A high-precision electric shaft mechanical shaft calibration method based on joint measurement

Abstract

The application provides a high-precision electric shaft mechanical shaft calibration method based on joint measurement. The position of a target in a radar mechanical shaft coordinate system is accurately measured through multiple measurement methods such as visual measurement and theodolite measurement, combined with public point conversion. Finally, according to the measurement result of the radar on the target position, the angle deviation between the radar electric shaft and the mechanical shaft and the radar angle measurement error are calculated, so as to realize high-precision angle calibration of the radar and high-precision calibration of the deviation between the radar electric shaft and the radar mechanical shaft.

Description

Technical Field

[0001] This invention relates to the aerospace field, and in particular to a high-precision electric and mechanical axis calibration method based on joint measurement, which can be applied to the field of radar electric and mechanical axis calibration technology. Background Technology

[0002] Currently, for spaceborne mechanically scanned radars, the radar is generally mounted on a satellite platform to provide target measurement information for the satellite. Mechanically scanned radars typically use a two-dimensional drive mechanism to move the radar antenna to achieve search, tracking, and measurement. Due to installation errors in the radar antenna and the two-dimensional drive mechanism, there are errors between the mechanical axis of the two-dimensional drive mechanism and the electrical axis of the radar measurement. Therefore, to meet the application requirements of radar system testing and calibration, it is necessary to calibrate the radar's electrical and mechanical axes. However, traditional electrical and mechanical axis calibration methods cannot meet the requirements for high-precision angle measurement and calibration of electrical and mechanical axis deviations. Summary of the Invention

[0003] The purpose of this invention is to provide a high-precision electric axis and mechanical axis calibration method based on joint measurement. By using multiple measurement methods such as visual measurement and theodolite measurement, combined with common point conversion, the position of the target in the radar mechanical axis coordinate system is accurately measured. Finally, based on the radar's measurement results of the target position, the angular deviation between the radar electric axis and the mechanical axis, as well as the radar angle measurement error, are calculated, thereby achieving high-precision radar angle measurement calibration and high-precision calibration of the deviation between the radar electric axis and the radar mechanical axis.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0005] A high-precision electric shaft mechanical shaft calibration method based on joint measurement includes:

[0006] An electric and mechanical axis calibration system was built in a microwave anechoic chamber. The horn antenna of the simulated target was installed on a two-dimensional scanning frame. A cross target was attached to the front of the horn antenna, with the center of the cross target coinciding with the normal of the horn antenna. The radar antenna mechanism was installed on a T-shaped fixture, and a cubic prism was installed on the base of the radar antenna mechanism.

[0007] The assembly of the radar antenna mechanism and the T-shaped fixture is placed horizontally, with the radar antenna normal facing upwards. Target points are attached to the side of the T-shaped fixture, and the position of the target points in the cubic prism coordinate system is measured using two theodolites.

[0008] In front of the two-dimensional scanning frame, the assembly of the radar antenna mechanism and the T-shaped fixture is placed vertically with the normal of the radar antenna facing the two-dimensional scanning frame. Target points are attached to the edge of the radar antenna and the back of the T-shaped fixture. The radar antenna mechanism is controlled to rotate the azimuth and pitch axes. The position of the target points on the side and back of the T-shaped fixture in the radar mechanical axis coordinate system is obtained using a single-camera measurement system.

[0009] Using the coordinates of the target point on the back of the T-shaped tooling as a common point, the transformation relationship between the radar mechanical axis coordinate system and the prism coordinate system is calculated.

[0010] The horn antenna radiates the target echo signal. The radar receives the target echo signal and controls the mechanism to track the horn. At the same time, it outputs the elevation and azimuth angles of the horn antenna in the radar mechanical axis coordinate system. It controls the two-dimensional scanning frame to move the horn antenna to different positions. Two theodolites are used to measure the positions of the target point on the back of the horn antenna and the radar antenna in the theodolite measurement coordinate system. The measured values ​​of the elevation and azimuth angles in the radar mechanical axis coordinate system are recorded.

[0011] Using the coordinates of the target point on the back of the T-shaped fixture as a common point, the position of the horn antenna in the theodolite coordinate system is transferred to the position in the radar mechanical axis coordinate system. Then, based on the geometric relationship, the elevation and azimuth angles of the mechanism are mapped to obtain the calibration values. The error between the measured values ​​of the radar elevation and azimuth angles and the calibration values ​​is calculated. The mean error is the error of the electric axis deviating from the radar mechanical axis, and the variance of the error is the radar angle measurement accuracy.

