JP2014109517A - Tracking device, tracking method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy of correction of an orbit prediction value as a prediction value of a position of an object to be used for tracking the object.SOLUTION: An acquisition part 12 acquires an orbit prediction value as a prediction value of the position of a satellite from external equipment. An offset time calculation part 11 calculates an offset time indicating a time deviation on an orbit between the position of a satellite at a certain time to be estimated from a received satellite signal and the position of the satellite at the time indicated by the orbit prediction value. A selection part 13 acquires information indicating the degree of an error included in the orbit prediction value, and selects any of a plurality of orbit correction models to be used for the correction of the error included in the orbit prediction value on the basis of the information. A correction part 14 applies the offset time calculated by the offset time calculation part 11 to the orbit correction model selected by the selection part 13, and corrects the orbit prediction value. A driving part 15 drives an antenna on the basis of the orbit prediction value transmitted from the acquisition part 12 and the orbit prediction value corrected by the correction part 14.

Description

  The present invention relates to a tracking device, a tracking method, and a program used for tracking a target.

  Since deep space antennas and radio telescopes are controlled only by the program tracking that tracks the satellite based on the calculated orbit, it is necessary to perform highly accurate orbit calculation. The antenna for the Earth orbiting satellite is controlled to perform initial acquisition and automatic tracking of the satellite based on the position of the satellite calculated from the satellite signal, and program tracking is employed as a backup.

  Orbital calculation accuracy can be improved by mounting a GPS (Global Positioning System) receiver on the satellite, but the orbital calculation accuracy decreases for satellites that orbit at an altitude where atmospheric resistance is likely to change due to solar activity. For example, in a satellite orbiting at an altitude of 500 km, if the orbit calculation error is 1 second in the direction of travel of the satellite, the angle error near the zenith reaches about 0.8 degrees. Therefore, an antenna with a beam width of about 0.2 degrees cannot capture a satellite and receive a satellite signal only by program tracking. During periods of high solar activity, 2-4 seconds of orbital calculation error can occur.

  In the satellite acquisition method disclosed in Patent Document 1, the predicted value obtained based on the satellite orbit calculation is corrected in consideration of the movement of the earth station due to the rotation of the earth in the inertial coordinate system, and the corrected predicted value is used. Capture the satellite. After capturing the satellite, automatic tracking is performed to calculate the position of the satellite based on the satellite signal and control the antenna. Further, in the satellite acquisition method disclosed in Patent Document 1, orbital elements are acquired instead of the predicted values, the predicted values are obtained by calculating the orbital elements, and the epoch time of the orbital elements is used as a parameter for correcting the predicted values. it can.

Japanese Patent Laid-Open No. 2002-14151

  However, in the vicinity of the zenith where the angular velocity in the traveling direction of the satellite as viewed from the earth station is high or in a low orbit, the satellite acquisition method disclosed in Patent Document 1 uses a time shift that represents the difference between the actual satellite position and the predicted value. Since the resolution of the correction amount is degraded, the accuracy of the corrected forecast value is degraded. The satellite acquisition method disclosed in Patent Document 1 is used to shift to automatic tracking based on satellite signals, and the accuracy of the satellite acquisition method is such that satellites are included in the automatic tracking pull-in range. is there.

  In the satellite acquisition method disclosed in Patent Document 1, in order to perform a forecast value calculation for obtaining an azimuth angle, an elevation angle, and a distance from an orbital element, the position of the ground station by the earth rotation in the inertial coordinate system is measured at Greenwich star time or Greenwich. It is necessary to calculate from the average stellar time, and the calculation takes time. If only one set of orbital elements can be acquired, orbital propagation calculation considering the earth's gravity model is required, and further calculation takes time. Therefore, it is not suitable for real-time control.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to improve the accuracy of correction of a predicted trajectory value, which is a predicted value of a target position, used for tracking a target object.

  In order to achieve the above object, a tracking device of the present invention is a tracking device that controls an antenna that receives a signal from a target, and includes an acquisition unit, an offset time calculation unit, a selection unit, a correction unit, and a driving unit. Prepare. The acquisition unit acquires a predicted trajectory value that is a predicted value of the position of the target at each time. The offset time calculation unit calculates an offset time representing a time lag on the orbit between the position of the target at a certain time estimated from the signal received by the antenna and the position of the target at the time indicated by the predicted trajectory value. calculate. The selection unit acquires information indicating the degree of error included in the predicted trajectory value, and selects one of a plurality of trajectory correction models used for correcting the error included in the predicted trajectory value based on the information. . The correction unit corrects the predicted trajectory value by applying the offset time calculated by the offset time calculation unit to the trajectory correction model selected by the selection unit. The drive unit drives the antenna based on the predicted trajectory value corrected by the correction unit.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to improve the precision of correction | amendment of the track | orbit predicted value which is a predicted value of the position of a target used by tracking of a target.

It is a block diagram which shows the structural example of the tracking apparatus which concerns on Embodiment 1 of this invention. 1 is a block diagram illustrating a configuration example of a satellite communication system including a tracking device according to Embodiment 1. FIG. 6 is a diagram illustrating an example of offset time calculation performed by the tracking device according to Embodiment 1. FIG. 4 is a flowchart illustrating an example of a satellite tracking operation performed by the tracking device according to the first embodiment. 3 is a block diagram illustrating a different configuration example of a satellite communication system including a tracking device according to Embodiment 1. FIG. It is a block diagram which shows the structural example of the tracking apparatus which concerns on Embodiment 2 of this invention. 6 is a block diagram illustrating a configuration example of a satellite communication system including a tracking device according to Embodiment 2. FIG. It is a figure which shows the example of calculation of the tracking offset time which the tracking apparatus which concerns on Embodiment 2 performs. It is a figure showing the velocity vector of the satellite in the drive coordinate system of an antenna. 10 is a time chart illustrating an example of calculation of a tracking offset time performed by the tracking device according to the second embodiment. 10 is a flowchart illustrating an example of a satellite tracking operation performed by the tracking device according to the second embodiment. It is a block diagram which shows the structural example of the tracking apparatus which concerns on Embodiment 3 of this invention. 10 is a block diagram illustrating a configuration example of a satellite communication system including a tracking device according to Embodiment 3. FIG. 10 is a flowchart illustrating an example of a satellite tracking operation performed by the tracking device according to the third embodiment. It is a figure which shows an example of the change of the signal level of the detected satellite signal. It is a figure which shows an example of the time change of the variation | change_quantity of offset time and an orbital length radius. It is a figure which shows an example of the error of the direction of an antenna beam. It is a figure which shows an example of the time change of the total value of offset time and tracking offset time, and the variation | change_quantity of a track | orbit length radius. It is a block diagram which shows the physical structural example of the tracking apparatus which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent parts are denoted by the same reference numerals.

