Double-arm space robot adhesion capture control method

Abstract

The invention discloses a double-arm space robot adhesion and capture control method, which is characterized in that the double-arm space robot adhesion and capture control method is used for a double-arm space robot system. The double-arm space robot system comprises a double-arm space robot platform (1), a first space mechanical arm (2), an end effector (4) of the first space mechanical arm (2), a second space mechanical arm (3) and an end effector (5) of the second space mechanical arm (3), and the adhesion and capture control method for the double-arm space robot comprises the following steps that 1, an adhesion concept is put forward, and an adhesion and capture mode of the double-arm space robot is designed; 2, a coordinate system is established, and dynamics modeling of the two-arm space robot is completed; 3, designing an autonomous path planning algorithm in adhesion capture; step 4, completing the design of an adhesion capture controller by using a contact force control strategy; and 5, carrying out closed-loop numerical simulation, and verifying the effectiveness of double-arm adhesion capture.

Description

Technical Field

[0001] The present invention belongs to the technical field of spacecraft on-orbit service and space debris removal, and relates to an adhesion capture control method for a dual-arm space robot to capture a moving target. Background Art

[0002] In recent years, space debris caused by launch failures, functional failures, and even fuselage disintegration has seriously affected the safety of the space environment. The number of space debris in low-Earth orbit has far exceeded the number of spacecraft currently in orbit, and it is still increasing with the accumulation of time. In June 2024, a Russian low-orbit remote sensing satellite suddenly disintegrated, generating at least 250 pieces of space debris, which directly triggered an emergency risk avoidance warning for the International Space Station. Since its operation in orbit, my country's Tiangong Space Station has taken emergency measures at least twice to avoid space collisions. In August 2023, the United States decided to promote the Orbital Sustainability Act, authorizing NASA to jointly develop and demonstrate key technologies for removing orbital debris with the U.S. Department of Commerce. According to NASA's forecast model, at least 5-10 pieces of space debris need to be removed each year to maintain the safety and stability of the low-orbit environment. Therefore, the removal of space debris will become a difficult problem to be overcome in the future aerospace field, and it is the key to reducing the cost of spacecraft operation and maintenance and improving the safety of the space environment.

[0003] The core of the space debris removal task is to use active spacecraft to capture space debris and transfer it to the graveyard orbit to achieve the removal task. Compared with conventional non-contact capture, using space robots to directly contact debris targets and then implement capture has the advantages of higher reliability, stronger safety, and greater control. In order to achieve the capture of targets by space robots, many scholars at home and abroad have carried out a lot of research. At present, most of the research focuses on the capture of targets by single-arm space robots, while there are few studies on the capture of targets by dual-arm space robots. Compared with single-arm space robots, dual-arm space robots have greater load capacity, higher operational flexibility, and stronger task adaptability. Using dual-arm space robots for space debris removal has more advantages. However, there are problems in existing related studies such as easy saturation of contact force, easy damage to the end of the robotic arm, and easy escape of the target. Therefore, using dual-arm space robots as active spacecraft to complete debris removal tasks is a hot and difficult problem.

[0004] In summary, in order to achieve the capture of moving debris targets by the dual-arm space robot, it is necessary to consider reducing the relative motion state between the target and the robotic arm to ensure that it is within the capture capability of the robotic arm and avoid damage caused by excessive contact force at the end of the robotic arm. At the same time, it is necessary to consider avoiding pushing the target away from the dual-arm space robot to avoid relative orbit control problems caused by target escape.

[0005] Based on the above situation, it is particularly important to design a new capture control method to reduce the contact force at the end of the robot arm, avoid contact force saturation, prevent damage to the end effector, and avoid the risk of target escape. Summary of the invention

[0006] The purpose of the present invention is to provide a kind of space debris removal task for a dual-arm space robot, propose a new adhesion capture control method, provide new ideas and methods for the design of ultra-compliant controller for debris removal, effectively improve the compliant control performance of the dual-arm space robot in capturing debris targets, and avoid the risks of contact force saturation, mechanical arm damage and target escape.

[0007] The present invention provides a dual-arm space robot adhesion capture control method, the dual-arm space robot adhesion capture control method is used for a dual-arm space robot system, the dual-arm space robot system comprises a dual-arm space robot platform (1), a first space robot arm (2) and an end effector (4) thereof, a second space robot arm (3) and an end effector (5) thereof, the dual-arm space robot adhesion capture control method comprises the following steps:

[0008] Step 1: Propose the concept of adhesion and design the adhesion grasping method of the dual-arm space robot;

[0009] Step 2, establish a coordinate system and complete the dynamic modeling of the dual-arm space robot;

[0010] Step 3, design an autonomous path planning algorithm in adhesion capture;

[0011] Step 4, using the contact force control strategy to complete the controller design of adhesion capture;

[0012] Step 5: Closed-loop numerical simulation to verify the effectiveness of dual-arm adhesion capture.

[0013] Preferably, in step 1, the adhesion refers to a process in which the end effector of the robot arm moves with the target for a period of time before performing the capture.

[0014] Preferably, in step 1, the dual-arm space robot adhesion capture method includes: by driving the joints of the robotic arms, an autonomously adjustable tiny contact force is maintained between the end effector of each robotic arm and the target, so that the end effector is always maintained near the contact point of the target corresponding to it.

[0015] Preferably, in step 2, it is assumed that the i-th (i=1,2) mechanical arm of the dual-arm space robot has n i (i=1,2) arms, each of which is connected by a single-degree-of-freedom rotation joint;

[0016] Establish coordinate system: The platform system of the dual-arm space robot is Σb , whose origin is located at the center of mass of the space robot platform; the target system is Σ t , whose origin is at the target mass center; the rod coordinate system Σ i,j The origin is located on the axis of the jth joint of the i-th robot arm, which is fixed to the j-th arm rod; the rod reference coordinate system The origin of the coordinate system is located on the axis of rotation of the jth joint of the i-th robot arm. With Σ i,j The z-axis of the revolute joint is aligned with the rotation axis Γ i,j The direction of the end effector is parallel to hi The origin is located at the nth i The end of a rod, used to describe the operation task; the catch point system The origin is located at the i-th capture point on the target. When the i-th robot arm completes the capture, Σ hi With Σ hi* Coincidence; inertial coordinate system Σ I The origin is at the center of the earth, the z-axis points to the North Pole along the polar axis of the earth, the x-axis points to the vernal equinox, and the y-axis, x-axis, and z-axis form a right-handed coordinate system;

