General method and device for optical axis correction of airborne optical equipment

Abstract

The application provides a general method and device for correcting the optical axis of an airborne optical device, which comprises the following steps: setting a total station at a first station, measuring the coordinates of N reference points and two auxiliary measurement points in the total station coordinate system; setting the total station at a second station according to the coordinates of the two auxiliary measurement points in the total station coordinate system, the coordinates of the two auxiliary measurement points measured by the total station at the second station being the same as the coordinates measured at the first station; measuring the coordinates of M reference points in the total station coordinate system by the total station at the second station; M and N are positive integers, and the sum L of M and N is not less than 6; the L reference points are not repeated; obtaining a coordinate conversion formula according to the coordinates of the L reference points in the total station coordinate system and in the aircraft coordinate system; obtaining the coordinates of a target point in the total station coordinate system according to the theoretical coordinates of the target point in the aircraft coordinate system and the coordinate conversion formula; placing the target point according to the coordinates of the target point in the total station coordinate system; and correcting the on-board axis of the airborne optical device according to the placed target point. The method can greatly improve the correction accuracy, is suitable for any type of aircraft and airborne optical device, and has good universality. Since the aircraft leveling process is not needed, the method obviously saves manpower and material resources and greatly improves the work efficiency of the ground crew.

Description

Technical Field

[0001] This invention relates to the field of rigid body motion theory and coordinate system transformation algorithms, and in particular to a general method and apparatus for optical axis correction of airborne optical equipment. Background Technology

[0002] Existing airborne optoelectronic detection equipment and laser illumination pods contain several optoelectronic sensors distributed around the airborne optical equipment. The main functions of these devices are target search, identification, tracking, laser ranging, aiming, and imaging, with sensing wavelengths ranging from visible light to infrared. Optically, the various optoelectronic sensors are aligned with the aircraft's axis, ensuring their optical axes are parallel to each other. This multi-axis optical load exhibits optical axis consistency, guaranteeing effective cooperation and accurate target information.

[0003] However, since manufacturing errors of the aircraft and installation errors of the airborne optoelectronic detection equipment and laser illumination pod are uncontrollable factors during use, it is necessary to use the axis alignment method to correct the axis of the airborne optoelectronic detection equipment and laser illumination pod to ensure that they are parallel to the aircraft axis.

[0004] The current method for optical axis correction is as follows: First, level the aircraft; place the alignment equipment 30m directly in front of the aircraft, ensuring that the alignment equipment is perpendicular to the axis of the airborne inertial coordinate system; adjust the target position of the alignment equipment to be on the same horizontal line as the aircraft axis, and then operate the airborne optical equipment to aim at the target to complete the alignment.

[0005] Although existing optical axis alignment methods have advantages such as low substitution error, low installation accuracy requirements, and relatively easy fulfillment of optical axis alignment accuracy requirements, they also have the following drawbacks: large leveling errors for large aircraft, because the aircraft is large, fuel flows, and it is difficult to level, making it difficult to achieve high-precision lateral and longitudinal horizontal alignment; the leveling process requires human observation of the level and theodolite, resulting in large alignment errors, requiring many human eyes, and placing high demands on the operators, leading to high labor intensity, time and effort; even a slight mistake during the leveling process may damage the aircraft; the alignment equipment can only be placed directly in front of the aircraft, which may not be possible for airborne optical equipment with inconvenient installation locations to complete the optical axis alignment work. Summary of the Invention

[0006] This invention provides a general method and apparatus for optical axis calibration of airborne optical equipment, which can perform optical axis calibration of airborne optical equipment in any stationary state of the aircraft, reducing the process of leveling the aircraft frame, and can be applied to the optical axis calibration work of optical equipment installed in different positions on the aircraft body.

