Space target vision measurement method combined with acceleration drift estimation

Abstract

The invention relates to the technical field of spaceflight on-orbit close-range relative vision navigation, in particular to a space target vision measurement method combined with acceleration drift estimation, a tracking spacecraft is provided with an acceleration sensor and a camera, and the method comprises the following steps: S1, obtaining initial relative position information and relative speed information through a measurement system; s2, acquiring an acceleration value and a space target image in real time; s3, establishing a relative motion equation, substituting the obtained acceleration value, the relative position at the previous moment and the relative speed information into the relative motion equation, and calculating position information; and S4, calculating an error amount, and estimating the relative position information, the relative speed information and the error of the acceleration value in the kinetic equation through a filtering algorithm according to the error amount so as to correct a calculation result obtained in the kinetic equation, so that accurate positioning of the target spacecraft can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of aerospace on-orbit short-range relative visual navigation, and in particular to a space target visual measurement method combined with acceleration drift estimation. Background Art

[0002] Almost all on-orbit operation tasks involve guiding the target spacecraft through visual sensors and performing the operation tasks at the appropriate position. Due to the limited measurement range of ordinary CCD cameras, it is difficult to "see" the target at a distance of 100 meters. In this distance range, the ground tracking measurement system is limited by tracking conditions and cannot accurately measure the relative position of the target relative to the tracking spacecraft. In order to solve the relative measurement problem in the transition period between ground measurement and visual measurement, the current solution is to use relatively expensive equipment such as microwave radar or long focal length camera for measurement.

[0003] The application of deep learning-based target recognition technology in ground scenes is becoming more and more widespread. At present, it can already identify weak targets in remote sensing images. This technology is applied to space target recognition. The network is trained with ground simulation data and pseudo-real images, and the trained network is loaded into the onboard computing unit, which can quickly and accurately identify target spacecraft of different scales. However, when the distance between the target and the camera is large, the projection of the target on the imaging plane occupies very few pixels, making it difficult to separate the target spacecraft from the resident targets in the space background. Since the tracking spacecraft is in a maneuvering state, traditional methods such as trajectory association are no longer applicable. At this time, some prior information is needed to screen suspected targets. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a space target visual measurement method combined with acceleration drift estimation to achieve precise positioning of the target spacecraft.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A space target visual measurement method combined with acceleration drift estimation is proposed. The tracking spacecraft is equipped with an acceleration sensor and a camera.

[0007] The steps include:

[0008] S1: acquiring initial relative position information and relative velocity information through a measurement system, wherein the relative position information and relative velocity information are position and velocity information of the space target relative to the tracking spacecraft;

[0009] S2: acquiring the acceleration value and the space target image in real time; wherein the acceleration value is a parameter measured by the acceleration sensor; and the space target image is acquired by the camera;

[0010] S3: Establishing a relative motion equation, substituting the acceleration value at the current moment and the relative position and relative velocity information of a calculation cycle before the current moment into the relative motion equation, and calculating the position information, wherein the position information is the relative position of the space target relative to the tracking spacecraft at the current moment;

[0011] S4: Calculate the error amount, and estimate the errors of relative position information, relative velocity information and acceleration value in the dynamic equation through a filtering algorithm based on the error amount to correct the calculation result obtained in the dynamic equation, wherein the error amount is the error between the position information and the image position information, and the image position information is the position of the space target obtained based on the space target image.

[0012] Furthermore, in a space target visual measurement method combined with acceleration drift estimation in the present application, in step S3, the relative motion coordinate system between the tracking spacecraft and the space target is defined by the spacecraft orbit coordinate system, and the relative motion equation established in the relative motion coordinate system is as follows:

[0013]

[0014] Where n is the orbital angular velocity of the target spacecraft, f = [f x , f y , f z ] is the acceleration value;

[0015] The results obtained from the relative motion equation are as follows:

[0016]

[0017] Where T is the calculation period, [x k ,y k , z k ] is the position information of k at the current time, [Δx k-1 , Δy k-1 , Δz k-1 ] is the relative position error estimated by the filtering algorithm, is the relative speed of the space target at the current moment, is the relative velocity error estimated by the filtering algorithm, Δf = [Δf x , Δf y , Δf z ] is the accelerometer error estimated by the filtering algorithm, and k-1 represents the time of the previous calculation cycle of the current time k.