(Embodiment 1)
FIG. 1 is a block diagram illustrating a configuration example of a tracking device according to an embodiment of the present invention. The tracking device 1 includes an offset time calculation unit 11, an acquisition unit 12, a selection unit 13, a correction unit 14, and a drive unit 15. The tracking device 1 drives an antenna that receives a signal from a target, and controls the antenna to face the target. Here, as an example, the target is a satellite orbiting the earth. FIG. 2 is a block diagram illustrating a configuration example of a satellite communication system including the tracking device according to the first embodiment. The satellite communication system 2 includes a tracking device 1, an antenna 3, an LNA (Low Noise Amplifier) 4, a DC (Down-Converter) 5, and a receiver 6.

  The antenna 3 receives a signal from the satellite and sends the received satellite signal to the LNA 4. The LNA 4 performs low noise amplification of the satellite signal and sends it to the D-C 5. The D-C 5 converts the low-noise amplified satellite signal from RF (Radio Frequency) to IF (Intermediate Frequency) and sends it to the receiver 6. The receiver 6 demodulates the satellite signal frequency-converted to IF, generates a baseband signal, and outputs the baseband signal to an external device connected to the receiver 6. Further, the receiver 6 detects the signal level of the satellite signal frequency-converted to IF and sends it to the offset time calculation unit 11 provided in the tracking device 1.

  The acquisition unit 12 acquires an orbit prediction value, which is a predicted value of the satellite position at each time, from an external device of the tracking device 1. The predicted trajectory value is composed of time, an azimuth angle, an elevation angle, and a distance in a drive coordinate system with the antenna 3 as the origin, which moves in the inertial coordinate system due to the rotation of the earth. The distance is a distance from the antenna 3 to the satellite. As the inertial coordinate system, for example, three-dimensional coordinates having the origin at the center of gravity of the earth are used. The earth rotates in an inertial coordinate system. Strictly speaking, the inertial coordinates move along the earth's revolution orbit, but can be regarded as inertial coordinates during one period in which a satellite located near the earth orbits the earth. The acquisition unit 12 sends the acquired trajectory prediction value to the offset time calculation unit 11, the correction unit 14, and the drive unit 15.

  The offset time calculation unit 11 calculates an offset time that represents a time lag in orbit between the position of the satellite at a certain time estimated from the satellite signal and the position of the satellite at the time indicated by the orbit prediction value. The offset time is sent to the correction unit 14.

  The selection unit 13 acquires information indicating the degree of error included in the predicted trajectory value, and selects one of a plurality of trajectory correction models used for correcting the error included in the predicted trajectory value based on the information. . The information indicating the degree of error included in the predicted trajectory value is, for example, information about solar activity that affects the orbit of the satellite and the offset time calculated by the offset time calculation unit 11. When the selection unit 13 selects the trajectory correction model based on the offset time, the offset time calculation unit 11 is configured to send the offset time to the selection unit 13. In addition, the user may be configured to select the trajectory correction model, or may be configured to accept input of information indicating the degree of error from the user, and the selection unit 13 may select the trajectory correction model based on the input. Good.

  The selection unit 13 includes, for example, a first trajectory correction model based on the change amount of the trajectory length radius based on the change rate of the atmospheric resistance and the offset time, a second trajectory correction model based on the error of the trajectory length radius and the offset time, and One of the third trajectory correction models based on the offset time is selected. The first trajectory correction model is a model in which the degree of error included in the trajectory prediction value is the largest among the three trajectory correction models, and the third trajectory correction model is the degree of error included in the trajectory prediction value. Is the smallest model.

  The correction unit 14 applies the offset time calculated by the offset time calculation unit 11 to the trajectory correction model selected by the selection unit 13 and corrects the predicted trajectory value. The correction unit 14 sends the corrected predicted trajectory value to the drive unit 15. When the selection unit 13 selects the first trajectory correction model, the correction unit 14 corrects the trajectory length radius and time of the predicted trajectory value based on the change amount of the trajectory length radius and the offset time. When the second trajectory correction model is selected by the selector 13, the trajectory length radius and time of the trajectory prediction value are corrected based on the trajectory radius error and the offset time. When the third trajectory correction model is selected by the selection unit 13, the time of the trajectory prediction value is corrected based on the offset time.

  The drive unit 15 drives the antenna 3 based on the predicted trajectory value sent from the acquisition unit 12 and the predicted trajectory value corrected by the correction unit 14. Each part of the tracking device 1 is not necessarily stored in one housing.

  The operation of each part of the tracking device 1 will be described. The tracking device 1 calculates an offset time in order to acquire a satellite. Based on the position of the satellite indicated by the orbit prediction value at a certain time, the driving unit 15 performs control so that the antenna 3 faces the position of the satellite for a predetermined time including the time. The offset time calculation unit 11 calculates the offset time based on the signal level of the satellite signal received by the antenna 3 within the predetermined time. The predetermined time is arbitrary and may be set so as to include a range in which the offset time can be taken.

  FIG. 3 is a diagram illustrating an example of offset time calculation performed by the tracking device according to the first embodiment. The upper row shows the relationship between the actual satellite orbit and the predicted value. The horizontal axis is time, and the vertical axis is the elevation angle. For ease of understanding, only the elevation angle is described, and the description of the azimuth angle is omitted. The offset time calculation unit 11 calculates an offset time representing a time lag in the orbit between the position of the satellite at time T4 estimated from the satellite signal and the position of the satellite at time T4 indicated by the orbit prediction value. . It is a graph in which the actual satellite orbit is indicated by a thick solid line, and the predicted orbit is a graph indicated by a thin solid line. The antenna 3 faces the position of the satellite indicated by the orbit prediction value for the predetermined time and receives the satellite signal. The elevation angle of the antenna 3 is a graph represented by a dotted line. The drive unit 15 performs control so that the antenna 3 faces the position of the satellite indicated by the orbit prediction value at time T4 for a predetermined time from time T0 to time T5.

  Actually, the elevation angle and the azimuth angle of the antenna 3 on the earth are adjusted in consideration of the earth rotation so that the antenna 3 faces the position of the satellite indicated by the orbit prediction value for a predetermined time. However, for easy understanding, the elevation angle of the antenna 3 is set to a constant value in FIG.

  An example of drive processing for causing the antenna 3 to directly face the position of the satellite at the target time indicated by the orbit prediction value when calculating the offset time ΔTx will be described. Time T4 is set as the target time. The difference between the observation time t and the target time T4 is calculated as the initial offset time. The initial offset time ΔT = t−T4. For example, at the observation time T0, the initial offset time ΔT = T0−T4. The offset time calculation unit 11 sends the initial offset time ΔT to the correction unit 14. The correction unit 14 applies the initial offset time ΔT calculated by the offset time calculation unit 11 to the trajectory correction model selected by the selection unit 13, corrects the time of the predicted trajectory value by t + ΔT, and a predetermined trajectory correction model is obtained. If selected, the radius of the trajectory length is also corrected. The correction unit 14 sends the corrected predicted trajectory value to the drive unit 15. Details of the operation of the correction unit 14 that corrects the predicted trajectory value will be described later.

