KR20180054103A - Improved UTC Time Synchronization Method for a Device using GPS Module in Abnormal Operation Condition - Google Patents

Improved UTC Time Synchronization Method for a Device using GPS Module in Abnormal Operation Condition Download PDF

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KR20180054103A
KR20180054103A KR1020160151629A KR20160151629A KR20180054103A KR 20180054103 A KR20180054103 A KR 20180054103A KR 1020160151629 A KR1020160151629 A KR 1020160151629A KR 20160151629 A KR20160151629 A KR 20160151629A KR 20180054103 A KR20180054103 A KR 20180054103A
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time
signal
value
module
seconds
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KR1020160151629A
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KR101967027B1 (en
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정한균
임기택
신대교
윤상훈
장수현
진성근
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전자부품연구원
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Priority to PCT/KR2017/011249 priority patent/WO2018093046A1/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G—PHYSICS
    • G04—HOROLOGY
    • G04C—ELECTROMECHANICAL CLOCKS OR WATCHES
    • G04C11/00—Synchronisation of independently-driven clocks
    • G—PHYSICS
    • G04—HOROLOGY
    • G04C—ELECTROMECHANICAL CLOCKS OR WATCHES
    • G04C11/00—Synchronisation of independently-driven clocks
    • G04C11/02—Synchronisation of independently-driven clocks by radio
    • G04C11/026—Synchronisation of independently-driven clocks by radio the time-piece preparing itself on set times on the reception of the sychronising signal
    • G—PHYSICS
    • G04—HOROLOGY
    • G04R—RADIO-CONTROLLED TIME-PIECES
    • G04R20/00—Setting the time according to the time information carried or implied by the radio signal
    • G04R20/02—Setting the time according to the time information carried or implied by the radio signal the radio signal being sent by a satellite, e.g. GPS

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Electric Clocks (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)

Abstract

There is provided a method of UTC time synchronization of a device using GPS which improves an abnormal operation situation. A time synchronization method according to an embodiment of the present invention includes a first setting step in which a processor sets a time value of a system time in seconds using a first signal and a second setting step in which a reception time of a first signal and a generation time of a second signal are specified And if the condition is satisfied, the processor sets a time value of seconds or less of the system time using the second signal. This makes it possible to synchronize the UTC time in units of nanoseconds to microseconds, thereby improving the accuracy and performance of the device / system.

Figure P1020160151629

Description

[0001] The present invention relates to a UTC time synchronization method for a GPS device that improves an abnormal operation situation,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time synchronization method, and more particularly, to a method of synchronizing time of a device by mounting a Global Positioning System (GPS) module.

In general, the GPS module obtains a Universal Time Coordinated (UTC) time value based on the information received from the GPS satellite (= the GPS module clock is synchronized with the UTC time) and transmits it to a UART (Universal Asynchronous Receiver / Transmitter) Interface to a central processing unit (CPU) of a device connected to the GPS module in the form of a National Marine Electronics Association (NMEA) message.

In common devices and systems, a time synchronization module (eg, a software module that synchronizes the system clock to UTC time) can synchronize the system clock to UTC time by setting the UTC time value received from the GPS module to system time, The method has the following problems.

- Low resolution: The UTC time value received from the GPS module has a value in seconds, so it is impossible to synchronize less than a second (millisecond, microsecond, nanosecond).

- GPS transmission timing error: There may be a time difference between the time when the GPS module acquires the UTC time value and the time when it outputs to the device. Since the time synchronization module does not know the standard deviation of these time differences and time differences , Precise synchronization is impossible.

- Transmission delay: Transmission delay occurs when the GPS module transmits data to the time synchronization module.

- Processing Delay: The time synchronization module processes the NMEA message data received from the GPS module to extract the UTC time value and a processing delay occurs during the procedure of setting it as the system time. (When running on a preemptive operating system, there is an unpredictable delay due to process scheduling.)

As mentioned above, the unit of the UTC time value provided by the GPS module is in the order of seconds, and there is an unpredictable error between the time at which the GPS module acquires the UTC time value for the first time and finally the time at which the system time is set There is a limitation in accurately synchronizing the system clock with the UTC time.

It is an object of the present invention to provide a UTC time synchronization method of synchronizing UTC time in nano-microsecond time in a specific device / system equipped with a GPS module .

According to an aspect of the present invention, there is provided a time synchronization method including: a first setting step of setting a time value of a system time in seconds using a first signal; And a second setting step in which the processor sets a time value in seconds of the system time using the second signal if the reception time of the first signal and the generation time of the second signal satisfy a specific condition.

