Hierarchical control method and system for reconfigurable rigid-flexible coupling space on-orbit assembly robot

Abstract

The invention relates to the technical field of space on-orbit robot control, in particular to a reconfigurable rigid-flexible coupling space on-orbit assembly robot hierarchical control method and system, and the control system comprises a spacecraft formation control system and a rigid-flexible coupling robot control system. According to the rigid-flexible coupling robot control system, the working stroke of a robot can be changed through reconfiguration of spacecraft formation re-planning, and on the basis of an upper-layer task planner, a controller fuses multi-perception information of vision, force sense and position to achieve hierarchical control over a flexible cable driving robot and a mechanical arm. The control method is oriented to space large-size component assembly tasks, the robot hierarchical controller fused with multi-source information is designed by decoupling robot kinematics and dynamics and combining operation scene requirements, the overall operation efficiency and precision of the robot are improved, and the adaptability of the robot to different on-orbit tasks is enhanced.

Description

Technical Field

[0001] This invention relates to the field of space on-orbit robot control and operation technology, specifically to a reconfigurable rigid-flexible coupled space on-orbit assembly robot hierarchical control method and system. Background Technology

[0002] As aerospace engineering advances towards higher goals such as deep space exploration and on-orbit servicing, the continuous evolution of space technology and the significant increase in the complexity of space exploration missions have placed more stringent demands on the design and control performance of on-orbit space robots. For ultra-large-scale assembly tasks in space, the dual constraints of launch vehicle payload capacity and spatial dimensions mean that the assembly work cannot be completed on the ground before launch. On-orbit space robots are beginning to be used to complete these space assembly tasks. The high precision requirements for robot operation and the impact of the extreme space environment further place higher demands on the stability and robustness of the robot's control system.

[0003] Currently, several robot-based technical solutions have been proposed for on-orbit assembly missions, which can be summarized into three types. First, there is the human-robot collaborative robotic arm teleoperation solution. This type of solution is mainly used on large robotic arms in space stations. Through master-slave teleoperation combined with force-sensing control of the robotic arm, it autonomously completes assembly tasks or collaborates with extravehicular astronauts. This method is relatively mature and has been widely used in on-orbit assembly missions. However, it suffers from communication latency issues in the extreme environment of space. Furthermore, this method relies on astronauts for operation, posing significant risks, and assembling structures far exceeding the size of the robotic arm is relatively difficult. Second, there is modular robot cluster assembly. By designing modular, lightweight robots, multiple robot clusters collaborate to complete assembly tasks. The system is robust and efficient, but its complexity is high, collaborative control is difficult, and the lightweight design affects assembly accuracy. Third, there is the biomimetic climbing robot. This robot moves by climbing on the surface of complex structures and completes assembly tasks through motion planning and force-sensing control. It offers high redundancy and high operational accuracy, but is limited by its own structural constraints, making it unable to perform heavy-load operations such as moving large components. Whether the robot can adhere to the attached structure in the extreme environment of space requires further research.

[0004] Chinese invention patent application number CN202511465298.8 proposes a reconfigurable rigid-flexible coupled space on-orbit assembly robot. Using a spacecraft cluster as a mobile base, the robot dynamically adjusts the relative posture between spacecraft according to mission requirements. Each spacecraft is equipped with a flexible cable actuator, which drives the movement of a moving platform. A robotic arm is mounted on the moving platform, and the on-orbit assembly task is completed through the coordinated control of the moving platform and the robotic arm. The flexible cable system and the robotic arm form a rigid-flexible coupling characteristic, possessing reconfigurable working stroke, and can effectively perform on-orbit operations on variable-sized, unstructured space targets. However, in the microgravity environment of space, the flexible cable system and the robotic arm need to coordinate to perform assembly tasks; otherwise, the efficiency and accuracy of the robot's operation will be severely affected. Therefore, it is necessary to design a robot control system to improve the stability of the operation process, thereby ensuring and improving efficiency and accuracy.

[0005] Chinese invention patent application number CN202110481248.4 proposes a design method and system for a position observer of an adaptive coordinated control space robotic arm. This space robotic arm is installed on a spacecraft and designs a mission space observer, adaptive dynamic coordinated control law and parameter update law to realize the spacecraft attitude adjustment and the end effector's tracking of the desired trajectory in the mission space. It overcomes the parameter uncertainty problem in space on-orbit missions and can adapt to different on-orbit robot operation tasks. However, this method is not applicable to the robot in this scheme. There is a kinematic and dynamic coupling relationship between the cable-driven parallel robot and the robotic arm in this scheme. It is necessary to conduct a complete analysis of the robot coupling relationship and complete the decoupling to achieve hierarchical control of the robot.

[0006] Chinese invention patent application number CN202410686786.0 proposes a fuzzy reinforcement learning method for pre-time vibration suppression in rigid-flexible coupled robots, which solves the technical problems of pre-time trajectory tracking and elastic vibration suppression in rigid-flexible coupled robot systems. However, this method does not take into account the special constraints of the space on-orbit environment. The microgravity environment will cause changes in the mass distribution and inertial parameters of the robot system. The robot modeling method used in this method is too simplified and is not suitable for the rigid-flexible coupled robot in this solution. Summary of the Invention

[0007] The purpose of this invention is to provide a layered control method and system for a reconfigurable rigid-flexible coupled space on-orbit assembly robot, thereby solving the technical problem of insufficient reliability of the layered control method for the reconfigurable rigid-flexible coupled space on-orbit assembly robot.

[0008] The solution of the present invention to the above-mentioned technical problems is as follows: A hierarchical control method for a reconfigurable rigid-flexible coupled on-orbit assembly robot includes the following steps: S1. Based on the target location and operational requirements, the spacecraft formation is replanned using the PSO-SCP method to generate a reconstructed trajectory. The spacecraft formation then completes the formation change and reaches the designated location. S2. Based on the specifications of the truss to be assembled, determine the assembly sequence of the truss units and the pre-assembly end pose of the rigid-flexible coupling robot when assembling each truss unit. S3. Determine the position of the moving platform and the configuration of the robotic arm joints based on the pre-assembled end-effector pose of the rigid-flexible coupling robot. S4. Determine the robot's kinematics and dynamics model based on the robot's current configuration data. Drive the moving platform through the flexible cable and use a cable-arm cooperative movement force / position hybrid PID controller to control the robot arm to adjust the end pose to the robot's pre-assembled posture by combining the moving platform position and the robot arm joint configuration. S5. A dynamic platform anti-interference - robotic arm assembly force / position hybrid controller is used to keep the dynamic platform stable until the robotic arm completes the assembly of a single truss unit; S6. Repeat steps S4 and S5 until all truss units are assembled.