[0012] Optionally, the movement of the two-dimensional scanning frame causes the horn antenna to move in both horizontal and vertical directions.

[0013] Optionally, the cubic prism coordinate system is established as follows:

[0014] Set up two theodolites that have been aligned with each other, aim at the reference scale, add scale information to the theodolite measurement system, and establish the theodolite measurement system.

[0015] In the theodolite surveying system, two theodolites are used to collimate the cube prism, determine the positional relationship between the cube prism coordinate system and the two theodolites, measure the crosshairs of the prism using the two theodolites, determine the origin of the prism coordinate system, and establish the prism coordinate system in the theodolite surveying system.

[0016] Optionally, a single-camera measurement system is used to obtain the positions of the target points on the side and back of the T-shaped tooling in the radar mechanical axis coordinate system, including:

[0017] A single-camera measurement system was used to monitor the position of the target point at the edge of the antenna, as well as the positions of the target points on the side and back of the T-shaped fixture.

[0018] By fitting two circles to the position of the target point at the edge of the antenna, the straight line passing through the center of the circle and perpendicular to the plane of the circle is the radar mechanical axis, and the intersection of the two straight lines is the origin of the radar mechanical axis coordinate system, thus obtaining the position of the target point on the side and back of the T-shaped fixture in the radar mechanical axis coordinate system.

[0019] Optionally, the step of using the coordinates of the target point on the back of the T-shaped tooling as a common point to deduce the geometric relationship between the radar mechanical axis coordinate system and the prism coordinate system specifically includes:

[0020] Select at least three common points that simultaneously possess both radar mechanical axis coordinate system and prism coordinate system, list the error equation for each common point, calculate the transformation parameters between radar mechanical axis coordinate system and prism coordinate system using the least squares principle, eliminate common points with large errors based on the error between the transformed coordinate position and the measured coordinate position, and calculate the transformation parameters between radar mechanical axis coordinate system and prism coordinate system for the remaining common points using the least squares principle.

[0021] Compared with the prior art, the present invention has the following technical effects:

[0022] The present invention provides a high-precision electric axis and mechanical axis calibration method based on joint measurement, which realizes high-precision angle measurement calibration of radar and high-precision calibration of electric axis deviation from radar mechanical axis error. It also obtains the transformation relationship between radar mechanical axis coordinate system and prism coordinate system. It has the advantages of high measurement accuracy and comprehensive measurement results, providing accurate and comprehensive data for system compensation. Attached Figure Description

[0023] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the drawings described below are one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort:

[0024] Figure 1 Here is a flowchart of a high-precision electric shaft / mechanical shaft calibration method based on joint measurement;

[0025] Figure 2 A block diagram of an electric shaft / mechanical shaft calibration system under microwave anechoic chamber conditions;

[0026] Figure 3 A schematic diagram of target point measurement in the prism coordinate system;

[0027] Figure 4 Schematic diagram of target point measurement in radar mechanical axis coordinate system;

[0028] Figure 5 A schematic diagram for high-precision calibration of the horn antenna position for simulating a radar target;

[0029] Figure 6 A schematic diagram of the transformation from the radar mechanical axis coordinate system to the angle measurement coordinate system. Detailed Implementation

[0030] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the solution proposed by the present invention. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of the present invention. Please refer to the drawings to make the objectives, features, and advantages of the present invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the present invention, should still fall within the scope of the technical content disclosed in the present invention.

[0031] This invention provides a high-precision electric shaft / mechanical shaft calibration method based on joint measurement, such as... Figure 1 As shown, its specific implementation method is as follows:

[0032] Step S1: Set up an electric shaft / mechanical shaft calibration system in a microwave anechoic chamber, such as... Figure 2 As shown, the specific components include: a horn antenna simulating a target is mounted on a two-dimensional scanning frame in a microwave anechoic chamber; the movement of the two-dimensional scanning frame causes the horn antenna to move in both horizontal and vertical directions; a cross-shaped target is attached to the front of the horn antenna, ensuring that the center of the cross-shaped target coincides with the normal of the horn antenna; the radar antenna mechanism is mounted on a T-shaped fixture, and a cubic prism is mounted on the base of the radar antenna mechanism, ensuring that the two faces of the cubic prism are not obstructed by the radar antenna mechanism.

