JP2842029B2 - Error correction device for timekeeping means - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an error correcting device for a time measuring means used in a computer or the like. In recent years, artificial satellites,
Particularly in computer systems mounted on academic satellites, even under severe environmental conditions, the need to record events occurring in space at an accurate time requires particularly high precision and small timekeeping means.

For this reason, an error correction device for a clock means is required to correct the clock means, whose operation changes due to severe environmental conditions and which causes an error from the actual time, to obtain an accurate time.

[0003]

2. Description of the Related Art A time counting means or a timer (hereinafter referred to as a clock) counts pulses based on the frequency of an oscillator with a counter or the like, and outputs time or time when the counted value reaches a predetermined number. For example, when the nominal frequency of the oscillator specified in the specification is 100,000 Hz, the clock is configured to count one second when counting 100,000 pulses. However, the oscillation frequency of an oscillator is greatly affected by environmental conditions, especially changes in temperature, and even if the same oscillator with a nominal frequency of 100,000 Hz oscillates at a frequency of 100,010 Hz, it oscillates at 99,990 Hz. In some cases.

Therefore, when a prescribed number of pulses 100,000 are counted, an error of 1 / 10,000 seconds is generated. Conventionally, in order to reduce the influence of such environmental changes and reduce clock errors, the oscillator is placed in a constant temperature bath, etc., and the ambient temperature of the oscillator is kept constant while the power to the clock is kept on. The way to keep was taken.

[0005] Further, a correction method instead of the above method is as follows.
Japanese Patent Application No. 03-087 filed by the applicant on April 19, 1991
993 There is a "timer error correction circuit" (hereinafter referred to as the correction method of the prior application), and the correction method will be briefly described here. First, the frequency characteristics of the frequency that changes depending on the temperature of the oscillator used in the watch are acquired in advance, and a temperature-frequency table is created. If the temperature is known, the frequency of the oscillator can be predicted from the temperature-frequency table. .

On the other hand, a temperature sensor using a thermistor is attached to an oscillator used in the timepiece so that the temperature of the oscillator can be obtained at any time. Then, the temperature of the oscillator at the start of the correction and the actual frequency are measured, and thereafter, the temperature of the oscillator at the start of the correction and the current temperature of the oscillator are applied to a previously created temperature-predicted frequency table, and the oscillator at the start of the correction is obtained. A change in the frequency from the frequency of the oscillator at the start of the correction is estimated based on the temperature change from the temperature of (i), and the current frequency of the oscillator is predicted.

[0007] The difference between the nominal frequency of the oscillator and the predicted frequency of the oscillator every second is accumulated, and the difference between the time indicated by the clock and the accumulated frequency and the nominal frequency of the oscillator is corrected to correspond to the time indicated by the clock. Find the time.

[0008]

As described above, according to the conventional method, the oscillator is placed in a constant temperature bath or the like in order to keep the environmental conditions of the oscillator constant. In addition to increasing the clock size and increasing the size of the watch, especially in a severe environment, such as when it is mounted on an aircraft or satellite, a stable operating environment for the oscillator can be achieved even with a constant temperature bath. Can not give,
There was a problem that a highly accurate timepiece could not be realized.

In the correction method of the prior application, the actual frequency and temperature of the oscillator are measured at the start of correction, and then the temperature of the oscillator at the start of correction and the temperature of the oscillator at each time are applied to a temperature versus predicted frequency table. The frequency difference between the oscillator at the start of correction and the time at each time is obtained from the temperature difference between the oscillator at the start of correction and the time at each time, and the predicted frequency of the oscillator at each time is obtained from the frequency at the start of correction and the obtained frequency difference. Ask.

However, the predicted frequency of the oscillator with respect to the temperature obtained from the temperature versus predicted frequency table does not always match the actual frequency of the oscillator due to environmental conditions and the like. Therefore, in the correction method of the prior application, an error occurs between the frequency of the oscillator predicted from the temperature and the frequency of the actual oscillator at each time, and the error is accumulated as time elapses, so that the time after correction becomes It will be different from the real time.

Furthermore, in the above-mentioned correction method, since the actual frequency of the oscillator at the start of the correction must be measured, if the frequency of the oscillator used in the timepiece cannot be measured due to cost or technical problems, Clock correction cannot be performed using the correction method described above. SUMMARY OF THE INVENTION It is an object of the present invention to provide a small and economical error correcting device for a timekeeping means for realizing a highly accurate timekeeping means even under severe environmental conditions.

