Space target closed-loop tracking method and device, space target tracking imaging system

Abstract

This invention relates to the field of space target tracking technology, providing a space target closed-loop tracking method and apparatus, and a space target tracking imaging system. The method includes: placing a space target within the field of view of a guide mirror; adjusting a motor using optical tracking to ensure the space target remains continuously within the guide mirror's field of view, specifically including: acquiring the position of the space target within the guide mirror's field of view; calculating pixel error values ​​at predetermined time intervals; if the pixel error value in a first direction or a second direction is greater than or equal to a specified threshold, then converting the pixel error value in the first direction or the pixel error value in the second direction into a motion direction and velocity magnitude using a proportional method to adjust the motor; otherwise, converting the pixel error value in the first direction or the pixel error value in the second direction into a motion direction and velocity magnitude using a proportional and integral method to adjust the motor. This solution can achieve closed-loop tracking of space targets, ensuring the execution of subsequent tasks.

Description

Technical Field

[0001] This invention relates to the field of space target tracking technology, and in particular to a space target closed-loop tracking method and apparatus, and a space target tracking imaging system. Background Technology

[0002] As human space activities continue to develop, there is a need to track and observe space targets such as spacecraft and celestial bodies.

[0003] Most commercially available systems use equatorial mounts for observation and theoretical trajectory guidance during tracking. This approach involves open-loop control throughout the entire process, which has the following drawbacks: First, during tracking, the equatorial mount cannot lock the target in the center of the guiding star's field of view, resulting in pixel deviation errors within the field of view. Second, the theoretically guided trajectory has a time delay, which can cause path deviations and tracking errors. If used during the rocket's ascent phase, if the trajectory deviates from the ballistic trajectory, the open-loop system cannot determine the magnitude of the error, leading to tracking failure.

[0004] Therefore, there is an urgent need to develop a closed-loop tracking method and device for space targets, as well as a space target tracking imaging system, which can realize closed-loop tracking of space targets and provide a guarantee for the execution of subsequent missions. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for closed-loop tracking of space targets, and a space target tracking imaging system, which can realize closed-loop tracking of space targets and provide a guarantee for the execution of subsequent tasks.

[0006] To address the aforementioned technical problems, as one aspect of the present invention, a closed-loop tracking method for space targets is provided. A guide mirror is fixed to a first-direction turntable or a second-direction turntable, the first-direction turntable and the second-direction turntable are fixedly connected, and both the first-direction turntable and the second-direction turntable include a motor. The method includes the following steps:

[0007] Place the space target within the field of view of the guide mirror;

[0008] The motor is adjusted using optical tracking to keep the space target continuously within the field of view of the guide mirror;

[0009] The method of adjusting the motor using optical tracking to keep the space target continuously within the field of view of the guide mirror includes:

[0010] Acquire the position of the space target in the guide scope's field of view;

[0011] Calculate the pixel error value in the first direction or the pixel error value in the second direction at predetermined intervals;

[0012] If the pixel error value in the first direction or the pixel error value in the second direction is greater than or equal to a specified threshold, the pixel error value in the first direction or the pixel error value in the second direction is converted into the motion direction and speed magnitude by means of a ratio to adjust the motor.

[0013] If the pixel error value in the first direction and the pixel error value in the second direction are both less than a specified threshold, then the pixel error value in the first direction or the pixel error value in the second direction is converted into the direction of motion and speed of the motor through proportional and integral methods.

[0014] According to an exemplary embodiment of the present invention, the first direction is the width direction of the guide mirror, and the second direction is the height direction of the guide mirror.

[0015] According to an exemplary embodiment of the present invention, the method for placing a space target within the field of view of a guide mirror includes: placing the space target within the field of view of the guide mirror using a digital tracking method.

[0016] According to an exemplary embodiment of the present invention, the data tracking method includes: acquiring the ephemeris file of the space target, determining the position of the space target based on the ephemeris file, and controlling a motor to point the guide mirror at the space target based on the position of the space target.

[0017] According to an exemplary embodiment of the present invention, the method for calculating the pixel error value in the first direction and the pixel error value in the second direction includes:

[0018] First, calculate the field of view of the guide mirror. Then, calculate the field of view of each pixel based on the field of view of the guide mirror. Finally, calculate the pixel error value in the first direction and the pixel error value in the second direction based on the field of view of each pixel.

