Laser communication search, acquisition and tracking method and laser communication terminal

Abstract

This invention discloses a laser communication search, capture, and tracking method and a laser communication terminal. The laser communication search, capture, and tracking method includes: establishing a target-platform coupled dynamic model; predicting the target's trajectory within a preset future time period based on the target's ephemeris data and target motion model; generating a dynamic search path based on the target's trajectory within the preset future time period; calculating the spatiotemporal range of the laser beam covering the target based on the dynamic search path and the target's current position and velocity, and dynamically adjusting the capture threshold; estimating platform vibration disturbance in real time based on data collected by the inertial measurement unit on the platform and the platform disturbance model; optimizing the control commands generated by the controller in the laser communication terminal based on model predictive control and platform vibration disturbance; and inputting the optimized control commands into the terminal actuator model to drive the terminal actuator in the laser communication terminal to rotate, so that the laser beam is aligned with the target.

Description

Technical Field

[0001] This invention relates to the field of laser communication technology, and in particular to a laser communication search, capture and tracking method and a laser communication terminal. Background Technology

[0002] Laser communication boasts advantages such as high bandwidth, low power consumption, and resistance to electromagnetic interference, making it widely used in inter-satellite and satellite-to-ground communication. The PAT (Pointing, Acquisition, and Tracking) system is the core subsystem of a laser communication terminal, directly impacting the establishment and stability of the communication link.

[0003] Traditional PAT algorithms often employ a step-by-step control approach, which involves three steps: search scanning, coarse tracking, and fine tracking, to search for and track the target. This algorithm suffers from the following problems: 1. Low search efficiency: Traditional grid search or spiral search relies on preset paths and does not consider the characteristics of the target, resulting in long search time and high energy consumption.

[0004] 2. Poor robustness during the capture phase: Capture strategies based on fixed thresholds are easily affected by initial alignment errors, atmospheric turbulence, or platform vibrations, resulting in a high probability of false capture.

[0005] 3. Insufficient dynamic response during the tracking phase: Traditional control feedback (such as PID) relies on the current state and cannot predict future disturbances (such as target acceleration and platform jitter), resulting in tracking lag and cumulative beam offset, which makes it difficult to meet the requirements of high dynamic and high precision scenarios.

[0006] 4. Multi-interference coupling problem: In inter-satellite and satellite-to-ground scenarios, target motion (such as satellite orbital maneuvers), platform vibration (such as spacecraft attitude adjustment), atmospheric turbulence and other multi-source interference coupling make it difficult for traditional PAT algorithms to achieve multi-degree-of-freedom cooperative control.

[0007] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art. Summary of the Invention

[0008] The purpose of this invention is to provide a laser communication search, capture, and tracking method and a laser communication terminal, which can meet the requirements of search, capture, and tracking, with high control precision and small tracking error.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution: A laser communication search, capture, and tracking method is applied to a laser communication terminal, which is mounted on a platform; the laser communication search, capture, and tracking method includes: A target-platform coupled dynamics model is established; the target-platform coupled dynamics model includes: a target motion model, a platform disturbance model, and a terminal actuator model; Based on the target's ephemeris data and target motion model, predict the target's trajectory within a preset future time period; A dynamic search path is generated based on the target's movement trajectory within the preset future time period; Based on the dynamic search path and the target's current position and velocity, the spatiotemporal range of the laser beam covering the target is calculated and the capture threshold is dynamically adjusted. Based on the data collected by the inertial measurement unit on the platform and the platform disturbance model, the platform vibration disturbance is estimated in real time; The control commands generated by the controller in the laser communication terminal are optimized based on model predictive control and the vibration disturbance of the platform. The optimized control command is input to the terminal actuator model to drive the terminal actuator in the laser communication terminal to rotate, so that the laser beam is aligned with the target.

[0010] Optionally, the target motion model includes a satellite orbital dynamics model or a target relative motion model.

[0011] Optionally, the capture threshold includes spot center deviation and power intensity threshold.

[0012] Optionally, the inertial measurement unit includes an accelerometer and a gyroscope; The accelerometer collects the acceleration data of the platform; the gyroscope collects the angular velocity data of the platform.

[0013] Optionally, the steps for real-time estimation of platform vibration disturbances include: The acceleration and angular velocity data of the platform are fused using Kalman filtering, and the fused data is input into the platform disturbance model to estimate the platform vibration disturbance in real time.

[0014] Optionally, the platform disturbance model includes a spacecraft attitude vibration model.

[0015] Optionally, the terminal actuator includes a high-speed reflector and a two-dimensional turntable.

[0016] Optionally, the terminal actuator model includes the transfer function of the fast-reflecting mirror and the transfer function of the two-dimensional turntable.

[0017] On the other hand, the present invention also provides a laser communication terminal, including a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, it implements the method described above.

