JPH0658606B2 - Forecast data supply device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention, like a control system for an artificial satellite tracking antenna, provides a series of forecast data of control positions in time series from a central station to a remote station control device. The present invention relates to a program control system for sequentially supplying data to a remote station, and particularly, a forecast data supply device that adjusts the data interval so that the error of the forecast data supplied to a remote station is within a certain allowable range and minimizes the amount of forecast data supply Regarding

[Conventional technology]

There is a program tracking method as one of control methods when an artificial satellite equipped with a probe such as Landsat is tracked by an antenna from an observation station on the ground. This method creates forecast data at fixed time intervals for the azimuth angle, elevation angle, etc. of the tracking antenna placed on the ground, programs them, and drives the antennas sequentially based on this forecast data. .

FIG. 2 schematically shows such an artificial satellite tracking system, in which 1 is an artificial satellite, 2 is a ground station, 3 is an antenna, 4 is an observation center, and 5 is a transmission line.

Normally, the antenna 3 and the observation center 4 are geographically distant from each other, and the observation center 4 transmits the series of forecast data for driving the antenna 3 to the antenna 3 via the transmission line 5. The antenna 3 applies an interpolation method to a series of received forecast data to interpolate an intermediate value, controls the antenna drive system, and continuously adjusts the azimuth angle, the elevation angle, and the like of the antenna to target values. In this case, the forecast data interval is fixed, for example, every 60 seconds.

FIG. 3 shows an example of forecast data string and interpolation regarding the elevation angle supplied to the antenna. t _n-1 , t _n ,
t _{n + 1} indicates a forecast time, d _n−1 , d _n , and d _{n + 1} indicate forecast data strings, and r _n−1 and r _n indicate linear interpolated result values. Note that S _n-1 and S _n represent the true elevation value of the artificial satellite. The error between the linear interpolation result value and the true elevation angle value is called an interpolation error.

That is, the interpolation error referred to here is two times (t, t +) received by the control device that directly controls the driving of the antenna drive system.
Each predictor in Delta] t) (f _t, which means the control deviation of the local elevation generated by interpolating (interpolation) in linear approximation values between _{f t + Δ t).}

[Problems to be solved by the invention]

The tracking error of the antenna largely depends on the interpolation error. Therefore, in order to improve the tracking accuracy, it is necessary to shorten the data interval of the forecast data.

However, for that purpose, there is a problem that the amount of forecast data supplied to the antenna via the transmission line increases.

[Means for solving problems]

In the present invention, the interpolation error in the controlled object in the program control system generally differs depending on the control position. For example, in the case of the antenna for tracking the artificial satellite described above, the change rate near the horizon is smaller than the change rate near the maximum elevation angle. Therefore, when linear interpolation is performed with a fixed data interval,
Focusing on the fact that the interpolation error is larger near the zenith than near the horizon, rather than shortening the data interval of the forecast data uniformly when improving the accuracy, an approximate calculation is performed from the values of the forecast data and past forecast data. The data interval is changed according to the local error of the difference with the value, and if the error amount is small, the data interval is extended, and if the error amount is large, the data interval is shortened, and the increase of the forecast data amount supplied as a whole is suppressed. It was made possible. Note "local error" as referred to herein, in FIG. 6 to be described later, the time after the data interval Δt from a past time _{t n (t n + Δ n} ) in the predictor _{f (t n + Δ t)} , forecast value f (t at t _n
n ), its first derivative f (t _n ), and an error Δ between the value f ^* (t _n ) extrapolated by linear approximation using Δt.
f. This local error is a data interval Δ for gradually reducing the interpolation error generated in the control device of the antenna drive system.
It is used as an index for adjusting t.

Then, the configuration of the device of the present invention based on it is such that, with respect to the control device (13) that controls the control target device using the supplied forecast data and the forecast data obtained by interpolating the values between the forecast data as control information, A forecast data supply device that supplies the forecast data, comprising: a forecast data creation unit (7) that creates and supplies a forecast value ( _ft ) based on time (t); and the forecast data creation at time (n). The forecast value (f _n ) supplied from the section (7) and at least the past time (n
An error output unit (9) for outputting a deviation (Δf) from a forecast approximate value (f ^* _n ) at time (n) extrapolated from the forecast value (f _n−1 ) of −1), and the error output unit. Allowable range of deviation (ε) output by (9)
₁ ), (epsilon ₂ ), a deviation (Δf) from the error output (9), and an allowable range value (ε ₁ , ε ₂ ) from the error output (8). ) And a time determination unit (10) that updates the time interval input to the forecast data creation unit (7) according to the determination result, and the control device (13) provides a forecast. It is characterized in that the step size of the time when the data is supplied is variably and optimally controlled.

