Inter-satellite laser communication anti-disturbance second-level switching link establishment method and ground simulation system

Abstract

This invention belongs to the field of free-space laser communication technology, specifically disclosing a second-level anti-disturbance link establishment method and ground simulation system for inter-satellite laser communication. The method includes: using an inverse dynamics feedforward algorithm to compensate in real-time for the inertial coupling torque of the coarse tracking mechanism caused by satellite platform disturbances, achieving inertial spatial stability of the line of sight; employing a spectrum grading and saturation unloading strategy to further suppress line-of-sight jitter caused by satellite platform disturbances through the high-bandwidth operation of the fine tracking mechanism, and unloading low-frequency components to the coarse tracking mechanism to prevent saturation of the fine tracking mechanism; and initiating a high-frequency probabilistic spiral scan at the initial stage of link establishment to achieve rapid target acquisition. This invention solves the problem of lacking efficient anti-disturbance strategies and optimization strategies for second-level rapid response during mode switching from large-scale "blind search" to high-precision "lock-in" in inter-satellite laser link establishment.

Description

Technical Field

[0001] This invention belongs to the field of free-space laser communication technology, specifically relating to an inter-satellite laser communication anti-disturbance second-level switching link establishment method and ground simulation system. Background Technology

[0002] In free-space laser communication (FSOC), low Earth orbit (LEO) satellite networks offer advantages such as low latency, high bandwidth, and global coverage. However, the highly dynamic nature of their network topology necessitates frequent and rapid switching capabilities for inter-satellite laser links (ISLs). Existing link establishment mechanisms, however, are slow and ill-suited to highly dynamic network topologies. Traditional link establishment schemes typically rely on high-inertia mechanical turntables for helical or grating scanning, or on beacon light for long-cycle acquisition processes, with times generally ranging from tens of seconds to several minutes. This inefficient link establishment process incurs significant time overhead in frequently switching constellation networks, making it difficult to meet the networking requirements of second-level switching. Furthermore, various disturbance sources exist on the satellite platform during its on-orbit operation (such as flywheel vibration, moving part impact, and thermal flutter). These disturbances are directly coupled to the laser communication terminal through the satellite platform, easily causing line-of-sight jitter and leading to communication link interruptions.

[0003] In existing inter-satellite laser link establishment technologies, coarse tracking mechanisms possess large field-of-view scanning capabilities, but due to their large mechanical inertia and strong frictional nonlinearity, their servo bandwidth is typically limited to within a few hertz, making it impossible to suppress high-frequency jitter and leading to target loss during the initial link establishment phase. Fine tracking mechanisms offer high bandwidth but have extremely small travel (typically only a few milliradians). During the initial acquisition phase, if the satellite attitude error or orbit prediction error exceeds the field of view of the fine tracking system, the system will be unable to establish a link. Composite axis control technology is considered an effective way to solve these problems, but it is highly susceptible to dynamic coupling disturbances during the transition from large-angle rapid maneuvers to micro-radian level fine tracking. If the residuals of the coarse tracking mechanism are instantaneously introduced into the fine tracking loop, it can easily lead to saturation of the fine tracking mechanism, causing system divergence. Existing technologies lack efficient anti-disturbance strategies and optimization strategies for second-level rapid response when handling mode switching from large-scale "blind search" to high-precision "lock-in". Therefore, how to simultaneously solve the problems of rapid seek-through over a large angular range and disturbance suppression at the micro-radian level within a single system, and achieve seamless, second-level integration of the two, is a pressing technical challenge in the field of inter-satellite laser communication. Furthermore, traditional ground tests are often conducted on fixed platforms, which cannot simulate the microgravity dynamics of satellites in space, specifically the effect of the reaction torque caused by momentum conservation. The high-fidelity ground simulation system based on an air-bearing platform proposed in this invention can realistically reproduce this dynamic coupling phenomenon, and is a crucial step in verifying on-orbit performance. Summary of the Invention

[0004] The purpose of this invention is to address the lack of efficient anti-disturbance strategies and optimization strategies for second-level rapid response when switching modes from large-scale "blind search" to high-precision "lock-in" in inter-satellite laser link establishment. This invention proposes an anti-disturbance second-level switching link establishment method for inter-satellite laser communication and a ground simulation system.

