A dynamic correction method for installation error of airborne satellite communication antenna

Abstract

The present invention discloses a method for dynamically correcting the installation error of an airborne satellite communication antenna, and belongs to the field of antenna calibration. The method comprises the following steps: under different flight attitudes of the aircraft, the airborne satellite communication antenna obtains azimuth and pitch correction values ​​by scanning stars and circles; based on the least square method, the recorded azimuth and pitch correction values ​​are fitted with error coefficients to calculate the azimuth zero position error, the roll and pitch errors of the antenna installation surface; the true attitude of the antenna installation surface is obtained through the azimuth zero position error, the roll and pitch errors of the antenna installation surface, and the antenna tracking control is performed using the true attitude, which is continuously iterated. The present invention can dynamically correct the installation error of the airborne satellite communication antenna.

Description

Technical Field

[0001] The invention relates to the field of antenna calibration, and in particular to a method for dynamically correcting installation errors of airborne satellite communication antennas. Background Art

[0002] The antenna needs to calculate the satellite pointing angle based on the position and attitude information of the target satellite and aircraft, control the antenna's axes to quickly rotate to aim at the target and implement tracking. The aircraft's position and attitude are provided by the high-precision inertial navigation on the carrier aircraft. However, when the antenna is installed, there are problems such as the installation surface is not parallel to the inertial navigation installation surface, and the azimuth zero point does not coincide with the heading.

[0003] When the antenna is installed, the installation surface is not parallel to the inertial navigation installation surface, and the azimuth zero point does not coincide with the heading. This will cause a deviation between the heading and attitude provided by the inertial navigation to the antenna and the heading and attitude of the actual installation location of the antenna, resulting in a large antenna pointing error and reduced antenna tracking accuracy.

[0004] The existing antenna calibration technology requires the cooperation of ground calibration equipment or calibration towers, and requires a lot of preparation work to analyze the collected data offline. After obtaining the calibration results, it is necessary to verify the calibration effect again. It can be seen that the existing technology has the problem of cumbersome process and difficult implementation. Summary of the invention

[0005] In view of this, the present invention proposes a method for dynamically correcting the installation error of an airborne satellite communication antenna. The method can correct the azimuth zero point error and attitude error of the antenna installation surface and the inertial navigation installation surface, improve the tracking accuracy of the antenna, and can be continuously iterated.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for dynamically correcting installation errors of an airborne satellite communication antenna comprises the following steps:

[0008] (1) The antenna tracks and maintains satellite tracking normally;

[0009] (2) A circle with a radius of a° is superimposed on the satellite tracking angle to achieve circular scanning of the antenna;

[0010] (3) Collect the beacon receiving field strength value during the antenna scanning process and calculate the field strength deviation in azimuth and elevation respectively;

[0011] (4) correcting the azimuth frame control angle and the pitch frame control angle according to the field strength deviation, and calculating the azimuth frame control angle deviation and the pitch frame control angle deviation; recording multiple sets of azimuth frame control angle deviations and pitch frame control angle deviations at different attitudes during the flight of the aircraft;

[0012] (5) Fitting the recorded multiple groups of azimuth mount control angle deviations and elevation mount control angle deviations based on the least squares method to obtain the error coefficients, and then calculate the azimuth zero position error, roll error, and pitch error of the antenna installation surface;

[0013] (6) calculating the true attitude of the antenna installation surface according to the heading, roll, and pitch values ​​provided by the inertial navigation system and the roll error and pitch error of the antenna installation surface obtained in step (5); using the true attitude and combining it with the azimuth zero position error obtained in step (5) to perform antenna tracking control;

[0014] (7) During the tracking process, steps (1) to (6) are continuously executed and iterative correction is performed to achieve error convergence.

[0015] Furthermore, the specific method of step (1) is:

[0016] According to the longitude and latitude of the satellite and the antenna, calculate the theoretical azimuth and elevation pointing angles of the antenna to the satellite:

[0017]

[0018]

[0019] Where:

[0020] A G0 : The theoretical pointing angle of the antenna to the satellite;

[0021] E G0 : The theoretical pointing angle of the antenna to the satellite;

[0022] λ: satellite longitude;

[0023] Satellite latitude (the latitude of a synchronous orbit satellite is 0°);

[0024] λ e : aircraft longitude;

[0025] Aircraft latitude;

[0026] h: distance between satellite and the center of the earth;

[0027] h e : distance between the aircraft and the center of the earth;

[0028] According to A G0 and E G0 Track and maintain satellites.

