Universal method and device for correcting optical axis of airborne optical equipment

Abstract

The invention provides a general method and device for correcting the optical axis of airborne optical equipment, and the method comprises the steps: arranging a total station at a first station, and measuring the coordinates of N reference points and two auxiliary measurement points in a coordinate system of the total station; according to the coordinates of the two auxiliary measuring points in the total station coordinate system, the total station is arranged at a second station, and the coordinates, measured at the second station, of the two auxiliary measuring points are the same as the coordinates, measured at the first station, of the total station; the total station measures the coordinates of the M datum points in the coordinate system of 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 datum points are not repeated; acquiring a coordinate conversion formula according to the coordinates of the L datum points in the coordinate system of the total station and the coordinates of the L datum points in the coordinate system of the airplane; according to the theoretical coordinate of the target spot in the aircraft coordinate system and a coordinate conversion formula, obtaining the coordinate of the target spot in the total station coordinate system; placing the target spot according to the coordinate of the target spot under the coordinate system of the total station; and carrying out on-board axis calibration on the on-board optical equipment according to the placed target spot. The shaft calibration precision can be greatly improved; the method can be suitable for airplanes of any model and airborne optical equipment thereof, and is good in universality; due to the fact that the aircraft leveling process is not needed, manpower and material resources are obviously saved, and the working efficiency of ground crew is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of rigid body motion theory and coordinate system conversion algorithm, and in particular to a general method and device for correcting the optical axis of airborne optical equipment. Background Art

[0002] The existing airborne photoelectric detection equipment and laser irradiation pods contain several photoelectric sensors, which are distributed around the airborne optical equipment. The main functions of airborne photoelectric detection equipment and laser irradiation pods are to search, identify, track, laser range finder, aim, image, etc., and the sensing band ranges from visible light to infrared. Its several photoelectric sensors are optically based on the aircraft axis to ensure that their respective optical axes are parallel to each other. This is the consistency of the optical axes of multi-axis optical loads, which ensures effective coordination and accurate target information.

[0003] However, since the manufacturing error of the aircraft and the installation error of the airborne photoelectric detection equipment and the laser irradiation pod are uncontrollable factors during use, it is necessary to use the axis calibration method to correct the axis of the airborne photoelectric detection equipment and the laser irradiation pod to ensure that it is parallel to the axis of the aircraft.

[0004] The currently used optical axis correction method is: first level the aircraft; place the axis correction device 30m in front of the aircraft, ensuring that the axis correction device is perpendicular to the axis of the airborne inertial coordinate system; adjust the center of the axis correction device to be on the same horizontal line as the aircraft axis, and then operate the airborne optical device to aim at the center of the axis correction to complete the axis correction.

[0005] Although the existing optical axis correction method has the advantages of less substitution error, low installation accuracy requirement, and easier to meet the optical axis correction accuracy requirement, it also has the following disadvantages: the leveling error is large for large aircraft, because the aircraft is huge and the fuel is flowing, it is not easy to level, and it is difficult to achieve high-precision lateral and longitudinal levels; the leveling process requires human eyes to observe the level and theodolite, the alignment error is large, the operation requires many eyes, and the requirements for operators are also high, the labor intensity is high, and it is time-consuming and labor-intensive; the slightest mistake in the leveling process may damage the aircraft; the axis correction equipment can only be placed in front of the aircraft, and for airborne optical equipment with inconvenient installation positions, it may not be possible to complete the optical axis alignment work. Summary of the invention

[0006] The present invention provides a general method and device for optical axis correction of airborne optical equipment, which can calibrate the optical axis of the airborne optical equipment in any parking state of the aircraft, reducing the process of leveling the aircraft frame, and can be applied to the axis correction work of optical equipment installed at different positions of the aircraft body.

[0007] A first aspect of the present invention provides a general method for calibrating an optical axis of an airborne optical device, comprising:

[0008] Set the total station at the first station position, and measure the 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 a second station position, and the coordinates of the two auxiliary measurement points measured by the total station at the second station position are the same as the coordinates measured at the first station position;

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

[0011] Obtain a coordinate conversion formula based on the coordinates of L reference points in the total station coordinate system and the coordinates in the aircraft coordinate system;

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

[0013] Place the target point according to its coordinates in the total station coordinate system;

[0014] Perform on-board calibration of the airborne optical equipment based on the placed targets.