[0017] Introducing the homogeneous transformation matrix A T B , which means: the homogeneous transformation matrix of coordinate system B relative to coordinate system A, let A r B and A R B are the position vector matrix and coordinate transformation matrix of coordinate system B relative to coordinate system A, respectively. Then the homogeneous transformation matrix between the two coordinate systems is A T B It can be expressed as: The homogeneous transformation matrix can be used to solve the forward kinematics equation of the dual-arm space robot, that is, the end effector system Σ hi Relative platform system Σ b The pose can be solved using the homogeneous transformation matrix in, b T hi is the end effector system Σ hi Relative platform system Σ b The coordinate transformation matrix, b T i,1 is the rod coordinate system Σ i,1 Relative platform system Σ b The coordinate transformation matrix, i,(j-1) T i,j is the rod coordinate system Σ i,j Relative rod coordinate system Σ i,j-1 The coordinate transformation matrix, is the end effector system Σ hiRelative rod coordinate system The coordinate transformation matrix of

[0018] Using Kane equation, the dynamic equation of the dual-arm space robot can be derived as follows: Among them, M b With M m are the generalized mass matrices of the platform and the two robotic arms, M bm is the coupling mass matrix between the platform and the two robotic arms; V b is the platform relative inertial system Σ I The linear velocity and angular velocity are projected on the platform system Σ b middle; is the joint angular velocity of the two robotic arms; c b With c m are the nonlinear generalized inertial forces corresponding to the platform and the two robotic arms respectively; F b is the external force on the platform b The spatial force formed is projected on Σ b τ is the joint torque of the two manipulators; J b With J m are the Jacobian matrices of the platform and the robot arm respectively; F h is the contact force / torque on the ends of the two manipulators, projected in the end effector system; similarly, the dynamic equation of the target to be captured is Among them, M t is the generalized mass matrix of the target; V t is the target relative inertial system Σ I The linear velocity and angular velocity are projected on the target system Σ t c t is the nonlinear generalized inertial force of the target; is the generalized Jacobian matrix of the target.

[0019] Preferably, the step 3 comprises:

[0020] Step 31, obtaining the relative position information between the end of each robotic arm and the target capture point through kinematic relationship calculation of the dual-arm space robot;

[0021] Step 32, using the relative posture information between the end of the robot arm and the target capture point, the visual servo method can be used to complete the trajectory planning of the robot arm in the workspace, laying the foundation for the subsequent design of the adhesion capture controller.

[0022] Preferably, the step 31 comprises:

[0023] Let the target system Σ t Relative to the end effector system of the i-th robot arm Σ hi The position and posture of hi pt and hi R t , assuming that the camera center of each robot coincides with the origin of its end effector system, we can get hi p t =( I R hi ) T ( I p t - I p hi ), hi R t =( I R hi ) TI R t ,in I p t and I R t They are Σ t Relative inertial systemΣ I The position vector matrix and coordinate transformation matrix, I p hi and I R hi They are Σ hi Relative Σ I The position vector matrix and coordinate transformation matrix of the target system Σ t Relative end effector system Σ hi Homogeneous transformation matrix hi T t for: On the other hand, since the position of the capture point on the target is fixed, the capture point system Σ hi* Relative target system Σ t Homogeneous transformation matrix t T hi* is a constant matrix; therefore, the end effector system of the i-th robot arm is Σ hi The corresponding capture point system Σ hi* The homogeneous transformation matrix between is: hi T hi* = hi T tt T hi* .

[0024] Preferably, the step 32 comprises:

[0025] Define the capture posture error of the end of the i-th robotic arm for in hi p hi* and hi θ hi*They are the position and attitude angle of the target capture point relative to the end of the robotic arm; based on the kinematic relationship of the robotic arm, combined with hi p hi* and hi θ hi* The time derivative of the expected capture posture error of the end effector in the workspace is obtained as follows: in hi R b For platform system b Relative Σ hi The coordinate transformation matrix E 3 is a 3×3 unit matrix; 0 3×3 is a 3×3 zero matrix; is the Jacobian matrix of the i-th robot; is the joint angular velocity of the i-th robot arm; T( hi θ hi* ) is the rotation direction matrix of the axis; the superscript “×” is the symbol for finding the matrix cross product antisymmetric matrix; let the Jacobian matrix be The desired trajectory of the end effector in the workspace can be converted into the desired trajectory of each robot joint angle in the joint space. The joint angular velocity command in the joint space is: The superscript “+” in the formula is the symbol for finding the pseudo-inverse of the matrix. is the positive definite symmetric matrix to be selected.

[0026] Preferably, step 4 comprises:

[0027] The expected positions and angular velocities of the two robot end effectors relative to the platform are defined as and Then the control law of the force control loop can be designed as: In the formula, and is the expected contact force and torque at the end of the robot, both described in the end effector system, f h and τ h are the measured values ​​of contact force and torque, all described under the end effector system; and is the desired velocity and angular velocity of the end of the manipulator under force control, both described in the end effector system; K is the control gain matrix, the subscript t represents translation, and o represents rotation;

[0028] When the contact force is less than the expected value, the above control law will cause the end of the robot arm to move in the contact direction, thereby increasing the contact force and gradually making it equal to the expected value;

[0029] The robot arm motion controller used for the force controller can be designed as: In the formula, b P h andb ω h K is the actual position and angular velocity of the two robot end effectors relative to the platform; Dp , K Pp , K Do and K Po They are all control gain matrices; The attitude error is defined as: In the formula, b x h , b y h and b z h is the coordinate transformation matrix of the end effector system of the two manipulators relative to the platform system b R h The amount of and is the desired coordinate transformation matrix of the end effector system of the two manipulators relative to the platform system The specific relationship is: b x h b y h b z h ]= b R h ,

[0030] The acceleration and angular acceleration of the end effector relative to the platform, and the joint angular acceleration are obtained by redundant decomposition of the acceleration level for: In the formula, J m is the geometric Jacobian matrix of the robot,

[0031] According to the dynamic equation of the dual-arm space robot system derived in step 2, when the contact force and contact torque at the end of the robot arm are considered, the dynamic model of the robot arm with a fixed base is written as: Using the inverse dynamics control method of the robot arm, the robot arm joint control torque command can be obtained as: In the formula,

[0032] Preferably, step 5 includes: according to the system kinematics and dynamics model established in step 2, utilizing the autonomous trajectory planning algorithm and adhesion capture controller designed in steps 3 and 4, simulating the space debris removal task in aerospace engineering applications, and completing a closed-loop numerical simulation of the process of a dual-arm space robot capturing a six-degree-of-freedom single rigid body target; by analyzing the closed-loop simulation results, if the capture position and attitude errors of the two robotic arms can converge to near zero, it proves that the designed adhesion capture control is effective.