[0009] Further specifying, step S1 includes the following steps: Obtain initial parameters for spacecraft formation: initial position Initial scale of spacecraft formation and the initial angle of the spacecraft formation ; Determine spacecraft formation target parameters: target position Target Scale and target angle ; Based on the initial parameters and target parameters of the spacecraft formation, a hierarchical optimization algorithm combining particle swarm optimization and sequential convex optimization is adopted to solve the spacecraft formation trajectory planning under the constraints of Clohessy-Wiltshire equation dynamics, spacecraft collision avoidance constraints, and cable length constraints with relaxation variables. Adjust the spacecraft formation based on the solved spacecraft formation trajectory plan.

[0010] Further specifying, the optimization algorithm combining particle swarm optimization and sequential convex optimization, based on the initial parameters and target parameters of the spacecraft formation, and under the constraints of the Clohessy-Wiltshire equations, spacecraft collision avoidance constraints, and cable length constraints with relaxation variables, solves the spacecraft formation trajectory planning problem, including the following steps: Construct the objective function for spacecraft formation trajectory planning:

[0011]

[0012]

[0013]

[0014]

[0015]

[0016] in, For spacecraft formation fuel consumption, For discretized time periods, For the long walk, For the first One spacecraft, The total number of spacecraft in the spacecraft formation. For positional weights, For the position error of the moving platform terminal, For scale weights, For spacecraft formation scale error, For angle weighting, This refers to the spacecraft formation angle error term. for Time of the first The motion state of a spacecraft The system state matrix in the Clohessy-Wiltshire equations is... This is the control input matrix in the Clohessy-Wiltshire equation; For the rotation matrix of spacecraft formation, Let be the reference basis vector for the motion of the moving platform; The length of the flexible rope, As slack variables, The minimum safe distance between spacecraft This is the maximum thrust of the spacecraft.

[0017] Further specifying, step S2 includes the following steps: The assembly of each truss unit is determined according to the specifications of the truss to be assembled. The position of the robotic arm's end effector during assembly is determined based on the assembly sequence of each truss unit. :

[0018] in, This represents the coordinates of the robotic arm's end effector along the X-axis in the global coordinate system. This represents the coordinates of the robotic arm's end effector along the Y-axis in the global coordinate system. This refers to the coordinates of the robotic arm's end effector along the Z-axis in the global coordinate system; the global coordinate system... O Located at the center of the lead spacecraft; The yaw angle at the end of the robotic arm. The pitch angle at the end effector of the robotic arm. This is the roll angle at the end of the robotic arm.

[0019] Further specifying, step S3 includes the following steps: S10. Select the end-effector pose of a robotic arm during the assembly process as the current target pose of the robotic arm end-effector. ; S11. Set the robot's end-effector position Convergence threshold Robot end effector posture Convergence threshold Feasibility function of flexible cable tension threshold and the position of the robot's moving platform and the configuration of the robotic arm joints. ;

[0020] in, To determine the position of the moving platform in the global coordinate system, For the joint angle of the robotic arm; Let X be the coordinate value of the moving platform along the X-axis in the global coordinate system. This refers to the coordinates of the moving platform along the Y-axis in the global coordinate system. The first in the robotic arm The components of a joint angle; S12. Initialize the robot's moving platform position and robotic arm joint configuration. Let the number of iterations be... 1. Determine the number of iterations Does it meet the requirements? If yes, continue; if no, end. S13. Based on the current position of the robot's moving platform and the configuration of the robotic arm joints... Update the position of the global coordinate system of the moving platform. ; S14. Based on the current position of the global coordinate system of the moving platform Calculate the current pose of the robotic arm's end effector ; S15. Based on the position of the robotic arm's end effector Calculate the current target pose of the robotic arm's end effector. Position error and angle error ; S16. Based on position error and angle error The incremental values ​​of the robot's moving platform position and the manipulator joint configuration are calculated using the damped least squares method. :

[0021]

[0022] in, For the hybrid Jacobian matrix of the robot end effector, The damping factor, The error matrix consists of position error and angle error; For dynamic platform Jacobian matrix, For the Jacobian matrix of the robotic arm, Jacobi, the location of the moving platform The dynamic platform posture is comparable; S17. Determine the number of iterations. If the set period has been reached, then perform tension optimization and feasibility assessment to obtain the optimized cable tension; otherwise, proceed to step S18. S18. Increment based on the position of the robot's moving platform and the configuration of the robotic arm joints. Or, based on the optimized cable tension, let k+1 and update the current robot motion platform position and robotic arm joint configuration; S19. Obtain the current robot pose based on the updated moving platform position and robotic arm joint configuration, and calculate the pose relative to the current robotic arm end-effector target pose. Position error and angle error ; S20. Determine the updated position error. and attitude error Do they satisfy the following conditions simultaneously:

[0023]

[0024] in, For the robot end-effector position error, This refers to the robot's end-effector posture error. If so, then the current target pose of the robotic arm's end effector is obtained. The corresponding robot cable length and the angles of each joint of the robotic arm are determined; otherwise, the current pose is considered unsolvable.

[0025] To further define the process, the optimized cable tension obtained through tension optimization and feasibility assessment includes the following steps: Based on the robot inverse dynamics model, and according to the current position of the moving platform and the configuration of the robotic arm joints... Calculate the current tension vector of the flexible cable. ; Calculate the feasible violation of cable tension :

[0026] If satisfied If the result is positive, then null space optimization is initiated to obtain the corrected cable tension; otherwise, the current tension vector is... Optimization was performed to obtain the optimized cable tension:

[0027]

[0028]

[0029] in, This is the weight matrix. Feasibility function for cable tension The threshold.

[0030] Further specifying, step S4 includes the following steps: Trajectory planning is performed using an offline trajectory planner to generate the desired trajectory for the end effector, which includes a time series. The desired trajectory is sampled, and the end Cartesian space pose of each sampling point is converted into the position of the moving platform and the joint configuration of the robotic arm by a tension-optimized robot inverse kinematics solver, resulting in the desired position sequence of the moving platform, the desired tension sequence of the flexible cable, the desired joint angle sequence of the robotic arm, and the desired joint torque sequence. A force feedback PID controller for a cable-driven parallel robot is used to measure the difference between the desired cable tension and the actual cable tension. As the PID control input, the difference between the desired and actual cable lengths is used. As a feedforward input, a flexible cable length control signal is generated. :

[0031] in, , and All are PID parameters. For feedforward gain parameters; A cascaded PID controller is used for the robotic arm. The outer loop position controller takes the desired joint angle as input, compares it with the actual joint angle, and then generates the desired joint angular velocity through the position PID controller. The inner loop velocity controller takes the actual joint angular velocity as input, compares it with the actual joint angular velocity, and then outputs the basic joint torque through the velocity PID controller. The final control output is:

[0032] Through the coordinated control of the cable-driven parallel robot force feedback PID controller and the robotic arm cascade PID controller, the flexible cable system and the robotic arm are driven to move, so that the robot end effector reaches the pre-assembled posture.

