A high-precision prediction method for satellite inertial attitude suitable for large time delay

Abstract

This invention relates to a high-precision prediction method for satellite inertial attitude applicable to large time delays. The method constructs a projection relationship between satellite motion characteristics and predicted attitude, and uses linear difference of reference attitude and adaptive polynomial fitting for attitude extrapolation in dynamic and steady-state processes, respectively, to achieve high-precision attitude prediction in the initial stage of dynamic positioning and stable tracking process, ensuring the extrapolation accuracy of satellite attitude maneuvering and stable tracking process under large time delays.

Description

Technical Field

[0001] This invention relates to a high-precision prediction method for satellite inertial attitude applicable to large time delays, belonging to the field of spacecraft control technology. Background Technology

[0002] The inertial attitude of a satellite can be measured in real time, typically obtained through co-filtering with star-sensitive gyroscopes. This information is used by the attitude control unit and can also serve as an output interface for other subsystems. For example, the information processing subsystem of a remote sensing satellite requires inertial attitude information for real-time image association matching. However, due to hardware limitations in the information transmission process, the attitude information obtained by the information processing subsystem may have a significant time delay, for example, 2 seconds. To ensure the accuracy of image association matching, the satellite attitude accuracy needs to be on the order of arcseconds. In other words, the information processing system needs to obtain a high-precision real-time attitude prediction value; otherwise, it will directly affect the accuracy of target matching and association. Traditional attitude prediction methods are mainly suitable for situations with relatively short extrapolation periods. Summary of the Invention

[0003] The technical problem to be solved by this invention is: to improve the extrapolation accuracy of satellite attitude maneuvering and stable tracking under large time delay, a high-precision prediction method for satellite inertial attitude suitable for large time delay is proposed. In the satellite attitude maneuvering process, linear difference extrapolation based on reference attitude is used, while in the case where the expected attitude is unknown in the steady state process, adaptive polynomial fitting based on order and historical data is used for attitude prediction. The two are intelligently and autonomously switched through scheduling logic to ensure the attitude prediction accuracy of the satellite motion in all stages.

[0004] The technical solution adopted in this invention is as follows:

[0005] A high-precision prediction method for satellite inertial attitude suitable for large time delays includes the following steps:

[0006] Step 1: Read the quaternion of the celestial body's inertial attitude and convert it into the satellite's inertial attitude angle;

[0007] Step 2: Perform polynomial adaptive fitting on the satellite's inertial attitude angle, extrapolate the attitude based on the fitting coefficients, and then proceed to Step 4.

[0008] Step 3: Perform attitude extrapolation based on linear interpolation, and then proceed to Step 4;

[0009] Step 4: Select the attitude extrapolation method based on the logical switching conditions to achieve high-precision prediction of satellite inertial attitude.

[0010] Furthermore, the quaternion of the celestial body's inertial attitude is converted into the satellite's inertial attitude angle, specifically as follows:

[0011] The quaternion of the celestial body's inertial attitude is converted into three-axis inertial Euler angles, and appropriate handling is performed to prevent attitude jumps of ±180 degrees. Specifically:

[0012] For the roll angle φ t :

[0013] φ t (k)=φ t (k-1)+f(φ t (k)-φ t (k-1))

[0014] Where, φ t (k) is the measured value of the roll angle for the current shot, φ t (k-1) is the measured value of the rolling angle in the previous frame. For any variable x∈R, x0 = x - 2nπ, where n is an integer rounded up from 2π; the pitch and yaw angles are calculated similarly.

[0015] Furthermore, the polynomial adaptive fitting of the satellite inertial attitude angle is performed based on multi-frame three-axis inertial Euler angles and their time-scaled historical data. The order of the polynomial and the length of the historical data can be adjusted.