If the difference between the reception time of the first signal and the generation time of the second signal is equal to or shorter than the first time, the second setting step may set the time value of the system time in seconds or less have.

In addition, the second setting step may set the time value of the system time to be less than a second of the system time by using the second signal if the difference between the system time and the generation time of the second signal is equal to or shorter than the second time.

The second signal is an interrupt signal, and the second setting step can be performed in the interrupt processing routine.

Also, the first signal may be an NMEA message received from the GPS module, and the second signal may be a PPS signal received from the GPS module.

And a second setting step of storing a second signal generation time when the difference between the system time at which the first signal is received and the stored second signal generation time is greater than the reference value , The time value of the system time in seconds can be set using the first signal.

In addition, the first setting step may include: storing a time unit value extracted from the first signal in an internal variable; When the second signal is received, setting a value of the unit time value + 1 stored in the internal variable as a time unit value of the system time.

According to another aspect of the present invention, there is provided a system including: a module for generating a first signal and a second signal including time information; And a second signal received from the module is used to set a time value of the system time in units of seconds. When the reception time of the first signal and the generation time of the second signal satisfy a specific condition, And setting a time value of seconds or less of the system time.

As described above, according to the embodiments of the present invention, it is possible to synchronize the UTC time in nano-microseconds in a specific device / system equipped with the GPS module, thereby improving the accuracy and performance of the device / It becomes possible.

1 is a block diagram of a system to which the present invention is applicable;
2 is a diagram showing a normal operation timing situation,
3 is a diagram showing an abnormal operation timing situation,
FIG. 4 is a flow chart for explaining a time synchronization method according to an embodiment of the present invention;
5 is a diagram illustrating a specific processing procedure in the time synchronization method shown in FIG. 4,
Figures 6 and 7 are diagrams provided to illustrate additional abnormal operation timing situations,
8 is a flowchart provided in the description of a time synchronization method according to another embodiment of the present invention;
9 is a diagram illustrating a process according to another exemplary embodiment of the present invention,
FIG. 10 is a flowchart illustrating a time synchronization method according to another embodiment of the present invention,
FIG. 11 is a diagram illustrating a processing procedure according to a time synchronization method according to another embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a block diagram of a system to which the present invention is applicable. As shown in FIG. 1, a system to which the present invention can be applied is constructed by connecting a Global Positioning System (GPS) module 110 to a CPU (Central Processing Unit) 120. Specifically, the NMEA (National Marine Electronics Association) message output pin of the GPS module 110 and the PPS signal pin are connected to the CPU 120.

Accordingly, the time synchronization module 130, which is a software module that synchronizes the system clock executed by the CPU 120 in UTC (Universal Time Coordinated) time, receives and processes the NMEA message to obtain the UTC time value.

Also, the PPS signal pin of the GPS module 110 is connected to the interrupt input of the CPU 120 so that the interrupt processing routine can be called when the PPS signal is generated. The PPS is a pulse output by the GPS module 110 every 1 second of UTC, and has an error of about several nanoseconds from the actual UTC time.

The basic operation of the system shown in Fig. 1 is as follows.

- Phase 1: The time synchronization module 130 stores the UTC time value in seconds acquired in the NMEA message received from the GPS module 110 in an internal variable (= utcTime).

- Phase 2: After receiving the PPS signal from the GPS module 110, the time synchronization module 130 sets the UTC time value in seconds stored in the internal variable (= utcTime) in the interrupt processing routine as the system time, Set the time value in seconds to zero.

Thus, the following problems can be solved.

- Transmission delay: Although the transmission delay itself is present, the transmission delay is accumulated and not applied since the transmission time and the system time setting time are separated into Phase 1 and Phase 2, respectively.

- Processing delay: The processing delay itself exists, but the processing delay is accumulated and accumulated at the time of setting the system time by separating "NMEA message parsing and UTC time value acquisition point" and "system time setting point" into Phase 1 and Phase 2 respectively Since the system time setting operation is performed in the interrupt processing routine, the delay is very small and predictable because it is not preempted by other processes.

- Low resolution: Setting the microsecond time to 0 in the PPS interrupt sets the time in microseconds, even if you take into account the error of the PPS itself (in nanoseconds) and the delay of the interrupt handling routine (in the range of several to several tens of nanoseconds) You can synchronize. For higher accuracy, you can set the nanosecond unit value by applying the PPS error and the measured interrupt processing routine delay instead of 0 microseconds.

In this way, transmission delay, processing delay, and low resolution problems can be solved, and the GPS timing error can be solved as follows.