  The drive unit 15 drives the antenna 3 based on the predicted trajectory value corrected at time t + ΔT. By repeating the above-described processing and using the predicted trajectory value corrected based on the initial offset time ΔT that changes from moment to moment, the antenna is positioned at the satellite position indicated by the predicted trajectory value at the target time T4 for a predetermined time including the target time. 3 can be controlled to face each other. Thereafter, the offset time calculation unit 11 determines the position of the satellite at time T4 estimated from the satellite signal based on the signal level of the satellite signal at a predetermined time including the target time, and the position of the satellite at time T4 indicated by the orbit prediction value. An offset time representing a time shift on the orbit is calculated.

  The lower part of FIG. 3 shows the signal level of the satellite signal. The horizontal axis is time, and the vertical axis is signal level. Time T4 is set to 0, and the difference from time T4 is represented on the horizontal axis. For example, the offset time calculation unit 11 performs the time T3 when the signal level of the satellite signal falls below the second threshold for the first time from the time T1 when the signal level of the satellite signal first exceeded the first threshold within the predetermined time. Based on the signal level of the satellite signal, a quadratic curve that is most applicable is calculated using the least square method, and ΔTx that is the difference between time T2 and time T4 at which the quadratic curve takes the maximum value is calculated as the offset time. Calculate as

  When x is the difference from time T4 and y is the signal level, the quadratic curve is expressed by the following equation (1). The value of x is negative when the time is earlier than the time T4 and positive when the time is later than the time T4. When the coefficient of the following equation (1) is used, the offset time ΔTx that is the difference between the time T2 and the time T4 corresponding to the maximum value of the quadratic curve is expressed by the following equation (2). As shown in FIG. 3, when the satellite passes the position where the antenna 3 is facing directly earlier than the time indicated by the predicted trajectory value, the offset time ΔTx becomes negative and later than the time, When the satellite passes, the offset time ΔTx becomes positive.

  Next, the tracking device 1 corrects the predicted trajectory value based on the trajectory correction model selected by the selection unit 13 and the offset time calculated by the offset time calculation unit 11. The correction unit 14 calculates six elements of the trajectory based on two consecutive data of the time immediately before and the time immediately after the correction target time among the data constituting the predicted trajectory value. The time to be corrected is t, the times of two consecutive data immediately before and after time t are t1 and t2, respectively, and t1 <t <t2. The predicted trajectory value at time t1 includes an azimuth angle AZ1, an elevation angle EL1, and a distance R1, and the predicted trajectory value at time t2 includes an azimuth angle AZ2, an elevation angle EL2, and a distance R2.

  Based on the two data, the correction unit 14 calculates the six orbital elements (x1, y1, z1, Vx1, Vy1, Vz1) at the time t1 of the elliptical orbit that passes through the two points specified by the two data. . x1, y1, and z1 indicate the components of the satellite position in the inertial coordinate system, and Vx1, Vy1, and Vz1 indicate the components of the satellite velocity at time t1. The above calculation is based on the method described in Reference: Pedro Ramon Escobal, “METHOD OF ORBIT DETERMINATION”, published in 1976.

  The coordinate transformation of the six trajectory elements is performed, and the Kepler trajectory elements (a, e, i, Ω, ω, M) at the time t1 are calculated. a is the orbital radius, e is the orbit eccentricity, i is the orbit inclination angle, Ω is the ascending intersection red longitude, ω is the near point argument, and M is the average near point angle. The average motion n, which is the average angular velocity, is expressed by the following equation (3) according to Kepler's third law, where μ is a value obtained by multiplying the universal gravitational constant by the mass of the earth.

  The satellite velocity V at time t1 is expressed by the following equation (4) by combining the components.

  The correction of the predicted trajectory value using the first trajectory correction model will be described. Differentiating the average motion n in the above equation (3), the following equation (5) is derived.

The elapsed time from the epoch time t0 when the calculation of the predicted trajectory is started is defined as time t. The average near point angle M, which is an angle parameter that rotates uniformly with time t, is expressed by the following equation (6) using the average motion n, time t, and the initial value M ₀ of the average near point angle. The following formula (7) is obtained by differentiating the following formula (6).

  If the error in the direction of travel of the satellite is ΔL, ΔL is expressed by the following equation (8) based on Δn and ΔM. However, the error ΔL in the traveling direction of the satellite becomes positive when the satellite passes a certain point at a time earlier than the time indicated by the orbit prediction value, and becomes negative when the satellite passes at a time later than the time.

The semi-major axis of the change rate due to air resistance and .DELTA.a _DR, when the elapsed time from time t0 to time to be corrected to te, the error [Delta] L ₁ in the traveling direction of the satellite due to the amount of change in semimajor axis by atmospheric resistance, It is represented by the following formula (9). Further, the error ΔL _{1 in} the traveling direction of the satellite is expressed by the following equation (10) using the satellite velocity V and the offset time ΔTx.

From the above formulas (9) and (10), the following formula (11) is derived. The change amount Δa _DRT of the orbital length radius is expressed by the following equation (12), and the corrected orbital length radius a ₁ is expressed by the following equation (13).

When the selection unit 13 selects the first trajectory correction model, the correction unit 14 corrects the trajectory length radius and time of the trajectory prediction value. The correction unit 14 replaces the time t1 of the predicted trajectory value with t1 + ΔTx, and replaces the trajectory length radius a with a + Δa _DRT .

The correction of the predicted trajectory value using the second trajectory correction model will be described. When the error of the semi-major axis and .DELTA.a _D, similarly to the first track correction model, (8) the error [Delta] L ₂ in the traveling direction of the satellite by semimajor axis of the error from the equation, the table below (14) Is done. The error [Delta] L ₂ in the traveling direction of the satellite using the satellite velocity V and offset time ΔTx above is expressed by the following equation (15).

From the above formulas (14) and (15), the following formula (16) is derived. Semimajor axis _{a 2} after correction is expressed by the following equation (17).

When the second trajectory correction model is selected by the selection unit 13, the correction unit 14 corrects the trajectory length radius and time of the trajectory prediction value. Correcting unit 14, the time t1 trajectory predicted value replaced by t1 + Delta] Tx, replacing the semi-major axis a at a + .DELTA.a _D.

The correction of the predicted trajectory value using the third trajectory correction model will be described. The error ΔL _{3 in} the traveling direction of the satellite is expressed by the following equation (18) using the satellite velocity V and the offset time ΔTx.

  When the third trajectory correction model is selected by the selection unit 13, the correction unit 14 corrects the time of the trajectory prediction value. The correction unit 14 replaces the time t1 of the predicted trajectory value with t1 + ΔTx.

