Low-orbit double-feed overhead tracking method based on XY architecture

Abstract

The present invention proposes a low-orbit dual-feed overhead tracking method based on an X-Y architecture, including: calculating the theoretical angle of an AZ frame antenna, determining the cosine matrix of the theoretical angle of the antenna according to the theoretical angle of the AZ frame antenna; determining the cosine matrix of the X-Y frame pointing angle according to the installation error matrix and the installation plane angle matrix; reversely solving the X-Y frame pointing angle according to the coordinate rotation sequence yxz of the X-Y frame; and adjusting the X-axis, Y-axis, and polarization axis of the antenna system in real time through a servo system to achieve rapid capture and tracking of the satellite by the antenna. The present invention adopts a dual-feed control algorithm to achieve antenna control, which has high precision, is extremely easy to implement in an embedded system, and occupies less chip memory.

Description

Technical Field

[0001] The present invention belongs to the technical field of satellite communications, and in particular relates to a low-orbit dual-feed overhead tracking method based on an XY architecture. Background Art

[0002] In recent years, with the application and development of satellite communication technology, the development of the US broadband satellite communication system has gone through three major stages: the Defense Satellite Communication System (DSCS), the Military Broadcast Satellite System (GBS) and the Broadband Global Satellite Communication System (WGS). High-capacity low-orbit satellites are a trend for future development.

[0003] Compared with the servo control platform, low-orbit and inclined-orbit satellites will cause the antenna system to face the scenario of over-the-top tracking. Solving the problem of stable tracking at high elevation angles becomes a difficulty that must be overcome. The number of high-frequency low-orbit remote sensing and communication satellites is increasing day by day, and the demand for small and medium-caliber ground tracking antennas is increasing accordingly.

[0004] At present, the moving antenna mainly relies on the carrier's attitude acquisition equipment (such as Beidou, inertial navigation, attitude and navigation instrument, etc.) to obtain the carrier's attitude data, and uses the encoder's pulse feedback to update the antenna's rotation angle position information in real time, and finally realizes the closed-loop control of the antenna control platform. This servo control scheme is heavily dependent on the carrier's attitude acquisition equipment, making the currently produced antennas less versatile, and because the closed-loop control belongs to feedback regulation, the real-time performance is poor, and the lag of the carrier's attitude data and the antenna's rotation angle information will cause the antenna control platform to produce a large control error. Summary of the invention

[0005] The present invention proposes a low-orbit double-fed overhead tracking method based on an XY architecture.

[0006] The technical solution to achieve the purpose of the present invention is: a low-orbit double-fed overhead tracking method based on an XY structure, comprising:

[0007] Calculate the theoretical angle of the AZ frame antenna, and determine the cosine matrix of the theoretical angle of the antenna according to the theoretical angle of the AZ frame antenna;

[0008] Determine the XY frame pointing angle cosine matrix based on the installation error matrix and the installation plane angle matrix;

[0009] According to the coordinate rotation order yxz of the XY frame, the XY frame pointing angle is solved in reverse;

[0010] The servo system is used to adjust the X-axis, Y-axis, and polarization axis of the antenna system in real time to enable the antenna to quickly capture and track the satellite.

[0011] Preferably, the theoretical angle of the AZ frame antenna is specifically:

[0012]

[0013] Where M is the difference between the satellite longitude and the receiving location longitude, N is the receiving location latitude, (θ 1 ,θ 2 ,θ 3 ) are the theoretical azimuth, elevation and polarization angles of the AZ frame antenna respectively.

[0014] Preferably, the cosine matrix of the antenna theoretical angle determined according to the AZ frame antenna theoretical angle is specifically:

[0015] In the formula, (θ 1 ,θ 2 ,θ 3 ) are the theoretical azimuth, elevation and polarization angles of the AZ frame antenna respectively.

[0016] Preferably, the installation error matrix is ​​specifically:

[0017]

[0018] In the formula, They are the angle between the Y-axis installation direction and the heading of the antenna installation position, the angle between the Y-axis and the installation plane, and the angle between the X-axis and the installation horizontal plane.

