CN109655081B - On-orbit adaptive correction method and system for star sensor optical system parameters - Google Patents
On-orbit adaptive correction method and system for star sensor optical system parameters Download PDFInfo
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Abstract
The invention relates to an on-orbit self-adaptive correction method and system for optical system parameters of a star sensor. The on-orbit adaptive correction method for the parameters of the optical system of the star sensor comprises the following steps: acquiring parameters of an optical system of the star sensor; and performing on-orbit updating on the focal length of the star sensor by an extended Kalman filtering method. The correction method and the system only optimize the focal length, thereby greatly reducing the calculated amount and further improving the feasibility and the reliability of the correction method and the correction system; furthermore, an EKF algorithm is adopted for filtering, so that the influence of noise on a focal length updating result is reduced, and the stability of the system is further improved.
Description
Technical Field
The invention relates to the technical field of star sensors, in particular to an on-orbit adaptive correction method and system for parameters of an optical system of a star sensor.
Background
The star sensor is the attitude sensor with the highest precision at present and is widely applied to satellite attitude determination. The low-frequency error is the bottleneck of improving the precision of the star sensor, the error of the optical system is an important component of the low-frequency error, the error can be effectively reduced by calibrating the optical system, and the calibration of the optical system comprises ground calibration and on-orbit calibration.
The high-precision star table is a common standard for on-orbit calibration, and Griffith of Texas A & M University-college Station applies forgetting factor recursive least squares to the optimization calculation of optical system parameters according to the angular distance between stars calculated by the star table so as to increase the weight of new data in calculation, prevent parameter drift and analyze the stability and convergence of the algorithm.
The Liuhai wave of national defense science provides another on-orbit calibration algorithm combining least square iteration with Kalman filtering. The lens temperature distortion compensation is applied to the on-track correction by the great Sunday of Harmony, and the accuracy of the on-track correction is improved through simulation analysis, but only radial distortion is considered, tangential distortion is not considered, and the change of defocus is not considered.
Although the above research uses star catalogue reference, optimization is not performed according to inter-star angular distance information, and madhaumita.pal, an aerospace engineering research institute of india academy of sciences, applies a closed-form solution to on-orbit parameter estimation and simultaneously calculates elements and postures in the star sensor. The gunn professor in the great university of the harbourne industry also uses this solution for parameter estimation, but applies a different distortion model. The Wei Xin doctor of the university of aerospace of Beijing proposes an on-orbit correction algorithm based on RAC constraint, calculates external parameters and internal parameters from a single-frame star map in a step-by-step manner, and performs integral optimization on the internal parameters by using a multi-frame star map. The optimization method of the internal parameters is improved on the basis of the juan doctor, and Kalman filtering iteration is provided as the optimal estimation of the internal parameters. Compared with the angular distance reference between stars, the algorithm cannot unconditionally decouple internal and external parameters of the star sensor, the external parameters need to be recalculated for each frame of star map, and the calculation result is greatly influenced by noise.
How to efficiently and reliably carry out the on-orbit adaptive correction of the parameters of the optical system of the planetary sensor becomes one of the problems to be solved urgently by the technical personnel in the field.
Disclosure of Invention
The invention aims to provide an on-orbit adaptive correction method and system for optical system parameters of a star sensor, which can efficiently and reliably realize the on-orbit adaptive correction of the optical system parameters of the star sensor.
In order to achieve the above object, the present invention provides an on-orbit adaptive correction method for star sensor optical system parameters, comprising:
acquiring parameters of an optical system of the star sensor;
and performing on-orbit updating on the focal length of the star sensor by an extended Kalman filtering method.
In some embodiments, the step of performing on-orbit updating on the focal length of the star sensor through the extended kalman filtering method includes:
performing on-orbit updating on the focal length of the star sensor according to the formula (1);
wherein the content of the first and second substances,
is the angular distance error between the stars; m iskIs the current internal element; pkState variance of the K-frame star map; hkIs composed of
Relative mkPartial derivatives of (a).
