WO2018093046A1

WO2018093046A1 - Utc time synchronization method of device using gps that improves abnormal operating situation

Info

Publication number: WO2018093046A1
Application number: PCT/KR2017/011249
Authority: WO
Inventors: 정한균; 임기택; 신대교; 윤상훈; 장수현; 진성근
Original assignee: 전자부품연구원
Priority date: 2016-11-15
Filing date: 2017-10-12
Publication date: 2018-05-24
Also published as: KR101967027B1; KR20180054103A

Abstract

Provided is a UTC time synchronization method of a device using a GPS that improves an abnormal operating situation. A time synchronization method according to an embodiment of the present invention comprises: a first setting step in which a processor sets a time value of a system time in seconds by using a first signal; and a second setting step in which, when the reception time of the first signal and the generation time of a second signal satisfy a specific condition, the processor sets the time value of the system time in seconds or less by using the second signal. Accordingly, it is possible to perform synchronization to UTC time in nanoseconds to microseconds, thereby improving the accuracy and performance of the device/system.

Description

How to synchronize UTC time with a device using GPS that improves abnormal behavior

The present invention relates to a time synchronization method, and more particularly, to a method of mounting a global positioning system (GPS) module and synchronizing time of a device based thereon.

In general, the GPS module obtains a Universal Time Coordinated (UTC) time value based on the information received from the GPS satellites (= the GPS module's clock is synchronized with UTC time), which is a UART (Universal Asynchronous Receiver / Transmitter). Through the interface, it is delivered to the Central Processing Unit (CPU) of the device connected to the GPS module in the form of a National Marine Electronics Association (NMEA) message.

In typical devices and systems, a time synchronization module (such as 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 the 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 synchronization of less than seconds (milliseconds, microseconds, nanoseconds) is impossible.

-GPS Transmit Timing Error: There may be a time difference between when the GPS module acquires the UTC time value and when it is output to the device, and the time synchronization module does not know the standard deviation of the time difference and time differences. Accurate synchronization is not possible.

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

Processing Delay: A processing delay occurs during the procedure where the time synchronization module processes the NMEA message data received from the GPS module to extract the UTC time value and set it to the system time. (When operating on a preemptive operating system, process scheduling introduces unpredictable delays.)

As above, the unit of UTC time value provided by the GPS module is in the unit of second level, and there is an unpredictable error between the time when the GPS module first acquired the UTC time value and finally the time point when setting the system time. As such, there is a limit to the exact synchronization of the system clock to UTC time.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a UTC time synchronization method for synchronizing to UTC time in nano to micro seconds in a specific device / system equipped with a GPS module. .

According to an embodiment of the present invention, a time synchronization method includes: a first setting step of setting, by a processor, a time value in seconds of a system time using a first signal; And a second setting step of setting, by the processor, a time value equal to or less than a second of the system time by using the second signal when the reception time of the first signal and the generation time of the second signal satisfy a specific condition.

In the second setting step, when the difference between the reception time of the first signal and the generation time of the second signal is less than or equal to the first time, the processor may use the second signal to set a time value less than or equal to seconds of the system time. have.

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

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

In addition, 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.

The second setting step may further include storing a second signal generation time. The first setting step may include: when a difference between the system time at which the first signal is received and the stored second signal generation time is greater than a reference value. The first signal may set a time value in seconds of the system time.

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

On the other hand, according to another embodiment of the present invention, a system includes a module for generating a first signal and a second signal including time information; And setting a time value in seconds of the system time using the first signal received from the module, and using the second signal received from the module when the reception time of the first signal and the generation time of the second signal satisfy a specific condition. And a processor configured to set a time value equal to or less than a second of a system time.

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

1 is a block diagram of a system to which the present invention is applicable;

2 is a diagram illustrating a normal operation timing situation;

3 is a diagram illustrating an abnormal operation timing situation;

4 is a flowchart provided to explain a time synchronization method according to an embodiment of the present invention;

FIG. 5 is a diagram illustrating a specific processing procedure in the time synchronization method illustrated in FIG. 4;

6 and 7 are diagrams provided in the description of additional abnormal operating timing situations,

8 is a flowchart provided to explain a time synchronization method according to another embodiment of the present invention;

9 is a diagram illustrating in detail a processing procedure according to a time synchronization method according to another embodiment of the present invention;

10 is a flowchart provided to explain a time synchronization method according to another embodiment of the present invention, and

11 is a diagram specifically illustrating a processing procedure according to a time synchronization method according to another embodiment of the present invention.