[0019] Preferably, the installation plane angle matrix is ​​specifically:

[0020]

[0021] In the formula, They are the heading angle, pitch angle, and roll angle of the installation plane.

[0022] Preferably, the XY frame pointing angle cosine matrix is ​​specifically:

[0023] In the formula, C 理论角 is the cosine matrix of the antenna theoretical angle, is the installation error matrix, is the mounting plane angle matrix.

[0024] Preferably, the XY frame pointing angle is solved inversely according to the coordinate rotation sequence yxz of the XY frame:

[0025]

[0026] In the formula, They are the X angle, Y angle, and polarization angle of the XY frame antenna.

[0027] Preferably, the coordinate rotation sequence yxz of the XY frame is determined as follows: the antenna is in a power-on initialization state, the antenna surface is vertical to the mounting surface and faces upward as the coordinate system z-axis, the antenna surface is horizontal to the mounting surface and faces right as the x-axis, and faces forward as the y-axis. At this time, the X frame rotation angle is zero degrees, and the Y frame rotation angle is zero degrees; the X frame rotates clockwise to be positive and counterclockwise to be negative, the Y frame rotates clockwise to be positive and counterclockwise to be negative, the X frame rotates first, and the Y frame rotates later, corresponding to the coordinate system rotation sequence of first the y-axis, then the x-axis, and then the z-axis.

[0028] Preferably, the specific method of adjusting the X-axis, Y-axis, and polarization axis of the antenna system in real time through the servo system to achieve rapid capture and tracking of the satellite by the antenna is:

[0029] The target speed of the antenna is obtained by calculating the two pointing angles of the antenna, and the target speed is assigned to the antenna servo system. The antenna servo system performs speed closed-loop control by reading the encoder pulses in real time.

[0030] Preferably, the antenna target speed is specifically:

[0031]

[0032] In the formula, θ XY The calculated pointing angle for the XY frame antenna, is the last pointing angle, and fre is the frequency of calculating the two pointing angles.

[0033] Compared with the prior art, the present invention has the following significant advantages:

[0034] 1. The method for determining the theoretical angle of the XY frame antenna in the present invention is simple and convenient;

[0035] 2. The present invention adopts a dual-feed control algorithm to realize antenna control, which has high precision and is extremely easy to realize in embedded systems, occupying less chip memory.

[0036] The present invention is described in further detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flow chart of the present invention.

[0038] Figure 2 This is a schematic diagram of the static signal level.

[0039] Figure 3 A schematic diagram of dynamic signal levels. DETAILED DESCRIPTION

[0040] like Figure 1 As shown, a low-orbit double-feed overhead tracking method based on an XY architecture comprises the following steps:

[0041] Currently, the theoretical angles of satellite target orbits are derived based on the geodetic coordinate system, while the antenna servo tracking angle calculation needs to be based on the antenna frame coordinate system, so the theoretical angles in the geodetic coordinate system need to be derived to the antenna frame coordinate system.

[0042] According to the XY frame antenna structure, its coordinate system is defined as follows: the antenna is powered on and initialized, the antenna surface is vertical to the installation surface and faces upward as the coordinate system z-axis, the antenna surface is horizontal to the installation surface and faces right as the x-axis, and faces forward as the y-axis. At this time, the X frame rotation angle is zero degrees, and the Y frame rotation angle is zero degrees; the X frame rotates clockwise to be positive, and counterclockwise to be negative, and the Y frame rotates clockwise to be positive, and counterclockwise to be negative. The X frame rotates first, and the Y frame rotates later, corresponding to the coordinate system rotation order of the y-axis first, then the x-axis, and then the z-axis.

[0043] The difference in the derivation of antenna theoretical angles of different frames lies in the different order of the rotation axes, but the final direction cosine matrix is ​​the same. Currently, most antenna frame structures are AZ frame structures. The calculation of the theoretical angle of AZ frame antenna can be obtained by the existing formula:

[0044]

[0045] In formula (1), X = satellite longitude - receiving location longitude, Y = receiving location latitude, (θ 1 ,θ 2 ,θ 3 ) are the theoretical azimuth, elevation and polarization angles of the AZ frame antenna respectively.

