time of the time keeping packet, the calculation means calculates the difference in response to receiving the transmission time of the time keeping packet and the time keeping packet from the external device, and the determining means determines, as the timing, a time period determined by a value obtained by dividing the correction period by the number of counts of the first counter corresponding to the difference, as the timing, according to the calculation means calculating the difference; at the determined timing, corrects only the counter value of the first counter by 1. In this way, in the time period determined by the value obtained by dividing the correction period in which the drift correction is performed by the information processing apparatus by the number of counts of the first counter corresponding to the difference between the transmission and reception times of the packet for time maintenance, the counter of the first counter The value is automatically corrected to 1 only. Therefore, it becomes possible for the information processing apparatus to perform high-precision time synchronization according to the resolution of the first counter without frequent communication with the external apparatus.

In one embodiment, the communication means transmits a second time keeping packet to the external device in response to the difference calculated by the calculation means being less than a predetermined value, and the communication means includes: receiving, from the external device, a reception time at which the external device received the second time keeping packet, measured by a second counter, and wherein the calculating means includes the second time measured by the first counter. calculates a second difference that is a difference between a transmission time at which the maintenance packet is transmitted and a reception time at which the external device receives the second time maintenance packet, wherein the correction means is configured to: The counter value of the first counter is corrected. For example, the correction means may correct the counter value of the first counter by a value of 1/2 of the second difference. In this way, since the information processing apparatus corrects the counter value of the first counter based on the difference between the transmission and reception times of the second time keeping packets, correcting the time shift resulting from the communication delay with the external apparatus is it becomes possible

An information processing system according to some embodiments includes: a first counter for measuring time by counting up a counter value at a fixed time period; and a second information processing device including a second counter and second communication means. The second communication means of the second information processing apparatus transmits a time keeping packet to the first information processing apparatus, and the first communication means of the first information processing apparatus enables the second information processing apparatus to Upon receiving the transmitted time keeping packet, the second communication means of the second information processing device processes the first information at the transmission time at which the time keeping packet was transmitted, measured by the second counter. and the first communication means of the first information processing device receives a transmission time at which the second information processing device transmits the time keeping packet, and the first information processing device includes: calculating means for calculating a difference between the reception time and the transmission time at which the packet for maintaining the time measured by one counter is received, and a timing for correcting the counter value of the first counter based on the difference determining means; and correcting means for correcting the counter value of the first counter at the determined timing. In this way, the first information processing apparatus automatically corrects the counter value of the first counter at the correction timing determined based on the difference between the transmission and reception times of the packet for time maintenance, so that transmission and reception of packets between devices is performed. It becomes possible to raise the precision of time synchronization while suppressing.

An information processing method according to some embodiments is an information processing method of an information processing apparatus including a first counter for measuring time by counting up a counter value at a fixed time period, and a communication unit, wherein the communication unit includes: receiving the time keeping packet transmitted by the external device having a second counter for measuring the The transmission time is received from the external device, and the calculation means calculates a difference between the reception time and the transmission time at which the packet for maintaining the time measured by the first counter is received, and the first correction means comprises: Based on the difference, the counter value of the first counter is corrected, the determining unit determines a timing for correcting the counter value of the first counter based on the difference, and the second correction unit determines the determined timing. In , the counter value of the first counter is corrected. In this way, since the information processing apparatus automatically corrects the counter value of the first counter at the correction timing determined based on the difference between the transmission and reception times of the time keeping packets, suppressing transmission and reception of packets between devices. , it becomes possible to increase the precision of time synchronization.

According to the present disclosure, it is possible to provide an information processing apparatus, an information processing system, and an information processing method capable of increasing the accuracy of time synchronization while suppressing transmission and reception of packets between devices.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the structural example of the time synchronization system which concerns on one Embodiment of this indication.
Fig. 2 is a diagram showing an operation example of a time synchronization system according to an embodiment of the present disclosure.
3 is a diagram showing the configuration of a time synchronization system according to a comparative example.

