Star sensor simulation teaching system

Abstract

The invention discloses a star sensor simulation teaching system, which comprises a star map simulation device, the star map simulation device generates a simulation star map by a star map simulation computer, projects a star point in a view field pointed by a star sensor visual axis to a star sky simulation device, and simulates a real star sky environment; the star sensor simulation equipment simulates a star sensor through an industrial camera, shoots a star map on the star sky simulation equipment by adjusting the distance of the bracket, and simulates the shooting process of the star sensor; the device has the beneficial effects that the working principle and the working process of the star sensor are visually displayed by simulating the real star sky environment and the working process of the star sensor, so that students can understand and master the working principle and the working process conveniently; practical operation links such as star map acquisition, processing, recognition and attitude calculation are provided, and the operational ability and practical ability of students are enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of star sensor simulation teaching, and in particular relates to a star sensor simulation teaching system. Background Art

[0002] A star sensor is a high-precision space attitude measurement device that uses stars as a reference system and the starry sky as a measurement object. By detecting stars at different positions on the celestial sphere and performing attitude calculations, it provides accurate spatial orientation and high-precision attitude references for satellites, space stations and other spacecraft, and has important application value.

[0003] However, the working principle of star sensors is complex and requires high operating skills. Traditional theoretical teaching makes it difficult for students to fully understand and master it. Summary of the invention

[0004] The purpose of the present invention is to provide a star sensor simulation teaching system, which can deepen students' understanding of the working principle of star sensors and the operation process of star sensors by simulating the operation tasks of star sensors in real situations, so as to achieve comprehensive training of students' theoretical knowledge and practical skills.

[0005] To achieve the above object, the present invention provides the following technical solution: a star sensor simulation teaching system, comprising

[0006] A star map simulation device, wherein the star map simulation device generates a simulated star map by a star map simulation computer, projects the star points within the field of view pointed by the star-sensitive visual axis onto the starry sky simulation device, and simulates a real starry sky environment;

[0007] A star sensor simulation device, wherein the star sensor simulation device simulates a star sensor with an industrial camera, and shoots a star map on the starry sky simulation device by adjusting the distance of the bracket to simulate the shooting process of the star sensor;

[0008] The star map acquisition and processing demonstration device performs filtering, correction, star point extraction, star map recognition, attitude quaternion solution output and star map tracking processing on the collected star map, and gradually shows the operation steps of the star sensor through teaching demonstration, so as to facilitate students to deeply understand and master its working principle.

[0009] As a preferred technical solution of the present invention, it also includes star sensor calibration, which is used to obtain internal parameters of the imaging system and then complete high-precision attitude measurement of the aircraft.

[0010] As a preferred technical solution of the present invention, the calibration process is as follows:

[0011] A high-precision calibration object with known parameters is obtained, and the internal parameters of the star sensor are obtained in an optimized manner through the spatial coordinates of the feature points on the calibration object and their projection coordinates on the two-dimensional image, combined with the imaging model.

[0012] As a preferred technical solution of the present invention, filtering processing is performed on the collected star map, including linear filtering, median filtering, and morphological filtering.

[0013] As a preferred technical solution of the present invention, a segmentation method based on image grayscale is used to complete the extraction of star regions in the image; after the star region extraction is completed, the connected regions are marked according to the segmentation results, and the features of each connected region are calculated to obtain the center of mass position of each star in the star map.

[0014] As a preferred technical solution of the present invention, a centroid extraction algorithm is used to obtain the centroid position of each star in the star map. The algorithm includes a centroid method, a square weighted centroid method, and a surface fitting method.

[0015] As a preferred technical solution of the present invention, the method for star map recognition includes:

[0016] Subgraph isomorphism algorithm: The star map recognition problem is regarded as a special case of the subgraph isomorphism problem. The algorithm uses the star points in the field of view as the vertices of the graph and the distances between the star points as the edges to construct an undirected graph and search for subgraphs in the navigation database that are consistent with the observed undirected graph.

[0017] Pattern recognition algorithm: Construct a unique pattern or mark for each navigation star, which is determined by the distribution of its neighborhood star points; the navigation star corresponding to the pattern closest to the observed pattern in the navigation star database is considered to be a matching star point.

