Target pointing error calibration method of multimode composite tracking and pointing system

Abstract

A target pointing error calibration method of a multi-mode composite tracking and pointing system comprises the steps that (1) an autocollimator is erected right in front of a multi-mode optical system and a visible light camera view field, the multi-mode optical system is corrected, and the zero point of the visible light camera is marked; (2) placing a rake mark at the maximum measurement distance of the multimode optical system, and marking the position of the zero point of the camera in the rake mark; then, the azimuth axis and the pitch axis of the high-precision rotary table rotate to the zero position, the imaging position of a laser emitting laser point of the laser device is read, and the system deviation pointed by the target is recorded; (3) controlling an azimuth axis and a pitch axis of the high-precision turntable to swing to different angles, and measuring a deviation value of imaging positions of a tracking point of the visible light camera and a target laser irradiation point; and (4) the measured value is substituted into an error calculation formula containing the reflector installation deviation to form a multivariate equation set, the reflector installation error of the multimode composite tracking and pointing system is obtained through calculation, and the corresponding deviation value is calculated by combining the swing angles of the azimuth axis and the pitch axis of the high-precision rotary table. According to the method, the target pointing error of the multimode composite tracking and pointing system can be accurately calibrated.

Description

Technical Field

[0001] The invention belongs to the field of precision calibration of space tracking and aiming systems, and in particular relates to a calibration method for the direction of laser light transmitting and receiving paths and the deviation of a turntable in a space multi-mode composite tracking and aiming system. Background Art

[0002] Optoelectronic tracking and aiming technology has important applications in many fields such as communications and aerospace, and is an important part of establishing and maintaining laser communication links. The tracking and aiming performance of the optoelectronic tracking and aiming system directly affects the stability and reliability of optical communications. In the aerospace field, laser removal of "space junk" forms plasma, which has the advantages of thorough removal, low cost, and long-distance removal compared to other removal solutions.

[0003] In order to achieve the purpose of tracking and aiming, an optical path is usually built in the turntable, and the characteristic of the Coudé reflector that it can swing with the axis is used to achieve the consistency of the direction of the turntable and the laser light receiving and transmitting path. Figure 1 The figure shows the principle diagram of the laser output optical path of the multi-mode composite tracking and aiming system. Among them, the reflector 1 is installed at the laser output end and is fixedly connected to the laser output end; the reflector 2 is installed at the intersection of the azimuth axis and the elevation axis and is fixedly connected to the azimuth axis and rotates with the rotation of the azimuth axis; the multi-mode optical system is installed on the elevation axis and is fixedly connected to the elevation axis and moves with the rotation of the azimuth axis and the elevation axis; the reflector 3 is installed on the multi-mode optical system and is fixedly connected to the multi-mode optical system and also moves with the rotation of the azimuth axis and the elevation axis. After the laser is emitted by the laser and reflected by the reflector 1, it enters the azimuth axis. When the azimuth axis rotates, the laser light always remains parallel to the azimuth axis; after the laser light is reflected by the reflector 1, it enters the pitch axis. When the pitch axis rotates, the laser light always remains parallel to the pitch axis; after the laser light is reflected by the reflector 2, it is reflected by the reflector 3, parallel to the optical axis of the multi-mode optical system, and irradiates the target; after the laser light is scattered by the target, it is received by the laser detector in the multi-mode optical system to achieve distance measurement, and the visible light camera in the multi-mode optical system can measure the position of the target in the tracking and aiming system; when the target moves, the visible light camera feedback recognizes the change of the target position, and the tracking and aiming system controls the rotation of the azimuth axis and pitch axis of the high-precision turntable to ensure that the laser light still points to the target to achieve tracking and aiming. It can be seen from the working principle of the laser output optical path of the multi-mode composite tracking and aiming system that in order to ensure that the direction of the laser output light is consistent with the rotation of the two axes, the three reflectors need to maintain a specific angle and do not change during the working process. The three angles need to be achieved through adjustment.

[0004] Since the adjustment angle of the reflector deviates from the theoretical value, there will be a deviation between the turntable's swing angle and the laser's output optical path's direction. This deviation is related to the turntable's swing angle, that is, when the azimuth axis and the pitch axis swing to different angles, the deviation between the turntable's swing angle and the laser's output optical path's direction changes. In addition, there are stability issues with optical adjustment, that is, after the optical path is adjusted, stress release will occur, causing changes in accuracy; the reflector angle will also change under different temperature conditions; and the optical path accuracy will also change when experiencing a mechanical environment. Therefore, it is necessary to calibrate the laser emission optical path and the turntable's direction to reduce the pointing error of the tracking and aiming system caused by the optical adjustment. Figure 1 : is the angular deviation between the laser output light and the optical axis of the optical system.