[0012]

FIG. 1 is a diagram illustrating the principle of the present invention. In the figure, reference numeral 1 denotes an oscillator having a predetermined nominal frequency. Reference numeral 2 denotes a time measuring means for measuring time based on the oscillator 1. 3 is a computing means, a 'predicted frequency g of the oscillator 1 in _s and clock means 2 is the time indicated' predicted frequency F of the oscillator 1 at correction start (t)

[0013]

(Equation 4) Is what you want. 4 is a correction means,
The correct correction start time and correction end time given from other than the time indicated by the clock means 2, the nominal frequency of the oscillator 1, and the time indicated by the clock means 2 are corrected from the output of the arithmetic means 3.

Numeral 5 is a frequency predicting unit, which changes the frequency of the oscillator 1 depending on the temperature change, and outputs a frequency predicted by the temperature change as a predicted frequency of the oscillator 1.

[0015]

According to the present invention, the correction is performed based on the time indicated by the clock at the start and end of the correction and the true time, that is, the time indicated by the clock at the start and end of the correction and the real time corresponding to the time. Is corrected so that the error with respect to 0 becomes zero .
Therefore , it is possible to suppress the accumulation of the error between the frequency of the oscillator predicted at each time and the actual frequency of the oscillator, which has occurred in the correction method of the prior application, and to correct the time indicated by the clock and the true time. Is reduced.

In the correction method of the prior application, if the actual frequency of the oscillator at the start of correction cannot be measured, it is impossible to correct a clock error using the correction method. According to the present invention, the actual frequency of the oscillator at the start of correction is obtained from the time indicated by the clock, the real time corresponding thereto, the nominal frequency of the oscillator, and the predicted frequency of the oscillator, so that the oscillator frequency at the start of correction is measured. The correction can be performed without any necessary equipment.

[0017]

FIG. 2 is a diagram showing an embodiment of the present invention. FIG.
FIG. 6 is a diagram showing creation of a temperature versus predicted frequency table. Clock 12 shown in FIG. 2, crystal oscillator 11 (nominal frequency F ₀
) Is counted, and the time is output. For example, when the oscillation frequency of the crystal oscillator 11 is 100,000 Hz, a time of one second is output by counting 100,000 pulses.

The crystal oscillator 11 has a built-in thermistor 13 exhibiting a resistance value that varies depending on the temperature so that the temperature can be obtained in real time. The crystal oscillator 11 has a shunt resistor 14 and an analog / digital converter 15 (hereinafter, referred to as an analog / digital converter).
ADC) and the thermistor 13
And the shunt resistor 14 are connected in series between the + 5V and 0V power supplies, so that the thermistor 13 and the shunt resistor 1 are connected.
4 is configured to change in accordance with a temperature change of the crystal oscillator 11. By inputting an analog voltage value indicating this potential to the ADC 15, the temperature of the crystal oscillator 11 is output as a digital value.

The frequency predicting unit 5 has a table of the digital value of the temperature versus the predicted frequency (or a read-only memory ROM for storing the predicted frequency in a storage location having the digital value of the temperature as an address), and is an output from the ADC 15. With the digital value of the temperature as an input, a predicted frequency g (T) accompanying a temperature change of the crystal oscillator 11 is output in real time. In this table, as shown in FIG. 3, the crystal oscillator 11 (with the thermistor 13) is placed in a thermostat, and the output of the crystal oscillator 11 is connected to the frequency measuring device 18. In this state, the temperature of the thermostat is changed, and a temperature-predicted frequency table in which the digital value of the temperature (the output of the ADC 15) obtained by the temperature and the oscillation frequency of the crystal oscillator 11 are made to correspond to each other is stored in a memory in advance. Keep it.

As shown in FIG. 2, the calculating means 3 comprises a subtractor 16 and an accumulation counter 17, and the subtractor 16 outputs the predicted frequency output from the frequency predicting section 5 at the start of correction and the current predicted frequency. Is calculated, and the difference is accumulated in the accumulation counter 17. When determining the time at the moment when the user wants to record, the real time at the start and end of the correction and the clock 1
2, the nominal frequency of the crystal oscillator 11, the integrated value of the integrating counter 17 from the start of correction to the moment at which recording is desired, and the integrated counter 1 from the start of correction to the end of correction.
With the integrated value of 7 as an input, the correction unit 4 calculates and outputs a real time corresponding to the time indicated by the clock 12 at the moment of recording.