[0007] The first aspect of this invention provides a general method for optical axis correction of airborne optical equipment, comprising:

[0008] setting the total station at the first station, measuring coordinates of N reference points and 2 auxiliary measurement points in the total station coordinate system;

[0009] According to the coordinates of the two auxiliary measurement points in the total station coordinate system, the total station is set at the second station, and the coordinates of the two auxiliary measurement points measured by the total station at the second station are the same as the coordinates measured at the first station;

[0010] The total station measures the coordinates of M reference points in the total station coordinate system at the second station; M and N are positive integers, and the sum L of M and N is not less than 6; the L reference points are not repeated;

[0011] According to the coordinates of the L reference points in the total station coordinate system and in the aircraft coordinate system, the coordinate conversion formula is obtained;

[0012] According to the theoretical coordinates of the target point in the aircraft coordinate system and the coordinate conversion formula, the coordinates of the target point in the total station coordinate system are obtained;

[0013] According to the coordinates of the target point in the total station coordinate system, the target point is placed;

[0014] According to the placed target point, the on-board optical equipment is calibrated on board.

[0015] Optionally, the theoretical coordinates of the target point in the aircraft coordinate system are at a preset distance in front of the aircraft heading axis.

[0016] Optionally, the theoretical coordinates of the target point in the aircraft coordinate system are at a preset distance in front of the aircraft heading axis.

[0017] Optionally, the fuselage L reference points are provided with auxiliary measurement adapters, and the auxiliary measurement adapters are marked with cross lines.

[0018] Optionally, the fuselage L reference points include 2 belly reference points, and the auxiliary measurement adapters provided at the belly reference points are auxiliary measurement rods.

[0019] Optionally, the two auxiliary measurement points are respectively located below the nose and tail of the right side of the aircraft.

[0020] One set of reflecting prism is arranged on each of the two auxiliary measurement points.

[0021] Optionally, the fuselage L reference points include 4 fuselage reference points.

[0022] The first station and the second station are respectively located on both sides of the fuselage.

[0023] The second aspect of the application provides a general device for calibrating the optical axis of the on-board optical equipment, which is used to execute the method as described in any one of the first aspect.

[0024] The application provides a general method and device for correcting the optical axis of an airborne optical device, compared with the current axis correction method, the axis is corrected by using a total station instrument station transfer measurement mode, so that the axis correction precision is greatly improved; the method can be applied to any model of airplane and airborne optical device, and has good universality; since the airplane leveling process is not needed, manpower and material resources are obviously saved, and the work efficiency of the ground crew is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a work flow chart of the airborne optical device axis correction;

[0026] Figure 2 is a schematic diagram of total station instrument station position and resection measurement auxiliary measurement point position;

[0027] Figure 3 is a schematic diagram of using the axis correction device for axis correction in the total station instrument coordinate system;

[0028] Figure 4 is a man-machine interface for using the application for axis correction by taking the photoelectric detection device as an example;

[0029] Figure 5 is a man-machine interface for using the application for axis correction by taking the laser irradiation nacelle as an example. DETAILED DESCRIPTION

[0030] The application is further described in detail below in combination with examples and drawings:

[0031] The application provides a general method for correcting the optical axis of an airborne optical device, six measurement points on the known airplane and two station positions required when measuring the airplane reference point are known, and the method comprises the following contents:

[0032] 1) there is an axis correction system, the axis correction system comprises a total station instrument, an axis correction device (which is provided with a target point M), four body point auxiliary measurement adapters (the bottom is marked with a cross line), two belly point auxiliary measurement adapters (containing an auxiliary measurement rod, which is marked with a cross line), two sets of reflecting prisms, one set of coordinate conversion calculation device and the built-in coordinate conversion software thereof;

[0033] 2) the axis correction device is placed at a proper distance (about 30 m) in front of the airplane axis;

[0034] 3) two auxiliary measurement points C and D are selected below the nose and tail of the right side of the airplane, and the two auxiliary measurement points should be observed by station position 1 and station position 2 at the same time, and two sets of reflecting prisms are fixed on the two auxiliary measurement points;

[0035] 4) respectively screw 2 sets of the auxiliary measurement adapters of the belly points into the M12, M55 holes on the belly of the aircraft, screw 4 sets of the auxiliary measurement adapters of the fuselage points into the L12, L57, R12, R57 holes on the side of the fuselage of the aircraft, until the auxiliary measurement adapters are tangent to the fuselage of the aircraft, turn the auxiliary measurement rods on the auxiliary measurement adapters of the belly points, so that the cross lines thereon face the total station;

