An optoelectronic calibration method for shipborne measurement and control antennas

Abstract

The present invention discloses an optoelectronic calibration method for shipborne measurement and control antennas, belonging to the technical field of antenna calibration. The present invention tracks different stars, records the target miss distance, and according to the recorded data, fits the error quantity in the error model by the least square method; for azimuth, it can determine the azimuth zero point, the non-level of the turntable, the non-orthogonality of the azimuth and elevation axes, and the non-orthogonality of the optical axis and the elevation axis; for elevation, it can determine the elevation zero point and the non-level value of the turntable. At the same time, through the error analysis of tracking dynamic targets, reverse correction is performed on some variable parameters such as random error and systematic error in the parameter model.

Description

Technical Field

[0001] The present invention relates to the technical field of antenna calibration, and in particular to an optoelectronic calibration method for shipborne measurement and control antennas, which can be used for star calibration of low-light-level television for measurement and control antennas. Background Art

[0002] After the antenna is installed on the ship and the ship is docked at the wharf, the attitude of the hull will change slowly with the water flow and tide. Therefore, when calibrating the antenna axis error by tracking stars with a low-light-level television, it is different from that of a fixed station. After exploration, a set of calibration processes and algorithms have been determined, and the test results are good. After the earth calibration of the fixed station measurement and control antenna, the calibration parameters are fixed after the orthogonality calibration of the azimuth and elevation axes, the optoelectronic consistency calibration, and the optomechanical consistency calibration. For shipborne measurement and control antennas, after earth calibration, optoelectronic calibration needs to be carried out on the ship through a low-light-level television to adjust the calibration parameters.

[0003] Deficiencies existing in shipborne antennas only through earth calibration:

[0004] 1) Earth calibration does not consider the influence of the hull attitude, water flow, and tide;

[0005] 2) Earth calibration does not calculate the influence of the deformation of the equipment over time on the tracking accuracy. Summary of the Invention

[0006] Aiming at the problem that the calibration of shipborne measurement and control antennas in the prior art is affected by the change of the carrier attitude and the deformation of the equipment, the present invention provides an optoelectronic calibration method for shipborne measurement and control antennas, which has a high calibration accuracy.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] An optoelectronic calibration method for shipborne measurement and control antennas includes the following steps:

[0009] Step 1, the low-light-level television star calibration system calculates the current star chart according to the equipment site address and time, and selects multiple stars as calibration stars;

[0010] Step 2, the low-light-level television star calibration system calculates the geographical pointing angle of the calibration star and sends it to the servo system;

[0011] Step 3, the servo system calculates the deck pointing angle of the calibration star according to the geographical pointing angle sent by the low-light-level television star calibration system and collects the carrier attitude data sent by the inertial navigation system;

[0012] Step 4, the servo system controls the antenna to point to the calibration star according to the calculated deck pointing angle, reads and records the target miss distance in the low-light-level television tracking interface;

[0013] Step 5: Track and record each calibration star in sequence. If cloud occlusion or double-star phenomenon occurs, select a substitute star at a nearby position and perform Steps 2 to 4 on the substitute star;

[0014] Step 6: Establish an error correction model. According to the actually tracked azimuth mount angle A c , the actually tracked elevation mount angle E c , the azimuth measurement value A T , and the elevation measurement value E T , fit the undetermined parameters in the error correction model by the least squares method;

[0015] Step 7: Calculate the deviation between the angle measurement value and the actually tracked mount angle during tracking, i.e., A T - A c , E T - E c , and calculate the standard deviation of the two deviations during tracking respectively to determine the model deviation parameter; minimize the deviation by supplementing the optoelectronic deviation and gravity deformation to obtain the undetermined parameters of the corrected error correction model;

[0016] Complete the optoelectronic calibration of the TT&C antenna.

