A high-orbit intra-cluster fully autonomous target recognition and relative navigation method

Abstract

The application discloses a high-orbit cluster-in full-autonomous target identification and relative navigation method, adopts only angle measurement relative navigation technology, and performs initial identification and coarse navigation on multiple space point targets one by one to obtain a rough relative position between observation stars and target stars; the rough relative position obtained through coarse navigation and a radio ranging value are subjected to distance matching, and a view meeting a distance threshold value is regarded as completing space domain target registration; the matched radio ranging value and an angle value output by an optical camera are input into a precise navigation system to obtain a precise relative navigation output value; and the navigation output value is subjected to image domain review to complete review of target identification. In the case that GNSS is unavailable in high orbit, only the optical camera and interstellar communication can complete identification and navigation of multiple point targets in the cluster, and the identification result has good reliability.

Description

Technical Field

[0001] This invention relates to the field of spacecraft photoelectric detection and relative navigation technology, and in particular to a fully autonomous target identification and relative navigation method within a high-orbit cluster. Background Technology

[0002] As space missions become increasingly complex, the trend towards miniaturization and swarming of spacecraft is becoming more and more apparent, and swarm target identification and navigation have gradually become a research hotspot both domestically and internationally. In particular, currently, most spacecraft within a swarm are micro- and nano-satellites, and their size, power consumption, and weight limit the measurement payloads they can carry, typically only equipped with simple optical cameras and single-unit inter-satellite radio communication devices.

[0003] Current target identification research primarily focuses on identifying individual point targets, while relative navigation techniques for swarms typically rely on GNSS systems. When multiple point targets are detected, traditional methods distinguish them based on the positioning results provided by GNSS, differentiating multiple point targets on the optical camera's image plane according to their position information. However, this method is limited by the coverage range of GNSS satellites and is therefore only applicable to low-Earth orbit swarms. When swarms are in high Earth orbit without GNSS support, and if the targets are not unique, and the measurement unit only has an optical camera and inter-satellite communication, how to achieve point target identification and navigation for swarms has become a new research hotspot.

[0004] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art. Summary of the Invention

[0005] The purpose of this invention is to provide a fully autonomous target identification and relative navigation method within a high-orbit cluster. In the absence of GNSS available in high orbit, the method can identify and navigate multiple point targets within the cluster using only optical cameras and inter-satellite communication, while ensuring that the identification results have good reliability.

[0006] To achieve the above objectives, this invention provides a fully autonomous target identification and relative navigation method within a high-orbit constellation. It employs angle-only relative navigation technology to perform initial identification and coarse navigation on multiple spatial point targets one by one, obtaining the approximate relative positions between the observed and target stars. The approximate relative positions obtained from coarse navigation are then matched with radio ranging values; targets meeting a distance threshold are considered to have completed spatial domain target registration. The matched radio ranging values ​​and the angle values ​​output by the optical camera are input into a precise navigation system to obtain accurate relative navigation output values. Finally, the navigation output values ​​are verified in the image domain to complete the target identification verification.

[0007] The initial identification method includes: setting a convergence threshold, using angle-only relative navigation technology to filter out targets that converge within the convergence threshold from the cooperative point group targets acquired by the optical camera, and completing the initial identification of the targets.

[0008] The coarse navigation method includes: performing angle-only relative navigation on the initially identified targets to obtain their approximate relative positions.

[0009] The point targets acquired by the optical camera carried by observation star O are micro-nano A, micro-nano B, and micro-nano C stars within the cluster;

[0010] Based on the relative motion relationships f(A,O), f(B,O), and f(C,O) between the observed star O and micro-nano stars A, B, and C, respectively, using the two-body motion, the relative navigation equations between the two stars using only angular measurements are established and denoted as F. angles-only (A,O), F angles-only (B,O), F angles-only (C,O), and the completely observable relative navigation equations are denoted as F(A,O), F(B,O), and F(C,O), respectively;

[0011] Using a polling method, the image points of three point targets A, B, and C in the optical camera of the observed star O are obtained. elevation and azimuth (γ) a ,β a ), (γ b ,β b ), (γ c ,β c ), respectively calculate the relative navigation equation F using only the measured angle. angles-only The input values ​​of (A,O);

[0012] Set convergence threshold Thd t = (T,h), if the navigation output error converges within h within time T, the system is considered to have converged; otherwise, the navigation output is considered to be diverging only relative to the angle measurement.

[0013] To meet the needs of extreme cases, assuming that microsatellites A and B are relatively close to each other and both meet the convergence threshold criteria when passing through the angle-only navigation system, the approximate relative positions of microsatellites A and B with the observed star O can be obtained.