[0036] 5) select an appropriate position on the left side of the aircraft, place the total station at station 1, ensure that station 1 can simultaneously observe the reference points L12, L57, M12, M55 and the auxiliary measurement points C, D on the left side of the aircraft, and take station 1 as the initial station of the total station to establish the coordinate system of the total station;

[0037] 6) use the coordinate measurement function of the total station at station 1 to measure the coordinates of the 4 fixed measurement points on the side of the fuselage;

[0038] 7) use the total station to measure the coordinates of the auxiliary measurement points C, D respectively, input the measured coordinate values of the auxiliary measurement points C, D into the total station, use the resection measurement method of the total station to ensure the correct setting of station 2, and then complete the total station station transfer operation;

[0039] 8) measure the coordinates of the remaining two fixed measurement points on the side of the fuselage at station 2;

[0040] 9) start the coordinate conversion calculation device, select the aircraft model and the airborne optical equipment (optoelectronic detection equipment / laser illumination pod) being calibrated on the screen, and input the coordinate values of the 6 measurement points of the aircraft measured in the coordinate system of the total station respectively, because the theoretical coordinate values (in the coordinate system of the aircraft) of the target points M of various types of airborne optical equipment are known and have been written into the built-in coordinate conversion software, directly click the “coordinate calculation” button to calculate the final coordinate values of the target points M (in the current coordinate system of the total station) of the selected airborne optical equipment;

[0041] 10) perform coordinate lofting at the position of station 2, input the calculated coordinate values of the target points M into the total station, use the “coordinate lofting measurement” function of the total station to perform lofting measurement on the coordinates of the target points M, adjust the position of the coordinates of the target points M, so that the difference between the measurement value displayed by the total station and the input coordinate value of the target points M meets the accuracy requirement, and the accurate placement of the calibration equipment position is completed;

[0042] 11) start the airborne optical equipment that needs to be calibrated on the aircraft, and perform on-machine calibration operation.

[0043] The general method for optical axis correction of airborne optical equipment described above involves a rigid transformation between the aircraft coordinate system and the total station coordinate system. Utilizing the characteristic that the aircraft is essentially a rigid body, a matrix transformation is employed. First, a translation matrix T is used to translate the origin of the aircraft coordinate system P to the origin of the total station coordinate system B. Then, a rotation matrix R is applied to the aircraft coordinate system, rotating it sequentially around the X-axis by α, around the Y-axis by β, and around the Z-axis by θ, achieving complete overlap between the two coordinate systems, thus completing the coordinate transformation between the aircraft and total station coordinate systems. To solve for the transformation matrix set, the theoretical coordinate values ​​in the aircraft coordinate system and the coordinate values ​​of the measured points in the total station coordinate system (selecting four non-coplanar points) need to be substituted into the equation set to obtain the transformation matrix set (this method can yield eight sets of transformation matrices). A verification point (M12 and M55 are mutual verification points) is selected and substituted into the transformation matrix set, and compared with the measured coordinate values ​​to verify the accuracy of the total station setup and measurement. Then, by substituting the theoretical coordinates of the target point in the aircraft coordinate system, the calculated coordinates of the target point in the total station coordinate system can be obtained. After setting out with a total station, the actual position of the target point can be found. To maximize the accuracy of axis alignment, the method of solving multiple sets of data and averaging them is used to eliminate errors. The average value of the eight sets of data is taken as the final coordinate value of the target point M.

[0044] The method provided by this invention is used in a certain type of aircraft to achieve axis alignment of optical equipment installed at different positions on the aircraft body. For example, it includes the following:

[0045] 1. Selection of aircraft reference points

[0046] like Figure 1 As shown, six reference points were selected on the aircraft, denoted as L12, L57, R12, R57, M12, and M55. Points L12 and R12 are located on the left and right sides of frame 12 on the aircraft; points L57 and R57 are located on the left and right sides of frame 57 on the aircraft; point M12 is located on the lower belly of frame 12; and point M55 is located on the lower belly of frame 55. Their theoretical coordinates in the aircraft coordinate system are known.

