A radar angle zero value calibration method without optical reference

Abstract

The present application relates to a kind of optical reference-free radar angle zero value calibration method, the method comprises the following:1, install 2 groups of GPS antennas on pitch fork arm sideband, utilize the straight line formed by the 2 points, with antenna axis forms associated relationship, and then link radar angle;2, using 4-way calibration method, with accurate north angle as reference, according to north, west, south, east, in the case of pitch 0, respectively, get positive and negative angle value;3, according to error correction formula, the positive and negative angle value is brought into calculation, and then average is obtained by using arithmetic average method to get azimuth, pitch zero position.The method uses temporarily installed 2 groups of GPS antennas to replace mechanical shaft, according to positive and negative unified pointing method, zero position is calibrated, after calibration, GPS antenna tooling can be removed and saved, there is no influence to the whole antenna structure, and angle calibration can be carried out at any time under unified time reference, has important practical significance.

Description

TECHNICAL FIELD

[0001] The present application relates to a radar angle zero value calibration method without optical reference. BACKGROUND

[0002] For the precision control radar used in the field of measurement and control, the angle zero value and the like need to be calibrated due to the precision requirement, the calibrated error parameters are brought into the error correction model for correction to obtain accurate tracking orbit parameters, and the calibration process is in-dock calibration. However, the radar tracks the target through the electric axis, and the electric axis is a virtual axis that cannot be seen or touched. In the past, a telescope was installed on the pitch arm to simulate the electric axis, through this substitution method, the azimuth mark for accurate positioning was aimed at by the telescope to calculate the angle zero value, and the accurate angle zero value was obtained through correction of the deviation between the calibrated telescope and the electric axis. However, there is no mature experience for the calibration of the radar without optical axis (without telescope), and there is no reliable and effective means for the calibration of the angle zero value.

[0003] The present application designs a radar angle zero value calibration method without optical reference, two groups of four GPS antennas are installed on two edges of the pitch arm, a virtual optical axis is simulated according to the idea that one straight line is formed by two points, the angle zero value can be obtained through simple calculation, and the self-calibration method provides a practical and simple method for solving the problem. SUMMARY

[0004] The present application provides a radar angle zero value calibration method without optical reference, adopts the GPS positioning method, simulates the space electric axis through the baseline between two GPSs, obtains the radar geodetic angle through coordinate transformation and angle calculation, calibrates according to the measured ship deviation north angle according to the four-way positive and negative calibration method, and calculates the angle zero value.

[0005] The technical scheme adopted by the present application to solve the above problems is as follows: a radar angle zero value calibration method without optical reference, the method is implemented as follows:

[0006] 1. Install GPS antennas on the pitch arm

[0007] Two thick edges (sidebands) perpendicular to the antenna elevation axis are used as the basis for GPS antenna installation, two GPS antennas are installed on each sideband, one sideband has one group, a total of two groups of four, and the GPS antenna independent tooling and elevation fork arm screw fixing method is adopted to ensure the structural strength and installation accuracy. The GPS antenna tooling is designed as a Z-shaped reinforcing structure, which is divided into upper edge, side edge, bottom edge and support edge. The upper edge is used to be fixed with the elevation fork arm thick edge through bolts, the bolt at the center position of the lower edge is used to fix the GPS antenna, the side edge is fixed with the elevation fork arm side piece through bolts, and the lower edge is supported with the side edge. By mechanical processing, the two groups of GPS are strictly symmetrical along the center line of the antenna fork arm, and the GPS antenna tooling and the elevation fork arm mounting surface accuracy are controlled. Under the condition of using the same batch of the same type of GPS antenna, this structure can not only ensure the strength, but also facilitate wiring and disassembly.