[0014] The spatial domain target registration method includes: comparing the approximate relative position obtained by coarse navigation with the radio ranging value; when the distance deviation between the two is less than the distance threshold, establishing a correspondence between the point target in the optical camera and the corresponding radio ranging value, and completing the target registration in the spatial domain.

[0015] Approximate locations of the two satellites, MicroNano A and MicroNano B. The distance scalars between the two approximate positions and the observation satellite O are transmitted via inter-satellite communication, and the observation satellite calculates these distances. and Calculate the distance scalar and By comparing the precise distance values ​​measured through inter-satellite communication, two distance deviation values ​​are obtained. and Based on the fundamental understanding that the approximate location of a correct point target is closer to its actual location, the two distance deviation values ​​Δ A ,Δ B With the set distance threshold Thd L =l comparison, less than distance threshold Thd L = deviation value Δ of l A The corresponding point target is determined to meet F. angles-only The result of target identification (A,O) is the micro-nano A-star. Another point target that exceeds the distance threshold is judged as not conforming, that is, it is not the micro-nano A-star.

[0016] Employing a fully observable relative navigation equation F(A,O) and the azimuth angle (γ) output by the optical camera. a ,β a ) and radio ranging value L A To accurately navigate the microsatellite A, its precise relative position (X) was obtained. A ,Y A Z A ) and relative velocity

[0017] The image domain verification method includes: position verification and velocity verification;

[0018] The relative position and relative velocity in the navigation output value are projected onto the image plane to obtain the theoretical position and velocity of each point target on the image plane. The actual position of each image point on the image plane is extracted, and the velocity direction of the image point is extracted by projecting each point target into multiple consecutive frames. The theoretical position and theoretical velocity are matched with the actual position and velocity direction of the image point for a second time to determine whether the verification threshold is met.

[0019] Based on the precise relative position of micro-nano A star (X) A ,Y A Z A ) and relative velocity Calculate the theoretical coordinates of image point a corresponding to the micro-nano A-star on the image plane. And theoretical point velocity Using temporal multi-frame projection technology, 10 frames of images are continuously acquired and projected onto an optical camera. The true velocity of image point a on the image plane is then fitted based on the trajectory of image point a. Theoretical coordinates calculated based on navigation And theoretical point velocity Compared with the true value and Is the difference between them less than the review threshold? To determine the accuracy of the target identification result.

[0020] The present invention has the following beneficial effects:

[0021] 1. It can identify and distinguish multiple target objects without feature points in a cluster.

[0022] 2. It has full autonomy and is free from dependence on GNSS systems.

[0023] 3. The measurement methods only require basic measurement equipment carried by the spacecraft, namely optical cameras and inter-satellite communication, without the need for additional auxiliary measurement methods, making it suitable for micro and nano satellite platforms.

[0024] 4. It can provide important technical support for the relative navigation of swarm spacecraft in subsequent high-orbit missions. Attached Figure Description

[0025] Figure 1 This is a flowchart of a fully autonomous target identification and relative navigation method within a high-orbit cluster according to the present invention.

[0026] Figure 2 This is a schematic diagram showing the on-orbit positions of the cluster of spacecraft.

[0027] Figure 3 This is a schematic diagram of the satellite imagery observed by the cluster spacecraft. Detailed Implementation

[0028] The following is based on Figures 1-3 The preferred embodiments of the present invention will be described in detail below.

[0029] like Figure 1 As shown, this invention provides a fully autonomous target identification and relative navigation method within a high-orbit cluster. It can reliably distinguish and navigate multiple distant point targets within a micro / nano cluster using only optical cameras and inter-satellite radio ranging values. Addressing the scenario where no GNSS is available for high-orbit clusters, this invention employs a two-stage navigation process to complete target identification and relative navigation. Target identification refers to using relative navigation information to assist the optical camera in screening, identifying, and verifying targets within the cooperative cluster. The two relative navigation processes refer to angular-only relative navigation and fully observable, precise relative navigation.

[0030] The fully autonomous target identification and relative navigation method within the high-orbit cluster specifically includes the following steps:

[0031] Step S1: Initial identification of targets in the spatial domain;

[0032] Using angle-only relative navigation technology, multiple spatial point targets are screened and coarsely navigated one by one to obtain approximate relative positions;

[0033] The initial target identification method in the spatial domain includes: setting a convergence threshold, combining the information returned by the target (including image, number, distance, etc.), and for cooperative point group targets acquired by the optical camera, employing angle-only relative navigation technology, and determining whether the target meets the threshold condition Thd. t = (T,h) converges, and targets that meet the conditions are selected, thus completing the initial identification of targets.