[0047] L12(5.680, 0, 1.2499); R12(5.680, 0, -1.2499);

[0048] L57(25.230, 0, 1.0508); R57(25.230, 0, -1.0508);

[0049] M12(5.662,-1.250,0); M55(24.143,-1.1793,0).

[0050] 2. There is an axis alignment system, which contains a total station, an axis alignment device, four fuselage point auxiliary measurement adapters (with cross lines engraved on the bottom), two belly point auxiliary measurement adapters (with auxiliary measurement rods, which have cross lines engraved on them), two sets of reflecting prisms, one set of coordinate conversion calculation device and its built-in coordinate conversion software.

[0051] 3. Two auxiliary measurement points C and D are selected under the nose and tail of the right side of the airplane, ensuring that the two auxiliary measurement points can be observed by station 1 and station 2 at the same time, and two sets of reflecting prisms are fixed on the two auxiliary measurement points.

[0052] 4. Two sets of belly point auxiliary measurement adapters are screwed into the M12 and M55 holes on the belly of the airplane, and four sets of fuselage point auxiliary measurement adapters are screwed into the L12, L57, R12, and R57 holes on the side of the fuselage of the airplane, until the auxiliary measurement adapters are tangent to the fuselage of the airplane, and the auxiliary measurement rods on the belly point auxiliary measurement adapters are turned so that the cross lines on them face the total station.

[0053] 5. Establishment of total station coordinate system and measurement of reference point coordinates

[0054] The total station coordinate system is established with station 1 as the initial station of the total station, and the specific operation is as follows:

[0055] a) First, place the total station near the left wing of the airplane (use a tripod to hold it up), ensuring that the total station can simultaneously observe the two points (L12, L57) on the left side of the fuselage, the two points (M12, M55) under the belly, and the positions of the auxiliary measurement points C and D (reflecting prisms);

[0056] b) Measure the height H of the total station with a regular tape measure 仪 , and then use the ranging function of the total station to aim at a point in front of the 2# hanging point (called the rear view point), and measure the horizontal distance HD and the height difference VD between the total station and the rear view point;

[0057] c) Coordinate setting rear view of total station: set the coordinates of station 1 as (0, 0, 0), and select the coordinate setting rear view function on the total station to set the coordinates of the rear view point as (HD, 0, H 仪 +VD);

[0058] d) Measure the rear view point again in step b) to observe whether the measured value is the same as the set rear view point coordinates; if they are the same, the setting of station 1 is complete, otherwise start over from step b);

[0059] Note: Do not turn the total station before completing the coordinate setting rear view.

[0060] e) Coordinate measurement 1: Measure and record the coordinates of L12, L57, M12, M55 and auxiliary measurement points C, D using the coordinate measurement function (use auxiliary measurement adapter when measuring the coordinates of points on the airplane to ensure measurement accuracy);

[0061] f) Station 2 setup:

[0062] Move the total station to the right wing under the airplane, use the total station resection measurement function, input the coordinates of auxiliary measurement points C, D, then use the total station to measure the coordinates of auxiliary measurement points C, D again, and the total station will calculate the coordinates of station 2 itself after measurement. Then use the total station to measure the coordinates of any auxiliary measurement point again, and observe whether the measured value is the same as the value recorded in step 5.

[0063] If the same, it means that the station is set correctly, and the subsequent work can be carried out, otherwise, re-perform this step;

[0064] g) Coordinate measurement 2: Measure and record the coordinates of R12, R57; (After coordinate measurement is completed, do not move the total station at station 2, and wait for subsequent lofting)

[0065] h) Target point coordinate conversion: After selecting the aircraft model and the calibration optical equipment in the coordinate conversion calculation device, input the previously measured L12, L57, M12, M55, R12 and R57 coordinate values at the corresponding positions, click the coordinate conversion button, and the coordinate conversion calculation program will automatically convert the target point theoretical coordinate values in the aircraft coordinate system to the target point actual coordinate values in the total station coordinate system;

[0066] In the coordinate conversion used in the present calibration method, the aircraft coordinate system P (X, Y, Z), the total station coordinate system B (E, N, U), the conversion matrix R, and the translation matrix T, the conversion relationship between the two coordinate systems is B = R * P + T, that is,

[0067]

[0068] Wherein:

[0069]

[0070] is the transformation matrix of rotating α angle around X axis alone;

[0071] is the transformation matrix of rotating β angle around Y axis alone;

[0072] is the transformation matrix of rotating θ angle around X axis alone.