[0018] Compared with the prior art, the present invention has at least one of the following advantages: (1) The rolling optimization and disturbance compensation mechanism based on MPC in this invention can improve tracking accuracy and stabilize the error within ±5μrad.

[0019] (2) The MPC tracking control module with dynamic disturbance compensation of the present invention can realize feedforward-feedback coordinated control, effectively suppressing coupling interference such as platform disturbance and atmospheric turbulence, so as to reduce communication link interruption time.

[0020] (3) The multi-constraint optimization and probabilistic detection mechanism of the present invention can adapt to different degrees of alignment error, reduce the false capture rate to <1%, and enhance the capture robustness.

[0021] (4) The present invention provides an integrated laser communication pointing, searching, acquisition and tracking (PAT) algorithm based on model predictive control (MPC), which can be applied to various laser communication scenarios such as inter-satellite / satellite-ground and ground-based UAV, supports high-precision pointing of dynamic targets (such as low-orbit satellites) and has strong versatility. Attached Figure Description

[0022] Figure 1 This is a flowchart of a laser communication search, capture, and tracking method provided in an embodiment of the present invention.

[0023] Figure 2 A schematic diagram of the dynamic search path generated for the search phase.

[0024] Figure 3 A flowchart for determining the validity of a real objective.

[0025] Figure 4 This is a diagram of the MPC-based rolling optimization control framework of the present invention. Detailed Implementation

[0026] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a laser communication search, capture, and tracking method and a laser communication terminal proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of this invention. Please refer to the drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0027] Combined with appendix Figures 1-4 As shown, this embodiment provides a laser communication search, capture, and tracking method, which is applied to a laser communication terminal. The laser communication terminal is set on a platform; it can be understood that the platform is a spacecraft such as a satellite, spacecraft, or space probe.

[0028] The laser communication search, capture, and tracking method includes: Step S1: Establish a target-platform coupled dynamics model; the target-platform coupled dynamics model includes: target motion model, platform disturbance model and terminal actuator model.

[0029] Step S2: Predict the trajectory of the target within a preset time period based on the target's ephemeris data and target motion model; optionally, the target is a satellite, spacecraft, space probe, or space shuttle that needs to establish a communication link with the laser communication terminal.

[0030] Step S3: Generate a dynamic search path (non-fixed network / spiral path) based on the target's movement trajectory within the preset future time period.

[0031] Step S4: Calculate the spatiotemporal range (i.e., "capture window") of the laser beam covering the target based on the dynamic search path and the target's current position and velocity, and dynamically adjust the capture threshold; it is understood that the laser beam is generated and emitted by the laser in the laser communication terminal.

[0032] Step S5: Based on the data collected by the inertial measurement unit on the platform and the platform disturbance model, estimate the platform vibration disturbance in real time.

[0033] Step S6: Optimize the control commands generated by the controller in the laser communication terminal based on model predictive control and the platform vibration disturbance.

[0034] Step S7: Input the optimized control command into the terminal actuator model to drive the terminal actuator in the laser communication terminal to rotate, so that the laser beam is aligned with the target. Optionally, the terminal actuator includes a fast reflector and a two-dimensional turntable.

[0035] Specifically, in step S1, the target motion model includes a satellite orbital dynamics model or a target relative motion model. In one embodiment, the target motion model is a two-dimensional orbital dynamics model with J2 perturbation correction and an update period of 0.1s. This means that the target motion model can update the prediction result once every 0.1 seconds, that is, predict the target's motion trajectory once every 0.1 seconds.

[0036] Specifically, steps S2 and S3 belong to the search phase. In step S2, the ephemeris data of the target is input into the target motion model to obtain the target's motion trajectory within a preset time period in the future; optionally, the preset time period is 1 second.

[0037] In other embodiments, other orbital parameters of the target (such as orbital inclination, right ascension of the ascending node, argument of perigee, and mean perigee) or initial estimation information (such as the target's initial position, initial velocity, and initial attitude) can be used to obtain the target's trajectory within a preset time period based on the target motion model, but the present invention is not limited thereto.

[0038] In step S3, the dynamic search path is generated based on the target's movement trajectory within the preset future time period. This significantly reduces invalid search areas and narrows the search range, thereby shortening the search time by 30% to 50% and improving search efficiency. Specifically, as shown... Figure 2 As shown, when generating the dynamic search path based on the target's motion trajectory within the preset future time period, a spiral scanning trajectory generation method is used. That is, the dynamic search path is represented by designing a spiral scanning trajectory, so that the dynamic search path satisfies the minimization of search and the constraints on time.

