A motion-coupled spaceborne laser communication terminal fixed-time disturbance control method

Abstract

The present application relates to a kind of motion coupling under spaceborne laser communication terminal fixed time disturbance control method, for the periscope type laser communication terminal fast pointing control problem under the influence of multi-source disturbance such as space environment interference, floating satellite platform coupling moment and rotation shaft friction moment, first, the deep coupling model of spaceborne communication terminal containing above-mentioned multi-source disturbance is established, and multi-source disturbance is regarded as total disturbance moment by analyzing interference structure and characteristics;Second, fixed time disturbance observer is designed to quickly estimate the total disturbance moment suffered by communication terminal;Third, nominal fixed time controller is designed and combined with disturbance observer to form fixed time compound anti-interference controller;Finally, combined with the pointing time demand of communication terminal, observer and controller parameter selection are analyzed and guided, and fixed time anti-interference control of spaceborne laser communication terminal under motion coupling is completed.The control method of the present application has the characteristics of strong robustness, fast pointing speed and guaranteeing pointing error fixed time convergence.

Description

Technical Field

[0001] This invention belongs to the field of servo system control, specifically relating to a fixed-time anti-disturbance control method for a spaceborne laser communication terminal under motion coupling, which solves the problem of fixed-time anti-disturbance control for a periscope-type laser communication terminal under the influence of multiple sources of interference, including space environment interference, coupling torque of floating satellite platform, and friction torque of rotating shaft. Background Technology

[0002] With the rapid development and deployment of constellation communication projects, highly secure and reliable inter-satellite laser communication technology has become an important development direction, creating an urgent need for the rapid construction of inter-satellite laser links. Domestic and international aerospace agencies have already conducted research on key laser communication technologies and on-orbit experiments, facing challenges in various aspects such as communication link establishment speed and link stability during practice. The pointing and tracking system control technology for inter-satellite laser communication is a core key technology for achieving stable and continuous communication, requiring communication terminals to possess high-precision, high-stability, and rapid pointing and tracking control capabilities. The laser communication terminal pointing control system is a typical strongly coupled, multi-interference, and high-performance control system. For example, the pointing maneuver of the communication terminal is coupled with the satellite's attitude motion; in a microgravity environment, the coupling torque directly affects the pointing accuracy of the communication terminal. The communication terminal is also affected by complex and difficult-to-describe multi-source disturbances, such as space environment interference and friction from various joint movements. Furthermore, to meet the communication requirements within the limited time window of laser communication, the communication terminal needs to point at the target satellite with specific accuracy within a limited time. The complex interference characteristics and stringent control performance requirements greatly increase the difficulty of designing and analyzing the laser communication terminal pointing control system, making traditional terminal pointing control methods difficult to apply directly. Therefore, it is crucial to design a fixed-time anti-disturbance control method for spaceborne laser communication terminals under motion coupling, based on existing technologies, and this method has broad application prospects.

[0003] Currently, research on anti-disturbance control for laser communication terminals mainly focuses on single-disturbance scenarios, with limited research considering anti-disturbance control techniques for communication terminals under conditions of multiple-source disturbances and time constraints. The literature "Composite Control Strategy for Satellite Laser Communication Coarse Tracking System" considers a terminal pointing system directly driven by a permanent magnet synchronous motor. Based on the traditional PID control strategy, it proposes a feedforward composite control strategy, improving the system's dynamic characteristics and reducing tracking errors. This method emphasizes the dynamics of the driving servo but does not fully consider the influence of the pointing mechanism's coupling torque and satellite attitude motion, making it difficult to achieve ideal control performance under complex disturbance environments. Chinese patent application CN201911056675.7 proposes a working mode recognition and position control system for the coarse pointing mechanism of a laser terminal. Addressing the shortcomings of traditional PID control methods in simultaneously achieving fast dynamic response and no overshoot in step response, it designs a working mode recognition strategy and corresponding position loop control parameters for different working modes, improving system tracking performance. However, this method does not fully consider anti-disturbance control issues. Chinese patent application CN202110566714.9 proposes a coarse pointing position control method for a laser terminal based on an ultrasonic motor. By setting a preset threshold for the pointing error angle, a joint position loop-velocity loop control is used when the error exceeds the threshold, and only the position loop control is used when the error is less than the threshold, ensuring the system's control performance at extremely low speeds. However, this method neglects the nonlinear coupling terms in the communication terminal. The paper "Satellite Inter-Satellite Laser Communication Coarse Tracking Turntable Control System" establishes a three-loop control model for a terminal coarse tracking system driven by a permanent magnet synchronous motor. Based on PI control, an adaptive gain control is proposed, improving the system's control accuracy. This method focuses on the dynamics of the terminal servo system and ignores the influence of satellite attitude motion. The paper "Research on Optoelectronic Platform Line-of-Sight Stabilization Technology Based on Active Disturbance Rejection Control" addresses the control problem of an optoelectronic servo platform under disturbances. Utilizing the concept of disturbance summation, an active disturbance rejection controller based on a reduced-order extended state observer is designed. Combined with a Kalman filter to process system measurement noise, this improves the system's line-of-sight stability and robustness. However, this method does not fully consider the quantification of the system response time index during its design.