[0018] Furthermore, in a method for visual measurement of space targets combined with acceleration drift estimation in the present application, in step S4, the position information is converted into image coordinate system position information, and then the error between the image coordinate system position information and the image position information is calculated; the image coordinate system position information corresponds to the coordinate system of the space target image information.

[0019] Furthermore, a space target visual measurement method combined with acceleration drift estimation in the present application converts the position information into image coordinate system position information according to the following formula:

[0020]

[0021] in, is the spatial target position Pc in the camera coordinate system, which is obtained by converting the position information, f is the focal length of the camera, and (Cx, Cy) is the coordinate of the camera principal point in the imaging plane.

[0022] Optionally, a space target visual measurement method combined with acceleration drift estimation in the present application converts the space target position information P in the orbital coordinate system into: H Convert to the spatial target position Pc in the camera coordinate system:

[0023]

[0024] Assuming that the optical axis of the camera is parallel to the Y direction of the orbital coordinate system, and the x-axis and y-axis of the camera plane are consistent with the X and Z directions of the orbital coordinate system, the attitude transformation matrix from the camera coordinate system to the orbital coordinate system is:

[0025] Optionally, a space target visual measurement method combined with acceleration drift estimation in the present application converts the position information P into H Convert to the spatial target position Pc in the camera coordinate system:

[0026]

[0027] in, The camera coordinate system is aligned with the tracking spacecraft body coordinate system according to the attitude matrix of the tracking spacecraft body coordinate system relative to the orbit coordinate system measured by the attitude measurement system.

[0028] Furthermore, in a space target visual measurement method combined with acceleration drift estimation in the present application, the error MSE between the position information and the image position information is obtained by the following formula:

[0029]

[0030] Among them, (u,v) is the image position information, is the image coordinate system position information.

[0031] Furthermore, in a space target visual measurement method combined with acceleration drift estimation in the present application, the acquired space target image information is input into a preset target detection network to output a target detection result; if multiple target detection results are output, only the target detection result closest to the predicted position is retained, and the center position of the space target is calculated as the image position information based on the target detection result. As a preferred solution of the present application, the target detection network can be completed by adding a small detection head to a general target detection network, or a Transformer-type network can be used.

[0032] It can be seen from the above technical solution that the present invention has the following beneficial effects:

[0033] The present invention provides a space target visual measurement method combined with acceleration drift estimation, which uses an accelerometer to measure and track the maneuvering acceleration of a spacecraft, estimates the relative position of the target spacecraft through the relative motion equation, and estimates the acceleration drift through filtering. When the target is far away from the camera, the target spacecraft can be separated from the resident targets in the space background, realizing a visual measurement method that integrates acceleration drift estimation with deep learning technology, achieving the effect of increasing the measurement range of the camera, thereby realizing accurate positioning of the target spacecraft. At the same time, the error estimation of the acceleration is performed through filtering, which can improve the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a diagram that defines the orbital coordinate system of the space target and tracking spacecraft in an embodiment of the present application. DETAILED DESCRIPTION

[0035] This embodiment provides a space target visual measurement method combined with acceleration drift estimation. An acceleration sensor and a camera are provided on the tracking spacecraft.

[0036] The steps include:

[0037] S1: Acquire initial relative position information and relative speed information through a measurement system, wherein the relative position information and relative speed information are the position and speed information of the space target relative to the tracking spacecraft; the specific measurement system may be a GPS or other ground measurement system.

[0038] S2: acquiring the acceleration value and the space target image in real time; wherein the acceleration value is a parameter measured by the acceleration sensor; and the space target image is acquired by the camera;

[0039] S3: Establishing a relative motion equation, substituting the acceleration value at the current moment and the relative position and relative velocity information of a calculation cycle before the current moment into the relative motion equation, and calculating the position information, wherein the position information is the relative position of the space target relative to the tracking spacecraft at the current moment;

[0040] S4: Calculate the error amount, and estimate the errors of relative position information, relative velocity information and acceleration value in the dynamic equation through a filtering algorithm based on the error amount to correct the calculation result obtained in the dynamic equation, wherein the error amount is the error between the position information and the image position information, and the image position information is the position of the space target obtained based on the space target image.