[0029] Furthermore, the specific method of step (2) is:

[0030] Pointing angle A according to azimuth theory G0, Pitch theoretical pointing angle E G0 As the center, set a scanning path with a pointing deviation of a°, and the azimuth pointing angle of the new scanning path is A G , pitch pointing angle E G for:

[0031] A G =A G0 +a×cos(ωt) (7)

[0032] E G =E G0 +a×sin(ωt) (8)

[0033] Among them, the scanning frequency ω is 1Hz, and a is 1 / 10 of the half-power beamwidth of the antenna;

[0034] The new scanning path forms a spatial orientation of the antenna with (A G0 ,E G0 ) is a closed circle centered on

[0035] The coordinate transformation from the antenna pointing angle to the antenna mount angle is realized through equations (9) and (10), thus realizing scanning control:

[0036]

[0037] E D0 =sin -1 {-cosE G *cos(A G -H)*sinP*cosR+sinE G *cosP*cosR+cosE G *sin(A G -H)*sinR} (10)

[0038] In the formula, A D0 is the azimuth control angle of the antenna mount, E D0 is the antenna mount pitch control angle, A G is the geographical angle of the satellite azimuth, E G is the geographical pitch angle of the satellite, H, R, and P are the heading, roll, and pitch of the aircraft respectively.

[0039] Furthermore, the specific method of step (3) is:

[0040] The antenna circular scanning path is divided into four parts: A, B, C, and D. During each path scanning process, 25 beacon field strength values ​​are collected at equal intervals and recorded as P A1 , P A2 ...P A25 , P B1 , P B2...P B25 , P C1 , P C2 ...P C25 , P D1 , P D2 ...P D25 ; Take the algebraic sum of the beacon strengths received by each part and get P A , P B , P C , P D , then the field strength deviation of the antenna azimuth pointing to the beacon is ΔP 方位 =P A+D -P B+C , the field strength deviation of the beacon in the elevation direction is ΔP 俯仰 =P A+B -P C+D .

[0041] Furthermore, the specific method of step (4) is:

[0042] If ΔP 方位 >0, indicating that the antenna is off center to the right, so the azimuth pointing correction is required (A G0 -a / 20)°, otherwise the azimuth pointing correction (A G0 +a / 20)°, if ΔP 俯仰 >0, indicating that the antenna deviates downward from the center, let (E G0 +a / 20)°, otherwise (E G0 -a / 20)°;

[0043] According to equations (9) and (10), the corrected azimuth frame control angle A is obtained: D1 and the pitch mount control angle E D1 ;

[0044] Continuous scanning until ΔP 方位 , ΔP 俯仰 If it is close to 0 and changes alternately between positive and negative, it means that the antenna is aligned with the satellite. At this time, solve the azimuth mount control angle deviation ΔA D and the pitch mount control angle deviation ΔE D ;

[0045] When the aircraft flies at different headings and attitudes, select 5 groups of ΔA D and ΔE D . They are denoted as ΔA D1 , ΔA D2 , ΔA D3 , ΔA D4 , ΔA D5 and ΔE D1 , ΔE D2 , ΔE D3 , ΔED4 , ΔE D5 .

[0046] Furthermore, the specific method of step (5) is:

[0047] The algebraic expression to be calculated is -A 0 -β m sin(A c -A m )tanE c and -β m cos(A c -A m ), the principle of fitting solution is to minimize the sum of squares of deviations between fitting points and actual points, as follows:

[0048]

[0049]

[0050] Where:

[0051] A 0 -Azimuth null error of the antenna mounting surface;

[0052] A ci -The azimuth angle value of the i-th group of circular scans;

[0053] E ci -The pitch angle value of the i-th group of circular scans;

[0054] A Di - Azimuth correction value for the i-th group of circular scans;

[0055] E Di -The pitch correction value for the i-th group of circular scans;

[0056] The coefficient β can be obtained from the two fitting curves. m1 , β m2 , A m1 , A m2 , A 01 , A 02 ;