In some embodiments, the obtaining step of obtaining the inter-satellite angular distance error by formula (2) includes:
wherein: v. ofiIs a star vector v under the inertial system corresponding to the ith star pointi TvjIs the cosine value of the included angle between the ith inertia system star vector and the jth inertia system star vector, Fij(mk) The internal element is mkAnd calculating the cosine value of the inter-satellite included angle by using the coordinates of the satellite points.
In some embodiments, obtaining inter-satellite angle cosine values from the coordinates of the star points is obtained according to equation (3):
Fij(mk)＝wT(mk)w(mk) (3)
wherein, w (m)k) The internal element is mkAnd calculating a star vector under the coordinate system of the star sensor by using the star point coordinates.
In certain embodiments, the obtaining is according to equation (4)
Relative mkPartial derivative of (H)k；
In some embodiments, the method for on-orbit adaptive correction of the optical system parameters of the star sensor further includes: acquiring the state quantity of the K +1 frame according to the formula (5):
in some embodiments, the method for on-orbit adaptive correction of the parameters of the optical system of the star sensor further comprises: the state variance of the K +1 frame is obtained according to equation (6):
the invention also provides an on-orbit adaptive correction system for the parameters of the optical system of the star sensor, which comprises the following components:
the parameter acquisition module is used for acquiring the optical system parameters of the star sensor;
and the focal length updating module is used for performing on-orbit updating on the focal length of the star sensor by an extended Kalman filtering method.
In summary, compared with the prior art, the on-orbit adaptive correction method and system for the optical system parameters of the star sensor of the invention have the following advantages:
according to the correction method and the correction system, the inter-satellite angular distance is calculated based on the star catalogue, so that the measurement precision is improved; meanwhile, parameter optimization is carried out by utilizing an inter-satellite angular distance criterion which is very sensitive to focal length change, so that decoupling of internal and external parameters is realized; in addition, the correction method and the correction system only optimize the focal length, thereby greatly reducing the calculated amount and further improving the feasibility and the reliability of the correction method and the correction system; furthermore, an EKF algorithm is adopted for filtering, so that the influence of noise on a focal length updating result is reduced, and the stability of the system is further improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive labor.
FIG. 1 is a schematic flow chart of an implementation of the on-orbit adaptive correction method for the parameters of the star sensor optical system according to the present invention;
fig. 2 is a schematic structural diagram of an implementation manner of the on-orbit adaptive correction system for the parameters of the star sensor optical system of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is noted that, in this document, relational terms such as "first," "second," "third," and the like, if any, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrases "comprising … …" or "comprising … …" does not exclude the presence of additional elements in a process, method, article, or terminal that comprises the element. Further, herein, "greater than," "less than," "more than," and the like are understood to exclude the present numbers; the terms "above", "below", "within" and the like are to be understood as including the number.
In the following description, reference is made to the accompanying drawings that describe several embodiments of the invention. It is to be understood that other embodiments may be utilized and that mechanical, structural, electrical, and operational changes may be made without departing from the spirit and scope of the present disclosure. The following detailed description is not to be taken in a limiting sense, and the scope of embodiments of the present invention is defined only by the claims of the issued patent. Spatially relative terms, such as "upper," "lower," "left," "right," "lower," "below," "lower," "above," "upper," and the like, may be used herein to facilitate describing one element or feature's relationship to another element or feature as illustrated in the figures.
As described above, the optical system parameters are ground calibrated during the manufacture of the star sensor, but there are many factors that cause the calibration parameters to change during the in-orbit use, such as the change of the spatial refractive index compared to the ground calibration environment, thermal deformation, vibration during emission, and aging of components. By in-orbit calibration, the optical system parameters are adjusted periodically, which helps to maintain measurement accuracy throughout the service life. The method is different from the prior method of optimizing the focal length, the principal point and the distortion simultaneously, the applicant of the invention considers that the focal length is the main factor of the on-orbit change, only one-dimensional filtering is carried out on the focal length, and the principal point and the distortion still use ground calibration parameters so as to enhance the reliability of on-orbit calibration. Meanwhile, the applicant of the invention considers that the inter-satellite angular distance criterion can better realize the decoupling of internal and external parameters, is sensitive to the focal length change, and adopts the inter-satellite angular distance criterion for optimization because distortion correction is not needed.