<Comparative example>

3 : is a figure which shows the structure of the time synchronization system 9 which concerns on a comparative example. In the configuration of FIG. 3 , the time synchronization system 9 includes a device A 80 and a device B 90 . The device A80 includes a time counter 81 , a transmission time holding unit 82 , a reception time holding unit 83 , a packet transmission unit 84 , and a packet receiving unit 85 . The device B90 includes a time counter 91 , a transmission time holding unit 92 , a reception time holding unit 93 , a packet sending unit 94 , a packet receiving unit 95 , and a difference calculating unit 96 . be prepared The packet 71 transmitted from the packet transmitter 84 of the device A80 to the device B90 is received by the packet receiver 95 of the device B90. The packet 72 transmitted from the packet transmission unit 94 of the device B 90 to the device A 80 is received by the packet reception unit 85 of the device A 80 . The time counter 81 of the device A80 is a reference counter, and in the time synchronization system 9, the time counter 91 of the device B90 is set as the time counter of the device A80. A process for synchronizing according to (81) is performed.

The time counter 81 of the device A80 and the time counter 91 of the device B90 are both counters based on an independent oscillation source, and operate asynchronously. When the counter 81 for time and the counter 91 for time are synchronized, the difference in time can be corrected by transmitting and receiving packets between devices as in IEEE1588, for example. The processing procedure for such time synchronization is the same as the following operations 191 to 198.

(Act 191)

The device A80 transmits the packet 71 for time maintenance from the packet transmission unit 84 to the device B90. The device B90 receives the packet 71 for time maintenance in the packet receiving unit 95 .

(Action 192)

The device A80 holds the packet transmission time, which is the time at which the packet 71 for time maintenance was transmitted from the packet transmission unit 84 , in the transmission time holding unit 82 . The device B90 holds the packet reception time, which is the time at which the packet 71 for time maintenance was received in the packet reception unit 95 , in the reception time holding unit 93 .

(Action 193)

The device A80 transmits the packet 71 indicating the packet transmission time held in the transmission time holding unit 82 in operation 192 from the packet transmission unit 84 to the device B90. The device B90 receives the packet 71 indicating the packet transmission time in the packet receiving unit 95 .

(Act 194)

The difference calculation unit 96 of the device B90 calculates the packet reception time held by the reception time holding unit 93 in operation 192 and the packet 71 received from the device A80 in operation 193 Calculate the difference between packet transmission times represented by . The difference calculation part 96 correct|amends the counter 91 for time with the calculated difference.

(Act 195)

The device B90 transmits the packet 72 for time maintenance from the packet transmitter 94 to the device A80. The device A80 receives the packet 72 for time maintenance in the packet receiving unit 85 .

(Act 196)

The device A80 holds the packet reception time, which is the time at which the packet 72 for time maintenance was received in the packet reception unit 85 , in the reception time holding unit 83 . The device B90 holds the packet transmission time, which is the time at which the packet 72 for time maintenance is transmitted from the packet transmission unit 94 , in the transmission time holding unit 92 .

(Act 197)

The device A80 transmits the packet 71 indicating the packet reception time held in the reception time holding unit 83 in operation 196 from the packet transmission unit 84 to the device B90. The device B90 receives the packet 71 indicating the packet transmission time in the packet receiving unit 95 .

(Act 198)

The difference calculation unit 96 of the device B90 calculates the packet transmission time held by the transmission time holding unit 92 in operation 196 and the packet 71 received from the device A80 in operation 197. Calculate the difference between packet reception times represented by . The difference calculation unit 96 calculates a delay time by communication between devices based on the calculated difference, and corrects the time counter 91 with the delay time.

Time synchronization by the above-described processing has the following problems.

First, in both the time counter 81 of the device A80 and the time counter 91 of the device B90, drift due to the frequency deviation of the oscillation source occurs. Therefore, the counter 81 for time and the counter 91 for time need to be corrected regularly. The frequency of correction needs to be increased as the visual precision increases. For example, when the precision of the time counter is 50 ppm (parts per million), an error of 50 μs occurs per second. In order to maintain this time counter with an accuracy of 1 μs, at least 50 corrections must be performed per second. Therefore, frequent correction is required to increase the precision, and for that purpose, it is necessary to increase the frequency (number of times) of packet transmission and reception.

In addition, after correcting the shift of the time counter 91 of the device B90 in operation 194, until the delay time due to communication between the devices is corrected in operation 198, the time counter due to drift deviation occurs. Therefore, in the above method, time synchronization cannot necessarily be performed with high precision.