[0019] According to an exemplary embodiment of the present invention, the field of view of the guide mirror is calculated using the following formula:

[0020] θ w2 = 2arctan(w² / 2f²);

[0021] θ h2 = 2arctan(h² / 2f²);

[0022] Where, θ w2 θ represents the width of the guide scope's field of view. h2 w2 represents the height field of view of guide mirror 11, w2 represents the CCD width of guide mirror, h2 represents the CCD height of guide mirror, and f2 represents the focal length of guide mirror.

[0023] According to an exemplary embodiment of the present invention, the calculation of the field of view corresponding to each pixel based on the field of view of the guide mirror is performed using the following formula:

[0024] θw′ =θ w2 / w2;

[0025] θ h′ =θ h2 / h2;

[0026] Where, θ w′ θ represents the field of view in pixels. h′ θ represents the height pixel field of view. w2 θ represents the width of the guide scope's field of view. h2 w2 represents the height field of view of the guide mirror, w2 represents the CCD width of the guide mirror, and h2 represents the CCD height of the guide mirror.

[0027] According to an exemplary embodiment of the present invention, the pixel error values ​​in the first and second directions are calculated based on the field of view corresponding to each pixel using the following formula:

[0028] Err Az = (w² / 2 - centroidX) × θ w′ ;

[0029] Err El = -(h² / 2 - centroidY) × θ h′ ;

[0030] Among them, Err Az Err represents the pixel error value in the first direction. El The pixel error value represents the second direction. centroidX represents the coordinates of the space target in the width direction within the guide scope's field of view, centroidY represents the coordinates of the space target in the height direction within the guide scope's field of view, and θ... w′ θ represents the field of view in pixels. h′ w2 represents the height pixel field of view, w2 represents the CCD width of the guide mirror, and h2 represents the CCD height of the guide mirror.

[0031] According to an exemplary embodiment of the present invention, the motor that converts the pixel error value in the first direction or the pixel error value in the second direction into the motion direction and speed using a proportional method employs the following formula:

[0032] P El =Err El ×Kp1;

[0033] P Az =Err Az ×Kp2;

[0034] Among them, P Az P represents the proportional velocity in the first direction. ElKp1 represents the proportional velocity in the second direction, Kp2 represents the proportional coefficient in the second direction, and Err represents the proportional coefficient in the first direction. Az Err represents the pixel error value in the first direction. El This represents the pixel error value in the second direction.

[0035] According to an exemplary embodiment of the present invention, a method for adjusting a motor by converting pixel error values ​​in a first direction or a second direction into motion direction and speed using a proportional and integral method is provided.

[0036] The cumulative error is obtained based on the pixel error value:

[0037] I El =∑Err El ×Ki1;

[0038] I Az =∑Err Az ×Ki2;

[0039] Among them, I El I represents the cumulative error in the second direction. Az Ki1 represents the cumulative error in the first direction, Ki2 represents the integral coefficient in the second direction, and Err represents the integral coefficient in the first direction. Az Err represents the pixel error value in the first direction. El This represents the pixel error value in the second direction;

[0040] The velocity and direction of motion are obtained from the cumulative error:

[0041] PI El =P El +I El ;

[0042] PI Az =P Az +I Az ;

[0043] Among them, PI El PI represents the proportional-integral velocity in the second direction. Az I represents the proportional-integral velocity in the first direction. El I represents the cumulative error in the second direction. Az P represents the cumulative error in the first direction. Az P represents the proportional velocity in the first direction. El This represents the proportional velocity in the second direction.

[0044] As a second aspect of the present invention, a space target closed-loop tracking device is provided, which can perform the aforementioned space target closed-loop tracking method.

[0045] According to an exemplary embodiment of the present invention, the space target closed-loop tracking device includes:

[0046] The first-direction turntable includes a motor;

[0047] The second-direction turntable is fixedly connected to the first-direction turntable and includes a motor;

[0048] A guide scope, fixed on a first-direction turntable or a second-direction turntable, is used to photograph space targets;

[0049] The tracking and processing module is communicatively connected to the guide mirror, the motor of the first direction turntable, and the motor of the second direction turntable. It is used to acquire data captured by the guide mirror, process the data that the motor needs to rotate, and send the data that the motor needs to rotate to the motor.