[0005] The technical solution of the present invention is as follows: Firstly, an inter-satellite laser communication anti-interference second-level switching link establishment method, comprising the following steps: Coarse pointing and decoupling: The coarse tracking and aiming mechanism is driven to point to the target area based on satellite orbit and attitude information, and the inverse dynamics model is used to feedforward decoupling to compensate for the disturbance of the air-bearing satellite sub-platform, so as to establish an inertial space-stable line-of-sight reference. High-frequency scanning and acquisition: When the coarse pointing error converges to the preset range but no beacon light is detected, the fine tracking and aiming mechanism is driven to perform a high-frequency spiral scan on the line of sight reference. When the detector captures the beacon light, the high-frequency spiral scan is immediately interrupted and the spot position is locked. Dual-loop collaborative tracking: After successfully capturing the position of the light spot, the fine tracking mechanism is driven to perform high-bandwidth tracking based on the optical error of the beacon light to suppress high-frequency disturbances. An unloading command is generated to drive the coarse tracking mechanism to move in the direction of reducing the deflection angle of the fine tracking mechanism, so as to unload the zero position of the fine tracking mechanism, avoid saturation of the fine tracking mechanism, and realize anti-disturbance second-level switching and link establishment of inter-satellite laser communication.

[0006] As a preferred method, the feedforward decoupling compensation method for disturbances in the air-floating satellite sub-platform using the inverse dynamics model is as follows: The angular acceleration and angular velocity information of the air-floating satellite sub-platform are obtained through inertial sensors. Based on angular acceleration information, angular velocity information, and the moment of inertia of the coarse tracking and aiming mechanism, the dynamic coupling torque generated by the motion of the air-bearing satellite sub-platform on the coarse tracking and aiming mechanism is calculated in real time. A disturbance torque compensation value opposite to the dynamic coupling torque is generated and superimposed on the drive control loop of the coarse tracking and aiming mechanism to complete the decoupling compensation for the disturbance of the air-floating satellite sub-platform.

[0007] As a preferred option, the formula for expressing the dynamic coupling torque is:

[0008] in, Represents the dynamic coupling torque. This represents the angular acceleration of the air-bearing satellite sub-platform. This represents the angular velocity of the air-bearing satellite sub-platform. The unit direction vector representing the azimuth axis. The matrix of rotational inertia of the load, indicated by the superscript. This indicates transpose.

[0009] As a preferred option, the control law for the coarse aiming mechanism is:

[0010] in, This indicates the control torque output by the coarse-heel aiming mechanism motor. This indicates an optical error signal introduced by the coarse tracking mechanism detecting the beacon light. Indicates optical error signal rate of change, and These are the proportional and derivative coefficients of the feedback controller. It is the compensation value of the disturbance torque calculated in real time based on the inverse dynamics model. Represents the Coulomb friction torque. Coupled disturbance torque from outside the system, This represents the equivalent moment of inertia of the coarse-aligned sight. This represents the angular acceleration of the coarse aiming azimuth axis relative to the air-bearing satellite sub-platform. Indicates azimuth angular velocity, Indicates angular velocity, Indicates the viscous damping coefficient. This represents the stiffness coefficient.

[0011] Preferably, the high-frequency spiral scanning is a probability-driven Archimedean spiral scanning, and the trajectory equation of the probability-driven Archimedean spiral scanning is:

[0012] in, Indicates the polar radius. Indicates the polar angle. Indicates radial diffusion velocity. Indicates the scan frequency. Represents pi (π). Indicates time.