[0004] In summary, under the influence of multiple sources of interference such as space environment interference, coupling torque of floating satellite platform and rotation shaft friction torque, there is a lack of rapid pointing control methods for periscope-type laser communication terminals. It is urgent to overcome the problem of anti-interference fixed-time pointing control methods for laser communication terminals based on anti-interference technology. Summary of the Invention

[0005] To address the problem of fixed-time anti-interference control for periscope-type laser communication terminals under the influence of multi-source interference from space environment interference, floating satellite platform coupling torque, and shaft friction torque, and to overcome the shortcomings of existing technologies, this invention provides a fixed-time anti-interference control method for spaceborne laser communication terminals under motion coupling. This method enables rapid estimation and compensation of complex multi-source interference, utilizes interference estimation compensation, feedback suppression, and fixed-time control techniques, and ensures the pointing time constraint of the communication terminal, thereby improving the speed, accuracy, and anti-interference capability of the pointing control process of the communication terminal.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A fixed-time anti-disturbance control method for a spaceborne laser communication terminal under motion coupling includes the following steps:

[0008] The first step is to establish a model of a deep-coupled spaceborne periscope laser communication terminal under the influence of multiple sources of interference, including space environment interference, coupling torque of floating satellite platform, and rotational friction torque. The coupling torque of floating satellite platform on terminal is calculated by Newton-Euler recursion, and environmental interference and rotational friction are regarded as norm-bounded total disturbances.

[0009] The second step involves designing a fixed-time interference observer to quickly estimate external environmental interference, satellite motion coupling torque, and shaft friction based on the deep-coupled spaceborne periscope laser communication terminal model established in the first step, thereby obtaining the total disturbance estimate within a fixed time period.

[0010] The third step is to design a nominal fixed-time controller, using the interference observer and the total disturbance estimate from the second step to form a fixed-time composite disturbance rejection controller to suppress interference compensation error.

[0011] The fourth step involves analyzing and guiding the selection of observer and controller parameters based on the pointing time requirements of the communication terminal, thereby completing the fixed-time anti-disturbance control of the spaceborne laser communication terminal under motion coupling.

[0012] Furthermore, the first step includes:

[0013] (1) Establish a model of a deeply coupled spaceborne periscope laser communication terminal under the influence of multiple sources of interference, including space environment interference, floating satellite platform coupling torque, and shaft friction torque:

[0014]

[0015] in, Let Z be the moment of inertia of the first periscope-type communication terminal connecting rod at the center of mass along the Z-axis. and These correspond to the rotational inertia of the second periscope-type communication terminal linkage at its center of mass along the X, Y, and Z axes, respectively; θ1 and θ2 are the rotation angles of the first terminal joint and the second terminal joint, respectively. and These are the angular velocities of the first and second terminal joints, respectively. and τ1 and τ2 are the angular accelerations of the first and second terminal joints, respectively; L2 is the link length of the second terminal joint; m2 is the mass of the second terminal joint; τ1 and τ2 are the control torques of the first and second terminal joints, respectively. and These are the coupling torques of the first and second terminal joints, respectively; f S1 and f S2 These are the entrainment and coupling torques caused by the satellite's attitude motion on the first and second terminal joints, respectively. and The disturbance torque of environmental interference and shaft friction on the first and second terminal joints;