[0050] According to an exemplary embodiment of the present invention, the tracking processing module is used to place a space target within the field of view of the guide mirror;

[0051] The motor is adjusted using optical tracking to keep the space target continuously within the field of view of the guide mirror;

[0052] The method of adjusting the motor using optical tracking to keep the space target continuously within the field of view of the guide mirror includes:

[0053] Acquire the position of the space target in the guide scope's field of view;

[0054] Calculate the pixel error value in the first direction or the pixel error value in the second direction at predetermined intervals;

[0055] If the pixel error value in the first direction or the pixel error value in the second direction is greater than or equal to a specified threshold, the pixel error value in the first direction or the pixel error value in the second direction is converted into the motion direction and speed magnitude by means of a ratio to adjust the motor.

[0056] If the pixel error value in the first direction and the pixel error value in the second direction are both less than a specified threshold, then the pixel error value in the first direction or the pixel error value in the second direction is converted into the direction of motion and speed of the motor through proportional and integral methods.

[0057] As a third aspect of the present invention, a space target tracking imaging system is provided, comprising:

[0058] The aforementioned closed-loop tracking device for space targets;

[0059] Imaging devices;

[0060] The imaging device is fixed on the first or second direction turntable of the space target closed-loop tracking device.

[0061] According to an exemplary embodiment of the present invention, the imaging device is one or more, and the imaging device includes an optical system and / or an infrared system.

[0062] The beneficial effects of this invention are:

[0063] This scheme continuously acquires the position of the space target within the field of view of the guide mirror and adjusts the motor accordingly, so that the space target continuously approaches the center point of the guide mirror's field of view, making the pixels of the space target observed by the imaging device stable. At the same time, as it is a closed-loop tracking system, it can continuously and stably track the space target, ensuring the execution of subsequent missions. Attached Figure Description

[0064] Figure 1 A schematic diagram of a space target tracking and imaging system is shown.

[0065] Figure 2 A schematic diagram of the structure of a space target tracking imaging system (from another angle).

[0066] Figure 3 A schematic diagram of a space target tracking and imaging system is shown.

[0067] Figure 4 The diagram illustrates the steps of a closed-loop tracking method for space targets.

[0068] Figure 5 The schematic diagram illustrates the PI control flowchart of the tracking system.

[0069] Figure 6 The diagram illustrates the results of the analysis of star pointing accuracy by a space target tracking imaging system.

[0070] Figure 7 The diagram illustrates the analysis results of the pointing accuracy of a space target tracking imaging system for low-speed moving targets.

[0071] Figure 8 The diagram illustrates the analysis results of the pointing accuracy of a space target tracking imaging system for high-speed moving targets.

[0072] Figure 9 The illustration shows a visible light image of the International Space Station.

[0073] Figure 10 The illustration shows a frame overlay effect of the International Space Station.

[0074] Among them, 1—space target closed-loop tracking device, 11—guide mirror, 12—first direction turntable, 13—second direction turntable, 14—turntable tripod, 2—imaging device, 21—optical system, 22—infrared system. Detailed Implementation

[0075] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0076] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0077] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0078] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0079] It should be understood that although the terms first, second, third, etc., may be used herein to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Therefore, the first component discussed below may be referred to as the second component without departing from the teachings of this application. As used herein, the term "and / or" includes all combinations of any one and more of the associated listed items.

[0080] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily essential for implementing this application, and therefore cannot be used to limit the scope of protection of this application.

[0081] As a first embodiment of the present invention, a space target closed-loop tracking device 1 is provided, such as... Figure 1 and Figure 2As shown, it includes a guide mirror 11, a first-direction turntable 12, a second-direction turntable 13, a turntable tripod 14, and a tracking processing module 15.

[0082] The first-direction turntable 12 and the second-direction turntable 13 are fixedly connected and can rotate around the pitch and azimuth directions. The first-direction turntable 12 and the second-direction turntable 13 can be combined into an AE structure turntable or an XY structure turntable. The first and second directions are perpendicular. Both the first-direction turntable 12 and the second-direction turntable 13 include motors that drive the turntables to rotate. The guide mirror 11 is fixed on the first-direction turntable 12 or the second-direction turntable 13 and is used to photograph space targets. The tracking and processing module 15 is communicatively connected to the guide mirror 11, the first-direction turntable 12, and the second-direction turntable 13. It is used to acquire the data captured by the guide mirror 11, process it to obtain the data that the motors of the first-direction turntable 12 and the second-direction turntable 13 need to rotate, and send the data that needs to be rotated to the first-direction turntable 12 and the second-direction turntable 13. The turntable tripod 14 is fixed below the first-direction turntable 12 or the second-direction turntable 13 and is used to support the guide mirror 11, the first-direction turntable 12, and the second-direction turntable 13.