[0013] As a preferred embodiment, the method for generating unloading commands to drive the coarse tracking aiming mechanism to move in a direction that reduces the deflection angle of the fine tracking aiming mechanism is as follows: Monitor the real-time control position of the precision tracking mechanism; In response to the real-time control position deviating from the center zero position of the precision tracking mechanism, the offset of the real-time control position is low-pass filtered and integrated to obtain the unloading command; In response to the unloading command, the coarse tracking controller redirects the light spot back to the center of the field of view of the fine tracking mechanism, ensuring that the fine tracking mechanism always operates in the center area where its linearity is best and its stroke margin is largest, thus completing the zero-position unloading of the fine tracking mechanism. As a preferred option, the control law for the precision tracking and aiming mechanism is:

[0014] in, This indicates the real-time control position of the precision tracking and aiming mechanism. This indicates an optical error signal introduced by the coarse tracking mechanism detecting the beacon light. Indicates optical error signal The reciprocal, and This indicates the control parameters of the feedback controller for the precision tracking mechanism.

[0015] The beneficial effects of this invention are: This invention solves the problem of low efficiency in traditional scanning modes under disturbance conditions by using a coarse and fine dual-loop coordinated control method, enabling the tracking and aiming terminal to achieve visual axis stabilization from a large-scale blind search to a micro-radius level within seconds.

[0016] Secondly, a ground simulation system for verifying the second-level switching link establishment method for inter-satellite laser communication anti-disturbance includes an air-floating satellite simulation platform, a coarse-precision composite tracking terminal, a link-to-be-established terminal simulation device, and a main control and integrated processing unit; the main control and integrated processing unit is communicatively connected to the air-floating satellite simulation platform, the coarse-precision composite tracking terminal, and the link-to-be-established terminal simulation device; the coarse-precision composite tracking terminal is installed on the air-floating satellite simulation platform; An air-floating satellite simulation platform is used to simulate the microgravity, low-friction dynamic environment, and angular momentum conservation characteristics of satellites in orbit. A terminal simulation device to be built is used to generate optical signals that simulate the motion characteristics of a remote satellite. The main control and integrated processing unit is used for data interaction and real-time calculation to generate drive control commands. The coarse-precision composite tracking and aiming terminal includes a coarse tracking and aiming mechanism and a precision tracking and aiming mechanism, which are used to complete the second-level switching link establishment and stable pointing according to the drive control command.

[0017] Preferably, the coarse tracking mechanism uses a servo turntable as its actuator and a PSD sensor as its sensor; the fine tracking mechanism uses a voice coil fast swing mirror as its actuator and a CCD detector as its sensor.

[0018] As a preferred embodiment, the terminal simulation device to be established includes a perturbation fast-swing mirror and a parallel light emission subsystem. The deflected beam generated by the perturbation fast-swing mirror is angularly reduced by the parallel light emission subsystem, realizing a ground simulation system for inter-satellite laser communication with anti-disturbance second-level switching and link establishment in a near-field laboratory, simulating the small angular motion and jitter characteristics of far-field satellites.

[0019] The beneficial effects of this invention are: The ground simulation system proposed in this invention solves the problem that simple mathematical simulation cannot verify the dynamic coupling characteristics between optical payloads and satellite platforms, and provides a reference for ground-based experimental verification of laser terminals. Attached Figure Description

[0020] Figure 1 The diagram shows a flowchart of a second-level switching link establishment method for inter-satellite laser communication to resist disturbances.

[0021] Figure 2 The diagram shows the coarse-fine dual-loop cooperative control block diagram for realizing a second-level switching link establishment method for inter-satellite laser communication to resist disturbances.

[0022] Figure 3 The diagram shows the working principle of a ground simulation system used to verify the inter-satellite laser communication switching and link establishment performance.

[0023] Figure 4 The results of the coarse tracking and aiming terminal experiment are shown.

[0024] Figure 5 The diagram shows the change in the scanning angle of the two axes of the precision tracking and aiming mechanism.