[0005] The key issue in calibrating the accuracy of measuring instruments is how to find the variation law of errors to eliminate pointing errors and achieve higher tracking and aiming accuracy. Currently, there is no public calibration method for the pointing error of tracking and aiming systems. Summary of the invention

[0006] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art and provide a target pointing error calibration method for a multi-mode composite tracking and aiming system, obtain the relationship between the laser emission optical path and the turntable pointing deviation through theoretical modeling, and calibrate the error on this basis, and take the error into account in the tracking and aiming control process to reduce the tracking and aiming pointing error, thereby achieving the purpose of not losing the target.

[0007] The technical solution of the present invention is: a method for calibrating the target pointing error of a multi-mode composite tracking and aiming system, comprising the following steps:

[0008] (1) An autocollimator is set up in front of the multi-mode optical system and the visible light camera field of view, and the outer end surface of the secondary mirror of the multi-mode optical system is auto-collimated. The posture of the autocollimator is adjusted so that the image is reflected to the zero point of the autocollimator; then the visible light camera is powered on so that the crosshairs of the autocollimator are imaged in the visible light camera, and the position of the crosshairs in the camera measurement coordinate system at this time is recorded as the zero point of the visible light camera;

[0009] (2) Place a target at the maximum measurement distance of the multi-mode optical system, power on the visible light camera, image the target in the visible light camera, and mark the position of the zero point of the visible light camera in the target as (x0, y0); then, power on the high-precision turntable, rotate the azimuth and elevation axes of the high-precision turntable to (0°, 0°) and fix them; then, power on the laser, read the laser point imaging position (x0′, y0′) on the target, and record the system deviation of the target pointing at this time as e0=(x0′, y0′)-(x0, y0);

[0010] (3) Control the azimuth and elevation axes of the high-precision turntable to swing to different angles, and measure the deviation between the visible light camera tracking point (x, y) and the imaging position (x′, y′) of the target laser irradiation point;

[0011] (4) Substitute the measured value of step (3) into the formula e=A3-A3′ to form a multivariate equation group, and solve this multivariate equation group to obtain the reflector installation error of the multi-mode composite tracking and aiming system; calculate the corresponding deviation value according to the reflector installation error and the swing angles of the azimuth axis and the pitch axis of the high-precision turntable; wherein A3 is the direction vector of the laser emission beam vector when there is an adjustment error, and A3′ is the ideal direction vector of the laser emission beam.

[0012] Furthermore, the ideal direction vector A3′ of the emitted light beam of the laser is expressed as:

[0013]

[0014] in θ1 and θ2 are the azimuth axis rotation angle and the elevation axis rotation angle of the high-precision turntable respectively, α is the verticality error of the azimuth axis and the elevation axis, and R3 is the reflection matrix of the reflector 3 of the multi-mode composite tracking and aiming system.

[0015] Furthermore, the direction vector A3 of the laser's emission light beam vector when there is an adjustment error is expressed as A3=R3R2R1A0, wherein R2 and R1 are respectively the reflection matrix of the reflector 2 and the reflector 1 of the multi-mode composite tracking and aiming system, and A0 is the laser's output light vector.

[0016] Furthermore, the reflector reflection matrix of the multi-mode composite tracking and aiming system is:

[0017]

[0018] in is the normal vector of the mirror.

[0019] Furthermore, the normal vector transpose N' of the reflector is expressed as:

[0020]

[0021] Among them, d1, d2, and d3 are the heights of the three pads supporting the reflector. The three pads form an isosceles triangle with a height of b and a base length of a.

[0022] Furthermore, the normal vector N1 of the reflector 1, the normal vector N2 of the reflector 1, and the normal vector N3 of the reflector 3 are expressed as follows:

[0023]

[0024] The prime symbol in the upper right corner indicates vector transposition.

[0025] Furthermore, the azimuth axis and the elevation axis of the high-precision turntable are controlled to swing to different angles, the angle range is determined according to the use requirements of the multi-mode composite tracking and aiming system, and the swing angle positions are not less than 6.