[0017] Furthermore, the error correction model in Step 6 is expressed as:

[0018] ΔA = A0 + θ m ·sin(A c - A m )·tanE c + δ·tanE c + (K z + K g + ΔU a / C a )·secE c

[0019] In the formula, ΔA is the azimuth deviation correction amount, A0 is the antenna azimuth zero-value error, A c is the actually tracked azimuth mount angle, E c is the actually tracked elevation mount angle, A m is the error correction parameter, K z is the horizontal deviation between the electrical axis and the optical axis, K g is the horizontal deviation between the optical axis and the elevation axis, C a is the directional sensitivity coefficient, ΔU a is the error voltage, δ is the non-orthogonality of the azimuth axis and the elevation axis, θ m is the maximum non-levelness of the large disk;

[0020] Rewrite the expression of the above error correction model as follows:

[0021] θ m ·sin(A c -A m )·tanE c =θ m ·(sinA c ·cosA m -cosA c ·sinA m )·tanE c

[0022] Define the lateral deviation C3, where the left height is positive: C3 = -θ m ·sinA m

[0023] Define the longitudinal deviation C4, where the front height is positive: C4 = θ m ·cosA m

[0024] Define the misalignment error K of the electric axis: K = K z +K g

[0025] In addition, since θ m is always negative, we have:

[0026] θ m ·sin(A c -A m )·tanE c =C3·cosA c ·tanE c +C4·sinA c ·tanE c

[0027] During electric calibration fitting, substitute (ΔU a / C a )·secE c as a known quantity. Finally, the error correction model for dynamic lag substitution is obtained as:

[0028] ΔA = A0 + C3·cosA c ·tanE c +C4·sinA c ·tanE c +δ·tanE c +K·secE c +(ΔU a / C a )·secE c

[0029] where the directional sensitivity coefficient C aIt is a calibration project before the mission and does not require fitting;

[0030] In the low-light optical pointing fitting, K becomes K g , during the low-light TV calibration, optical tracking is not performed, but the deviation value is directly read after pointing. Therefore, the dynamic lag term (ΔU a / C a )·secE c is removed. The error correction model without the dynamic lag term is expressed as ΔA’, and the following formula is obtained:

[0031] ΔA’ = A0 + C3·cosA c ·tanE c + C4·sinA c ·tanE c + δ·tanE c + K g ·secE c

[0032] Perform least squares fitting on A0, C3, C4, δ, Kg. The specific method is as follows: According to the recorded multiple azimuth miss distances A ej , elevation miss distances E ej , azimuth deck angles A j , elevation deck angles E j , azimuth guidance angles LA j , elevation guidance angles LE j , make the error value minimum according to the error correction model without the dynamic lag term. Obtain the model parameters through least squares curve fitting, and take partial derivatives of A0, C3, C4, δ, Kg respectively to get a = (A T A) -1 A T L. The definitions of a, A, and L are as follows:

[0033]

[0034] where the subscript j represents the j-th recorded value.

[0035] Furthermore, the number of stars selected as calibration stars in step 1 is 36.

[0036] Furthermore, in step 7, in order to further verify the fitting result, calculate the azimuth and elevation deviation standard deviations of the target tracking, or fix several quantities and perform fitting on other quantities, observe the deviation changes, and finally determine the deviation parameters and supplement the optoelectronic deviation and gravity deformation to minimize the error of the model.

[0037] The present invention has the following advantages:

[0038] 1. On-site calibration is easy to operate.

[0039] 2. High precision. After the optoelectronic calibration is completed, it can work with high precision within the range of plus or minus 7 degrees of the carrier's roll change.

[0040] 3. The present invention can be calibrated under dynamic conditions without the need for the ship to dock.

[0041] 4. The present invention has relatively low requirements for the calibration environment and does not require the cooperation of a professional calibration tower. Description of the Drawings

[0042] Figure 1 is a flowchart of the optoelectronic calibration method for shipborne measurement and control antennas in an embodiment of the present invention.

[0043] Figure 2 is a deviation value curve graph of the actual azimuth value and the theoretical value after azimuth reverse correction.

