JP2008211487A - Antenna apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna on an altazimuth mount which maintains a directivity accuracy by correcting a directivity error due to deformation of a frame caused by wind power and sun heat by means of a constitution having one EL angle detector and a correction algorithm. <P>SOLUTION: The antenna on the altazimuth mount is provided with an EL angle difference calculating means which has the EL angle detectors at both ends of the frame supporting an EL axis and calculates an angle difference of an elevation angle detected by each EL angle detector when the EL axis is distorted by the deformation of the frame due to wind power and sun heat, an EL distortion amount correcting means which corrects an EL command value based on the calculated angle difference of the elevation angle, an AZ error calculating means which calculates an azimuth angle error based on the calculated angle difference of the elevation angle, a height of the frame and a length between both ends of the frame, and an AZ distortion amount correcting means which corrects an AZ command value based on the calculated azimuth angle error. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antenna device that improves the directivity of a large parabolic antenna.

As is well known, parabolic antennas are used as antennas for radio telescopes for astronomical observation, satellite-to-ground station communications, radars, etc. In recent years, the resolution has been improved to enable more precise observation. Therefore, the main reflecting mirror (hereinafter referred to as the main mirror) tends to be enlarged. In addition, as the primary mirror increases in size, the gantry for supporting it will naturally increase in size. Many large parabolic antennas are exposed to the open air and are therefore susceptible to wind. In particular, the larger the primary mirror, the larger the area that receives the wind, so that a large force is applied to the gantry that supports the primary mirror, causing a phenomenon that the gantry is elastically deformed. Large parabolic antennas are also susceptible to solar radiation and outside air temperature, and the phenomenon of thermal deformation occurs due to temperature distribution. Therefore, the AZ (Azimuth) axis and EL (Elevation) axis information that is driven to determine the direction of the primary mirror is detected by an encoder and fed back to correct the azimuth and elevation angles. Is applied (see, for example, Patent Document 1).
In addition, two sets of light beam generators and optical position detectors are provided on the AZ angle detector and EL angle detector, respectively, and the torsional component of the AZ axis is obtained from the difference in the output of the optical position detector for AZ. The twisted component of the EL axis is obtained from the difference between the sum of the output of the EL optical position detector and the sum of the output of the AZ optical position detector, and the angle from the angle detector directly connected to each axis by these components. A technique for correcting the signal and detecting the antenna directivity angle has been proposed (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 2003-315012 Japanese Patent No. 2560475 (FIG. 1)

When the technique described in Patent Document 1 as described above is applied, it seems that the azimuth angle and elevation angle of the antenna can be controlled according to the command values even when subjected to wind deformation and thermal deformation. However, in actuality, deformation of the pedestal due to wind force or heat appears as torsional distortion of the EL axis that determines the elevation angle and azimuth angle, resulting in a pointing error that cannot be detected only by the current encoder (one EL angle detector). This is a factor that cannot achieve a certain pointing accuracy in a large parabolic antenna.
On the other hand, in the case of the technique described in Patent Document 2, since the gantry blocks the light beam in the actual structure, there is a limit to the structure for preventing it. There is also a problem with the thermal stability of the light beam. In particular, the light beam is susceptible to temperature drift due to the heat generated by the light beam generator itself and the surrounding heat, and as a result, whether the thermal deformation of the gantry is being measured or the thermal drift of the beam is measured. It becomes difficult to determine whether it is present. Although Patent Document 2 describes a case where two EL angle detectors are provided, since usually one is used, this is considered to be merely a preliminary use.

  The present invention has been made to solve the above-described problems, and is a configuration in which an EL angle detector is added to a pointing error caused by deformation of a pedestal caused by wind power or solar heat in an abutment type antenna. An object of the present invention is to obtain an antenna device that maintains a pointing accuracy by correcting with a correction algorithm.

  The antenna device according to the present invention is directed to an antenna device that directs the antenna to a target by applying the EL command value and the AZ command value to the corresponding EL control system and AZ control system and rotating the antenna around the EL axis and the AZ axis. In this case, an EL angle detector is provided at each end of the pedestal that rotatably supports both ends of the EL shaft, and one of the EL angle detectors is shared with the EL control system, and the gantry is deformed by wind force or solar heat. EL angle difference calculating means for calculating the angle difference of the elevation angle detected by each EL angle detector when the EL axis is twisted, and an EL command value based on the angle difference of the elevation angle calculated by the EL angle difference calculation means An azimuth angle error is calculated based on the elevation angle difference calculated by the EL distortion amount correcting means for correcting the angle, the height of the gantry, and the length between both ends of the gantry. And error calculating means, those having a AZ distortion amount correcting means for correcting the AZ command value based on the azimuth angle error calculated by AZ error calculation means.