As described above, in this embodiment, the calculating means 3
Is a process in which the correction start time output from the frequency prediction unit 5 and the current predicted frequency are input, the subtractor 16 obtains the difference between them, and the difference is integrated by the integration counter 17. As another process of 3, assuming that the correction start time output from the frequency prediction unit 5 and the current predicted frequency are input, the integration counter 17 integrates the predicted frequencies at each time from the correction start time to the correction end time, When the correction is completed, the subtractor 16 subtracts the predicted frequency at the start of the correction by the elapsed time from the start of the correction at the time indicated by the clock to the end of the correction from the integrated value of the integration counter 17. It is.

Here, a method of correcting an error of the timepiece 12, which is a feature of the present invention, will be described. FIG. 4 is a diagram showing a frequency change of the oscillator. In FIG. 4, g (T): predicted frequency F _S of the crystal oscillator 11 frequency SPS _E correction starting crystal oscillator 11: elapsed time (time indicating clock 12) from the time correction start to the correction end T _E : Elapsed time (real time) from the start of correction to the end of correction, where g (T) can be predicted without error from the actual frequency of the crystal oscillator 11.

FIG. 4 shows the crystal oscillator 11 over time.
The horizontal axis indicates the elapsed time from the start of the correction at the real time, and the vertical axis indicates the frequency of the crystal oscillator 11, with the origin being the start of the correction. In FIG. 4, a vertical dotted line indicates a time interval of one second by the clock 12. SPS ₁ , SPS ₂ ,..., SPS ₅ indicate that the clock 12 has elapsed 1, 2,.
Time SPS _1, SPS ₂ indicated, ..., T _1, T ₂ a real time on the horizontal axis corresponding to the SPS _5, ..., shown by the T _5.

Therefore, the intervals between the dotted lines are not equal with respect to the real time axis. That is, the predicted frequency g (T) is equal to the nominal frequency F ₀
If higher, the clock 12 indicates 1 second before the real time has elapsed 1 second (clock advances), and if the predicted frequency g (T) is lower than the nominal frequency F ₀ , the real time has elapsed 1 second. Later, the clock 12 indicates one second (clock lags). The present invention first obtains the frequency F _s of the crystal oscillator 11 at the start of correction so that the time indicated by the clock at the end of correction and the real time correspond without error, and obtains the calculated frequency F _s of the crystal oscillator 11 at the start of correction. _s
And the difference between the predicted frequency g (T) per second and the predicted frequency of the crystal oscillator 11 at the start of the correction is calculated until the end of the correction, the difference is integrated, and the integrated value and the frequency of the crystal oscillator 11 at the start of the correction are calculated. It performs a correction of the clock 12 from F _s, determine the real time corresponding to the time indicated by the clock 12 at the moment you want to record the exact time.

[0025] First of all, describe the method of determining the frequency F _S of correction at the start of the crystal oscillator 11. Assuming that the real time at the start of the correction and the end of the correction and the time indicated by the clock 12 are obtained, the elapsed time indicated by the clock 12 from the start of the correction to the end of the correction is represented by SPS.
_Assuming that _E , the elapsed time at the real time is T _E , and the predicted frequency of the crystal oscillator 11 is g (T), the area between the curve g (T) and the horizontal axis in FIG. is actually the total number of pulses output (integrated value), also a product of the elapsed time SPS _E at the time indicated by the clock 12 and the nominal frequency F _0, the following equation holds.

[0026]

(Equation 5) In FIG. 4, the predicted frequency g (T) of the crystal oscillator 11 is shown.
Curves the area of a portion that varies above and below with respect to the straight line F _S is the frequency of the crystal oscillator 11 during correction start, respectively, stored as a frequency difference between the frequency F _S of the crystal oscillator 11 during correction start and the difference between the sum of the pulse number by the predicted frequency g (T) of the crystal oscillator 11 at every second from the time correction start frequency F _S of the correction at the start of the crystal oscillator 11 until the correction completed,

[0027]

(Equation 6) Becomes Here, g (t) and F _S on the right side of Formula 2 be those determined from the temperature versus predicted frequency table, it can not always be predicted actual frequency and no error of the crystal oscillator 11 as described above.

However, the right side shows the crystal oscillator 1 per second.
A difference accumulated in the frequency of the first frequency and the correction start of the crystal oscillator 11, the frequency of the case where it is predicted actual frequency and no error of the crystal oscillator 11 g (t) and F _S, the crystal oscillator 11 the frequency was determined from the temperature versus predicted frequency table, as the actual frequency and the predicted frequency that might introduce errors g '(t) and F' _S, almost uniquely the frequency change of the crystal oscillator 11 due to temperature changes G (t) and F _S
The difference of the difference and g '(t) and F' _S of the following expression holds by almost the same value is obtained.