<Embodiment of the present disclosure>

The present disclosure aims to increase the accuracy of time synchronization without increasing the frequency of correction. EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of this indication is described with reference to drawings. In each figure, the same code|symbol is attached|subjected to the same or corresponding part. In description of this embodiment, description is abbreviate|omitted or simplified as appropriate about the same or corresponding part.

(Configuration of time synchronization system)

1 : is a figure which shows the structural example of the time synchronization system 1 which concerns on one Embodiment of this indication. In the example of FIG. 1 , the time synchronization system 1 as an information processing system includes a device A 10 as an external device or a second information processing device, and a device B 20 as a first information processing device. The device A10 includes a time counter 11 as a second counter, a transmission time holding unit 12 , a reception time holding unit 13 , a packet transmitting unit 14 , and a packet receiving unit 15 . The packet transmission unit 14 and the packet reception unit 15 of the device A10 function as first communication means. The device B 20 includes a time counter 21 as a first counter, a transmission time holding unit 22, a reception time holding unit 23, a packet transmitting unit 24, a packet receiving unit 25, a difference calculating unit ( 26 ), a correction period holding unit 27 , and a drift correction unit 28 . The packet transmission unit 24 and the packet reception unit 25 of the device B 20 function as second communication means.

The time counter 11 of the device A10 is a counter for measuring the reference time. In the time synchronization system 1, the process which synchronizes the counter 21 for time of the device B20 with the counter 11 for time of the device A10 is performed. The time counter 11 measures the time by counting up the counter value at a constant time period corresponding to a predetermined resolution (eg, 1 ns).

The transmission time holding part 12 is a holding part which holds the time when the device A10 transmitted the packet for time maintenance to the device B20. The reception time holding unit 13 is a holding unit that holds the time when the device A 10 received the packet for time maintenance from the device B 20 . The transmission time holding unit 12 and the reception time holding unit 13 hold the time measured by the time counter 11 of the device A10 . The packet transmitter 14 is a transmitter that transmits a packet to the device B20. The packet receiving unit 15 is a receiving unit that receives a packet from the device B 20 .

The counter 21 for time of the device B20 is a counter synchronized with the counter 11 for time of the device A10. The time counter 21 measures the time by counting up the counter value at a constant time period corresponding to a predetermined resolution (eg, 1 ns).

The transmission time holding part 22 is a holding part which holds the time when the device B20 transmitted the packet for time maintenance to the device A10. The reception time holding unit 23 is a holding unit that holds the time when the device B20 received the packet for time maintenance from the device A10 . The transmission time holding unit 22 and the reception time holding unit 23 hold the time measured by the time counter 21 of the device B20 . The packet transmission unit 24 is a transmission unit that transmits a packet to the device A10 . The packet receiving unit 25 is a receiving unit that receives a packet from the device A10 .

The difference calculation unit 26 as the calculation means and the first correction means is measured by the device B20 and the transmission time measured by the device A10 of the packet for time maintenance transmitted by the device A10 Calculate the difference between the received reception times, etc. The correction period holding unit 27 is a holding unit that holds a drift correction period, which will be described later. The drift correction unit 28 as the determining means and the second correction means includes the drift correction period, the transmission time measured by the device A 10 and the device B ( 20), the drift correction timing is calculated based on the difference between the measured reception times. The drift correction part 28 performs drift correction which correct|amends the counter value of the counter 21 for time by one count in a drift correction timing.

Each packet 31 transmitted from the packet transmission unit 14 of the device A 10 to the device B 20 is received by the packet reception unit 25 of the device B 20 . Each packet 32 transmitted from the packet transmission unit 24 of the device B 20 to the device A 10 is received by the packet reception unit 15 of the device A 10 .