[0033] The beneficial effects of the present invention include:

[0034] 1. The capture method of the present invention cleverly applies the ball-stopping technology of slowing down the ball to the capture control of the robot arm, designs the adhesion process before the formal capture, and makes the end effector move with the target in a small range, so as to avoid the target escaping due to direct capture;

[0035] 2. The capture method of the present invention combines adhesion with an improved adaptive impedance control method, effectively improving the compliant control performance of the dual-arm space robot in capturing debris targets, avoiding contact force saturation and damage to the end of the robotic arm;

[0036] 3. In order to verify the effect of adhesion, the capture method of the present invention provides the adhesion threshold condition for starting the adhesion process, and verifies its effectiveness through multiple sets of comparative numerical simulations. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. By referring to the drawings, the features and advantages of the present invention will be more clearly understood. The drawings are schematic and should not be understood as limiting the present invention in any way. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0038] Figure 1 It is a flowchart of the method of the present invention;

[0039] Figure 2 This is a schematic diagram of a dual-arm space robot capturing a target;

[0040] Figure 3 It is the ball stopping technique in badminton

[0041] Figure 4 It is the adhesion capture method of the dual-arm space robot

[0042] Figure 5 It is a schematic diagram of the coordinate system

[0043] Figure 6 This is the contact force control diagram in adhesion capture

[0044] Figure 7 is the motion state of the arms adhering to the target

[0045] Figure 8 is the capture posture error of the first robot arm

[0046] Fig. 9 is the capture posture error of the second robot arm

[0047] Fig.10 is the contact force and contact torque on the end of the first robot arm

[0048] Fig.11 is the contact force and contact torque on the end of the second robot arm

[0049] Fig.12 is the joint angle and joint angular velocity of the first robot arm

[0050] Fig.13 is the joint angle and joint angular velocity of the second robot arm

[0051] Fig.14 Comparison of the capture error of the first robot arm with and without adhesion

[0052] Fig.15 Comparison of the capture error of the second robot arm with and without adhesion

[0053] Description of reference numerals:

[0054] 1-dual-arm space robot platform; 2-first robotic arm; 3-second robotic arm; 4-end effector of the first robotic arm; 5-end effector of the second robotic arm; 6-first capture point; 7-second capture point; 8-target. DETAILED DESCRIPTION

[0055] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] The technical solution of the present invention is: a dual-arm space robot adhesion capture control method, based on the inspiration of the technical essentials of the ball-catching slow force in the badminton ball stopping technology, the concept of adhesion is proposed, a new capture mode of the dual-arm space robot adhesion capture control is designed, and the controller design of the adhesion capture is completed. The method is applicable to any dual-arm space robot capture system, the system includes a dual-arm space robot platform, two space manipulators and their end effectors, the space manipulators are used for transmission, and the end effectors are used for capturing the target 8. To achieve the above purpose, the method of the present invention includes the following steps: step 1, propose the concept of adhesion, design the dual-arm space robot adhesion capture mode; step 2, establish a coordinate system, and complete the dynamic modeling of the dual-arm space robot; step 3, design an autonomous path planning algorithm in adhesion capture; step 4, use the contact force control strategy to complete the controller design of adhesion capture; step 5, verify the effectiveness of the dual-arm space robot adhesion capture through closed-loop numerical simulation.

[0057] The concept of adhesion in step 1 is inspired by the badminton ball stopping technique. The key to the ball stopping technique is to slow down the force when facing the ball. Specifically, when the ball is coming, the racket needs to first move with the ball for a short distance, and then slowly touch the ball with the racket face, and then stop the ball steadily on the racket face. During the ball stopping process, the racket and the ball need to maintain consistency in movement to avoid direct contact with the ball with the racket and causing it to be hit away. The present invention defines a process similar to the racket moving with the ball for a short distance as adhesion.

[0058] In step 2, the dual-arm space robot and the target fragment are regarded as rigid bodies, and the body coordinate system, joint reference system and capture system are established. On the basis of establishing the coordinate system, the concepts of homogeneous transformation matrix and space velocity are introduced to derive the open-chain kinematic equation of the dual-arm space robot. At the same time, the Kane equation is used to establish the dynamic equation of the dual-arm space robot and the target, laying the foundation for trajectory planning and control in the subsequent robot adhesion capture operation.

[0059] In step three, it is assumed that the camera coordinate system in each robotic arm coincides with the end effector system of the robotic arm. Then, the relative posture information between the end of the robotic arm and the target capture point is given from a kinematic perspective. Then, the visual servo method based on position information is used to plan the expected motion trajectory in the workspace of each robotic arm in real time online, completing the autonomous path planning of the dual-arm space robot to capture the moving target.

[0060] In step 4, under the action of adhesion, the end of each robot arm maintains a small contact force with the target, so that it always maintains a close distance to the target, that is, the end effector moves with the target in a small range, thereby avoiding excessive contact force at the capture moment and contact force saturation. In addition, considering the uncertainty of the capture environment, adhesion is combined with improved adaptive impedance control to realize the adhesion capture operation of the dual-arm space robot to avoid accidental damage.

[0061] In step five, a dual-arm space robot is used to capture the moving target, realizing the entire process from trajectory planning, approach, adhesion to capture. The effectiveness of the dual-arm adhesion capture method is verified by comparing numerical simulations.

[0062] The specific scheme of the present invention is described below. A dual-arm space robot adhesion capture control method is based on the technical essentials of slowing down the ball in badminton ball stopping technology, proposes the concept of adhesion, designs a new capture method of dual-arm space robot adhesion capture control, and completes the controller design of adhesion capture. The method is applicable to any dual-arm space robot capture system, and the system includes a dual-arm space robot platform (1), two space robot arms and their end effectors. The adhesion capture control method includes the following steps:

[0063] Step 1: Propose the concept of adhesion and design the adhesion grasping method of the dual-arm space robot.

[0064] The technical key to the ball stopping technique in badminton is to slow down the force when facing the ball, that is, when the oncoming badminton flies in a rotating high-speed motion state, if the racket first accompanies the ball for a short distance, and then slowly touches the ball with the racket face, the badminton can be stopped steadily on the racket face. Inspired by this, the process of the end effector of the robot arm accompanying the target for a period of time before implementing the capture is defined as adhesion. The adhesion capture method of the dual-arm space robot can be designed to maintain a small contact force that can be adjusted independently between the end effector of each robot arm and the target through the controller design, so that the end effector is always maintained near the corresponding target contact point. Under the action of adhesion, the relative movement between the end effector of each robot arm and the target is small, so the maximum contact force and contact torque generated when the end effector implements the capture are also relatively small, which can effectively avoid contact force saturation and damage to the end effector.

[0065] Step 2: Establish a coordinate system and complete the dynamic modeling of the dual-arm space robot.