[0083] The guide mirror 11 uses the ASI224, and its CCD sensor parameters are shown in Table 1.

[0084] Table 1

[0085] Resolution / pixel pitch 1304×976 / 17um Pixel size 3.75um Image area 4.8mm×3.6mm weight 100g (excluding guide scope)

[0086] This scheme continuously optimizes the direction of rotation by using a guide mirror 11 and a tracking processing module 15, ensuring that the space target remains within the field of view of the guide mirror 11, thereby achieving continuous and stable tracking of the space target and providing a guarantee for the execution of subsequent missions.

[0087] As a second embodiment of the present invention, a space target imaging system is provided, such as... Figure 1 and Figure 2 As shown, it includes: a space target closed-loop tracking device 1 and an imaging device 2 according to the first embodiment.

[0088] The imaging device 2 may be one or more, including an optical system 21 and an infrared system 22. The optical system 21 is mainly used for observation during the day and can be a visible light telescope. The infrared system 22 is mainly used for observation at night and can be an infrared imager. The imaging device 2 is fixed on a first-direction turntable 12 or a second-direction turntable 13.

[0089] like Figure 3 As shown, the space target tracking and imaging system includes an algorithm layer, a software layer, a system layer, and a product layer.

[0090] The algorithm layer includes target recognition algorithms based on traditional image processing, target recognition algorithms based on convolutional networks, autofocus algorithms, optical (binocular) measurement algorithms, imaging model establishment, target acquisition algorithms, and image recognition algorithms. Among them, the target recognition algorithms based on traditional image processing, the target recognition algorithms based on convolutional networks, the autofocus algorithms, the optical (binocular) measurement algorithms, and the imaging model establishment algorithms process data from the optical system, while the optical (binocular) measurement algorithms, the imaging model establishment algorithms, the target acquisition algorithms, and the image recognition algorithms process data from the infrared system.

[0091] The software layer includes optical system tracking and video quality optimization software, infrared system image acquisition and tracking software, and intelligent decision-making and scheduling software.

[0092] The system layer includes an optical imaging system, an optical focusing mechanism, an infrared imaging system, a turntable servo system, a power supply and distribution system, and a data interaction and storage system.

[0093] The product layer consists of a dual-optical intelligent tracking device based on visible light and infrared light, which includes: a space target closed-loop tracking device 1 and an imaging device 2.

[0094] The optical system 21 can use the parameters shown in Table 2.

[0095] Table 2

[0096] Optical design Schmidt-Cassegrain backflip caliber 254mm focal length Fixed lens 2500mm (f1)

[0097] The camera video parameters of the optical system can be as shown in Table 3.

[0098] Table 3

[0099] resolution 1920×1080 Frame rate 30 CCD size 35.9×24mm(w1×h1)

[0100] Optical system with 21 fields of view:

[0101] θ h = 2arctan(w1 / 2f1);

[0102] θ v = 2arctan(h1 / 2f1).

[0103] Where, θ h The width of the field of view of the optical system 21 is θ, preferably 0.823°. v The height field of view of the optical system 21 is represented, preferably 0.555°; w1 represents the CCD width of the optical system 21, h1 represents the CCD height of the optical system 21, and f1 represents the focal length of the optical system.

[0104] Optical axis alignment: The guide mirror 11 is fixed on the optical system 21 to ensure optical axis alignment, that is, the coordinates of the space target in the guide field of view are consistent with the visible light field of view and the infrared field of view.

[0105] The space target is stably tracked by the space target closed-loop tracking device 1, so that the space target is continuously in the imaging device 2, ensuring that the imaging device 2 can always stably observe the space target.

[0106] As a third embodiment of the present invention, a space target closed-loop tracking method is provided, which uses the space target closed-loop tracking device 1 of the first embodiment to achieve stable tracking and improve target imaging quality. The space target closed-loop tracking method, such as... Figure 4 As shown, it includes the following steps:

[0107] S1: Place the space target within the field of view of guide mirror 11.

[0108] This step is completed by the tracking processing module 15.

[0109] After placing the space target in a straight line within the field of view of the guide mirror 11, the system is first calibrated to north.