(Processing sequence of the time synchronization system)

In the above configuration, the packet transmission unit 14 of the device A10 transmits a packet for time keeping to the device B20. The packet reception unit 25 of the device B20 receives the packet for time maintenance transmitted by the device A10. Moreover, the packet transmission part 14 of the device A10 transmits to the device B20 the transmission time measured by the counter 11 for time and which transmitted the packet for time maintenance. The packet receiving unit 25 of the device B20 receives the transmission time at which the device A10 transmitted the packet for time maintenance. The difference calculation unit 26 of the device B 20 calculates a difference between the reception time at which the packet for time maintenance measured by the time counter 21 is received, and the transmission time received from the device A 10 . . The difference calculation part 26 correct|amends the counter value of the counter 21 for time with this difference. The drift correction unit 28 of the device B20 determines the timing for correcting the counter value of the time counter 21 based on the calculated difference. The drift correction part 28 correct|amends the counter value of the counter 21 for time. Thus, the apparatus B20 correct|amends automatically the counter value of the counter 21 for time in the correction timing determined based on the difference of the transmission/reception time of the packet for time maintenance. Therefore, according to the device B20, it becomes possible to improve the precision of time synchronization, suppressing the transmission/reception of the packet in between devices.

The processing procedure of time synchronization in the time synchronization system 1 is the same as the following operations 110 to 140. The information processing method according to the present embodiment is realized when each device included in the time synchronization system 1 performs the following processing.

○ Action 110

The device A 10 transmits a correction cycle packet 31 indicating a drift correction cycle from the packet transmission unit 14 to the device B 20 . The drift correction period is a time interval (correction period) for performing operations 121 to 127 (referred to as "drift correction") to be described later. The device B20 receives the correction period packet 31 in the packet receiving unit 25 , and holds the drift correction period indicated by the correction period packet 31 in the correction period holding unit 27 .

○ Action 120

The device A 10 and the device B 20 repeatedly execute the following operations 121 to 127 at time intervals of the drift correction period indicated by the correction period packet 31 . Among these operations, operations 121 to 124 are the same as operations 191 to 194 of the comparative example. Further, the device B 20 executes the operation 128 in parallel with the operations 121 to 127 .

(Action 121)

The device A10 transmits the packet 31 for time maintenance from the packet transmitter 14 to the device B20. The device B20 receives the packet 31 for time maintenance in the packet receiving unit 25 .

(Action 122)

The device A10 holds in the transmission time holding unit 12 the packet transmission time, which is the time at which the packet 31 for time maintenance was transmitted from the packet transmission unit 14 in operation 121 . The packet transmission time is measured by the counter value of the counter 11 for time. Specifically, for example, the packet transmission unit 14 notifies the transmission time keeping unit 12 that the packet 31 for time maintenance to the device B20 has been transmitted. Thereby, the transmission time holding part 12 acquires and holds the time from the counter 11 for time.

The device B20 holds the packet reception time, which is the time at which the packet 31 for time maintenance was received in the packet reception unit 25 , in the reception time holding unit 23 . The packet reception time is measured by the counter value of the counter 21 for time. Specifically, for example, the packet reception unit 25 notifies the reception time maintenance unit 23 that the packet 31 for time maintenance has been received from the device A10 . Thereby, the reception time holding unit 23 acquires and holds the time from the counter 21 for time.

(Action 123)

The device A10 transmits the packet 31 indicating the packet transmission time held by the transmission time holding unit 12 in operation 122 from the packet transmission unit 14 to the device B20 . The device B20 receives the packet 31 indicating this packet transmission time in the packet reception unit 25 .

(Act 124)

The difference calculation unit 26 of the device B20 calculates the packet reception time held by the reception time holding unit 23 in operation 122 and the packet 31 received from the device A10 in operation 123 . Calculate the difference between packet transmission times represented by . The difference calculation part 26 correct|amends the counter value of the counter 21 for time with the calculated difference.

(Action 125)

The drift correction unit 28 of the device B 20 acquires the drift correction period from the correction period holding unit 27 .

(Act 126)

The drift correction unit 28 of the device B 20 acquires the difference calculated in operation 124 from the difference calculation unit 26 . The drift correction unit 28 calculates the accumulated value each time a difference is acquired. 0 is set as the initial value of the accumulated value. Accordingly, when the difference calculated in operation 124 is acquired for the first time, the accumulated value becomes the value of the difference.

