A method for calibrating the spatial coordinate reference of a target track based on a total station

Abstract

This invention provides a target trajectory spatial coordinate benchmark calibration method based on a total station, comprising: establishing a target trajectory coordinate system with the muzzle as the origin and a transition coordinate system with the total station as the origin, and measuring the initial distance between the muzzle and the total station; establishing a calibration coordinate system based on three non-collinear marker points on the calibration frame; performing three-dimensional coordinate measurements on the marker points using a target surface coordinate testing device and the total station respectively, obtaining the coordinate values ​​of the marker points in the calibration coordinate system and the transition coordinate system; establishing the transformation relationship from the calibration coordinate system to the transition coordinate system for each target surface testing device based on the Rodrigue matrix; and adding a compensation distance to establish the transformation relationship from the calibration coordinate system to the target trajectory coordinate system. This invention uses a three-point distance measurement method with a total station to replace the laser collimation system, which on the one hand improves the existing calibration method and increases the calibration accuracy, and on the other hand reduces the calibration workload and increases the calibration efficiency.

Description

Technical Field

[0001] This invention belongs to the field of spatial three-dimensional coordinate measurement and transformation, specifically involving a target track spatial coordinate benchmark calibration method based on a total station. Background Technology

[0002] A ballistic target track is a closed firing range specifically designed for free-flight tests, aerodynamic and ballistic performance studies of various projectiles or models. Its primary task is to measure the changes in the projectile's motion parameters (pitch and yaw angles) over time after exiting the muzzle (or gun muzzle), and to obtain the projectile's aerodynamic coefficients and flight stability discrimination factors through data processing, providing data support for theoretical projectile research. To improve the measurement accuracy of the target track coordinate testing system, meticulous calibration of the target track spatial reference system is required.

[0003] The accuracy of the target trajectory spatial reference system is a crucial factor affecting the accuracy of projectile flight attitude testing. A high-precision spatial reference system is essential for the smooth operation of all subsequent work and the accuracy of data measurement. Therefore, establishing a high-precision ballistic target trajectory spatial reference system is the primary task of target trajectory testing. However, existing target trajectory spatial reference systems suffer from problems such as short target trajectory distances, large calibration errors, low reliability, complex and cumbersome operation processes, difficulties in use and maintenance, and a lack of unified calibration methods. Therefore, there is an urgent need to conduct research on long-distance, high-precision target trajectory spatial measurement and positioning methods and high-precision target trajectory spatial reference design methods.

[0004] The earliest calibration method proposed in China used the orthogonal elevation of the spatial reticle to correct the camera position, and then used suspension lines and level liquid surfaces to further determine the spatial attitude of the reticle. This method requires the camera's optical axis to be orthogonal to the center of the reticle, which is difficult to achieve. In recent years, with the further development of related technologies, suspension line and level liquid surface attitude determination systems have been replaced by laser collimation systems, and film-type analog cameras have been replaced by high-resolution digital cameras. Currently, the latest method is a spatial reference system based on dual position sensors (PSD) and dual lasers. Two overlapping laser beams are used as spatial reference axes. Based on the position coordinates of the two laser beams fed back by the dual PSDs, the spatial position of the reference carrier is adjusted through a six-dimensional stepper motor control console, thereby establishing the target trajectory spatial reference system.

[0005] The laser beam from a laser collimator is used as the reference optical axis. The alignment of the reference carrier's side center axis with the muzzle line is adjusted based on the overlap between the reflected spot on the optical target and the initial spot. The alignment is further adjusted based on the spot coordinates measured by the PSD. The spatial positions of the shadow cameras on both sides are adjusted according to the reference carrier, ensuring that the principal optical axis of the shadow cameras coincides with the center of the grid on the opposite surface of the reference carrier, thus completing the calibration of the shadow cameras. While these methods improve system accuracy, they also present some challenges to the calibration process. These include: the laser collimation system is relatively bulky, making it difficult to use and maintain; and the curved track of the calibration vehicle, or its misalignment with the target trajectory, can cause the calibration object to fail to be positioned correctly at certain locations, thus affecting the calibration. Summary of the Invention

[0006] This invention addresses the problems existing in the calibration process of a spatial reference system with dual position sensors (PSD) and dual lasers, and proposes a target trajectory spatial coordinate reference calibration method based on a total station. This method improves existing calibration methods and increases calibration accuracy, while reducing calibration workload and increasing calibration efficiency.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] A method for calibrating the spatial coordinate reference of a target track based on a total station is implemented using a system consisting of a gun barrel, a total station, a calibration frame, a target surface coordinate testing device, a mobile lifting vehicle, and a computer. The method includes the following steps:

[0009] Step 1: Establish a target trajectory coordinate system with the muzzle as the origin and a transition coordinate system with the total station as the origin. Measure the initial distance between the muzzle and the total station.

