Real-time compensation method for pointing error of laser communication terminal based on orbit space-time characteristics and space-borne laser communication terminal

Abstract

A laser communication terminal pointing error real-time compensation method based on track space-time characteristics and a satellite-borne laser communication terminal, the method uses the periodicity of satellite orbit operation, through multi-orbit period, angle partition iterative learning and compensation, the installation angle deviation caused by slow-changing factors such as installation surface thermal deformation is systematically corrected, specifically comprising: in the first orbit period, when the terminal runs to a preset angle partition, the system synchronously records and calculates the pointing error in the interval; from the second orbit period, when the terminal runs to the angle partition that has been learned again, the system automatically injects the installation angle deviation of the partition learned and saved in the last orbit as a feedforward compensation amount to pre-correct the current pointing; through the operation of multiple continuous orbit periods, all commonly used working angles of the terminal can be gradually covered. The application ensures that the pointing accuracy of the terminal can be dynamically maintained and continuously optimized in long-term on-orbit tasks.

Description

Technical Field

[0001] This invention belongs to the field of space laser communication technology, specifically relating to a real-time compensation method for pointing error of a laser communication terminal based on machine learning and orbital spatiotemporal characteristics, and a spaceborne laser communication terminal. Background Technology

[0002] With the rapid development of low-Earth orbit satellite constellations and space information networks, spaceborne laser communication has become an important technical means for inter-satellite and space-to-ground communication due to its advantages such as high bandwidth, high speed, strong anti-interference capability, and good confidentiality. Laser communication terminals have extremely high requirements for pointing accuracy during communication; pointing errors directly affect the acquisition probability, stability, and communication quality of the communication link.

[0003] In actual on-orbit operation, laser communication terminals are typically installed on satellite structural platforms. Affected by factors such as periodic changes in orbital illumination, fluctuations in the thermal environment, and the release of structural stress, the terminal mounting surface experiences minute thermal deformations or attitude shifts, introducing pointing errors that vary slowly over time. These errors are characterized by long variation periods, small amplitudes, but significant cumulative effects, making them difficult to eliminate in the long term through one-time ground calibration or static compensation.

[0004] Existing technologies for correcting pointing errors in laser communication terminals mainly include precise ground calibration, uniform installation angle compensation across the entire field of view, and correction methods based on temperature or structural models. These methods typically assume that the installation angle deviation remains consistent throughout the pointing range. However, in complex on-orbit environments, terminal pointing errors often exhibit non-uniform distribution characteristics closely related to the pointing angle and orbital period, making it difficult for traditional methods to simultaneously achieve both compensation accuracy and system real-time performance.

[0005] Furthermore, with the trend towards miniaturization and lightweighting of laser communication terminals, onboard computing and storage resources are severely limited, making it difficult to implement compensation schemes using highly complex models or large-scale data storage in engineering. Moreover, as the number of terminals in orbit increases, on-orbit maintenance becomes increasingly complex. Therefore, there is an urgent need for a technical solution that can fully utilize orbital operational patterns and achieve long-term stable correction of laser communication terminal pointing errors under limited computing and storage resources. Summary of the Invention

[0006] This invention addresses the problem of persistent and effective correction of pointing errors caused by slowly varying factors such as thermal deformation of the mounting surface and stress release of the structure due to periodic changes in the orbital thermal environment during long-term link establishment in existing laser communication terminals. The aim is to propose a real-time pointing error compensation method for laser communication terminals based on machine learning and orbital spatiotemporal characteristics, and a corresponding spaceborne laser communication terminal. This method utilizes the periodicity of satellite orbital operation, employing iterative learning and compensation across multiple orbital periods and angular intervals to systematically correct pointing errors caused by slowly varying factors such as thermal deformation of the mounting surface. The pointing state corresponding to the terminal under recurring orbital positions and attitudes is used as the learning object. By establishing and dynamically updating an angular-regional mounting angle deviation mapping table, online learning, dynamic compensation, and long-term stable correction of the terminal's pointing error are achieved.

[0007] The technical solution of this invention is as follows:

[0008] A real-time compensation method for pointing error of a laser communication terminal based on orbital spatiotemporal characteristics is characterized by the following steps:

[0009] S1. Based on the on-orbit working field of view of the laser communication terminal, the pointing space of the laser communication terminal is divided into N preset discrete angle partitions;

[0010] During the first orbital cycle in which a communication link is successfully established, when the laser communication terminal moves to any of the aforementioned angle partitions, it synchronously acquires the theoretical pointing vector and the actual pointing vector of that angle partition.