  Based on the trajectory correction model selected by the selection unit 13, the correction unit 14 performs elliptical trajectory propagation calculation using the predicted trajectory value corrected as described above. The correction unit 14 calculates the Kepler equation at the time t1 + ΔTx, and calculates the azimuth angle, the elevation angle, and the distance. The correction unit 14 sends the corrected time and the calculated azimuth angle, elevation angle, and distance to the drive unit 15. In the correction of the predicted trajectory value for driving the antenna 3 when calculating the offset time ΔTx, the correction unit 14 corrects the predicted trajectory value by replacing the offset time ΔTx in the above process with the initial offset time ΔT.

  The correction unit 14 repeats the above-described processing for the subsequent correction target time, and sequentially sends the time, the azimuth angle, the elevation angle, and the distance to the drive unit 15. The time interval of the orbit prediction value data is set to 1 second, for example, and the above-described calculation and correction of the orbit prediction value are repeatedly performed in real time by an embedded computer. Since two consecutive data of the time immediately before and the time immediately after the correction target time are used, an error in the propagation calculation can be reduced. Further, when the trajectory correction model different from the trajectory correction model used for the correction is selected by the selection unit 13 while the above-described processing is repeatedly performed, the correction unit 14 determines the subsequent correction target time. Correction based on a new trajectory correction model may be performed.

  The drive unit 15 drives the antenna 3 based on the predicted trajectory value corrected by the correction unit 14. The drive unit 15 drives the antenna 3 based on the time, the azimuth angle, the elevation angle, and the distance sent from the correction unit 14.

  FIG. 4 is a flowchart illustrating an example of the satellite tracking operation performed by the tracking device according to the first embodiment. The tracking device 1 performs an orbit prediction value correction and a driving operation in order to track the satellite. The acquisition unit 12 acquires an orbit prediction value, which is a predicted value of the satellite position at each time, from an external device of the tracking device 1 (step S110). The selection unit 13 acquires information indicating the degree of error included in the predicted trajectory value, and selects one of a plurality of trajectory correction models used for correcting the error included in the predicted trajectory value based on the information. (Step S120).

  The offset time calculation unit 11 calculates an offset time representing a time lag in the orbit between the position of the satellite at a certain time estimated from the satellite signal and the position of the satellite at the time indicated by the predicted orbit (step). S130). The correction unit 14 applies the offset time calculated by the offset time calculation unit 11 to the trajectory correction model selected by the selection unit 13 and corrects the predicted trajectory value for each correction target time. The time corrected, and the azimuth, elevation, and distance are sequentially sent (step S140). When the correction process in step S140 is completed, the process ends.

  The drive unit 15 drives the antenna based on the time, azimuth angle, elevation angle, and distance sent from the correction unit 14 (step S210). The drive unit 15 repeats the process of step S210 at a predetermined timing.

  FIG. 5 is a block diagram illustrating a different configuration example of the satellite communication system including the tracking device according to the first embodiment. The satellite communication system 2 shown in FIG. 5 includes a level detector 7 in addition to the configuration of the satellite communication system 2 shown in FIG. The D-C 5 also sends a satellite signal whose frequency has been converted to IF to the level detector 7. Unlike the satellite communication system 2 shown in FIG. 2, the level detector 7 detects the signal level of the satellite signal frequency-converted to IF, and sends the satellite signal signal level to the offset time calculation unit 11 provided in the tracking device 1. send. When it takes time to capture the satellite signal at the receiver 6, the processing speed can be increased by providing the level detector 7 that only detects the signal level.

  As described above, the tracking device 1 according to the first embodiment is used for tracking a target object by correcting the predicted trajectory value by applying an offset time to any of a plurality of trajectory correction models. Thus, it is possible to improve the accuracy of correcting the predicted trajectory value, which is the predicted value of the target position.

  Further, as in the prior art, the antenna 3 includes, for example, two power supply units, and the amplitude ratio of the sum signal that is the sum of the satellite signals received by each power supply unit and the difference signal that is the difference between the satellite signals received by each power supply unit When performing automatic tracking that is controlled based on the deviation of the antenna 3 in the drive coordinate system calculated based on the phase difference, it is necessary to provide LNA 4 and D-C 5 for each of the sum signal and the difference signal. The tracking device 1 according to the first embodiment has a simple configuration compared to a device that performs automatic tracking, and can reduce the manufacturing cost of the device. It is also possible to simplify the configuration of the power feeding unit of the antenna 3.

(Embodiment 2)
FIG. 6 is a block diagram showing a configuration example of the tracking device according to Embodiment 2 of the present invention. The tracking device 1 according to the second embodiment includes a tracking unit 16 in addition to the configuration of the tracking device 1 according to the first embodiment. FIG. 7 is a block diagram illustrating a configuration example of a satellite communication system including the tracking device according to the second embodiment. The tracking unit 16 receives the predicted orbit value from the acquisition unit 12, receives the corrected predicted orbit value from the correction unit 14, and receives the signal level of the satellite signal from the receiver 6. The tracking unit 16 corrects the predicted trajectory value by calculating a tracking offset time used to reduce an error included in a position where the antenna 3 is directly facing at a certain time based on the signal level of the satellite signal.

  The operation of each part of the tracking device 1 different from the first embodiment will be described. The drive unit 15 drives the antenna 3 based on the predicted trajectory value corrected by the correction unit 14 as described in the first embodiment. For example, the drive unit 15 sets the position of the satellite at the reference time based on a certain time (hereinafter referred to as a reference time) sent from the correction unit 14 and the position of the satellite indicated by the azimuth angle, the elevation angle, and the distance at the reference time. Control is performed so that the antenna 3 faces directly. Thereafter, the driving unit 15 causes the antenna 3 to face the satellite position at a time advanced by the first tracking time from the reference time and the satellite position at a time delayed by the second tracking time from the reference time. To control. The first tracking time and the second tracking time may be the same time or different times.

  The tracking unit 16 is a satellite signal when the antenna 3 is facing the satellite position at the reference time, the time advanced by the first tracking time from the reference time, and the time delayed by the second tracking time from the reference time. The tracking offset time is calculated based on the signal level. Then, the predicted trajectory value is corrected based on the tracking offset time, and the corrected predicted trajectory value is sent to the drive unit 15.

  FIG. 8 is a diagram illustrating an example of the tracking offset time calculation performed by the tracking device according to the second embodiment. The signal level of the satellite signal when facing the satellite position at the reference time is p2, and the signal level of the satellite signal when facing the satellite position at the time advanced by the first tracking time from the reference time. Let p1 be the signal level of the satellite signal when facing the position of the satellite at the time delayed by the second tracking time from the reference time. The angle formed by the position vector of the satellite at the reference time and the position vector of the satellite at the time advanced by the first tracking time from the reference time with respect to the origin of the driving coordinate system of the antenna 3 is Δθ1. The angle between the satellite position vector at the reference time and the satellite position vector at the time delayed by the second tracking time from the reference time with respect to the origin of the driving coordinate system of the antenna 3 is Δθ2. The traveling direction of the satellite is the positive direction of the angle.

