On-orbit control method based on butt joint of mechanical arm and electromagnetism

Abstract

The invention discloses an on-orbit control method based on butt joint of a mechanical arm and an electromagnet, which comprises the following steps: acquiring an initial pose of a target spacecraft through a sensor, and planning a motion track of the mechanical arm; when the tail end of the mechanical arm is close to a target by a preset distance, an electromagnetic docking module is activated to apply non-contact adsorption force to the surface of the target; a cascade force / position hybrid control algorithm is adopted to adjust the pose of the tail end of the mechanical arm, so that the electromagnetic butt joint surface is aligned with the target contact point; when the butt joint face error is smaller than a threshold value, the electromagnetic module is switched to a rigid locking mode, and rigid connection between the mechanical arm and the target is completed; and executing a task through the mechanical arm, and releasing electromagnetic locking and separating after the task is completed. The active electromagnetic module is integrated at the tail end of the mechanical arm, flexible adsorption and high-precision rigid docking of a non-cooperative target are achieved in combination with a multi-mode sensing and cascade predictive control algorithm, and the robot has the advantages of being high in docking efficiency, low in energy consumption and high in adaptability and is suitable for on-orbit service tasks in a complex space environment.

Description

Technical Field

[0001] The present invention relates to the field of spacecraft on-orbit servicing technology, and in particular to an autonomous on-orbit control method that combines high-precision control of a robotic arm with electromagnetic docking, which is suitable for space station maintenance, failed satellite capture, and deep space exploration missions. Background Art

[0002] In recent years, with the increasing complexity of spacecraft on-orbit service needs, the limitations of traditional mechanical docking and capture technologies have gradually become apparent. Existing solutions mainly rely on rigid locking mechanisms, which are difficult to meet the control requirements of highly dynamic and non-cooperative targets.

[0003] At present, the traditional docking method has the problem that the rigid locking mechanism can easily cause damage to the target. Taking the robotic arm of the International Space Station as an example, its claw-type rigid locking mechanism requires hard contact with the preset interface of the target. Under space disturbances in a microgravity environment, the contact force can easily exceed the limit instantaneously, causing surface wear and even structural damage to the target. The existing method requires frequent adjustment of the orbit and attitude of the spacecraft through thrusters during capture, which consumes a lot of fuel and makes the capture of non-cooperative targets high. There is also the problem of insufficient adaptability of the robotic arm system. The existing robotic arm-adapter system requires the target to have a standardized interface, while failed satellites or special-shaped debris often have no adaptive structure, making capture difficult.

[0004] Therefore, an on-orbit control method based on the coordination of a robotic arm and electromagnetic docking can be adopted. Non-contact operation can be achieved by combining rapid electromagnetic guidance with precise mechanical operation, thereby reducing collision risks and propellant consumption. At the same time, it is applicable to various complex scenarios, such as the capture of non-cooperative targets and heterogeneous debris. The present invention has the advantages of high docking efficiency, low energy consumption, strong adaptability and a wide range of applications, providing a highly reliable and low-risk solution for future complex on-orbit services. Summary of the Invention

[0005] In view of this, the present invention provides an on-orbit control method based on a robotic arm and electromagnetic docking. By integrating an active electromagnetic docking module at the end of the robotic arm, combined with multimodal perception and cascaded force / position hybrid control algorithm, a system solution for flexible adsorption and high-precision rigid docking of non-cooperative targets is achieved.

[0006] The object of the present invention is achieved like this:

[0007] S1, obtain the initial position of the target spacecraft through the visual sensor and laser rangefinder, and plan the motion trajectory of the robotic arm;

[0008] S2. When the end of the robotic arm approaches the target to a preset distance, the electromagnetic docking module is activated to generate a gradient magnetic field, exerting a non-contact adsorption force on the target surface;

[0009] S3. Based on the force sensor feedback and magnetic field strength data, a cascaded force / position hybrid control algorithm is used to adjust the end-arm posture so that the electromagnetic docking surface is aligned with the target contact point.

[0010] S4. When the docking surface error is less than the threshold, the electromagnetic module is switched to the rigid locking mode to complete the rigid connection between the manipulator and the target;

[0011] S5. Perform load transfer or equipment maintenance operations through the robotic arm. After the task is completed, release the electromagnetic lock and separate.