[0011] The difference between the two is calculated as the initial installation angle deviation corresponding to the angle partition, and the initial installation angle deviation is associated with and stored with the corresponding angle partition identifier to form an initial installation angle deviation mapping table.

[0012] S2. Starting from the second orbital cycle, when the laser communication terminal runs to a certain angle partition that has been learned again, the installation angle deviation currently stored in that angle partition is obtained as the feedforward compensation amount;

[0013] The feedforward compensation amount is superimposed with the current theoretical pointing instruction to form a corrected pointing instruction, and the corrected pointing instruction is sent to the pointing execution mechanism.

[0014] After the pre-calibration is completed, the residual pointing error after compensation is measured in real time, and the installation angle deviation of the corresponding angle zone is updated based on the residual pointing error.

[0015] S3. Through iterative operation of multiple consecutive orbital cycles, the learning and compensation of all commonly used working angle partitions of the laser communication terminal are gradually completed, forming an installation angle deviation mapping relationship for real-time correction of pointing errors.

[0016] Furthermore, the pointing error includes slowly varying pointing errors caused by thermal deformation of the mounting surface, structural stress release, and changes in the thermal environment.

[0017] Furthermore, the angle partitioning is based on at least one of the attitude angle, azimuth angle, and pitch angle pointed to by the line of sight of the laser communication terminal during satellite orbit operation.

[0018] Furthermore, the feedforward compensation amount is superimposed on the original installation angle in the form of installation angle deviation to obtain the corrected installation angle, and the theoretical value of terminal pointing is calculated based on the corrected installation angle.

[0019] Furthermore, the update of the installation angle deviation adopts an iterative learning algorithm, which includes at least one of weighted averaging, adaptive filtering, or least squares algorithm.

[0020] Furthermore, the angle partitioning gradually covers all commonly used working field of view of the laser communication terminal.

[0021] Furthermore, when the residual pointing error of a certain angle partition is less than a preset threshold, the update weight of the installation angle deviation of that angle partition is reduced.

[0022] Second, the present invention also provides a spaceborne laser communication terminal, including a control processing unit, a pointing actuator and a memory, wherein the control processing unit is configured to execute the laser communication terminal pointing error real-time compensation method described above.

[0023] Furthermore, the control processing unit is used to generate control signals based on theoretical pointing instructions and / or feedback signals; the pointing actuator is used to drive the optical components to move in response to the control signals; and the pointing measurement unit is used to measure the actual pointing deviation between the terminal optical axis and the target line of sight and feed it back to the control processing unit.

[0024] Compared with the prior art, the technical effects of the present invention are as follows:

[0025] 1) This invention makes full use of the periodic spatiotemporal characteristics of satellite orbit operation, and takes the repeated pointing state during the on-orbit operation of the laser communication terminal as the learning object, realizing cross-orbit iterative learning and adaptive compensation of pointing error, which can effectively track and correct pointing error drift caused by slow-changing factors such as thermal deformation of the mounting surface and release of structural stress.

[0026] 2) This invention divides the terminal pointing angle space into multiple angle partitions and performs error modeling and compensation for different angle partitions, overcoming the problem that the traditional full-field uniform installation angle correction method is difficult to take into account the accuracy of different pointing angles, and improving the overall pointing accuracy of the terminal under various working pointing angle conditions.

[0027] 3) This invention adopts a closed-loop learning mechanism that combines feedforward compensation and online updates, so that pointing errors can be pre-corrected before entering the control loop, reducing the control burden of the servo system and improving the acquisition stability and tracking accuracy of the laser communication link.

[0028] 4) This invention does not rely on complex physical thermal models or frequent ground recalibration, can operate online for a long time under spaceborne conditions, is suitable for space application environments with limited computing and storage resources, and has good engineering feasibility.

[0029] 5) This invention can achieve long-term dynamic maintenance and continuous optimization of the pointing accuracy of laser communication terminals without adding extra hardware, which is beneficial to improving the reliability and mission success rate of laser communication systems. Attached Figure Description

[0030] Figure 1 This is a flowchart of the real-time compensation method for pointing error of laser communication terminal based on machine learning and orbital spatiotemporal characteristics of the present invention.