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

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

[0017] Optionally, auxiliary measurement adapters are provided at L reference points of the fuselage, and cross lines are engraved on the auxiliary measurement adapters.

[0018] Optionally, 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.

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

[0020] A set of reflecting prisms is respectively arranged at two auxiliary measuring points.

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

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

[0023] A second aspect of the present invention provides a general device for calibrating the optical axis of an airborne optical device, which is used to execute the method as described in any one of the first aspects.

[0024] The present invention provides a universal method and device for calibrating the optical axis of airborne optical equipment. Compared with the current axis calibration method, the axis calibration is performed by adopting a total station transfer measurement method, which can greatly improve the axis calibration accuracy; the method can be applied to any type of aircraft and its airborne optical equipment, and has good versatility; since the aircraft leveling process is not required, manpower and material resources are obviously saved, and the work efficiency of ground staff is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the workflow diagram for aligning the axis of airborne optical equipment;

[0026] Figure 2 It is a schematic diagram of the total station position and the auxiliary measurement points for the resection measurement;

[0027] Figure 3 It is a schematic diagram of using the axis calibration equipment to calibrate the axis in the total station coordinate system;

[0028] Figure 4 It is a human-computer interaction interface for calibrating axes using the present application, taking photoelectric detection equipment as an example;

[0029] Figure 5 The laser irradiation pod is used as an example to calibrate the axis using the present application. DETAILED DESCRIPTION

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

[0031] The present invention provides a general method for calibrating the optical axis of an airborne optical device. It is known that 6 measuring points on an aircraft and 2 stations need to be set when measuring the aircraft reference points, which includes the following contents:

[0032] 1) There is an axis calibration system, which includes a total station, an axis calibration device (with a target point M), 4 fuselage point auxiliary measurement adapters (with crosshairs engraved on the bottom), 2 belly point auxiliary measurement adapters (including auxiliary measurement rods with crosshairs engraved on them), 2 sets of reflecting prisms, 1 set of coordinate conversion calculation device and its built-in coordinate conversion software;

[0033] 2) Place the axis calibration equipment at an appropriate distance (about 30m) in front of the aircraft axis;

[0034] 3) Select two auxiliary measurement points C and D below the nose and tail on the right side of the aircraft, ensure that the two auxiliary measurement points can be observed by both station 1 and station 2 at the same time, and fix two sets of reflecting prisms on the two auxiliary measurement points respectively;

[0035] 4) Screw two sets of belly point auxiliary measurement adapters into the M12 and M55 holes on the belly of the aircraft respectively, and screw four sets of fuselage point auxiliary measurement adapters into the L12, L57, R12, and R57 holes on the side of the aircraft fuselage until the auxiliary measurement adapters are tangent to the aircraft fuselage. Turn the auxiliary measurement rod on the belly point auxiliary measurement adapter so that the crosshairs on it face the total station;

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

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

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

[0039] 8) Perform coordinate measurement of the remaining two fixed measurement points on the fuselage on this side at station 2;

[0040] 9) Start the coordinate conversion calculation device, select the aircraft model and the airborne optical equipment (photoelectric detection equipment / laser irradiation pod) that is being calibrated on the screen, and enter the coordinate values ​​of the six measurement points of the aircraft measured in the total station coordinate system. Since the theoretical coordinate values ​​of the target point M of each type of airborne optical equipment (in the aircraft coordinate system) are known and have been written into its built-in coordinate conversion software, directly click the "Coordinate Calculation" button to solve the calculated coordinate values ​​of the final target point M of the selected airborne optical equipment (in the current total station coordinate system);

[0041] 10) Perform coordinate setting at the position of station 2, input the calculated target point M coordinate value into the total station, use the "coordinate setting measurement" function of the total station to set out and measure the target point M coordinate, adjust the position of the target point M coordinate, make the difference between the measured value displayed by the total station and the input target point M coordinate meet the accuracy requirements, and then complete the accurate placement of the axis calibration equipment;

[0042] 11) Start the onboard optical equipment that needs to be aligned and perform the alignment operation on board.