[0026] Preferably, the azimuth axis and the pitch axis of the high-precision turntable are controlled to swing to different angles, the pitch angle swing angle range is -10 degrees to 50 degrees, and the azimuth axis swing angle range is -50 degrees to 50 degrees.

[0027] The advantages of the present invention compared with the prior art are:

[0028] (1) Based on the reflector installation method, the present invention uses the pad grinding amount as input to establish a theoretical model of target pointing error, based on which the calibration error can be minimized;

[0029] (2) The present invention separates the system error and the axis swing error, making the calibration process clear, reducing the calibration difficulty and improving the calibration efficiency;

[0030] (3) The present invention performs calibration based on the error existing in the adjustment of the Kude optical path, which can improve the tracking and aiming accuracy of the system, thereby reducing the difficulty of the Kude optical path adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the principle diagram of the laser emission optical path of the multi-mode composite tracking and aiming system;

[0032] Figure 2 This is a schematic diagram of the installation method of the reflector in the multi-mode composite tracking and aiming system;

[0033] Figure 3 This is the distribution size diagram of the reflector pad column;

[0034] Figure 4 It is a flowchart of the method of the present invention;

[0035] Figure 5 This is a schematic diagram of zero point calibration of a visible light camera of the present invention;

[0036] Figure 6 This is a schematic diagram of target pointing error calibration of the present invention. DETAILED DESCRIPTION

[0037] The method of the present invention firstly conducts theoretical modeling of the error and finds the variation law of the pointing error of the tracking and aiming system with the dual-axis swing. Figure 1The tracking and aiming system shown in the figure uses relevant instruments and equipment to build a calibration system, and uses the measured error points to solve the parameters in the theoretical model. Finally, the error value of the tracking and aiming subsystem is calculated based on the model.

[0038] First, establish Figure 1 Theoretical model of pointing error for the system shown.

[0039] Assume that the normal vector of a plane mirror is N, which can be expressed in the spatial coordinate system as:

[0040]

[0041] Then the reflection matrix R of the plane reflector can be expressed as

[0042]

[0043] Assume the outgoing light vector of the laser is A0, which can be expressed in the spatial coordinate system as:

[0044]

[0045] Then the laser light vector A3 reflected by three mirrors can be expressed as

[0046] A3=R3R2R1A0 (4)

[0047] Among them, parameters R1, R2, and R3 are the reflection action matrices of reflector 1, reflector 2, and reflector 3 respectively.

[0048] The reflector is installed as follows Figure 2 As shown, the reflector coordinate system is defined as: the origin is at the midpoint of the line connecting the centers of the cylindrical bases of pad pillars 1 and 2, the X-axis points from the center of the cylindrical base of pad pillar 2 to the center of the cylindrical base of pad pillar 1, the Y-axis is the height of the isosceles triangle formed by the three pad pillars, pointing from the origin to pad pillar 3, and the Z-axis, X-axis and Y-axis form a right-handed coordinate system.

[0049] Assume that the distance between the centers of the bases of the columns 1 and 2 is a, and the height of the isosceles triangle is b. Figure 3 As shown. Therefore, the spatial coordinates of the top surfaces of the three pads in the reflector coordinate system are DZ1 = (-a / 2, 0, d1) ′, DZ2 = (a / 2, 0, d2) ′, and DZ3 = (0, b, d3) ′. Among them, d1, d2, and d3 are the heights of the three pads, respectively. The upper right corner means transposition, which converts the row vector into a column vector.

[0050] The normal vector transposition of the reflector supported by three pads is N'=(DZ1-DZ3)×(DZ2-DZ3), where the multiplication sign means the vector product. The vector product of two vectors is a vector whose direction is perpendicular to the two vectors.

[0051] Substituting the coordinates into

[0052]

[0053] By converting N' to the global coordinate system, we can get the normal vector N of the reflector. The global coordinate system Oxyz is defined as Figure 1 shown.

