Time maintaining device and time maintaining method
The time keeping device and method for satellite positioning systems use an atomic clock with drift adjustment parameter updates based on time difference information and approximation functions to maintain accurate system time, addressing high-cost and synchronization challenges.
Patent Information
- Application Number
- JP2024070278
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-04-24
- Publication Date
- 2025-11-06
AI Technical Summary
Existing satellite positioning systems face challenges in maintaining accurate timekeeping with atomic clocks, which require frequent adjustments and specialized personnel, leading to high costs and potential synchronization issues with external time standards like GPST.
A time keeping device and method utilizing an atomic clock with a system time generation means, time information processing, time accuracy monitoring, and drift adjustment parameter calculation to maintain accurate system time by periodically updating drift adjustment parameters based on time difference information and approximation functions.
The system maintains high-accuracy timekeeping at low cost by minimizing drift in atomic clocks, ensuring independence from external time standards and reducing the need for frequent adjustments.
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Figure 2025166337000001_ABST
Abstract
Description
[Technical Field]
[0001] The present disclosure relates to a time keeping device, a time keeping method, and a time keeping program. [Background technology]
[0002] Patent Document 1 describes a device for monitoring an atomic clock. [Prior art documents] [Patent documents]
[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-191551 Summary of the Invention [Problem to be solved by the invention]
[0004] To determine / estimate a coordinate on Earth using a spacecraft (artificial satellite) in orbit (i.e., to perform satellite positioning), the "coordinates of the four spacecraft," "spacecraft time (satellite time)," "receiver," and "receiver time (receiver time)" are required. "Receiver time" is the time that is synchronized with satellite time, and this time is called system time.
[0005] During satellite positioning, the pseudorange between the satellite and the receiver is calculated from the difference between the time a signal is transmitted from the satellite and the receiver time when the signal is received by the receiver. Therefore, accurate satellite time and receiver time are required to determine / estimate the receiver coordinates accurately. Satellite time is controlled by an atomic clock or similar device. Ordinary single-frequency receivers (for example, built-in modules in mobile phones, etc.) often use a quartz oscillator (hereafter referred to as "quartz") as a time reference. High-precision receivers, such as those with dual frequencies, are controlled by even more accurate quartz crystals. The receiver referred to here refers to a device that performs a series of processes using positioning information to output various information. NTP (Network Time Protocol) servers and shipboard receivers also fall under the category of receivers.
[0006] The receiver is assumed to be used in an orbit determination system that determines the orbit of an artificial satellite. In order for the receiver to keep an accurate clock, it is possible to use a high-precision crystal such as that described above, or to obtain time information from an external organization. On the other hand, if more accurate time information is required in a state independent of external sources due to certain constraints, it is also possible to use a high-precision crystal such as that described above, or a time standard more precise than a crystal, such as an atomic clock.
[0007] Typical time standards for atomic clocks include rubidium, cesium, and hydrogen maser. In order of accuracy, hydrogen maser is most accurate, followed by cesium and rubidium. The specific accuracy of a hydrogen maser atomic clock is approximately 10E-13 seconds over a measurement time of 1 second, and 10E-15 seconds over a measurement time of 1000 seconds. This accuracy is achieved when parameters on which stability depends, such as the environmental temperature and degree of vacuum in the location where the atomic clock is installed, are optimally adjusted.
[0008] Quartz crystals and other time standards have errors. These errors accumulate (drift) as the clocks operate independently for a long time. Correcting the errors generally requires adjustments to synchronize with more precise external clocks. This adjustment process requires multiple atomic clocks and multiple specialized technical personnel. Therefore, it is preferable to keep the intervals between adjustments as long as possible.
[0009] Positioning receivers require precise time information. Given the objective of positioning, it is important for the receiver to keep the same time as a Global Navigation Satellite System (GNSS), such as the Global Positioning System (GPS) or the Quazi-Zenith Satellite System (QZSS), but the receiver does not necessarily need to keep accurate time. GPS operates based on a time system called GPST (GPS Time), and it is important to synchronize the receiver's time with this system. However, considering the possibility of an abnormality occurring in GPST or if the receiver is no longer able to perform positioning using other GNSS, it is preferable to avoid directly synchronizing the receiver's time with GPST in order to maintain independence.
