Integrated torso height and posture constraint dual-arm space robot inverse kinematics solving method

Abstract

A method for solving the inverse kinematics of a dual-arm space robot integrating torso height and posture constraints is disclosed, relating to the field of space robot technology. The process is as follows: establishing a geometry-based kinematic model of the dual-arm space robot; establishing a virtual torso position formula; calculating the virtual torso pose based on torso height and posture constraints; converting the desired pose of the mobile end into the desired poses of each individual arm; and calling a single-branch arm inverse kinematics solver to calculate and integrate joint angles. By transforming the torso height and posture constraint problem into two unconstrained single-arm inverse kinematics problems, the dimensionality of the problem is reduced. Parallel computing strategies can be employed, allowing the torso and spatial mechanisms to adjust their posture while maintaining a safe height during task execution, reducing disturbances to the robot and spatial mechanisms, and enabling more flexible acquisition of task-site image information via a torso camera.

Description

Technical Field

[0001] This invention relates to the field of space robot technology, specifically a method for solving the inverse kinematics of a dual-arm space robot that integrates torso height and posture constraints. Background Technology

[0002] When dual-arm space robots perform on-orbit assembly or maintenance tasks on large space platforms, they need to perform actions such as bi-arm handling and crawling. This can cause disturbances to the large space platform, and if left uncontrolled, it can increase the danger of performing on-orbit tasks. By controlling the height and posture of the dual-arm space robot's torso, the disturbances to the large space platform caused by the robot's movement can be reduced. In addition, by controlling the posture of the torso, the cameras on the torso can obtain a better field of view, thereby assisting in the successful execution of the task.

[0003] However, existing inverse kinematics methods are difficult to directly apply height and posture constraints to the torso. Therefore, there is an urgent need for an inverse kinematics solution method for dual-arm space robots that integrates torso height and posture constraints to improve the safety and reliability of dual-arm space robots when performing on-orbit tasks. Summary of the Invention

[0004] To address the shortcomings of the prior art, this invention provides a method for solving the inverse kinematics of a dual-arm space robot that integrates torso height and posture constraints. This method transforms the torso height and posture constraint problem into two unconstrained single-arm inverse kinematics problems, reducing the dimensionality of the problem and enabling the use of parallel computing strategies. This allows the torso and space mechanism to adjust the torso posture while maintaining a safe height during task execution, reducing disturbances to the robot and space mechanism, and more flexibly acquiring task site image information through the torso camera.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for solving the inverse kinematics of a dual-arm space robot integrating torso height and posture constraints, comprising the following steps:

[0006] Step 1: Establish a geometry-based kinematic model for the dual-arm space robot

[0007] Define a world coordinate system {O}. Establish a virtual torso coordinate system at the geometric center of the torso. Assign the two branch arms armma and armb, respectively. Establish the base coordinate system and end-effector coordinate system for the two branch arms. The poses of the end-effector coordinate systems of armma and armb and the virtual torso coordinate system under the world coordinate system {O} are as follows: and as well as Represented as: in, and Let x, y, and z represent the x, y, and z axis vectors of the end coordinate system of Arma, respectively. Represents the position vector of the end coordinate system of Arma. and Let x, y, and z represent the x, y, and z axis vectors of the end coordinate system of armb, respectively. This represents the position vector of the end coordinate system of armb. and Let x, y, and z represent the vectors of the virtual torso coordinate system, respectively. Represents the position vector of the virtual torso coordinate system;

[0008] Step 2: Establish the virtual position formula for the torso

[0009] The geometric center of the torso of the dual-arm space robot is located at the midpoint P of the line connecting the ends of the two branch arms. mide Directly above, define n ab Let n be the vector connecting the ends of the two branch arms. p for and If the plane normal vector formed is P, then P mide point to vector The unit vector is but Where h vtorso for Relative to the height of the line connecting the ends of the two branch arms, Composed of in, and They represent Position on the x, y, and z axes;

[0010] Step 3: Calculate the virtual pose of the torso based on torso height and posture constraints.