[0016] Furthermore,

[0017] The process of polynomial fitting is as follows:

[0018] (1) For the rolling axis, the formula for calculating the fitting parameter matrix p1 is as follows:

[0019]

[0020] in,

[0021]

[0022]

[0023] φ t (k) represents the measured roll angle corresponding to the current frame, and its corresponding time scale is t(k). s k represents the number of shots in the historical data. r The order of the polynomial;

[0024] (2) The initial value is the order of the bound polynomial and the number of historical data beats. The extrapolated attitude is saved and compared with the attitude at the actual corresponding moment. Accuracy statistics are performed. If the accuracy does not meet the requirements, the order of the polynomial and the number of historical data beats are modified and adjusted until the accuracy meets the requirements.

[0025] (3) Similarly, perform polynomial fitting for pitch and yaw axes according to steps (1) to (2).

[0026] Furthermore, the attitude extrapolation based on the fitting coefficients specifically involves:

[0027] Assume the measurement delay is t d If the current actual scroll angle is in seconds, then the predicted value is...

[0028]

[0029] The current actual pitch angle and the current actual yaw angle are treated the same.

[0030] Furthermore, the attitude extrapolation based on linear interpolation specifically involves:

[0031]

[0032] Where ΔT is the time difference between the current shot and the previous shot.

[0033] Furthermore, the attitude extrapolation method based on logical switching conditions specifically includes:

[0034] Logical judgment is made based on whether the satellite is in a dynamic or steady-state process. If the satellite is in a dynamic process, attitude extrapolation based on linear interpolation is introduced; if the satellite is in a steady-state process, attitude extrapolation based on polynomial fitting is introduced to achieve high-precision attitude extrapolation throughout the entire process.

[0035] The dynamic process refers to the rapid attitude maneuvering acquisition phase; the steady-state process refers to the stable tracking phase after the attitude maneuver is in place.

[0036] Secondly, the present invention also proposes a processor for running a program, wherein the program executes the aforementioned high-precision prediction method for satellite inertial attitude suitable for large time delays.

[0037] Thirdly, the present invention also proposes a non-volatile storage medium, comprising: a computer program product, which, when executed, performs the aforementioned high-precision prediction method for satellite inertial attitude applicable to large time delays.

[0038] Fourthly, the present invention also proposes a computer program product that, when executed by a processor, implements the high-precision prediction method for satellite inertial attitude applicable to large time delays.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] (1) Existing satellite attitude extrapolation methods are not suitable for situations with long extrapolation periods. This invention proposes a novel prediction method for determining the real-time inertial attitude of satellites under conditions of large transmission delay. This method fully exploits the attitude characteristics of the dynamic and steady-state processes of attitude maneuvering, and autonomously schedules the reference attitude linear difference and adaptive polynomial fitting extrapolation algorithm based on kinematic and operational mode characteristics to ensure high-precision attitude prediction in the initial stage of dynamic positioning and the stable tracking process. This method has not appeared in existing papers or patents and is novel.

[0041] (2) This invention proposes a high-precision inertial attitude extrapolation algorithm applicable to the entire process under large time delay. This method can effectively solve the problem of high-precision attitude estimation under long extrapolation periods through on-board autonomous optimization and adaptive estimation. The entire algorithm design is simple and the parameter debugging workload is small.

[0042] (3) This invention proposes a new solution to the problem of high-precision attitude estimation under long extrapolation period. It does not require additional data input, is simple to calculate, and can be adapted to a large class of satellite systems with similar attitude extrapolation requirements. It has strong engineering practicality. Attached Figure Description

[0043] Figure 1 This is a flowchart of the method of the present invention;

[0044] Figure 2 This is a schematic diagram of the satellite's inertial attitude angle (deg).

[0045] Figure 3 A schematic diagram of the celestial attitude prediction error (deg). Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0047] like Figure 1 As shown, this invention relates to a high-precision prediction method for satellite inertial attitude suitable for large time delays, comprising the following steps:

[0048] Step 1: Read the quaternion of the celestial body's inertial attitude and convert it into the satellite's inertial attitude angle;

[0049] Step 2: Perform polynomial adaptive fitting on the satellite's inertial attitude angle, extrapolate the attitude based on the fitting coefficients, and then proceed to Step 4.

[0050] Step 3: Perform attitude extrapolation based on linear interpolation, and then proceed to Step 4;

[0051] Step 4: Select the attitude extrapolation method based on the logical switching conditions to achieve high-precision prediction of satellite inertial attitude.