[0034] The coarse navigation includes: performing angle-only relative navigation on the selected target and obtaining its approximate relative position;

[0035] Step S2: Spatial domain target registration;

[0036] The spatial domain target registration method includes: by setting a judgment threshold, comparing the approximate relative position obtained by coarse navigation with the radio ranging value; when the difference is less than the distance threshold, establishing a correspondence between the point target in the optical camera and the corresponding radio ranging value, and completing the target registration in the spatial domain.

[0037] Step S3: Precise navigation;

[0038] Precise relative navigation refers to the use of a fully observable relative navigation model. The matched radio ranging values ​​and the angle values ​​output by the optical camera are used as navigation observation values ​​and input into the precise navigation system for a second navigation calculation. Since the system is fully observable, precise relative navigation output values ​​can be obtained, including precise relative position and relative velocity, thus achieving fully autonomous relative navigation.

[0039] Step S4: Image domain verification;

[0040] Using the results of the fine navigation output, position and velocity verification are performed in the image plane to complete the target identification verification and ensure reliability;

[0041] Image domain verification includes position verification and velocity verification. That is, the relative position and relative velocity obtained in step S3 are projected onto the image plane to obtain the theoretical position and velocity of each point target on the image plane. At the same time, the actual position of each image point on the image plane is extracted, and the velocity direction of the image point is extracted by projecting each point target into multiple consecutive frames. The theoretical position and velocity are matched with the actual position and velocity direction of the image point for the second time to determine whether the verification threshold is met.

[0042] The invention will be further illustrated by describing a preferred embodiment in detail. An example is given of how observed star O identifies the micro / nano star A among three point targets A, B, and C, and performs verification and navigation.

[0043] Step 1: Initial identification of spatial targets, which involves using angle-only relative navigation technology to screen and coarsely navigate multiple spatial point targets one by one to obtain approximate relative positions.

[0044] Taking one observation star and three target stars as an example, the cluster environment is as follows: Figure 2 As shown, the optical camera carried by the observation star O acquired multiple point targets, namely micro-nano A, micro-nano B, and micro-nano C within the cluster.

[0045] Based on the ease of obtaining the relative motion relationships f(A,O), f(B,O), and f(C,O) between the observed star O and micro / nano stars A, B, and C, respectively, we can establish the relative navigation equations between the two stars using only angular measurements, denoted as F. angles-only (A,O), F angles-only (B,O), F angles-only (C,O), and the completely observable relative navigation equations are denoted as F(A,O), F(B,O), and F(C,O), respectively.

[0046] To enable the observed star O to identify and verify the micro-nano A-star among the three point targets A, B, and C, a polling method is used in step 1. That is, the image points of the three point targets A, B, and C in the optical camera of the observed star O are compared. elevation and azimuth (γ) a ,β a ), (γ b ,β b ), (γ c ,β c ), respectively calculate the relative navigation equation F using only the measured angle. angles-only The input values ​​of (A,O).

[0047] Based on the convergence characteristics of the filtering process, errors in the observed parameters can cause the program to diverge; therefore, a convergence threshold Thd is set. t = (T, h), if the navigation output error converges within h within time T, the system is considered convergent; otherwise, the angular-only relative navigation output is considered divergent. Theoretically, when both the micro-nano B and micro-nano C satellites pass through this step, the angular-only relative navigation system will diverge, thus completing target selection.

[0048] To meet the needs of extreme cases, assuming that microsatellites A and B are relatively close to each other and both meet the convergence threshold criteria when passing through the angle-only navigation system, the approximate relative positions of microsatellites A and B with the observed star O can be obtained.

[0049] It should be noted that although the micro-nano C satellite was directly filtered out in this round of polling because it caused the angular-only relative navigation system to diverge, making it impossible to obtain a rough relative position, this does not mean that the relative position of the micro-nano C satellite is forever unobtainable. When the next round uses F... angles-only When polling cluster point targets (C,O), micro-nano C-stars will be accurately selected and their approximate relative positions will be obtained.

[0050] Step 2, Spatial Domain Target Registration: This involves setting a threshold and matching the approximate relative position obtained from coarse navigation with the ranging value from the radio to complete target registration.