[0041] In this embodiment, the space target is an on-orbit spacecraft.

[0042] In this embodiment, in step S2, the error of the measurement data is estimated by a filtering algorithm to correct the calculation result obtained in the dynamic equation.

[0043] In this embodiment, in step S2, the relative motion coordinate system of the tracking spacecraft and the space target is defined by the spacecraft orbit coordinate system, that is, Figure 1 As shown, the origin of the orbital coordinate system of the space target is fixedly connected to the center of mass of the space target and moves along the orbit with it. The X-axis coincides with the center of the earth vector of the space target. The Y-axis is perpendicular to the X-axis in the orbital plane and points to the positive direction of motion. The Z-axis is determined by the right-hand rule. The relative motion equation established in the relative motion coordinate system is as follows:

[0044]

[0045] Where n is the orbital angular velocity of the target spacecraft, f = [f x , f y , f z ] is the acceleration value;

[0046] The results obtained from the relative motion equation are as follows:

[0047]

[0048] Where T is the calculation period, [x k ,y k , z k ] is the position information at the current time k, [Δx k-1 , Δy k-1 , Δz k -1 ] is the relative position error estimated by the filtering algorithm, is the relative speed of the space target at the current moment, is the relative velocity error estimated by the filtering algorithm, Δf = [Δf x , Δf y , Δf z ] is the accelerometer error estimated by the filtering algorithm, and k-1 represents the time of the previous calculation cycle of the current time k.

[0049] In this embodiment, in step S3, after the position information is converted into image coordinate system position information, the error between the image coordinate system position information and the image position information is calculated; the image coordinate system position information corresponds to the coordinate system of the space target image information.

[0050] In this embodiment, the position information is converted into image coordinate system position information according to the following formula:

[0051]

[0052] in, is the spatial target position Pc in the camera coordinate system, which is obtained by converting the position information, f is the focal length of the camera, and (Cx, Cy) is the coordinate of the camera principal point in the imaging plane.

[0053] In one embodiment, the spatial target position information P in the orbital coordinate system is converted into H Convert to the spatial target position Pc in the camera coordinate system:

[0054]

[0055] Assuming that the optical axis of the camera is parallel to the Y direction of the orbital coordinate system, and the x-axis and y-axis of the camera plane are consistent with the X and Z directions of the orbital coordinate system, the attitude transformation matrix from the camera coordinate system to the orbital coordinate system is:

[0056] In another embodiment, the position information P is converted into H Convert to the spatial target position Pc in the camera coordinate system:

[0057]

[0058] in, The camera coordinate system is aligned with the tracking spacecraft body coordinate system according to the attitude matrix of the tracking spacecraft body coordinate system relative to the orbit coordinate system measured by the attitude measurement system.

[0059] In this embodiment, the error MSE between the position information and the image position information is obtained by the following formula:

[0060]

[0061] Wherein, (u, v) is the image position information, is the image coordinate system position information.

[0062] In this embodiment, the acquired space target image information is input into a preset target detection network to output the target detection result; if multiple target detection results are output, only the target detection result closest to the predicted position is retained, and the center position of the space target is calculated as the image position information according to the target detection result. Among them, the target detection network can be completed by adding a small detection head to a general target detection network, or a Transformer network can be used. In this embodiment, the yolov81 plus small detection head solution is used in the application process. Specifically, a GEO target detection method based on improved yolov8 is disclosed in the Chinese invention patent with the publication number CN118918312A. The original yolov81 has 3 detection heads, and the sizes are 32ⅹ32, 16ⅹ16, and 8ⅹ8 respectively. On this basis, a small detection head is added, and the size is 4ⅹ4. The modified network can be used for multi-scale target detection.

[0063] Based on the above method, through simulation verification, a binocular camera is used to measure a target spacecraft with a diameter of one meter. The detection accuracy is 100% within a distance of 60 meters, 98% at 60-70 meters, 80% at 70-80 meters, and 60% at 80-100 meters. The detection accuracy of the range of 60 meters to 100 meters is greater than 90% when the method described in this embodiment is used for measurement.