[0010] An object of the present disclosure is to provide a time keeping device, a time keeping method, and a time keeping program that can keep the time of a system clock at low cost and with high accuracy. [Means for solving the problem]
[0011] The time keeping device according to the present disclosure is characterized by comprising an atomic clock that generates periodic information, a system time generation means that generates a time synchronized with the periodic information as system time, a time information processing means that outputs time difference information that indicates the difference between the system time and a reference time that is a time that serves as a reference value, a time accuracy monitoring means that determines whether to update a drift adjustment parameter of the atomic clock based on the time difference information and a predetermined threshold, a time change function calculation means that, when it is determined that the drift adjustment parameter should be updated, calculates an approximation function that indicates the change in the difference over time based on time difference information from the past to the present, and a drift adjustment parameter calculation means that, when it is determined that the drift adjustment parameter should be updated, calculates the value of the drift adjustment parameter using the approximation function and the drift adjustment parameter of the atomic clock before it was updated.
[0012] The time maintenance method disclosed herein is characterized in that a computer equipped with an atomic clock that generates periodic information generates a time synchronized with the periodic information as system time, outputs time difference information indicating the difference between the system time and a reference time, which is a time that serves as a reference value, determines whether to update a drift adjustment parameter of the atomic clock based on the time difference information and a predetermined threshold, calculates an approximation function that indicates the change in the difference over time based on the time difference information from the past to the present, and, if it is determined that the drift adjustment parameter should be updated, calculates the value of the drift adjustment parameter using the approximation function and the drift adjustment parameter of the atomic clock before it was updated.
[0013] The time maintenance program of the present disclosure causes a computer equipped with an atomic clock that generates periodic information to execute a system time generation process that generates a time synchronized with the periodic information as system time, a time information process that outputs time difference information that indicates the difference between the system time and a reference time that is a time that serves as a reference value, a time accuracy monitoring process that determines whether to update a drift adjustment parameter of the atomic clock based on the time difference information and a predetermined threshold, a time change function calculation process that calculates an approximation function that indicates the change in the difference over time based on time difference information from the past to the present when it is determined that the drift adjustment parameter should be updated, and a drift adjustment parameter calculation process that calculates the value of the drift adjustment parameter using the approximation function and the drift adjustment parameter of the atomic clock before it was updated when it is determined that the drift adjustment parameter should be updated. [Effects of the Invention]
[0014] According to the present disclosure, the time of the system clock can be maintained with high accuracy at low cost. [Brief explanation of the drawings]
[0015] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a system according to the present disclosure. [Figure 2] FIG. 10 is a schematic diagram illustrating an example of the process flow of the system according to the present disclosure. [Figure 3] FIG. 2 is a block diagram showing an example of the configuration of a computer related to the time keeping device. [Figure 4] 1 is a block diagram illustrating an overview of a time keeping device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION
[0016] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings.
[0017] The time management device (hereinafter referred to as the time keeping device) of this embodiment is incorporated into, for example, an orbit determination system or an orbit estimation system that generates system time based on the time measured by an atomic clock. The system time is a system-specific time (independent time). In this embodiment, the device monitors the difference information between the GNSS reference time (GPST, GST (Galileo System Time), QZSST (QZSS Time)) broadcast from positioning satellites and the receiver time based on an atomic clock as an independent external clock input, and uses this difference information to perform an approximate calculation of the difference, thereby suppressing future drift of the atomic clock and controlling the atomic clock.
[0018] Generally, drift in atomic clocks can be controlled by adjusting the drift adjustment parameters inherent in the atomic clock. The drift adjustment method uses a calculated approximation formula to predict the time when a time difference of a certain amount or more will occur. Then, based on the amount of change in the time difference at the predicted time, the value of the drift adjustment parameter is determined so that the GNSS reference time and the receiver time are equal and the time difference can be kept within a certain range for a long period of time, and the determined drift adjustment parameter value is applied to the atomic clock.
[0019] The above method is carried out at intervals (e.g., periodically).
[0020] This method allows the time of the atomic clock used together with the reference time to be maintained with high accuracy at low cost, thereby maintaining the accuracy of the system time.
[0021] 1 is a schematic diagram showing an example of a system according to the present disclosure. The system according to the present disclosure includes a time keeping device 10 and a positioning satellite 3. The time keeping device 10 according to the present disclosure includes an atomic clock 1, a system time generating unit 2, a time information processing unit 4, a time accuracy monitoring unit 5, a time variation function calculating unit 6, a drift adjustment parameter acquiring unit 7, and a drift adjustment parameter calculating unit 8.