[0033] Further specifying, step S5 includes the following steps: The assembly unit image is acquired by the end-effector camera of the robotic arm, and the coarse alignment of the shaft and hole is achieved by using a 6D pose estimation algorithm. Activate the moving platform damping compensation controller, taking the moving platform position during coarse alignment as the desired position. According to the actual position of the moving platform Generate compensated position instructions and speed command :

[0034]

[0035] The robotic arm's fuzzy adaptive admittance controller is activated, based on the interaction force measured by the end effector force sensor. The deviation from the desired contact force is adjusted in real time by a fuzzy logic system to generate a reference trajectory for the robotic arm. :

[0036] in, This is the stiffness adjustment factor. As the inertia adjustment factor, This is the damping adjustment factor; The compensated position command and speed command and robotic arm reference trajectory Input the robot inverse dynamics model to calculate the optimized cable tension and robotic arm joint torque; A flexible cable tension PID controller is used to track the optimized flexible cable tension, and a robotic arm PID controller is used to track the optimized robotic arm joint torque, so as to achieve coordinated control of the moving platform's anti-interference stability and the robotic arm's compliant assembly. The contact stage and insertion stage are distinguished based on the characteristics of the contact force signal during the assembly process. The admittance control parameters are adaptively adjusted based on the fuzzy rule table to complete the fine alignment and insertion assembly of the shaft and hole.

[0037] Further defining the fuzzy adaptive admittance controller model for the robotic arm is as follows:

[0038] in, , and All of these are admittance parameters.

[0039] A reconfigurable rigid-flexible coupled spatial on-orbit assembly robot hierarchical control system, used to implement the above-mentioned reconfigurable rigid-flexible coupled spatial on-orbit assembly robot hierarchical control method, includes: Spacecraft formation control system: The spacecraft formation system mission planning layer completes the replanning of the spacecraft formation through the PSO-SCP method, and realizes the replanning of the robot's working stroke based on the assembly mission requirements and the trajectory obtained from the replanning. The perception and communication layer enables master-slave communication between the spacecraft in the formation and can obtain the current position and attitude information of the spacecraft. The single-spacecraft propulsion layer enables formation reconfiguration between individual spacecraft according to a specified trajectory, allowing them to reach the designated operational location. Rigid-flexible coupling robot hierarchical control system: The robot sensing layer perceives real-time information about the robot itself and its environment. The rigid-flexible coupled robot task planning layer confirms the pre-assembly pose and task objectives of each robot gantry unit. The robot control layer performs real-time calculations of robot kinematics and dynamics, as well as controller data; it controls the coordinated movement of the moving platform and the robotic arm to grasp the truss unit to the pre-assembly pose through a cable-arm cooperative motion force / position hybrid PID controller; and it controls the moving platform to maintain stability through a moving platform anti-interference - robotic arm assembly force / position hybrid controller. The robot drive layer inputs decoupled control quantities to the robotic arm drive and the cable-connected parallel robot drive for hierarchical control to complete the assembly.

[0040] The beneficial effects of this invention are as follows: 1. This invention addresses the formation reconfiguration and trajectory planning requirements of mobile spacecraft swarms under dynamic platform constraints. It employs the PSO-SCP hierarchical optimization method to effectively solve the multi-spacecraft formation reconfiguration trajectory planning problem under Clohessy-Wiltshire equation dynamic constraints, spacecraft collision avoidance constraints, and cable length constraints. This method can plan the transfer trajectory with optimal fuel consumption while ensuring absolute safety, significantly improving the economy and sustainability of space missions. It ensures that the spacecraft swarm can quickly complete formation reconfiguration and accurately reach the designated position according to on-orbit assembly mission requirements, while maintaining a stable formation state, reducing the risk of assembly accuracy deviations caused by formation instability.

[0041] 2. This invention proposes an inverse kinematics solution method that integrates tension optimization and feasibility assessment. Tension feasibility is taken as one of the core convergence conditions, and periodic null space optimization is introduced to ensure that the solved robot moving platform position and manipulator joint configuration not only meet the end-effector pose accuracy requirements, but also ensure that the cable tension is always within a safe range. This fundamentally avoids the risk of system failure due to entering singular configurations or tension overload, and greatly improves the reliability of control.

[0042] 3. This invention designs a multi-source information fusion hierarchical control architecture, deeply integrating multiple types of perception information such as vision, force, cable tension, cable length, and joint position / velocity. Based on robot kinematics and tension optimization, it combines a cable-driven parallel robot force feedback PID controller with a torque feedforward compensation manipulator cascade PID controller for efficient two-DOF large-space displacement of the moving platform and six-DOF coordinated large-space motion of the manipulator. In the assembly process, visual positioning and force perception are integrated, and the upper-level planning and compensation layer uses multi-source information deviation to dynamically adjust the moving platform interference. Fuzzy adaptive optimization of the manipulator admittance control parameters is achieved, and the manipulator force / position hybrid control completes the assembly task, significantly improving the adaptability and reliability of complex on-orbit assembly. Attached Figure Description

[0043] Figure 1 This is a structural diagram of the reconfigurable rigid-flexible coupled space on-orbit assembly robot of the present invention; Figure 2 This is a step diagram of the reconfigurable rigid-flexible coupled spatial on-orbit assembly robot layered control method of the present invention; Figure 3 This is a flowchart of the on-orbit re-planning process for spacecraft formations according to the present invention. Figure 4 This is a visualization diagram of the on-orbit replanning path of the spacecraft formation according to the present invention; wherein, (A) is a 3D diagram of the on-orbit replanning path of the spacecraft formation, and (B) is the projection of the on-orbit replanning path of the spacecraft formation onto the XY plane; Figure 5This is a diagram showing the change in formation configuration parameters of the spacecraft formation during on-orbit replanning of the path according to the present invention; wherein, (A) is a diagram showing the change in spacecraft formation scale, and (B) is a diagram showing the change in spacecraft formation angle; Figure 6 This is a schematic diagram of the truss assembly sequence of the present invention; Figure 7 This is a simplified structural diagram of the reconfigurable rigid-flexible coupled space on-orbit assembly robot of the present invention; Figure 8 This is a flowchart of the robot inverse kinematics solution method that combines optimization and feasibility assessment according to the present invention. Figure 9 The first example diagram shows the pose result of the robot inverse kinematics solution according to the present invention; wherein, (A) is the first example 3D space solution result diagram, and (B) is the XY plane projection diagram of the first example solution result; Figure 10 The second example diagram shows the pose result of the robot inverse kinematics solution according to the present invention; wherein, (A) is the 3D space solution result diagram of the second example, and (B) is the XY plane projection diagram of the solution result of the second example; Figure 11 This is a numerical visualization diagram of the iterative solution of the robot inverse kinematics of the present invention; wherein, (A) is a schematic diagram of the first example position error and angle error and the number of iterations, (B) is a schematic diagram of the second example position error and angle error and the number of iterations, (C) is a schematic diagram of the first example tension and inspection interval, and (D) is a schematic diagram of the second example tension and inspection interval. Figure 12 This is a schematic diagram of the cable arm cooperative movement force / position hybrid PID controller of the present invention; Figure 13 This is a schematic diagram of the motion platform anti-interference-robotic arm assembly force / position hybrid controller of the present invention; Figure 14 This is a schematic diagram of the reconfigurable rigid-flexible coupled spatial on-orbit assembly robot layered control system of the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0045] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0046] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0047] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0048] This invention provides a hierarchical control method for a reconfigurable rigid-flexible coupled space-on-orbit assembly robot. The controlled object is the reconfigurable rigid-flexible coupled space-on-orbit assembly robot, which uses a spacecraft formation as its base. Each spacecraft has a flexible cable-driven platform mounted on its bottom, and each platform is connected to a moving platform via a flexible cable. A multi-degree-of-freedom robotic arm is mounted on the bottom of the moving platform, with its end effector being a force sensor and a vision sensor for grasping. The flexible cable-driven platform drives the moving platform to complete planar motion via a flexible cable drive device. The moving platform, in conjunction with the robotic arm, completes the space-on-orbit assembly task. (Refer to...) Figure 1 The moving platform and the robotic arm are combined to form a rigid-flexible coupling robot. Through kinematic and dynamic analysis of the rigid-flexible coupling robot, a flexible cable drive device and different motor drive controls in the robotic arm are designed based on its kinematics and dynamics. This completes the coordinated control of the cable-driven parallel robot and the serial robotic arm, reduces the robot's own vibration during assembly, and improves assembly accuracy.