[0025] Figure 6 The image shown is a two-dimensional scanning curve of the precision tracking and aiming mechanism.

[0026] Figure 7 The figure shows the curve of dynamic pointing error variation of inter-satellite lasers.

[0027] Figure 8 The figure shown is an experimental result of the stable pointing accuracy of the precision tracking and aiming terminal. Detailed Implementation

[0028] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the drawings are merely exemplary and are intended to illustrate the principles and spirit of the invention, and are not intended to limit the scope of the invention.

[0029] Example 1: like Figure 1 As shown, an inter-satellite laser communication anti-disturbance second-level switching link establishment method includes the following steps: S1. Coarse pointing and decoupling: Based on satellite orbit and attitude information, the coarse tracking and aiming mechanism is driven to point to the target area, and inverse dynamics feedforward decoupling is used to compensate for satellite platform disturbances in order to establish an inertial space stable line-of-sight reference. Specifically, based on reference information such as satellite ephemeris and attitude, the coarse tracking controller drives the coarse tracking mechanism to point towards the target area. At the same time, the angular acceleration information of the satellite platform is obtained through inertial sensors, the coupling interference torque of the satellite platform on the coarse tracking mechanism is calculated using the inverse dynamics model, and a feedforward compensation command is generated and superimposed on the coarse tracking drive to achieve the stabilization of the line of sight relative to inertial space under coarse tracking.

[0030] S2. High-frequency scanning and acquisition: When the coarse pointing error converges to the preset range but no beacon light is detected, the fine tracking and aiming mechanism is driven to perform a high-frequency spiral scan on the line of sight reference. When the detector captures the beacon light, the high-frequency spiral scan is immediately interrupted and the spot position is locked. Specifically, the detector is a CCD detector. When the CCD detector detects a signal light with a signal-to-noise ratio exceeding the threshold, it immediately interrupts the scanning and locks the position of the light spot.

[0031] S3. Dual-loop cooperative tracking: After successfully capturing the position of the light spot, the fine tracking mechanism is driven to perform high-bandwidth tracking based on the optical error of the beacon light to suppress high-frequency disturbances. An unloading command is generated to drive the coarse tracking mechanism to move in the direction of reducing the deflection angle of the fine tracking mechanism, so as to unload the zero position of the fine tracking mechanism, avoid saturation of the fine tracking mechanism, and realize anti-disturbance second-level switching and link establishment of inter-satellite laser communication.

[0032] Specifically, the coarse and fine dual-loop tracking modes enter a closed-loop tracking mode. On one hand, the fine tracking mechanism compensates for the pointing error of the coarse tracking mechanism based on the optical error signal of the beacon light. On the other hand, the fine tracking controller feeds back the DC component of the optical error signal to the coarse tracking controller after integration, driving the coarse tracking mechanism to move in the direction that reduces the deflection angle of the fine tracking mechanism, thereby achieving zero-position unloading of the fine tracking mechanism and preventing saturation of the fine tracking mechanism.

[0033] In this embodiment, as Figure 2 As shown, this invention constructs a feedforward decoupling system based on interference observation to achieve coarse pointing and decoupling. Let the angular velocity vector of the satellite platform relative to the inertial frame be... The rotational speed of the coarse aiming azimuth axis relative to the satellite is The rotational speed of the pitch axis relative to the azimuth axis is The absolute angular velocity of the line of sight of the coarse-tracking terminal in inertial space is then determined. Represented as:

[0034] in, This represents the rotation transformation matrix from the satellite's body coordinate system to its inertial coordinate system. This represents the rotation transformation matrix from the coarse aiming azimuth coordinate system to the satellite body coordinate system. This represents the rotation transformation matrix from the coarse following aiming elevation axis coordinate system to the coarse following aiming azimuth axis coordinate system. It is derived from the absolute angular velocity. As can be seen from the formula, the motion of the line of sight depends not only on the rotational speed ( , It also directly superimposed the angular velocity vector of the satellite platform relative to the inertial frame. In traditional control, the controller adjusts the speed solely based on encoder feedback. , ), ignored The influence of this causes the base disturbance to be directly transmitted to the tracking terminal, thus affecting the stability of the line of sight.