[0046] The cosine matrix of the antenna theoretical angle can be derived from this:

[0047]

[0048] In formula (2), (θ 1 ,θ 2 ,θ 3 ) are the theoretical azimuth, elevation and polarization angles of the AZ frame antenna respectively.

[0049] There will be certain errors in the actual antenna processing and installation. After initialization, the antenna surface cannot be guaranteed to be perpendicular to the installation surface. At the same time, the antenna installation position may also change in real time, such as a moving antenna. In summary, the antenna installation error and the installation plane angle need to be considered. The error matrix is ​​shown in Formula 3, and the installation plane angle matrix is ​​shown in Formula 4:

[0050]

[0051]

[0052] In formula 3, They are the angle between the Y-axis installation direction and the antenna installation position heading, the angle between the Y-axis and the installation plane, and the angle between the X-axis and the installation horizontal plane. In formula 4, They are the heading angle, pitch angle and roll angle of the installation plane, which are measured by the inertial navigation system.

[0053] The new XY frame points to the angle, as shown in Formula 5 below:

[0054]

[0055] According to the coordinate rotation order yxz of the XY frame, the pointing angle is solved in reverse, see formula 6:

[0056]

[0057] In formula 6, They are the X angle, Y angle, and polarization angle of the XY frame antenna.

[0058] The antenna satellite capture and tracking design is based on the antenna servo control and tracking. The antenna servo control platform uses the attitude of the antenna installation surface (true heading, roll, pitch) and the satellite and ground position parameters (latitude and longitude, obtained by Beidou) provided by the inertial navigation system, plus the satellite position parameters, and the control unit calculates the antenna X angle, Y angle, and polarization angle. The servo system adjusts the X axis, Y axis, and polarization axis of the antenna system in real time to achieve rapid capture and tracking of the antenna to the satellite, so that the antenna beam is always aimed at the satellite.

[0059] In order to minimize the control error caused by system delay, the present invention adopts a double-feed (feedforward + feedback) model to obtain a faster control response.

[0060] Feedforward control is to calculate the antenna target speed by calculating the forward and backward pointing angles of the antenna (see formula 7), and assign the target speed to the antenna servo system. The antenna servo system then performs speed closed-loop control by reading the encoder pulses in real time to achieve target speed tracking of the X-axis, Y-axis, and polarization axis of the antenna system.

[0061]

[0062] In formula 7, θ XY The calculated pointing angle for the XY frame antenna, is the last pointing angle, and fre is the frequency of calculating the two pointing angles.

[0063] The principle of the double-fed control algorithm of the present invention is easy to understand, and is extremely easy to implement in an embedded system, occupying less chip memory.

[0064] Example

[0065] Take a city as an observation point for example (longitude 32°, latitude 118.8°), track the satellite longitude 110.5° (theoretical azimuth 195.4°, pitch 51.8°), antenna installation conditions, place the antenna on a fixture with a tilt angle of 37°, the fixture is fixed on the servo swing table, the angle is to simulate overhead tracking. The inertial navigation device is installed on the swing table to test the real-time attitude of the swing table.

[0066] The mounting surface angle in formula 4 is measured by the inertial navigation device They are 192.4°, 0°, and -0.5° respectively. The error angle in formula 3 is measured by a high-precision level and inertial navigation equipment. They are -0.5°, -37°, and 0.3° respectively. According to the above formulas 1 to 6, the theoretical angles of the XY frame antenna can be calculated to be X=1.6°, Y=-1.1°, and JH=-1.7°.

[0067] After the XY frame antenna is initialized normally, the antenna is adjusted to the theoretical angle. The antenna receives the satellite RF signal level through the spectrum analyzer to verify whether the antenna theoretical angle is calculated correctly. Figure 2 .

[0068] After adjusting the antenna X angle, Y angle, and polarization JH angle, the antenna receiving signal level did not become stronger, so it can be judged that the theoretical angle calculation of the XY frame antenna is correct and there is no deviation.

[0069] The swing table starts to swing in three axes, 8 degrees / 5 seconds for each axis. The spectrum analyzer receives the beacon level as Figure 3 .