[0016] (2) To further describe the influence of the floating satellite platform on the periscope terminal's entrainment coupling moment, the entrainment coupling moment was obtained through Newton-Euler recursive calculation:

[0017]

[0018] Among them, and These correspond to the X-axis and Y-axis rotational inertia of the first periscope-type communication terminal linkage at its center of mass, respectively; ω x ω y and ω z These are the attitude angular velocities of the satellite along the X, Y, and Z axes, respectively. and L1 represents the angular acceleration of the satellite along the X, Y, and Z axes, respectively; L2 represents the link length of the first terminal joint; L3 represents the link length of the second terminal joint; m1 represents the mass of the first terminal joint; m2 represents the mass of the second terminal joint; A1 and B1 are auxiliary variables.

[0019] (3) The dynamic model of the periscope-type communication terminal is transformed into an integral cascade type through state transformation, and x1 = [θ1θ2] is defined. T , in[·] T The transpose of · yields the transformed model:

[0020]

[0021] in, diag{·} denotes a diagonal matrix; and Let x1 and x2 be the first derivatives; τ = [τ1 τ2] T Input torque to the two joints of the communication terminal; The coupling torque between the two joints of the communication terminal; The coupling torque between the satellite's attitude motion and the two joints of the communication terminal; This refers to the environmental interference and shaft friction torque experienced by the two joints of the communication terminal.

[0022] Furthermore, in the second step, the total disturbance is obtained within a fixed time period. The estimated value is:

[0023]

[0024] Where z1 and z2 are the observer states, and their first derivatives are respectively Specifically, z1 is the estimated value of the angular velocity x2 of the communication terminal joint; z2 is the estimated value of the total disturbance D experienced by the communication terminal joint; K1 = diag{k1,k2} and K2 = diag{k3 / η,k4 / η} are the observer parameter matrices, where k1, k2, k3, k4 and η are the observer parameters to be selected, satisfying k1 > 0, k2 > 0, k3 > 0, k4 > 0, ... and 0 < η < 1; the auxiliary functions Φ1(·) and Φ2(·) are expressed as:

[0025]

[0026]

[0027] Where a is any n-dimensional vector, a i Let represent the i-th row of vector a; α1 and β1 are the observer parameters to be selected, which must satisfy 0.5 < α1 < 1 and 1 < β1 < 1.5; |·| represents the absolute value of ·; sgn(·) is the sign function; φ1(·) and φ2(·) represent intermediate variables, specifically expressed as

[0028] Furthermore, the third step includes:

[0029] Take the expected pointing angle x of the communication terminal d Desired pointing angular velocity With desired pointing angle acceleration Define the angle tracking error ε1 = x1 - x d Angular velocity tracking error The controller is designed to be in the following form:

[0030]

[0031]

[0032] Among them, s i Represents the i-th row element of the sliding surface s; and These represent the i-th row elements of the tracking errors ε1 and ε2, respectively; This represents the element in the i-th row of the state variable z2 of the disturbance observer; Represents a nonlinear diagonal matrix f x The element in the i-th row and i-th column; Represents the desired pointing angular acceleration The elements in the i-th row; k5, k6, k7, α2, λ1, and μ1 are controller parameters, satisfying k5 > 0, k6 > 0, k7 > 0, α2 > 1, λ1 > 0, and μ1 > 0; ln(·) is the natural logarithm function; the final controller output torque is τ = [τ1τ2]. T .