[0039] In one embodiment, the platform is a low-Earth orbit satellite A, and the target is a low-Earth orbit satellite B, with an orbital inclination of 45° and a relative speed of 5 km / s. The trajectory of satellite B in the next 1 second is predicted based on its ephemeris data, wherein the ephemeris data sampling interval is set to 0.1 s, generating a dynamic search path.

[0040] Specifically, step S4 belongs to the acquisition phase; in step S4, the "acquisition window" of the laser beam covering the target (e.g., satellite B mentioned above) is predicted based on the dynamic search path, the current position and velocity of the target, and the acquisition threshold is dynamically adjusted to reduce the probability of false acquisition. Optionally, the acquisition threshold includes spot center deviation and power intensity threshold.

[0041] Understandably, during the capture phase, robust capture is achieved based on capture window prediction and a multi-hypothesis testing mechanism. The multi-hypothesis testing mechanism refers to confirming the validity of the target and whether it is a real target through multiple decision conditions. Specifically, multi-constraint optimization (i.e., using the dynamic search path, the target's current position, and velocity as constraints) and a probabilistic detection mechanism can adapt to different levels of alignment error, reducing the false capture rate to <1% and enhancing capture robustness.

[0042] Specifically, steps S5-S7 belong to the tracking phase; in step S5, the Inertial Measurement Unit (IMU) includes an accelerometer and a gyroscope; and the data collected by the accelerometer is the platform's acceleration data, while the data collected by the gyroscope is the platform's angular velocity data. More specifically, in step S5, the platform's acceleration and angular velocity data are fused using Kalman filtering, and the fused data is input into the platform disturbance model to estimate the platform's vibration disturbance in real time. Optionally, the platform disturbance model includes a spacecraft attitude vibration model, which describes the vibration generated by the spacecraft during attitude adjustment, but this invention is not limited thereto.

[0043] The expression for the platform vibration disturbance is: (1) in, Indicates time The corresponding platform vibration disturbance; This represents the acceleration data of the platform; This represents the angular velocity data of the platform; This indicates that the platform perturbation model at time [time missing] Perform disturbance estimation.

[0044] More specifically, in some embodiments, before performing step S6, the method further includes: detecting the light spot signal emitted by the target using a photodetector in the laser communication terminal; inputting the light spot signal emitted by the target, the platform vibration disturbance, and the light spot center position deviation in the acquisition threshold into a Bayesian estimation model (e.g., Figure 3As shown, to determine whether the target is a real target, that is, to estimate the validity of the real target; if the target is a real target, then continue to execute steps S6 to S7; if the target is not a real target, that is, the target is a distracting target, then do not continue to execute steps S6 to S7.

[0045] In step S6, the platform vibration disturbance can be used as input, and the control command for controlling the rotation of the terminal actuator can be optimized every 0.1 seconds using the Model Predictive Control (MPC). The optimized control command can suppress the laser beam pointing deviation caused by the platform vibration disturbance; that is, as... Figure 4 As shown, the platform disturbance model is incorporated into the objective function of the model predictive control (MPC), and optimized control commands are obtained through a rolling optimization solution method to control the terminal actuator. It can be understood that the MPC optimization objective function in the tracking phase includes: beam pointing error, actuator movement amplitude, and constraints including actuator saturation limits and general link availability. Furthermore, Figure 4 The state observation in the process involves obtaining the current observation vector of the laser communication terminal, i.e., its position and attitude angle in the inertial coordinate system.

[0046] It is understandable that the state of the laser communication terminal can be abstracted as follows: (2) in, This represents the rate of change of the state vector of the laser communication terminal over time; Represents the state transition function; This represents the state vector of the laser communication terminal, and , This indicates the position of the platform's center in the inertial coordinate system; This indicates the current attitude angle of the platform; Indicates control commands, and , , This represents the control quantity input to the two-dimensional turntable in the control command. , This indicates the control quantity input to the fast-reflecting mirror in the control command.

[0047] Finally, the state equation of the laser communication terminal is: (3) in, Indicates that the laser communication terminal is in the next moment. The state vector; This indicates that the laser communication terminal is at time... The state vector; Indicates time The corresponding control commands; , Represents the state transition matrix; Indicates time The corresponding platform vibration disturbance.

[0048] In other embodiments, the platform disturbance model further includes an atmospheric turbulence equivalent disturbance model to estimate atmospheric turbulence disturbances in real time. In step S6, the platform vibration disturbance and the atmospheric turbulence disturbance can be used as inputs, and the model predictive control can be used to optimize the control command for controlling the rotation of the terminal actuator. The optimized control command can suppress the laser beam pointing offset caused by the platform vibration disturbance and the atmospheric turbulence disturbance.

[0049] In step S7, the terminal actuator model includes the transfer function of the fast reflector (i.e., the response model of the fast reflector) and the transfer function of the two-dimensional turntable (i.e., the response model of the two-dimensional turntable).