[0010] Step 2: Establish a calibration coordinate system based on three non-collinear marker points on the calibration frame;

[0011] Step 3: Use the target surface coordinate testing equipment to measure the three marked points and record the coordinate values ​​of the three marked points in the calibration coordinate system;

[0012] Step 4: Use a total station to measure the three marker points and record their coordinates in the transition coordinate system;

[0013] Step 5: Based on the Rodrigue matrix, establish the transformation relationship between the current target surface coordinate testing equipment calibration coordinate system and the transition coordinate system;

[0014] Step 6: Compensate for the initial distance and establish the transformation relationship between the current target surface coordinate test equipment calibration coordinate system and the target track coordinate system, that is, complete the spatial reference calibration of the current target surface coordinate test equipment;

[0015] Step 7: Move the calibration frame to the next target coordinate testing device and repeat steps 2 to 6 until all target coordinate testing devices have been calibrated.

[0016] Furthermore, the transformation relationship from the calibration coordinate system to the transition coordinate system includes rotation and translation relationships, as shown in the following formula:

[0017] (1)

[0018] In the formula, Represents the coordinate values ​​in the transition coordinate system. This represents the coordinate value in the calibration coordinate system, where λ is the scale factor and λ = 1. , , R is the translation parameter, R is the rotation matrix from the calibration coordinate system to the transition coordinate system, and T is the translation matrix from the calibration coordinate system to the transition coordinate system.

[0019] The rotation matrix R from the calibration coordinate system to the transition coordinate system is calculated as follows:

[0020] (2)

[0021] In the formula, I is the identity matrix, and S is an antisymmetric matrix with three independent elements. The calculation formula is as follows:

[0022] (3)

[0023] In the formula, a, b, and c are rotation parameters, and their calculation process includes:

[0024] Define three non-collinear marker points as point 1, point 2, and point 3, and their coordinate values ​​in the calibrated coordinate system are respectively... , and The coordinate values ​​in the transition coordinate system are respectively , and ;

[0025] First, substitute the coordinates of point 1 and point 2 into equation (1), and then subtract the values ​​to eliminate the translation parameter, resulting in the following equation:

[0026] (4)

[0027] Combining equations (2), (3), and (4), we obtain the following equation:

[0028] (5)

[0029] In the formula, ; ;

[0030] Substitute the coordinates of points 1 and 3 into equation (1) and subtract the translation parameters to obtain the following equation:

[0031] (6)

[0032] In the formula, , ;

[0033] Combining equation (5) and equation (6), we obtain the following equation:

[0034] (7)

[0035] Find the rotation parameters a, b, and c, and you will get the rotation matrix R from the calibration coordinate system to the transition coordinate system.

[0036] After finding the rotation matrix R from the calibration coordinate system to the transition coordinate system, substituting the coordinates of point 1 into equation (1), we obtain the following equation:

[0037] (8)

[0038] The translation matrix parameter T from the calibration coordinate system to the transition coordinate system is thus obtained.

[0039] Furthermore, the transformation relationship from the calibration coordinate system to the target coordinate system is as follows:

[0040] (9)

[0041] In equation (9), R represents the coordinate values ​​in the target track coordinate system. R remains unchanged. T0 represents the rotation matrix from the calibration coordinate system to the target track coordinate system. L0 is the translation matrix from the calibration coordinate system to the target track coordinate system. I is the initial distance between the muzzle and the total station.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] This invention is applicable to the calibration of spatial references for conventional target track systems. It replaces the laser collimation system with a three-point distance measurement method using a total station, relaxing the relative positional constraints between the testing equipment and the calibration object, and avoiding the calibration difficulties caused by curved or non-parallel tracks on the calibration vehicle. The entire system has a simple structure, convenient movement and transportation of its components, easy operation, high calibration accuracy, and is easy to implement in engineering. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of a target trajectory spatial reference calibration system based on a total station.

[0045] Figure 2This is a schematic diagram of the calibration frame structure;

[0046] Figure 3 This is a flowchart of the calibration method.