[0044] Figure 3 is a deviation value curve graph of the actual pitch value and the theoretical value after pitch reverse correction. Detailed Embodiment

[0045] Geodetic calibration is the basis for the star calibration of low-light-level television. Geodetic calibration accurately calibrates all error terms, which can ensure that the error of each axis system is within a certain accuracy; low-light-level television calibration can calibrate all other axis system errors except for optoelectronic deviation and gravity sag. The low-light-level television calibration is essentially data fitting calibration, and the calibrated error terms no longer have strict physical meanings, but only variable values in the error model. Aiming at the low tracking accuracy of the measurement and control antenna caused by factors such as non-orthogonality of the optoelectronic axes and non-leveling of the large turntable, an optoelectronic calibration method for shipborne measurement and control antennas is proposed.

[0046] The principle of this method is as follows:

[0047] By tracking different stars, recording the target miss distance, and according to the recorded data, the error quantities in the error model are fitted by the least square method. For azimuth, the azimuth zero point, non-leveling of the large turntable, non-orthogonality of the azimuth and pitch axes, and non-orthogonality of the optical axis and the pitch axis can be determined; for pitch, the pitch zero point and the non-leveling value of the large turntable can be determined. At the same time, through the error analysis of tracking dynamic targets, including random errors and systematic errors, some variable parameters in the parameter model are reversely corrected.

[0048] The steps of this method are as follows:

[0049] 1) The low-light-level television star calibration system calculates the current star chart according to the equipment site and time, and automatically or manually selects 36 stars as calibration stars.

[0050] 2) The low-light-level television star calibration system calculates the geographical pointing angle of the current star one by one and sends it to the servo equipment;

[0051] 3) The servo system calculates the stellar deck pointing angle based on the stellar geographic pointing angle sent by the low-light TV star calibration system and collects the carrier attitude data sent by the inertial navigation system; the star is the calibration star.

[0052] 4) The servo system controls the antenna to point to the star according to the calculated stellar deck pointing angle, reads the target miss distance in the low-light TV tracking interface, and records the data.

[0053] 5) Track and record 36 stellar sources in sequence. If cloud occlusion or double-star phenomenon occurs, an alternative star can be selected at a nearby position.

[0054] 6) According to the recorded data, fit the error quantities A0, C3, C4, δ, Kg in the error model (1) by the least squares method:

[0055] ΔA = A0 + θ m ·sin(A c -A m )·tanE c +δ·tanE c +(K z +K g +ΔU a / C a )·secE c (1)

[0056] Where, ΔA is the azimuth deviation correction amount, A0 is the antenna azimuth zero value error, A c is the azimuth mount angle of the actual tracking, E c is the elevation mount angle of the actual tracking, A m is the error correction parameter, K z is the horizontal deviation between the electrical axis and the optical axis, K g is the horizontal deviation between the optical axis and the elevation axis, C a is the directional sensitivity coefficient, ΔU a is the error voltage, δ is the non-orthogonality of the azimuth axis and the elevation axis, θ m is the maximum non-levelness of the large plate.

[0057] Among them, Kz + Kg can be combined into K, that is, the misalignment error of the electrical axis; that is, the horizontal deviation between the electrical axis and the optical axis + the horizontal deviation between the optical axis and the elevation axis = the horizontal deviation between the electrical axis and the elevation axis.

[0058] Rewrite the model as:

[0059] θ m ·sin(A c -A m )·tanE c =θ m ·(sinA c ·cosAm -cosA c ·sinA m )tanE c (2)

[0060] Let:

[0061] C3 = -θ m ·sinA m Defined as the lateral deviation (positive for higher on the left)

[0062] C4 = θ m ·cos A m Defined as the longitudinal deviation (positive for higher in the front)

[0063] From the definition of θ m it can be seen that it is always negative; thus:

[0064] θ m ·sin(A c -A m )·tanE c = C3·cosA c ·tanE c + C4·sinA c ·tanE c

[0065] Therefore, the azimuth error correction model can be rewritten as:

[0066] ΔA = A0 + C3·cosA c ·tanE c + C4·sinA c ·tanE c + δ·tanE c +(K z + K g + ΔU a / C a )·secE c (3)

[0067] Since the directional sensitivity coefficients C a 、C e are calibration items that must be carried out before the mission, these two coefficients do not need to be fitted. When performing electrical calibration fitting, (ΔU a / C a )·secE c is substituted as a known quantity. Finally, the error correction model with dynamic lag substitution is expressed as:

[0068] ΔA = A0 + C3·cosA c ·tanE c + C4·sinA c·tanE c +δ·tanE c +K·secE c +(ΔU a / C a )·secE c (4)

[0069] The directional sensitivity coefficient C a is a calibration item that must be carried out before the mission, so these two coefficients do not need to be fitted.