[0033] Furthermore, in the fourth step, based on the pointing time requirements of the communication terminal, the parameters of the observer and controller are analyzed and selected to complete the fixed-time anti-disturbance control of the spaceborne laser communication terminal under motion coupling:

[0034] (1) When the lumped interference derivative of the two joints of the communication terminal has an upper bound σ1, that is, it satisfies express The derivative, express The derivative; there exists a positive constant E when the observer parameter η is sufficiently small, such that the interference observer's error in estimating D occurs within time t ≥ T. dmax It then converges to ||D-z²|| < E in the neighborhood of E, where ||·|| denotes the norm of ·. The convergence time T dmax satisfy:

[0035]

[0036] Where c is a positive constant; when the interference observer parameters satisfy k1>0, k2>0, k3>0, k4>0, Under the premise of 0 < η < 1, the convergence time can be adjusted by adjusting the observer parameters 0.5 < α1 < 1 and 1 < β1 < 1.5;

[0037] (2) After the interference observer estimation error converges to ||D-z2||<E, the communication terminal expects the pointing angle error to be within time t>T. dmax +T Cmax After convergence to near zero, where T Cmax satisfy:

[0038]

[0039] in, e represents the natural constant; the controller parameter k6 must satisfy k6 > E; under the premise of satisfying k5 > 0, k6 > 0, k7 > 0, α2 > 1, λ1 > 0 and μ1 > 0, the convergence time can be shortened by appropriately increasing the controller parameters k5, k6 and k7, or by increasing α2 and λ1 or decreasing μ1.

[0040] The advantages of this invention compared to the prior art are as follows:

[0041] This invention relates to a fixed-time anti-interference controller for a spaceborne laser communication terminal under motion coupling. Addressing the shortcomings of existing methods in lacking fixed-time anti-interference control capabilities for laser communication terminals under multi-source interference from space environment disturbances, floating satellite platform coupling torque, and shaft friction torque, this invention designs a fixed-time interference observer to estimate the total disturbance of complex interference and nonlinear components. Combined with a fixed-time controller, this achieves a robust anti-interference controller for the laser communication terminal, enabling it to maintain ideal control performance under multi-source interference and ensuring that the control error converges within a fixed time. Finally, considering the pointing time requirements of the communication terminal, the invention analyzes and guides the selection of observer and controller parameters. This invention's control method features strong robustness and high pointing speed, making it suitable for pointing systems of communication terminals with multi-source interference and rapid pointing requirements. Attached Figure Description

[0042] Figure 1 This is a flowchart of a fixed-time anti-interference control method for a spaceborne laser communication terminal under motion coupling according to the present invention.

[0043] Figure 2 This is a control block diagram of a fixed-time anti-disturbance control method for a spaceborne laser communication terminal under motion coupling according to the present invention. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0045] like Figure 1 As shown, the fixed-time anti-interference control method for a laser communication terminal under satellite motion coupling according to the present invention includes the following steps:

[0046] The first step is to establish a model of a deeply coupled spaceborne periscope-type laser communication terminal under the influence of multiple sources of interference, including space environment interference, coupling torque of the floating satellite platform, and rotational friction torque. The coupling torque of the floating satellite platform on the terminal is calculated using Newton-Euler recursion. Environmental interference and rotational friction are considered as norm-bounded total disturbances, including:

[0047] (1) Establish a model of a deeply coupled spaceborne periscope laser communication terminal under the influence of multiple sources of interference, including space environment interference, floating satellite platform coupling torque, and shaft friction torque:

[0048]

[0049] in, Let Z be the moment of inertia of the first periscope-type communication terminal connecting rod at the center of mass along the Z-axis. and These correspond to the rotational inertia of the second periscope-type communication terminal linkage at its center of mass along the X, Y, and Z axes, respectively; θ1 and θ2 are the rotation angles of the first terminal joint and the second terminal joint, respectively. and These are the angular velocities of the first and second terminal joints, respectively. and τ1 and τ2 are the angular accelerations of the first and second terminal joints, respectively; L2 is the link length of the second terminal joint; m2 is the mass of the second terminal joint; τ1 and τ2 are the control torques of the first and second terminal joints, respectively. and These are the coupling torques of the first and second terminal joints, respectively. and These are the entrainment and coupling torques caused by the satellite's attitude motion on the first and second terminal joints, respectively. and The disturbance torque of environmental interference and shaft friction on the first and second terminal joints.