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

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 is applicable is constructed by connecting a Global Positioning System (GPS) module 110 to a central processing unit (CPU) 120. Specifically, the National Marine Electronics Association (NMEA) message output pin and the PPS signal pin of the GPS module 110 are connected to the CPU 120.

Accordingly, the time synchronization module 130, which is a software module for synchronizing the system clock executed in the CPU 120 to Universal Time Coordinated (UTC) time, may receive and process an NMEA message to obtain a UTC time value.

In addition, 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 several nanoseconds from the actual UTC time.

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

Phase1: The time synchronization module 130 stores the UTC time value in seconds obtained from the NMEA message received from the GPS module 110 in an internal variable (= utcTime).

-Phase2: After receiving the PPS signal from the GPS module 110, the time synchronization module 130 sets the UTC time value in seconds, which is stored in an internal variable (= utcTime) in the interrupt processing routine, as the system time. Set the time value in seconds to zero.

Through this, the following problems can be solved.

-Transmission delay: The transmission delay itself exists, but "transmission time" and "system time setting time" are separated into phase1 and phase2, respectively, and the transmission delay is not applied at the system time setting time.

-Processing Delay: The processing delay itself remains intact, but "NMEA message parsing and UTC time value acquisition time" and "System time setting time" are separated into Phase1 and Phase2 respectively, so processing delays are accumulated and applied at the system time setting time In addition, 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 another process.

Low resolution: If you set the microsecond time to 0 for PPS interrupts, the time in microseconds is taken into account even when the error in PPS itself (in nanoseconds) and the delay in the interrupt processing routine (in hundreds to tens of nanoseconds). Can be synchronized. For higher accuracy, you can set nanosecond values with PPS error and measured interrupt handling routine delays instead of zero microseconds.

Through the above method, the problem of transmission delay, processing delay and low resolution can be solved. GPS timing error is solved as follows.

The time synchronization module 130 may not know when to output the UTC time acquired by the GPS module 110. In addition, when the UTC time is output at a specific timing, the normal operation may be performed as shown in FIG. 2, but as shown in FIG. 3, the UTC time may be changed in units of 1 second.

That is, if the UTC second is changed while the GPS module 110 acquires the UTC time value and outputs it (abnormal operation timing), when the time synchronization module 130 acquires the UTC time value, the present time is 'Current UTC-1'. It will have a seconds value of.

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

As shown in FIG. 4, first, the time synchronization module 130 stores the "PPS generation time" in an internal variable (= utcTime) every time PPS occurs, based on the current system time (S210).

In addition, when receiving the NMEA message including the UTC time value from the GPS module 110 (S220), the time synchronization module 130 transmits the system time (Tcurrent) at the moment of receiving the received NMEA message including the UTC time value. The difference between the " and the " PPS generation time (Tpps) " stored in the internal variable (= utcTime) is calculated (S230).

Calculating the time difference is to prevent the following timing error (Tdiff).

Tdiff = Dmsg + Dgps

Dmsg: Transmission delay required for NMEA message to be delivered from GPS module 110 to time synchronization module 130

Dgps: the difference between the actual time generated inside the GPS module 110 and the time stored in the message

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

For example, suppose that you receive an NMEA message from the GPS module 110 through the serial port, and if you have a baudrate of 9,600 (the slowest rate), you receive a line about 30 bytes long (approximately the NMEA line length). The transmission delay is about 25 msec.

This corresponds to an abnormal operation timing shown in FIG. 3 when a PPS interrupt occurs between 25msec + Dgps to which a time value is transmitted. Thus, 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 baudrate is 115,200, since the transmission delay is about 2 msec, the CPU 120 may calculate Dmsg differently based on the baudrate of the serial port. Dgps can be identified or guessed from the product datasheet. For example, it may be 5 msec depending on the product.

Since there are four NMEA messages including UTC time values, at least xxZDA, xxRMC, xxGLL, and xxGGA, at least one message is received 25 msec after the PPS occurs.