[0012] The core component of step S2, the electromagnetic docking module, is a coaxial annular electromagnetic coil installed at the end, which is composed of a high-density copper winding and an iron-cobalt alloy core. The electromagnetic docking module generates a directional gradient magnetic field by independently regulating the current intensity of each coil. The dynamic regulation of the magnetic field intensity can adapt to various needs, and the PID control algorithm ensures that the dynamic regulation accuracy of the adsorption force meets the requirements.

[0013] In step S3, the visual prediction controller (SVPC) first predicts the target pose based on the target feature points identified by the binocular vision camera, based on the EPnP algorithm and combined with the laser rangefinder data; constructs the robot arm kinematic state space equation, solves and optimizes the robot arm joint angular velocity by inverse kinematics, and enables the robot arm to quickly approach the target; then the force prediction controller (FPC) receives data obtained from the six-dimensional force sensor and the Hall effect magnetometer, and based on the contact force error model, solves the optimal control quantity by quadratic programming to dynamically correct the end pose, ensure that the electromagnetic docking surface is aligned with the target contact point, and ensure that the dynamic constraints are met; based on the Hall effect magnetometer data and the current joint angle, the electromagnetic contact force deviation is compensated by the magnetic field-mechanical coupling compensation model;

[0014] The advantages of the present invention are:

[0015] Compared with traditional technologies, the advantages of the present invention are that it integrates an active electromagnetic docking mechanism at the end of the robotic arm to achieve dual-mode switching between contactless flexible adsorption and rigid locking, effectively avoiding the problem of rigid collision of the robotic arm; it integrates visual-force-electromagnetic multimodal perception and cascaded force / position hybrid control algorithm, and uses a magnetic field-mechanical coupling compensation model to reduce fuel consumption and thermal effects during the docking process; it can still achieve capture and docking for non-cooperative targets, failed satellites, etc. that do not have standardized interfaces, and has a wider range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart of an on-orbit control method based on a robotic arm and electromagnetic docking provided by the present invention;

[0017] Figure 2 Schematic diagram of the coil array layout and magnetic field distribution of the electromagnetic docking module;

[0018] Figure 3 Schematic diagram of redundant fault recovery mechanism;

[0019] Figure 4 This is a multi-stage docking process and control logic block diagram. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0021] Combine Figure 1 To illustrate this embodiment, an on-orbit control method based on a robotic arm and electromagnetic docking includes the following steps:

[0022] S1, obtain the initial position of the target spacecraft through the visual sensor and laser rangefinder, and plan the motion trajectory of the robotic arm;

[0023] S2. When the end of the robotic arm approaches the target to a preset distance, the electromagnetic docking module is activated to generate a gradient magnetic field, exerting a non-contact adsorption force on the target surface;

[0024] S3. Based on the force sensor feedback and magnetic field strength data, a cascaded force / position hybrid control algorithm is used to adjust the end-arm posture so that the electromagnetic docking surface is aligned with the target contact point.

[0025] S4. When the docking surface error is less than the threshold, the electromagnetic module is switched to the rigid locking mode to complete the rigid connection between the manipulator and the target;

[0026] S5. Perform load transfer or equipment maintenance operations through the robotic arm. After the task is completed, release the electromagnetic lock and separate.

[0027] In step S1, the initial position of the target spacecraft is obtained by using a visual sensor and a laser rangefinder, and the motion trajectory of the robotic arm is planned. The specific process is as follows:

[0028] The visual sensor (binocular camera) acquires image data of the target spacecraft, extracts the QR code or feature points on the target surface, and uses the SURF algorithm to match the feature points based on a pre-stored 3D model of the target. The EPnP algorithm uses the matched feature points to calculate the position and attitude of the target spacecraft relative to the visual sensor, synchronously integrating the precise relative distance provided by the laser rangefinder to compensate for the error of the visual sensor. The robot arm's motion trajectory is solved through inverse kinematics.

[0029] The robotic arm body adopts a 7-degree-of-freedom redundant configuration, and the joint drive module integrates a harmonic reducer and a torque sensor. The closed-loop PID control can achieve end-point repeatability accuracy to meet certain requirements.