The antenna radiation pattern is approximated by a Gaussian distribution as shown by a one-dot chain line in FIG. 8, and based on the signal levels p1, p2, and p3 of the satellite signal, the position of the satellite at the reference time and the position where the signal level of the satellite signal becomes a peak. The angle difference Δδ is calculated. The formula of the Gaussian distribution is expressed by the following formula (19). Σ ² in the following formula (19) represents dispersion. The following equation (19) is linearized logarithmically, and (Δθ1, p1), (0, p2), (Δθ2, p3) are substituted for (α, p), respectively, to solve a ternary simultaneous linear equation, ) Is calculated based on the equation.

  As expressed by the following equation (21), the angle difference Δδ is divided by the angular velocity Vtr in the traveling direction of the satellite to calculate the tracking offset time ΔΔTx.

  FIG. 9 is a diagram illustrating the velocity vector of the satellite in the antenna drive coordinate system. A black circle in FIG. 9 is the satellite communication system 2 including the antenna 3 located on the earth, and a white circle is a satellite. The inner product of the satellite position vector rrr relative to the origin of the driving coordinate system of the antenna 3 and the velocity vector vvv in the driving coordinate system of the antenna 3 is calculated, and the angle β is calculated. The tracking unit 16 performs elliptical orbit propagation calculation using the predicted trajectory value corrected by the correction unit 14, calculates the velocity component at the time at which the velocity vector vvv is to be calculated, subtracts the rotation speed of the earth from the calculation result, A velocity vector vvv is calculated. The tracking unit 16 divides | vvv | cos (90 ° −β), which is a component of the vector vvv orthogonal to the vector rrr, by the vector rrr, so that the angular velocity Vtr in the satellite traveling direction in the orbital coordinate system of the antenna 3 is obtained. Is calculated.

  It is possible to improve the accuracy of the satellite tracking by improving the accuracy of the correction of the orbit prediction value by correcting the orbit prediction value by the correction unit 14 and correcting the orbit prediction value based on the tracking offset time by the tracking unit 16. It becomes.

  Only when the signal level p2 detected by the tracking unit 16 is lower than the threshold, the driving unit 15 is delayed by the second tracking time from the satellite position at the time advanced by the first tracking time from the reference time and the reference time. You may comprise so that it may control so that an antenna may face each position of the satellite in time. By driving the antenna 3 only when the signal level p2 is lower than the threshold, it is possible to reduce the frequency of driving the antenna 3 and improve maintainability.

  FIG. 10 is a time chart illustrating an example of tracking offset time calculation performed by the tracking device according to the second embodiment. Before calculating the tracking offset time, the absolute values of the first tracking time and the second tracking time are divided by, for example, the beam width of the antenna 3 by a real value of 10 or more and 20 or less to drive the antenna 3. The value divided by the angular velocity of the satellite in the direction of travel in the coordinate system. The angular velocity in the traveling direction of the satellite is calculated at a time immediately before the start of calculation of the tracking offset time, and at a time according to a calculation cycle determined by the calculation capability of the embedded computer.

  The calculation of the tracking offset time will be described. The tracking unit 16 starts calculating the tracking offset time at time τ0. Let the offset time calculated by the offset time calculation unit 11 be ΔTx. Based on the position of the satellite indicated by a certain reference time, azimuth, elevation, and distance sent from the correction unit 14, the drive unit 15 controls the antenna 3 to face the position of the satellite at the reference time. If the time of the predicted trajectory value before correction is t, the time sent from the correction unit 14 is t + ΔTx. Time τ1 coincides with t + ΔTx. The driving unit 15 performs control so that the antenna 3 directly faces the position of the satellite at the time t + ΔTx of the corrected orbit prediction value during the time s1 + s2 from the time τ0 to the time τ2.

  The tracking unit 16 integrates the signal level of the satellite signal during a time s2 from time τ1 to time τ2. Assume that the integration result is P2_1. The integration step time is T, for example, 20 ms or less. If the signal level is in decibels, the logarithm is converted to a true number and integration is performed. The same applies to the following integration processing. Further, the tracking unit 16 integrates the angular velocity in the traveling direction of the satellite in the driving coordinate system of the antenna 3 from time τ0 to time τ2. The integration result is Vtr1.

  The tracking unit 16 performs elliptical orbit propagation calculation using the corrected predicted trajectory value, calculates the position of the satellite at the time advanced by the first tracking time from the time t + ΔTx, and calculates the time, azimuth angle, elevation angle, and The distance is sent to the drive unit 15. The driving unit 15 controls the antenna 3 to face the satellite position determined by the azimuth angle, the elevation angle, and the distance during a time s1 from time τ2 to time τ3.

  The tracking unit 16 integrates the signal level of the satellite signal during a time s2 from time τ3 to time τ4. The integration result is P1. Further, the tracking unit 16 integrates a value obtained by multiplying the angular velocity in the traveling direction of the satellite in the driving coordinate system of the antenna 3 by the first tracking time during the time s1 + s2 from the time τ2 to the time τ4 to obtain the offset angle offset1. calculate.

  The tracking unit 16 performs elliptical orbit propagation calculation using the corrected orbit prediction value, calculates the position of the satellite at a time delayed by a second tracking time from the time t + ΔTx, and calculates the time, azimuth, elevation, and The distance is sent to the drive unit 15. The driving unit 15 controls the antenna 3 to face the satellite position determined by the azimuth angle, the elevation angle, and the distance during a time s1 from time τ4 to time τ5.

  The tracking unit 16 integrates the signal level of the satellite signal during a time s2 from time τ5 to time τ6. The integration result is P3. The tracking unit 16 also integrates a value obtained by multiplying the angular velocity in the traveling direction of the satellite in the driving coordinate system of the antenna 3 by the second tracking time during the time s1 + s2 from the time τ4 to the time τ6, and sets the offset angle offset2. calculate.

  The driving unit 15 performs control so that the antenna 3 directly faces the position of the satellite at the time t + ΔTx of the corrected orbit prediction value during the time s1 from the time τ6 to the time τ7. The tracking unit 16 integrates the signal level of the satellite signal during a time s2 from time τ7 to time τ8. Assume that the integration result is P2_2. Further, the tracking unit 16 integrates the angular velocity in the traveling direction of the satellite in the driving coordinate system of the antenna 3 during the time s1 + s2 from the time τ6 to the time τ8. Assume that the integration result is Vtr2.

  The amount of change due to satellite movement during the above processing is corrected by linear approximation. The correction amount Δlv is expressed by the following equation (22). When the correction amount Δlv is used, the signal levels p1, p2, and p3 are calculated as represented by the following equation (23).

  Δθ1 and Δθ2 used in the above equation (20) are expressed by the following equation (24).

  The average avg_Vtr of the angular velocity in the traveling direction of the satellite during the above processing is expressed by the following equation (25).