[0070] from Figure 3 It can be seen that during the swinging process of the swing platform, the antenna receiving signal level drops less, indicating that the antenna can be stably tracked in real time during the dynamic process through the invented dual-feed control algorithm.

[0071] The present invention realizes stable tracking of the antenna without blind spots when it passes over the top of the antenna.

Claims

1. A low-orbit double-fed overhead tracking method based on an XY architecture, characterized in that: include: Calculate the theoretical angle of the AZ frame antenna, and determine the cosine matrix of the theoretical angle of the antenna according to the theoretical angle of the AZ frame antenna; Determine the XY frame pointing angle cosine matrix based on the installation error matrix and the installation plane angle matrix; According to the coordinate rotation order yxz of the XY frame, the XY frame pointing angle is solved in reverse; The servo system is used to adjust the X-axis, Y-axis, and polarization axis of the antenna system in real time to enable the antenna to quickly capture and track the satellite.

2. The low-orbit double-fed overhead tracking method based on XY architecture according to claim 1, characterized in that: The specific theoretical angle of the AZ frame antenna is: Where M is the difference between the satellite longitude and the receiving location longitude, N is the receiving location latitude, and (θ1, θ2, θ3) are the theoretical azimuth, elevation, and polarization angles of the AZ frame antenna, respectively.

3. The low-orbit double-fed overhead tracking method based on XY architecture according to claim 1, characterized in that: The cosine matrix of the antenna theoretical angle determined according to the AZ frame antenna theoretical angle is specifically: Where (θ1, θ2, θ3) are the theoretical azimuth, elevation, and polarization angles of the AZ frame antenna, respectively.

4. The low-orbit double-fed overhead tracking method based on XY architecture according to claim 1, characterized in that: The installation error matrix is ​​as follows: In the formula, They are the angle between the Y-axis installation direction and the heading of the antenna installation position, the angle between the Y-axis and the installation plane, and the angle between the X-axis and the installation horizontal plane.

5. The low-orbit double-fed overhead tracking method based on XY architecture according to claim 1, characterized in that: The installation plane angle matrix is ​​as follows: In the formula, They are the heading angle, pitch angle, and roll angle of the installation plane.

6. The low-orbit double-fed overhead tracking method based on XY architecture according to claim 1, characterized in that: The XY frame points to the angle cosine matrix specifically: In the formula, C 理论角 is the cosine matrix of the antenna theoretical angle, is the installation error matrix, is the mounting plane angle matrix.

7. The low-orbit double-fed overhead tracking method based on XY architecture according to claim 6, characterized in that: According to the coordinate rotation order yxz of the XY frame, the XY frame pointing angle is solved in reverse as follows: In the formula, They are the X angle, Y angle, and polarization angle of the XY frame antenna.

8. The low-orbit double-fed overhead tracking method based on XY architecture according to claim 1, characterized in that: The coordinate rotation order yxz of the XY frame is determined as follows: the antenna is in the power-on initialization state, the antenna surface is vertical to the installation surface and faces upward as the coordinate system z axis, the antenna surface is horizontal to the installation surface and faces right as the x axis, and faces forward as the y axis. At this time, the X frame rotation angle is zero degree, and the Y frame rotation angle is zero degree; the X frame rotates clockwise to be positive and counterclockwise to be negative, the Y frame rotates clockwise to be positive and counterclockwise to be negative, the X frame rotates first and the Y frame rotates later, corresponding to the coordinate system rotation order of first the y axis, then the x axis, and then the z axis.

9. The low-orbit double-fed overhead tracking method based on XY architecture according to claim 1, characterized in that: The specific method of adjusting the X-axis, Y-axis, and polarization axis of the antenna system in real time through the servo system to achieve rapid capture and tracking of the satellite by the antenna is as follows: The target speed of the antenna is obtained by calculating the two pointing angles of the antenna, and the target speed is assigned to the antenna servo system. The antenna servo system performs speed closed-loop control by reading the encoder pulses in real time.

10. The low-orbit double-fed overhead tracking method based on XY architecture according to claim 9, characterized in that: The antenna target speed is specifically: In the formula, θ XY The calculated pointing angle for the XY frame antenna, is the last pointing angle, and fre is the frequency of calculating the two pointing angles.

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