(Act 127)

The drift correction unit 28 of the device B 20 divides the drift correction period acquired in the operation 125 by the number of counts of the time counter 21 corresponding to the difference accumulated in the operation 126, so that the drift correction timing (1 count) difference between sugars). The drift correction timing is when the time counter 11 of the device A 10 and the time counter 21 of the device B 20 deviate by one count of the time counter 21 (for example, 1 ns) It is equivalent to the time required to

(Action 128)

In parallel with the operations 121 to 127, the drift correction unit 28 of the device B 20 corrects the counter 21 for time by only one count for each drift correction timing. The larger the accumulated difference value, the shorter the drift correction timing. Thereby, the error of the counter 11 for time of the device A10 and the counter 21 for time of the device B20 is corrected larger. As a result, the difference obtained from the difference calculation unit 26 becomes a positive or negative value close to zero. As a result, the accumulated value of the difference is corrected so as to approach the same value as the error of the time counter 21, and finally converges to zero.

○ Action 130

The device B20 performs the following operations 131 to 134 after the difference obtained by the drift correction unit 28 from the difference calculation unit 26 is sufficiently close to zero. The device B20 may, for example, determine whether a difference obtained by a predetermined value (threshold value) is less than or not according to the obtained precision, and when it is determined that it is less than, the operations 131 to 134 may be performed. These operations 131 to 134 are the same as operations 195 to 198 of the comparative example.

(Action 131)

The device B20 transmits the packet 32 for time maintenance from the packet transmitter 24 to the device A10. The device A10 receives the packet 32 for time maintenance in the packet receiving unit 15 .

(Action 132)

The device A10 holds the packet reception time, which is the time at which the packet 32 for time maintenance was received in the packet reception unit 15 , in the reception time holding unit 13 . The packet reception time is measured by the counter value of the counter 11 for time. Specifically, for example, the packet reception unit 15 notifies the reception time maintenance unit 13 that the packet 32 for time maintenance has been received from the device B 20 . Thereby, the reception time holding unit 13 acquires and holds the time from the counter 11 for time.

The device B20 holds, in the transmission time holding unit 22 , the packet transmission time, which is the time at which the packet 32 for time maintenance is transmitted from the packet transmission unit 24 . The packet transmission time is measured by the counter value of the counter 21 for time. Specifically, for example, the packet transmission unit 24 notifies the transmission time keeping unit 22 that the packet 31 for time maintenance to the device A10 has been transmitted. Thereby, the transmission time holding part 22 acquires and holds the time from the counter 21 for time.

(Action 133)

The device A10 transmits the packet 31 indicating the packet reception time held in the reception time holding unit 13 in operation 132 from the packet transmission unit 14 to the device B20 . The device B20 receives the packet 31 indicating the packet transmission time in the packet receiving unit 25 .

(Act 134)

The difference calculation unit 26 of the device B20 is configured to calculate the packet transmission time held by the transmission time holding unit 22 in operation 132 and the packet 31 received from the device A10 in operation 133. Calculate the difference between packet reception times represented by . The difference calculation unit 26 calculates a delay time by communication between devices based on the calculated difference, and corrects the time counter 21 with the delay time. The difference between the packet reception time in the device A10 and the packet transmission time in the device B20 includes the time for communication between the device A10 and the device B20 to reciprocate. Then, for example, the difference calculating part 26 may calculate 1/2 of the difference of the packet reception time in the device A10 and the packet transmission time in the device B20 as a delay time, for example. .

○ Action 140

The device B20 continues the above operation 120 and maintains a state in which the time is synchronized with the device A10.

As described above, the packet receiving unit 25 of the device B20 receives, from the device A10, a correction period for performing drift correction, and at a time interval of the correction period, from the device A10 The time keeping packet and the transmission time of the time keeping packet are received. In response to receiving the transmission time of the packet for time maintenance and the packet for time maintenance from the device A10, the difference calculation unit 26 of the device B20 is the time measured by the counter 21 for time. The difference between the reception time of the maintenance packet and the transmission time received from the device A10 is calculated. The drift correction unit 28 performs drift correction in a time period determined by the value obtained by dividing the drift correction period by the number of counts of the time counter 21 corresponding to the difference according to the difference calculation unit 26 calculating the difference. is determined as the timing of , and at that timing, only the counter value of the time counter 21 is corrected by 1. In this way, in the time period determined by the value obtained by dividing the correction period in which the drift correction is performed by the device B 20 by the number of counts of the time counter 21 corresponding to the difference between the transmission and reception times of the packet for time maintenance, The counter value of the time counter 21 is automatically corrected by 1 only. Therefore, the apparatus B20 becomes possible to perform highly accurate time synchronization according to the resolution of the counter 21 for time, without frequently communicating with the apparatus A10.