The technical solution of the present invention will be described in detail with specific examples in conjunction with fig. 1 to 2. The following several specific embodiments may be combined with each other, and details of the same or similar concepts or processes may not be repeated in some embodiments.
Fig. 1 is a schematic flow chart showing an implementation manner of the on-orbit adaptive correction method for the parameters of the star sensor optical system of the present invention, as shown in fig. 1, the method includes:
step S10, acquiring star sensor optical system parameters;
and step S20, performing on-orbit updating on the focal length of the star sensor by an extended Kalman filtering method.
In this embodiment, the process of performing the on-track update on the focal length of the star sensor in step S20 through the extended kalman filter method can refer to the following detailed description.
Firstly, the initial value m of the element in the star sensor is set0As an initial value of kalman filtering, the initial value of the state variance is P0Processing the star map frame by frame, and for the k frame star map, processing as follows:
wherein, the inter-satellite angular distance error is obtained through a formula (2):
wherein v isiFor the star vector under the inertial system corresponding to the ith star point (matching in the star tracking process), vi TvjIs the cosine value of the included angle between the ith inertia system star vector and the jth inertia system star vector, Fij(mk) The internal element is mkThe cosine value of the included angle between the stars is calculated by the coordinates of the star points, as shown in the formula (3), w (m)k) The internal element is mkAnd calculating a star vector under the coordinate system of the star sensor by using the star point coordinates.
Fij(mk)＝wT(mk)w(mk) (3)
Then, it is obtained by the formula (4)
Relative mkPartial derivative of (H)k：
Because the internal parameters of the star sensor slowly change relative to the sampling frequency, the internal parameters are assumed to be unchanged, so that the state equation is
The prediction equation for the state variance is:
wherein Q is the variance of the process noise, and although we assume that the model parameters are not changed, it is necessary to ensure a certain process noise because the process noise can prevent P from being too small, and avoid the filter from ignoring new measurement information. R is the variance of the measured noise and is a diagonal matrix, and the selection of R is related to the noise equivalent angle of the star sensor.
In the specific application, an Extended Kalman Filtering (EKF) method is adopted to perform on-orbit updating on the focal length of the star sensor, and the processing is performed on the kth frame star map as follows:
step 1, element m in the currentkCalculating the cosine value F of the included angle between the stars according to the formula (3) by the coordinates of the star pointsij(mk)；
Step 2, calculating the angular distance error between the stars according to the formula (2)
Step 3, calculating according to the formula (4)
Relative mkPartial derivatives of (d);
step 4, calculating gain according to the formula (1), updating state quantity and updating state variance;
step 5, predicting the state quantity of the (k + 1) th frame according to the formula (5);
and 6, predicting the state variance of the (k + 1) th frame according to the formula (6).
And step 7, similarly processing steps 1-6 on the k +1 frame star map.
Fig. 2 is a schematic structural diagram of an implementation of the on-orbit adaptive correction system for the parameters of the star sensor optical system of the present invention, as shown in fig. 2, the system includes:
the parameter acquisition module 10 is used for acquiring the optical system parameters of the star sensor;
and the focal length updating module 20 is used for performing on-orbit updating on the focal length of the star sensor by using an extended Kalman filtering method.
The working process of the star sensor optical system parameter on-orbit adaptive correction system is explained in detail with reference to the attached drawings as follows:
firstly, updating the focal length of the star sensor in an on-orbit mode according to a formula (1);
wherein the content of the first and second substances,
is the angular distance error between the stars; m iskIs the current internal element; pkState variance of the K-frame star map; hkIs composed of
Relative mkPartial derivatives of (a).
Then, the step of obtaining the inter-satellite angular distance error through the formula (2) includes:
wherein: v. ofiIs a star vector v under the inertial system corresponding to the ith star pointi TvjIs the cosine value of the included angle between the ith inertia system star vector and the jth inertia system star vector, Fij(mk) The internal element is mkAnd calculating the cosine value of the inter-satellite included angle by using the coordinates of the satellite points.
Then, acquiring a cosine value of an inter-satellite included angle acquired by the star point coordinates according to a formula (3):
Fij(mk)＝wT(mk)w(mk) (3)
wherein, w (m)k) The internal element is mkAnd calculating a star vector under the coordinate system of the star sensor by using the star point coordinates.