[0008] 2. Calibration method steps

[0009] The in-dock calibration is carried out in the dry dock. After the ship body is leveled, the entire ship body center line will have an angle with the true north, which is called the north deviation angle here and can be accurately calibrated. The present application uses this accurate north deviation angle as the azimuth reference, takes 0° as the elevation reference, and adopts a 4-way positive and negative positioning method to obtain the angle zero value. The so-called 4-way means that the radar points to the bow, the radar points to the port side, the radar points to the stern, and the radar points to the starboard, and the positive and negative measurements are carried out respectively (the positive direction is that the antenna points to the target in the positive direction, and the negative direction is that the antenna is flipped and then points to the target). Before calibration, the distance value D of the phase center points (antenna feed position) of the two groups of GPS antennas is obtained by geodetic surveying. It is known that the four directions refer to true north, true west, true south and true east. The specific method is that the antenna is positively rotated to point to true north, true west, true south and true east respectively, the current azimuth and elevation angles of the two GPS antenna baselines are calculated through GPS data, the antenna is rotated until the azimuth angle of the GPS antenna is 0°, 90°, 180° and 270° respectively, and the elevation angle is 0°, and the radar azimuth and elevation angle data are recorded; the antenna is reversed according to the positive rotation angle +180 and the elevation angle 180- the positive rotation angle, the antenna is rotated according to the azimuth and elevation angles, the azimuth angles are 0°, 90°, 180° and 270° respectively, and the elevation angles are all 180°, and the radar azimuth and elevation angle data are recorded; the data is processed by arithmetic average, and the azimuth and elevation zero positions are obtained.

[0010] 3. Calculation method

[0011] Firstly, the GPS measurement elements are processed to obtain three-dimensional coordinate values in the geocentric space rectangular coordinate system. In the three-dimensional coordinate system, the baseline azimuth and elevation angles of the two groups of GPS antennas are obtained according to the triangular relationship and the projection principle. After the data recording of step 2 is completed, the data is processed according to the calculation model, and the zero value is obtained after taking the arithmetic average of the results.

[0012] Preferably, by installing two sets of GPS antennas on the positive and negative sidebands of the pitch fork, the pointing angle of the line can be obtained under a unified coordinate system according to the theory that two points form a straight line, and this angle can be used as a comparison benchmark.

[0013] Preferably, the precisely calibrated north angle is used as the reference for antenna angle null correction, thereby reducing errors.

[0014] Preferably, a four-directional measurement method is used, with measurements taken in the directions of due north, due west, due south, and due east. The angle values ​​obtained through GPS data processing guide the antenna rotation, ensuring that the antenna points in the same direction whether it rotates forward or backward in any direction.

[0015] Preferably, the error correction model, particularly the zero-position formulas for each pointing direction (azimuth and pitch), is as follows:

[0016] A 0j =(A +i +A -i +180) / 2-β m sin(A +i -A m )tanE +i +A d

[0017] E 0j =(E +i +E -i -180) / 2+E d

[0018] Compared with the prior art, the advantages of the present invention are as follows:

[0019] (1) The method designed in this invention solves the problem of zero-angle calibration of radar equipment without optical axis.

[0020] (2) The method designed in this invention solves the problem of zero-value angle calibration anytime and anywhere. Attached Figure Description

[0021] Figure 1 This is a GPS installation diagram for the radar angle zero-value calibration method without optical reference of the present invention.

[0022] Figure 2 for Figure 1 GPS tooling diagram.

[0023] Figure 3 This is a schematic diagram illustrating the GPS elevation angle acquisition principle in the radar angle zero-value calibration method without optical reference of the present invention.

[0024] Figure 4This is a schematic diagram illustrating the principle of GPS azimuth acquisition in the radar angle zero-value calibration method without optical reference of the present invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0026] This invention relates to a method for calibrating the zero value of radar angles without optical reference. Its function is to use a theodolite as the ship's overall reference and employ a combined survey method to complete the calibration of individual differences in electrical equipment using geodetic survey results. The specific process is as follows:

[0027] 1. Mounting GPS antenna with a tilt fork arm

[0028] A pitch fork is a U-shaped steel structure, one on each side, used for power transmission and support of the entire reflector antenna structure. For example... Figure 1 and 2 As shown, two thick edges perpendicular to the antenna's pitch axis are used as the base for GPS antenna mounting. Considering the difficulty of processing and maintenance, a separate GPS fixture is used, which is then fixed to the thick edges of the pitch fork arm with screws. The GPS fixture is designed as a Z-shaped reinforced structure, consisting of a top, side, bottom, and support edge. The top edge has four mounting holes, corresponding to four screw holes drilled on the precision-machined mounting surface of the pitch fork arm, which are then assembled together. A bolt is installed at the center of the bottom edge to fix the GPS antenna, and the bottom edge and side edge form a diagonal brace. The side edge has mounting holes, corresponding to the holes drilled on the pitch fork arm, and then assembled. Because the GPS antenna is relatively light, this structure can ensure strength while also taking into account the advantages of wiring and easy disassembly. By controlling the machining accuracy of the GPS antenna fixture and the precision of the pitch fork arm's machined surface, and by selecting GPS antennas of the same type and batch to ensure phase center consistency, it is possible to ensure that the connection line between the two GPS antennas on the same side is perpendicular to the pitch axis and parallel to the mechanical axis. Meanwhile, through mechanical processing, it is ensured that the two sets of GPS antennas mounted on both sides of the fork arm maintain strict symmetry along the center line of the fork arm, and during installation, the baseline length of the GPS antenna on the same side is minimized to reduce pointing errors caused by installation.

[0029] 2. Calibration Methods and Steps

[0030] Dry dock calibration is conducted in a dry dock. After the hull is leveled, there will be an angle between the entire hull centerline and true north, which is called the north offset angle. This patent uses this precise north offset angle as the bearing reference, with 0° as the elevation reference. A four-directional forward and reverse positioning method is used to determine the zero angle value. The four directions refer to the radar pointing towards the bow, the port side, the stern, and the starboard side, respectively. Forward and reverse measurements are performed (the antenna is forward-pointing towards the target, and then the antenna is tilted back to point towards the target). Before calibration, the distance value D of the phase center points (antenna feed positions) of the two GPS antennas needs to be obtained by geodetic surveying. The specific method is as follows:

[0031] ① The radar azimuth is determined by the north angle α and the elevation is determined by turning the ship's bow direction at 0°. The azimuth and elevation angles are calculated using formulas (3) and (4). The antenna is rotated until the GPS baseline azimuth angle is 0° and the elevation angle is 0° or less than the minimum resolvable angle of the radar encoder. The radar angle data is then recorded.

[0032] ② The radar azimuth is set at 180 + north angle α, and the elevation is set at 180° to the bow direction. The azimuth and elevation angles are calculated using formulas (3) and (4). The antenna is rotated until the GPS baseline azimuth is 0° and the elevation angle is 0° or less than the minimum resolvable angle of the radar encoder. The radar angle data is then recorded.

[0033] ③ The radar azimuth is set at 90 + north angle α, and the elevation is set at 0° to the port side. The azimuth and elevation angles are calculated using formulas (3) and (4). The antenna is rotated until the GPS baseline azimuth is 90° and the elevation angle is 0° or less than the minimum resolvable angle of the radar encoder. The radar angle data is then recorded.

[0034] ④ The radar azimuth is set at 270 + north angle α, and the elevation is set at 180° to the port side. The azimuth and elevation angles are calculated using formulas (3) and (4). The antenna is rotated until the GPS baseline azimuth is 90° and the elevation angle is 0° or less than the minimum resolvable angle of the radar encoder. The radar angle data is then recorded.

[0035] ⑤ The radar azimuth is set at 180 + north angle α, and the elevation is set at 0° to the stern. The azimuth and elevation angles are calculated using formulas (3) and (4). The antenna is rotated until the GPS baseline azimuth is 180° and the elevation angle is 0° or less than the minimum resolvable angle of the radar encoder. The radar angle data is then recorded.

[0036] ⑥ The radar azimuth is determined by the north angle α and the elevation is determined by turning the stern direction by 180°. The azimuth and elevation angles are calculated using formulas (3) and (4). The antenna is rotated until the GPS baseline azimuth is 180° and the elevation angle is 0° or less than the minimum resolvable angle of the radar encoder. The radar angle data is then recorded.