In addition, in the packet transmission unit 24 of the device B20, the difference between the reception time of the packet for time maintenance calculated by the difference calculation unit 26 and the transmission time received from the device A10 is a predetermined value In response to being less than , the second packet for keeping time is transmitted to the device A10. The packet receiving unit 25 of the device B 20 determines the reception time measured by the time counter 11 of the device A 10 at which the device A 10 received the second time keeping packet. Receive from A (10). The difference calculation unit 26 of the device B20 transmits the second timekeeping packet measured by the time counter 21, and the device A10 transmits the second timekeeping packet. A second difference, which is the difference between the received reception times, is calculated. The difference calculating part 26 of the apparatus B20 correct|amends the counter value of the counter 21 for time based on a 2nd difference. For example, the difference calculation part 26 may correct|amend the counter value of the counter 21 for time with the value of 1/2 of the 2nd difference. In this way, since the device B 20 corrects the counter value of the counter 21 for time based on the difference between the transmission and reception times of the second time keeping packet, it is caused by a communication delay with the device A 10 . It becomes possible to correct the temporal deviation.

(Example of operation)

An example of the specific operation procedure of the time synchronization system 1 which concerns on this embodiment is demonstrated with reference to FIG. Hereinafter, as an example, time is shown in microsecond units, but other units may be sufficient.

○ Step 210

The device A10 transmits the correction period packet 31 which notifies 1s as a drift correction period from the packet transmission part 14 to the apparatus B20 (S1 in FIG. 2). The device B 20 receives the correction period packet 31 in the packet receiving unit 25, and holds the drift correction period 1s indicated by the correction period packet 31 in the correction period holding unit 27 ( S2 in FIG. 2).

○ Step 220

The device A10 and the device B20 repeatedly execute the following steps 221 to 227 at intervals of 1 s of the drift correction period. The device B20 executes step 228 in parallel with steps 221 to 227 .

(Step 221)

Device A10 transmits the packet 31 for time maintenance from the packet transmission part 14 to the device B20 (S3 of FIG. 2). The device B20 receives the packet 31 for time maintenance in the packet receiving unit 25 .

(Step 222)

The packet transmission unit 14 of the device A10 notifies the transmission time keeping unit 12 that the packet 31 for time maintenance was transmitted to the device B20 in step 221 . Thereby, as shown to S4 of FIG. 2, the transmission time holding part 12 acquires time 301 microseconds from the counter 11 for time, and holds this.

When the packet receiving unit 25 of the device B20 receives the packet 31 for time keeping, it notifies the reception time holding unit 23 of packet reception. Thereby, the reception time holding part 23 acquires the time 106 microseconds from the counter 21 for time, and holds this (S5 of FIG. 2).

(Step 223)

The device A10 transmits the packet 31 indicating 301 μs of time information held by the transmission time holding unit 12 in step 222 from the packet transmission unit 14 to the device B20 ( FIG. 2 ). S6). The device B20 receives the packet 31 indicating this packet transmission time in the packet reception unit 25 .

(Step 224)

The difference calculation unit 26 of the device B 20 includes a time indicated by the packet 31 received from the device A 10 (301 μs in the example shown in FIG. 2 ) and a reception time holding unit 23 . From the time information (106 microseconds in the example shown in FIG. 2) held by 195 microseconds shift|offset|difference of the counter 21 for time (= 301 microseconds - 106 microseconds) is calculated (S7 of FIG. 2). As shown in S8 of FIG. 2, the difference calculation part 26 correct|amends the counter 21 for time with the calculated difference.

(Step 225)

The drift correction unit 28 of the device B 20 acquires the drift correction period 1s from the correction period holding unit 27 .

(Step 226)

The drift correction unit 28 of the device B 20 acquires the difference calculated in step 224 from the difference calculation unit 26 . Each time the drift correction unit 28 acquires a difference, it calculates the accumulated value (S9 in Fig. 2). In the example of Fig. 2, the accumulated value is 195 mu s.

(Step 227)

The drift correction unit 28 of the device B 20 calculates the drift correction timing by dividing the drift correction period 1s obtained in step 225 by the count number of the time counter 21 corresponding to the accumulated difference 195 µs (Fig. 2). S10). For example, when the resolution of the counter 21 for time is 1 ns, the count number of the counter 21 for time corresponding to the difference 195 ns is 195000 counts. Therefore, in the example shown in FIG. 2, the drift correction timing becomes 1s ÷ 195000 counts = about 5.128 microseconds/count.