[0050] (2) To further describe the influence of the floating satellite platform on the periscope terminal's entrainment coupling torque, the entrainment coupling torque can be obtained through Newton-Euler recursion calculation:

[0051]

[0052] in, and These correspond to the X-axis and Y-axis rotational inertia of the first periscope-type communication terminal linkage at its center of mass, respectively; ω x ω y and ω z These are the attitude angular velocities of the satellite along the X, Y, and Z axes, respectively. and L1 represents the angular acceleration of the satellite along the X, Y, and Z axes, respectively; L2 represents the link length of the first terminal joint; L3 represents the link length of the second terminal joint; m1 represents the mass of the first terminal joint; m2 represents the mass of the second terminal joint; A1 and B1 are auxiliary variables.

[0053] (3) The dynamic model of the periscope-type communication terminal is transformed into an integral cascade type through state transformation, and x1 = [θ1θ2] is defined. T , in[·]T The transpose of · yields the transformed model:

[0054]

[0055] in, diag{·} denotes a diagonal matrix; and Let x1 and x2 be the first derivatives; τ = [τ1 τ2] T Input torque to the two joints of the communication terminal; The coupling torque between the two joints of the communication terminal; The coupling torque between the satellite's attitude motion and the two joints of the communication terminal; This refers to the environmental interference and shaft friction torque experienced by the two joints of the communication terminal.

[0056] The second step involves designing a fixed-time interference observer based on the deeply coupled spaceborne periscope-type laser communication terminal model established in the first step. This observer rapidly estimates external environmental interference, satellite motion coupling torque, and axis friction, obtaining the total disturbance within a fixed time period. Estimated value:

[0057]

[0058] Where z1 and z2 are the observer states, and their first derivatives are respectively Specifically, z1 is the estimated value of the angular velocity x2 of the communication terminal joint; z2 is the estimated value of the total disturbance D experienced by the communication terminal joint; K1 = diag{k1,k2} and K2 = diag{k3 / η,k4 / η} are the observer parameter matrices, where k1, k2, k3, k4 and η are the observer parameters to be selected, which must satisfy k1 > 0, k2 > 0, k3 > 0, k4 > 0. And 0 < η < 1; the auxiliary functions Φ1(·) and Φ2(·) can be expressed as:

[0059]

[0060]

[0061] Where a is any n-dimensional vector, a i Let represent the i-th row of vector a; α1 and β1 are the observer parameters to be selected, which must satisfy 0.5 < α1 < 1 and 1 < β1 < 1.5; |·| represents the absolute value of ·; sgn(·) is the sign function; φ1(·) and φ2(·) represent intermediate variables, specifically expressed as

[0062] The third step is to design a nominal fixed-time controller. Using the interference observer and the total disturbance estimate from the second step, a fixed-time composite disturbance rejection controller is formed to suppress interference compensation errors.

[0063] Take the expected pointing angle x of the communication terminal d Desired pointing angular velocity With desired pointing angle acceleration Define the angle tracking error ε1 = x1 - x d Angular velocity tracking error The controller is designed to be in the following form:

[0064]

[0065]

[0066] Among them, s i Represents the i-th row element of the sliding surface s; and These represent the i-th row elements of the tracking errors ε1 and ε2, respectively; This represents the element in the i-th row of the state variable z2 of the disturbance observer; Represents a nonlinear diagonal matrix f x The element in the i-th row and i-th column; Represents the desired pointing angular acceleration The elements in the i-th row; k5, k6, k7, α2, λ1, and μ1 are controller parameters, which must satisfy k5 > 0, k6 > 0, k7 > 0, α2 > 1, λ1 > 0, and μ1 > 0; ln(·) is the natural logarithm function; the final controller output torque is τ = [τ1τ2]. T .

[0067] The fourth step involves analyzing and guiding the selection of observer and controller parameters based on the pointing time requirements of the communication terminal, to complete the fixed-time disturbance rejection control of the spaceborne laser communication terminal under motion coupling, including:

[0068] (1) When the lumped interference derivative of the two joints of the communication terminal has an upper bound σ1, that is, it satisfies express The derivative, express The derivative; there exists a positive constant E when the observer parameter η is sufficiently small, such that the interference observer's error in estimating D occurs within time t ≥ T. dmax It then converges to ||D-z²|| < E in the neighborhood of E, where ||·|| denotes the norm of ·. The convergence time T dmax satisfy:

[0069]

[0070] Where c is a positive constant. The interference observer parameters satisfy k1 > 0, k2 > 0, k3 > 0, k4 > 0, Given that 0 < η < 1, the convergence time can be adjusted by setting the observer parameters 0.5 < α1 < 1 and 1 < β1 < 1.5. Furthermore, selecting larger values ​​for k1, k2, k3, and k4, and smaller values ​​for η, will improve the observer estimation speed.