[0029]

(Equation 7) Substituting equation 3 into equation 2 and transforming it further,

[0030]

(Equation 8) And from Equations 1 and 4,

[0031]

(Equation 9)

[0032]

(Equation 10) Becomes The right side of Expression 5 is a value obtained by integrating the difference between the predicted frequency of the crystal oscillator 11 per second and the predicted frequency of the crystal oscillator 11 at the start of correction from the start of correction to the end of correction. From the temperature of the crystal oscillator 11 per second from the difference between the temperature of the crystal oscillator 11 and the temperature of the crystal oscillator 11 per second.

[0033] Thus, the nominal frequency F ₀ of the elapsed time of the elapsed time SPS _E and the real time indicated by the clock 12 from the time of correction start to the correction end T _E and the crystal oscillator 11 is known, the right-hand side of equation (5) for even values are known as described above, it is possible to obtain the frequency F _S of the crystal oscillator 11 at the correction start from equation 6. From Equation 6, the crystal oscillator 11 at the start of correction
Since Motoma' of frequency F _S is, then, how to obtain real time corresponding to the time at which the clock 12 at the moment you want to record by using the F _S obtained showed described.

Assuming that the elapsed time from the start of correction at the time indicated by the clock 12 is N and the elapsed time from the start of correction at the true time at that time is T _N , Equations 1, 2 and 3 are obtained. From Equation 4,

[0035]

[Equation 11]

[0036]

(Equation 12) , And from equations 7 and 8,

[0037]

(Equation 13)

[0038]

[Equation 14] Since each value other than T _N is known, Equation 1
The elapsed time T _N at the real time corresponding to the elapsed time N from the correction start at the time indicated by the clock 12 from 0 can be obtained, and the real time at the start of the correction and the obtained elapsed time
The real time at the moment you want to record can be obtained from T _N.

FIG. 5 is a flowchart of the present invention. (1) Temperature of crystal oscillator 11 at start of correction, clock 12
, The real time is acquired, the integration counter 17 is cleared, and the integrated value of the frequency difference is set to zero (S in FIG. 5).
1). (2) Every second at the time indicated by the clock 12, the crystal oscillator 1
1 (S2 in FIG. 5), and inputs the temperature of the crystal oscillator 11 at the start of correction and the current temperature of the crystal oscillator 11 to the temperature versus predicted frequency table to obtain the predicted frequency of the crystal oscillator 11 at the start of correction and the current. The frequency difference is obtained by the subtractor 16, integrated in the integrating counter and stored (S3 in FIG. 5). (3) At the moment when you want to record an accurate time (S in FIG. 5)
5) The integrated value of the integrating counter and the time indicated by the clock 12 at that time are recorded (S6 in FIG. 5). (4) Steps (2) and (3) are repeated until the correction is completed (S4 in FIG. 5). (5) The real time at the end of the correction, the time indicated by the clock 12, and the integrated value of the integrating counter are acquired (S7 in FIG. 5). (6) The frequency of the crystal oscillator 11 at the start of the correction is obtained from the real time at the end of the correction, the time indicated by the clock 12, the integrated value of the integrating counter, and the nominal frequency of the crystal oscillator 11 (S8 in FIG. 5). (7) The time indicated by the clock 12 at the moment when an accurate time is to be recorded, the integrated value of the integrating counter acquired at that time,
From the frequency of the crystal oscillator 11 at the start of the correction obtained in (6) and the nominal frequency of the crystal oscillator 11, a real time corresponding to the time indicated by the clock 12 at the moment to record is obtained (S9 in FIG. 5).

As an application example of the present invention, a case where the time indicated by a clock mounted on an artificial satellite is corrected will be described.
When correcting the time indicated by the clock mounted on the satellite, the thermistor is attached to the clock of the satellite as described above, and the temperature of the oscillator used in the clock is obtained at any time by the thermistor, shunt resistor, and ADC. The satellite is provided with a frequency prediction unit, a subtractor, an integration counter, and a correction unit in the ground station.

First, when correction is started when communication with the artificial satellite is started, the integration counter of the artificial satellite is cleared to make the integrated value zero, and the time indicated by the clock at the start of correction, the time on the ground, and the time used by the clock. Get the temperature of the oscillator that is running.
Then, when communication with the artificial satellite is not possible, the temperature of the oscillator at the start of correction and the time at each time are applied to the temperature vs. predicted frequency table of the frequency predicting unit every second, and the predicted frequency for each temperature is obtained and subtracted. Calculator calculates the frequency difference between the predicted frequency of the oscillator at the start of correction and at each time,
The frequency difference is accumulated in the accumulation counter.