[0057] Maximum inclination of the mounting plate β m and the maximum tilt direction A m The conversion formula with rolling error ΔR and pitch error ΔP is:

[0058] ΔP=sin -1 (sinβ m cosA m ) (13)

[0059] ΔR=tg -1(-tgβ m sI m ) (14)

[0060] From this, we can find the two sets of ΔR 1 , ΔR 2 ,ΔP 1 , ΔP 2 , if ΔR 1 , ΔR 2 Deviation greater than 0.2°, or ΔP 1 , ΔP 2 If the deviation is greater than 0.2°, the calculated value is considered to have a large deviation and low credibility, so it is discarded and the values ​​are re-selected, fitted, and ΔR and ΔP are solved.

[0061] Furthermore, the specific method of step (6) is:

[0062] Assume the heading measured by inertial navigation is H 0 , roll is R 0 , pitch is P 0 , H 0 ,R 0 ,P 0 Substitute the real attitude matrix of the antenna installation surface provided by the inertial navigation get:

[0063]

[0064] Where H = H 0 ;

[0065] Substituting the roll and pitch errors ΔR and ΔP into the error matrix, we get

[0066]

[0067] The true posture matrix after error correction is:

[0068]

[0069] According to the relation According to the principle that if two matrices are equal, the elements should be equal, the real pitch P and real roll R of the antenna installation plane are solved;

[0070] The zero position error A obtained in step (5) 0 Subtract it from the output angle of the azimuth encoder, and use the actual pitch P and actual roll R of the antenna installation plane after error correction to solve the corrected control angle according to equations (9) and (10) to achieve error correction tracking.

[0071] The present invention has the following advantages:

[0072] 1. The present invention can be applied to satellite communication antennas of aircraft, and can correct the errors between the mounting surface and the inertial navigation mounting surface, thereby improving the tracking accuracy of the antenna.

[0073] 2. The present invention can automatically correct errors during the flight of the aircraft without human intervention, and the correction is continuous and iterative. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 It is a flow chart of dynamic correction of installation error in an embodiment of the present invention.

[0075] Figure 2 is a circular scanning path diagram in an embodiment of the present invention. DETAILED DESCRIPTION

[0076] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0077] A method for dynamically correcting the installation error of an airborne satellite communication antenna. In this method, the relationship between the influence of the azimuth zero position error and the attitude error on the antenna pointing is as follows:

[0078] A=A c -A 0 -β m sin(A c -A m )tanE c (1)

[0079] E=E c -β m cos(A c -A m ) (2)

[0080] Where:

[0081] A, E—corrected azimuth and elevation angles;

[0082] A c 、E c —The real angle of antenna azimuth and elevation encoder;

[0083] A 0 —azimuth zero error;

[0084] β m , A m —The maximum tilt amount and direction of the mounting plate (i.e., the roll and pitch error angles of the antenna mounting surface).

[0085] The azimuth error angle AA c and pitch error angle EE c Substituting ΔA and ΔE respectively, equations (1) and (2) can be written as:

[0086] ΔA=-A 0 -β m sin(A c -A m )tanE c (3)

[0087] ΔE=-β m cos(A c -A m ) (4)

[0088] Based on this, the specific steps of this method are as follows:

[0089] a) The antenna tracks and maintains the satellite. The theoretical azimuth and elevation angles of the antenna are calculated based on the satellite longitude and the longitude and latitude of the antenna location, and the antenna is controlled to point to the angle.

[0090]

[0091]

[0092] Its parameter description:

[0093] A G0 : The theoretical azimuth angle of the antenna to the satellite;

[0094] E G0 : The theoretical elevation angle of the antenna to the satellite;

[0095] λ: satellite longitude;

[0096] Satellite latitude (the latitude of a synchronous orbit satellite is 0°);

[0097] λ e : aircraft longitude;

[0098] Aircraft latitude;

[0099] h: distance between satellite and the center of the earth;

[0100] h e : Distance between the aircraft and the center of the earth.