[0047] (In the figure: 1-Barrel, 2-Muzzle marker, 3-Total station, 4-L1 target surface coordinate testing equipment, 5-L2 target surface coordinate testing equipment, 6-L2 target surface coordinate testing equipment, 7-Mobile lifting vehicle, 8-Calibration frame, 9-Feature marker, 10-Computer, 11-Light shield, 12-Reflector, 13-Calibration bracket) Detailed Implementation

[0048] To facilitate understanding of the present invention, a more comprehensive description will be given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0049] Example

[0050] like Figure 1 As shown, the present invention provides a target trajectory spatial reference calibration system based on a total station, including a gun barrel 1, a total station 3, an L1 target surface coordinate testing device 4, an L2 target surface coordinate testing device 5, an L3 target surface coordinate testing device 6, a mobile lifting vehicle 7, a calibration frame 8, and a computer 10 system. The gun barrel 1 has a muzzle marking point 2, and the calibration frame 8 has three non-collinear marking points 9. In the aforementioned target track spatial reference calibration system, the total station is a general-purpose instrument commonly used in civil engineering to determine the spatial coordinates of multiple points; it is a high-tech measuring instrument integrating optics, mechanics, and electronics. The mobile lifting vehicle can be freely adjusted in both horizontal and vertical directions. Three non-collinear characteristic measurement points are fixed on the calibration support for measurement by the coordinate testing equipment and the total station. The computer is a general-purpose device with storage, data calculation, processing, and display capabilities. The coordinate testing equipment refers to the coordinate testing equipment at different distances within the target track, capable of measuring the coordinate values ​​at the marked points. During operation, the testing equipment transmits the measured coordinate values ​​of the marked points to the computer via a data cable for storage, while the total station transmits the measured coordinates of the marked points on the calibration frame and the coordinates of the gun muzzle to the computer via a data cable for storage. Based on the obtained coordinate data, the computer calculates and determines the position of the testing equipment under the target track coordinates.

[0051] See Figure 3 The present invention employs the aforementioned target trajectory spatial reference calibration system and provides a target trajectory spatial reference calibration system method based on a total station, comprising the following steps:

[0052] Step 1: Establish a target trajectory coordinate system (OXYZ) with the muzzle as the origin, and a transition coordinate system (O´X´Y´Z´) with the total station as the origin. Install a reflector at the muzzle, position, fix, and start the total station. Align with the reflector, adjust the level and azimuth of the total station and zero it. Measure and record the initial distance L0 between the muzzle and the total station to establish the target trajectory coordinate system, where the origin of the target trajectory coordinate system is the muzzle position. Then rotate the total station 180 degrees to establish the transition coordinate system. The current aiming direction of the total station is the positive direction of the target trajectory coordinate X-axis. Find the vector pointing upwards and orthogonal to the X-axis in the vertical plane and record it as the target trajectory coordinate Y-axis. The direction of the target trajectory coordinate Z-axis satisfies the right-hand rule with the X-axis and Y-axis.

[0053] Step 2: Move the trolley to position the calibration frame at a suitable position on the L1 target surface of the test equipment, so that the light-blocking column can block the light curtain, and establish the calibration coordinate system oxyz based on the three non-collinear marker points on the calibration frame;

[0054] Step 3: Use the target surface coordinate testing equipment to measure the three marked points and record the coordinate values ​​of the three marked points in the calibration coordinate system;

[0055] Step 4: Use a total station to measure the three marker points and record their coordinates in the transition coordinate system;

[0056] Step 5: Based on the Rodrigue matrix, establish the transformation relationship between the current target surface coordinate testing equipment calibration coordinate system and the transition coordinate system;

[0057] Step 6: Compensate for the initial distance L0, establish the transformation relationship between the current target surface coordinate test equipment calibration coordinate system and the target track coordinate system, that is, complete the spatial reference calibration of the current target surface coordinate test equipment;

[0058] Step 7: Move the calibration frame to the next target coordinate testing device and repeat steps 2 to 6 until all target coordinate testing devices have been calibrated.

[0059] The transformation relationship from the calibration coordinate system (oxyz) to the transition coordinate system (O´X´Y´Z´) includes rotation and translation relationships, as shown in the following formulas:

[0060] (1)

[0061] In the formula, Represents the coordinate values ​​in the transition coordinate system. Represents the coordinate values ​​in the calibration coordinate system, λ = 1. , , R is the translation parameter, R is the rotation matrix from the calibration coordinate system to the transition coordinate system, and T is the translation matrix from the calibration coordinate system to the transition coordinate system.

[0062] The rotation matrix R from the calibration coordinate system to the transition coordinate system is calculated as follows:

[0063] (2)

[0064] In the formula, I is the identity matrix, and S is an antisymmetric matrix with three independent elements. The calculation formula is as follows:

[0065] (3)

[0066] In the formula, a, b, and c are rotation parameters, and their calculation process includes:

[0067] Define three non-collinear marker points as point 1, point 2, and point 3, and their coordinate values ​​in the calibrated coordinate system are respectively... , and The coordinate values ​​in the transition coordinate system are respectively , and ;

[0068] First, substitute the coordinates of point 1 and point 2 into equation (1), and then subtract the values ​​to eliminate the translation parameter, resulting in the following equation:

[0069] (4)

[0070] Combining equations (2), (3), and (4), we obtain the following equation:

[0071] (5)

[0072] In the formula, ; ;

[0073] Substitute the coordinates of points 1 and 3 into equation (1) and subtract the translation parameters to obtain the following equation:

[0074] (6)

[0075] In the formula, , ;

[0076] Combining equation (5) and equation (6), we obtain the following equation:

[0077] (7)

[0078] Find the rotation parameters a, b, and c, and you will get the rotation matrix R from the calibration coordinate system to the transition coordinate system.