[0030] In step S2, when the end of the robotic arm approaches the target to a preset distance, the electromagnetic docking module is activated to generate a gradient magnetic field to apply a non-contact adsorption force to the target surface; the specific process is as follows:

[0031] The electromagnetic docking module includes an array of coaxial annular electromagnetic coils. By independently controlling the current intensity of each coil and superimposing its magnetic field distribution, a directional gradient magnetic field is generated. The dynamic control range of the magnetic field intensity can adapt to the needs from weak adsorption to rigid locking. During operation, the magnetic field strength is dynamically adjusted based on the relative distance between the end of the robotic arm and the target, and the electromagnetic force is activated when the target enters the adsorption range. A PID controller is used to compensate for external disturbances and maintain adsorption stability, ensuring that the dynamic adjustment accuracy of the adsorption force meets the requirements.

[0032] The core component electromagnetic docking module: a coaxial annular electromagnetic coil is installed at the end, which is composed of a high-density copper winding and an iron-cobalt alloy core.

[0033] In step S3, based on the force sensor feedback and the magnetic field strength data, a cascaded force / position hybrid control algorithm is used to adjust the end-arm posture so that the electromagnetic docking surface is aligned with the target contact point. The specific process is as follows:

[0034] The visual prediction controller (SVPC) first predicts the target pose based on the target feature points identified by the binocular vision camera, using the EPnP algorithm and combined with laser rangefinder data. It then constructs the robot's kinematic state-space equations, solves and optimizes the robot's joint angular velocities using inverse kinematics, and enables the robot to quickly approach the target. Next, the force prediction controller (FPC) receives data from the six-dimensional force sensor and Hall effect magnetometer. Based on the contact force error model, it uses quadratic programming to solve the optimal control variable to dynamically correct the end-point pose, ensuring that the electromagnetic docking surface is aligned with the target contact point and that dynamic constraints are met. Based on the Hall effect magnetometer data and the current joint angle, the electromagnetic contact force deviation is compensated using a magnetic field-mechanical coupling compensation model.

[0035] The cascaded force / position hybrid control algorithm includes: a visual predictive controller (SVPC) constructs a state-space equation based on the target feature point recognition results to optimize the angular velocity of the manipulator joint; a force predictive controller (FPC) corrects the manipulator end position according to the contact force error model to meet the dynamic constraints;

[0036] The multimodal sensing unit includes: a binocular vision camera, a six-dimensional force sensor and a Hall effect magnetometer;

[0037] The contact force error dynamics model is:

[0038]

[0039] Among them, M C 、C C , K C are the inertia, damping and stiffness matrices respectively, x is the end pose deviation, and the optimal joint torque is solved by quadratic programming (QP);

[0040] The magnetic field-mechanical coupling compensation model is:

[0041] F em =K m ·B 2 ·J -T (q d -q)

[0042] Among them, F em is the electromagnetic compensation force, K m is the magnetic-mechanical coupling coefficient, B is the magnetic field strength, J is the Jacobian matrix of the manipulator, q d and q are the expected and actual joint angles.

[0043] In step S4, when the interface error is less than the threshold, the electromagnetic module is switched to the rigid locking mode to complete the rigid connection between the manipulator and the target. The specific process is as follows:

[0044] The multimodal sensing unit monitors the position error of the docking surface in real time. When the error is less than the set threshold, the electromagnetic docking module is triggered to generate a high-intensity gradient magnetic field. The six-dimensional force sensor verifies the stability of the adsorption force to ensure that the target surface fits the electromagnetic docking surface, and mechanical locking is involved to achieve a rigid connection. When the electromagnetic locking fails, the redundant gripper at the end of the robotic arm deploys, and based on vision and force feedback, the gripper position is adjusted to grasp the target structure. In addition, a suspended damping mechanism is set at the end of the robotic arm to absorb the docking impact energy, and the damping coefficient is dynamically selected within an adjustable range.

[0045] In step S5, the load transfer or equipment maintenance operation is performed by the robotic arm, and the electromagnetic lock is released and separated after the task is completed. The specific process is:

[0046] After the on-orbit service mission is completed, the complete unlocking is confirmed by gradually attenuating the magnetic field strength, releasing the mechanical clips, and detecting the force sensors; the separation path of the robotic arm is planned using inverse kinematics calculations to ensure the safety and reliability of the entire process.

[0047] Combine Figure 2 The coil array layout and magnetic field distribution of the electromagnetic docking module are as follows:

[0048] The electromagnetic docking module is equipped with a coaxial annular electromagnetic coil at the end, which is composed of a high-density copper winding and an iron-cobalt alloy core. By independently adjusting the current intensity of each coil and superimposing its magnetic field distribution, a directional gradient magnetic field is generated. The magnetic field intensity can be dynamically adjusted, and the dynamic adjustment accuracy of the adsorption force meets certain requirements.