[0064] The technical principles of the present invention are described above in conjunction with specific embodiments. These descriptions are only for explaining the principles of the present invention and cannot be interpreted as limiting the scope of protection of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific implementations of the present invention without creative work, and these methods will fall within the scope of protection of the present invention.

Claims

1. A space target visual measurement method combined with acceleration drift estimation, characterized in that: The tracking spacecraft is equipped with acceleration sensors and cameras. The steps include: S1: acquiring initial relative position information and relative velocity information through a measurement system, wherein the relative position information and relative velocity information are position and velocity information of the space target relative to the tracking spacecraft; S2: acquiring the acceleration value and the space target image in real time; wherein the acceleration value is a parameter measured by the acceleration sensor; and the space target image is acquired by the camera; S3: Establishing a relative motion equation, substituting the acceleration value at the current moment and the relative position and relative velocity information of a calculation cycle before the current moment into the relative motion equation, and calculating the position information, wherein the position information is the relative position of the space target relative to the tracking spacecraft at the current moment; S4: Calculate the error amount, and estimate the errors of relative position information, relative velocity information and acceleration value in the dynamic equation through a filtering algorithm based on the error amount to correct the calculation result obtained in the dynamic equation, wherein the error amount is the error between the position information and the image position information, and the image position information is the position of the space target obtained based on the space target image.

2. The method for visual measurement of space targets combined with acceleration drift estimation according to claim 1, characterized in that: In step S3, the relative motion coordinate system between the tracking spacecraft and the space target is defined by the spacecraft orbit coordinate system. The relative motion equation established in the relative motion coordinate system is as follows: Where n is the orbital angular velocity of the target spacecraft, f = [f x , f y , f z ] is the acceleration value; The results obtained from the relative motion equation are as follows: Where T is the calculation period, [x k ,y k , z k ] is the position information of k at the current time, [Δx k-1 , Δy k-1 , Δz k-1 ] is the relative position error estimated by the filtering algorithm, is the relative speed of the space target at the current time k, is the relative velocity error estimated by the filtering algorithm, Δf = [Δf x , Δf y , Δf z ] is the acceleration error estimated by the filtering algorithm, and k-1 represents the moment of the previous calculation cycle of the current moment k.

3. The method for visual measurement of space targets combined with acceleration drift estimation according to claim 1, characterized in that: In step S4, after the position information is converted into image coordinate system position information, the error between the image coordinate system position information and the image position information is calculated; the image coordinate system position information corresponds to the coordinate system of the space target image information.

4. The method for visual measurement of space targets combined with acceleration drift estimation according to claim 3, characterized in that: The position information is converted into image coordinate system position information according to the following formula: in, is the spatial target position Pc in the camera coordinate system, which is obtained by converting the position information, f is the focal length of the camera, and (Cx, Cy) is the coordinate of the camera principal point in the imaging plane.

5. The method for visual measurement of space targets combined with acceleration drift estimation according to claim 4, characterized in that: The spatial target position information P in the orbital coordinate system is obtained by the following formula H Convert to the spatial target position Pc in the camera coordinate system: Assuming that the optical axis of the camera is parallel to the Y direction of the orbital coordinate system, and the x-axis and y-axis of the camera plane are consistent with the X and Z directions of the orbital coordinate system, the attitude transformation matrix from the camera coordinate system to the orbital coordinate system is:

6. The method for visual measurement of space targets combined with acceleration drift estimation according to claim 5, characterized in that: The position information P is expressed as follows: H Convert to the spatial target position Pc in the camera coordinate system: in, The camera coordinate system is aligned with the tracking spacecraft body coordinate system according to the attitude matrix of the tracking spacecraft body coordinate system relative to the orbit coordinate system measured by the attitude measurement system.

7. The method for visual measurement of space targets combined with acceleration drift estimation according to claim 4, characterized in that: The error MSE between the position information and the image position information is obtained by the following formula: Wherein, (u, v) is the image position information, is the image coordinate system position information.

8. The method for visual measurement of space targets combined with acceleration drift estimation according to claim 1, characterized in that: The acquired space target image information is input into a preset target detection network to output a target detection result; If multiple target detection results are output, only the target detection result closest to the predicted position is retained, and the center position of the space target is calculated based on the target detection result as the image position information.

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