[0071] (2) After the interference observer estimation error converges to ||D-z2||<E, the communication terminal expects the pointing angle error to be within time t>T. dmax +T Cmax After convergence to near zero, where T Cmax satisfy:

[0072]

[0073] in, e represents the natural constant; the controller parameter k6 must satisfy k6 > E; under the premise that k5 > 0, k6 > 0, k7 > 0, α2 > 1, λ1 > 0 and μ1 > 0, the convergence time can be shortened by appropriately increasing the controller parameters k5, k6 and k7. In addition, the convergence time can also be shortened by increasing α2 and λ1 or decreasing μ1.

[0074] like Figure 2 As shown, the structure of this invention begins with establishing a laser communication terminal pointing model containing space environment interference, floating satellite platform coupling torque, and shaft friction torque. A fixed-time interference observer is designed to estimate multi-source interference. A nominal fixed-time controller is designed and combined with the interference observer to form a fixed-time composite anti-interference controller. This is done in conjunction with the pointing time requirements of the communication terminal, and the analysis guides the selection of observer and controller parameters.

[0075] This invention employs an interference observer and controller with fixed-time characteristics, which can achieve fixed-time anti-interference control of the terminal under the influence of multi-source interference and keep the pointing error within a small range. It has the characteristics of strong robustness and fast pointing speed, and is suitable for communication terminal pointing systems with multi-source interference and fast pointing requirements.

[0076] The method of this invention for laser communication terminal pointing control allows for the use of a single pointing control strategy even under conditions of multiple sources of interference and convergence time, while maintaining good dynamic and steady-state performance of the controller. Furthermore, compared to controllers without interference estimation and compensation mechanisms, the control effect can withstand greater spatial environmental interference, and the interference estimation error and desired pointing angle error can stabilize within a fixed time, achieving the requirements of speed, accuracy, and robustness.

[0077] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A fixed-time anti-interference control method for a spaceborne laser communication terminal under motion coupling, characterized in that, Includes the following steps: The first step is to establish a model of a deep-coupled spaceborne periscope laser communication terminal under the influence of multiple sources of interference, including space environment interference, coupling torque of floating satellite platform, and rotational friction torque. The coupling torque of floating satellite platform on terminal is calculated by Newton-Euler recursion, and environmental interference and rotational friction are regarded as norm-bounded total disturbances. The second step involves designing a fixed-time interference observer to quickly estimate external environmental interference, satellite motion coupling torque, and shaft friction based on the deep-coupled spaceborne periscope laser communication terminal model established in the first step, thereby obtaining the total disturbance estimate within a fixed time period. The third step is to design a nominal fixed-time controller. Using the interference observer and the total disturbance estimate from the second step, a fixed-time composite disturbance rejection controller is formed to suppress interference compensation errors, including: Determine the desired pointing angle of the communication terminal Desired pointing angular velocity With desired pointing angle acceleration Define angle tracking error Angular velocity tracking error The controller is designed as follows: Sliding surface The row element equal to tracking error The row element and sum; in, Represents the sliding surface The row element; and These represent the tracking errors respectively. and The row element; Represents the state variables of the disturbance observer The row element; Represents a nonlinear diagonal matrix The Line number Column elements; Represents the desired pointing angular acceleration The row element; , , , , and For controller parameters, satisfy , , , , and ; It is a natural logarithmic function; the final controller output torque is , Equal to coupling torque minus Subtract ; The fourth step involves analyzing and guiding the selection of observer and controller parameters based on the pointing time requirements of the communication terminal, thereby completing the fixed-time anti-disturbance control of the spaceborne laser communication terminal under motion coupling; specifically, when the lumped interference derivative of the two joints of the communication terminal has an upper bound... That is, satisfying , express The derivative, express The derivative; there exists a positive constant. In observer parameters Small enough that the interference observer interferes with the Estimation error in time Later converged to about Within the neighborhood , express The norm; when the interference observer estimation error converges to Afterwards, the communication terminal expects the pointing angle error to occur within time. It then converges to near zero. For intermediate parameters; Convergence time Less than or equal to ; in, It is a positive constant; when the interference observer parameters satisfy , , , , , and Under the premise of adjusting the observer parameters and Adjust the convergence time; by increasing the , , , and reduce Improve the speed of observer estimation; intermediate parameters Less than or equal to ; in, ; Represents the natural constant; controller parameters Must meet ; in satisfying , , , , and Under the premise of appropriately increasing the controller parameters , and Shorten the convergence time, or by increasing... and or reduce Shorten the convergence time.