[0052] The specific process of step one is as follows:

[0053] The quaternion of the celestial body's inertial attitude is converted into three-axis inertial Euler angles, and appropriate handling is performed to prevent attitude jumps of ±180 degrees. Specifically:

[0054] For the roll angle φ t :

[0055] φ t (k)=φ t (k-1)+f(φ t (k)-φ t (k-1))

[0056] Where, φ t (k) is the measured value of the roll angle for the current shot, φ t (k-1) is the measured value of the rolling angle in the previous frame. For any variable x∈R, x0 = x - 2nπ, where n is an integer rounded up from 2π; the pitch and yaw angles are calculated similarly.

[0057] In step two, the polynomial adaptive fitting of the satellite inertial attitude angle is performed, that is, polynomial fitting is performed based on multi-frame three-axis inertial Euler angles and their time-scaled historical data. The order of the polynomial and the length of the historical data can be adjusted.

[0058] Taking a rolling shaft as an example,

[0059] (2.1) For the rolling axis, the formula for calculating the fitting parameter matrix p1 is as follows:

[0060]

[0061] in,

[0062]

[0063] φ t (k) represents the measured roll angle corresponding to the current frame, and its corresponding time scale is t(k). s k represents the number of shots in the historical data. r The order of the polynomial;

[0064] (2.2) The initial value is the order of the bound polynomial and the number of historical data beats. The extrapolated attitude is saved and compared with the attitude at the actual corresponding moment. Accuracy statistics are performed. If the accuracy does not meet the requirements, the order of the polynomial and the number of historical data beats are modified and adjusted until the accuracy meets the requirements.

[0065] (2.3) Similarly, perform polynomial fitting for the pitch axis and yaw axis according to steps (2.1) to (2.2).

[0066] In step three, attitude extrapolation is performed based on the fitting coefficients.

[0067] Assume the measurement delay is t d If the current actual scroll angle is in seconds, then the predicted value is...

[0068]

[0069] The same treatment can be applied to the pitch and yaw axes.

[0070] In step four, attitude extrapolation based on linear interpolation is performed, specifically as follows:

[0071]

[0072] Where ΔT is the time difference between the current shot and the previous shot.

[0073] In step five, attitude extrapolation is selected based on logical switching conditions.

[0074] Polynomial fitting extrapolation method has high steady-state prediction accuracy but poor dynamic characteristics. Combining the kinematic characteristics of the satellite, linear difference is introduced in the dynamic process through logical switching conditions, and polynomial fitting is autonomously introduced in the steady-state process to achieve high-precision attitude extrapolation throughout the entire process.

[0075] Specifically, the system makes logical judgments based on whether the satellite is in a dynamic or steady-state process. If the satellite is in a dynamic process, attitude extrapolation based on linear interpolation is introduced; if the satellite is in a steady-state process, attitude extrapolation based on polynomial fitting is introduced to achieve high-precision attitude extrapolation throughout the entire process.

[0076] The dynamic process refers to the rapid attitude maneuvering acquisition phase; the steady-state process refers to the stable tracking phase after the attitude maneuver is in place.

[0077] The present invention will be further described below with reference to the embodiments.

[0078] Example:

[0079] Using a specific satellite as an example, a set of typical on-orbit operating conditions were used to simulate and verify the method proposed in this patent application. The satellite initially operates in normal Earth-orbit mode. At t=200s, attitude maneuvers begin, achieving target acquisition through rapid maneuvers. The satellite reaches target position at t=248s. At this point, high-precision attitude extrapolation is required for image matching and association. At t=250s, the information processing system successfully outputs image information, and the target transitions to a stable tracking phase based on image feedback. The system defaults to using a 4th-order polynomial with 5 seconds of historical data. Through self-correction via prediction accuracy feedback, the polynomial order is adjusted to 5th order. The attitude prediction accuracy during the maneuver to target position is better than 0.003 degrees, and the attitude prediction accuracy during stable tracking is better than 2e-4 degrees. Specific simulation curves are shown below. Figures 2-3 .