  According to the present invention, a component relating to the twist of the EL axis caused by the deformation of the gantry caused by wind power or solar heat is obtained as the difference between the angles detected by the two EL angle detectors installed on the EL axis. Since the algorithm for correcting the elevation and azimuth angle errors based on the above is incorporated in the original EL control system and AZ control system, even if a pointing error occurs due to the deformation of the gantry, it is corrected and directed The accuracy can be kept high. Further, since an encoder or a resolver is used as the EL angle detector, the detection output of the EL angle detector is not affected by its own heat.

Embodiment 1 FIG.
1A and 1B are external views showing the configuration of an antenna device according to Embodiment 1 of the present invention. FIG. 1A is a front view and FIG. 1B is a side view.
In the figure, this antenna device is a gravitational parabolic antenna that determines the antenna orientation by rotating the antenna about the AZ axis and the EL axis. The gantry base 8 is installed on the ground, and the AZ turntable 6 for changing the azimuth angle is horizontally provided thereon. The AZ turntable 6 has a yoke (mounting base) 7 fixed thereon, and can be rotated around the AZ shaft 10 by a motor (not shown). An AZ angle detector 11 for detecting the azimuth angle of the antenna is provided between the yoke 7 and the AZ axis 10. On both shoulder portions of the yoke 7, there are provided a main mirror (main reflecting mirror) 4 and an EL shaft 2 that supports the receiver chamber 5. The elevation angle directed by the primary mirror 4 is set by rotating the EL shaft 2 by the EL rotation drive unit 1 provided between the primary mirror 4 and the yoke 7. Therefore, the EL rotation driving unit 1 includes a motor installed at the lower portion of the yoke 7 and a gear structure that transmits the rotation to the EL shaft 2. An EL angle detector 3 that detects the elevation angle of the antenna is provided at the bearing portion of the shoulder portion of the yoke 7 that supports the EL shaft 2. As the EL angle detector 3 and the AZ angle detector 11, an encoder or a resolver is used.

An example of the structure of the bearing portion of the shoulder portion of the yoke 7 is shown in FIG. The EL shaft 2 is rotatably supported by a bearing 9 mounted on a yoke seat surface that is an EL fixing side. The EL angle detector 3 is supported by a yoke 7 on the EL fixing side, and detects a rotation angle (that is, an elevation angle) of a shaft 31 fixed to the EL shaft 2 with its center aligned.
The above description is the same as the general configuration of a conventional large parabolic antenna. However, in the case of the present invention, two EL angle detectors 3 are provided on the left and right shoulders of the yoke 7, for a total of two. And provide the features described below.

FIG. 2 is a diagram of the parabolic antenna as viewed from above. The main mirror 4 receives wind and the yoke 7 is deformed, the EL shaft 2 is twisted, and the AZ axis is substantially deviated. It is shown in FIG. 2A shows a normal state, but when the main mirror 4 receives wind from an oblique direction, a force is applied to the surface facing the wind direction, so one side of the main mirror 4 (left side in the figure). The wind force concentrates, the corresponding yoke is twisted as indicated by 7 'shown in FIG. 2B, the AZ axis 2 is distorted, and the azimuth angle of the primary mirror 4 is changed.
FIG. 3 is a view of the yoke 7 as viewed from above the EL axis. When the wind is received as shown in FIG. 2 or when only one side of the yoke 7 is exposed to sunlight, the yoke 7 is deformed and the EL axis 2 is It is a schematic representation of the twisted state. The yoke 7 is largely deformed in the vicinity of the EL shaft 2, and the bearing seat surface is inclined downward from the horizontal position. That is, since the EL shaft 2 is twisted and deformed clockwise, the elevation angle of the primary mirror 4 changes.