[0066] Suppose the i-th (i=1,2) manipulator of the dual-arm space robot has n i (i=1,2) arms, which are connected by single-degree-of-freedom rotation joints. The established coordinate system is as follows: The platform system of the dual-arm space robot is Σ b, whose origin is located at the center of mass of the space robot platform; the target system is Σ t , whose origin is at the target mass center; the rod coordinate system Σ i,j The origin is located on the axis of the jth joint of the i-th robot arm, which is fixed to the j-th arm rod; the rod reference coordinate system The origin of the coordinate system is located on the axis of rotation of the jth joint of the i-th robot arm. With Σ i,j The z-axis of the revolute joint is aligned with the rotation axis Γ i,j The direction of the end effector is parallel to hi The origin is located at the nth i The end of a rod, used to describe the operation task; the catch point system The origin is located at the i-th capture point on the target. When the i-th robot arm completes the capture, Σ hi With Σ hi* Coincidence; inertial coordinate system Σ I The origin is at the center of the earth, the z-axis points to the North Pole along the earth's polar axis, the x-axis points to the vernal equinox, and the y-axis, x-axis and z-axis form a right-handed coordinate system.

[0067] Introducing the homogeneous transformation matrix A T B , which means: the homogeneous transformation matrix of coordinate system B relative to coordinate system A, let A r B and A R B are the position vector matrix and coordinate transformation matrix of coordinate system B relative to coordinate system A, respectively. Then the homogeneous transformation matrix between the two coordinate systems is A T B It can be expressed as: The homogeneous transformation matrix can be used to solve the forward kinematics equation of the dual-arm space robot, that is, the end effector system Σ hi Relative platform system Σ b The pose can be solved using the homogeneous transformation matrix in, b T hi is the end effector system Σ hi Relative platform system Σ b The coordinate transformation matrix, b T i,1 is the rod coordinate system Σ i,1 Relative platform system Σ b The coordinate transformation matrix, i,(j-1) T i,j is the rod coordinate system Σ i,j Relative rod coordinate system Σ i,j-1 The coordinate transformation matrix, is the end effector system Σ hi Relative rod coordinate system The coordinate transformation matrix.

[0068] Using Kane equation, the dynamic equation of the dual-arm space robot can be derived as follows: Among them, M b With M m are the generalized mass matrices of the platform and the two robotic arms, M bm is the coupling mass matrix between the platform and the two robotic arms; V b is the platform relative inertial system Σ I The linear velocity and angular velocity are projected on the platform system Σ b middle; is the joint angular velocity of the two robotic arms; c b With c m are the nonlinear generalized inertial forces corresponding to the platform and the two robotic arms respectively; F b is the external force on the platform b The spatial force formed is projected on Σ b τ is the joint torque of the two manipulators; J b With J m are the Jacobian matrices of the platform and the robot arm respectively; F h is the contact force / torque on the ends of the two manipulators, projected in the end effector system. Similarly, the dynamic equation of the target to be captured is: Among them, M t is the generalized mass matrix of the target; V t is the target relative inertial system Σ I The linear velocity and angular velocity are projected on the target system Σ t c t is the nonlinear generalized inertial force of the target; is the generalized Jacobian matrix of the target.

[0069] Step 3: Design an autonomous path planning algorithm for adhesion capture.

[0070] Since the dual-arm space robot and the target are moving in real time, the capture point system In the platform system b The position and posture of the object are constantly changing. At this time, it is necessary to use a hand-eye camera to shoot the target capture point in real time, and then use the sensor to measure the relative posture information between the target and the camera.

[0071] First, the kinematic relationship of the dual-arm space robot is calculated to obtain the relative position information between the end of each robotic arm and the target capture point. t Relative to the end effector system of the i-th robot arm Σ hi The position and posture of hi p t andhi R t , assuming that the camera center of each robot coincides with the origin of its end effector system, we can get hi p t =( I R hi ) T ( I p t - I p hi ), hi R t =( I R hi ) TI R t ,in I p t and I R t They are Σ t Relative inertial systemΣ I The position vector matrix and coordinate transformation matrix, I p hi and I R hi They are Σ hi Relative Σ I The position vector matrix and coordinate transformation matrix of the target system Σ t Relative end effector system Σ hi Homogeneous transformation matrix hi T t for: On the other hand, since the position of the capture point on the target is fixed, the capture point system Σ hi* Relative target system Σ t Homogeneous transformation matrix t T hi* is a constant matrix. Therefore, the end effector system of the i-th robot arm is Σ hi The corresponding capture point system Σ hi* The homogeneous transformation matrix between is: hi T hi* = hi T tt T hi* .

[0072] Then, using the relative posture information between the end of the robot and the target capture point, the visual servo method can be used to complete the trajectory planning of the robot in the workspace, laying the foundation for the subsequent design of the adhesion capture controller. Define the capture posture error of the end of the i-th robot for in hi p hi* and hi θ hi*are the position and attitude angle of the target capture point relative to the end of the robotic arm. Based on the kinematic relationship of the robotic arm, combined with hi p hi* and hi θ hi* The time derivative of the expected capture posture error of the end effector in the workspace is obtained as follows: in hi R b For platform system b Relative Σ hi The coordinate transformation matrix E 3 is a 3×3 unit matrix; 0 3×3 is a 3×3 zero matrix; is the Jacobian matrix of the i-th robot; is the joint angular velocity of the i-th robot arm; T( hi θ hi* ) is the rotation direction matrix of the axis; the superscript “×” is the symbol for finding the matrix cross product antisymmetric matrix. Let the Jacobian matrix be The desired trajectory of the end effector in the workspace can be converted into the desired trajectory of each robot joint angle in the joint space. The joint angular velocity command in the joint space is: The superscript “+” in the formula is the symbol for finding the pseudo-inverse of the matrix. is the positive definite symmetric matrix to be selected.

[0073] Step 4: Use the contact force control strategy to complete the controller design for adhesion capture.

[0074] In the process of the dual-arm space robot capturing a target, the end effectors of the two robotic arms contact the capture point on the target, which will generate complex collision contact forces. Due to the existence of errors such as measurement and control, the contact force between the end effector and the target may be relatively large, and excessive contact force can easily lead to damage to the end effector or failure to capture the target. In order to reduce the impact of the physical contact between the end effector and the target contact point on the capture stage, the present invention adds an adhesion capture process in the early stage of capture. During the adhesion process, a relatively small contact force is maintained between the end effector and the target so that the end of the robotic arm is always maintained at a relatively close distance to the target contact point. Under the adhesion effect, since the relative movement between the end effector and the target is small, the maximum contact force and contact torque generated at the capture moment are also relatively small, which can avoid contact force saturation and damage to the end effector.