[0049] The coil of the electromagnetic docking module is mostly wound around the magnetic core in a high-density manner, and the gap is negligible. The outer ring coil can be approximated as a hollow cylinder. Figure 2 (b) The middle cylinder is an iron-cobalt alloy core, and the outer hollow cylinder is a high-density copper winding;

[0050] The coil array distribution is to perform an array operation on a single coil, and the spacing and shape between the array and the individual coils in the array can be adjusted; the current, number of turns and position of each coil are optimized to make the magnetic field generated by the coil array as close as possible to the target magnetic field; the coupling effect between the coil arrays can be solved by optimizing the coil distribution or adopting appropriate shielding measures; Figure 2 (c) and (b) are two possible coil arrays.

[0051] Combine Figure 3 , a schematic diagram of the redundant fault recovery mechanism, comprising an electromagnetic docking module (1), a suspended damping mechanism (2), a redundant mechanical claw (3), a 7-DOF redundant configuration mechanical arm (4), and a target (5);

[0052] The electromagnetic docking module (1) is installed at the end of a 7-DOF redundant configuration manipulator (4), and generates a directional gradient magnetic field by independently regulating the current intensity of each coil; the suspended damping mechanism (2) is installed between the redundant manipulator claw (3) and the manipulator arm (4), and can absorb impact energy during docking; the redundant manipulator claw (3) is deployed to grasp the target structure when electromagnetic locking fails; the specific process is as follows:

[0053] Based on the target's structural characteristics and task requirements, either a robotic claw or an electromagnetic docking module is dynamically selected to capture the target, or the two can work together as needed. First, a binocular vision camera, magnetometer, etc. are used to identify the target's surface features to detect whether it is a magnetic material and whether the surface is sufficiently rough. Based on the target's characteristics, the XGBoost algorithm is used to select the actuator mode. For example, a robotic claw can grasp non-magnetic rough targets, while the electromagnetic docking mode is suitable when the target material is ferromagnetic and the surface is flat and smooth. When choosing a collaborative working mode, the electromagnetic docking module can be used to initially adsorb the target and suppress its movement, the robotic claw can be deployed to grasp the target, or the robotic claw can actively grasp the target and the electromagnetic docking device can assist in alignment, among other collaborative methods.

[0054] The redundant fault recovery mechanism means that when the electromagnetic locking of the target (5) fails, the redundant mechanical claw (3) is quickly deployed at the end of the robotic arm (4), and a dynamic obstacle avoidance grasping path is generated based on vision and force feedback using a DWA (Dynamic Window Approach) algorithm; in addition, a suspended damping mechanism (2) is set at the end of the robotic arm (4) to absorb the docking impact energy, and its damping coefficient is adjustable within a range.

[0055] Combine Figure 4 The multi-stage docking process and control logic block diagram include the following steps:

[0056] The perception layer described includes target pose acquisition and path planning, as well as determining whether the target enters the adsorption range. The specific process is as follows:

[0057] The binocular vision camera extracts the QR code or feature points on the target surface and matches the feature points using the SURF algorithm. The target spacecraft pose is calculated based on the EPnP algorithm, while the laser rangefinder simultaneously provides the precise relative distance. The robotic arm's motion trajectory is solved using inverse kinematics. The precise relative distance provided by the laser rangefinder is used to determine whether the target has entered the adsorption range. If the target has entered the preset distance, the next stage—the execution layer—is entered. If the target has not entered the preset distance, the target pose is repeatedly acquired and the robotic arm path is planned until the target enters the adsorption range.