[0051] Based on the extreme case assumptions in the previous step, the approximate locations of the two satellites, MicroNano A and MicroNano B, can be obtained. like Figure 3 As shown, in order to identify the angle-only relative navigation equation F angles-only To determine whether the target point corresponding to (A,O) is A or B, firstly, the two approximate locations are transmitted to the observing satellite O via inter-satellite communication. Then, the distance scalars between the two approximate locations and the observing satellite are calculated on the observing satellite. and Then, the calculated distance scalar and By comparing the precise distance values ​​measured through inter-satellite communication, two distance deviation values ​​are obtained. and Finally, based on the fundamental understanding that the approximate location of a correct point target is closer to its actual location, the two distance deviation values ​​Δ are... A ,Δ B With the set distance threshold Thd L =l comparison, deviation value Δ less than the threshold A The corresponding point target is determined to meet F. angles-only The result of target identification (A,O) is the micro-nano A-star. Another point target that exceeds the distance threshold is judged as not conforming, that is, it is not the micro-nano A-star.

[0052] Step 3, Precise Navigation: This involves inputting the matched radio ranging values ​​and the angle values ​​output by the optical camera into the precise navigation system to obtain precise relative navigation output values, including precise relative position and relative speed, thereby achieving fully autonomous relative navigation.

[0053] After steps 1 and 2, the image plane of the optical camera has been... Points and their corresponding elevation and azimuth angles (γa, βa) and inter-satellite communication radio ranging values ​​L AThe correspondence has been completed. The above measurements are completely observable for the relative navigation system, enabling accurate relative navigation output results. Therefore, in step 3, the completely observable relative navigation equation F(A,O), the (γa,βa) output by the optical camera, and the radio ranging value L are used. A To accurately navigate the microsatellite A, its precise relative position (X) was obtained. A ,Y A Z A ) and relative velocity

[0054] Step 4: Image domain verification. This involves using the results of the fine navigation output to perform position and velocity verification in the image plane, thus completing the verification of target identification and ensuring reliability.

[0055] First, based on the precise relative position and velocity of the micro-nano A-star obtained in step 3, the theoretical coordinates of the image point 'a' corresponding to the micro-nano A-star on the image plane are calculated. And theoretical point velocity Then, using temporal multi-frame projection technology, 10 frames of images are continuously acquired and projected onto the optical camera. Based on the trajectory of image point a, the true image point velocity of image point a on the image plane is fitted. Finally, based on the theoretical coordinates calculated by navigation... And theoretical point velocity Compared with the true value and Is the difference between them less than the review threshold? To determine the accuracy of the target identification result.

[0056] This invention employs angle-only relative navigation technology to achieve initial spatial domain identification of multiple point targets. Then, coarse navigation is used to provide approximate relative positions between the observed and target satellites. Next, the approximate relative positions obtained from the coarse navigation are matched with radio ranging values; targets meeting a threshold are considered successfully registered in the spatial domain. The matched radio ranging values ​​and the angle values ​​output by the optical camera are then input into a precise navigation system to obtain accurate relative navigation output values. Finally, the results of the precise navigation are used for image domain verification to complete the target identification verification and ensure reliability. This invention, employing a process of two navigation steps, one registration step, and one verification step, solves the problem of fully autonomous target identification and relative navigation within high-orbit swarms. Specifically, it addresses the challenge of how to match point targets extracted by the optical camera with radio ranging values ​​when swarm spacecraft are in high orbit without GNSS and the observed satellites can only obtain measurements through optical cameras and inter-satellite radio communication equipment, thus completing the identification and precise relative navigation of multiple swarm point targets within the optical camera's field of view.

[0057] The method provided by this invention solves the problem of identifying and navigating multiple point targets one by one in high-orbit micro-nano swarm spacecraft. It enables the observation spacecraft to identify each point target among numerous targets acquired by optical cameras, accurately match optical and radio signals, and obtain the relative navigation value for each target. The advantage of this technology lies in its completely autonomous relative navigation within the swarm; that is, it can obtain relative navigation values ​​without relying on a GNSS system. It possesses the ability to identify and navigate multiple point targets within the swarm using only optical cameras and inter-satellite communication, even in high-orbit environments without GNSS availability, while ensuring accurate identification. The effective application and implementation of this technology will fully realize the identification of swarm members and relative position estimation in high-orbit environments without GNSS availability, enabling swarm spacecraft to possess fully autonomous relative navigation capabilities within the swarm in various environments. This provides crucial technical support for subsequent scientific exploration missions, such as deep space exploration based on swarm micro-nano satellites.

[0058] This invention addresses the problem of fully autonomous identification and navigation of multiple indistinguishable point targets within a swarm, where the large distances between satellites cause the loss of area target features. It enables high-orbit swarms to promptly detect changes in the positions of multiple point targets even without GNSS availability, particularly avoiding misidentification caused by the exchange of positions between two point targets. This invention does not require additional measurement equipment from the observation spacecraft, can be used for recapture after target loss due to changes in lighting conditions or rapid maneuvers, and has the capability for widespread deployment on various micro / nano spacecraft platforms.