[0075] The expected positions and angular velocities of the two robot end effectors relative to the platform are defined as and Then the control law of the force control loop can be designed as: In the formula, and is the expected contact force and torque at the end of the robot, both described in the end effector system, f h and τ h are the measured values ​​of contact force and torque, all described under the end effector system; and is the desired speed and angular velocity of the end of the manipulator under force control, all described in the end effector system; K is the control gain matrix, the subscript t represents translation, and o represents rotation. When the contact force is less than the expected value, the above control law will cause the end of the manipulator to move in the contact direction, thereby increasing the contact force and gradually making it equal to the expected value.

[0076] The robot arm motion controller used for the force controller can be designed as: In the formula, b P h and b ω h K is the actual position and angular velocity of the two robot end effectors relative to the platform; Dp , K Pp , K Do and K Po They are all control gain matrices; The attitude error is defined as: In the formula, b x h , b y h and b z h is the coordinate transformation matrix of the end effector system of the two manipulators relative to the platform system b R h The weight of and is the desired coordinate transformation matrix of the end effector system of the two manipulators relative to the platform system The specific relationship is: b x h b y h b z h ]= b R h ,

[0077] The acceleration and angular acceleration of the end effector relative to the platform can be obtained by redundant decomposition of the acceleration level to obtain the joint angular acceleration for: In the formula, J m is the geometric Jacobian matrix of the robot,

[0078] According to the dynamic equation of the dual-arm space robot system derived in the second step, when the contact force and contact torque at the end of the robot arm are considered, the dynamic model of the robot arm with a fixed base can be written as: Using the inverse dynamics control method of the robot arm, the robot arm joint control torque command can be obtained as: In the formula,

[0079] Step 5: Verify the effectiveness of the dual-arm space robot's adhesion capture through closed-loop numerical simulation. Based on the system kinematics and dynamics model established in step 2, the autonomous trajectory planning algorithm and adhesion capture controller designed in steps 3 and 4 are used to simulate the space debris removal task in aerospace engineering applications, and complete the closed-loop numerical simulation of the dual-arm space robot's capture of a six-degree-of-freedom single rigid body target. By analyzing the closed-loop simulation results, if the capture position and attitude errors of the two robotic arms can converge to near zero, it proves that the designed adhesion capture control is effective.

[0080] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0081] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0082] The flowchart of the method of the present invention is as follows Figure 1 As shown, specifically, the adhesion capture control method includes the following steps:

[0083] Step 1: Propose the concept of adhesion and design the adhesion grasping method of the dual-arm space robot.

[0084] The schematic diagram of the dual-arm space robot capturing a target in the present invention is as follows: Figure 2 As shown in the figure, the dual-arm space robot consists of a spacecraft platform and two space manipulators. An end effector is installed at the end of each manipulator to capture the target. The target to be captured can be regarded as a single rigid body with 6 degrees of freedom, and there are two capture points on the target.

[0085] The concept of adhesion proposed in the present invention originates from the ball stopping technique in badminton, and the technical essentials are to slow down the ball, such as Figure 3As shown. When the oncoming badminton flies in a high-speed rotating state, if the racket is used to directly touch the badminton, it may cause the badminton to be bounced away. However, if the racket first accompanies the ball for a short distance, and then slowly touches the ball with the racket face, that is, the ball is slowed down, the badminton can be steadily stopped on the racket face. Inspired by this, the present invention defines the process of the end effector of the robot arm accompanying the target for a period of time and then implementing the capture as adhesion, such as Figure 4 As shown. The dual-arm space robot adhesion capture method designed by the present invention is to maintain a small contact force between the end effector of each robot arm and the target through the controller design, so that the end of each robot arm is always maintained at a close distance to the target contact point. Under the action of adhesion, the relative movement between the end effector of each robot arm and the target is small, so the maximum contact force and contact torque generated when the end effector implements capture are also relatively small, which can effectively avoid contact force saturation and damage to the end effector.

[0086] Step 2: Establish a coordinate system and complete the dynamic modeling of the dual-arm space robot.

[0087] Suppose the i-th (i=1,2) manipulator of the dual-arm space robot has n i (i=1,2) arms, and the arms are connected by single-degree-of-freedom rotation joints. The coordinate system established by the present invention is as follows Figure 5 As shown, the platform system of the dual-arm space robot is Σ b , whose origin is located at the center of mass of the space robot platform; the target system is Σ t , whose origin is at the target mass center; the rod coordinate system Σ i,j The origin is located on the axis of the jth joint of the i-th robot arm, which is fixed to the j-th arm rod; the rod reference coordinate system The origin of the coordinate system is located on the axis of rotation of the jth joint of the i-th robot arm. With Σ i,j The z-axis of the revolute joint is aligned with the rotation axis Γ i,j The direction of the end effector is parallel to hi The origin is located at the nth i The end of a rod, used to describe the operation task; the catch point system The origin is located at the i-th capture point on the target. When the i-th robot arm completes the capture, Σ hi With Σ hi* Coincidence; inertial coordinate system Σ I The origin is at the center of the earth, the z-axis points to the North Pole along the earth's polar axis, the x-axis points to the vernal equinox, and the y-axis, x-axis and z-axis form a right-handed coordinate system.

[0088] Introducing the homogeneous transformation matrix A T B, which means: the homogeneous transformation matrix of coordinate system B relative to coordinate system A, let A r B and A R B are the position vector matrix and coordinate transformation matrix of coordinate system B relative to coordinate system A, respectively. Then the homogeneous transformation matrix between the two coordinate systems is A T B It can be expressed as: The homogeneous transformation matrix can be used to solve the forward kinematics equation of the dual-arm space robot, that is, the end effector system Σ hi Relative platform system Σ b The pose can be solved using the homogeneous transformation matrix in, b T hi is the end effector system Σ hi Relative platform system Σ b The coordinate transformation matrix, b T i,1 is the rod coordinate system Σ i,1 Relative platform system Σ b The coordinate transformation matrix, i,(j-1) T i,j is the rod coordinate system Σ i,j Relative rod coordinate system Σ i,j-1 The coordinate transformation matrix, is the end effector system Σ hi Relative rod coordinate system The coordinate transformation matrix.

[0089] Using Kane equation, the dynamic equation of the dual-arm space robot can be derived as follows: Among them, M b With M m are the generalized mass matrices of the platform and the two robotic arms, M bm is the coupling mass matrix between the platform and the two robotic arms; V b is the platform relative inertial system Σ I The linear velocity and angular velocity are projected on the platform system Σ b middle; is the joint angular velocity of the two robotic arms; c b With c m are the nonlinear generalized inertial forces corresponding to the platform and the two robotic arms respectively; F b is the external force on the platform b The spatial force formed is projected on Σ b τ is the joint torque of the two manipulators; J b With J m are the Jacobian matrices of the platform and the robot arm respectively; F his the contact force / torque on the ends of the two manipulators, projected in the end effector system. Similarly, the dynamic equation of the target to be captured is: Among them, M t is the generalized mass matrix of the target; V t is the target relative inertial system Σ I The linear velocity and angular velocity are projected on the target system Σ t c t is the nonlinear generalized inertial force of the target; is the generalized Jacobian matrix of the target.