[0035] This invention utilizes the angular velocity vector measured by an inertial sensor. The required compensation velocity is calculated to achieve kinematic decoupling. The dynamic equation of the coarse following aiming azimuth axis is expressed as:

[0036] in, It is the equivalent moment of inertia of the coarse aiming azimuth axis. This refers to the electromagnetic torque output by the motor control. Frictional torque, mainly including Coulomb friction and viscous friction, is expressed as:

[0037] in, Let be the Coulomb coefficient of friction. It is the coefficient of viscous friction. It is a symbolic function.

[0038] The embodiments of the present invention take into account dynamic coupling torque. When the satellite platform has angular acceleration At that time, due to inertia, a reverse torque will be applied to the coarse aiming azimuth axis, resulting in a dynamic coupling torque. The formula is:

[0039] in, The unit direction vector representing the azimuth axis. It is the moment of inertia matrix of the load, with superscript... This indicates transpose.

[0040] When the PSD sensor detects beacon light, it introduces an optical error signal. and the derivative of the optical error signal At that time, the control law design of the coarse aiming mechanism is as follows:

[0041] in, and These are the control parameters of the feedback controller for the coarse aiming mechanism. It is the compensation value of the disturbance torque calculated in real time based on the inverse dynamics model.

[0042] In this embodiment, the present invention achieves the coordinated operation of coarse and fine tracking mechanisms based on a spectrum hierarchical strategy. High-frequency disturbances are suppressed by the high-bandwidth, fast-response fine tracking mechanism. Low-frequency and large-angle disturbances are handled by the coarse tracking mechanism. To address the saturation issue of the fine tracking mechanism, an unloading loop is designed, and the controller monitors the real-time control position of the fine tracking mechanism. If the precision tracking mechanism deviates from its center zero position, the deviation is passed through a low-pass filter and a correction command is generated and sent to the coarse tracking mechanism. The coarse tracking mechanism then redirects the spot to the center of the field of view of the precision tracking mechanism, so that the precision tracking mechanism always works in the center area where its linearity is best and its travel margin is largest.

[0043] The control law design of the precision tracking and aiming mechanism is as follows:

[0044] in, and These are the control parameters of the feedback controller for the precision tracking mechanism.

[0045] In addition, the embodiments of the present invention also include a watchdog program in the control software. If the link establishment is not completed within a specified time (20s), the system will automatically reset to the initial search state and re-establish the laser link, preventing the voice coil motor from overheating or even the system from being damaged due to long-term large-scale scanning.

[0046] In this embodiment, the present invention designs a probability-driven Archimedean spiral scan for high-frequency scanning and acquisition. The trajectory equation of the Archimedean spiral scan is as follows:

[0047] in, It is the radial diffusion velocity. This refers to the scanning frequency. In this embodiment of the invention, the scanning frequency is set to 50Hz to achieve high-frequency, rapid scanning, and the scanning interval is set to the beam divergence angle. to To ensure coverage without blind spots, the probabilistic acquisition algorithm incorporates interrupt-lock logic. Once the beacon light energy detected by the PSD sensor exceeds a preset threshold, an "interruption" is immediately triggered, forcibly switching from scanning mode to closed-loop tracking mode. A compensation control algorithm then rapidly pulls the light spot into the center of the CCD's field of view. This event-triggered mode switching eliminates the waiting time required to complete the entire scanning cycle, facilitating rapid scanning and link establishment.