[0059] It should be noted that, in the embodiments of the present invention, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing the embodiments. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0060] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0061] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A fully autonomous target identification and relative navigation method within a high-orbit cluster, characterized in that, Include: Angle-only relative navigation technology is used to perform initial identification and coarse navigation on multiple spatial point targets one by one, obtaining the approximate relative positions between the observed star and the target star. The initial identification method includes: setting a convergence threshold, and using angle-only relative navigation technology to select targets that converge within the convergence threshold from the cooperative point group targets acquired by the optical camera, thus completing the initial identification of the targets. The coarse navigation method includes: performing angle-only relative navigation on the targets selected by the initial identification to obtain their approximate relative positions. The point targets acquired by the optical camera carried by observation star O are micro-nano A, micro-nano B, and micro-nano C stars within the cluster; The relative motion relationships between observed star O and micro / nano stars A, B, and C were obtained based on two-body motion. , , The relative navigation equations between the two satellites, based solely on angular measurements, are established and denoted as follows: , , And the completely observable relative navigation equations are denoted as follows: , , ; Using a polling method, the image points of three point targets A, B, and C in the optical camera of the observed star O are obtained. elevation and azimuth , , Perform the relative navigation equations using only the measured angles. Input quantity; Set convergence threshold If the navigation output error converges within h within time T, the system is considered to have converged; otherwise, the navigation output is considered to be divergent only relative to the angle measurement. To meet the needs of extreme cases, assuming that microsatellites A and B are relatively close to each other and both meet the convergence threshold criteria when passing through the angle-only navigation system, the approximate relative positions of microsatellites A and B with the observed star O can be obtained. , ; The approximate relative position obtained from coarse navigation is matched with the ranging value from the radio. If the distance threshold is met, the spatial domain target registration is considered complete. The matched radio ranging value and the angle value output by the optical camera are input into the precision navigation system to obtain the accurate relative navigation output value; The navigation output values ​​are verified in the image domain to complete the verification of target identification.

2. The fully autonomous target identification and relative navigation method within a high-orbit cluster as described in claim 1, characterized in that, The spatial domain target registration method includes: comparing the approximate relative position obtained by coarse navigation with the radio ranging value; when the distance deviation between the two is less than the distance threshold, establishing a correspondence between the point target in the optical camera and the corresponding radio ranging value, and completing the target registration in the spatial domain.

3. The fully autonomous target identification and relative navigation method within a high-orbit cluster as described in claim 2, characterized in that, Approximate locations of the two satellites, MicroNano A and MicroNano B. , The distance scalars between the two approximate positions and the observation satellite O are transmitted via inter-satellite communication, and the observation satellite calculates these distances. and ; calculate the distance scalar and By comparing the precise distance values ​​measured through inter-satellite communication, two distance deviation values ​​were obtained. and ; Based on the fundamental understanding that the approximate location of a correct point target is closer to its actual location, the two distance deviation values ​​are... and the set distance threshold Comparison, less than the distance threshold deviation value The corresponding point target is determined to be in compliance with The result of target identification is micro-nano A-star. Another point target that exceeds the distance threshold is judged as not conforming, that is, it is not micro-nano A-star.

4. The fully autonomous target identification and relative navigation method within a high-orbit cluster as described in claim 3, characterized in that, Employing fully observable relative navigation equations azimuth angle output by the optical camera and radio ranging values Precise navigation of the microsatellite A was performed to obtain its precise relative position. and relative velocity .

5. The fully autonomous target identification and relative navigation method within a high-orbit cluster as described in claim 4, characterized in that, Methods for image domain verification include: position verification and velocity verification; The relative position and relative velocity in the navigation output value are projected onto the image plane to obtain the theoretical position and velocity of each point target on the image plane. The actual position of each image point on the image plane is extracted, and the velocity direction of the image point is extracted by projecting each point target into multiple consecutive frames. The theoretical position and theoretical velocity are matched with the actual position and velocity direction of the image point for a second time to determine whether the verification threshold is met.

6. The fully autonomous target identification and relative navigation method within a high-orbit cluster as described in claim 5, characterized in that, Based on the precise relative position of micro-nano A-star and relative velocity Calculate the theoretical coordinates of image point a corresponding to the micro-nano A-star on the image plane. And theoretical point velocity Using temporal multi-frame projection technology, 10 frames of images are continuously acquired and projected onto an optical camera. The true velocity of image point a on the image plane is then fitted based on the trajectory of image point a. Theoretical coordinates calculated based on navigation And theoretical point velocity Compared with the true value and Is the difference between them less than the review threshold? This is used to determine the accuracy of the target identification result.

Images