[0031] Figure 2 This is a schematic diagram comparing the correction results of the method of the present invention with those of the traditional pointing error correction method. Detailed Implementation

[0032] The present invention will be further described below with reference to implementation examples and accompanying drawings, but this should not be construed as limiting the scope of protection of the present invention.

[0033] Please see Figure 1 , Figure 1 This is a flowchart of the real-time pointing error compensation method for laser communication terminals based on machine learning and orbital spatiotemporal characteristics, as shown in the figure. The workflow of this method can be divided into the following steps:

[0034] S1. The system determines whether the laser communication terminal has completed link establishment;

[0035] S2. After the terminal establishes the link, the system divides the terminal's working pointing space (azimuth and / or pitch angle) into several preset discrete angle partitions. The angle partitions are generally divided by selecting the rotation axis with a larger working range as the partition object, setting the motor zero position as the center of the angle partition (the pointing error at the motor zero position is the smallest), and dividing the space evenly with the preset number of partitions.

[0036] During the first orbital cycle in which a communication link is successfully established, when the terminal reaches any angular partition, the system acquires the actual pointing vector of the terminal in that partition (obtainable through inversion from precise tracking data) and compares it with the theoretical pointing vector of that partition to calculate the initial pointing error of that partition. The theoretical pointing vector for that partition is calculated based on the position vectors of the local satellite and the target satellite in the J2000.0 inertial coordinate system, the attitude matrix of the local satellite platform, and the theoretical installation matrix, specifically including:

[0037] S2.1) Obtain the position vector set of the local satellite and the target satellite in the J2000.0 inertial coordinate system;

[0038] S2.2) Calculate the pointing vector set of the target satellite relative to the local position based on the position vector set;

[0039] S2.3) Based on the attitude matrix of the local satellite platform, convert the position vector in the J2000.0 inertial coordinate system into the position vector in the satellite body coordinate system;

[0040] S2.4) Using the theoretical installation matrix, the position vector in the satellite body coordinate system is converted into the theoretical pointing vector in the laser communication terminal coordinate system.

[0041] The initial pointing error is used as the initial mounting angle deviation of the partition, forming an initial mounting angle deviation mapping table.

[0042] S3. Starting from the second orbital cycle, when the laser communication terminal returns to the angle partition that has been learned, the system reads the installation angle deviation of that partition stored in the previous orbital cycle from the installation angle deviation mapping table and injects it as a feedforward compensation amount into the terminal pointing control loop. The compensation method is usually to superimpose this deviation amount with the original installation angle parameter to generate a "corrected installation angle," which is used to calculate the theoretical value of the current pointing, thereby achieving pre-correction of the expected error.

[0043] S4. After completing the pre-calibration, the system continues to record the actual pointing information and the theoretical pointing angle, measures the residual pointing error after compensation, and updates the installation angle deviation of the corresponding angle partition based on the residual error. The system dynamically optimizes the installation angle deviation mapping table until the installation angle deviation of all commonly used working angle partitions of the terminal is iteratively updated, thereby realizing real-time compensation and long-term adaptive tracking of pointing error.

[0044] Please refer to the comparison of the effects with traditional pointing error correction methods. Figure 2 , Figure 2 This is a comparison chart of the correction results between a real-time compensation method for pointing error of a laser communication terminal based on machine learning and orbital spatiotemporal characteristics and traditional methods.

[0045] Please refer to the comparison of the effects with traditional pointing error correction methods. Figure 2 . Figure 2 The diagram shows a comparison of the correction results between the real-time pointing error compensation method for laser communication terminals based on machine learning and orbital spatiotemporal characteristics proposed in this invention and the traditional pointing error correction method.

[0046] This embodiment selects data collected by a laser communication terminal during a complete orbital cycle after successful link establishment as a sample to compare and analyze its pointing error correction effect. During this orbital cycle, the azimuth angle working range of the laser communication terminal is 208°~332°, and the elevation angle working range is 63°~69°.

[0047] When using traditional pointing error correction methods, a unified model is constructed for data across the entire angular range, and the least squares method is used to fit the installation angle error as a whole. The resulting installation angle corrections for the X, Y, and Z axes are 290 μrad, −1333 μrad, and 1857 μrad, respectively. After correction, the terminal pointing error is reduced from a maximum initial deviation of approximately 10 mrad to approximately 8 mrad. However, the correction effect is limited and cannot effectively compensate for nonlinear and time-varying errors generated during track operation.