[0070] When performing low-light optical pointing fitting, K becomes K g . During low-light TV calibration, instead of performing optical tracking, the deviation value is directly read after pointing, so the dynamic lag term (ΔU a / C a )·secE c is removed to obtain the error correction model without dynamic lag substitution, denoted as ΔA’, and the following equation is obtained:

[0071] ΔA’ = A0 + C3·cosA c ·tanE c + C4·sinA c ·tanE c + δ·tanE c + K g ·secE c (5)

[0072] 7) After the calculation, data such as the deviation standard deviation of target tracking can be obtained. It is also possible to fix several quantities and perform fitting or trials on other quantities to observe the deviation changes. Finally, determine the deviation parameters and supplement parameters such as optoelectronic deviation and gravity deformation to obtain the complete error correction model parameters.

[0073] The following is a more specific example:

[0074] Refer to Figure 1 , a shipborne measurement and control antenna optoelectronic calibration method, including the following steps:

[0075] 1) Select a clear night weather to ensure that the inertial navigation and low-light TV are working properly, and manually select 36 stars through the low-light TV;

[0076] 2) The measurement and control antenna tracks 36 stars respectively. After guiding in place, record the azimuth guiding angle LA j , the elevation guiding angle LE j . Adjust the azimuth axis and elevation axis of the antenna to ensure that the azimuth miss distance A ej , the elevation miss distance E ej is minimized, and record the azimuth miss distance A ej , the elevation miss distance E ej, Azimuth deck angle A j , Elevation deck angle E j ; j is the star serial number;

[0077] 3) According to the record of 36 azimuth miss distances A ej , elevation miss distance E ej , azimuth deck angle A j , elevation deck angle E j , azimuth guidance angle LA j , elevation guidance angle LE j , make the error value minimum according to the error model formula (5), obtain the model parameters through least squares curve fitting, and take partial derivatives of A0, C3, C4, δ, Kg respectively to get a = (A T A) -1 A T L:

[0078]

[0079] In summary, the present invention tracks different stars, records the target miss distance, and fits the error quantity in the error model through least squares according to the recorded data; for azimuth, it can determine the azimuth zero point, the non - level of the turntable, the non - orthogonality of the azimuth and elevation axes, and the non - orthogonality of the optical axis and the elevation axis; for elevation, it can determine the elevation zero point and the non - level value of the turntable. At the same time, through the error analysis of tracking dynamic targets, the variable parameters such as random error and systematic error in the parameter model are corrected inversely.

Claims

1. A method for optoelectronic calibration of shipborne measurement and control antennas, characterized in that, It includes the following steps: Step 1: The low-light TV star calibration system calculates the current star chart based on the equipment station address and time, and selects multiple stars as calibration stars; Step 2: The low-light TV star calibration system calculates the geographical pointing angle of the calibration stars and sends it to the servo system; Step 3: The servo system calculates the deck pointing angle of the calibration stars according to the geographical pointing angle sent by the low-light TV star calibration system and collects the carrier attitude data sent by the inertial navigation system; Step 4: The servo system controls the antenna to point to the calibration stars according to the calculated deck pointing angle, reads and records the target miss distance in the low-light TV tracking interface; Step 5: Track and record each calibration star in turn. If cloud occlusion or double-star phenomenon occurs, select a substitute star at a nearby position and perform Steps 2 to 4 on the substitute star; Step 6, establish an error correction model. According to the recorded actual tracked azimuth pedestal angle A c , the actual tracked elevation pedestal angle E c , the measured azimuth angle A T , and the measured elevation angle E T , fit the undetermined parameters in the error correction model by the least squares method; Step 7, calculate the deviation A between the angle measurement value and the actual tracking mount angle during the tracking process T -A c , E T -E c , and calculate the standard deviations of the two deviations during the tracking process respectively, determine the model deviation parameters; make the deviation minimum by supplementing the optoelectronic deviation and the gravity deformation, and obtain the undetermined parameters of the error correction model after anti-repair Complete the optoelectronic calibration of the tracking and control antenna.