[0043] In the above-mentioned general method for correcting the optical axis of airborne optical equipment, the coordinate conversion between the aircraft coordinate system and the total station coordinate system is a rigid transformation. By using the characteristic that the aircraft is essentially a rigid structure, a matrix conversion method is adopted. First, a translation matrix T is converted to translate the origin of the aircraft coordinate system P to the origin of the total station coordinate system B. Then the aircraft coordinate system is transformed by the rotation matrix R, and the aircraft coordinate system P is rotated by α around the X axis, β around the Y axis, and θ around the Z axis in sequence to achieve complete coincidence of the two coordinate systems, that is, the coordinate conversion between the aircraft coordinate system and the total station coordinate system is completed. In order to solve the conversion matrix group, it is necessary to substitute the theoretical coordinate values ​​in the aircraft coordinate system and the coordinate values ​​of the measurement points in the total station coordinate system (select 4 non-coplanar points) into the equation group, and the conversion matrix group can be solved (this method can obtain 8 conversion matrix groups). Select a check point (M12 and M55 are check points for each other) and substitute it into the conversion matrix group, and compare it with the measured coordinate value to verify the accuracy of the total station station establishment and measurement. Then, the theoretical coordinates of the target in the aircraft coordinate system are substituted to obtain the calculated coordinates of the target in the total station coordinate system. After the total station is laid out, the actual position of the target can be found. In order to improve the calibration accuracy as much as possible, the method of solving multiple sets of data and taking the average is used to eliminate the error. The average value of the 8 sets of data is taken as the coordinate value of the final target M.

[0044] The method provided by the present invention is used in a certain type of machine to realize the axis alignment of optical devices installed at different positions of the machine body, which exemplarily includes the following contents:

[0045] 1. Aircraft reference point selection

[0046] like Figure 1 As shown, 6 reference points are selected on the aircraft, which are recorded 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. Its theoretical coordinate values ​​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 calibration system, which includes 1 total station, 1 axis calibration equipment, 4 fuselage point auxiliary measurement adapters (with crosshairs engraved on the bottom), 2 belly point auxiliary measurement adapters (including auxiliary measuring rods with crosshairs engraved on them), 2 sets of reflecting prisms, 1 set of coordinate conversion calculation device and its built-in coordinate conversion software.

[0051] 3. Select two auxiliary measurement points C and D under the nose and tail on the right side of the aircraft, ensure that the two auxiliary measurement points can be observed by station 1 and station 2 at the same time, and fix two sets of reflecting prisms on the two auxiliary measurement points respectively.

[0052] 4. Screw two sets of belly point auxiliary measurement adapters into the M12 and M55 holes on the belly of the aircraft respectively, and screw four sets of fuselage point auxiliary measurement adapters into the L12, L57, R12, and R57 holes on the side of the aircraft fuselage until the auxiliary measurement adapters are tangent to the aircraft fuselage. Turn the auxiliary measurement rod on the belly point auxiliary measurement adapter so that the crosshairs on it face the total station.

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

[0054] Use station 1 as the total station's initial station to establish the total station coordinate system. The specific operations are as follows:

[0055] a) First place the total station near the left wing of the aircraft (set up on a tripod), making sure that when the total station is placed in this position, it can simultaneously see two points on the left side of the fuselage (L12, L57), two points under the belly (M12, M55) and the positions of the auxiliary measurement points C and D (reflecting prisms);

[0056] b) Measure the total station height H using a common tape measure 仪 , then use the distance measurement function of the total station to aim at a point in front of the 2# hanging point (called the backsight point), and use the total station to measure the horizontal distance HD and height difference VD between it and the backsight point;

[0057] c) Total station coordinate setting backsight: used to determine the reference orientation of the total station coordinate system. Set the coordinates of station 1 to (0, 0, 0), select the coordinate setting backsight function on the total station, and set the backsight point coordinates to (HD, 0, H 仪 +VD);

[0058] d) Measure the backsight point in step b) again to see if the measured value is the same as the backsight point coordinates set above; if they are the same, then complete the setting of station 1, otherwise, start again from step b);

[0059] Note: Do not rotate the total station before completing the coordinate backsight.

[0060] e) Coordinate measurement 1: Use the coordinate measurement function to measure and record the coordinates of L12, L57, M12, M55 and auxiliary measurement points C and D (when measuring the coordinates of points on the aircraft, an auxiliary measurement adapter is required to ensure measurement accuracy);

[0061] f) Station 2 settings:

[0062] Move the total station to the right side of the aircraft wing, use the total station's resection measurement function to input the coordinates of auxiliary measurement points C and D, and then use the total station to measure the coordinates of auxiliary measurement points C and D respectively. After the measurement is completed, the total station will calculate the coordinates of station 2. Then use the total station to measure the coordinates of any auxiliary measurement point again to see if the measured value is the same as the value recorded in step 5.