Then, it is obtained according to the formula (4)
Relative mkPartial derivative of (H)k；
Then, the state quantity of the K +1 frame is obtained according to the formula (5):
finally, the state variance of the K +1 frame is obtained according to equation (6):
compared with the prior art, the on-orbit adaptive correction method and the system for the parameters of the optical system of the star sensor have the following advantages that:
according to the correction method and the correction system, the inter-satellite angular distance is calculated based on the star catalogue, so that the measurement precision is improved; meanwhile, parameter optimization is carried out by utilizing an inter-satellite angular distance criterion which is very sensitive to focal length change, so that decoupling of internal and external parameters is realized; in addition, the correction method and the correction system only optimize the focal length, thereby greatly reducing the calculated amount and further improving the feasibility and the reliability of the correction method and the correction system; furthermore, an EKF algorithm is adopted for filtering, so that the influence of noise on a focal length updating result is reduced, and the stability of the system is further improved.
As will be appreciated by one skilled in the art, the above-described embodiments may be provided as a method, apparatus, or computer program product. These embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. All or part of the steps in the methods according to the embodiments may be implemented by a program instructing related hardware, where the program may be stored in a storage medium readable by a computer device and used to execute all or part of the steps in the methods according to the embodiments.
As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used in this specification, specify the presence of stated features, steps, operations, elements, components, items, species, and/or groups, but do not preclude the presence, or addition of one or more other features, steps, operations, elements, components, species, and/or groups thereof. The terms "or" and/or "as used herein are to be construed as inclusive or meaning any one or any combination. Thus, "A, B or C" or "A, B and/or C" means "any of the following: a; b; c; a and B; a and C; b and C; A. b and C ". An exception to this definition will occur only when a combination of elements, functions, steps or operations are inherently mutually exclusive in some way.
The various embodiments described above are described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a computer apparatus to produce a machine, such that the instructions, which execute via the processor of the computer apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.
Claims (6)
1. An on-orbit adaptive correction method for optical system parameters of a star sensor is characterized by comprising the following steps:
acquiring parameters of an optical system of the star sensor;
performing on-orbit updating on the focal length of the star sensor by an extended Kalman filtering method; the method specifically comprises the following steps:
performing on-orbit updating on the focal length of the star sensor according to the formula (1);
wherein the content of the first and second substances,
is the angular distance error between the stars; m iskIs the current internal element; pkState variance of the K-frame star map; hkIs composed of
Relative mkPartial derivatives of (d);
obtaining the angular distance error between the satellites through a formula (2):
wherein: v. ofiIs a star vector v under the inertial system corresponding to the ith star pointi TvjIs the cosine value of the included angle between the ith inertia system star vector and the jth inertia system star vector, Fij(mk) The internal element is mkAnd calculating the cosine value of the inter-satellite included angle by using the coordinates of the satellite points.
2. The star sensor optical system parameter on-orbit adaptive correction method according to claim 1, characterized in that the inter-star angle cosine values obtained from the star point coordinates are obtained according to formula (3):
Fij(mk)＝wT(mk)w(mk) (3)
wherein, w (m)k) The internal element is mkAnd calculating a star vector under the coordinate system of the star sensor by using the star point coordinates.
3. The star sensor optical system parameter on-orbit adaptive correction method of claim 1, characterized in that the acquisition is performed according to formula (4)
Relative mkPartial derivative of (H)k；
4. The star sensor optical system parameter on-orbit adaptive correction method according to claim 1, characterized in that, further comprising: acquiring the state quantity of the K +1 frame according to the formula (5):
5. the star sensor optical system parameter on-orbit adaptive correction method according to claim 1, characterized in that, further comprising: the state variance of the K +1 frame is obtained according to equation (6):
6. an on-orbit adaptive correction system for optical system parameters of a star sensor, which is suitable for the on-orbit adaptive correction method for the optical system parameters of the star sensor as claimed in any one of claims 1 to 5, and which comprises:
the parameter acquisition module is used for acquiring the optical system parameters of the star sensor;
and the focal length updating module is used for performing on-orbit updating on the focal length of the star sensor by an extended Kalman filtering method.
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