[0058] The execution layer described includes activating the electromagnetic docking module, using a cascaded force / position hybrid control algorithm to adjust the end-arm posture and align the docking surface with the target contact point, and determining whether the docking surface posture error is less than a threshold. The specific process is as follows:

[0059] The electromagnetic docking module dynamically adjusts the magnetic field strength based on the relative distance between the end of the robotic arm and the target, and activates the electromagnetic force when the target enters the adsorption range; a cascaded force / position hybrid control algorithm is used to adjust the end posture of the robotic arm: the visual prediction controller (SVPC) predicts the target posture, solves and optimizes the robotic arm joint angular velocity, and enables the robotic arm to quickly approach the target; the force prediction controller (FPC) aligns the electromagnetic docking surface with the target contact point based on the contact force error model, while ensuring that the dynamic constraints are met; the electromagnetic contact force deviation is compensated by the magnetic field-mechanical coupling compensation model, and the adsorption stability is maintained by the PID controller; the docking surface posture error is measured in real time by the multimodal perception unit. When the error is less than the set threshold, the electromagnetic docking module generates a high-intensity gradient magnetic field to ensure that the docking surface is adsorbed and mechanical locking is intervened. If the error does not meet the conditions, the end posture of the robotic arm is repeatedly adjusted until the error judgment conditions are met.

[0060] The fault tolerance layer described includes determining whether the lock is successful; the specific contents are as follows:

[0061] After determining that the locking is successful, the task is executed. After the task is completed, the magnetic field strength is gradually attenuated and the mechanical clip is released to achieve safe unlocking and separation. When the electromagnetic locking fails, the redundant gripper at the end of the robotic arm is deployed, and the gripper position is adjusted based on vision and force feedback to grasp the target structure.

[0062] The present invention is described in detail through specific embodiments. It should be understood that the specific embodiments are only for illustrating the present invention, rather than for limiting the scope of protection of the present invention.

[0063] This embodiment is described in conjunction with the specific embodiment 1 of the space station module docking. An on-orbit control method based on a robotic arm and electromagnetic docking includes the following steps:

[0064] S1. The robotic arm moves from its parking position to a certain range within the target compartment, and the visual system identifies the docking ring feature points.

[0065] S2. When the distance is less than the threshold, the electromagnetic module is activated to generate a gradient magnetic field of sufficient strength to gradually attract the cabin to a centimeter-level distance;

[0066] S3, the force sensor detects the contact force fluctuation and adjusts the posture of the end of the robot arm so that the normal error of the docking surface is less than the threshold;

[0067] S4. The electromagnetic module is powered on and locked, and the robotic arm switches to high-rigidity mode to complete the cabin transfer.

[0068] In step S1, the robotic arm moves from the parking position to a certain range of the target compartment, and the visual system identifies the docking ring feature points; the specific process is as follows:

[0069] After determining the approximate orientation of the target compartment, the DWA algorithm is used to generate a collision-free path from the manipulator arm to the target compartment within a certain range. Based on the inverse kinematics model of the 7-DOF redundant manipulator, the pseudo-inverse method is used to solve the joint angular velocity. The preset QR code of the docking ring is identified by the visual system. For compartments without preset identification, SURF feature matching is performed, and the position and posture of the target compartment are solved based on the EPnP algorithm.

[0070] In step S2, when the distance is less than a threshold, the electromagnetic module is activated to generate a gradient magnetic field of sufficient strength to gradually attract the cabin to a centimeter-level distance. The specific process is as follows:

[0071] When the laser radar detects that the target distance is less than the threshold, it triggers the gradient magnetic field of sufficient intensity in the electromagnetic docking module. Based on the real-time feedback of the relative distance from the laser radar, PID control is used to ensure the stability of the adsorption process.

[0072] In step S3, the force sensor detects contact force fluctuations and adjusts the posture of the end of the robotic arm so that the normal error of the docking surface is less than a threshold. The specific process is as follows:

[0073] The six-dimensional force sensor collects real-time data, adopts the cascade force / position hybrid control algorithm to adjust the end-arm posture, and the binocular vision camera monitors the normal vector direction of the docking ring to ensure that the target is aligned with the coordinate system of the end-arm.

[0074] In step S4, the electromagnetic module is powered on and locked, and the robotic arm switches to high-rigidity mode to complete the cabin transfer. The specific process is as follows:

[0075] Activate the electromagnetic locking mode, enhance the magnetic field strength to generate rigid adsorption force, and insert the mechanical buckle to complete the locking; adjust the impedance parameters of each joint of the robotic arm and switch to the high stiffness mode; use polynomial interpolation to generate a smooth transfer path and execute the cabin transfer.

[0076] In conjunction with the specific embodiment 2 of the failed satellite capture, this embodiment is described. An on-orbit control method based on a robotic arm and electromagnetic docking includes the following steps:

[0077] S1. Perform laser scanning modeling on the failed satellite and plan the obstacle avoidance path of the robotic arm;

[0078] S2. Activate electromagnetic adsorption in the area without a preset interface on the satellite surface, maintaining the adsorption force at 10N;

[0079] S3, eliminate satellite spin disturbances through impedance control and finally lock to the end of the robotic arm;

[0080] S4: Drag the satellite to the deorbit orbit and then release it.