[0090] Step 3: Design an autonomous path planning algorithm for adhesion capture.

[0091] Since the dual-arm space robot and the target are moving in real time, the capture point system Σ hi* In the platform system b The position and posture of the object are constantly changing. At this time, it is necessary to use a hand-eye camera to shoot the target capture point in real time, and then use the sensor to measure the relative posture information between the target and the camera.

[0092] First, the kinematic relationship of the dual-arm space robot is calculated to obtain the relative position information between the end of each robotic arm and the target capture point. t Relative to the end effector system of the i-th robot arm Σ hi The position and posture of hi p t and hi R t , assuming that the camera center of each robot coincides with the origin of its end effector system, we can get hi p t =( I R hi ) T ( I p t - I p hi ), hi R t =( I R hi ) TI R t ,in I p t and I R t They are Σ t Relative inertial systemΣ I The position vector matrix and coordinate transformation matrix, I p hi and I R hi They are Σ hiRelative Σ I The position vector matrix and coordinate transformation matrix of the target system Σ t Relative end effector system Σ hi Homogeneous transformation matrix hi T t for: On the other hand, since the position of the capture point on the target is fixed, the capture point system Σ hi* Relative target system Σ t Homogeneous transformation matrix t T hi* is a constant matrix. Therefore, the end effector system of the i-th robot arm is Σ hi The corresponding capture point system Σ hi* The homogeneous transformation matrix between is: hi T hi* = hi T tt T hi* .

[0093] Then, using the relative posture information between the end of the robot and the target capture point, the visual servo method can be used to complete the trajectory planning of the robot in the workspace, laying the foundation for the subsequent design of the adhesion capture controller. Define the capture posture error of the end of the i-th robot for in hi p hi* and hi θ hi* are the position and attitude angle of the target capture point relative to the end of the robotic arm. Based on the kinematic relationship of the robotic arm, combined with hi p hi* and hi θ hi* The time derivative of the expected capture posture error of the end effector in the workspace is obtained as follows: in hi R b For platform system b Relative Σ hi The coordinate transformation matrix E 3 is a 3×3 unit matrix; 0 3×3 is a 3×3 zero matrix; is the Jacobian matrix of the i-th robot; is the joint angular velocity of the i-th robot arm; T( hi θ hi* ) is the rotation direction matrix of the axis; the superscript “×” is the symbol for finding the matrix cross product antisymmetric matrix. Let the Jacobian matrix be The desired trajectory of the end effector in the workspace can be converted into the desired trajectory of each robot joint angle in the joint space. The joint angular velocity command in the joint space is: The superscript “+” in the formula is the symbol for finding the pseudo-inverse of the matrix. is the positive definite symmetric matrix to be selected.

[0094] Step 4: Use the contact force control strategy to complete the controller design for adhesion capture.

[0095] In the process of capturing a target by a dual-arm space robot, the end effectors of the two robotic arms contact the capture point on the target, which will generate complex collision contact forces. Due to the existence of errors such as measurement and control, the contact force between the end effector and the target may be relatively large. Excessive contact force can easily lead to damage to the end effector or failure to capture the target. In order to reduce the impact of the physical contact between the end effector and the target contact point on the capture stage, the present invention adds an adhesion capture process in the early stage of capture. During the adhesion process, a relatively small contact force is maintained between the end effector and the target so that the end of the robotic arm is always maintained at a relatively close distance to the target contact point. Under the action of adhesion, since the relative motion between the end effector and the target is small, the maximum contact force and contact torque generated at the capture moment are also relatively small, which can avoid contact force saturation and damage to the end effector. The contact force control method is used to complete the controller design in adhesion capture. The control block diagram is shown in the figure. Figure 6 shown.

[0096] The expected positions and angular velocities of the two robot end effectors relative to the platform are defined as and Then the control law of the force control loop can be designed as: In the formula, and is the expected contact force and torque at the end of the robot, both described in the end effector system, f h and τ h are the measured values ​​of contact force and torque, all described under the end effector system; and is the desired speed and angular velocity of the end of the manipulator under force control, all described in the end effector system; K is the control gain matrix, the subscript t represents translation, and o represents rotation. When the contact force is less than the expected value, the above control law will cause the end of the manipulator to move in the contact direction, thereby increasing the contact force and gradually making it equal to the expected value.

[0097] The robot arm motion controller used for the force controller can be designed as: In the formula, b P h and b ω h K is the actual position and angular velocity of the two robot end effectors relative to the platform; Dp , K Pp , K Do and KPo They are all control gain matrices; The attitude error is defined as: In the formula, b x h , b y h and b z h is the coordinate transformation matrix of the end effector system of the two manipulators relative to the platform system b R h The amount of and is the desired coordinate transformation matrix of the end effector system of the two manipulators relative to the platform system The specific relationship is: b x h b y h b z h ]= b R h ,

[0098] The acceleration and angular acceleration of the end effector relative to the platform can be obtained by redundant decomposition of the acceleration level to obtain the joint angular acceleration for: In the formula, J m is the geometric Jacobian matrix of the robot,

[0099] According to the dynamic equation of the dual-arm space robot system derived in step 2, when the contact force and contact torque at the end of the robot arm are considered, the dynamic model of the robot arm with a fixed base can be written as: Using the inverse dynamics control method of the robot arm, the robot arm joint control torque command can be obtained as: In the formula,

[0100] Step 5: Verify the effectiveness of the dual-arm space robot's adhesion capture through closed-loop numerical simulation.

[0101] According to the system kinematics and dynamics model established in step 2, the autonomous trajectory planning algorithm and adhesion capture controller designed in steps 3 and 4 are used to simulate the space debris removal task in aerospace engineering applications, and the closed-loop numerical simulation is completed for the process of a dual-arm space robot capturing a six-degree-of-freedom single rigid body target. By analyzing the closed-loop simulation results, if the capture position and attitude errors of the two robotic arms can converge to near zero, it proves that the designed adhesion capture control is effective.

[0102] In order to facilitate understanding of the above technical solutions of the present invention, the above technical solutions of the present invention are described in detail below through specific embodiments.

[0103] Example

[0104] Taking a free-floating dual-arm space robot system and a six-degree-of-freedom moving target as research objects, the target capture of the dual-arm space robot is analyzed to verify the effectiveness of the method of the present invention.