[0048] Example 2: Based on Example 1, this embodiment of the invention provides a ground simulation system for verifying the second-level switching link establishment method for inter-satellite laser communication to resist disturbances, such as... Figure 3As shown, it includes an air-floating satellite simulation platform, a coarse-precision composite tracking and aiming terminal, a terminal simulation device for establishing a link, and a main control and integrated processing unit; the main control and integrated processing unit is communicatively connected to the air-floating satellite simulation platform, the coarse-precision composite tracking and aiming terminal, and the terminal simulation device for establishing a link; the coarse-precision composite tracking and aiming terminal is installed on the air-floating satellite simulation platform; The air-bearing satellite simulation platform is equipped with air bearings at the bottom to simulate the microgravity, low-friction dynamic environment and angular momentum conservation characteristics of satellites in orbit; attitude stability of the satellite platform is achieved through sensors and reaction flywheels. A terminal simulation device to be built is used to generate optical signals that simulate the motion characteristics of a remote satellite. The main control and integrated processing unit is used for data interaction and real-time calculation to generate drive control commands. The coarse-precision composite tracking and aiming terminal includes a coarse tracking and aiming mechanism and an embedded precision tracking and aiming mechanism, which are used to complete the second-level switching link establishment and stable pointing according to the drive control command.

[0049] In this embodiment, the coarse tracking mechanism is an actuator of a servo turntable and a PSD sensor; the fine tracking mechanism is an actuator of a voice coil fast swing mirror and a CCD detector.

[0050] In this embodiment, the terminal simulation device to be built includes a perturbation fast-swing mirror and a parallel light emission subsystem. The deflected beam generated by the perturbation fast-swing mirror is angularly reduced by the parallel light emission subsystem to simulate the small angular motion and jitter characteristics of far-field satellites in a near-field laboratory.

[0051] This invention proposes a high-fidelity ground simulation system that uses a single-axis air-bearing bearing to support the satellite simulation platform, overcoming gravity and friction during ground testing and avoiding the dynamic coupling effect of the cover. This allows for a realistic simulation of the "undamped" rotational environment in space, thereby verifying the effectiveness of inverse dynamics feedforward decoupling. The invention also designs a terminal simulation device for the chain to be built, which generates beam jitter by perturbing a fast-swinging mirror, thus simulating more realistic line-of-sight jitter in space. The perturbed beam passes through a parallel light emission system, reducing the beam aperture. The divergence angle increases by a factor of two. This allows for the simulation of inter-satellite links thousands of kilometers away within a limited laboratory space, significantly reducing testing costs and increasing the credibility of verification.

[0052] Furthermore, to verify the proposed inter-satellite laser communication anti-disturbance second-level switching link establishment method and ground simulation system, ground experiments were conducted. The results of the coarse tracking and aiming terminal experiments are as follows: Figure 4As shown. After the coarse tracking terminal control is activated, the two-axis servo motors drive the pointing to the desired command, and the coarse tracking angle error converges after 2.5 seconds. After stable control, the pointing deviations of the X-axis and Y-axis are 0.04° (3σ) and 0.18° (3σ), respectively.

[0053] After the coarse tracking and aiming terminal stabilizes, the fine tracking and aiming terminal automatically scans the uncertain area of ​​the target. The scanning curve is selected as an Archimedean spiral, the scanning frequency is 50Hz, and the changes in the scanning angles of the two axes are as follows: Figure 5 As shown, the two-dimensional scanning curve is as follows Figure 6 As shown, when the signal light spot appears within the field of view of the CCD photodetector at 2.87s, the fine tracking scan is considered successful, and the process switches to the fine tracking acquisition stage.

[0054] During the precision tracking and acquisition phase, when the signal light spot is centered in the field of view of the CCD photodetector and the pointing error (root mean square of the two-axis error) converges to within 20 μrad, the precision tracking terminal successfully switches and establishes a link. Figure 7 As shown, the entire process of rapid switching and link establishment takes 8.26 seconds.

[0055] The system continues to operate after a successful switchover and link establishment. Precise tracking and aiming of the signal beam spot are achieved; the experimental results of precise pointing control via inter-satellite laser communication are as follows: Figure 8 As shown. Under stable tracking and aiming conditions, the tracking and aiming errors of the two axes within 3 seconds are 8.9 μrad (3σ) and 3.5 μrad (3σ).