When an event occurring in space by an artificial satellite is recorded by a photograph or the like, at the same time, the time indicated by the clock mounted on the artificial satellite and the value of the integration counter at that time are used as data for correction as artificial data. Record on the satellite.
When communication with the satellite again becomes possible, the time at which the correction is completed and the time indicated by the clock at the end of the correction and the time on the ground are obtained, and the time for the correction stored in the satellite from the start of the correction to the end of the correction is obtained. Data is transmitted from the satellite to the ground station.

In the ground station receiving the data from the artificial satellite, the correction unit obtains the frequency of the oscillator at the start of the correction from the received data and the like as described above, and stores a clock stored as the data for correction. The indicated time is corrected, and a time on the ground corresponding to the time is obtained. In the present embodiment, an example has been described in which the difference between the current predicted frequency of the crystal oscillator and the predicted frequency of the crystal oscillator at the start of correction is calculated at one-second intervals and integrated and corrected, but the operation is performed more frequently. This makes it possible to correct the time indicated by the clock with higher accuracy.

Further, in the present embodiment, the description has been given of obtaining the true time corresponding to the time indicated by the clock at the moment when the accurate time is to be recorded. However, it corresponds to the time indicated by the clock every second. It is also possible to find the real time. In an experiment to which the present embodiment was applied, the error was 1/1000 as compared with a conventional timepiece that measures time assuming that an actual oscillation frequency is constant at a nominal frequency, that is, an uncorrected case. This result makes it possible to reduce the error to one tenth as compared with the result corrected by the correction method of the prior application.

[0045]

According to the present invention, in a timing means for timing based on an oscillator having a predetermined nominal frequency, the oscillation frequency of the oscillator is predicted based on external conditions, and the predicted frequency at each time and the correction start time The difference from the predicted frequency of the oscillator is calculated and accumulated, and the accumulated time is used to correct the time indicated by the timekeeping means. Therefore, a highly accurate, small, and economical time measuring means can be realized.

Also, Japanese Patent Application No. 03-08799 filed by the present applicant
Since the time indicated by the clock means is corrected while suppressing the accumulation of errors between the predicted oscillator frequency and the true oscillator frequency as occurred in step 3, the time after the time indicated by the clock means is corrected. And the difference between the time and the real time can be reduced.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention.

FIG. 3 is a diagram showing creation of a temperature versus predicted frequency table.

FIG. 4 is a diagram showing a frequency change of an oscillator.

FIG. 5 is a flowchart of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oscillator 2 Clocking means 3 Computing means 4 Correcting part 5 Frequency predicting part 11 Crystal oscillator 12 Clock 13 Thermistor 14 Shunt resistor 15 Analog-digital converter (ADC) 16 Subtractor 17 Integration counter 18 Frequency measuring instrument

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) G04G 3/00 G04D 7/00

Claims (5)

(57) [Claims] 1. A error correcting device counting means for counting based on an oscillator having a predetermined nominal frequency, the a predicted frequency F _'S of the oscillator at the correction start
Predicted frequency g '(t) of the oscillator at time t indicated by the clock means
From (Equation 1) Calculating means for obtaining and a correct correction start time and the correction end time given from the other time and the regimen time unit indicated by the clock means, and the nominal frequency of the oscillator <br/>, the regimen time means from an output of said arithmetic means An error correction device for timekeeping means, comprising: correction means for correcting the time indicated by: Wherein said correction means, the nominal frequency of the oscillator F0, the predicted frequency F _'S of the oscillator at the correction start, the
The predicted frequency of the oscillator g '(t), the elapsed time SPS _E from the correction start time indicated by the clock means to correction end time, elapsed time from the correct correction start time to the correction end time T
_In the case of _E , the elapsed time at the correct time with respect to the elapsed time N from the correction start time indicated by the timing means is expressed by the following equation. (Equation 3) 2. The error correcting device of the time measuring means according to claim 1, wherein the error is obtained as: 3. The oscillator according to claim 1, wherein a change in frequency of the oscillator depends on a change in temperature, and a frequency prediction unit that outputs a frequency predicted by the change in temperature as a predicted frequency of the oscillator. Claim 1 or Claim 2
An error correction device for the timekeeping means described. Wherein said timer means is a intended to be mounted on an artificial satellite, the time counting hand by the correction means provided on the ground
4. An error correcting device for a time measuring means according to claim 1, wherein a correct time is obtained by correcting the time indicated by the step . 5. The method according to claim 1, wherein the calculating unit is configured to perform a correction before starting the correction.
The in time indicated by the predicted frequency and the clock means of the serial oscillator
5. An error correction device for a timekeeping means according to claim 1, wherein a difference from a predicted frequency of the oscillator is integrated.