[0049] Example 1 refer to Figure 1 This invention provides a hierarchical control method for a reconfigurable rigid-flexible coupled on-orbit assembly robot, comprising the following steps: S1. Based on the target location and operational requirements, the spacecraft formation is replanned using the PSO-SCP method to generate a reconstructed trajectory. The spacecraft formation completes the formation change and reaches the designated location. The target location is the center position of the truss to be assembled. The purpose is to plan and control the alignment of the center position of the spacecraft formation with the target position.

[0050] S2. Based on the specifications of the truss to be assembled, determine the assembly sequence of the truss units and the pre-assembly end pose of the rigid-flexible coupling robot when assembling each truss unit. S3. Determine the position of the moving platform and the configuration of the robotic arm joints based on the pre-assembled end-effector pose of the rigid-flexible coupling robot. S4. Determine the robot's kinematics and dynamics model based on the robot's current configuration data. Drive the moving platform through the flexible cable and use a cable-arm cooperative movement force / position hybrid PID controller to control the robot arm to adjust the end pose to the robot's pre-assembled posture by combining the moving platform position and the robot arm joint configuration. S5. A dynamic platform anti-interference - robotic arm assembly force / position hybrid controller is used to keep the dynamic platform stable until the robotic arm completes the assembly of a single truss unit; S6. Repeat steps S4 and S5 until all truss units are assembled.

[0051] To further explain, step S1 includes the following steps: Obtain initial parameters for spacecraft formation: initial position Initial scale of spacecraft formation and the initial angle of the spacecraft formation ; Determine spacecraft formation target parameters: target position Target Scale and target angle ; Specifically, the initial position and initial size of the spacecraft formation are known. The relevant parameters of the spacecraft formation are obtained based on the initial position of the spacecraft formation and the target position where the spacecraft formation will move to the assembly position.

[0052] Based on the initial parameters and target parameters of the spacecraft formation, a hierarchical optimization algorithm combining particle swarm optimization and sequential convex optimization is adopted to solve the spacecraft formation trajectory planning under the constraints of Clohessy-Wiltshire equation dynamics, spacecraft collision avoidance constraints, and flexible cable length constraints with relaxation variables. The algorithm gradually minimizes the fuel consumption and terminal position error of the spacecraft formation in a hierarchical manner. Specifically, based on the initial parameters and target parameters of the spacecraft formation, a hierarchical optimization algorithm combining particle swarm optimization and sequential convex optimization is used to solve the spacecraft formation trajectory planning under the constraints of the Clohessy-Wiltshire equations, spacecraft collision avoidance constraints, and cable length constraints with relaxation variables. The steps include: Construct the objective function for spacecraft formation trajectory planning:

[0053]

[0054]

[0055]

[0056]

[0057]

[0058] in, For spacecraft formation fuel consumption, For discretized time periods, For the long walk, For the first One spacecraft, The total number of spacecraft in the spacecraft formation. For positional weights, For the position error of the moving platform terminal, For scale weights, For spacecraft formation scale error, For angle weighting, This refers to the spacecraft formation angle error term. for Time of the first The motion state of a spacecraft The system state matrix in the Clohessy-Wiltshire equations is... This is the control input matrix in the Clohessy-Wiltshire equation; For the rotation matrix of spacecraft formation, Let be the reference basis vector for the motion of the moving platform; l The length of the flexible rope, As slack variables, The minimum safe distance between spacecraft This is the maximum thrust of the spacecraft.

[0059] In the outer layer, the particle swarm optimization (PSO) algorithm is used to optimize the formation scale. and angle A global search is performed using low-dimensional parameters, and its fitness function... Includes a basic objective term and a penalty function term for simple constraints to achieve fast convergence:

[0060]

[0061]

[0062] refer to Figure 3 ,in, This indicates that the equal-form constraint in the optimization problem is subject to a quadratic penalty function. The inequality constraints are represented by a quadratic penalty function. To accelerate the optimization speed of PSO, only the geometric and acceleration constraints of the formation are retained, excluding the flexible cable constraints, as these are computationally complex. This avoids frequent calls to complex nonlinear constraints at the outer layer, ensuring rapid convergence. The convergence condition is... If the conditions are not met, the particle position and velocity are updated and the fitness function is recalculated.

[0063] The optimal solution output by PSO is used as the initial guess, and the Sequential Convex Optimization (SCP) method is called. SCP linearizes the nonlinear constraints at the current point, constructs and solves the convex subproblem, and gradually reduces the slack variables and trust domain through iterative updates. Finally, the replanning of the spacecraft formation is completed to obtain a high-precision spacecraft formation trajectory that ensures that fuel consumption is approximately optimal and satisfies all safety constraints.

[0064] Adjust the spacecraft formation based on the solved spacecraft formation trajectory plan.