The time synchronization module 130 can not know when the GPS module 110 outputs the acquired UTC time. In addition, when the UTC time is output at a specific timing, it can operate normally as shown in FIG. 2. However, as shown in FIG. 3, the UTC time may be shifted by one second.

That is, when the UTC time value is acquired and the UTC time is changed during the output of the UTC time value, the time synchronization module 130 acquires the UTC time value, Lt; / RTI > seconds.

To this end, the time synchronization method shown in FIG. 4 is presented. 4 is a flow chart provided in the description of the time synchronization method according to an embodiment of the present invention.

As shown in FIG. 4, the time synchronization module 130 stores the "PPS occurrence time" in the internal variable (= utcTime) on the basis of the current system time each time the PPS is generated (S210).

Upon receiving the NMEA message including the UTC time value from the GPS module 110 in step S220, the time synchronization module 130 determines whether the NMEA message including the UTC time value is received at the system time instant Tcurrent, PPS occurrence time (Tpps) "stored in the internal variable (= utcTime) (S230).

The calculation of the time difference is to prevent the following timing error (Tdiff).

Tdiff = Dmsg + Dgps

- Dmsg: transmission delay required for the NMEA message to be transmitted from the GPS module 110 to the time synchronization module 130

- Dgps: Difference between the actual time inside the GPS module 110 and the time stored in the message

(Tcurrent - Tpps) < Tdiff (S240-N), the time synchronization module 130 ignores the NMEA message (S260). That is, if the computed time difference is short enough to cause a timing error, the UTC time in the NMEA message is ignored.

For example, if it is assumed that a NMEA message is received from the GPS module 110 via the serial port and a line (approximately NMEA line length) of about 30 bytes long is received when the baud rate is 9,600 (the slowest rate) The transmission delay is about 25 msec.

This occurs when the PPS interrupt occurs between 25 msec + Dgps at which the time value is transmitted, which corresponds to the abnormal operation timing shown in FIG. Accordingly, the time synchronization module 130 ignores the message if (Tcurrent - Tpps) is less than (25 msec (= Dmsg) + Dgps). That is, it does not update the internal variable utcTime.

On the other hand, when the baud rate is 115,200, the transmission delay is about 2 msec, so the CPU 120 may calculate the Dmsg differently based on the baud rate of the serial port. Dgps can be verified or guessed through the product data sheet. For example, it may be 5msec depending on the product.

Since the NMEA message including the UTC time value is at least four xxZDA, xxRMC, xxGLL and xxGGA messages, at least one message is received at a time point after 25 msec after the PPS occurrence.

On the other hand, if (Tcurrent - Tpps)> Tdiff (S240-Y), the time synchronization module 130 sets the system time using the NMEA message (S250). That is, if the calculated time difference is longer than the interval in which the timing error occurs, the UTC time in the corresponding NMEA message is used.

Specifically, in step S250, the time synchronization module 130 extracts the UTC time value from the NMEA message and stores the time in the internal variable (utcTime). In the next PPS interrupt processing routine, the value of utcTime + Setting.

FIG. 5 illustrates a process of '(Tcurrent - Tpps) Tdiff' and '(Tcurrent - Tpps)> Tdiff' in the time synchronization method shown in FIG.

In the time synchronization method according to the embodiment of the present invention shown in FIG. 4, the following abnormal operation may occur.

1) The procedure of "checking the stored previous PPS occurrence time" and "storing the internal variable (= utcTime)" performed by the time synchronization module 130 at the time of receiving the NMEA message are not completely bound by the atomic operation, As shown, when the PPS occurs between the two procedures, there is a possibility that the timing will be changed.

2) As shown in FIG. 7, when the PPS signal reception (PPS interrupt) and the NMEA message acquisition procedure are omitted, the timing may be turned off.

To this end, in another embodiment of the present invention, a method for solving the abnormal operation by the above "1)" is presented. The time synchronization method according to another embodiment of the present invention adds the procedure shown in FIG. 8 between steps S220 and S230 shown in FIG.

8, when receiving the NMEA message including the UTC time value from the GPS module 110 (S220), the time synchronization module 130 receives the NMEA message including the " system time of the received moment " And stores the stored "PPS occurrence time" difference (S222).

If the time difference calculated in step S222 is short enough to cause a timing error (S224-Y), step S260 is performed to ignore the NMEA message.

If the time difference is short enough to cause a timing error, for example, the NMEA message reception time can be set to be included in the time interval of 990 msec (= 0.99 sec) elapsed from the previously stored "PPS occurrence time" have.