[0073] Let Then

[0074] Rewrite the equation set in matrix form into the form of general equation, that is:

[0075]

[0076] The above equation set contains 12 unknowns. To complete the equation set solution, 4 reference points on the aircraft which are not in the same plane should be measured, and 3 of the 4 points L12, L57, R12, R57 and 1 of the 2 points M12, M55 are selected to solve the conversion matrix set (this method can obtain 8 groups of conversion matrix set). Select a check point (M12 and M55 are check points for each other) and substitute it into the conversion matrix set, and compare it with the measured coordinate value to verify the accuracy of the total station setting and measurement. Then substitute the target point coordinate value in the aircraft coordinate system into the equation, and the target point coordinate value in the total station coordinate system can be obtained. Then through the total station lofting, the actual position of the target point can be found.

[0077] In order to improve the calibration accuracy as much as possible, the method of solving multiple sets of data and taking the average to eliminate errors is adopted. After solving 8 sets of data, the average value is taken as the final coordinate value of the target point.

[0078] i) Coordinate lofting: input the completed target coordinate value in the total station, and perform target coordinate lofting. Observe the difference between the measured value and the input coordinate value. If the difference is large, adjust the position of the calibration equipment and perform lofting measurement again until the difference meets the accuracy requirement.

[0079] j) Calibration: operate the optical equipment on the aircraft to calibrate the axis;

[0080] k) After the calibration is completed, turn off the optical equipment; after the total station is turned off, collect it; collect the calibration equipment; remove the 2 belly point auxiliary measurement adapters and the 4 fuselage point auxiliary measurement adapters from the aircraft and collect them.

Claims

1. A general method for on-board optical equipment optical axis correction, characterized in that, The method comprises the following steps: setting a total station at a first station, measuring coordinates of N reference points and 2 auxiliary measurement points in a total station coordinate system; setting the total station at a second station according to the coordinates of the 2 auxiliary measurement points in the total station coordinate system, the total station measuring the coordinates of the 2 auxiliary measurement points at the second station being the same as the coordinates measured at the first station; the total station measuring coordinates of M reference points in the total station coordinate system at the second station; M and N are positive integers, and the sum L of M and N is not less than 6; the L reference points are not repeated; obtaining a coordinate conversion formula according to the coordinates of the L reference points in the total station coordinate system and in an aircraft coordinate system; obtaining coordinates of a target point in the total station coordinate system according to a theoretical coordinate of the target point in the aircraft coordinate system and the coordinate conversion formula; placing the target point according to the coordinates of the target point in the total station coordinate system; performing on-board optical equipment on-board calibration according to the placed target point; the L reference points of the fuselage include 2 belly reference points, and the auxiliary measurement adapters arranged at the belly reference points are auxiliary measurement rods; the 2 auxiliary measurement points are respectively located below the nose and the tail of the right side of the aircraft; 1 set of reflecting prisms is arranged on each of the 2 auxiliary measurement points; the L reference points of the fuselage include 4 fuselage reference points; the first station and the second station are respectively located on the two sides of the fuselage.

2. The general method for onboard optical equipment optical axis correction according to claim 1, characterized in that, The theoretical coordinate of the target point in the aircraft coordinate system is a preset distance in front of the aircraft heading axis.

3. The general method for on-board optical equipment optical axis correction according to claim 1, characterized in that, The theoretical coordinate of the target point in the aircraft coordinate system is a preset distance in front of the aircraft yaw at a preset angle.

4. The general method for on-board optical equipment optical axis correction according to claim 1, characterized in that, The auxiliary measurement adapters are arranged at the L reference points of the fuselage, and the auxiliary measurement adapters are marked with cross lines.

5. A general device for correcting the optical axis of an airborne optical device, characterized in that, A device for performing the method according to any one of claims 1-4.

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