[0065] refer to Figure 4 and Figure 5The initial formation size of the spacecraft is [30, 25], the initial formation angle is 0°, the target formation size is [60.50], the target formation angle is 60°, and the target moving platform position is [300, -250, -50]. The spacecraft formation is replanned using the PSO-SCP method, and the final generated trajectory is visualized to obtain the trajectory of each spacecraft and the moving platform in the formation. On the XY plane, the spacecraft in the lower left corner is designated as the lead spacecraft and numbered SC1. The spacecraft are numbered counter-clockwise. The final positions of the four spacecraft SC1 to SC4 are [286.794 -123.019 -50], [226.663 -226.871 -50], [313.206 -276.981 -50], [373.337 -173.129], respectively. -50], the formation size is [60.012, 50.012], the spacecraft formation angle is 59.9285°, within the allowable error range, the scale and angle information of multiple steps in the middle of the trajectory are visualized and analyzed, and the changes in the spacecraft formation reconstruction process are stable.

[0066] To further explain, step S2 includes the following steps: The assembly of each truss unit is determined according to the specifications of the truss to be assembled. For details, please refer to Figure 6 Taking an array of trusses as an example, the assembly of the array of trusses is divided into single truss unit assembly, horizontal truss unit group assembly, and vertical truss unit assembly. Each truss member is considered a connecting unit. Single truss unit assembly is carried out by assembling one connecting unit at a time, starting from the upper left corner and proceeding clockwise to obtain a single truss unit. Horizontal truss unit assembly is carried out based on an existing complete single truss unit. First, two directly installable connecting units are installed, and then the remaining connecting unit is installed. This process is repeated to complete the first row of horizontal truss assembly. Vertical truss unit assembly is applicable to the vertical truss assembly starting from the second row. The installation sequence is similar to that of the horizontal trusses. The two directly installable connecting units are installed first, and then the remaining connecting unit is installed. This process is repeated to complete the first column of vertical truss assembly. Starting from the second column, the vertical truss unit assembly of all columns is completed according to the vertical truss unit assembly sequence, generally from left to right and from front to back.

[0067] The position of the robotic arm's end effector during assembly is determined based on the assembly sequence of each truss unit. :

[0068] in, This represents the coordinates of the robotic arm's end effector along the X-axis in the global coordinate system. This represents the coordinates of the robotic arm's end effector along the Y-axis in the global coordinate system. Here are the coordinates of the robotic arm's end effector along the Z-axis in the global coordinate system; global coordinate system O Located at the center of the lead spacecraft; The yaw angle at the end of the robotic arm. The pitch angle at the end effector of the robotic arm. The roll angle at the end of the robotic arm; For details, please refer to Figure 7 During the assembly process, the assembly position and angle of each truss member are determined by the rigid-flexible coupling robot control unit. Therefore, by constructing a global coordinate system, the pose of the robotic arm end effector during each truss member gripping and assembly can be determined. .

[0069] The cable exit point of the flexible cable drive device is represented as follows: The anchor point of the flexible cable on the moving platform is represented as Flex vector Based on the inherent characteristics of the flexible cable, the direction of the cable tension vector is opposite to that of the cable vector, and its magnitude is the real-time tension of the cable; (Moving platform coordinate system) O m The relationship between the origin, located at the center of mass of the moving platform, and the anchor point is represented by the vector. r i The moving platform has two degrees of freedom, therefore its position is represented as... The coordinate system of the robotic arm base is O a0 The coordinate system of the end effector is O e Taking a robotic arm with 6 degrees of freedom as an example, the position of the robotic arm's center of mass is... P ai The speed at the center of mass of the robotic arm link The angular velocity at the center of mass is ω ai The position vector and Euler angles are used to represent the end effector pose of the robotic arm as a superposition of the angular velocities of all joints in the preceding stage. P e .

[0070] For further explanation, please refer to Figure 8 Step S3 includes the following steps: S10. Select the end-effector pose of a robotic arm during the assembly process as the current target pose of the robotic arm end-effector. ; S11. Set the robot's end-effector position Convergence threshold Robot end effector posture Convergence threshold Feasibility function of flexible cable tension threshold and the position of the robot's moving platform and the configuration of the robotic arm joints. ;

[0071] in, To determine the position of the moving platform in the global coordinate system, For the joint angle of the robotic arm; Let X be the coordinate value of the moving platform along the X-axis in the global coordinate system. This refers to the coordinates of the moving platform along the Y-axis in the global coordinate system. The first in the robotic arm The components of a joint angle; Specifically, the obtained end-effector pose trajectory is converted into the cable length and the joint angle of the robotic arm through inverse kinematics.

[0072] S12. Initialize the robot's moving platform position and robotic arm joint configuration. Let the number of iterations be... 1. Determine the number of iterations Does it meet the requirements? If yes, continue; if no, end. S13. Based on the current position of the robot's moving platform and the configuration of the robotic arm joints... Update the position of the global coordinate system of the moving platform. ; S14. Based on the current position of the global coordinate system of the moving platform And calculate the current end effector pose of the robotic arm by calculating the joint angles of the robotic arm joints. ; S15. Based on the position of the robotic arm's end effector Calculate the current target pose of the robotic arm's end effector. Position error and angle error ; S16. Based on position error and angle error The incremental values ​​of the robot's moving platform position and the manipulator joint configuration are calculated using the damped least squares method. :

[0073]

[0074] in, For the hybrid Jacobian matrix of the robot end effector, The damping factor, The error matrix consists of position error and angle error; For dynamic platform Jacobian matrix, For the Jacobian matrix of the robotic arm, Jacobi, the location of the moving platform The dynamic platform posture is comparable; Specifically, because the moving platform in the kinematic model of the rigid-flexible coupled space on-orbit assembly robot only has two translational degrees of freedom, therefore The value is 0; further, based on the velocity at the center of mass of the robotic arm link... Angular velocity at the center of mass of the robotic arm link ω ai Using the principle of superposition, solve for the mixed Jacobian matrix of the center-of-mass motion:

[0075] S17. Determine the number of iterations. If the set period has been reached, then perform tension optimization and feasibility assessment to obtain the optimized cable tension; otherwise, proceed to step S18. S18, According to the robot Incremental changes in platform position and robotic arm joint configuration Or, based on the optimized cable tension, let k+1 and update the current robot motion platform position and robotic arm joint configuration; S19. Obtain the current robot pose based on the updated moving platform position and robotic arm joint configuration, and calculate the pose relative to the current robotic arm end-effector target pose. Position error and angle error ; S20. Determine the updated position error. and attitude error Do they satisfy the following conditions simultaneously:

[0076]

[0077] in, For the robot end-effector position error, This refers to the robot's end-effector posture error. If so, then the current target pose of the robotic arm's end effector is obtained. The corresponding length of the robot cable and the angles of each joint of the robotic arm, such as Figure 9 , Figure 10 Figure 11 As shown, the corresponding flexible cable tension is obtained. Robotic arm joint torque With the joint angle of the robotic arm If not, then the current pose is considered to have no solution. Specifically, the dynamics of the robot are solved using the Lagrange method, based on the Lagrange function. We need to calculate the robot's total potential energy and total kinetic energy. The robot's total kinetic energy is expressed as:

[0078] Since the robot is in a microgravity state in the space environment, its gravitational potential energy is ignored, and the robot's total potential energy is expressed as:

[0079] in, The actual length of the flexible cable measured by the wire displacement sensor. The initial length of the flexible rope. This is the stiffness matrix of the flexible cable.