2. The optoelectronic calibration method for shipborne measurement and control antennas according to claim 1, wherein The error correction model in Step 6 is expressed as: ΔA = A0 + θ m ·sin(A c -A m )·tanE c +δ·tanE c +(K z +K g +ΔU a / C a )·secE c Wherein, ΔA is the azimuth deviation correction amount, A0 is the zero value error of the antenna azimuth angle, A c is the azimuth pedestal angle of actual tracking, E c is the elevation pedestal angle of actual tracking, A m is the error correction parameter, K z is the horizontal deviation between the electrical axis and the optical axis, K g is the horizontal deviation between the optical axis and the elevation axis, C a is the directional sensitivity coefficient, ΔU a is the error voltage, δ is the non-orthogonality of the azimuth axis and the elevation axis, θ m is the maximum non-levelness of the large plate; The expression of the above error correction model is rewritten as follows: θ m ·sin(A c -A m )·tanE c =θ m ·(sinA c ·cosA m -cosA c ·sinA m )·tanE c Define the lateral deviation C3, where the left height is positive: C3 = -θ m ·sinA m Define the longitudinal deviation C4, where the front height is positive: C4 = θ m ·cosA m Define the misalignment error K of the electrical axis: K = K z + K g In addition, since θ m is always negative, we have: θ m ·sin(A c -A m )·tanE c = C3·cosA c ·tanE c + C4·sinA c ·tanE c When performing electrical calibration fitting, (ΔU a / C a )·secE c is substituted as a known quantity. Finally, the error correction model with dynamic lag substitution is obtained and expressed as: ΔA = A0 + C3·cosA c ·tanE c + C4·sinA c ·tanE c + δ·tanE c + K·secE c +(ΔU a / C a )·secE c Among them, the directional sensitivity coefficient C a is a calibration item before the task and does not require fitting; In the low-light optical pointing fitting, K becomes K g , during the low-light TV calibration, instead of performing optical tracking, the deviation value is directly read after pointing. Therefore, the dynamic lag term (ΔU a / C a )·secE c is removed. The error correction model without the dynamic lag term substitution is denoted as ΔA’, and the following equation is obtained: ΔA’ = A0 + C3·cosA c ·tanE c + C4·sinA c ·tanE c + δ·tanE c + K g ·secE c Perform least squares fitting on A0, C3, C4, δ, and Kg. The specific method is as follows: According to the recorded multiple azimuth miss distances A ej , elevation miss distances E ej , azimuth deck angles A j , elevation deck angles E j , azimuth guidance angles LA j , elevation guidance angles LE j , make the error value minimum according to the error correction model without dynamic lag substitution, obtain the model parameters through least squares curve fitting, take partial derivatives of A0, C3, C4, δ, and Kg respectively, and get a = (A T A) -1 A T L. The definitions of a, A, and L are as follows: Where the subscript j represents the recorded value of the jth time.

3. A method for photoelectric calibration of a shipborne measurement and control antenna according to claim 1, characterized in that, The number of stars selected as calibration stars in Step 1 is 36.

4. The optoelectronic calibration method for shipborne measurement and control antennas according to claim 1, characterized in that, Step 7: In order to further verify the fitting result, calculate the standard deviation of the azimuth and elevation deviations of the target tracking, or fix several quantities and perform fitting on other quantities, observe the deviation changes, and finally determine the deviation parameters and then supplement the optoelectronic deviation and gravity deformation to minimize the error of the model.

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