[0018] As a preferred technical solution of the present invention, it also includes attitude calculation, and the corresponding method is as follows: according to the star map recognition result, the coordinates of the stars corresponding to the current star map in the geocentric inertial coordinate system are obtained, and the position coordinates of the star points in the two-dimensional image are combined with the internal parameters of the star sensor itself. The star sensor's own attitude is acquired by model optimization, and high-precision attitude measurement of the aircraft is achieved.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] By simulating the real starry sky environment and the operation process of the star sensor, the working principle and operation process of the star sensor are intuitively demonstrated to facilitate students' understanding and mastery;

[0021] Provide practical operation links such as star map collection, processing, recognition and attitude calculation to enhance students' hands-on and practical abilities;

[0022] The operation steps of the star sensor are demonstrated step by step, which is convenient for teachers to conduct teaching demonstrations and explanations, and improve teaching effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the system principle diagram of the present invention;

[0024] Figure 2 It is a schematic diagram of the star tracking process of the present invention;

[0025] Figure 3 is the overall system flow chart of the present invention; DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] See also Figure 1 , which is the first embodiment of the present invention, provides a star sensor simulation teaching system, including

[0029] Star map simulation equipment, the star map simulation equipment generates a simulated star map by a star map simulation computer, and projects the star point within the field of view pointed by the star-sensitive visual axis onto the star sky simulation equipment to simulate the real starry sky environment;

[0030] Star sensor simulation equipment: the star sensor simulation equipment simulates the star sensor with an industrial camera, and shoots the star map on the starry sky simulation equipment by adjusting the distance of the bracket to simulate the shooting process of the star sensor;

[0031] The star map acquisition and processing demonstration equipment filters, corrects, extracts star points, identifies star maps, outputs attitude quaternion solutions, and tracks star maps. Through teaching demonstrations, it gradually shows the operating steps of the star sensor, making it easier for students to deeply understand and master its working principles.

[0032] The overall system can simulate and collect star maps, and perform filtering, correction, star point extraction, star map recognition, attitude quaternion solution output and star map tracking on the collected star maps. It can gradually demonstrate the operation process of the star sensor.

[0033] The operation process is as follows, please refer to the attached Figure 3 :

[0034] Camera connection:

[0035] Double-click the camera on the desktop to connect to the software; (Note: If the software interface cannot be displayed after double-clicking, close the dual-screen system, reopen the software, and restore the dual-screen function after reopening);

[0036] The system will automatically identify the camera driver;

[0037] Click the Image Capture button;

[0038] The image is displayed normally and the camera is connected successfully;

[0039] Simulated star map generation:

[0040] Open the star map simulation software, click the "Operation"-"Start" button to simulate the movement of the star map;

[0041] Select a suitable simulated star map and click the "Operation"-"Stop" button to obtain the current simulated star map image;

[0042] Open the Add Background button, add a suitable background to the current simulated star map, and press the F key to enter full screen mode;

[0043] Generate a simulated star map diagram:

[0044] Open the star sensor teaching software, click the "Open Camera" button to collect the current simulated star map image, and click the "Collect Image" button to obtain the current frame image for processing;

[0045] Image preprocessing:

[0046] Click the image preprocessing button in the star sensor teaching software to preprocess the image of the current simulated star map;

[0047] Star map preprocessing results:

[0048] Star point extraction:

[0049] Click the Extract Coordinates button in the star sensor teaching software to preprocess the image of the current simulated star map;

[0050] Star point extraction results;

[0051] Star map recognition:

[0052] Click the star point recognition button in the star sensor teaching software to match the current simulated star map with the data in the star map library to complete the recognition of the current simulated star map;

[0053] Posture calculation:

[0054] Click the attitude calculation button in the star sensor teaching software to calculate the attitude of the star sensor itself using the current simulated star map recognition results.

[0055] In the present embodiment, preferably, the calibration of the star sensor is also included, and the purpose of the star sensor calibration is to obtain the internal parameters of the imaging system, and then complete the high-precision attitude measurement of the aircraft; generally speaking, the calibration process requires a high-precision calibration object with known parameters, and the spatial coordinates of the characteristic points on the calibration object and their projection coordinates on the two-dimensional image are combined with the imaging model to adopt an optimized method to achieve the acquisition of the internal parameters of the star sensor; in the actual star sensor calibration task, it is necessary to consider the distortion factor of the optical system; the optical system distortion generally includes radial distortion and eccentric distortion; if the lens shape of the optical imaging system is imperfect, then the resulting image will have a deviation in the radial position, which is called radial distortion; this distortion is symmetrical about the main optical axis of the lens, and the closer to the edge, the greater the distortion; the shape of the distortion is related to the positive and negative of the distortion coefficient, when the coefficient is positive, the image as a whole stretches out (barrel distortion), when the distortion coefficient is negative, the image as a whole shrinks inward (pincushion distortion).