[0054] The coordinate rotation matrix of a local coordinate along the x-axis to the global coordinate is defined as S i,θ , the coordinate rotation matrix of the angle θ along the y-axis to the global coordinate is defined as S j,θ , the coordinate rotation matrix of the angle θ along the z-axis to the global coordinate is defined as S k,θ , its matrix expression is:

[0055]

[0056] Assume that the reflector 2 swings at an angle θ1 along the azimuth axis; the reflector 3 swings at an angle θ1 along the azimuth axis and at an angle θ2 along the elevation axis; the verticality error between the azimuth axis and the elevation axis is α. Then, according to the installation relationship of the three reflectors, the normal vectors of the reflectors in the global coordinates are

[0057]

[0058] Among them, the subscripts 1, 2, and 3 correspond to reflectors 1, 2, and 3. It should be noted that the angles of the subscripts of the coordinate rotation matrices in formulas (7), (8), and (9) are related to the spatial positional relationship between reflectors 1, 2, and 3. This is the angle selected in the example of the present invention. The conversion matrix in other examples needs to be modified according to the installation angle of the reflector. The principle is the aforementioned vector coordinate system transformation.

[0059] Substituting equations (1) to (3) and (5) to (9) into equation (4), we can obtain the expression A3 when there is an adjustment error in the laser beam vector; and the ideal direction vector expression of the laser beam is:

[0060]

[0061] Therefore, the expression of the theoretical model of the deviation between the laser emission beam and the biaxial swing angle is:

[0062] e=A3-A3′ (11)

[0063] The input variables are the verticality error α of the azimuth axis and the elevation axis (for a certain high-precision turntable, this error is constant and can be measured, and is a constant for the tracking system), the azimuth axis swing angle θ1, and the elevation axis swing angle θ2. The parameters that need to be determined by calibration are the height differences of the pads of reflector 1, reflector 2, and reflector 3, a total of 6 (2 for each reflector, corresponding to the height differences d1-d3, d2-d3 in the last line of equation (5)).

[0064] like Figure 4 As shown, the calibration process of the method of the present invention is as follows:

[0065] ①Calibration preparation.

[0066] Tools and equipment required: autocollimator and its accessories; goggles.

[0067] ② Zero point calibration of visible light camera.

[0068] like Figure 5 As shown, first, the autocollimator is set up in front of the multi-mode optical system and the visible light camera field of view, the outer end face of the secondary mirror of the multi-mode optical system is self-collimated, and the posture of the autocollimator is adjusted to make the image return to the zero point of the autocollimator; then, the visible light camera is turned on and powered on to make the crosshairs of the autocollimator form an image in the visible light camera, and the position of the crosshairs in the camera measurement coordinate system at this time is recorded. This position is the zero point of the visible light camera.

[0069] ③ Target pointing system error calibration.

[0070] The target pointing error is divided into two parts. One part is the system error formed after the reflector 3 is installed and adjusted. It is a fixed value and is represented by e0. The other part is the axis swing error and is represented by e.

[0071] like Figure 6 As shown, firstly, a target mark is placed at the maximum measuring distance of the multi-mode optical system, and the visible light camera is powered. The target mark is imaged in the visible light camera, and the position of the camera zero point in the target mark is marked, and the position coordinates are (x0, y0).

[0072] Then, the high-precision turntable is powered on, and the azimuth and elevation axes of the high-precision turntable are rotated to (0°, 0°) and fixed; then, the laser is powered on, and the laser point imaging position (x0′, y0′) is read on the target mark. At this time, the system deviation of the target pointing is

[0073] e0=(x0′,y0′)-(x0,y0) (12)

[0074] ④ Calibration of laser pointing with-axis swing error. The with-axis swing error e changes with the dual-axis swing angle, that is, e is a function of the azimuth axis swing angle θ1 and the elevation axis swing angle θ2. e is a comprehensive error, including the system error e0.

[0075] Control the azimuth and elevation axes to swing to different angles, as shown in Table 1. The angle range is determined according to the tracking and aiming system requirements, and the number of points is no less than 6. Measure the deviation between the visible light camera tracking point (x, y) and the imaging position (x′, y′) of the target laser irradiation point.

[0076] Table 1 Laser pointing with two-axis swing angle record

[0077]

[0078] ⑤Parameter calculation.

[0079] Based on the recorded values ​​in step ④, substitute them into equation (11) to form a multivariate equation system, and solve this multivariate equation system. The known variables of this equation system are the values ​​recorded in Table 1, and the unknown variables are the height differences in equation (5). By solving the equation system (for example, using MATLAB to write a program for calculation), the height differences of the columns of reflector 1, reflector 2, and reflector 3 are calculated, a total of 6 parameters.

[0080] ⑥Error calculation.