[0050] As can be seen from the above, during the tracking phase, the MPC-based rolling optimization and disturbance compensation mechanism can improve tracking accuracy and stabilize the error within ±5μrad. Furthermore, by integrating multi-source disturbance observation with MPC rolling optimization, it is possible to achieve feedforward-feedback coordinated control, effectively suppressing coupled interference such as platform disturbances and atmospheric turbulence, thereby reducing communication link interruption time.

[0051] Based on the same inventive concept, this embodiment also provides a laser communication terminal, including a processor and a memory; the memory stores a computer program, and when the computer program is executed by the processor, it implements the method described above.

[0052] In summary, the laser communication search, capture, and tracking method and laser communication terminal provided in this embodiment overcome the shortcomings of traditional algorithms in terms of search efficiency, capture robustness, and tracking accuracy by integrating target motion models, multi-constraint optimization, and dynamic compensation mechanisms, achieving highly dynamic, high-precision, and robust laser communication pointing control. This embodiment can meet the requirements of search, capture, and tracking, with high control accuracy and small tracking error, achieving highly dynamic, high-precision, and robust laser communication pointing control.

[0053] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0054] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0055] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

[0056] The data collection, storage, and processing involved in this application strictly comply with current laws and regulations. Specifically, all user-related data to be processed in this solution originates from legal channels, and explicit authorization and consent from the data subjects have been obtained through user agreements or privacy policies during the data collection phase. For cases involving sensitive personal information, separate consent from the users has been further obtained, strictly adhering to the principle of informed consent. In the actual data processing process, if identity-identifying information is involved, this solution employs anonymization or de-identification techniques to ensure that the processed data cannot identify any specific natural person and cannot be restored. The data processing activities do not infringe upon personal privacy rights and comply with the provisions of the "Personal Information Protection Law of the People's Republic of China," the "Cybersecurity Law of the People's Republic of China," and other relevant laws. If this solution involves collecting information in public places, the purpose of collection is limited to maintaining public safety or specific scenarios with explicit user authorization, and does not exceed the necessary limits.

[0057] In summary, the technical solution claimed in this application ensures its legality, compliance, and ethics through technical means throughout the entire chain of data acquisition, data processing, and result output, and there is no situation that violates the law, social morality, or harms the public interest.

Claims

1. A laser communication search, capture, and tracking method, applied to a laser communication terminal, wherein the laser communication terminal is mounted on a platform; characterized in that, The laser communication search, capture, and tracking method includes: A target-platform coupled dynamics model is established; the target-platform coupled dynamics model includes: a target motion model, a platform disturbance model, and a terminal actuator model; Based on the target's ephemeris data and target motion model, predict the target's trajectory within a preset future time period; A dynamic search path is generated based on the target's movement trajectory within the preset future time period; Based on the dynamic search path and the target's current position and velocity, the spatiotemporal range of the laser beam covering the target is calculated and the capture threshold is dynamically adjusted. Based on the data collected by the inertial measurement unit on the platform and the platform disturbance model, the platform vibration disturbance is estimated in real time; The control commands generated by the controller in the laser communication terminal are optimized based on model predictive control and the vibration disturbance of the platform. The optimized control command is input to the terminal actuator model to drive the terminal actuator in the laser communication terminal to rotate, so that the laser beam is aligned with the target.

2. The laser communication search, capture, and tracking method as described in claim 1, characterized in that, The target motion model includes a satellite orbital dynamics model or a target relative motion model.

3. The laser communication search, capture, and tracking method as described in claim 1, characterized in that, The capture threshold includes spot center deviation and power intensity threshold.

4. The laser communication search, capture, and tracking method as described in claim 1, characterized in that, The inertial measurement unit includes an accelerometer and a gyroscope; The accelerometer collects the acceleration data of the platform; the gyroscope collects the angular velocity data of the platform.

5. The laser communication search, capture, and tracking method as described in claim 4, characterized in that, The steps for real-time estimation of platform vibration disturbances include: The acceleration and angular velocity data of the platform are fused using Kalman filtering, and the fused data is input into the platform disturbance model to estimate the platform vibration disturbance in real time.

6. The laser communication search, capture, and tracking method as described in claim 5, characterized in that, The platform disturbance model includes a spacecraft attitude vibration model.

7. The laser communication search, capture, and tracking method as described in claim 1, characterized in that, The terminal actuator includes a high-speed reflector and a two-dimensional turntable.

8. The laser communication search, capture, and tracking method as described in claim 7, characterized in that, The terminal actuator model includes the transfer function of the fast-reflecting mirror and the transfer function of the two-dimensional turntable.

9. A laser communication terminal, characterized in that, It includes a processor and a memory, wherein a computer program is stored in the memory, and when executed by the processor, the computer program implements the method as described in any one of claims 1 to 8.

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