  Δδ is calculated by applying the above equation (23) and the above equation (24) to the above equation (20). The tracking offset time ΔΔTx is calculated by applying avg_Vtr in the above equation (25) as Vtr in the above equation (21). When the satellite passes through the position where the antenna 3 is directly facing the corrected orbit predicted value, the tracking offset time ΔΔTx becomes negative, and the satellite passes through the position later than that time. In this case, the tracking offset time ΔΔTx is positive.

  The tracking unit 16 corrects the time of the predicted trajectory value by t + ΔTx + ΔΔTx, performs the elliptical trajectory propagation calculation using the corrected predicted trajectory value, and calculates the azimuth angle, the elevation angle, and the distance. The tracking unit 16 sends the corrected time and the calculated azimuth angle, elevation angle, and distance to the drive unit 15. The drive unit 15 drives the antenna 3 based on the time, the azimuth angle, the elevation angle, and the distance. The driving unit 15 and the tracking unit 16 repeat the above-described process, and after capturing the satellite described in the first embodiment, correct the orbit prediction value and track the satellite as described in the second embodiment. The accuracy can be improved.

  The drive unit 15 may be configured to control the antenna 3 in a range where the elevation angle satisfies a predetermined condition, and the drive unit 15 and the tracking unit 16 may perform the above-described processing at regular time intervals. For example, the drive unit 15 controls the antenna 3 so that the elevation angle becomes a value within a predetermined range. In addition, the processing may be performed substantially continuously by shortening the time interval sufficiently. Moreover, you may comprise so that the said time interval can be set from the exterior of the tracking apparatus 1. FIG.

  FIG. 11 is a flowchart illustrating an example of a satellite tracking operation performed by the tracking device according to the second embodiment. The tracking device 1 performs an orbit prediction value correction and a driving operation in order to track the satellite. The operation of correcting the predicted trajectory is the same as that of the tracking device according to the first embodiment. The tracking unit 16 is a satellite signal when the antenna 3 is facing the satellite position at the time, the time advanced by the first tracking time from the time, and the time delayed by the second tracking time from the time. The tracking offset time is calculated based on the signal level, and the predicted trajectory value is corrected based on the tracking offset time (step S201). The drive unit 15 drives the antenna 3 based on the predicted trajectory value corrected by the tracking unit 16 (step S210). The drive unit 15 and the tracking unit 16 repeat the processes in steps S201 and S210 at a predetermined timing.

  As described above, according to the tracking device 1 according to the second embodiment, by calculating the tracking offset time and correcting the predicted trajectory value, the predicted value of the target position used for tracking the target object. It is possible to improve the accuracy of correcting the predicted trajectory.

(Embodiment 3)
FIG. 12 is a block diagram showing a configuration example of the tracking device according to Embodiment 3 of the present invention. The tracking device 1 according to Embodiment 3 serves as a backup for automatic tracking that performs antenna control based on satellite signals. FIG. 13 is a block diagram illustrating a configuration example of a satellite communication system including the tracking device according to the third embodiment. The antenna 3 includes, for example, two power feeding units. The separation unit 8 generates a sum signal S that is the sum of the satellite signals received by each power feeding unit and a difference signal D that is the difference between the satellite signals received by each power feeding unit, and the sum signal S is sent to the LNA 41 as a difference signal. Send D to LNA42.

  The LNAs 41 and 42 amplify the sum signal S and the difference signal D with low noise, respectively, and send them to the D-Cs 51 and 52. The D-C 51 sends the frequency-converted sum signal S to the receiver 6 and the tracking receiver 9. The D-C 52 sends the frequency-converted difference signal D to the tracking receiver 9. The tracking receiver 9 calculates the magnitude and direction of the deviation of the antenna 3 in the driving coordinate system of the antenna 3 based on the amplitude ratio and the phase difference between the sum signal S and the difference signal D, and sends them to the driving unit 15. The tracking receiver 9 performs an operation as a signal tracking unit. The drive unit 15 controls the antenna 3 based on the magnitude and direction of the deviation calculated by the tracking receiver 9 and performs an operation as a main drive unit.

  The offset time calculation unit 11 is based on the position vector of the position where the antenna 3 is directly facing at a certain time and the position vector of the satellite indicated by the predicted trajectory value at that time with reference to the origin of the driving coordinate system of the antenna 3. Calculate the angle. An offset time that minimizes the angle is calculated, and the offset time is sent to the correction unit 14.

  The processes of the acquisition unit 12, the selection unit 13, and the correction unit 14 are the same as those in the first embodiment. The drive unit 15 performs an operation as a switching unit that switches between antenna control based on the deviation calculated by the tracking receiver 9 and antenna control based on the predicted trajectory value corrected by the correction unit 14 under a predetermined condition. For example, when the signal from the tracking receiver 9 is interrupted for a certain time, the driving unit 15 performs antenna control based on the predicted trajectory value corrected by the correction unit 14.

  FIG. 14 is a flowchart illustrating an example of a satellite tracking operation performed by the tracking device according to the third embodiment. The tracking device 1 performs an orbit prediction value correction and a driving operation in order to track the satellite. The operation of correcting the predicted trajectory is the same as that of the tracking device 1 according to the first and second embodiments. However, in step S130, as described above, the offset time calculation unit 11 uses the origin of the driving coordinate system of the antenna 3 as a reference and the position vector of the position where the antenna 3 is facing at a certain time and the trajectory at the time. An offset time is calculated such that the angle formed by the satellite position vector indicated by the predicted value is minimized.

  The drive unit 15 determines whether to perform automatic tracking or to perform antenna driving based on the predicted trajectory value (step S310). When automatic tracking is performed (step S310: Y), the tracking receiver 9 calculates. Based on the magnitude and direction of displacement of the antenna 3 in the drive coordinate system, the antenna 3 is driven by automatic tracking (step S320). When automatic tracking is not performed (step S310: N), the antenna 3 is driven based on the predicted trajectory value corrected by the correction unit 15 (step S210). The drive unit 15 repeats the above process at a predetermined timing.

  The tracking device 1 according to the third embodiment may further include the tracking unit 16 included in the second embodiment, and may be configured to correct the predicted trajectory value based on the tracking offset time. The method of automatic tracking is not limited to the method using the sum signal S and the difference signal D described above.

  As described above, even when performing antenna driving by automatic tracking, it is possible to improve the accuracy of satellite tracking by providing the tracking device 1 according to the third embodiment.

(Concrete example)
Satellite tracking simulation was performed using the tracking device 1 according to the first and second embodiments. The time error of the predicted orbit was about -18 seconds, the error of the orbital length radius was -1800 m, the satellite altitude was about 500 km, and the maximum elevation angle of the satellite path was 88.3 degrees. The beam width of the antenna 3 was 0.2 degrees, and the time interval of each data of the predicted trajectory value was 1 millisecond.