[0101] b) Based on the theoretical azimuth pointing angle and the theoretical elevation pointing angle (A G0 、E G0 ) as the center, set a scanning path with a pointing deviation of a°, and the azimuth and elevation pointing angles of the new path are:

[0102] A G =A G0 +a×cos(ωt) (7)

[0103] E G =E G0 +a×sin(ωt) (8)

[0104] The scanning frequency ω is set to 1 Hz, and a is taken as 1 / 10 of the antenna half-power beam width.

[0105] The scanning path will form a spatial orientation of the antenna with (A G0 、E G0 ) is a closed circle with centered on the antenna. The coordinate transformation from the antenna pointing angle to the antenna mount angle is realized through equations (9) and (10), thus realizing scanning control:

[0106]

[0107] E D0 =sin -1 {-cosE G *cos(A G -H)*sinP*cosR+sinE G *cosP*cosR+cosE G *sin(A G -H)*sinR} (10)

[0108] In the formula, A D0 Antenna mount azimuth control angle, E D0 Antenna mount pitch control angle, A G Geographic angle of the satellite azimuth, E G Satellite pitch geographical angle, H, R, P aircraft heading, roll, pitch.

[0109] Collect the beacon receiving airport strength value during the antenna circular scanning process, calculate the field strength deviation of azimuth and pitch respectively, and make angle corrections to azimuth and pitch according to the deviations. Record the azimuth and pitch correction values ​​of 5 groups of aircraft in different postures.

[0110] c) Based on the least squares method, the error coefficients of the stored multiple groups of azimuth and pitch correction values ​​are fitted to obtain the azimuth zero position error A in formulas (3) and (4): 0 , antenna installation surface roll β m and pitch error angle A m .

[0111] d) Through the azimuth zero error A 0 , antenna installation surface roll β m and pitch error angle A m , the true posture H, P, R of the antenna installation surface can be calculated.

[0112] e) Use the real attitude to track the antenna and perform tracking. The entire correction process is continuous and iterative.

[0113] Using this method can greatly improve the tracking accuracy of the antenna.

[0114] The following is another embodiment:

[0115] like Figure 1 As shown, a method for dynamically correcting installation errors of airborne satellite communication antennas includes the following steps:

[0116] a) The antenna receives the correction command and tracks and maintains the satellite normally;

[0117] b) If Figure 2 As shown in the figure, the azimuth theoretical pointing angle and elevation theoretical pointing angle (A G0 、E G0 ) as the center, and the antenna pointing deviation is a° in the space area, forming a circular scanning path. The antenna scanning path is divided into four parts, ABCD. During each path scanning process, 25 beacon field strength values ​​are collected at equal intervals. Denoted as P A1 , P A2 ...P A25 , P B1 , P B2 ...P B25 , P C1 , P C2 ...P C25 , P D1 , P D2 ...P D25 , calculate the algebraic sum of the beacon strength received by each part P A , P B , P C , P D , then the field strength deviation of the antenna azimuth pointing to the beacon is ΔP 方位 =P A+D -P B+C , the field strength deviation of the beacon in the elevation direction is ΔP 俯仰 =P A+B -P C+D If ΔP 方位 >0, indicating that the antenna is off center to the right, so the azimuth pointing correction is required (A G0 -a / 20)°, the correction step (a / 20)° is 1 / 20 of the antenna half-power beam width. G0 +a / 20)°, if ΔP 俯仰 >0, indicating that the antenna deviates downward from the center, let (E G0 +a / 20)°, otherwise (E G0-a / 20)°, and then calculate the corrected azimuth frame control angle A according to equations (9) and (10). D1 and the pitch mount control angle E D1 . Continuously scan until ΔP 方位 , ΔP 俯仰 If it is close to 0 and changes between positive and negative, it means that the antenna is aligned with the satellite. At this time, solve the azimuth mount control angle deviation ΔA D and the pitch mount control angle deviation ΔE D ;

[0118] c) The antenna is constantly scanning the main surface and calculating ΔA during the tracking process D and ΔE D When the aircraft flies at different headings and attitudes, select 5 groups of ΔA D and ΔE D . They are denoted as ΔA D1 , ΔA D2 , ΔA D3 , ΔA D4 , ΔA D5 and ΔE D1 , ΔE D2 , ΔE D3 , ΔE D4 , ΔE D5 ;