[0105] The platform of the dual-arm space robot system is a cube with a side length of 2m, a mass of 3000kg, and a moment of inertia of 2000kg·m on all three axes. 2 , without considering the center of mass deviation. Both robotic arms are equipped with 7 arms, each of which can be regarded as a cylindrical homogeneous solid rod.

[0106] In step 2, the structures and mass parameters of the two robotic arms are the same, as shown in Table 1. The two robotic arms are installed on the +z plane of the platform, along Σ b The x-axis is symmetrical, and the root installation positions are [-1 0.85 1] T m and [-1 -0.85 1] T m. The geometric parameters and mass characteristic parameters of the target star are consistent with the platform of the dual-arm space robot system. The two capture points on the target are located at Σ t The position in is set to [0 0.6 -1] T m and [0 -0.6 -1] T m.

[0107] Table 1 Structural and quality characteristic parameters of each robot arm

[0108]

[0109] In step 3, the control gain matrix to be determined can be selected as

[0110] In step 4, the expected contact force and contact torque of the end of the robot are selected as 5N and 0Nm respectively. The thresholds of the adhesion stage and the capture stage are defined as σ i (i=1,2) and η i (i=1,2). When the capture posture error of the end of the i-th robot arm is satisfy When satisfy When , the system ends the sticking stage and starts to capture. The initial value of the system state in the capture stage is the final value of the system state in the sticking stage. The sticking threshold and the capture threshold are selected as σ i=[0.1 0.1 0.1 5 5 5] T (i=1,2) and η i =[0.03 0.03 0.03 1 1 1] T (i=1,2).

[0111] Through Matlab closed-loop numerical simulation, the motion process of the dual-arm space robot adhering to and capturing the moving target is obtained, such as Figure 7 As shown in Figure 2. At t = 8.4s, the dual-arm space robot system was close to the target capture point and began to adhere. At t = 17s, the adhesion ended and the capture began. Both robotic arms were able to successfully capture the two capture points on the target, and the target did not escape. The position and posture errors of the two robotic arms are shown in Figure 2. Figure 8 and Fig. 9 As shown in Figure 2, the capture posture errors of the two manipulators can converge to near zero within 20 seconds, verifying that both manipulators can successfully capture the target. The contact force and contact torque at the ends of the two manipulators are respectively Fig.10 and Fig.11 As shown in the figure, the end effector is subjected to a smaller contact force and torque during the adhesion stage. At this time, the end effector is close to the target contact point and the relative motion is small. Therefore, the maximum contact force and contact torque at the capture moment are relatively small, avoiding the risk of contact force saturation and damage to the end of the robot arm. The joint angles and joint angular velocities of the two robot arms are shown in Figure 1. Fig.12 and Fig.13 As shown in the figure, both are within a reasonable range, and there is no problem of singularity of the robotic arm. In order to verify the influence of the adhesion process on the capture of the target by the dual-arm space robot, a group of simulation experiments without considering adhesion in the capture control was selected as the control group. The comparison results of the capture position and posture error of the two robotic arms are shown in the figure below. Fig.14 and Fig.15 As shown in the figure, it can be seen that considering adhesion can significantly reduce the grasping error of the robot arm, thereby verifying the superiority of the designed adhesion grasping control.

[0112] In summary, the present invention provides a dual-arm space robot adhesion capture control method, that is, before the two mechanical arms formally capture the moving target, the adhesion contact force control strategy is first used to maintain a relatively small contact force between the end effector and the target, so that the end of the mechanical arm is always maintained at a relatively close distance to the target contact point, and the capture is performed when the relative movement between the mechanical arm and the target is small. This method can avoid the risk of target escape, and effectively improve the compliant control performance of the dual-arm space robot in capturing debris targets, avoid contact force saturation and damage to the end of the mechanical arm. It has important theoretical research significance and engineering application value for my country's space debris removal mission, can reduce the threat of debris impact to on-orbit spacecraft, and improve the safety of the space environment.

[0113] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A dual-arm space robot adhesion capture control method, characterized in that: The dual-arm space robot adhesion and capture control method is used for a dual-arm space robot system, the dual-arm space robot system comprises a dual-arm space robot platform (1), a first space robot arm (2) and an end effector (4) thereof, a second space robot arm (3) and an end effector (5) thereof, and the dual-arm space robot adhesion and capture control method comprises the following steps: Step 1: Propose the concept of adhesion and design the adhesion grasping method of the dual-arm space robot; Step 2, establish a coordinate system and complete the dynamic modeling of the dual-arm space robot; Step 3, design an autonomous path planning algorithm in adhesion capture; Step 4, using the contact force control strategy to complete the controller design of adhesion capture; Step 5: Closed-loop numerical simulation to verify the effectiveness of dual-arm adhesion capture.

2. The dual-arm space robot adhesion capture control method according to claim 1, characterized in that: In the step 1, the adhesion refers to the process of causing the end effector of the robot arm to move with the target for a period of time before performing the capture.

3. The dual-arm space robot adhesion capture control method according to claim 2, characterized in that: In step 1, the dual-arm space robot adhesion capture method includes: by driving the joints of the robotic arms, a micro contact force that can be adjusted autonomously is maintained between the end effector of each robotic arm and the target, so that the end effector is always maintained near the contact point of the target corresponding to it.