[Operation of the invention]

If the time of the forecast data in the program control system is represented by t and the control function is represented by El (t), the time derivative l (t) of El (t) can be given by an analytical formula. Considering this as the initial value problem of the first-order ordinary differential equations l (t) = f (El, t), El (t ₀ ) = El ₀ (1), the known predictor-corrector method (PC Method) can be applied to calculate the local error. Therefore, the sequential data intervals may be set so that the local error does not exceed the predetermined upper and lower allowable values.
However, in practice, it is not necessary to continuously change the data interval, and it is possible to change the data interval in two steps or in other appropriate plural steps. Moreover, the numerical solution of the differential equation of the above equation (1) may be of a low order. This is El
This is because the purpose is not to obtain the value of (t), but to obtain a standard for changing the data interval based on the local error.

Example of Invention

 The details of the present invention will be described below with reference to examples.

FIG. 1 is a schematic diagram of an artificial satellite tracking system according to an embodiment of the present invention. In the figure, 3 is an antenna, 4 is an observation center, 5 is a transmission line, 6 is a tracking control device, 7 is a forecast data creation unit, 8 is an allowable error calculation unit, 9 is a local error calculation unit, and 10 is a time step size determination. 11 is a transmission control unit, 13 is an antenna drive device, 14 is an azimuth drive motor, and 15 is an elevation drive motor. Note that the transmission and processing system of the information received by the antenna 3 from the artificial satellite is omitted for simplification because it is not directly related to the description of the present invention.

The observation center 4 uses the tracking control device 6 to create a series of forecast data in which the time is designated at the optimum data interval, that is, the time step width, and the antenna drive device is transmitted via the transmission control unit 11, the transmission line 5, and the transmission control unit 12. Supply to 13. The antenna driving device 13 performs linear interpolation between individual forecast data for the supplied series of forecast data and controls the azimuth drive motor 14 and the elevation drive motor 15 to set the antenna 3 to the target satellite. Track it.

The forecast data creation unit 7 calculates the azimuth angle and the elevation angle of the antenna 3 with respect to the target artificial satellite at any time, and creates the forecast data f.

The allowable error calculation unit 8 calculates the upper limit value ε ₁ and the lower limit value ε _{2 of the} allowable error, which are thresholds for changing the time step width, under the worst and best tracking conditions, that is, the minimum elevation angle and the maximum elevation angle in this embodiment. To do.

The local error calculator 9 calculates a local error Δf that occurs when the forecast data f is created with the given time step width Δt.

The time step size determination unit 10 compares the calculated local error Δf with the allowable errors ε ₁ and ε _2, and when Δf> ε ₁ , Δ
If t ← Δt / 2, and if Δf <ε ₂ , then Δt ← 2
The time step width is changed as Δt. This ensures that the local error is always within tolerance, ie ε ₁ > Δf
Determine the time step width Δt such that> ε ₂ . However, it has a maximum value Δt ₀ and a minimum value Δt _min .

Next, with reference to the flow charts of FIGS. 4 and 5, the process of creating the forecast data having the optimum time step size in the tracking control device 6 of FIG. 1 will be described.

The symbols used are as follows, and their contents are shown in FIG.

t: time.

El (t): tracking curve (elevation angle).

t ₀ : Tracking start time.

t _max : Time when the elevation angle El (t) becomes maximum.

t _n : time of the n-th forecast data.

Δt: Time step width.

Δt ₀ : Initial value of time step width, maximum value.

Δt _min : Allowable minimum value of time step width.

f (t): = El (t) f _n : f (t _n ) = El (t _n ). f ^* _n : = f (tn _-1 ) + (tn _-1 ) * [Delta] t
_{^{... (2) f * max =}} f (t max) + (t max) · Δt min
^{_{... (3) f * 0:}} f (t 0) + (t 0) · Δt 0
_{... (4) Δf: = |} f n -f * n | ... (5) ε 1: Δf max = | f * max -f (t max + Δt min) | ...
(6) ε ₂ : Δf ₀ = | f ^* −f (t ₀ + Δt ₀ ) ...
(7) FIG. 4 is a flow chart of the initial process.