[0056] In this embodiment, preferably, image preprocessing is also included, and its function is to remove the image noise caused by factors such as dark current of photosensitive devices and starry sky background in the real star map, so as to improve the image quality; generally, linear filtering, median filtering, morphological filtering and other methods are used to preprocess the star map obtained by the star sensor; image mean filtering is a basic linear smoothing filtering method, and the main idea is to remove the high-frequency noise component in the image, so as to improve the quality of the star map; its principle is to replace the gray value of each pixel in the image with the average gray value of the pixels in the n×n size area around the pixel;

[0057] In this teaching system, median filtering is used to remove background noise, thereby improving the accuracy of star point extraction.

[0058] In this embodiment, preferably, star point extraction: the function is to use image segmentation to complete the extraction of stars in the star map according to the difference in brightness between the stars and the background; generally, a segmentation method based on image grayscale is used to complete the extraction of star areas in the image; after the star area extraction is completed, the connected area will be marked according to the segmentation result, and the feature calculation will be performed on each connected area to obtain the center of mass position of each star in the star map; the current mature center of mass extraction algorithms include the center of mass method, the square weighted center of mass method, the surface fitting method, etc.; the accuracy of a suitable center of mass positioning algorithm can reach 1 / 20 pixel; in this teaching system, the classic image segmentation method Otsu method is used to extract the star area, and the method used in the center of mass calculation part is the square weighted center of mass method.

[0059] In this embodiment, preferably, star map recognition is to perform feature description on the distribution of star points in the currently acquired star map, and match the description features with the corresponding feature sets in the star map database, thereby completing the recognition of the acquired star map; current star map recognition methods are mainly divided into two categories, including subgraph isomorphism algorithms and pattern recognition algorithms; the algorithms generally use the distance between star pairs, triangles or polygons to construct a navigation database, which has a simple structure and is easy to implement; in this teaching system, triangles are used as star map features, and the subgraph isomorphism algorithm is used to complete the recognition of the acquired star map.

[0060] In this embodiment, preferably, attitude calculation is also included. According to the star map recognition result, the coordinates of the stars corresponding to the current star map in the geocentric inertial coordinate system can be obtained. By combining the position coordinates of the star points in the two-dimensional image with the internal parameters of the star sensor itself, the attitude of the star sensor itself can be acquired by model optimization, and high-precision attitude measurement of the aircraft can be achieved at the same time.

[0061] Example 2

[0062] See also Figure 1 , 2 3 is the second embodiment of the present invention, which is based on the previous embodiment, except that:

[0063] It also includes attitude tracking: there are two operating modes of the star sensor: initial attitude capture mode and tracking mode; the initial attitude capture mode provides accurate initial recognition information and precise initial attitude for the tracking mode; when tracking recognition fails or the attitude is lost, the tracking mode automatically switches to the initial attitude capture mode and re-performs full-celestial star map recognition; when working in the initial attitude capture mode, since there is no initial attitude, the entire celestial sphere is used as an uncertain sky area for star map recognition, so the search and matching time is relatively long, and the general recognition process takes seconds; the tracking mode uses the results of full-celestial star map recognition and attitude calculation, and the recognition information of the previous few frames of star tracking to track and identify the observed stars in the current field of view. , so the processing time of the tracking process is relatively short; the initial attitude capture is only performed at the start or when the tracking is lost. If the tracking mode is very stable, the star sensor will be in a real-time tracking state after the initial attitude capture, so the tracking mode is the main working mode of the star sensor; the most common star sensor attitude tracking method in actual engineering is the fast star tracking algorithm using inter-frame star point matching; the overall idea is: through star point prediction, a reference star map is generated, and a neighborhood radius is set to determine whether the observed star of the observed star map falls within the neighborhood of the corresponding star in the reference star map to determine whether the tracking is successful; the number of tracked stars in the field of view is increased by the star point mapping method for continuous tracking.