[0033] Step S2, perform target point measurement in the prism coordinate system, such as... Figure 3 As shown, the specific steps include: setting up two theodolites that have been mutually aimed at each other, aiming at the reference scale, adding scale information to the theodolite measurement system, and establishing the theodolite measurement system. Within the theodolite measurement system, the two theodolites are used to collide with the cube prism, determining the pose relationship between the prism coordinate system and the two theodolites. The two theodolites are used to measure the prism crosshairs, determining the origin of the prism coordinate system, and establishing the prism coordinate system within the theodolite measurement system. The radar antenna mechanism and the T-shaped fixture assembly are placed horizontally, with the radar antenna normal facing upwards. Target points are attached to the side of the T-shaped fixture, and the theodolites are used to measure the position of the target points in the cube prism coordinate system.

[0034] Step S3, perform target point measurement in the radar mechanical axis coordinate system, such as... Figure 4As shown, the specific steps include: placing the radar antenna mechanism and the T-shaped fixture assembly vertically in front of the 2D scanning frame, with the antenna normal facing the 2D scanning frame; attaching two target points at the edge of the antenna and multiple target points on the back of the T-shaped fixture; controlling the rotation of the radar antenna mechanism along its azimuth and elevation axes; and using a single-camera measurement system to obtain the positions of the target points on the side and back of the T-shaped fixture in the radar mechanical axis coordinate system. Specifically, the single-camera measurement system monitors the movement of the target points at the antenna edge and the positions of the target points on the side and back of the T-shaped fixture. Two circles are fitted using the movement of the target points at the antenna edge, with the straight line passing through the center of the circle and perpendicular to the plane of the circle representing the radar mechanical axis. The intersection of the two straight lines is the origin of the radar mechanical axis coordinate system, thus obtaining the positions of the target points on the side and back of the T-shaped fixture in the radar mechanical axis coordinate system.

[0035] Step S4 involves performing a transformation between the radar mechanical axis coordinate system and the prism coordinate system based on common points. Specifically, this includes using the target point coordinates on the back of the T-shaped fixture as common points to calculate the transformation relationship between the radar mechanical axis coordinate system and the prism coordinate system. Specifically, at least three common points that simultaneously possess both radar mechanical axis and prism coordinate systems are selected. The error equation for each common point is listed, and the transformation parameters between the radar mechanical axis coordinate system and the prism coordinate system are calculated using the least squares principle. Based on the error between the transformed coordinate positions and the measured coordinate positions, common points with large errors are eliminated. The remaining common points are then used to calculate the transformation parameters between the radar mechanical axis coordinate system and the prism coordinate system using the least squares principle.

[0036] Step S5 involves high-precision calibration of the horn antenna position of the simulated radar target. This includes: connecting the horn antenna to a simulated signal source to radiate the target echo signal; the radar receiving the echo signal and controlling the mechanism to track the horn antenna, while simultaneously outputting the elevation and azimuth angles of the horn antenna in the radar's mechanical axis coordinate system; and setting up two theodolites near the radar, establishing a theodolite measurement system through mutual aiming and reference ruler aiming. Figure 5 As shown, the two-dimensional scanning frame is controlled to move the horn antenna to different positions. Two theodolites are used to measure the positions of the horn antenna and the target point on the back of the antenna in the theodolite measurement coordinate system. The radar measurement values ​​of the elevation angle and azimuth angle of the horn antenna at different positions are recorded.