[0022] The system time generating unit 2 and the time information processing unit 4 are also elements of a receiver, which is used in, for example, an orbit determination system or an orbit estimation system.
[0023] The atomic clock 1 generates period information with a certain degree of accuracy.
[0024] The system time generating unit 2 generates a system time that is synchronized with the fixed periodic information generated by the atomic clock.
[0025] The positioning satellite 3 broadcasts satellite time information indicating the satellite time of the positioning satellite 3. This satellite time is a time that serves as a reference value (reference time). The satellite time can be referred to as GNSS reference time. The satellite time information can also be referred to as GNSS time information.
[0026] The time information processing unit 4 calculates time difference information indicating the difference between the satellite time indicated by the satellite time information acquired from the positioning satellites 3 in orbit and the system time generated by the system time generating unit 2, and outputs the time difference information. The satellite time indicated by the satellite time information is treated as a reference value.
[0027] The time accuracy monitoring unit 5 accumulates real-time time difference information output from the time information processing unit 4 for use in creating a time change function, and stores all time difference information from the past to the present. The past refers to, for example, the start of system operation. The past may also refer to a time a certain period prior to the current time. Based on the stored time difference information from the past to the present, the time accuracy monitoring unit 5 determines whether to update the drift adjustment parameters of the atomic clock 1 depending on whether the absolute value of the difference indicated by the time difference information is equal to or less than a preset threshold or exceeds the threshold. If the absolute value of the difference is equal to or less than the threshold, the time accuracy monitoring unit 5 determines not to update the drift adjustment parameters of the atomic clock 1. If the absolute value of the difference exceeds the threshold, the time accuracy monitoring unit 5 determines to update the drift adjustment parameters of the atomic clock 1.
[0028] When the time accuracy monitoring unit 5 determines that the drift adjustment parameter should be updated, the time change function calculation unit 6 acquires time difference information for a predetermined period between the past and the present (time difference information from the predetermined period before to the present) from the time accuracy monitoring unit 5. Based on the acquired time difference information, the time change function calculation unit 6 uses the least squares method to calculate an approximation function that indicates the change in the difference over time (the difference between satellite time and system time). This approximation function is referred to as the time change function.
[0029] The time difference accumulates over time. The time change function is a function that approximates the change in the difference over time. The time change function is a function of the time difference with time (elapsed time) as a variable.
[0030] The time change function calculation unit 6 calculates a time change function by linearly or curve-fitting the change in the time difference based on the time difference information for a predetermined period from the past to the present. For example, if time (elapsed time) is represented by x and the time difference is represented by y, then y = ax + b or y = ax 2 Calculates time-varying functions expressed in the format +bx+c etc.
[0031] The drift adjustment parameter acquisition unit 7 acquires the drift adjustment parameters before updating the period information generated by the atomic clock 1. That is, the drift adjustment parameter acquisition unit 7 acquires from the atomic clock 1 the value of the drift adjustment parameter before updating.
[0032] When the time accuracy monitoring unit 5 determines that the drift adjustment parameters should be updated, the drift adjustment parameter calculation unit 8 calculates the value of the newly set drift adjustment parameter using the time change function calculated by the time change function calculation unit 6 and the pre-update drift adjustment parameter of the atomic clock 1 acquired by the drift adjustment parameter acquisition unit 7. At this time, the drift adjustment parameter calculation unit 8 calculates the value of the newly set drift adjustment parameter so that the difference between the satellite time and the system time is close to 0 and the update interval of the drift adjustment parameter is the longest under the conditions of the frequency characteristics of the atomic clock 1.
[0033] The drift adjustment parameter calculation unit 8 uses a time change function to calculate the amount of drift (gradient) of the time difference at the time when the value of the drift adjustment parameter is adjusted, and calculates a new value of the drift adjustment parameter from the amount of drift.
[0034] The system time generation unit 2, time information processing unit 4, time accuracy monitoring unit 5, time variation function calculation unit 6, drift adjustment parameter acquisition unit 7, and drift adjustment parameter calculation unit 8 are realized, for example, by a CPU (Central Processing Unit) of a computer that operates according to a time maintenance program. This computer is equipped with an atomic clock 1. The CPU reads the time maintenance program from a program recording medium such as a program storage device of the computer, and operates as the system time generation unit 2, time information processing unit 4, time accuracy monitoring unit 5, time variation function calculation unit 6, drift adjustment parameter acquisition unit 7, and drift adjustment parameter calculation unit 8 according to the time maintenance program.