[0081] Step S1 performs laser scanning modeling on the failed satellite and plans the obstacle avoidance path of the robotic arm. The specific process is as follows:

[0082] A laser radar is used to perform an all-round scan of the failed satellite, and a binocular vision camera is used to identify and locate the target based on the obtained target feature points. A three-dimensional model of the target is generated based on the ICP algorithm and the pre-stored satellite model. The DWA algorithm is used to plan the obstacle avoidance path of the robotic arm to ensure that the end avoids sensitive areas.

[0083] The step S2 activates electromagnetic adsorption in the area without a preset interface on the satellite surface, and the adsorption force is maintained at 10N. The specific process is:

[0084] When the end of the robotic arm approaches the centimeter-level distance from the satellite surface, the electromagnetic docking module is activated, and a gradient magnetic field of a certain intensity applies a non-contact adsorption force to the satellite surface structure without relying on a preset interface. A PID controller is used to dynamically adjust the coil current, reducing the posture error through magnetic field posture coupling.

[0085] Step S3 eliminates satellite spin disturbances through impedance control and finally locks to the end of the robotic arm; the specific process is:

[0086] The satellite's spin angular velocity is detected by gyroscopes and visual sensors, and dynamic modeling is performed considering multi-source disturbances. The satellite's spin disturbances are offset by an impedance control model. When the spin angular velocity drops to almost zero, the electromagnetic-mechanical locking is triggered, and the satellite is eventually locked to the end of the robotic arm.

[0087] The step S4 drags the satellite to the deorbit orbit and then releases it. The specific process is:

[0088] The optimal dragging path of the robotic arm is calculated, and the robotic arm drags the target to the deorbit height according to the predetermined orbit; after confirming that the target orbit point is correct, the magnetic field strength is slowly attenuated to achieve safe separation of the robotic arm from the failed satellite.

[0089] This embodiment achieves dynamic capture of non-cooperative targets, breaking the traditional robotic arm's reliance on pre-set interfaces and demonstrating the invention's broader applicability. Verification has shown that the invention significantly improves docking success rates and reduces docking energy consumption; it can also capture non-cooperative targets (such as inoperable satellites without pre-set interfaces).

[0090] Specific embodiments are used in the present invention to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

[0091] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the present invention.

Claims

1. An on-orbit control method based on a robotic arm and electromagnetic docking, characterized in that: The method comprises the following steps: S1, obtain the initial position of the target spacecraft through the visual sensor and laser rangefinder, and plan the motion trajectory of the robotic arm; S2. When the end of the robotic arm approaches the target to a preset distance, the electromagnetic docking module is activated to generate a gradient magnetic field, exerting a non-contact adsorption force on the target surface; S3. Based on the force sensor feedback and magnetic field strength data, a cascaded force / position hybrid control algorithm is used to adjust the end-arm posture so that the electromagnetic docking surface is aligned with the target contact point. S4. When the docking surface error is less than the threshold, the electromagnetic module is switched to the rigid locking mode to complete the rigid connection between the manipulator and the target; S5. Perform load transfer or equipment maintenance operations through the robotic arm. After the task is completed, release the electromagnetic lock and separate.

2. The on-orbit control method based on the docking of a robotic arm and electromagnetics according to claim 1, characterized in that: In step S1, the initial position of the target spacecraft is obtained by using a visual sensor and a laser rangefinder, and the motion trajectory of the robotic arm is planned. The specific process is as follows: The visual sensor (binocular camera) acquires image data of the target spacecraft, extracts the QR code or feature points on the target surface, and uses the SURF algorithm to match the feature points based on a pre-stored 3D model of the target. The EPnP algorithm uses the matched feature points to calculate the position and attitude of the target spacecraft relative to the visual sensor, synchronously integrating the precise relative distance provided by the laser rangefinder to compensate for the error of the visual sensor. The robot arm's motion trajectory is solved through inverse kinematics. The robotic arm body adopts a 7-degree-of-freedom redundant configuration, and the joint drive module integrates a harmonic reducer and a torque sensor. The closed-loop PID control can achieve end-point repeatability accuracy to meet certain requirements.