[0063] If they are the same, it means the site is set up correctly and you can proceed with the subsequent work. Otherwise, repeat this step.

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

[0065] h) Target coordinate conversion: In the coordinate conversion calculation device, after selecting the aircraft model and the axis calibration optical device, input the previously measured L12, L57, M12, M55, R12 and R57 coordinate values ​​at the corresponding positions. After clicking the coordinate conversion button, the coordinate conversion calculation program automatically converts the theoretical coordinate values ​​of the target in the aircraft coordinate system into the actual coordinate values ​​of the target in the total station coordinate system;

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

[0067]

[0068] in:

[0069]

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

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

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

[0073] make but

[0074] Rewrite the matrix equations into a regular equations form, namely:

[0075]

[0076] The above equations contain 12 unknowns. To solve the equations, four reference points on the aircraft that are not in the same plane should be measured, and three points from the four points L12, L57, R12, and R57, and one point from the two points M12 and M55 can be selected to solve the transformation matrix group (this method can produce 8 transformation matrix groups). Select a check point (M12 and M55 are check points for each other) and substitute it into the transformation matrix group, and compare it with the measured coordinate values ​​to verify the accuracy of the total station station establishment and measurement. Then substitute the target coordinate value in the aircraft coordinate system to obtain the target coordinate in the total station coordinate system, and then find the actual position of the target through total station layout.

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

[0078] i) Coordinate setting out: Input the converted target coordinate value into the total station, perform target coordinate setting out, and observe the difference between the measured value and the input coordinate value. If the difference is large, adjust the position of the axis calibration equipment and perform setting out measurement again until the difference meets the accuracy requirements;

[0079] j) Axis calibration: operate optical equipment on board to calibrate the axis;

[0080] k) After the calibration is completed, turn off the optical equipment; shut down the total station and put it away; put away the calibration equipment; remove the two belly point auxiliary measurement adapters and the four fuselage point auxiliary measurement adapters from the aircraft and put them away.

Claims

1. A general method for optical axis calibration of airborne optical equipment, characterized in that: include: Set the total station at the first station position, and measure the coordinates of N reference points and 2 auxiliary measurement points in the total station coordinate system; According to the coordinates of the two auxiliary measurement points in the total station coordinate system, the total station is set at a second station position, and the coordinates of the two auxiliary measurement points measured by the total station at the second station position are the same as the coordinates measured at the first station position; The total station measures the coordinates of M reference points in the total station coordinate system at the second station position; M and N are positive integers, and the sum of M and N is not less than 6; the L reference points are not repeated; Obtain a coordinate conversion formula based on the coordinates of L reference points in the total station coordinate system and the coordinates in the aircraft coordinate system; According to the theoretical coordinates of the target in the aircraft coordinate system and the coordinate conversion formula, the coordinates of the target in the total station coordinate system are obtained; Place the target point according to its coordinates in the total station coordinate system; Perform on-board calibration of the airborne optical equipment based on the placed targets.

2. The general method for optical axis calibration of airborne optical equipment according to claim 1, characterized in that: The theoretical coordinates of the target in the aircraft coordinate system are the preset distance directly in front of the aircraft's heading axis.

3. The general method for optical axis calibration of airborne optical equipment according to claim 1, characterized in that: The theoretical coordinates of the target in the aircraft coordinate system are the preset distance in front of the aircraft at the preset yaw angle.

4. The general method for optical axis calibration of airborne optical equipment according to claim 1, characterized in that: Auxiliary measurement adapters are provided at L reference points of the fuselage, and cross lines are engraved on the auxiliary measurement adapters.

5. The general method for optical axis calibration of airborne optical equipment according to claim 1, characterized in that: 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.

6. The general method for optical axis calibration of airborne optical equipment according to claim 1, characterized in that: The two auxiliary measurement points are located on the right side of the aircraft, below the nose and tail; A set of reflecting prisms is respectively arranged at two auxiliary measuring points.

7. The general method for optical axis calibration of airborne optical equipment according to claim 5, characterized in that: The L fuselage reference points include: 4 fuselage reference points; The first and second stations are located on both sides of the fuselage.

8. A universal device for calibrating the optical axis of an airborne optical device, characterized in that: Used to perform the method according to any one of claims 1 to 7.

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