An on-orbit evaluation method for single-frame attitude accuracy of star sensors

Abstract

This invention discloses an on-orbit evaluation method for the single-frame attitude accuracy of a star sensor, comprising: S1, calculating the single-frame attitude covariance matrix of the star sensor by combining the synthesized value of the variance of noise from all star vector measurements; S2, evaluating the three-axis attitude error of the star sensor based on the attitude covariance matrix; S3, calculating the single-frame attitude quality factor of the star sensor based on the three-axis attitude error value; and S4, evaluating the attitude error of the star sensor based on the quality factor. This invention achieves on-orbit real-time calculation and evaluation of the single-frame attitude accuracy of a star sensor by calculating the covariance matrix of the star sensor and constructing a "quality factor".

Description

Technical Field

[0001] This invention relates to the field of star sensor star detection, and in particular to an on-orbit evaluation method for single-frame attitude accuracy of a star sensor. Background Technology

[0002] As a key component for spacecraft attitude measurement, the star sensor's attitude accuracy is its most important indicator. A comprehensive theory and methodology for star sensor accuracy evaluation is crucial for the development of high-precision star sensors. Currently, star sensor accuracy evaluation methods include the sliding window method, the optical axis angle method, the star diagonal distance method, and the epoch difference method. These methods are primarily used for ground-based data analysis, characterized by high computational demands, large sample size requirements, and the inability to evaluate star sensor attitude accuracy in real-time on-orbit.

[0003] Therefore, this invention addresses the application scenario of on-orbit evaluation of star sensor accuracy and proposes an on-orbit evaluation method for single-frame attitude accuracy of star sensors based on constructing a "quality factor" from the star sensor covariance matrix. Summary of the Invention

[0004] The purpose of this invention is to provide an on-orbit evaluation method for the single-frame attitude accuracy of a star sensor, which can solve the problems of large computational load, large sample quantity requirements, and inability to evaluate the accuracy of a star sensor in real time on orbit.

[0005] To achieve the above objectives, this invention provides an on-orbit evaluation method for the single-frame attitude accuracy of a star sensor, comprising:

[0006] S1, combine the combined values ​​of the noise variance of all star vector measurements to calculate the single-frame attitude covariance matrix of the star sensor;

[0007] S2, Evaluate the three-axis attitude error of the star sensor based on the attitude covariance matrix;

[0008] S3, Calculate the single-frame attitude quality factor of the star sensor based on the three-axis attitude error value of the star sensor;

[0009] S4, evaluate the attitude error of the star sensor based on the quality factor.

[0010] Optionally, step S1 includes:

[0011] S1.1, Calculate the composite value of the noise variance for all star vector measurements.

[0012] S1.2, the composite value of noise variance is measured using the star vector. Calculate the single-frame attitude covariance matrix P of the star sensor.

[0013] Optionally, the synthesized value of the star vector measurement noise variance The calculation formula is:

[0014]

[0015] In the formula, A is the attitude transition matrix calculated by the star sensor in the current frame, and V i To measure the standard star vector corresponding to the star vector in the star catalog; W i is the star vector to be measured; n is the number of stars involved in the attitude calculation.

[0016] Optionally, the formula for calculating the single-frame attitude covariance matrix P of the star sensor is as follows:

[0017]

[0018] In the formula, a i To measure the star vector weights, W i T This is for measuring the transpose of the star vector.

[0019] Optionally, the calculation formulas for the three-axis attitude error of the star sensor in step S2 are as follows:

[0020]

[0021] In the formula, Cov_X represents the X-axis attitude error of the star sensor, Cov_Y represents the Y-axis attitude error of the star sensor, and Cov_Z represents the Z-axis attitude error of the star sensor; P[1,1], P[2,2], and P[3,3] represent the three diagonal elements of the covariance matrix P in sequence.

[0022] Optionally, step S3 includes:

[0023] S3.1, Calculate the average attitude error ε of the star sensor across three axes;

[0024] S3.2, Calculate the single-frame attitude quality factor QI of the star sensor using the average three-axis attitude error ε of the star sensor.