[0056] In summary, this invention proposes and verifies a second-level link establishment method and simulation system for inter-satellite laser communication based on coarse and fine dual-loop coordinated control. A back-dynamic feedforward algorithm based on base angular velocity feedforward is proposed, characterized by using a back-dynamic model to calculate and compensate for the coupling torque of the base on the coarse tracking mechanism in real time. A spectrum grading and saturation unloading strategy is adopted: the coarse tracking mechanism handles low-to-medium frequency large-amplitude maneuvers, while the fine tracking mechanism loop handles high-frequency micro-vibrations. The fine tracking mechanism unloads the DC component to the coarse tracking loop to prevent saturation. High-frequency probabilistic spiral scanning is initiated in the initial link establishment phase to achieve second-level target acquisition, ultimately achieving rapid and high-precision pointing. Tests based on a high-fidelity ground simulation system show that the link establishment time is 8.26 seconds, and the two-axis tracking errors are 8.9 μrad and 3.5 μrad, respectively, fully demonstrating the engineering practical value of this scheme and its application scenarios such as the construction of future large-scale integrated space-ground information networks.

[0057] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for inter-satellite laser communication with second-level anti-disturbance switching and link establishment, characterized in that, Includes the following steps: Coarse pointing and decoupling: The coarse tracking and aiming mechanism is driven to point to the target area based on satellite orbit and attitude information, and the inverse dynamics model is used to feedforward decoupling to compensate for the disturbance of the air-bearing satellite sub-platform, so as to establish an inertial space-stable line-of-sight reference. High-frequency scanning and acquisition: When the coarse pointing error converges to the preset range but no beacon light is detected, the fine tracking and aiming mechanism is driven to perform a high-frequency spiral scan on the line of sight reference. When the detector captures the beacon light, the high-frequency spiral scan is immediately interrupted and the spot position is locked. Dual-loop collaborative tracking: After successfully capturing the position of the light spot, the fine tracking mechanism is driven to perform high-bandwidth tracking based on the optical error of the beacon light to suppress high-frequency disturbances. An unloading command is generated to drive the coarse tracking mechanism to move in the direction of reducing the deflection angle of the fine tracking mechanism, so as to unload the zero position of the fine tracking mechanism, avoid saturation of the fine tracking mechanism, and realize anti-disturbance second-level switching and link establishment of inter-satellite laser communication.

2. The inter-satellite laser communication anti-disturbance second-level switching link establishment method according to claim 1, characterized in that, The specific method for using inverse dynamics model feedforward decoupling to compensate for disturbances in air-floating satellite sub-platforms is as follows: The angular acceleration and angular velocity information of the air-floating satellite sub-platform are obtained through inertial sensors. Based on angular acceleration information, angular velocity information, and the moment of inertia of the coarse tracking and aiming mechanism, the dynamic coupling torque generated by the motion of the air-bearing satellite sub-platform on the coarse tracking and aiming mechanism is calculated in real time. A disturbance torque compensation value opposite to the dynamic coupling torque is generated and superimposed on the drive control loop of the coarse tracking and aiming mechanism to complete the decoupling compensation for the disturbance of the air-floating satellite sub-platform.

3. The inter-satellite laser communication anti-disturbance second-level switching link establishment method according to claim 2, characterized in that, The formula for the dynamic coupling torque is: in, Represents the dynamic coupling torque. This represents the angular acceleration of the air-bearing satellite sub-platform. This represents the angular velocity of the air-bearing satellite sub-platform. The unit direction vector representing the azimuth axis. The matrix of rotational inertia of the load, with superscript This indicates transpose.