[0080] Substituting the values ​​into the Lagrangian function, we obtain the standard inverse dynamics model of the robot:

[0081] The format of the block matrix is:

[0082] in The calculation methods for each item are as follows:

[0083]

[0084]

[0085] This includes coupling terms between the cable-connected robot and the robotic arm, considering the coupling effects of their movements. To speed up dynamics calculations, the coupling portion of the Coriolis term is ignored. , All are 0.

[0086] The optimized cable tension is obtained by solving the QP tension optimization problem.

[0087] To further explain, obtaining the optimized cable tension through tension optimization and feasibility assessment includes the following steps: Based on the robot inverse dynamics model, and according to the current position of the moving platform and the configuration of the robotic arm joints... Calculate the current tension vector of the flexible cable. ; Calculate the degree of tension violation of the flexible cable :

[0088] If satisfied If the result is positive, then null space optimization is initiated to obtain the corrected cable tension; otherwise, the current tension vector is... Optimization was performed to obtain the optimized cable tension:

[0089]

[0090]

[0091] in, This is the weight matrix. Feasibility function for cable tension The threshold.

[0092] To further explain, by initiating zero-space optimization while maintaining the end-effector's posture, the system migrates from a high-tension configuration to a low-tension configuration, adjusting the internal configuration of the entire system and the position of the moving platform. The robotic arm's self-motion enables avoidance of singular configurations, reducing the robotic arm's influence on the moving platform's forces and achieving a tension gradient. Minimized zero-space optimization:

[0093] Specifically, the task of decomposing robot null space optimization can first be described as follows: , For the numerical changes in the position of the moving platform and the joint angles of the robotic arm, calculate the tension gradient and project it onto the null space. The influence of joint motion on mean tension is calculated using the priority difference method, and a search direction for tension minimization is constructed to generate null space corrections. Through weighting coefficients Controlling the optimization intensity ultimately generates the total joint increment. The correction step size is adaptively adjusted during the optimization process. To prevent oscillations and divergences during the correction process, the current optimal tension is recorded and updated to achieve a complete update of the configuration.

[0094] For further explanation, please refer to Figure 12 Step S4 includes the following steps: Trajectory planning is performed using an offline trajectory planner to generate the desired trajectory for the end effector, which includes a time series. The desired trajectory is sampled, and the end Cartesian space pose of each sampling point is converted into the position of the moving platform and the joint configuration of the robotic arm by a tension-optimized robot inverse kinematics solver, resulting in the desired position sequence of the moving platform, the desired tension sequence of the flexible cable, the desired joint angle sequence of the robotic arm, and the desired joint torque sequence. A force feedback PID controller for a cable-driven parallel robot is used to measure the difference between the desired cable tension and the actual cable tension. As the PID control input, the difference between the desired and actual cable lengths is used. As a feedforward input, a flexible cable length control signal is generated. :

[0095] in, , and All are PID parameters. For feedforward gain parameters; A cascaded PID controller is used for the robotic arm. The outer loop position controller takes the desired joint angle as input, compares it with the actual joint angle, and then generates the desired joint angular velocity through the position PID controller. The inner loop velocity controller takes the actual joint angular velocity as input, compares it with the actual joint angular velocity, and then outputs the basic joint torque through the velocity PID controller. The final control output is:

[0096] Through the coordinated control of the cable-driven parallel robot force feedback PID controller and the robotic arm cascade PID controller, the flexible cable system and the robotic arm are driven to move, so that the robot end effector reaches the pre-assembled posture.

[0097] Specifically, the actual tension of the flexible cable is acquired in real time by a tension sensor and used as the negative feedback quantity for the hybrid PID controller of the cable arm's coordinated movement force / position; the difference between the desired flexible cable length and the actual flexible cable length measured by the cable displacement sensor is used as feedforward to output the change in the length of the flexible cable; the desired joint angle of the robotic arm is used as the input of the cascade PID controller, and the current joint angle and joint speed of the robotic arm are obtained through the robotic arm angle encoder. The current joint angle is used as the first PID feedback and subtracted from the desired joint angle. The current joint speed is used as feedback for the second PID controller, and the difference between this and the output value of the first PID controller is used as the input for the second PID controller. The expected joint torque is summed with the PID output as feedforward to obtain the controller output. .

[0098] refer to Figure 13 To further explain, step S5 includes the following steps: The assembly unit image is acquired by the end-effector camera of the robotic arm, and the coarse alignment of the shaft and hole is achieved by using a 6D pose estimation algorithm. Activate the moving platform damping compensation controller, taking the moving platform position during coarse alignment as the desired position. According to the actual position of the moving platform Generate compensated position instructions and speed command :

[0099]

[0100] The robotic arm's fuzzy adaptive admittance controller is activated, based on the interaction force measured by the end effector force sensor. The deviation from the desired contact force is adjusted in real time by a fuzzy logic system to generate a reference trajectory for the robotic arm. :

[0101] in, This is the stiffness adjustment factor. As the inertia adjustment factor, This is the damping adjustment factor; The compensated position command and speed command and robotic arm reference trajectory Input the robot inverse dynamics model to calculate the optimized cable tension and robotic arm joint torque; A flexible cable tension PID controller is used to track the optimized flexible cable tension, and a robotic arm PID controller is used to track the optimized robotic arm joint torque, so as to achieve coordinated control of the moving platform's anti-interference stability and the robotic arm's compliant assembly. The contact stage and insertion stage are distinguished based on the characteristics of the contact force signal during the assembly process. The admittance control parameters are adaptively adjusted based on the fuzzy rule table to complete the fine alignment and insertion assembly of the shaft and hole.

[0102] The fuzzy rule table includes a contact phase fuzzy rule table and an insertion phase fuzzy rule table. The contact phase fuzzy rule table is shown in Table 1. Table 1. Fuzzy Rule Table for Contact Phase

[0103] The fuzzy rule table for the insertion phase is shown in Table 2: Table 2 Fuzzy Rule Table for Insertion Phase

[0104] The lower execution layer combines the reference trajectory and compensation instructions output by the upper planning and compensation layer with robot inverse dynamics calculations to output optimized cable tension and joint torque. These are then executed by the cable-parallel robot force feedback PID controller and the robotic arm cascade PID controller, respectively. This drives the robotic arm to complete the coarse and fine alignment of the truss connection units based on end-effector vision and force sensor information, and to perform assembly. The assembly process is divided into two stages based on the different end-effector force sensor signals: a contact stage and an insertion stage. The contact stage occurs when the axial force increases to a threshold, while the insertion stage occurs when the axial force stabilizes and the lateral force gradually decreases. The contact stage requires absorbing contact impact to achieve smooth contact, while the insertion stage requires compliant alignment and stable insertion. Different fuzzy control strategies are determined for the different force errors and robot speeds in these two scenarios.