[0048] In contrast, the method of the present invention segments the data according to the azimuth angle range, dividing the rotation axis (azimuth angle) with a larger working range into four intervals: 208°~240°, 240°~271°, 271°~302° and 302°~332°, and establishing corresponding pointing error correction models for each interval, resulting in the initial installation angle deviation mapping relationship shown in Table 1.

[0049] In contrast, the segmented correction method based on machine learning and orbital spatiotemporal characteristics employed in this invention can more effectively compensate for pointing errors, significantly reducing the maximum pointing deviation of the terminal to approximately 3 mrad. This method can better adapt to the dynamic error characteristics caused by orbital motion and changes in the space environment, significantly improving the pointing error compensation accuracy and system stability.

[0050] Table 1: Initial Installation Angle Deviation Mapping Table Obtained by Angle-Divided Region Correction

[0051]

Claims

1. A method for real-time compensation of pointing error in a laser communication terminal based on orbital spatiotemporal characteristics, characterized in that, The steps include the following: S1. Based on the on-orbit working field of view of the laser communication terminal, the pointing space of the laser communication terminal is divided into N preset discrete angle partitions; During the first orbital cycle in which a communication link is successfully established, when the laser communication terminal moves to any of the aforementioned angle partitions, it synchronously acquires the theoretical pointing vector and the actual pointing vector of that angle partition. The difference between the two is calculated as the initial installation angle deviation corresponding to the angle partition, and the initial installation angle deviation is associated with and stored with the corresponding angle partition identifier to form an initial installation angle deviation mapping table. S2. Starting from the second orbital cycle, when the laser communication terminal runs to a certain angle partition that has been learned again, the installation angle deviation currently stored in that angle partition is obtained as the feedforward compensation amount; The feedforward compensation amount is superimposed with the current theoretical pointing instruction to form a corrected pointing instruction, and the corrected pointing instruction is sent to the pointing execution mechanism. After the pre-calibration is completed, the residual pointing error after compensation is measured in real time, and the installation angle deviation of the corresponding angle zone is updated based on the residual pointing error. S3. Through iterative operation of multiple consecutive orbital cycles, the learning and compensation of all commonly used working angle partitions of the laser communication terminal are gradually completed, forming an installation angle deviation mapping relationship for real-time correction of pointing errors.

2. The real-time compensation method for pointing error of a laser communication terminal based on orbital spatiotemporal characteristics as described in claim 1, characterized in that, The pointing error includes slowly varying pointing errors caused by thermal deformation of the mounting surface, structural stress release, and changes in the thermal environment.

3. The real-time compensation method for pointing error of a laser communication terminal based on orbital spatiotemporal characteristics as described in claim 1, characterized in that, The angle partitioning is based on at least one of the attitude angle, azimuth angle, and pitch angle pointed to by the line of sight of the laser communication terminal during satellite orbit operation.

4. The real-time compensation method for pointing error of a laser communication terminal based on orbital spatiotemporal characteristics as described in claim 1, characterized in that, The feedforward compensation is superimposed on the original installation angle in the form of installation angle deviation to obtain the corrected installation angle, and the theoretical value of terminal pointing is calculated based on the corrected installation angle.

5. The real-time compensation method for pointing error of a laser communication terminal based on orbital spatiotemporal characteristics as described in claim 1, characterized in that, The installation angle deviation is updated using an iterative learning algorithm, which includes at least one of weighted averaging, adaptive filtering, or least squares algorithm.

6. The real-time compensation method for pointing error of a laser communication terminal based on orbital spatiotemporal characteristics as described in claim 1, characterized in that, The angle partitioning gradually covers all commonly used working fields of view of the laser communication terminal.

7. The real-time compensation method for pointing error of a laser communication terminal based on orbital spatiotemporal characteristics as described in claim 1, characterized in that, When the residual pointing error of a certain angle partition is less than a preset threshold, the update weight of the installation angle deviation of that angle partition is reduced.

8. A spaceborne laser communication terminal, comprising a control processing unit, a pointing actuator, and a memory, characterized in that, The control processing unit is configured to perform the laser communication terminal pointing error real-time compensation method as described in any one of claims 1 to 7.

9. The spaceborne laser communication terminal according to claim 8, characterized in that, The control processing unit is used to generate control signals based on theoretical pointing instructions and / or feedback signals; A pointing actuator is used to drive the optical components to move in response to the control signal; The pointing measurement unit is used to measure the actual pointing deviation between the terminal optical axis and the target line of sight and feed it back to the control processing unit.

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