[0035] Next, the prerequisite settings are shown.
[0036] The time information processing unit 4 can acquire satellite time information to be used as a reference. The time information processing unit 4 is set up so that it can acquire satellite time information (GNSS time information).
[0037] For the time accuracy monitoring unit 5, a threshold value (a threshold value to be compared with the absolute value of the time difference) used when determining whether or not to update the drift adjustment parameter of the atomic clock 1 is defined in advance.
[0038] The predetermined period that defines the time difference information used by the time change function calculation unit 6 to calculate the time change function and the method for generating the time change function are determined in advance.
[0039] With regard to the drift adjustment parameter calculation unit 8, an algorithm is determined in advance to calculate the value of the drift adjustment parameter so that the difference between the satellite time and the system time is close to 0 and the update interval of the drift adjustment parameter is the longest under the conditions of the frequency characteristics of the atomic clock 1. The drift adjustment parameter calculation unit 8 uses the determined algorithm.
[0040] Next, the process flow of the system according to the present disclosure will be described. Fig. 2 is a schematic diagram showing an example of the process flow of the system according to the present disclosure.
[0041] The atomic clock 1 generates periodic information with a certain degree of accuracy. The generated periodic information is input to the system time generation unit 2.
[0042] The system time generation unit 2 generates a system time that is synchronized with the fixed period information generated by the atomic clock (step S1). The generated system time is input to the time information processing unit 4.
[0043] The positioning satellite 3 broadcasts satellite time information (GNSS time information) that indicates the satellite time of the positioning satellite 3. The broadcasted satellite time information becomes an input to the time information processing unit 4.
[0044] The time information processing unit 4 calculates time difference information indicating the difference between the system time and the satellite time indicated by the satellite time information, and outputs the time difference information (step S2). The time difference information is input to the time accuracy monitoring unit 5.
[0045] The time accuracy monitoring unit 5 accumulates the real-time time difference information sent from the time information processing unit 4 and stores all time difference information from the past to the present. Based on the stored time difference information, the time accuracy monitoring unit 5 also determines whether or not to update the drift adjustment parameters of the atomic clock 1 depending on whether the absolute value of the difference indicated by the time difference information is equal to or less than a preset threshold value or whether the absolute value of the difference indicated by the time difference information exceeds that threshold value (step S3).
[0046] If the absolute value of the difference exceeds the threshold value (NO in step S4), the time difference information is used as an input to the time change function calculation unit 6.
[0047] If the absolute value of the difference is equal to or less than the threshold value (YES in step S4), the time keeping device 10 does not update the drift adjustment parameters of the atomic clock 1.
[0048] When the time accuracy monitoring unit 5 determines that the drift adjustment parameter should be updated, the time change function calculation unit 6 acquires time difference information for a predetermined period from the past to the present (time difference information from before the predetermined period to the present) from the time accuracy monitoring unit 5. Based on the acquired time difference information, the time change function calculation unit 6 calculates an approximation function (time change function) that indicates the change in the difference over time (the difference between the satellite time and the system time) using the least squares method (step S5). The calculated time change function is input to the drift adjustment parameter calculation unit 8.
[0049] When linear approximation is used to calculate the approximation function, it is necessary to set an appropriate period of time difference information to be used in advance in order to accurately predict the difference change.
[0050] The drift adjustment parameter acquisition unit 7 acquires the drift adjustment parameters (drift adjustment parameters set at that time) before updating the period information generated in the atomic clock 1 (step S6). The drift adjustment parameters acquired from the atomic clock 1 are input to the drift adjustment parameter calculation unit 8.
[0051] The drift adjustment parameter calculation unit 8 calculates the value of the drift adjustment parameter to be newly set using the time change function and the drift adjustment parameter before update. At this time, the drift adjustment parameter calculation unit 8 calculates the value of the drift adjustment parameter to be newly set so that the difference between the satellite time and the system time is close to 0 and the update interval of the drift adjustment parameter is the longest under the conditions of the frequency characteristics of the atomic clock 1 (step S7). The drift adjustment parameter calculation unit 8 sets the newly calculated value of the drift adjustment parameter in the atomic clock 1.