[0110] System North Calibration: By presetting the position, input the azimuth Az1 and altitude of a planet (e.g., Jupiter, the Moon), and point the first direction turntable 12 and the second direction turntable 13 towards the planet. Adjust the angles of the first direction turntable 12 and the second direction turntable 13 (i.e., the azimuth and elevation angles of the guide mirror 11) so that the planet is at the center of the field of view of the guide mirror 11. Record the azimuth angle Az2 of the guide mirror 11 at this time. Then, the system north offset angle OffsetNor = Az2 - Az1. In subsequent turntable movements, the system north offset angle needs to be used to compensate for the turntable movement.

[0111] Methods for placing a space target within the field of view of the guide mirror 11 include telemetry (TLE) tracking and manual preset, both of which can capture the space target. As a preferred embodiment, the method for placing the space target within the field of view of the guide mirror includes: using telemetry (TLE) tracking to place the space target within the field of view of the guide mirror.

[0112] The data tracking method includes: acquiring the ephemeris file of the space target, determining the position of the space target based on the ephemeris file, and controlling the motor to point the guide mirror 11 at the space target based on the position of the space target.

[0113] The ephemeris file contains the calculated positions of space targets, but this file is outdated, so the calculated positions are not accurate. This method is initially used for coarse alignment, with further adjustments made during subsequent tracking.

[0114] S2: The motor 13 is adjusted by optical tracking so that the space target remains within the field of view of the guide mirror 11.

[0115] This step is completed by the tracking processing module 15.

[0116] Although step S1 places the space target inside the guide mirror 11, it is generally far from the center of the field of view of the guide mirror 11. Therefore, the space target needs to be moved to the center of the field of view of the guide mirror 11 to ensure that subsequent tracking can be aligned.

[0117] like Figure 5 As shown, the method of adjusting the motor using optical tracking to keep the space target continuously within the field of view of the guide mirror 11 includes:

[0118] Acquire the position of the space target in the field of view of guide mirror 11;

[0119] Calculate the pixel error value in the first direction or the pixel error value in the second direction at predetermined intervals;

[0120] If the pixel error value in the first direction or the pixel error value in the second direction is greater than or equal to a specified threshold, the pixel error value in the first direction or the pixel error value in the second direction is converted into the motion direction and speed magnitude by means of a ratio to adjust the motor.

[0121] If the pixel error value in the first direction and the pixel error value in the second direction are both less than a specified threshold, then the pixel error value in the first direction or the pixel error value in the second direction is converted into the direction of motion and speed of the motor through proportional and integral methods.

[0122] Methods for obtaining the position of a space target in the field of view of guide scope 11 include:

[0123] The YOLO neural network is used to identify the position of the space target in the field of view of the guide mirror 11. The position includes the position of the center point of the space target in the width direction and the height direction in the field of view (the CCD of the guide mirror 11), i.e. (centroidX, centroidY).

[0124] If the space target cannot be identified, the motor is adjusted using digital tracking to keep the space target continuously within the field of view of the guide mirror 11. If the weather is unfavorable during tracking, and the space target is blocked by clouds, obstacles, etc., and cannot be identified, the system is temporarily switched to digital tracking. Once the space target can be identified, the system is immediately switched to optical tracking (using the guide mirror 11 for tracking).

[0125] The scheduled time uses the frame rate of Guide Mirror 11.

[0126] Methods for calculating pixel error values ​​in a first direction or a second direction include:

[0127] First, calculate the field of view of the guide mirror 11. Then, calculate the field of view of each pixel based on the field of view of the guide mirror 11. Finally, calculate the pixel error values ​​in the first and second directions based on the field of view of each pixel.

[0128] Preferably, the first direction is the width direction of the guide mirror 11, and the second direction is the height direction of the guide mirror 12.

[0129] The field of view of guide mirror 11 is calculated using the following formula:

[0130] θ w2 = 2arctan(w² / 2f²);

[0131] θ h2 = 2arctan(h² / 2f²);

[0132] Where, θ w2 θ represents the width of the field of view of guide mirror 11. h2 w2 represents the height field of view of the guide mirror 11, w2 represents the CCD width of the guide mirror 11, h2 represents the CCD height of the guide mirror 11, and f2 represents the focal length of the guide mirror 11.

[0133] The SDK calls a 640×480 (w2×h2) resolution guide scope with a field of view of f = 24mm. θ w2 Preferably 5.620°, θ h2 The preferred angle is 4.225°. SDK: Software Development Kit is generally a collection of development tools used by software engineers to create application software for specific software packages, software frameworks, hardware platforms, operating systems, etc.