[0081] Substituting the six parameters solved in step ⑤ into equation (11), setting the azimuth axis swing angle θ1 and the pitch axis swing angle θ2 to different angles, the corresponding deviation value can be calculated as the input of the target pointing control system software.

[0082] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for calibrating target pointing error of a multi-mode composite tracking and aiming system, characterized by: The steps include: (1) An autocollimator is set up in front of the multi-mode optical system and the visible light camera field of view, and the outer end surface of the secondary mirror of the multi-mode optical system is auto-collimated. The posture of the autocollimator is adjusted so that the image is reflected to the zero point of the autocollimator; then the visible light camera is powered on so that the crosshairs of the autocollimator are imaged in the visible light camera, and the position of the crosshairs in the camera measurement coordinate system at this time is recorded as the zero point of the visible light camera; (2) Place a target at the maximum measurement distance of the multi-mode optical system, power on the visible light camera, image the target in the visible light camera, and mark the position of the zero point of the visible light camera in the target as (x0, y0); then, power on the high-precision turntable, rotate the azimuth and elevation axes of the high-precision turntable to (0°, 0°) and fix them; then, power on the laser, read the laser point imaging position (x0′, y0′) on the target, and record the system deviation of the target pointing at this time as e0=(x0′, y0′)-(x0, y0); (3) Control the azimuth and elevation axes of the high-precision turntable to swing to different angles, and measure the deviation between the visible light camera tracking point (x, y) and the imaging position (x′, y′) of the target laser irradiation point; (4) Substitute the measured value of step (3) into the formula e=A3-A3′ to form a multivariate equation group, and solve this multivariate equation group to obtain the reflector installation error of the multi-mode composite tracking and aiming system; calculate the corresponding deviation value according to the reflector installation error and the swing angles of the azimuth axis and the pitch axis of the high-precision turntable; wherein A3 is the direction vector of the laser emission beam vector when there is an adjustment error, and A3′ is the ideal direction vector of the laser emission beam.

2. The target pointing error calibration method of a multi-mode composite tracking and aiming system according to claim 1 is characterized by: The ideal direction vector A3′ of the emitted light beam of the laser is expressed as: in θ1 and θ2 are the azimuth axis rotation angle and the elevation axis rotation angle of the high-precision turntable respectively, α is the verticality error of the azimuth axis and the elevation axis, and R3 is the reflection matrix of the reflector 3 of the multi-mode composite tracking and aiming system.

3. The target pointing error calibration method of a multi-mode composite tracking and aiming system according to claim 2 is characterized by: The direction vector A3 of the laser emission beam vector when there is an adjustment error is expressed as A3=R3R2R1A0, wherein R2 and R1 are respectively the reflection matrix of the reflector 2 and the reflector 1 of the multi-mode composite tracking and aiming system, and A0 is the output light vector of the laser.

4. The target pointing error calibration method of a multi-mode composite tracking and aiming system according to claim 2 or 3, characterized in that: The reflector reflection matrix of the multi-mode composite tracking and aiming system is: in is the normal vector of the mirror.

5. The target pointing error calibration method of a multi-mode composite tracking and aiming system according to claim 4 is characterized by: The normal vector transpose N' of the reflector is expressed as: Among them, d1, d2, and d3 are the heights of the three pads supporting the reflector. The three pads form an isosceles triangle with a height of b and a base length of a.

6. The target pointing error calibration method of a multi-mode composite tracking and aiming system according to claim 5 is characterized by: The normal vector N1 of the reflector 1, the normal vector N2 of the reflector 1, and the normal vector N3 of the reflector 3 are expressed as follows: The prime symbol in the upper right corner indicates vector transposition.

7. The target pointing error calibration method of a multi-mode composite tracking and aiming system according to claim 1 is characterized by: The azimuth axis and the elevation axis of the high-precision turntable are controlled to swing to different angles, the angle range is determined according to the use requirements of the multi-mode composite tracking and aiming system, and the swing angle positions are not less than 6.

8. The target pointing error calibration method of a multi-mode composite tracking and aiming system according to claim 1 is characterized by: The azimuth axis and the pitch axis of the high-precision turntable are controlled to swing to different angles, the pitch angle swing angle range is -10 degrees to 50 degrees, and the azimuth axis swing angle range is -50 degrees to 50 degrees.

9. A computer system comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method of claim 1.

10. A computer program product, comprising a computer program, characterized in that When the computer program instructions are executed by a processor, the steps of the method according to claim 1 are implemented.

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