(Step 228)

In parallel with steps 221 to 227, the drift correction unit 28 of the device B 20 corrects only one count of the time counter 21 at every 5.128 µs of drift correction timing (S11 in FIG. 2).

○ Step 230

After the difference obtained by the drift correcting unit 28 from the difference calculating unit 26 becomes sufficiently close to zero, the device B20 stops repeating the steps 221 to 227, and the following steps 231 to 231 234 is executed. The device B20 may, for example, determine whether or not the difference obtained a predetermined value according to the obtained precision is less than, and when it is determined that it is less than, you may perform steps 231 - step 234.

(Step 231)

The device B20 transmits the packet 32 for time maintenance from the packet transmitter 24 to the device A10 (S12 in FIG. 2). The device A10 receives the packet 32 for time maintenance in the packet receiving unit 15 .

(Step 232)

When the packet receiving unit 15 of the device A receives the packet 32 for time keeping, it notifies the reception time holding unit 13 of packet reception. Thereby, as shown to S13 of FIG. 2, the reception time holding part 13 acquires the time 522 microseconds from the counter 11 for time, and holds this.

The packet transmission unit 24 of the device B20 notifies the transmission time keeping unit 22 that the packet 32 for time maintenance was transmitted to the device A10 in step 231 . Thereby, as shown to S14 of FIG. 2, the transmission time holding part 22 acquires the time (518 microseconds in the example of FIG. 2) from the counter 21 for time, and holds this.

(Step 233)

The device A10 transmits a packet 31 indicating a packet reception time of 522 µs held by the reception time holding unit 13 in step 232 from the packet transmission unit 14 to the device B20 (FIG. 2, S15). The device B20 receives the packet 31 indicating the packet transmission time (522 µs in the example shown in FIG. 2 ) in the packet receiving unit 25 .

(Step 234)

The difference calculation unit 26 of the device B 20 includes a packet reception time 522 μs indicated by the packet 31 received from the device A 10 , and a packet transmission time held by the transmission time holding unit 22 . A difference of 4 μs (= 522 μs - 518 μs) of 518 μs is calculated (S16 in FIG. 2 ). And the difference calculating part 26 calculates 2 microseconds, which is 1/2 of the difference 4 microseconds, as a delay time by communication between devices, and corrects the counter 21 for time by the delay time (FIG. 2). S17).

○ Order 240

The device B20 continues the above step 220 and maintains a state in which the time is synchronized with the device A10.

According to the above configuration, it is possible to reduce the frequency of correction and establish high-precision time synchronization. For example, when the precision of 50 ppm of the counter 21 for time of the apparatus B 20 is 1 ns of resolution, the precision of time synchronization can be made into 1/1000 ppm. As a result, in the prior art, corrections were required at a frequency of 50 times per second in order to maintain the precision of 1 μs, but the frequency can be reduced to once every 1000 seconds, and the communication path can be used for other communication. In addition, it is possible to establish high-accuracy time synchronization corresponding to the resolution of 1 ns of the time counter 21 of the device B20 by using an inexpensive oscillator that is not highly accurate.

As described above, in the time synchronization system 1, the device B 20 accumulates the difference between the transmission and reception times of the time keeping packets by itself for each drift correction period, determines the drift correction period based on the value, and automatically to perform drift compensation. Therefore, according to the time synchronization system 1, high-precision time synchronization can be performed at arbitrary correction frequencies.

Moreover, the device A10 and the device B20 just need to be able to exchange time information by a communication packet, and can implement|achieve high-precision time synchronization by arbitrary communication protocols.

Moreover, also when there are two or more devices B20, time synchronization can be implemented by the same method. When there are two or more devices B20, the wiring structure can take arbitrary structures, such as star wiring or a daisy chain.

This indication is not limited to embodiment mentioned above. For example, a plurality of blocks described in the block diagram may be integrated. Alternatively, one block may be divided. The plurality of steps described in the flowchart may be executed in parallel or in a different order according to the processing capability of the apparatus executing each step, or as needed, instead of being executed in time series according to the description. In addition, changes in the range which does not deviate from the meaning of this indication are possible.