On the other hand, if (Tcurrent-Tpps)> Tdiff (S240-Y), the time synchronization module 130 sets the system time using the corresponding NMEA message (S250). That is, if the calculated time difference is longer than the interval where 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, stores the corresponding time in an internal variable (utcTime), and converts the utcTime + 1 second value to the system time in the next PPS interrupt processing routine. Set it.

In FIG. 5, a process of '(Tcurrent-Tpps) > Tdiff' and '(Tcurrent-Tpps) > Tdiff' in the time synchronization method shown in FIG. 4 is illustrated in detail.

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 "confirm stored time of previous PPS generation" procedure and the "store internal variable (= utcTime)" procedure performed by the time synchronization module 130 when receiving the NMEA message are not completely atomic operations, and thus, FIG. As shown, there is room for timing mismatch if PPS occurs between two procedures.

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

To this end, another embodiment of the present invention, proposes a method for solving the abnormal operation by the "1)". 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. 4.

Specifically, as shown in FIG. 8, when the NMEA message including the UTC time value is received from the GPS module 110 (S220), the time synchronization module 130 may be configured with the "system time of the received moment". The difference in the stored "PPS generation time" is calculated (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 time when the NMEA message reception time is included in the time period before 990 msec (= 0.99 sec) has elapsed from the previously stored "PPS occurrence time" and 1 sec has elapsed. have.

In other words, if the time difference is very close to 1 second, since the PPS timing is likely to overlap, the received NMEA message is ignored to avoid this.

It is determined by the relationship of "990msec = 1sec-10msec", "10msec" can be replaced by another value in consideration of jitter.

Since the NMEA message is ignored even when (Tcurrent-Tpps) ≤ Tdiff in step S240 of FIG. Received NMEA messages are 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. For example, when the NMEA message reception time is not included in the time period before 990 msec elapses and 1 sec elapses from the previously stored "PPS generation time".

9 specifically 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 "2)" is proposed. 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. 4.

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

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

On the other hand, if the calculated time difference is 1.5 seconds or less (S244-Y), the PPS interrupt is determined to be normal, and step S250 is performed, whereby the system time is set.

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

Through the above method, the system equipped with the GPS module 110 may synchronize the system clock in nano-microsecond units with UTC time.

So far, the preferred embodiment of the UTC time synchronization method of the device using GPS has been described in detail.

In an embodiment of the present invention, a method of synchronizing a system clock in UTC to nanoseconds 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 inventive concept of the present invention can be applied to a WAVE vehicle terminal using GPS and other systems.

On the other hand, the technical idea of the present invention can be applied to a computer-readable recording medium containing 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 disclosure may be implemented in the form of computer readable codes recorded on a computer readable recording medium. The computer-readable recording medium can be 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.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the specific embodiments described above, but the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

Claims

A first setting step of the processor setting a time value in seconds of the system time by using the first signal; And

And a second setting step of setting, by the processor, a time value equal to or less than a second of system time by 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,

The second setting step is

And if the difference between the reception time of the first signal and the generation time of the second signal is less than or equal to the first time, the processor sets a time value less than or equal to seconds of system time using the second signal.
The method according to claim 1,

The second setting step is

And if the difference between the system time and the generation time of the second signal is less than or equal to the second time, the processor sets a time value less than or equal to seconds of the system time by using the second signal.
The method according to claim 1,

The second signal is an interrupt signal,

The second setting step is performed in an interrupt processing routine.
The method according to claim 4,

The first signal is an NMEA message received from the GPS module,

The second signal is a time synchronization method, characterized in that the PPS signal received from the GPS module.
The method according to claim 1,

The second setting step is

Storing a second signal generation time;

The first setting step is

And setting a time value in seconds of the system time by using the first signal when the difference between the received system time and the stored second signal generation time is greater than the reference value.
The method according to claim 6,

The first setting step is

Storing the second time value extracted from the first signal in an internal variable;

And when the second signal is received, setting the second time value + 1 stored in the internal variable as the second time value of the system time.
A module for generating a first signal and a second signal including time information; And

Set a time value in seconds of the system time 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, use the second signal received from the module. And a processor configured to set a time value equal to or less than a second of the system time.