4. The dual-arm space robot adhesion capture control method according to claim 1, characterized in that: In step 2, it is assumed that the i-th (i=1,2) mechanical arm of the dual-arm space robot has n i (i=1,2) arms, each of which is connected by a single-degree-of-freedom rotation joint; Establish coordinate system: The platform system of the dual-arm space robot is Σ b , whose origin is located at the center of mass of the space robot platform; the target system is Σ t , whose origin is at the target mass center; the rod coordinate system Σ i,j The origin is located on the axis of the jth joint of the i-th robot arm, which is fixed to the j-th arm rod; the rod reference coordinate system The origin of the coordinate system is located on the axis of rotation of the jth joint of the i-th robot arm. With Σ i,j The z-axis of the revolute joint is aligned with the rotation axis Γ i,j The direction of the end effector is parallel to hi The origin is located at the nth i The end of a rod, used to describe the operation task; the catch point system The origin is located at the i-th capture point on the target. When the i-th robot arm completes the capture, Σ hi and Coincidence; inertial coordinate system Σ I The origin is at the center of the earth, the z-axis points to the North Pole along the earth's polar axis, the x-axis points to the vernal equinox, and the y-axis, x-axis, and z-axis form a right-handed coordinate system; Introducing the homogeneous transformation matrix A T B , which means: the homogeneous transformation matrix of coordinate system B relative to coordinate system A, let A r B and A R B are the position vector matrix and coordinate transformation matrix of coordinate system B relative to coordinate system A, respectively. Then the homogeneous transformation matrix between the two coordinate systems is A T B It can be expressed as: Where 0 1×3 =[0 0 0]; The forward kinematics equation of the dual-arm space robot can be solved by using the homogeneous transformation matrix, that is, the end effector system Σ hi Relative platform system Σ b The pose can be solved using the homogeneous transformation matrix in, b T hi is the end effector system Σ hi Relative platform system Σ b The coordinate transformation matrix, b T i,1 is the rod coordinate system Σ i,1 Relative platform system Σ b The coordinate transformation matrix, i,(j-1) T i,j is the rod coordinate system Σ i,j Relative rod coordinate system Σ i,j-1 The coordinate transformation matrix, is the end effector system Σ hi Relative rod coordinate system Σ i,ni The coordinate transformation matrix of Using Kane equation, the dynamic equation of the dual-arm space robot can be derived as follows: Among them, M b With M m are the generalized mass matrices of the platform and the two robotic arms, M bm is the coupled mass matrix of the platform and the two manipulators, and the superscript "T" is the symbol for matrix transposition; V b is the platform relative inertial system Σ I The linear velocity and angular velocity are projected on the platform system Σ b middle; is the joint angular velocity of the two robotic arms; c b With c m are the nonlinear generalized inertial forces corresponding to the platform and the two robotic arms respectively; F b is the external force on the platform b The spatial force formed is projected on Σ b τ is the joint torque of the two manipulators; J b With J m are the Jacobian matrices of the platform and the robot arm respectively; F h is the contact force / torque on the ends of the two manipulators, projected in the end effector system; similarly, the dynamic equation of the target to be captured is Among them, M t is the generalized mass matrix of the target; V t is the target relative inertial system Σ I The linear velocity and angular velocity are projected on the target system Σ t c t is the nonlinear generalized inertial force of the target; is the generalized Jacobian matrix of the target.

5. The dual-arm space robot adhesion capture control method according to claim 1, characterized in that: The step 3 comprises: Step 31, obtaining the relative position information between the end of each robotic arm and the target capture point through kinematic relationship calculation of the dual-arm space robot; Step 32, using the relative posture information between the end of the robot arm and the target capture point, the visual servo method can be used to complete the trajectory planning of the robot arm in the workspace, laying the foundation for the subsequent design of the adhesion capture controller.

6. The dual-arm space robot adhesion capture control method according to claim 5, characterized in that: The step 31 comprises: Let the target system Σ t Relative to the end effector system of the i-th robot arm Σ hi The position and posture of hi p t and hi R t , assuming that the camera center of each robot coincides with the origin of its end effector system, we can get hi p t =( I R hi ) T ( I p t - I p hi ), hi R t =( I R hi ) TI R t ,in I p t and I R t They are Σ t Relative inertial systemΣ I The position vector matrix and coordinate transformation matrix, I p hi and I R hi They are Σ hi Relative Σ I The position vector matrix and coordinate transformation matrix of the target system Σ t Relative end effector system Σ hi Homogeneous transformation matrix hi T t for: On the other hand, since the position of the capture point on the target is fixed, the capture point system Relative target system Σ t Homogeneous transformation matrix is a constant matrix; therefore, the end effector system of the i-th robot arm is Σ hi The corresponding capture point system The homogeneous transformation matrix between is:

7. The dual-arm space robot adhesion capture control method according to claim 6, characterized in that: The step 32 comprises: Define the capture posture error of the end of the i-th robotic arm for in and They are the position and attitude angle of the target capture point relative to the end of the robotic arm; based on the kinematic relationship of the robotic arm, combined with and The time derivative of the expected capture posture error of the end effector in the workspace is obtained as follows: in hi R b For platform system b Relative Σ hi The coordinate transformation matrix; E3 is the 3×3 unit matrix; 0 3×3 is a 3×3 zero matrix; is the Jacobian matrix of the i-th robot; is the joint angular velocity of the i-th robot arm; is the rotation direction matrix of the axis; the superscript "×" is the symbol for finding the matrix cross product antisymmetric matrix; let the Jacobian matrix be The desired trajectory of the end effector in the workspace can be converted into the desired trajectory of each robot joint angle in the joint space. The joint angular velocity command in the joint space is: The superscript "+" in the formula is the symbol for finding the pseudo-inverse of the matrix. is the positive definite symmetric matrix to be selected.

8. The dual-arm space robot adhesion capture control method according to claim 7, characterized in that: The step 4 comprises: The expected positions and angular velocities of the two robot end effectors relative to the platform are defined as and Then the control law of the force control loop can be designed as: In the formula, and is the expected contact force and torque at the end of the robot, both described in the end effector system, f h and τ h are the measured values ​​of contact force and torque, all described under the end effector system; and is the desired velocity and angular velocity of the end of the manipulator under force control, both described in the end effector system; K is the control gain matrix, the subscript t represents translation, and o represents rotation; When the contact force is less than the expected value, the above control law will cause the end of the robot arm to move in the contact direction, thereby increasing the contact force and gradually making it equal to the expected value; The robot arm motion controller used for the force controller can be designed as: In the formula, b P h and b ω h K is the actual position and angular velocity of the two robot end effectors relative to the platform; Dp , K Pp , K Do and K Po They are all control gain matrices; The attitude error is defined as: In the formula, b x h , b y h and b z h is the coordinate transformation matrix of the end effector system of the two manipulators relative to the platform system b R h The amount of and is the desired coordinate transformation matrix of the end effector system of the two manipulators relative to the platform system The specific relationship is: b x hb y hb z h ]= b R h , The acceleration and angular acceleration of the end effector relative to the platform, and the joint angular acceleration are obtained by redundant decomposition of the acceleration level for: In the formula, J m is the geometric Jacobian matrix of the robot, According to the dynamic equation of the dual-arm space robot system derived in step 2, when the contact force and contact torque at the end of the robot arm are considered, the dynamic model of the robot arm with a fixed base is written as: Using the inverse dynamics control method of the robot arm, the robot arm joint control torque command can be obtained as: In the formula, 9. The dual-arm space robot adhesion capture control method according to claim 8, characterized in that: The step 5 includes: according to the system kinematics and dynamics model established in step 2, using the autonomous trajectory planning algorithm and adhesion capture controller designed in steps 3 and 4, simulating the space debris removal task in aerospace engineering applications, and completing a closed-loop numerical simulation of the process of a dual-arm space robot capturing a six-degree-of-freedom single rigid body target; by analyzing the closed-loop simulation results, if the capture position and posture errors of the two robotic arms can converge to near zero, it is proved that the designed adhesion capture control is effective.

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