[0025] Optionally, the formula for calculating the average three-axis attitude error ε of the star sensor is:

[0026]

[0027] In the formula, weight X Weights are assigned to the X-axis attitude error of the star sensor. Y Weights are assigned to the Y-axis attitude error of the star sensor. Z Assign weights to the Z-axis attitude error of the star sensor.

[0028] Optionally, the formula for calculating the single-frame attitude quality factor (QI) of the star sensor is as follows:

[0029]

[0030] In the formula, These are the parameters of the quality factor transfer function.

[0031] Optionally, the evaluation of the star sensor attitude error based on the quality factor includes:

[0032] If the single-frame attitude quality factor (QI) of the star sensor is greater than 0.95, then the attitude of the current frame is considered to meet the accuracy index requirements.

[0033] Optionally, the evaluation of the star sensor attitude error based on the quality factor further includes:

[0034] When the single-frame attitude quality factor (QI) of the star sensor is between 0.8 and 0.95, the attitude accuracy of the current frame is considered to have decreased.

[0035] If the single-frame attitude quality factor (QI) of the star sensor is less than 0.8, the attitude error of the current frame is considered to be large.

[0036] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The present invention provides an on-orbit evaluation method for the single-frame attitude accuracy of a star sensor. By calculating the covariance matrix of the single-frame attitude of the star sensor, the 1σ value of the three-axis attitude error of the star sensor can be calculated in real time on-orbit without ground processing.

[0038] 2. The present invention provides an on-orbit evaluation method for the single-frame attitude accuracy of a star sensor. By introducing a "quality factor", the attitude accuracy of the star sensor can be intuitively characterized, which enhances the flexibility of users in using star sensor data. Attached Figure Description

[0039] Figure 1 This is a flowchart of the on-orbit evaluation method for single-frame attitude accuracy of the star sensor according to the present invention;

[0040] Figure 2 The figure shows the three-axis error curves obtained by calculating the attitude covariance matrix based on the attitude covariance matrix of the star sensor in the field of star observation according to the present invention.

[0041] Figure 3 This is a graph showing the transfer relationship between the star sensor quality factor and the three-axis attitude average error of the present invention.

[0042] Figure 4 This is a scatter plot of the star sensor's quality factor for external star observation in this invention. Detailed Implementation

[0043] The following will be combined with the appendix Figures 1-4The technical content, structural features, objectives and effects of the present invention will be described in detail through preferred embodiments.

[0044] It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions. They are only used to facilitate and clarify the purpose of illustrating the embodiments of the present invention, and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationship, or adjustments to the size should still fall within the scope of the technical content disclosed in the present invention, provided that they do not affect the effects and objectives that the present invention can produce.

[0045] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and 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. Therefore, they should not be construed as limitations on this 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.

[0046] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0047] This invention provides an on-orbit evaluation method for the single-frame attitude accuracy of a star sensor, such as... Figure 1 As shown, the on-orbit evaluation method for the single-frame attitude accuracy of the star sensor includes:

[0048] S1, the composite value combining the noise variance of all star vector measurements. Calculate the single-frame attitude covariance matrix P of the star sensor;

[0049] S2, evaluate the three-axis attitude error of the star sensor based on the attitude covariance matrix P;

[0050] S3, Calculate the single-frame attitude quality factor of the star sensor based on the three-axis attitude error value of the star sensor;

[0051] S4, evaluate the attitude error of the star sensor based on the quality factor.

[0052] Step S1 includes the following steps:

[0053] S1.1, Calculate the composite value of the noise variance for all star vector measurements. The combined value of the noise variance measured by the star vector. The calculation formula is as follows:

[0054]

[0055] In the formula, A is the attitude transition matrix calculated by the star sensor in the current frame, and V i To measure the standard star vector corresponding to the star vector in the star catalog; W i is the star vector to be measured; n is the number of stars involved in the attitude calculation.

[0056] S1.2, the composite value of noise variance is measured using the star vector. Calculate the single-frame attitude covariance matrix P of the star sensor.

[0057] The formula for calculating the single-frame attitude covariance matrix P of the star sensor is as follows:

[0058]

[0059] In the formula, n is the number of stars involved in the attitude calculation, and W i To measure the star vector, a i To measure the star vector weights, Measure the combined noise variance for all star vectors; W i T This is for measuring the transpose of the star vector.