  In the detection of the signal level of the satellite signal performed by the offset time calculation unit 11, the detection interval is 1 millisecond, the Gaussian noise is 0.18 dBm (root mean square), the first threshold is −80 dBm, The second threshold is set to a value that is 3 dBm lower than the maximum signal level, and the satellite signal is set to an elevation angle of 0 degrees for 30 seconds before and after 91402 seconds from the epoch time when the calculation of the orbit prediction value is started. The level was detected. dBrms means that the above value is an effective value. In the following description, rms attached after a unit indicating a physical quantity means that the physical quantity is an effective value.

  FIG. 15 is a diagram illustrating an example of a change in the signal level of the detected satellite signal. FIG. 15A shows the signal level of the detected satellite signal, and FIG. 15B shows the best-fit quadratic curve calculated using the least square method. The horizontal axis is the difference time (unit: second) from the time when 91402 seconds have passed since the epoch time, and the vertical axis is the signal level (unit: dBm). In the quadratic curve shown in FIG. 15B, b1 = −41.6913 in the above equation (1) and b2 = −1.1437, so that the offset time ΔTx = −18.2258 seconds. Therefore, it can be seen that the offset time can be calculated with a certain accuracy by the processing of the offset time calculation unit 11.

  FIG. 16 is a diagram illustrating an example of a time change of the change amount of the offset time and the orbital length radius. The horizontal axis represents an elapsed time (unit: second) from the start of the signal level detection of the satellite signal in the offset time calculation unit 11. The first vertical axis is the difference time (unit: second), and the second vertical axis is the change amount (unit: m) of the orbital length radius. It is a graph which shows the above-mentioned difference time with a solid line, and the change amount of an orbital length radius is a graph which shows with a dotted line.

  Next, a simulation was performed for calculating the tracking offset time. The absolute value of the first tracking time and the second tracking time is set to a value obtained by dividing the beam width of the antenna 3 by 20 and dividing by the angular velocity in the traveling direction of the satellite in the driving coordinate system of the antenna 3, The tracking offset time was calculated continuously for 1 second.

  FIG. 17 is a diagram illustrating an example of an error in the direction of the antenna beam. The horizontal axis represents the time (unit: second) since the start of calculation of the tracking offset time, and the vertical axis represents the angle error (unit: degree) in the beam direction. The decrease in the signal level of the satellite signal was 0.176 dBrms, and the decrease in the signal level in a state including noise was 0.997 dB at the maximum. The angle error in the beam direction was 0.007927 degrees rms, and the angle error in the beam direction was 0.0205 degrees at the maximum.

  FIG. 18 is a diagram illustrating an example of a time change of the total value of the offset time and the tracking offset time and the change amount of the trajectory length radius. The horizontal axis is the time (unit: second) after the calculation of the tracking offset time is started, the first vertical axis is the total value (unit: second) of the offset time and the tracking offset time, and the second The vertical axis represents the amount of change in the orbital radius (unit: m). The total value of the offset time and the tracking offset time is a graph indicated by a solid line, and the change amount of the orbital length radius is indicated by a dotted line.

  As described above, the signal level decreases due to an error in the predicted orbit after capturing the satellite. By controlling the antenna 3 based on the tracking offset time that changes from time to time, the accuracy of satellite tracking can be improved.

  FIG. 19 is a block diagram illustrating a physical configuration example of the tracking device according to the embodiment of the present invention. The tracking device 1 includes a control unit 31, a main storage unit 32, an external storage unit 33, and an input / output unit 34. The main storage unit 32, the external storage unit 33, and the input / output unit 34 are all connected to the control unit 31 via the internal bus 30.

  The control unit 31 includes a CPU (Central Processing Unit) and the like, and executes processing for tracking the target performed by the tracking device 1 in accordance with a control program 35 stored in the external storage unit 33. The main storage unit 32 is composed of a RAM (Random-Access Memory) or the like, loads a control program 35 stored in the external storage unit 33, and is used as a work area of the control unit 31.

  The external storage unit 33 includes a non-volatile memory such as a flash memory, a hard disk, a DVD-RAM (Digital Versatile Disc Random-Access Memory), a DVD-RW (Digital Versatile Disc ReWritable), and the above processing is performed by the control unit 31. A control program 35 to be executed is stored in advance, and data stored in the control program 35 is supplied to the control unit 31 according to an instruction from the control unit 31, and the data supplied from the control unit 31 is stored.

  The input / output unit 34 includes a serial interface or a parallel interface. An external device is connected to the input / output unit 34. For example, the acquisition unit 12 included in the tracking device 1 acquires a predicted trajectory value from the external device. Further, for example, the selection unit 13 may be configured to receive an input from an input device or the like connected via the input / output unit 34 and select the trajectory correction model.

  1, 6, and 12, the control program 35 uses the control unit 31, the main storage unit 32, the external storage unit 33, and the input / output unit 34 as resources. Execute by processing.

  In addition, the hardware configuration and the flowchart described above are merely examples, and can be arbitrarily changed and modified.

  The central part that performs control processing including the control unit 31, the main storage unit 32, the external storage unit 33, the internal bus 30 and the like can be realized by using a normal computer system, not a dedicated system. . For example, a computer program for executing the above operation is stored and distributed in a computer-readable recording medium (flexible disk, CD-ROM, DVD-ROM, etc.), and the computer program is installed in the computer. Thus, the tracking device 1 that executes the above-described processing may be configured. Further, the tracking device 1 may be configured by storing the computer program in a storage device included in a server device on a communication network such as the Internet and downloading it by a normal computer system.

  Further, when the functions of the tracking device 1 are realized by sharing an OS (operating system) and an application program, or by cooperation between the OS and the application program, only the application program portion is stored in a recording medium or a storage device. May be.

  It is also possible to superimpose a computer program on a carrier wave and distribute it via a communication network. For example, the computer program may be posted on a bulletin board (BBS: Bulletin Board System) on a communication network, and the computer program may be distributed via the network. The computer program may be started and executed in the same manner as other application programs under the control of the OS, so that the above-described processing may be executed.

  1 tracking device, 2 satellite tracking system, 3 antenna, 4, 41, 42 LNA, 5, 51, 52 DC, 6 receiver, 7 level detector, 8 separation unit, 9 tracking receiver, 11 offset time calculation Unit, 12 acquisition unit, 13 selection unit, 14 correction unit, 15 drive unit, 16 tracking unit, 30 internal bus, 31 control unit, 32 main storage unit, 33 external storage unit, 34 input / output unit, 35 control program, D Difference signal, S sum signal.