[0134] The field of view of the guide mirror 11 is calculated based on the pinhole imaging principle.

[0135] The principle of pinhole imaging: tan(field angle / 2) = (CCD film width / 2) / focal length.

[0136] The field of view for each pixel is calculated based on the field of view of the guide mirror 11 using the following formula:

[0137] θ w′ =θ w2 / w2;

[0138] θ h′ =θ h2 / h2;

[0139] Where, θ w′ θ represents the field of view in pixels. h′ θ represents the height pixel field of view. w2 θ represents the width of the field of view of guide mirror 11.h2 w2 represents the height field of view of the guide mirror 11, w2 represents the CCD width of the guide mirror 11, and h2 represents the CCD height of the guide mirror 11.

[0140] The SDK calls a 640×480 (w2×h2) resolution guide scope with a field of view of f = 24mm. θ w′ Preferably, θ is 0.0088°. h′ The preferred value is 0.0088°.

[0141] The pixel error values ​​in the first and second directions are calculated based on the field of view corresponding to each pixel using the following formula:

[0142] Err Az = (w² / 2 - centroidX) × θ w′ ;

[0143] Err El = -(h² / 2 - centroidY) × θ h′ ;

[0144] Among them, Err Az Err represents the pixel error value in the first direction. El The pixel error value represents the second direction. centroidX represents the coordinates of the space target in the width direction within the field of view of the guide mirror 11, centroidY represents the coordinates of the space target in the height direction within the field of view of the guide mirror 11, and θ represents the pixel error value in the second direction. w′ θ represents the field of view in pixels. h′ w2 represents the height pixel field of view, w2 represents the CCD width of guide mirror 11, and h2 represents the CCD height of guide mirror 11.

[0145] Preferably, the first direction is the pitch direction and the second direction is the azimuth direction.

[0146] The predetermined threshold is preferably 0.4°.

[0147] The pixel error value in the first direction or the pixel error value in the second direction is converted into the direction of motion and speed using a proportional method. The motor is then adjusted using the following formula:

[0148] P El =Err El ×Kp1;

[0149] P Az =Err Az ×Kp2;

[0150] Among them, P Az P represents the proportional velocity in the first direction. ElKp1 represents the proportional velocity in the second direction, Kp2 represents the proportional coefficient in the second direction, and Err represents the proportional coefficient in the first direction. Az Err represents the pixel error value in the first direction. El This represents the pixel error value in the second direction. The proportional velocity value is a signed numerical value; a negative value indicates the opposite direction of motion. The absolute value of the proportional velocity is the magnitude of the velocity. The farther the spatial target is from the center of the field of view in a given direction, the larger the pixel error value and the greater the corresponding velocity. Kp1 and Kp2 are both positive constants.

[0151] A method for adjusting the motor by converting the pixel error value in the first direction or the pixel error value in the second direction into the direction and speed of motion using proportional and integral methods:

[0152] The cumulative error is obtained based on the pixel error value:

[0153] I El =∑Err El ×Ki1;

[0154] I Az =∑Err Az ×Ki2;

[0155] Among them, I El I represents the cumulative error in the second direction. Az Ki1 represents the cumulative error in the first direction, Ki2 represents the integral coefficient in the second direction, and Err represents the integral coefficient in the first direction. Az Err represents the pixel error value in the first direction. El This represents the pixel error value in the second direction. Integral control considers past errors; therefore, it multiplies the sum of past error values ​​(error sum) by positive constants Ki1 and Ki2. Both Ki1 and Ki2 are positive constants.

[0156] The velocity and direction of motion are obtained from the cumulative error:

[0157] PI El =P El +I El ;

[0158] PI Az =P Az +I Az ;

[0159] Among them, PI El PI represents the proportional-integral velocity in the second direction. Az I represents the proportional-integral velocity in the first direction. ElI represents the cumulative error in the second direction. Az P represents the cumulative error in the first direction. Az P represents the proportional velocity in the first direction. El This represents the proportional velocity in the second direction. The value of the proportional-integral velocity is a numerical value with a positive or negative sign; if it is negative, the direction of motion is opposite. The absolute value of the proportional-integral velocity is the magnitude of the velocity.

[0160] By feeding back the proportional or proportional-integral velocity values ​​in each direction to the corresponding motors, the motors adjust the turntable angle, thus keeping the space target near the center of the field of view. After the system is in operation, the two control values ​​of the motors are refreshed and iterated according to the guide mirror frame rate, driving the turntable to move and gradually reduce pixel deviation until the target coincides with the coordinates of the center of the field of view, achieving a stable tracking effect.