[0105] This process is repeated until all truss units are assembled.

[0106] Example 2 This embodiment provides a reconfigurable rigid-flexible coupled spatial on-orbit assembly robot hierarchical control system, used to implement the reconfigurable rigid-flexible coupled spatial on-orbit assembly robot hierarchical control method provided in Embodiment 1, including: Spacecraft formation control system: The spacecraft formation system mission planning layer completes the replanning of the spacecraft formation through the PSO-SCP method, and realizes the replanning of the robot's working stroke based on the assembly mission requirements and the trajectory obtained from the replanning. The perception and communication layer enables master-slave communication between the spacecraft in the formation and can obtain the current position and attitude information of the spacecraft. The single-spacecraft drive layer enables formation reconfiguration between individual spacecraft according to a specified trajectory, allowing them to reach the designated operational position.

[0107] Rigid-flexible coupling robot hierarchical control system: The robot sensing layer perceives real-time information about the robot itself and its environment. The rigid-flexible coupled robot task planning layer confirms the pre-assembly pose and task objectives of each robot gantry unit. The robot control layer performs real-time calculations of robot kinematics and dynamics, as well as controller data; it controls the coordinated movement of the moving platform and the robotic arm to grasp the truss unit to the pre-assembly pose through a cable-arm cooperative motion force / position hybrid PID controller; and it controls the moving platform to maintain stability through a moving platform anti-interference - robotic arm assembly force / position hybrid controller. The robot drive layer inputs decoupled control quantities to the robotic arm drive and the cable-connected parallel robot drive for hierarchical control to complete the assembly.

[0108] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0109] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hierarchical control method for a reconfigurable rigid-flexible coupled on-orbit assembly robot, characterized in that, Includes the following steps: S1. Based on the target location and operational requirements, the spacecraft formation is replanned using the PSO-SCP method to generate a reconstructed trajectory. The spacecraft formation then completes the formation change and reaches the designated location. S2. Based on the specifications of the truss to be assembled, determine the assembly sequence of the truss units and the pre-assembly end pose of the rigid-flexible coupling robot when assembling each truss unit. S3. Determine the position of the moving platform and the configuration of the robotic arm joints based on the pre-assembled end-effector pose of the rigid-flexible coupling robot. S4. Determine the robot's kinematics and dynamics model based on the robot's current configuration data. Drive the moving platform through the flexible cable and use a cable-arm cooperative movement force / position hybrid PID controller to control the robot arm to adjust the end pose to the robot's pre-assembled posture by combining the moving platform position and the robot arm joint configuration. S5. A dynamic platform anti-interference - robotic arm assembly force / position hybrid controller is used to keep the dynamic platform stable until the robotic arm completes the assembly of a single truss unit; S6. Repeat steps S4 and S5 until all truss units are assembled.

2. The hierarchical control method for a reconfigurable rigid-flexible coupled on-orbit assembly robot according to claim 1, characterized in that, Step S1 includes the following steps: Obtain initial parameters for spacecraft formation: initial position Initial scale of spacecraft formation and the initial angle of the spacecraft formation ; Determine spacecraft formation target parameters: target position Target Scale and target angle ; Based on the initial parameters and target parameters of the spacecraft formation, a hierarchical optimization algorithm combining particle swarm optimization and sequential convex optimization is adopted to solve the spacecraft formation trajectory planning under the constraints of Clohessy-Wiltshire equation dynamics, spacecraft collision avoidance constraints, and cable length constraints with relaxation variables. Adjust the spacecraft formation based on the solved spacecraft formation trajectory plan.

3. The hierarchical control method for a reconfigurable rigid-flexible coupled on-orbit assembly robot according to claim 2, characterized in that, The optimization algorithm, which combines particle swarm optimization and sequential convex optimization, based on the initial and target parameters of the spacecraft formation, solves the spacecraft formation trajectory planning problem under the constraints of the Clohessy-Wiltshire equations, spacecraft collision avoidance constraints, and cable length constraints with relaxation variables. The steps include: Construct the objective function for spacecraft formation trajectory planning: in, For spacecraft formation fuel consumption, For discretized time periods, For the long walk, For the first One spacecraft, The total number of spacecraft in the spacecraft formation. For positional weights, For the position error of the moving platform terminal, For scale weights, For spacecraft formation scale error, For angle weighting, This refers to the spacecraft formation angle error term. for Time of the first The motion state of a spacecraft The system state matrix in the Clohessy-Wiltshire equations is... This is the control input matrix in the Clohessy-Wiltshire equation; For the rotation matrix of spacecraft formation, Let be the reference basis vector for the motion of the moving platform; The length of the flexible rope, As slack variables, The minimum safe distance between spacecraft This is the maximum thrust of the spacecraft.

4. The hierarchical control method for a reconfigurable rigid-flexible coupled on-orbit assembly robot according to claim 3, characterized in that, Step S2 includes the following steps: The assembly of each truss unit is determined according to the specifications of the truss to be assembled. The position of the robotic arm's end effector during assembly is determined based on the assembly sequence of each truss unit. : in, This represents the coordinates of the robotic arm's end effector along the X-axis in the global coordinate system. This represents the coordinates of the robotic arm's end effector along the Y-axis in the global coordinate system. This refers to the coordinates of the robotic arm's end effector along the Z-axis in the global coordinate system; the global coordinate system... O Located at the center of the lead spacecraft; The yaw angle at the end of the robotic arm. The pitch angle at the end effector of the robotic arm. This is the roll angle at the end of the robotic arm.

5. The reconfigurable rigid-flexible coupled spatial on-orbit assembly robot hierarchical control method according to claim 4, characterized in that, Step S3 includes the following steps: S10. Select the end-effector pose of a robotic arm during the assembly process as the current target pose of the robotic arm end-effector. ; S11. Set the robot's end-effector position Convergence threshold Robot end effector posture Convergence threshold Feasibility function of flexible cable tension threshold and the position of the robot's moving platform and the configuration of the robotic arm joints. ; in, To determine the position of the moving platform in the global coordinate system, For the joint angle of the robotic arm; Let X be the coordinate value of the moving platform along the X-axis in the global coordinate system. This refers to the coordinates of the moving platform along the Y-axis in the global coordinate system. The first in the robotic arm The components of a joint angle; S12. Initialize the robot's moving platform position and robotic arm joint configuration. Let the number of iterations be...