[0037] ⑦ The radar azimuth is set at 270 + north angle α, and the elevation is set at 0° to the starboard direction. The azimuth and elevation angles are calculated using formulas (3) and (4). The antenna is rotated until the GPS baseline azimuth is 270° and the elevation angle is 0° or less than the minimum resolvable angle of the radar encoder. The radar angle data is then recorded.

[0038] ⑧ The radar azimuth is set at 180 + north angle α, and the elevation is set at 180° to the starboard direction. The azimuth and elevation angles are calculated using formulas (3) and (4). The antenna is rotated until the GPS baseline azimuth is 270° and the elevation angle is 0° or less than the minimum resolvable angle of the radar encoder. The radar angle data is then recorded.

[0039] ⑨ Calculate the zero values ​​of azimuth and elevation angles based on the recorded radar angles.

[0040] 3. Calculation method

[0041] ① Obtain angle values ​​by measuring elements using GPS

[0042] The longitude L, latitude B, and elevation H obtained from the GPS receiver are measurements in the geocentric geodetic coordinate system. They need to be converted to the geocentric rectangular coordinate system. The calculation formula is as follows:

[0043]

[0044] In the formula, N is the radius of curvature of the ellipsoid's prime meridian; e is the first eccentricity of the ellipsoid, which is calculated as follows:

[0045]

[0046] In the formula, a is the major radius of the ellipsoid; b is the minor radius of the ellipsoid.

[0047] Pitch value calculation: In a geocentric rectangular coordinate system, such as Figure 3 Based on trigonometric and projection relationships, the pitch value can be obtained using the following formula:

[0048] arctanE ±i =(X1-X2) / (Y1-Y2) (3)

[0049] In the formula, X1 is the X-axis coordinate of point B; X2 is the X-axis coordinate of point A; Y1 is the Y-axis coordinate of point B; Y2 is the Y-axis coordinate of point A; i is the point direction indicator, with positive direction represented by +1 to +4 and negative direction represented by -4 to -1.

[0050] Azimuth value calculation: In a geocentric rectangular coordinate system, such as Figure 4 Based on the trigonometric and projection relationships, the azimuth value can be obtained using the following formula:

[0051] arctanA ±i =(Z1-Z2) / (X1-X2) (4)

[0052] In the formula, X1 is the X-axis coordinate of point B; X2 is the X-axis coordinate of point A; Z1 is the Z-axis coordinate of point B; Z2 is the Z-axis coordinate of point A; E iis the pitch value corresponding to that point; i is the point orientation identifier, with +1 to +4 for positive orientation and -4 to -1 for negative orientation.

[0053] ② Zero-digit calculation mathematical model

[0054] The zero value for each direction is:

[0055] A 0j =(A +i +A -i +180) / 2-β m sin(A +i -A m )tanE +i +A d

[0056] Among them: A d =((X1-X2) 2 +(Z1-Z2) 2 ) 1 / 2 / D

[0057] The zero position is obtained by performing an arithmetic average on it:

[0058]

[0059] The pitch zero value for each direction is:

[0060] E 0j =(E +i +E -i -180) / 2+E d

[0061] Among them: E d =((X1-X2) 2 +(Y1-Y2) 2 ) 1 / 2 / D

[0062] The pitch zero position is obtained by performing an arithmetic average on it:

[0063]

[0064] In the formula, β m The largest tilt in the market, A m This represents the maximum tilt angle of the market.