[0052] This embodiment makes it possible to calculate a time variation function using time difference information and update the drift adjustment parameter at intervals. This allows the system time to be maintained with high accuracy at low cost. Therefore, in an orbit determination or orbit estimation system that requires the use of independent time information (satellite time and system time) due to its characteristics, the system time can be maintained with high accuracy at low cost.
[0053] Next, a modified example will be described.
[0054] The satellite time (GNSS reference time) used as a reference in the time information processing unit 4 can be replaced with any GNSS reference time as long as the prerequisites are met. Furthermore, the system disclosed herein can be applied to all systems that require a reference time distributed as time information to be synchronized, in addition to artificial satellites.
[0055] The threshold used by the time accuracy monitoring unit 5 may be not only a threshold to be compared with the difference between the satellite time (GNSS reference time) and the system time, but also a threshold to be compared with the amount of change in the difference.
[0056] When creating the time change function, the time change function calculation unit 6 is not limited to the least squares method, and may use a regression analysis method.
[0057] 3 is a block diagram showing an example of the configuration of a computer related to the time keeping device. The computer 2000 includes, for example, a CPU 2001, a main memory device 2002, an auxiliary memory device 2003, an interface 2004, and an atomic clock 2005.
[0058] The time keeping device according to the present disclosure is realized, for example, by a computer 2000. The operation of the time keeping device is stored in the form of a program (time keeping program) in an auxiliary storage device 2003. A CPU 2001 reads the program from the auxiliary storage device 2003, loads the program into a main storage device 2002, and executes the processing described in the above embodiment in accordance with the program.
[0059] The auxiliary storage device 2003 is an example of a non-transitory tangible medium. Other examples of non-transitory tangible media include a magnetic disk, a magneto-optical disk, a CD-ROM (Compact Disk Read Only Memory), a DVD-ROM (Digital Versatile Disk Read Only Memory), and a semiconductor memory connected via the interface 2004.
[0060] Next, an overview of the time keeping device according to the present disclosure will be described. Fig. 4 is a block diagram showing an overview of the time keeping device according to the present disclosure. The time keeping device comprises a system time generating means 72, a time information processing means 74, a time variation function calculating means 76, and a drift adjustment parameter calculating means 78.
[0061] The system time generating means 72 (for example, the system time generating unit 2) generates the system time as a time synchronized with the period information generated by the atomic clock.
[0062] The time information processing means 74 (for example, the time information processing unit 4) outputs time difference information indicating the difference between the reference time, which is the time serving as a reference value, and the system time.
[0063] The time change function calculation means 76 (for example, the time change function calculation unit 6) calculates an approximate function that indicates the change in the difference over time based on the time difference information for a predetermined period.
[0064] The drift adjustment parameter calculation means 78 (for example, the drift adjustment parameter calculation unit 8) calculates the value of the drift adjustment parameter using the approximation function and the pre-update drift adjustment parameter of the atomic clock.
[0065] Such a configuration allows system time to be maintained with high accuracy at low cost.
[0066] The above embodiment can also be described as follows, but is not limited to the following:
[0067] (Appendix 1) a system time generating means for generating a time synchronized with the periodic information generated by the atomic clock as a system time; a time information processing means for outputting time difference information indicating the difference between a reference time, which is a time serving as a reference value, and the system time; a time change function calculation means for calculating an approximation function indicating a change in the difference over time based on the time difference information for a predetermined period; a drift adjustment parameter calculation means for calculating the value of the drift adjustment parameter by using the approximation function and the drift adjustment parameter before updating of the atomic clock; A time keeping device characterized by:
[0068] (Appendix 2) a time accuracy monitoring means for determining whether or not to update a drift adjustment parameter of the atomic clock based on the time difference information and a predetermined threshold value; The time change function calculation means When it is determined that the drift adjustment parameter is to be updated, the approximation function is calculated; The drift adjustment parameter calculation means When it is determined that the drift adjustment parameter is to be updated, the value of the drift adjustment parameter is calculated. 2. The timekeeping device of claim 1.
[0069] (Appendix 3) The reference time is the satellite time broadcast from a positioning satellite. 2. The timekeeping device of claim 1.
[0070] (Appendix 4) The drift adjustment parameter calculation means The value of the drift adjustment parameter is calculated so that the difference is close to 0 and the update interval of the drift adjustment parameter is the longest under the conditions of the frequency characteristics of the atomic clock. 2. The timekeeping device of claim 1.