． First, the tracking start time t ₀ , the time t max at which the elevation angle El becomes maximum, the initial value Δt ₀ of the time step width and the allowable minimum value Δt.
Initially input _min to the tracking control device 6.

． The forecast data creation unit 7 uses the elevation angle value f (t _max + Δ) at (t _max + Δt _min ) and (t ₀ + Δt ₀ ).
t _min ), f (t ₀ + Δt ₀ ), respectively.

． The allowable error calculator 8 calculates the linear approximation values at (t _max + Δt _min ) and (t ₀ + Δt ₀ ) using the above (3) and (4).

Obtained using (6) and (7) above, and the upper limit ε of the allowable error
₁ and the lower limit ε ₂ are calculated.

． For the subsequent processing, f _n−1 ← 0, _n−1 ← 0, and Δt ← Δt ₀ are set in the respective units 7, 9, and 10.

Next, the subsequent processing will be described with reference to the flow of FIG.

． The forecast data creation unit 7 creates f _n and _n .

． _{When n-1} = 0, it means that the forecast data does not change, and therefore, is immediately executed. But,
_{When n-1} ≠ 0, the following. To execute.

． ． The local error detection unit 9 obtains the linear approximation value f ^* _n at t _n by using the above equation (2), and further calculates the local error Δf by using the above equation (5).

． The time step size determination unit 10 compares the local error Δf with the upper limit value ε ₁ of the allowable error, executes if Δf> ε ₁ ,
If f and ₁ are executed.

． Since Δf> ε ₁ , the time step width Δt is 2
Shorten to one-half.

． ． Using the Delta] t that Delta] t is shortened as large than the allowable minimum value Delta] t _min, if Δt <Δt _min, Δt
= Hold down to Δt _min . Then run.

． Save f _n , _n for the next calculation.

． In the case of Δfε ₁ , then Δf is further compared with the lower limit value ε ₂ of the tolerance, and if Δfε ₂ , then
If f <ε ₂ , execute.

． And Δf <ε ₂ means that the time step width Δ
Since it means that the local error can be kept within the allowable error even if t is made longer, the amount of information is reduced by changing Δt = 2Δt.

． ． The changed Δt is compared with the initial value (maximum value) Δt _0, and if ΔtΔt ₀ , it may be left unchanged, but Δt>
If Δt ₀ , then Δt = Δt ₀ is suppressed and executed.

． The determined time step width Δt is output.

As described above, the time step width Δt is switched in a plurality of steps within the range of Δt _min Δt Δt ₀ , the minimum required most efficient time step width is determined within the allowable error, and forecast data is created. .

〔The invention's effect〕

As described above, according to the present invention, it is possible to optimize the forecast data amount by enabling the data interval of the forecast data for program tracking in relation to the local error,
The amount of data transmission and the file capacity can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a schematic diagram of an artificial satellite tracking system, FIG. 3 is an explanatory diagram of forecast data and interpolation, and FIGS. 4 and 5 are in this embodiment. FIG. 6 is a flow chart of forecast data creation processing, and FIG. 6 is an explanatory diagram of symbols used in this embodiment. In the figure, 3 is an antenna, 4 is an observation center, 5 is a transmission line,
6 is a tracking control device, 7 is a forecast data creation unit, 8 is an allowable error calculation unit, 9 is a local error calculation unit, 10 is a time step width determination unit, 11 and 12 are transmission control units, 13 is an antenna drive device, 14 Is an azimuth drive motor, and 15 is an elevation drive motor.

Claims (1)

[Claims] 1. The above forecast data is supplied to a control device (13) for controlling a device to be controlled by using the forecast data supplied and the forecast data obtained by interpolating values between the forecast data as control information. forecast a data supply apparatus for, forecast values based on time (t) (f _t) forecast data creation unit supplies to create the (7), the forecast data generator at time (n) from (7) The forecast value (f _n ) supplied and at least the past time (n
An error output unit (9) for outputting a deviation (Δf) from a forecast approximate value (f ^* _n ) at time (n) extrapolated from the forecast value (f _n−1 ) of −1), and the error output unit. Allowable range of deviation (ε) output by (9)
₁ ), (epsilon ₂ ), a deviation (Δf) from the error output (9), and an allowable range value (ε ₁ , ε ₂ ) from the error output (8). ) And a time determination unit (10) that updates the time interval input to the forecast data creation unit (7) according to the determination result, and the control device (13) provides a forecast. A forecast data supply device, characterized in that it is configured to variably and optimally control the step size of the data supply time.