[0079] After finding the rotation matrix R from the calibration coordinate system to the transition coordinate system, substituting the coordinates of point 1 into equation (1), we obtain the following equation:

[0080] (8)

[0081] The translation matrix parameter T from the calibration coordinate system to the transition coordinate system is thus obtained.

[0082] The transformation relationship from the calibration coordinate system (oxyz) to the target coordinate system (OXYZ) is as follows:

[0083] (9)

[0084] In the formula, R represents the coordinate values ​​in the target track coordinate system. R remains unchanged. T0 represents the rotation matrix from the calibration coordinate system to the target track coordinate system. L0 is the translation matrix from the calibration coordinate system to the target track coordinate system. I is the initial distance between the muzzle and the total station.

[0085] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A total station-based target path space coordinate reference calibration method, which is implemented by a system composed of a gun barrel, a total station, a calibration frame, a target surface coordinate test device, a mobile lifting vehicle, and a computer, characterized in that: The method comprises the following steps: Step 1: establishing a target path coordinate system with the muzzle as the origin and a transition coordinate system with the total station as the origin, and measuring the initial distance between the muzzle and the total station; Step 2: establishing a calibration coordinate system based on three non-collinear mark points on the calibration frame; Step 3: measuring the three mark points using the target surface coordinate testing equipment and recording the coordinate values of the three mark points in the calibration coordinate system; Step 4: measuring the three mark points using the total station and recording the coordinate values of the three mark points in the transition coordinate system; Step 5: establishing a conversion relationship from the calibration coordinate system of the current target surface coordinate testing equipment to the transition coordinate system based on the Rodrigues matrix; Step 6: compensating for the initial distance, establishing a conversion relationship from the calibration coordinate system of the current target surface coordinate testing equipment to the target path coordinate system, i.e. completing the spatial reference calibration of the current target surface coordinate testing equipment; Step 7: moving the calibration frame to the front of the next target surface coordinate testing equipment and repeating steps 2 to 6 until all target surface coordinate testing equipment is calibrated; The conversion relationship from the calibration coordinate system to the transition coordinate system comprises a rotation relationship and a translation relationship, and the relationship is as follows: (1) wherein represents coordinate values in the transition coordinate system, represents coordinate values in the calibration coordinate system, λ is a scale factor and λ = 1, , , is a translation parameter, R is a rotation matrix of the calibration coordinate system to the transition coordinate system, and T is a translation matrix of the calibration coordinate system to the transition coordinate system; The calculation formula of the rotation matrix R from the calibration coordinate system to the transition coordinate system is as follows: (2) In the formula, I is a unit matrix, and S is an anti-symmetric matrix with three independent elements, and the calculation formula is as follows: (3) In the formula, a, b and c are rotation parameters, and the calculation process comprises: Three non-collinear mark points are defined as point 1, point 2 and point 3, the coordinate values of which in the calibration coordinate system are respectively: , and , the coordinate values of which in the transition coordinate system are respectively: , and ; First, the coordinate values of point 1 and point 2 are respectively brought into formula (1), and the difference is eliminated to obtain the following formula: (4) Joint formula (2), (3) and (4) to obtain the following formula: (5) In the formulae, ; ; Then, the coordinate values of point 1 and point 3 are respectively brought into formula (1), and the difference is eliminated to obtain the following formula: (6) In the formulae, , ; Joint formula (5) and formula (6) to obtain the following formula: (7) The rotation parameters a, b and c are solved, and the rotation matrix R from the calibration coordinate system to the transition coordinate system is obtained; After the rotation matrix R from the calibration coordinate system to the transition coordinate system is solved, the coordinate value of point 1 is brought into formula (1) to obtain the following formula: (8) The translation matrix parameter T from the calibration coordinate system to the transition coordinate system is obtained; The conversion relationship from the calibration coordinate system to the target path coordinate system is as follows: (9) In the formula, R is a rotation matrix from the calibration coordinate system to the target coordinate system, T0 is a translation matrix from the calibration coordinate system to the target coordinate system, L0 is an initial distance between the muzzle and the total station, and I is a unit matrix.

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