FIG. 4 shows the relationship between the deformation of the EL axis 2 caused by the deformation of the yoke structure described in FIGS. 2 and 3 and the change in elevation angle and azimuth angle. When the inclinations of the two EL bearing seat surfaces of the yoke 7 are different on the left and right, the left and right EL angle detectors 3 detect values of different angles. Since the angle difference has a close correlation with the twist amount of the EL axis 2, the angle difference may be calculated to correct the pointing error. A specific correction formula is derived below.
The EL angle detector 3 detects the relative rotation angle between the yoke 7 and the EL shaft 2. When the parabolic antenna device is a steel body and is not distorted by a load such as wind force, the correct elevation angle is detected as it is. Become. However, when the yoke 7 is deformed as described above, elements other than the elevation angle enter the left and right EL angle detectors 3. For example, if there is a difference between the detection angles of the left and right EL angle detectors 3, the difference represents the deformation of the EL shaft 2 due to the left and right twists of the yoke 7. When the detection angle (elevation angle measurement value) of the right EL angle detector 3 is E _R , and the detection angle (elevation angle measurement value) of the left resolver is E _L , the angle difference χ is expressed by the following equation (1). This angle difference χ is used for elevation angle correction.
χ = E _R −E _L (1)

Here, if the yoke 7 is inclined linearly, the deformation amount D in the front-rear (± Y) direction that occurs between the left and right sides of the EL shaft 2 is obtained by using the height H and χ (rad) of the yoke 7. It can be expressed by equation (2).
D = H · χ (2)
Actually, the yoke 7 is not simply deformed. Therefore, the equation (2) is multiplied by a proportional constant or coefficient C representing the relationship between the angle difference χ and the azimuth pointing error due to the torsional component of the gantry (3 ). C is obtained by the method described later. In consideration of deformation close to a cantilever, if C is a coefficient of a higher order expression, the accuracy can be further increased.
D = C ・ H ・ χ (3)
Next, if the distance between both ends of the yoke supporting the EL axis 2 (or the same as the length of the EL axis in a normal state) is L, the error (azimuth angle error) θ _AZ of the AZ axis is (4). I can express. This error θ _AZ is calculated and used for azimuth correction.
θ _AZ = D / L = C · H · χ / L (4)

Here, there are two methods for determining the proportional constant C.
One is a typical wind deformation or thermal deformation mode that causes the deformation of the yoke. When the EL axis is twisted, the difference between the detection angles of the left and right EL angle detectors (the above angle difference χ) and the misorientation This is a method for obtaining the relationship between the quantities (left side of the above formula (4); θ _AZ ) using FEM (Finite Element Method). If the angle difference χ is the difference in the inclination of the EL bearing seat surface, the analysis becomes relatively easy.
Another method is to monitor the relationship between the difference in detection angle between the left and right EL angle detectors and the antenna pointing (directivity) error after entering the actual operation stage of the antenna. This is a method for calculating the optimum value. By determining a proportionality constant (a coefficient in the case of higher order) using an actual machine, it is possible to have higher directivity accuracy than AZ and EL correction value calculations that rely only on the FEM simulation.

FIG. 6 is a block diagram showing a control function configuration of the antenna apparatus according to Embodiment 1 of the present invention.
First, a general azimuth angle and elevation angle setting control of a theft platform parabolic antenna will be described. An AZ command value and an EL command value for directing the antenna toward the target are given from an operation device (not shown). The AZ control unit 202 generates a control signal corresponding to the given EL command value and supplies it to the AZ rotation drive unit 203. In the AZ rotation driving unit 203, the motor is driven to rotate the gantry around the AZ axis to change the orientation of the opening surface of the antenna. The azimuth angle of the antenna at this time is detected by the AZ angle detector 11 and given to the subtractor 201. The subtractor 201 obtains the difference between the AZ command value and the detected azimuth angle and gives it to the AZ control unit 202. The AZ control unit 202 controls the AZ rotation driving unit 203 until the difference becomes zero. Such a feedback method is similarly applied to a loop that is configured to control the setting of the elevation angle, that is, the subtractor 101, the EL control unit 102, the EL rotation driving unit 1, and the first EL angle detector 3A attached to one of the yokes. It is.

In the present invention, the second EL angle detector 3B, the EL angle difference calculation unit 106, the EL distortion amount correction unit 107, and the AZ error attached to the shoulder on the opposite side of the yoke with respect to the configuration of the EL and AZ control system. A calculation unit 206 and an AZ distortion amount correction unit 207 are added.
Detection angles (elevation angle measurement values) obtained from the first EL angle detector 3A and the second EL angle detector 3B provided at both ends of the EL axis are given to the EL angle difference calculation unit 106. The EL angle difference calculation unit 106 calculates the EL angle difference from both detection angles according to the equation (1). As described above, when deformation of the pedestal due to wind force or heat appears as twist distortion of the EL axis, the EL angle difference exhibits a finite value. This EL angle difference is given to the EL distortion amount correction unit 107 and the AZ error calculation unit 206. The EL distortion amount correction unit 107 corrects the EL command value by adding or subtracting the EL angle to the EL command value, and outputs it to the EL control system. On the other hand, the AZ error calculation unit 206 calculates the azimuth error based on the given EL angle difference, the height of the yoke supporting the EL axis, and the length of the EL axis according to the equations (2) to (4). And output to the AZ distortion amount correction unit 207. The AZ distortion amount correcting unit 207 corrects the AZ command value by adding or subtracting the azimuth angle error calculated by the AZ error calculating unit 206 to the AZ command value, and outputs it to the AZ control system.