4. The inter-satellite laser communication anti-disturbance second-level switching link establishment method according to claim 3, characterized in that, The control law for the coarse aiming mechanism is: in, This indicates the control torque output by the coarse-heel aiming mechanism motor. This indicates an optical error signal introduced by the coarse tracking mechanism detecting the beacon light. Indicates optical error signal rate of change, and These are the proportional and derivative coefficients of the feedback controller. It is the compensation value of the disturbance torque calculated in real time based on the inverse dynamics model. Represents the Coulomb friction torque. Coupled disturbance torque from outside the system, This represents the equivalent moment of inertia of the coarse-aligned sight. This represents the angular acceleration of the coarse aiming azimuth axis relative to the air-bearing satellite sub-platform. Indicates azimuth angular velocity, Indicates angular velocity. Indicates the viscous damping coefficient. This represents the stiffness coefficient.

5. The inter-satellite laser communication anti-disturbance second-level switching link establishment method according to claim 1, characterized in that, The high-frequency spiral scan is a probability-driven Archimedean spiral scan, and the trajectory equation of the probability-driven Archimedean spiral scan is: in, Indicates the polar radius. Indicates the polar angle. Indicates radial diffusion velocity. Indicates the scan frequency. Represents pi (π). Indicates time.

6. The inter-satellite laser communication anti-disturbance second-level switching link establishment method according to claim 1, characterized in that, The specific method for generating unloading commands to drive the coarse aiming mechanism to move in the direction that reduces the deflection angle of the fine aiming mechanism is as follows: Monitor the real-time control position of the precision tracking mechanism; In response to the real-time control position deviating from the center zero position of the precision tracking mechanism, the offset of the real-time control position is low-pass filtered and integrated to obtain the unloading command; In response to the unloading command, the coarse tracking controller redirects the light spot back to the center of the field of view of the fine tracking mechanism, ensuring that the fine tracking mechanism always operates in the center area where its linearity is best and its stroke margin is largest, thus completing the zero-position unloading of the fine tracking mechanism.

7. The inter-satellite laser communication anti-disturbance second-level switching link establishment method according to claim 1, characterized in that, The control law of the precision tracking and aiming mechanism is: in, This indicates the real-time control position of the precision tracking and aiming mechanism. This indicates an optical error signal introduced by the coarse tracking mechanism detecting the beacon light. Indicates optical error signal The reciprocal, and This indicates the control parameters of the feedback controller for the precision tracking mechanism.

8. A ground simulation system for verifying the second-level anti-disturbance switching link establishment method for inter-satellite laser communication as described in any one of claims 1-7, characterized in that, It includes an air-floating satellite simulation platform, a coarse-precision composite tracking and aiming terminal, a terminal simulation device for the link to be established, and a main control and integrated processing unit; The main control and integrated processing unit is communicatively connected to the air-floating satellite simulation platform, the coarse and fine composite tracking and aiming terminal, and the terminal simulation device to be established; the coarse and fine composite tracking and aiming terminal is installed on the air-floating satellite simulation platform. An air-floating satellite simulation platform is used to simulate the microgravity, low-friction dynamic environment, and angular momentum conservation characteristics of satellites in orbit. A terminal simulation device to be built is used to generate optical signals that simulate the motion characteristics of a remote satellite. The main control and integrated processing unit is used for data interaction and real-time calculation to generate drive control commands. The coarse-precision composite tracking and aiming terminal includes a coarse tracking and aiming mechanism and a precision tracking and aiming mechanism, which are used to complete the second-level switching link establishment and stable pointing according to the drive control command.

9. The ground simulation system according to claim 8, characterized in that, The coarse tracking mechanism is driven by a servo turntable and its sensor is a PSD sensor; the fine tracking mechanism is driven by a voice coil fast swing mirror and its sensor is a CCD detector.

10. The ground simulation system according to claim 8, characterized in that, The simulation device for the terminal to be built includes a perturbation fast-swing mirror and a parallel light emission subsystem. The deflected beam generated by the perturbation fast-swing mirror is angularly reduced by the parallel light emission subsystem, thereby simulating the minute angular motion and jitter characteristics of far-field satellites in the near-field laboratory.

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