[0161] By employing adaptive PI parameter conditions, stable tracking of both low-dynamic targets (stars / satellites) and high-dynamic targets (aircraft / rockets / reentry capsules) can be achieved. Tracking accuracy is as follows: Figure 6 , Figure 7 and Figure 8 As shown.

[0162] Pointing accuracy is used to measure the pointing performance of a system. Pointing accuracy refers to the deviation between the expected and actual pointing directions of a vector fixed on the line of sight after rotation. It is essentially a spatial angular error that directly affects the positioning accuracy of the telescope system.

[0163] Data Analysis: The direction of the telescope's optical axis can be considered as a Gaussian distribution, which is also a normal distribution. The 3σ principle of the normal distribution is: the probability that the value is distributed in (μ-3σ, μ+3σ) is 0.9973, that is, 3sigma(3σ) can encompass 99.7% of the data, where σ represents the standard deviation and μ represents the mean.

[0164] Using 99.7% of the data, we performed a pointing accuracy analysis, which is the difference between the actual pointing and the theoretical pointing. The unit of the difference is arcseconds, also known as arcseconds. The term "arcsecond" is only used to describe angles; 1 degree = 60 arcminutes = 3600 arcseconds.

[0165] A star-pointing experiment was conducted using the device of the first embodiment or the system of the second embodiment, with the azimuth axis as the first direction and the elevation axis as the second direction. This device or system can achieve precise star-pointing. The experiment collected 5 minutes of stable star tracking data, and the pointing accuracy was analyzed. 3000 frames of time-series images were selected for analysis, and the results are as follows: Figure 6As shown, the upper graph represents the azimuth axis, and the lower graph represents the pitch axis. The vertical axis represents the difference between the actual pointing and the theoretical pointing, i.e., the vector angle, in ", and the horizontal axis represents the frame timing, in frames. It can be seen that only a few pointing position errors are >30” throughout the process, while the rest are maintained at around -30”. The results show that the system pointing accuracy is better than 30” (3σ).

[0166] Field aircraft tracking tests were conducted to analyze tracking accuracy. Using only PI control, stable tracking was achieved after system parameter tuning. The tracking accuracy was better than 50%. The results are as follows: Figure 7 As shown, the upper graph represents the azimuth axis, and the lower graph represents the pitch axis. The vertical axis represents the difference between the actual pointing and the theoretical pointing, i.e., the vector angle, in degrees. The horizontal axis represents the frame time sequence, in frames. The azimuth axis is the first direction, and the pitch axis is the second direction. Analysis shows that the system's tracking stability for low-speed moving targets (<10° / s) is better than 40" (3σ).

[0167] A laser pointer was fixed to a motor, and the motor's angular velocity was set to 20° / s, and its angular acceleration to 30° / s², causing it to reciprocate. After introducing differential parameters in PID control and tuning the system's PID, stable tracking was achieved. Analysis showed that the system's tracking stability for high-speed moving targets (>10° / s) was better than 110"(3σ), as shown in the results. Figure 8 The upper graph represents the azimuth axis, and the lower graph represents the pitch axis. The vertical axis represents the difference between the actual pointing and the theoretical pointing, i.e., the vector angle, in inches. The horizontal axis represents the frame timing, in frames. The azimuth axis is the first direction, and the pitch axis is the second direction.

[0168] Therefore, it can be seen that when the space target enters the field of view, the guide mirror 11 and the tracking processing module 15 are called to obtain the pixel deviation (miss distance) of the target from the center of the field of view. The deviation value is converted into the motion direction and speed of the first direction turntable 12 and the second direction turntable 13, which drive the turntable to move and gradually reduce the pixel deviation until the target coincides with the coordinates of the center of the field of view, thus achieving a stable tracking effect.

[0169] The above method was applied to tracking and imaging of the International Space Station, using a space target imaging system based on the second implementation method. Figure 9 The space station as seen by an astronomical telescope. Figure 10 The video is cropped, aligned, sharpened, and overlaid to achieve the final effect.