  As described above, according to the first embodiment, the angle detected by the two EL angle detectors installed on the EL axis is a component related to the twist of the EL axis caused by the deformation of the gantry generated by wind power or solar heat. The EL command value is corrected based on this angle difference, and the AZ command value is corrected by calculating the azimuth error based on the angle difference, the height of the gantry, and the length between both ends of the gantry. Since the corrected command value is incorporated in the original EL control system and AZ control system, even if a pointing error occurs due to the deformation of the gantry, it can be corrected to maintain high pointing accuracy. it can. In addition, since an encoder or resolver is used as the EL angle detector, the detection output of the EL angle detector can obtain a detection angle that is not affected by heat, so that the thermal error of the detector itself appears in the angle difference. There is no.

It is an external view which shows the structure of the antenna apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows typically the state from which AZ axis | shaft shifts | deviates by the twist phenomenon of the EL axis | shaft by wind force. It is explanatory drawing which shows typically the state in which EL axis | shaft twists by the deformation | transformation of the yoke by a wind force or solar radiation heat. It is explanatory drawing which shows the relationship between a deformation | transformation of EL axis | shaft, and the change of an elevation angle and an azimuth. It is explanatory drawing which shows the structural example of the bearing part of the yoke which concerns on Embodiment 1 of this invention. It is a block diagram which shows the control function structure of the antenna apparatus by Embodiment 1 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 EL rotation drive part, 2 EL axis | shaft, 3 EL angle detector, 4 Primary mirror, 5 Receiver room, 6 AZ rotation stand, 7 Yoke (mounting base), 8 Mounting base, 9 Bearing, 10 AZ axis, 11 AZ angle Detector 101, 201 Subtractor, 102 EL control unit, 3A 1st EL angle detector, 3B 2nd EL angle detector, 106 EL angle difference calculation unit, 107 EL distortion amount correction unit, 202 AZ control unit, 203 AZ rotation Drive unit, 206 AZ error calculation unit, 207 AZ distortion amount correction unit.

Claims (4)

In an antenna device for directing the antenna to a target by applying the EL command value and the AZ command value to the corresponding EL control system and AZ control system and rotating the antenna around the EL axis and the AZ axis.
An EL angle detector is provided at each end of a gantry that rotatably supports both ends of the EL axis, and one EL angle detector is shared with the EL control system.
EL angle difference calculating means for calculating the angle difference of the elevation angle detected by each EL angle detector when the EL axis is twisted due to deformation of the pedestal by wind force or solar heat;
EL distortion amount correction means for correcting the EL command value based on the angle difference of the elevation angle calculated by the EL angle difference calculation means;
AZ error calculation means for calculating an azimuth error based on the angle difference of the elevation angle calculated by the EL angle difference calculation means, the height of the gantry and the length between both ends of the gantry,
An antenna apparatus comprising: an AZ distortion amount correcting means for correcting an AZ command value based on the azimuth angle error calculated by the AZ error calculating means. The EL angle difference calculation means
The amount of deformation of the EL axis by multiplying the angle difference of the elevation angle calculated by the EL angle difference calculating means, the height of the gantry, and a proportionality constant or coefficient representing the relationship between the angle difference and the azimuth angle pointing error due to the torsional component of the gantry To calculate
2. The antenna apparatus according to claim 1, wherein an azimuth angle error is calculated by dividing the deformation amount of the EL axis by the length between both ends of the gantry.   3. The antenna device according to claim 2, wherein the proportionality constant or the coefficient is a value obtained by using a simulation by a finite element method for deformation of the gantry due to wind or solar heat.   3. The proportionality constant or coefficient is an optimum value obtained based on relational data between a difference between detection angles of both EL angle detectors and an antenna directivity error accumulated in an antenna operation stage. The antenna device described.

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