[0119] d) According to the collected 5 sets of azimuth deviations and elevation deviations, the least square method is used to fit the error. The algebraic formula to be calculated is: 0 -β m sin(A c -A m )tanE c and -β m cos(A c -A m ), the principle of fitting solution is to minimize the sum of squares of deviations between fitting points and actual points, as follows:

[0120]

[0121]

[0122] Where:

[0123] A ci -The azimuth angle value of the i-th group of circular scans;

[0124] E ci -The pitch angle value of the i-th group of circular scans;

[0125] A Di - Azimuth correction value for the i-th group of circular scans;

[0126] E Di -The pitch correction value for the i-th group of circular scans;

[0127] The coefficient β can be obtained from the two fitting curves. m1 , β m2 , A m1 , A m2 , A 01 , A 02 ;

[0128] e) Maximum inclination of the mounting plate β m and the maximum tilt direction A m Conversion formula of rolling error ΔR and pitch error ΔP:

[0129] ΔP=sin -1 (sinβ m cosA m ) (13)

[0130] ΔR=tg -1 (-tgβ m sina m ) (14)

[0131] Two sets of ΔR can be obtained 1 , ΔR 2 ,ΔP 1 , ΔP 2 , if ΔR 1 , ΔR 2 Deviation greater than 0.2°, or ΔP 1 , ΔP 2 If the deviation is greater than 0.2°, the calculated value is considered to have a large deviation and low credibility, so it is discarded and the values ​​are taken, fitted, and ΔR and ΔP are solved again;

[0132] f) Assume the heading measured by the inertial navigation is H 0 , roll is R 0 , pitch is P 0 ,The roll and pitch errors of the inertial navigation and the antenna installation plane are ΔR,ΔP, and the true values ​​of the antenna installation plane are H,R,P.

[0133] H 0 ,R 0 ,P 0 Substitute the real attitude matrix of the antenna installation surface provided by the inertial navigation into the matrix, and we get

[0134] Where H = H 0 .

[0135] Substituting the roll and pitch errors ΔR and ΔP into the error matrix, we get

[0136]

[0137] The true posture matrix after error correction is:

[0138]

[0139] because Then we can solve P and R based on the principle that if two matrices are equal, their elements should be equal.

[0140] g) The zero position error A is obtained 0 Subtract it from the output angle of the azimuth encoder, use the error-corrected P and R, and solve the corrected control angle based on the conversion formula from pointing angle to antenna mount angle, i.e., formula (9) and formula (10), to achieve error correction tracking.

[0141] h) Based on the error correction tracking, this process can be continued to achieve correction iteration.

[0142] In summary, in view of the problem that the error between the mounting surface of the airborne satellite communication antenna and the mounting surface of the inertial navigation system in previous applications reduces the tracking accuracy of the airborne satellite communication antenna, the present invention proposes a method for dynamically correcting the installation error of the airborne satellite communication antenna. The method can correct the azimuth zero point error and attitude error between the mounting surface of the antenna and the mounting surface of the inertial navigation system, improve the tracking accuracy of the antenna, and can be continuously iterated.