[0071] (Appendix 5) The time accuracy monitoring means When the absolute value of the difference indicated by the time difference information exceeds the threshold, it is determined that the drift adjustment parameter is to be updated. 10. The timekeeping device of claim 2.
[0072] (Appendix 6) The computer Generates a system time that is synchronized with the periodic information generated by the atomic clock, outputting time difference information indicating the difference between a reference time, which is a time serving as a reference value, and the system time; calculating an approximation function that indicates a change in the difference over time based on the time difference information for a predetermined period of time; Calculating the value of the drift adjustment parameter using the approximation function and the drift adjustment parameter before updating of the atomic clock A time keeping method characterized by:
[0073] (Appendix 7) On the computer, a system time generation process for generating a system time that is synchronized with the periodic information generated by the atomic clock; a time information process for outputting time difference information indicating the difference between a reference time, which is a time serving as a reference value, and the system time; a time change function calculation process for calculating an approximation function indicating a change in the difference over time based on the time difference information for a predetermined period; and a drift adjustment parameter calculation process for calculating the value of the drift adjustment parameter using the approximation function and the drift adjustment parameter before updating of the atomic clock; A timekeeping program to run.
[0074] Some or all of the configurations described in Supplementary Notes 2 to 5, which are dependent on Supplementary Note 1, may also be dependent on Supplementary Notes 6 and 7 in the same dependent relationship as Supplementary Notes 2 to 5. Furthermore, not limited to Supplementary Notes 1, 6, and 7, some or all of the configurations described as Supplements may be made dependent on various hardware, software, various recording means for recording software, or systems, within the scope of the above-described embodiment.
[0075] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. [Explanation of symbols]
[0076] 1. Atomic clock 2 System time generation unit 3. Positioning satellites 4 Time information processing section 5 Time accuracy monitoring section 6 Time-varying function calculation section 7 Drift adjustment parameter acquisition section 8. Drift adjustment parameter calculation section 10 Time keeping device
Claims
1. a system time generating means for generating a time synchronized with the periodic information generated by the atomic clock as a system time; a time information processing means for outputting time difference information indicating the difference between a reference time, which is a time serving as a reference value, and the system time; a time change function calculation means for calculating an approximation function indicating a change in the difference over time based on the time difference information for a predetermined period; a drift adjustment parameter calculation means for calculating the value of the drift adjustment parameter by using the approximation function and the drift adjustment parameter before updating of the atomic clock; A time keeping device characterized by:
2. a time accuracy monitoring means for determining whether or not to update a drift adjustment parameter of the atomic clock based on the time difference information and a predetermined threshold value; The time change function calculation means When it is determined that the drift adjustment parameter is to be updated, the approximation function is calculated; The drift adjustment parameter calculation means When it is determined that the drift adjustment parameter is to be updated, the value of the drift adjustment parameter is calculated.
2. The time keeping device of claim 1.
3. The reference time is the satellite time broadcast from a positioning satellite.
2. The time keeping device of claim 1.
4. The drift adjustment parameter calculation means The value of the drift adjustment parameter is calculated so that the difference is a value close to 0 and the update interval of the drift adjustment parameter is the longest under the conditions of the frequency characteristics of the atomic clock.
2. The time keeping device of claim 1.
5. The time accuracy monitoring means When the absolute value of the difference indicated by the time difference information exceeds the threshold, it is determined that the drift adjustment parameter is to be updated.
3. The time keeping device of claim 2.
6. The computer Generates a system time that is synchronized with the periodic information generated by the atomic clock, outputting time difference information indicating the difference between a reference time, which is a time serving as a reference value, and the system time; calculating an approximation function that indicates a change in the difference over time based on the time difference information for a predetermined period of time; Calculating the value of the drift adjustment parameter using the approximation function and the drift adjustment parameter before updating of the atomic clock A time keeping method characterized by:
7. On the computer, a system time generation process for generating a system time that is synchronized with the periodic information generated by the atomic clock; a time information process for outputting time difference information indicating the difference between a reference time, which is a time serving as a reference value, and the system time; a time change function calculation process for calculating an approximation function indicating a change in the difference over time based on the time difference information for a predetermined period; and a drift adjustment parameter calculation process for calculating the value of the drift adjustment parameter using the approximation function and the drift adjustment parameter before updating of the atomic clock; A timekeeping program to run.
Citation Information
Patent Citations
Monitoring of multi-level / multi-threshold / multi-persistence GPS / GNSS atomic clock
JP2016191551A