That is, if the time difference is very close to one second, the PPS timing is highly likely to overlap, so it will ignore the received NMEA message to avoid it.

Quot; 990 msec = 1 sec - 10 msec ", and "10 msec" can be replaced with another value in consideration of jitter and the like.

According to the embodiment of the present invention, since 9990 msec elapses from "PPS occurrence time" and Tdiff sec elapses from "Tcurrent" The received NMEA message is ignored.

On the other hand, if the time difference calculated in step S222 is not short enough to cause a timing error (S224-N), step S230 is performed. In other words, the NMEA message reception time is not included in the time zone of 990 msec elapsed from the previously stored "PPS occurrence time" and before 1 sec elapsed.

FIG. 9 illustrates a processing procedure according to a time synchronization method according to another embodiment of the present invention.

In another embodiment of the present invention, a method for solving the abnormal operation by the above "2)" is presented. The time synchronization method according to another embodiment of the present invention adds the procedure shown in FIG. 10 between steps S240 and S250 shown in FIG.

Specifically, as shown in FIG. 10, the time synchronization module 130 calculates the difference between "current time" and "previous PPS occurrence time" before setting the system time (S242).

At this time, if the calculated time difference is much more than 1 second (for example, more than 1.5 seconds) (S244-N), it is determined that the PPS interrupt is missed, and the step S260 is performed, whereby the NMEA message is ignored.

On the other hand, if the calculated time difference is 1.5 seconds or less (S244-Y), it is determined that the PPS interrupt is normal and the system time is set by performing step S250.

FIG. 11 illustrates a processing procedure according to a time synchronization method according to another embodiment of the present invention.

The system equipped with the GPS module 110 through the above method can synchronize the system clock in nano-microsecond time in UTC time.

Up to now, the UTC time synchronization method of a device using GPS has been described in detail with a preferred embodiment.

In the embodiment of the present invention, a method of synchronizing the system clock in nano-microsecond units in UTC time in a system equipped with the GPS module 110 is proposed.

This technique can be applied to any system using a GPS module without limitation. The technical idea of the present invention can be applied not only to a WAVE vehicle terminal using GPS, but also to other systems.

It goes without saying that the technical idea of the present invention can also be applied to a computer-readable recording medium having a computer program for performing the functions of the apparatus and method according to the present embodiment. In addition, the technical idea according to various embodiments of the present invention may be embodied in computer-readable code form recorded on a computer-readable recording medium. The computer-readable recording medium is any data storage device that can be read by a computer and can store data. For example, the computer-readable recording medium may be a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical disk, a hard disk drive, or the like. In addition, the computer readable code or program stored in the computer readable recording medium may be transmitted through a network connected between the computers.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention.

110: GPS module
120: CPU
130: Time synchronization module

Claims (8)

A processor comprising: a first setting step of setting a time value in seconds of a system time using a first signal; And
And a second setting step of setting a time value of seconds or less of the system time using the second signal when the reception time of the first signal and the generation time of the second signal satisfy a specific condition Time synchronization method.
The method according to claim 1,
In the second setting step,
Wherein the processor sets a time value less than a second of the system time using the second signal if the difference between the reception time of the first signal and the generation time of the second signal is equal to or less than the first time.
The method according to claim 1,
In the second setting step,
And if the difference between the system time and the time of occurrence of the second signal is less than or equal to a second time, the processor sets a time value of less than a second of the system time using the second signal.
The method according to claim 1,
The second signal is an interrupt signal,
And the second setting step is performed in an interrupt processing routine.
The method of claim 4,
The first signal is an NMEA message received from the GPS module,
And the second signal is a PPS signal received from the GPS module.
The method according to claim 1,
In the second setting step,
Further comprising: storing a second signal generation time,
In the first setting step,
Wherein the time value of the system time is set using the first signal if the difference between the system time at which the first signal is received and the stored second signal generation time is greater than the reference value.
The method of claim 6,
In the first setting step,
Storing a time unit value extracted from the first signal in an internal variable;
And setting a second time value + 1 stored in the internal variable as a time value in seconds of the system time when the second signal is received.
A module for generating a first signal and a second signal including time information; And
And the second signal received from the module is used to set the time value of the system time in units of seconds by using the first signal received from the module and if the reception time of the first signal and the generation time of the second signal satisfy a specific condition, And a processor for setting a time value in seconds or less of the system time.
KR1020160151629A 2016-11-15 2016-11-15 Improved UTC Time Synchronization Method for a Device using GPS Module in Abnormal Operation Condition KR101967027B1 (en)

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