Claims

1. A method for dynamically correcting installation errors of airborne satellite communication antennas, characterized in that: The following steps are involved: (1) The antenna tracks and maintains satellite tracking normally; the specific method is as follows: According to the longitude and latitude of the satellite and the antenna, calculate the theoretical azimuth and elevation pointing angles of the antenna to the satellite: Where: : The theoretical pointing angle of the antenna to the satellite; : The theoretical pointing angle of the antenna to the satellite; : Satellite longitude; : Satellite latitude, the latitude of synchronous orbit satellite is 0°; : aircraft longitude; : aircraft latitude; : The distance between the satellite and the center of the earth; : distance between the aircraft and the center of the earth; in accordance with and Track and maintain satellites; (2) Superimpose a radius of The circle of the antenna is realized by: Pointing angle based on azimuth theory , Pitch theoretical pointing angle As the center, set a pointing deviation of The new scanning path points to angle A. G , pitch pointing angle E G for: Among them, the scanning frequency is 1Hz, The value is 1 / 10 of the half-power beamwidth of the antenna; The new scanning path forms a spatial orientation of the antenna with ( , ) is a closed circle centered on The coordinate transformation from the antenna pointing angle to the antenna mount angle is realized through equations (9) and (10), thus realizing scanning control: In the formula, is the azimuth control angle of the antenna mount, is the antenna mount pitch control angle, is the geographical angle of the satellite azimuth, is the geographical angle of elevation of the star, , , They are the heading, roll and pitch of the aircraft respectively; (3) Collect the beacon receiving airport strength value during the antenna scanning process and calculate the field strength deviation in azimuth and elevation respectively; (4) Correcting the azimuth frame control angle and the pitch frame control angle according to the field strength deviation, and calculating the azimuth frame control angle deviation and the pitch frame control angle deviation; recording multiple sets of azimuth frame control angle deviations and pitch frame control angle deviations at different attitudes during the flight of the aircraft; (5) Fit the multiple sets of recorded azimuth mount control angle deviations and elevation mount control angle deviations based on the least squares method to obtain the error coefficients and calculate the azimuth zero position error, roll error, and pitch error of the antenna installation surface; (6) Calculate the true attitude of the antenna installation surface based on the heading, roll, and pitch values ​​provided by the inertial navigation system and the roll error and pitch error of the antenna installation surface obtained in step (5); use the true attitude and the azimuth zero position error obtained in step (5) to perform antenna tracking control; (7) During the tracking process, steps (1) to (6) are continuously executed and iterative correction is performed to achieve error convergence.

2. The method for dynamic correction of installation error of an airborne satellite communication antenna according to claim 1, characterized in that: The specific method of step (3) is: The antenna circular scanning path is divided into four parts: A, B, C, and D. During each path scanning process, 25 beacon field strength values ​​are collected at equal intervals and recorded as ; Take the algebraic sum of the beacon strengths received in each part and get , , , , then the field strength deviation of the antenna azimuth pointing to the beacon is , the field strength deviation of the beacon in the elevation direction is .

3. The method for dynamic correction of installation error of an airborne satellite communication antenna according to claim 2, characterized in that: The specific method of step (4) is: like , indicating that the antenna is off center to the right, so the azimuth pointing correction , otherwise the azimuth pointing correction ,like , indicating that the antenna deviates downward from the center, , otherwise ; According to equations (9) and (10), the corrected azimuth frame control angle is obtained: and pitch mount control angle ; Continue scanning until , If it is close to 0 and changes alternately between positive and negative, it means that the antenna is aligned with the satellite. At this time, solve the azimuth mount control angle deviation. and pitch mount control angle deviation ; When the aircraft flies at different headings and attitudes, select 5 groups and , respectively , , , , and , , , , .

4. The method for dynamic correction of installation error of an airborne satellite communication antenna according to claim 2, characterized in that: The specific method of step (5) is: The algebraic expression to be calculated is and The principle of fitting solution is to minimize the sum of squares of deviations between fitting points and actual points, as follows: （11） （12） Where: A0-azimuth zero position error of the antenna installation surface; -The azimuth angle value of the i-th group of circular scans; -The pitch angle value of the i-th group of circular scans; - Azimuth correction value for the i-th group of circular scans; -The pitch correction value for the i-th group of circular scans; Find the coefficients from the two fitting curves , , , , , ; Maximum tilt of the mounting plate and the direction of maximum tilt Roll Error , pitch error The conversion formula is: （13） （14） Thus, we can find two groups , ,if Deviation greater than 0.2°, or If the deviation is greater than 0.2°, the calculated value is considered to have a large deviation and low credibility, so it is discarded and the value is re-selected, fitted, and solved. , .

5. The method for dynamic correction of installation error of airborne satellite communication antenna according to claim 4, characterized in that: The specific method of step (6) is: Assume the heading measured by inertial navigation is , roll , pitch for ,Will , , Substitute the real attitude matrix of the antenna installation surface provided by the inertial navigation ,get: （15） in, ; Roll and pitch errors , Substituting into the error matrix, we get : （16） The true posture matrix after error correction is: （17） According to the relation , and the principle that if two matrices are equal, the elements should be equal, solve the true elevation of the antenna installation plane and real roll ; The zero position error obtained in step (5) is Subtract the error-corrected true elevation of the antenna mounting plane from the azimuth encoder output angle. and real roll , according to equations (9) and (10), the corrected control angle is solved to achieve error correction tracking.

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