[0170] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A closed-loop tracking method for a space target, wherein a guide mirror is fixed on a first-direction turntable or a second-direction turntable, the first-direction turntable and the second-direction turntable are fixedly connected, and both the first-direction turntable and the second-direction turntable include a motor, characterized in that, Includes the following steps: Place the space target within the field of view of the guide mirror; The method for placing a space target within the field of view of a guide mirror includes: placing the space target within the field of view of the guide mirror using a data-driven tracking method; the data-driven tracking method includes: acquiring the ephemeris file of the space target, determining the position of the space target based on the ephemeris file, and controlling a motor to point the guide mirror at the space target based on the position of the space target; The motor is adjusted using optical tracking to keep the space target continuously within the field of view of the guide mirror; The method of adjusting the motor using optical tracking to keep the space target continuously within the field of view of the guide mirror includes: Obtain the position of the space target in the guide mirror's field of view; use a YOLO neural network to identify the position of the space target in the guide mirror's field of view. If the space target cannot be identified, temporarily switch to digital tracking mode. Once the space target can be identified, immediately switch to optical tracking mode. Calculate the pixel error value in the first direction or the pixel error value in the second direction at predetermined intervals; If the pixel error value in the first direction or the pixel error value in the second direction is greater than or equal to a specified threshold, the pixel error value in the first direction or the pixel error value in the second direction is converted into the motion direction and speed magnitude by means of a ratio to adjust the motor. If the pixel error value in the first direction and the pixel error value in the second direction are both less than a specified threshold, then the pixel error value in the first direction or the pixel error value in the second direction is converted into the direction of motion and speed of the motor through proportional and integral methods.

2. The space target closed-loop tracking method according to claim 1, characterized in that, Methods for calculating pixel error values ​​in the first direction and pixel error values ​​in the second direction include: First, calculate the field of view of the guide mirror. Then, calculate the field of view of each pixel based on the field of view of the guide mirror. Finally, calculate the pixel error value in the first direction and the pixel error value in the second direction based on the field of view of each pixel.

3. The space target closed-loop tracking method according to claim 2, characterized in that, The field of view of the guide mirror is calculated using the following formula: θ w2 =2arctan(w2 / 2f2); θ h2 =2arctan(h2 / 2f2); Where, θ w2 θ represents the width of the guide scope's field of view. h2 w2 represents the height field of view of the guide mirror, w2 represents the CCD width of the guide mirror, h2 represents the CCD height of the guide mirror, and f2 represents the focal length of the guide mirror.

4. The space target closed-loop tracking method according to claim 3, characterized in that, The field of view corresponding to each pixel is calculated based on the field of view of the guide mirror using the following formula: i w′ =θ w2 / w2; i h′ =θ h2 / h2; Where, θ w′ θ represents the field of view in pixels. h′ θ represents the field of view of the height pixels. w2 θ represents the width of the guide scope's field of view. h2 w2 represents the height field of view of the guide mirror, w2 represents the CCD width of the guide mirror, and h2 represents the CCD height of the guide mirror.

5. The space target closed-loop tracking method according to claim 4, characterized in that, The pixel error values ​​in the first and second directions are calculated based on the field of view corresponding to each pixel using the following formula: Err Az =(w2 / 2-centroidX)×0 w′ ; Err El =-(h2 / 2-centroidY)×0 h′ ; Among them, Err Az Err represents the pixel error value in the first direction. El The pixel error value represents the second direction. centroidX represents the width coordinate of the space target in the guide scope's field of view, centroidY represents the height coordinate of the space target in the guide scope's field of view, and θ represents the height coordinate of the space target in the guide scope's field of view. w′ θ represents the field of view in pixels. h′ w2 represents the height pixel field of view, w2 represents the CCD width of the guide mirror, and h2 represents the CCD height of the guide mirror.

6. A closed-loop tracking device for a space target, characterized in that, The device can perform the space target closed-loop tracking method as described in any one of claims 1-5.

7. The space target closed-loop tracking device according to claim 6, characterized in that, include: The first-direction turntable includes a motor; The second-direction turntable is fixedly connected to the first-direction turntable and includes a motor; A guide scope, fixed on a first-direction turntable or a second-direction turntable, is used to photograph space targets; The tracking and processing module is communicatively connected to the guide mirror, the motor of the first direction turntable, and the motor of the second direction turntable. It is used to acquire data captured by the guide mirror, process the data that the motor needs to rotate, and send the data that the motor needs to rotate to the motor.

8. A space target tracking and imaging system, characterized in that, include: The space target closed-loop tracking device as described in claim 6 or 7; Imaging devices; The imaging device is fixed on the first or second direction turntable of the space target closed-loop tracking device.

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