1: Time Synchronization System
10: device A
11: time counter
12: transmission time maintaining unit
13: reception time maintenance unit
14: packet transmitter
15: packet receiver
20: device B
21: time counter
22: transmission time maintaining unit
23: reception time maintenance unit
24: packet transmitter
25: packet receiver
26: difference calculator
27: correction period maintenance unit
28: drift compensation unit
31, 32: packet
9: Visual synchronization system
80: device A
81: time counter
82: transmission time maintaining unit
83: reception time maintaining unit
84: packet transmitter
85: packet receiver
90: device B
91: time counter
92: transmission time maintaining unit
93: reception time maintaining unit
94: packet transmitter
95: packet receiver
96: difference calculator
71, 72: packet

Claims (6)

An information processing apparatus comprising: a first counter for measuring time by counting up a counter value at a fixed time period; and a communication means;
The communication means receives a packet for maintaining the time transmitted by an external device having a second counter for measuring a reference time,
the communication means receives, from the external device, a transmission time measured by the second counter at which the external device transmits the time keeping packet;
calculation means for calculating a difference between the reception time at which the time keeping packet was received and the transmission time measured by the first counter;
first correction means for correcting the counter value of the first counter based on the difference;
determining means for determining a timing for correcting the counter value of the first counter based on the difference;
second correction means for correcting the counter value of the first counter at the determined timing
An information processing device comprising a. The method of claim 1,
The communication means receives, from the external device, a correction period for performing drift correction;
the communication means receives the transmission time of the time keeping packet and the time keeping packet from the external device at time intervals of the correction period;
the calculating means calculates the difference in response to receiving the transmission time of the time keeping packet and the time keeping packet from the external device;
the determining means determines, as the timing, a time period determined by a value obtained by dividing the correction period by the number of counts of the first counter corresponding to the difference according to the calculation means calculating the difference;
The second correction means is configured to correct only the counter value of the first counter by one at the determined timing.
information processing unit. 3. The method of claim 1 or 2,
the communication means transmits a second time keeping packet to the external device in response to the difference calculated by the calculation means being less than a predetermined value;
the communication means receives, from the external device, a reception time measured by the second counter at which the external device receives the second time keeping packet;
The calculation means calculates a second difference, which is a difference between a transmission time at which the second time keeping packet is transmitted, and a reception time at which the external device receives the second time keeping packet, measured by the first counter. calculate,
The first correction means is configured to correct a counter value of the first counter based on the second difference.
information processing unit. 4. The method of claim 3,
The first correction means corrects the counter value of the first counter by a value of 1/2 of the second difference. A first information processing apparatus comprising: a first counter for measuring time by counting up a counter value at a constant time period; and a first communication means;
A second information processing device having a second counter for measuring a reference time and a second communication means
As an information processing system having a
the second communication means of the second information processing device transmits a time keeping packet to the first information processing device;
the first communication means of the first information processing apparatus receives the time keeping packet transmitted by the second information processing apparatus;
the second communication means of the second information processing device transmits, to the first information processing device, a transmission time measured by the second counter at which the time keeping packet was transmitted;
the first communication means of the first information processing device receives a transmission time at which the second information processing device transmits the time keeping packet;
The first information processing device,
calculation means for calculating a difference between the reception time at which the time keeping packet was received and the transmission time measured by the first counter;
first correction means for correcting the counter value of the first counter based on the difference;
determining means for determining a timing for correcting the counter value of the first counter based on the difference;
second correction means for correcting the counter value of the first counter at the determined timing
An information processing system comprising a. An information processing method for an information processing apparatus comprising: a first counter for measuring time by counting up a counter value at a fixed time period; and a communication means, the information processing method comprising:
The communication means receives the packet for maintaining the time transmitted by the external device having a second counter for measuring the reference time,
the communication means receives, from the external device, the transmission time measured by the second counter at which the external device transmits the time keeping packet;
calculating means calculates a difference between a reception time at which the packet for time keeping measured by the first counter is received and the transmission time;
a first correction means corrects a counter value of the first counter by the difference;
determining means determines a timing for correcting the counter value of the first counter based on the difference;
a second correction unit corrects the counter value of the first counter at the determined timing
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