[0064] The overall star sensor tracking task includes the following steps:

[0065] Initial attitude acquisition: After the star sensor starts working, its attitude is unknown. First, it needs to enter the initial attitude capture mode, use triangulation and other methods to complete the star map recognition within the entire celestial sphere, calculate the initial precise attitude, obtain the initial attitude of the star sensor, and then enter the tracking mode;

[0066] Search for navigation stars: According to the attitude of the star sensor, the current visual axis direction of the star sensor can be calculated, and the navigation star information of a certain sky area under this visual axis direction can be obtained. The information of stars is obtained from the navigation star catalog (the star's serial number, brightness, right ascension and declination coordinates, etc.). These stars are the stars that the image sensor of the star sensor can capture in this attitude state;

[0067] Star point mapping: Since the star map collected by the image sensor is based on the image coordinate system, and the navigation star coordinate information stored in the star catalog is based on the celestial coordinate system, the coordinates of the navigation star within this sky area must be transformed from the celestial coordinate system to the image coordinate system (that is, the right ascension and declination information of the navigation star in the star catalog is converted into the position coordinate information on the photosensitive surface of the image sensor); in the tracking process, the value mapping method is adopted, that is, the generation method of the simulated reference star map is determined according to the number of matching star points identified in the predicted star map and the observed star map;

[0068] Star point prediction: During tracking and matching, the position of the star point in the next frame of the star map can be predicted based on the moving trajectory of the star point in the previous frames of the known star map. This can greatly improve the success rate of matching and recognition during tracking and matching.

[0069] Reference star map generation: The reference star map is generated from the known attitude information of the star sensor through the processes of searching for navigation stars, star point mapping and star point prediction. The star information in the star map is known.

[0070] Observation star map: The observation star map is the actual image collected by the star sensor. By matching the star points in the observation star map with those in the reference star map, the attitude calculation of the star sensor in the current frame can be completed, thereby achieving attitude tracking.

[0071] Although the embodiments of the present invention have been shown and described, as detailed above, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A star sensor simulation teaching system, characterized by: include A star map simulation device, wherein the star map simulation device generates a simulated star map by a star map simulation computer, projects the star points within the field of view pointed by the star-sensitive visual axis onto the starry sky simulation device, and simulates a real starry sky environment; A star sensor simulation device, wherein the star sensor simulation device simulates a star sensor with an industrial camera, and shoots a star map on the starry sky simulation device by adjusting the distance of the bracket to simulate the shooting process of the star sensor; The star map acquisition and processing demonstration device performs filtering, correction, star point extraction, star map recognition, attitude quaternion solution output and star map tracking processing on the collected star map, and gradually shows the operation steps of the star sensor through teaching demonstration, so as to facilitate students to deeply understand and master its working principle.

2. A star sensor simulation teaching system according to claim 1, characterized in that: It also includes star sensor calibration, which is used to obtain the internal parameters of the imaging system and then complete the high-precision attitude measurement of the aircraft.

3. A star sensor simulation teaching system according to claim 2, characterized in that: The calibration process is as follows: A high-precision calibration object with known parameters is obtained, and the internal parameters of the star sensor are obtained in an optimized manner through the spatial coordinates of the feature points on the calibration object and their projection coordinates on the two-dimensional image, combined with the imaging model.

4. A star sensor simulation teaching system according to claim 1, characterized in that: The filtering processing of the collected star images includes linear filtering, median filtering and morphological filtering.

5. A star sensor simulation teaching system according to claim 1, characterized in that: The image grayscale-based segmentation method is used to extract the star region in the image. After the star region is extracted, the connected regions are marked according to the segmentation results, and the features of each connected region are calculated to obtain the center of mass position of each star in the star map.

6. A star sensor simulation teaching system according to claim 5, characterized in that: The centroid position of each star in the star map is obtained by using a centroid extraction algorithm, which includes the centroid method, square weighted centroid method, and surface fitting method.

7. A star sensor simulation teaching system according to claim 1, characterized in that: The method for star map recognition comprises: Subgraph isomorphism algorithm: The star map recognition problem is regarded as a special case of the subgraph isomorphism problem. The algorithm uses the star points in the field of view as the vertices of the graph and the distances between the star points as the edges to construct an undirected graph and search for subgraphs in the navigation database that are consistent with the observed undirected graph. Pattern recognition algorithm: Construct a unique pattern or mark for each navigation star, which is determined by the distribution of its neighborhood star points; the navigation star corresponding to the pattern closest to the observed pattern in the navigation star database is considered to be a matching star point.

8. The star sensor simulation teaching system according to claim 1, characterized in that: It also includes attitude calculation, and the corresponding method is as follows: according to the star map recognition results, the coordinates of the stars corresponding to the current star map in the geocentric inertial coordinate system are obtained, and the position coordinates of the star points in the two-dimensional image are combined with the internal parameters of the star sensor itself. The star sensor's own attitude is acquired through model optimization, and high-precision attitude measurement of the aircraft is achieved.

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