[0060] In an embodiment of the present invention,

[0061] The formulas for calculating the attitude error of the star sensor along the three axes (X, Y, and Z axes) in step S2 are as follows:

[0062]

[0063] In the formula, Con_X represents the X-axis attitude error of the star sensor, Cov_Y represents the Y-axis attitude error of the star sensor, and Con_Z represents the Z-axis attitude error of the star sensor; P[1,1], P[2,2], and P[3,3] represent the three diagonal elements of the covariance matrix P, respectively; wherein, the single-frame attitude covariance matrix P of the star sensor is a third-order matrix, P[1,1] is the element in the first row and first column of the third-order matrix, P[2,2] is the element in the second row and second column of the third-order matrix, and P[3,3] is the element in the third row and third column of the third-order matrix. Furthermore, the error accuracy of the X-axis attitude error of the star sensor, the error accuracy of the Y-axis attitude error of the star sensor, and the error accuracy of the Z-axis attitude error of the star sensor are all 1σ.

[0064] In a specific embodiment of the present invention, the three-axis attitude error curve obtained based on the covariance matrix in the star sensor field observation experiment is shown in the figure below. Figure 2 As shown.

[0065] Step S3 includes the following steps:

[0066] S3.1, Calculate the average three-axis attitude error ε of the star sensor:

[0067]

[0068] In the formula, weight X Weights are assigned to the X-axis attitude error of the star sensor. Y Weights are assigned to the Y-axis attitude error of the star sensor. Z Weights are assigned to the Z-axis attitude error of the star sensor. Furthermore, the accuracy of the average three-axis attitude error ε of the star sensor is 1σ.

[0069] The weight X weight Y weight Z Based on the electronic and optical system parameters of the star sensor; in a specific embodiment of the present invention, weight X Values weight Y Values weight Z Values

[0070] S3.2, Calculate the single-frame attitude quality factor QI of the star sensor using the average three-axis attitude error ε of the star sensor.

[0071] The formula for calculating the single-frame attitude quality factor (QI) of the star sensor is as follows:

[0072]

[0073] In the formula, These are the parameters of the quality factor transfer function.

[0074] The quality factor transfer function parameters The settings are based on the three-axis attitude error index of the star sensor; in a specific embodiment of the present invention, The value is set to 3.05; the relationship curve between the single-frame attitude quality factor QI of the star sensor and the average three-axis attitude error ε of the star sensor is shown in the figure. Figure 3 As shown; the scatter plot of the quality factor in the star sensor's field stargazing experiment is shown below. Figure 4 As shown.

[0075] The star sensor's single-frame attitude quality factor (QI) is a number between 0 and 1. When the quality factor equals 1, it indicates that the average three-axis attitude error is 0. When the quality factor approaches 0, it indicates that the average three-axis attitude error is very large, and this attitude error is considered to be the "worst extreme case".

[0076] Specifically, step S4 includes the following steps:

[0077] The single-frame attitude quality factors of the star sensors were summarized and categorized, and the current frame attitude error of the star sensors was evaluated. The evaluation results are shown in Table 1 below:

[0078] Table 1

[0079]

[0080]

[0081] The evaluation results indicate that:

[0082] 1) When the single-frame attitude quality factor QI of the star sensor is greater than 0.95 and the corresponding three-axis attitude average error ε(1σ)<1”, it is considered that the attitude of the current frame meets the accuracy index requirements, and it is recommended that the user can directly use the attitude.

[0083] 2) When the single-frame attitude quality factor QI of the star sensor is between 0.8 and 0.95, and the corresponding three-axis attitude average error ε(1σ) is between 1” and 2”, it is considered that the attitude accuracy of the current frame has decreased, and it is recommended that the user consider whether to use the attitude.

[0084] 3) When the single-frame attitude quality factor QI of the star sensor is less than 0.8, and the corresponding three-axis attitude average error ε(1σ)>2”, it is considered that the attitude error of the current frame is large (unreliable), and it is recommended that the user not use the attitude.