1. Determine the number of iterations Does it meet the requirements? If yes, continue; if no, end. S13. Based on the current position of the robot's moving platform and the configuration of the robotic arm joints... Update the position of the global coordinate system of the moving platform. ; S14. Based on the current position of the global coordinate system of the moving platform Calculate the current pose of the robotic arm's end effector ; S15. Based on the position of the robotic arm's end effector Calculate the current target pose of the robotic arm's end effector. Position error and angle error ; S16. Based on position error and angle error The incremental values ​​of the robot's moving platform position and the manipulator joint configuration are calculated using the damped least squares method. : in, For the hybrid Jacobian matrix of the robot end effector, The damping factor, The error matrix consists of position error and angle error; For dynamic platform Jacobian matrix, For the Jacobian matrix of the robotic arm, Jacobi, the location of the moving platform The dynamic platform posture is comparable; S17. Determine the number of iterations. If the set period has been reached, then perform tension optimization and feasibility assessment to obtain the optimized cable tension; otherwise, proceed to step S18. S18. Increment based on the position of the robot's moving platform and the configuration of the robotic arm joints. Or, based on the optimized cable tension, let k+1 and update the current robot motion platform position and robotic arm joint configuration; S19. Obtain the current robot pose based on the updated moving platform position and robotic arm joint configuration, and calculate the pose relative to the current robotic arm end-effector target pose. Position error and angle error ; S20. Determine the updated position error. and attitude error Do they satisfy the following conditions simultaneously: in, For the robot end-effector position error, This refers to the robot's end-effector posture error. If so, then the current target pose of the robotic arm's end effector is obtained. The corresponding robot cable length and the angles of each joint of the robotic arm are determined; otherwise, the current pose is considered unsolvable.

6. The hierarchical control method for a reconfigurable rigid-flexible coupled on-orbit assembly robot according to claim 5, characterized in that, The process of optimizing the tension and conducting a feasibility assessment to obtain the optimized cable tension includes the following steps: Based on the robot inverse dynamics model, and according to the current position of the moving platform and the configuration of the robotic arm joints... Calculate the current tension vector of the flexible cable. ; Calculate the feasible violation of cable tension : If satisfied If the result is positive, then null space optimization is initiated to obtain the corrected cable tension; otherwise, the current tension vector is... Optimization was performed to obtain the optimized cable tension: in, This is the weight matrix. Feasibility function for cable tension The threshold.

7. The hierarchical control method for a reconfigurable rigid-flexible coupled on-orbit assembly robot according to claim 6, characterized in that, Step S4 includes the following steps: Trajectory planning is performed using an offline trajectory planner to generate the desired trajectory for the end effector, which includes a time series. The desired trajectory is sampled, and the end Cartesian space pose of each sampling point is converted into the position of the moving platform and the joint configuration of the robotic arm by a tension-optimized robot inverse kinematics solver, resulting in the desired position sequence of the moving platform, the desired tension sequence of the flexible cable, the desired joint angle sequence of the robotic arm, and the desired joint torque sequence. A force feedback PID controller for a cable-driven parallel robot is used to measure the difference between the desired cable tension and the actual cable tension. As the PID control input, the difference between the desired and actual cable lengths is used. As a feedforward input, a flexible cable length control signal is generated. : in, , and All are PID parameters. For feedforward gain parameters; A cascaded PID controller is used for the robotic arm. The outer loop position controller takes the desired joint angle as input, compares it with the actual joint angle, and then generates the desired joint angular velocity through the position PID controller. The inner loop velocity controller takes the actual joint angular velocity as input, compares it with the actual joint angular velocity, and then outputs the basic joint torque through the velocity PID controller. The final control output is: Through the coordinated control of the cable-driven parallel robot force feedback PID controller and the robotic arm cascade PID controller, the flexible cable system and the robotic arm are driven to move, so that the robot end effector reaches the pre-assembled posture.

8. The hierarchical control method for a reconfigurable rigid-flexible coupled on-orbit assembly robot according to claim 7, characterized in that, Step S5 includes the following steps: The assembly unit image is acquired by the end-effector camera of the robotic arm, and the coarse alignment of the shaft and hole is achieved by using a 6D pose estimation algorithm. Activate the moving platform damping compensation controller, taking the moving platform position during coarse alignment as the desired position. According to the actual position of the moving platform Generate compensated position instructions and speed command : The robotic arm's fuzzy adaptive admittance controller is activated, based on the interaction force measured by the end effector force sensor. The deviation from the desired contact force is adjusted in real time by a fuzzy logic system to generate a reference trajectory for the robotic arm. : in, This is the stiffness adjustment factor. As the inertia adjustment factor, This is the damping adjustment factor; The compensated position command and speed command and robotic arm reference trajectory Input the robot inverse dynamics model to calculate the optimized cable tension and robotic arm joint torque; A flexible cable tension PID controller is used to track the optimized flexible cable tension, and a robotic arm PID controller is used to track the optimized robotic arm joint torque, so as to achieve coordinated control of the moving platform's anti-interference stability and the robotic arm's compliant assembly. The contact stage and insertion stage are distinguished based on the characteristics of the contact force signal during the assembly process. The admittance control parameters are adaptively adjusted based on the fuzzy rule table to complete the fine alignment and insertion assembly of the shaft and hole.

9. The hierarchical control method for a reconfigurable rigid-flexible coupled on-orbit assembly robot according to claim 8, characterized in that, The fuzzy adaptive admittance controller model for the robotic arm is as follows: in, , and Mean admittance parameter.

10. A reconfigurable rigid-flexible coupled spatial on-orbit assembly robot hierarchical control system, characterized in that, The hierarchical control method for the reconfigurable rigid-flexible coupled space on-orbit assembly robot according to any one of claims 1 to 9 includes: Spacecraft formation control system: The spacecraft formation system mission planning layer completes the replanning of the spacecraft formation through the PSO-SCP method, and realizes the replanning of the robot's working stroke based on the assembly mission requirements and the trajectory obtained from the replanning. The perception and communication layer enables master-slave communication between the spacecraft in the formation and can obtain the current position and attitude information of the spacecraft. The single-spacecraft propulsion layer enables formation reconfiguration between individual spacecraft according to a specified trajectory, allowing them to reach the designated operational location. Rigid-flexible coupling robot hierarchical control system: The robot sensing layer perceives real-time information about the robot itself and its environment. The rigid-flexible coupled robot task planning layer confirms the pre-assembly pose of each robot gantry unit and the current task objective. The robot control layer performs real-time calculations of robot kinematics and dynamics, as well as controller data; it controls the coordinated movement of the moving platform and the robotic arm to grasp the truss unit to the pre-assembly pose through a cable-arm cooperative motion force / position hybrid PID controller; and it controls the moving platform to maintain stability through a moving platform anti-interference - robotic arm assembly force / position hybrid controller. The robot drive layer inputs decoupled control quantities to the robotic arm drive and the cable-connected parallel robot drive for hierarchical control to complete the assembly.

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