3. The on-orbit control method based on the docking of a robotic arm and electromagnetics according to claim 1, characterized in that: In step S2, the electromagnetic docking module is activated to generate a gradient magnetic field. The specific process is as follows: The electromagnetic docking module includes an array of coaxial annular electromagnetic coils. By independently controlling the current intensity of each coil and superimposing their magnetic field distribution, a directional gradient magnetic field is generated. The dynamic control range of the magnetic field intensity can adapt to the needs from weak adsorption to rigid locking. During operation, the magnetic field strength is dynamically adjusted based on the relative distance between the end of the robotic arm and the target, and the electromagnetic force is activated when the target enters the adsorption range. The PID controller is used to compensate for external disturbances and maintain adsorption stability, ensuring that the dynamic adjustment accuracy of adsorption force meets the requirements; The core component electromagnetic docking module: a coaxial annular electromagnetic coil is installed at the end, which is composed of a high-density copper winding and an iron-cobalt alloy core.

4. The on-orbit control method based on the docking of a robotic arm and electromagnetics according to claim 1, characterized in that: In step S3, the cascaded force / position hybrid control algorithm is used to adjust the end-arm posture. The specific process is as follows: The visual prediction controller (SVPC) first predicts the target pose based on the target feature points identified by the binocular vision camera, using the EPnP algorithm and combined with laser rangefinder data. It then constructs the manipulator's kinematic state-space equations, solves inverse kinematics, and optimizes the manipulator's joint angular velocities to enable the manipulator to quickly approach the target. Next, the force prediction controller (FPC) receives data from the six-axis force sensor and Hall-effect magnetometer. Based on the contact force error model, it uses quadratic programming to solve the optimal control variable and dynamically correct the end-point pose to ensure alignment between the electromagnetic docking surface and the target contact point, while also ensuring that dynamic constraints are met. Based on the Hall effect magnetometer data and the current joint angle, the electromagnetic contact force deviation is compensated through the magnetic field-mechanical coupling compensation model; The cascaded force / position hybrid control algorithm includes: a visual predictive controller (SVPC) constructs a state-space equation based on the target feature point recognition results to optimize the angular velocity of the manipulator joint; a force predictive controller (FPC) corrects the manipulator end position according to the contact force error model to meet the dynamic constraints; The multimodal sensing unit includes: a binocular vision camera, a six-dimensional force sensor and a Hall effect magnetometer; The contact force error dynamics model is: Among them, M C 、C C , K C are the inertia, damping and stiffness matrices respectively, x is the end pose deviation, and the optimal joint torque is solved by quadratic programming (QP); The magnetic field-mechanical coupling compensation model is: F em =K m ·B 2 ·J -T (q d -q) Among them, F em is the electromagnetic compensation force, K m is the magnetic-mechanical coupling coefficient, B is the magnetic field strength, J is the Jacobian matrix of the manipulator, q d and q are the expected and actual joint angles.

5. The on-orbit control method based on the docking of a robotic arm and electromagnetics according to claim 1, characterized in that: In step S4, when the interface error is less than the threshold, the electromagnetic module is switched to the rigid locking mode to complete the rigid connection between the manipulator and the target. The specific process is as follows: The multimodal sensing unit monitors the position error of the docking surface in real time. When the error is less than the set threshold, the electromagnetic docking module is triggered to generate a high-intensity gradient magnetic field. The six-dimensional force sensor verifies the stability of the adsorption force to ensure that the target surface fits the electromagnetic docking surface, and mechanical locking is intervened to achieve a rigid connection. When the electromagnetic locking fails, the redundant gripper at the end of the robotic arm deploys, and based on vision and force feedback, the gripper position is adjusted to grasp the target structure. In addition, a suspended damping mechanism is set at the end of the robotic arm to absorb the docking impact energy, and the damping coefficient is dynamically selected within an adjustable range.

6. The on-orbit control method based on robotic arm and electromagnetic docking according to claim 1, characterized in that: After the task in step S5 is completed, the electromagnetic lock is released and separated; the specific process is: After the on-orbit service mission is completed, the complete unlocking is confirmed by gradually attenuating the magnetic field strength, releasing the mechanical clips, and detecting the force sensors; the separation path of the robotic arm is planned using inverse kinematics calculations to ensure the safety and reliability of the entire process.

Images