2. The fixed-time anti-interference control method for a spaceborne laser communication terminal under motion coupling according to claim 1, characterized in that: The first step includes: Establish a model of a deeply coupled spaceborne periscope-type laser communication terminal under the influence of multiple sources of interference, including space environment interference, coupling torque of floating satellite platforms, and rotational friction torque: ； in, Let Z be the moment of inertia of the first periscope-type communication terminal connecting rod at the center of mass along the Z-axis. , and These correspond to the rotational inertia of the second periscope-type communication terminal connecting rod at its center of mass along the X, Y, and Z axes, respectively. and These are the rotation angles of the first and second terminal joints, respectively. and These are the angular velocities of the first and second terminal joints, respectively. and These are the angular accelerations of the first and second terminal joints, respectively. The length of the connecting rod at the second terminal joint; The mass of the second terminal joint; and These are the control torques for the first and second terminal joints, respectively. and These are the coupling torques of the first and second terminal joints, respectively. and These are the entrainment and coupling torques caused by the satellite's attitude motion on the first and second terminal joints, respectively. and The disturbance torque of environmental interference and shaft friction on the first and second terminal joints.

3. The fixed-time anti-interference control method for a spaceborne laser communication terminal under motion coupling according to claim 2, characterized in that: The first step also includes: To further describe the influence of the floating satellite platform on the periscope terminal's entrainment coupling moment, the entrainment coupling moment was obtained through Newton-Euler recursive calculation: ； in, and These correspond to the X-axis and Y-axis rotational inertia of the first periscope-type communication terminal connecting rod at the center of mass, respectively. , and These are the attitude angular velocities of the satellite along the X, Y, and Z axes, respectively. , and These are the attitude angular accelerations of the satellite along the X, Y, and Z axes, respectively. The length of the connecting rod at the first terminal joint; The length of the connecting rod at the second terminal joint; The mass of the first terminal joint; The mass of the second terminal joint; and It is an auxiliary variable.

4. The fixed-time anti-interference control method for a spaceborne laser communication terminal under motion coupling according to claim 3, characterized in that: The first step also includes: The dynamic model of the periscope-type communication terminal is transformed into an integral cascade type through state transformation, and defined as follows: , ,in express The transpose of the model yields the transformed model: ； in, , Represents a diagonal matrix; and State variables and The first derivative; Input torque to the two joints of the communication terminal; The coupling torque between the two joints of the communication terminal; The coupling torque between the satellite's attitude motion and the two joints of the communication terminal; This refers to the environmental interference and shaft friction torque experienced by the two joints of the communication terminal.

5. The fixed-time anti-interference control method for a spaceborne laser communication terminal under motion coupling according to claim 4, characterized in that: In the second step, the total disturbance is obtained within a fixed time period. The estimated value is: ； in, , For the observer state, its first derivatives are respectively , Specifically, For the joint angular velocity of the communication terminal The estimated value; Total disturbance experienced by the joints of the communication terminal The estimated value; and The observer parameter matrix, , , , and The parameters of the observer to be selected satisfy... , , , , , and Auxiliary functions and Represented as: ； ； in, For any n-dimensional vector, Representing vectors The OK; and The parameters of the observer to be selected must satisfy the following conditions: and ; express The absolute value; It is a symbolic function; and This represents an intermediate variable, specifically as follows: , .

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