[0080] The contents not described in detail in this specification are common knowledge to those skilled in the art.

[0081] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A high-precision prediction method for satellite inertial attitude suitable for large time delays, characterized in that, include: Step 1: Read the quaternion of the celestial body's inertial attitude and convert it into the satellite's inertial attitude angle; Step 2: Perform polynomial adaptive fitting on the satellite's inertial attitude angle, extrapolate the attitude based on the fitting coefficients, and then proceed to Step 4. Step 3: Perform attitude extrapolation based on linear interpolation, and then proceed to Step 4; Step 4: Select the attitude extrapolation method based on logical switching conditions to achieve high-precision prediction of satellite inertial attitude; the specific steps of selecting the attitude extrapolation method based on logical switching conditions are as follows: Logical judgment is made based on whether the satellite is in a dynamic or steady-state process. If the satellite is in a dynamic process, attitude extrapolation based on linear interpolation is introduced; if the satellite is in a steady-state process, attitude extrapolation based on polynomial fitting is introduced to achieve high-precision attitude extrapolation throughout the entire process. The dynamic process refers to the rapid attitude maneuvering acquisition phase; the steady-state process refers to the stable tracking phase after the attitude maneuver is in place.

2. The high-precision prediction method for satellite inertial attitude applicable to large time delays according to claim 1, characterized in that: The quaternion of the celestial body's inertial attitude is converted into the satellite's inertial attitude angle, specifically as follows: The quaternion of the celestial body's inertial attitude is converted into three-axis inertial Euler angles, and appropriate handling is performed to prevent attitude jumps of ±180 degrees. Specifically: For roll angle : in, This is the measured value of the roll angle for the current shot. The measured value of the rolling angle in the previous frame, for any variable , , , To Round up to the nearest integer; the same applies to pitch and yaw angles.

3. The high-precision prediction method for satellite inertial attitude suitable for large time delays according to claim 2, characterized in that: The process of performing polynomial adaptive fitting on the satellite's inertial attitude angle involves performing polynomial fitting based on multi-frame three-axis inertial Euler angles and their time-scaled historical data. The order of the polynomial and the length of the historical data can be adjusted.

4. The high-precision prediction method for satellite inertial attitude suitable for large time delays according to claim 3, characterized in that: The process of polynomial fitting is as follows: (1) For the scroll axis, the fitting parameter matrix The calculation formula is in, ， The measured value of the roll angle corresponding to the current shot, and its corresponding time scale is: , For historical data, the number of shots. The order of the polynomial; (2) The initial value is the order of the bound polynomial and the number of historical data beats. The extrapolated attitude is saved and compared with the attitude at the actual corresponding moment. Accuracy statistics are performed. If the accuracy does not meet the requirements, the order of the polynomial and the number of historical data beats are modified and adjusted until the accuracy meets the requirements. (3) Similarly, perform polynomial fitting for pitch and yaw axes according to steps (1) to (2).

5. The high-precision prediction method for satellite inertial attitude suitable for large time delays according to claim 4, characterized in that: The attitude extrapolation based on the fitting coefficients is specifically as follows: Assuming the measurement delay is If the current actual scroll angle is in seconds, then the predicted value is... The current true pitch angle and the current true yaw angle are treated the same.

6. The high-precision prediction method for satellite inertial attitude suitable for large time delays according to claim 4, characterized in that: The attitude extrapolation based on linear interpolation is specifically performed as follows: in, This is the time difference between the current shot and the previous shot.

7. A processor, characterized in that, The processor is used to run a program, wherein the program executes the high-precision satellite inertial attitude prediction method applicable to large time delays as described in any one of claims 1 to 6.

8. A non-volatile storage medium, characterized in that, include: A computer program product that, when executed, performs the high-precision satellite inertial attitude prediction method applicable to large time delays as described in any one of claims 1 to 6.

9. A computer program product, characterized in that, When the computer program product is executed by the processor, it implements the high-precision prediction method for satellite inertial attitude applicable to large time delays as described in any one of claims 1 to 6.

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