Claims (12)

A tracking device that controls an antenna that receives a signal from a target,
An acquisition unit that acquires a predicted trajectory value that is a predicted value of the position of the target at each time;
Calculate an offset time that represents a time lag in the orbit between the position of the target at a certain time estimated from the signal received by the antenna and the position of the target at the time indicated by the predicted trajectory value An offset time calculation unit
A selection unit that obtains information indicating a degree of error included in the predicted trajectory value, and selects one of a plurality of trajectory correction models used for correcting the error included in the predicted trajectory value based on the information; ,
Applying the offset time calculated by the offset time calculation unit to the trajectory correction model selected by the selection unit, and correcting the trajectory prediction value;
A drive unit that drives the antenna based on the predicted trajectory value corrected by the correction unit;
A tracking device comprising: The selection unit includes a first trajectory correction model based on an amount of change in the trajectory length radius determined by a rate of change in atmospheric resistance and the offset time, a second trajectory correction model based on an error in the trajectory length radius and the offset time. , And a third trajectory correction model based on the offset time,
The correction unit, when the selection unit selects the first trajectory correction model, the trajectory length radius of the trajectory prediction value based on the amount of change in the trajectory length radius of the trajectory prediction value and the offset time. When the time is corrected and the second trajectory correction model is selected by the selection unit, the trajectory length radius and the time of the predicted trajectory value are corrected based on the error of the trajectory length radius and the offset time, When the third trajectory correction model is selected by the selection unit, the time of the trajectory prediction value is corrected.
The tracking device according to claim 1.   The correction unit determines whether the first trajectory correction model is selected by the selection unit based on two consecutive data of a time immediately before and after a correction target time among data constituting the predicted trajectory value. If selected, the change amount of the orbital length radius at the correction target time is calculated, and the orbital length radius and time of the predicted orbit are corrected based on the change amount of the orbital length radius and the offset time. When the second trajectory correction model is selected by the selection unit, an error of the trajectory length radius at the correction target time is calculated, and the trajectory is calculated based on the trajectory length radius error and the offset time. The trajectory length radius and time of the predicted value are corrected, and when the third trajectory correction model is selected by the selection unit, the time of the predicted trajectory value is corrected based on the offset time. Tracking apparatus according to claim 2 carried out repeatedly while changing the two data in response to Rukoto to a change in time of the correction target. The offset time calculation unit calculates a difference between an observation time and a target time as an initial offset time, and the selection unit, the correction unit, and the drive unit use the initial offset time instead of the offset time. Is repeated within a predetermined time including the target time,
The offset time calculation unit calculates the offset time based on the signal level of the signal within the predetermined time,
The selection unit, the correction unit, and the drive unit perform processing using the offset time.
The tracking device according to any one of claims 1 to 3.   The offset time calculation unit, from the time when the signal level of the signal exceeds the first threshold value for the first time within the predetermined time, to the time when the signal level of the signal first falls below the second threshold value, 5. A quadratic curve corresponding to the signal level of the signal is calculated based on a signal level of the signal using a least square method, and the offset time is calculated based on a time corresponding to a maximum value of the quadratic curve. The tracking device described in 1. Based on the signal level of the signal, a tracking unit that corrects the predicted trajectory value by calculating a tracking offset time used to reduce an error included in a position where the antenna is directly facing at a certain time,
Based on the predicted trajectory value corrected by the correction unit or the tracking unit, the driving unit performs control so that the antenna directly faces the position of the target at a certain reference time indicated by the predicted trajectory value. , Each of the position of the target at a time advanced by a first tracking time from the reference time and the position of the target at a time delayed by a second tracking time from the reference time indicated by the predicted trajectory value. , Control the antenna to face
The tracking unit includes a position of the target at each of the reference time, a time when the antenna is advanced by the first tracking time from the reference time, and a time that is delayed by the second tracking time from the reference time. The tracking offset time is calculated based on the signal level of the signal when facing directly, and the trajectory prediction value is corrected based on the tracking offset time,
The drive unit repeats the control process, and the tracking unit repeats the correction process according to a change in time,
The tracking device according to any one of claims 1 to 5. Based on the predicted trajectory value corrected by the correction unit or the tracking unit, the driving unit performs control so that the antenna directly faces the position of the target at a certain reference time indicated by the predicted trajectory value. Only when the signal level of the signal when the antenna is directly facing the position of the target object is equal to or less than a threshold value, the trajectory prediction value indicates that the first tracking time has advanced from the reference time. Control the antenna to face each of the position of the target at a time and the position of the target at a time delayed by the second tracking time from the reference time;
The tracking unit detects the antenna from the reference time and the reference time only when the signal level of the signal when the antenna is facing the target position at the reference time is equal to or less than a threshold value. Based on the signal level of the signal when facing the target position at each of the time advanced by the first tracking time and the time delayed by the second tracking time from the reference time, the tracking Calculating an offset time, and correcting the predicted trajectory value based on the tracking offset time;
The tracking device according to claim 6.   The absolute values of the first tracking time and the second tracking time are obtained by dividing the beam width of the antenna by a real value not less than 10 and not more than 20, respectively, and the traveling direction of the target in the driving coordinate system of the antenna The tracking device according to claim 6, wherein the tracking device is a value divided by an angular velocity of The drive unit performs control of the antenna within a range in which an elevation angle satisfies a predetermined condition, and repeats the control process at regular time intervals,
The tracking unit repeats the correction process at the predetermined time interval.
The tracking device according to any one of claims 6 to 8. A signal tracking unit that calculates a position of the target based on a signal received by the antenna;
A main drive unit for controlling the antenna based on the position of the target calculated by the signal tracking unit;
A switching unit that switches between control of the antenna by the main drive unit and control of the antenna by the drive unit;
The offset time calculation unit indicates a position vector of the position facing the antenna controlled by the main driving unit at a certain time and the predicted trajectory value with respect to the antenna in the driving coordinate system of the antenna. Calculating the offset time based on an angle formed by a position vector of the target at the time;
The tracking device according to any one of claims 1 to 9. A tracking method for controlling an antenna that receives a signal from a target,
An acquisition step of acquiring a trajectory prediction value that is a prediction value of the position of the target at each time;
Calculate an offset time that represents a time lag in the orbit between the position of the target at a certain time estimated from the signal received by the antenna and the position of the target at the time indicated by the predicted trajectory value Offset time calculating step to perform,
A selection step of acquiring information indicating a degree of error included in the predicted trajectory value, and selecting one of a plurality of trajectory correction models used for correcting the error included in the predicted trajectory value based on the information; ,
Applying the offset time calculated in the offset time calculation step to the trajectory correction model selected in the selection step, and correcting the trajectory prediction value;
A driving step of driving the antenna based on the predicted trajectory value corrected in the correction step;
A tracking method comprising: To the computer that controls the antenna that receives the signal from the target,
An acquisition step of acquiring a trajectory prediction value that is a prediction value of the position of the target at each time;
Calculate an offset time that represents a time lag in the orbit between the position of the target at a certain time estimated from the signal received by the antenna and the position of the target at the time indicated by the predicted trajectory value Offset time calculating step to perform,
A selection step of acquiring information indicating a degree of error included in the predicted trajectory value, and selecting one of a plurality of trajectory correction models used for correcting the error included in the predicted trajectory value based on the information; ,
Applying the offset time calculated in the offset time calculation step to the trajectory correction model selected in the selection step, and correcting the trajectory prediction value;
A driving step of driving the antenna based on the predicted trajectory value corrected in the correction step;
A program for running

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