[0037] Step S6 involves performing high-precision calibration of the radar's electrical axis and mechanical axis deviation, specifically including: using the target point coordinates on the back of the T-shaped fixture as a common point; transferring the position of the horn antenna in the theodolite coordinate system to the radar's mechanical axis coordinate system; mapping the geometric relationship to the elevation and azimuth angles of the mechanism to obtain calibration values; calculating the errors between the measured radar elevation and azimuth angles and the calibration values; the mean error is the error of the electrical axis deviating from the radar's mechanical axis; and the variance of the error is the radar's angle measurement accuracy. Figure 6As shown, the coordinates of the target point on the back of the T-shaped fixture are taken as the common point. After transferring the position of the horn antenna in the theodolite coordinate system to the position in the radar mechanical axis coordinate system, each horn point is connected to the origin of the radar mechanical axis coordinate system. The angle between the straight line and the YOX plane of the radar mechanical axis coordinate system is the elevation angle calibration value. The angle between each straight line and the ZOX plane of the radar mechanical axis coordinate system is the azimuth angle calibration value. The error between the measured values ​​of the radar elevation angle and azimuth angle and the calibration values ​​is calculated. The mean error is the error of the electric axis deviating from the radar mechanical axis, and the variance of the error is the radar angle measurement accuracy.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0039] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A high-precision electric shaft / mechanical shaft calibration method based on joint measurement, characterized in that, include: An electric and mechanical axis calibration system was built in a microwave anechoic chamber. The horn antenna of the simulated target was installed on a two-dimensional scanning frame. A cross target was attached to the front of the horn antenna, with the center of the cross target coinciding with the normal of the horn antenna. The radar antenna mechanism was installed on a T-shaped fixture, and a cubic prism was installed on the base of the radar antenna mechanism. The assembly of the radar antenna mechanism and the T-shaped fixture is placed horizontally, with the radar antenna normal facing upwards. Target points are attached to the side of the T-shaped fixture, and the position of the target points in the cubic prism coordinate system is measured using two theodolites. In front of the two-dimensional scanning frame, the assembly of the radar antenna mechanism and the T-shaped fixture is placed vertically with the normal of the radar antenna facing the two-dimensional scanning frame. Target points are attached to the edge of the radar antenna and the back of the T-shaped fixture. The radar antenna mechanism is controlled to rotate the azimuth and pitch axes. The position of the target points on the side and back of the T-shaped fixture in the radar mechanical axis coordinate system is obtained using a single-camera measurement system. Using the coordinates of the target point on the back of the T-shaped tooling as a common point, the transformation relationship between the radar mechanical axis coordinate system and the prism coordinate system is calculated. The horn antenna radiates the target echo signal. The radar receives the target echo signal and controls the mechanism to track the horn. At the same time, it outputs the elevation and azimuth angles of the horn antenna in the radar mechanical axis coordinate system. It controls the two-dimensional scanning frame to move the horn antenna to different positions. Two theodolites are used to measure the positions of the target point on the back of the horn antenna and the radar antenna in the theodolite measurement coordinate system. The measured values ​​of the elevation and azimuth angles in the radar mechanical axis coordinate system are recorded. Using the coordinates of the target point on the back of the T-shaped fixture as a common point, the position of the horn antenna in the theodolite coordinate system is transferred to the position in the radar mechanical axis coordinate system. Then, based on the geometric relationship, the elevation and azimuth angles of the radar antenna mechanism are mapped to obtain the calibration values. The error between the measured values ​​of the radar elevation and azimuth angles and the calibration values ​​is calculated. The mean error is the error of the electric axis deviating from the radar mechanical axis, and the variance of the error is the radar angle measurement accuracy.

2. The high-precision electric shaft / mechanical shaft calibration method based on joint measurement as described in claim 1, characterized in that, The movement of the two-dimensional scanning frame causes the horn antenna to move in both horizontal and vertical directions.

3. The high-precision electric shaft / mechanical shaft calibration method based on joint measurement as described in claim 1, characterized in that, The cubic prism coordinate system is established as follows: Set up two theodolites that have been aligned with each other, aim at the reference scale, add scale information to the theodolite measurement system, and establish the theodolite measurement system. In the theodolite surveying system, two theodolites are used to collimate the cube prism, determine the positional relationship between the cube prism coordinate system and the two theodolites, measure the crosshairs of the prism using the two theodolites, determine the origin of the prism coordinate system, and establish the prism coordinate system in the theodolite surveying system.

4. The high-precision electric shaft / mechanical shaft calibration method based on joint measurement as described in claim 1, characterized in that, The positions of the target points on the side and back of the T-shaped fixture in the radar mechanical axis coordinate system were obtained using a single-camera measurement system, including: A single-camera measurement system was used to monitor the position of the target point at the edge of the antenna, as well as the positions of the target points on the side and back of the T-shaped fixture. By fitting two circles to the position of the target point at the edge of the antenna, the straight line passing through the center of the circle and perpendicular to the plane of the circle is the radar mechanical axis, and the intersection of the two straight lines is the origin of the radar mechanical axis coordinate system, thus obtaining the position of the target point on the side and back of the T-shaped fixture in the radar mechanical axis coordinate system.

5. The high-precision electric shaft / mechanical shaft calibration method based on joint measurement as described in claim 1, characterized in that, The step of using the coordinates of the target point on the back of the T-shaped tooling as a common point to deduce the geometric relationship between the radar mechanical axis coordinate system and the prism coordinate system specifically includes: Select at least three common points that simultaneously possess both radar mechanical axis coordinate system and prism coordinate system, list the error equation for each common point, calculate the transformation parameters between radar mechanical axis coordinate system and prism coordinate system using the least squares principle, and based on the error between the transformed coordinate position and the measured coordinate position, eliminate common points with large errors, and calculate the transformation parameters between radar mechanical axis coordinate system and prism coordinate system for the remaining common points using the least squares principle.

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