[0065] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A method for calibrating the zero angle value of a radar without an optical reference, characterized in that: The method includes the following steps: 1) GPS antenna mounted on a tilt fork Two thick sides perpendicular to the antenna's pitch axis are used as the base for GPS antenna installation. Two GPS antennas are installed on each side strip, with one group on each side, for a total of two groups of four. 2) Calibration Methods and Steps Using the north-south angle as the azimuth reference and 0° as the elevation reference, a four-directional forward and reverse positioning method is employed to obtain the zero angle value. Forward and reverse measurements are performed separately. Before calibration, geodetic surveying is required to obtain the distance D between the phase center points of the two GPS antennas. The azimuth and elevation angles of the current two GPS antenna baselines are calculated using GPS data. The antennas are rotated until the azimuth angles are 0°, 90°, 180°, and 270°, and the elevation angle is 0°. The radar azimuth and elevation angle data are recorded. The antennas are then reversed with the azimuth angle being the forward rotation angle +180° and the elevation angle being 180° - the forward rotation angle. The antennas are rotated according to the GPS antenna azimuth and elevation angles. The radar's azimuth and elevation angles are 0°, 90°, 180°, and 270°, respectively, with an elevation angle of 180°. The radar's azimuth and elevation angle data are recorded. The azimuth and elevation zero points are obtained by performing arithmetic averaging on the data. The north-south angle refers to the angle between the centerline of the entire hull and true north after the hull has been leveled in the dry dock calibration. The four directions of the four-way forward and reverse positioning method are radar pointing towards the bow, radar pointing towards the port side, radar pointing towards the stern, and radar pointing towards the starboard side. Measurements are taken according to true north, true west, true south, and true east. The angle values ​​obtained by processing GPS data guide the antenna rotation, ensuring that the antenna points in the same direction in both forward and reverse rotations in all directions. 3) Zero value calibration method First, the GPS measurement elements are processed, and the three-dimensional coordinates in the geocentric rectangular coordinate system are obtained through coordinate transformation. In the three-dimensional coordinate system, the baseline azimuth and elevation angles of the two GPS antennas are obtained according to the trigonometric relationship and projection principle. After completing the data recording in step 2), the data is processed according to the calculation model, and the zero value is obtained by taking the arithmetic average of the results. The specific calculation process is as follows: ① Obtain angle values ​​by measuring elements using GPS The longitude L, latitude B, and elevation H obtained from the GPS receiver are measured values ​​in the geocentric geodetic coordinate system. They need to be converted to the geocentric rectangular coordinate system. The calculation formula is as follows: ; In the formula, N is the radius of curvature of the ellipsoid's prime meridian; e is the first eccentricity of the ellipsoid, which is calculated as follows: ; In the formula, a is the major radius of the ellipsoid; b is the minor radius of the ellipsoid. Pitch value calculation: In a geocentric rectangular coordinate system, the pitch value can be obtained based on trigonometric and projection relationships. The formula is as follows: ; In the formula, X1 is the X-axis coordinate of point B; X2 is the X-axis coordinate of point A; Y1 is the Y-axis coordinate of point B; Y2 is the Y-axis coordinate of point A; E ±i is the pitch value corresponding to this point; i is the point orientation identifier, with positive direction represented by +1 to +4 and negative direction represented by -4 to -1. Azimuth value calculation: In a geocentric rectangular coordinate system, the azimuth value can be obtained based on trigonometric and projection relationships. The formula is: ; In the formula, X1 is the X-axis coordinate of point B; X2 is the X-axis coordinate of point A; Z1 is the Z-axis coordinate of point B; Z2 is the Z-axis coordinate of point A; i is the point direction indicator, with positive direction represented by +1 to +4 and negative direction represented by -4 to -1; ② Zero-digit calculation mathematical model The zero value for each direction is: ; in: ; The zero position is obtained by performing an arithmetic average on it: ; The pitch zero value for each direction is: ; in: ; The pitch zero position is obtained by performing an arithmetic average on it: ; In the formula, β m The largest tilt in the market, A m This represents the maximum tilt angle of the market.

2. The radar angle zero-value calibration method without optical reference according to claim 1, characterized in that: In step 1), the GPS antenna fixture is designed as a Z-shaped reinforced structure, which is divided into an upper side, a side side, a bottom side, and a support side. The upper side is used to fix the thick side of the pitch fork arm with bolts. The bolt at the center of the lower side is used to fix the GPS antenna. The side side is fixed to the side plate of the pitch fork arm with bolts. The lower side and the side side are used for diagonal bracing.

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