[0085] In summary, the present invention provides an on-orbit evaluation method for the single-frame attitude accuracy of a star sensor. By calculating the covariance matrix of a single frame of the star sensor and constructing a "quality factor," it achieves real-time on-orbit computational evaluation of the single-frame attitude accuracy of the star sensor. This on-orbit evaluation method does not involve complex convolutions or integrals, fully meets the computational complexity requirements of spacecraft processors, and offers superior real-time computational performance. Furthermore, the introduced quality factor can directly characterize the attitude accuracy of the star sensor. This attitude accuracy can not only guide users in using the output attitude of the star sensor but also serve as a reference criterion for some internal functional items of the star sensor product, thereby improving the reliability of the star sensor product.

[0086] 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 invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. An on-orbit evaluation method for the single-frame attitude accuracy of a star sensor, characterized in that, It includes the following steps: S1, combine the combined values ​​of all star vector measurement noise variances to calculate the single-frame attitude covariance matrix of the star sensor; S2, Evaluate the three-axis attitude error of the star sensor based on the attitude covariance matrix; S3, Calculate the single-frame attitude quality factor of the star sensor based on the three-axis attitude error value of the star sensor; S4, Evaluate the attitude error of the star sensor based on the quality factor; Among them, the synthesized value of the star vector measurement noise variance The calculation formula is: In equation (1), A is the attitude transition matrix calculated by the star sensor in the current frame, and V i To measure the standard star vector corresponding to the star vector in the star catalog; W i The stellar vector is used for measurement; n is the number of stars involved in the attitude calculation. The formula for calculating the single-frame attitude covariance matrix P of the star sensor is as follows: In equation (2), a i To measure the star vector weights, W i T To measure the transpose of the star vector; The formulas for calculating the three-axis attitude error of the star sensor are as follows: In equation (3), Cov_X represents the X-axis attitude error of the star sensor, Cov_Y represents the Y-axis attitude error of the star sensor, and Cov_Z represents the Z-axis attitude error of the star sensor; P[1,1], P[2,2], and P[3,3] represent the three diagonal elements of the covariance matrix P in sequence.

2. The on-orbit evaluation method for single-frame attitude accuracy of star sensors as described in claim 1, characterized in that, Step S1 includes: S1.1, Calculate the composite value of the noise variance for all star vector measurements. S1.2, the composite value of noise variance is measured using the star vector. Calculate the single-frame attitude covariance matrix P of the star sensor.

3. The on-orbit evaluation method for single-frame attitude accuracy of star sensors as described in claim 1, characterized in that, Step S3 includes: S3.1, Calculate the average three-axis attitude error ε of the star sensor; S3.2, Calculate the single-frame attitude quality factor QI of the star sensor using the average three-axis attitude error ε of the star sensor.

4. The on-orbit evaluation method for single-frame attitude accuracy of star sensors as described in claim 3, characterized in that, The formula for calculating the average three-axis attitude error ε of the star sensor is as follows: In the formula, weight X Weights are assigned to the X-axis attitude error of the star sensor. Y Weights are assigned to the Y-axis attitude error of the star sensor. Z Assign weights to the Z-axis attitude error of the star sensor.

5. The on-orbit evaluation method for single-frame attitude accuracy of star sensors as described in claim 4, characterized in that, The formula for calculating the single-frame attitude quality factor (QI) of the star sensor is as follows: In the formula, These are the parameters of the quality factor transfer function.

6. The on-orbit evaluation method for single-frame attitude accuracy of star sensors as described in claim 5, characterized in that, The evaluation of the star sensor attitude error based on the quality factor includes: If the single-frame attitude quality factor (QI) of the star sensor is greater than 0.95, then the attitude of the current frame is considered to meet the accuracy index requirements.

7. The on-orbit evaluation method for single-frame attitude accuracy of star sensors as described in claim 6, characterized in that, The evaluation of the star sensor attitude error based on the quality factor also includes: When the single-frame attitude quality factor (QI) of the star sensor is between 0.8 and 0.95, the attitude accuracy of the current frame is considered to have decreased. If the single-frame attitude quality factor (QI) of the star sensor is less than 0.8, the attitude error of the current frame is considered to be large.

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