[0011] The input torso height constraint is h. abs The input torso posture constraint is and Choose ARMA or ARMB as the fixed arm, and then... abs This is represented as the value in the negative x-axis direction of the coordinate system at the end of the fixed arm. Will and P mide In the coordinate system at the end of the fixed arm, v is defined as... fixedee and in, and Let v represent the coordinates of the end of the fixed arm respectively. fixedee Positions along the x, y, and z axes, and Let P represent the coordinates of the end of the fixed arm, respectively. mide The positions along the x, y, and z axes are derived as follows: Therefore, it is possible to calculate By combining the input torso pose constraints, we can obtain

[0012] Step 4: Convert the desired pose of the mobile device into the desired pose of each arm.

[0013] The poses of the base coordinate systems of arma and armb in the world coordinate system {O} are respectively and

[0014] Let the base coordinate system of Arma be represented in the virtual torso coordinate system as follows: but The target pose of the arma end effector is: Then the pose of the ARMA endpoint in its base coordinate system

[0015] Let the base coordinate system of armb be represented in the virtual torso coordinate system as follows: but The target pose of the armb end effector is: Then the pose of the armb end in its base coordinate system

[0016] Step 5: Call the single-branch arm inverse kinematics solver to calculate joint angles and integrate them.

[0017] Will and Substitute the values ​​into the single-branch arm inverse kinematics solver, use a parallel computing strategy to calculate synchronously and output the joint angles of the two branches respectively. Integrate the joint angles of the two branches to obtain the inverse kinematics solution of the dual-arm space robot that meets the specified torso height and posture constraints.

[0018] Furthermore, in step one, the x-axis of the base coordinate system is perpendicular to the side of the torso and points to the geometric center of the torso; the z-axis is parallel to the edge of the side of the torso and points in the same counterclockwise direction around the geometric center of the torso; the y-axis is determined according to the right-hand coordinate definition. The x-axis of the end effector coordinate system is located on the extension line and points to the outside of the end of the branch arm; the z-axis is perpendicular to the gripper tool plane of the end effector; the y-axis is determined according to the right-hand coordinate definition. The x-axis of the virtual torso coordinate system points to the base of ARMA; the y-axis is determined according to the cross product of the x-axis of the base coordinate systems of ARMA and ARMB; the z-axis is determined according to the right-hand coordinate definition.

[0019] Furthermore, in step four... and It is a constant that can be obtained through measurement.

[0020] Furthermore, in step five, the inverse kinematics solver for the single branch arm can be a Levenberg-Marquardt, Broyden-Fletcher-Goldfarb-Shanno, or a solver based on analytical methods.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. The method of the present invention enables a dual-arm space robot to apply height and posture constraints to the torso at the inverse kinematics level when performing tasks, so that the torso and the space mechanism can adjust the torso posture while maintaining a specified safe height. This can more efficiently achieve functions such as camera field of view adjustment, reduce disturbance to the space mechanism during robot movement, and obstacle avoidance, providing more flexible and reliable kinematic technology support for the robot to perform space tasks.

[0023] 2. The method of the present invention transforms the inverse kinematics problem of a dual-arm space robot with torso height and posture constraints into an unconstrained single-arm inverse kinematics problem, reducing the dimensionality of the problem solution. It also provides a modular inverse kinematics solution approach, which can flexibly replace the single-arm inverse kinematics solver with an existing or more suitable method according to different branch arm configurations. Thus, the method of the present invention can be used for dual-arm space robot platforms with different branch arm configurations.

[0024] 3. The method of the present invention decomposes the inverse kinematics problem of a dual-arm space robot integrating torso height and posture constraints into two single-arm inverse kinematics problems. It can then use a parallel computing strategy to simultaneously calculate the inverse kinematics solutions of the two branch arms, thereby effectively ensuring the real-time performance of the inverse kinematics calculation of the dual-arm space robot. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method of the present invention;

[0026] Figure 2 This is a schematic diagram of the kinematic model of the dual-arm space robot in the method of this invention;

[0027] Figure 3 This is a schematic diagram of a simulated scenario of the dual-arm space robot performing a task in the method of this invention. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] like Figures 1-3 As shown, a method for solving the inverse kinematics of a dual-armed space robot integrating torso height and posture constraints is presented, with the specific process combined with... Figure 1 As shown, it includes the following steps:

[0030] Step 1: Establish a geometry-based kinematic model for the dual-arm space robot

[0031] The dual-arm space robot consists of a torso and two branch arms, based on a geometric approach, combined with... Figure 2 As shown, let {O} be the world coordinate system, and the two branch arms be designated as arma and armb, respectively. Base coordinate systems are established at the connection points between the two branch arms and the torso, where the x-axis is perpendicular to the torso's side surface and points towards the torso's geometric center; the z-axis is parallel to the torso's side surface edge and points in the same counter-clockwise direction around the torso's geometric center; and the y-axis is determined according to the right-hand coordinate definition. The poses of arma and armb in the base coordinate systems under the world coordinate system {O} are respectively represented as follows: and Establish end-effector coordinate systems for the two branch arms at their respective end effectors, away from the torso. The x-axis lies on its extension line pointing outwards from the end of the branch arm; the z-axis is perpendicular to the gripper tool plane of the end effector; and the y-axis is determined according to the right-hand coordinate system definition. The end-effector poses of arma and armb in the world coordinate system {O} are respectively represented as follows: and A virtual torso coordinate system is established at the geometric center of the torso, where the x-axis points to the base of arma, the y-axis is determined according to the cross product of the x-axis of the base coordinate systems of arma and armb, and the z-axis is determined according to the right-hand coordinate definition. The pose of the virtual torso coordinate system under the world coordinate system {O} is represented as follows: It refers to the pose representation after the actual torso pose is offset to the center plane of the torso.

[0032] but and It is expressed as follows:

[0033]

[0034]

[0035] In the formula, and Let x, y, and z be the vectors of the terminal coordinate system of ARMA in the world coordinate system {O}, respectively. This represents the position vector of the terminal coordinate system of ARMA in the world coordinate system {O}. and Let x, y, and z be the x, y, and z axis vectors of the end coordinate system of armb in the world coordinate system {O}, respectively. This represents the position vector of the end coordinate system of armb in the world coordinate system {O}. and Let x, y, and z be the vectors of the virtual torso coordinate system under the world coordinate system {O}, respectively. This represents the position vector of the virtual torso coordinate system under the world coordinate system {O}.

[0036] Step 2: Establish the virtual position formula for the torso

[0037] Define n ab Let P be the vector connecting the ends of the two branch arms. mide Let P be the midpoint of the line connecting the ends of the two branch arms, so that the geometric center of the torso of the dual-arm space robot is located at P. mide Directly above:

[0038]

[0039] Let n p for and If the plane normal vector is formed, then:

[0040]

[0041] By P mide point to vector It is expressed as follows:

[0042]

[0043] definition for If the unit vector is , then It can be represented as:

[0044]

[0045] Here h vtorso for Relative to the height of the line connecting the ends of the two branch arms, Composition is as follows:

[0046]

[0047] In the formula, and Representing the world coordinate system {O} Position on the x, y, and z axes.

[0048] Step 3: Calculate the virtual pose of the torso based on torso height and posture constraints.

[0049] Define the input torso height constraint as h abs This refers to the height constraint of the torso relative to the space mechanism platform. The input torso posture constraint is given by formula (3). and

[0050] In a dual-arm space robot, the two branch arms move and remain stationary alternately during crawling, therefore... and Both may remain in a fixed state. Choose either arma or armb as the fixed arm, and place h... abs This is represented as the value in the negative x-axis direction of the coordinate system at the end of the fixed arm.

[0051] Based on the actual crawling situation, the pose values ​​of the end coordinate system of the fixed arm are determined. Perform pose transformation, let Let the pose of the world coordinate system {O} in the end-effector coordinate system of the fixed arm be represented. Then:

[0052]

[0053] Will In the coordinate system at the end of the fixed arm, it is defined as v fixedee ,but:

[0054]

[0055] In the formula, and Let v represent the coordinates of the end of the fixed arm respectively. fixedee Position on the x, y, and z axes.

[0056] Further P mide This also means that in the coordinate system at the end of the fixed arm, it is defined as... but:

[0057]

[0058] In the formula, and Let P represent the coordinates of the end of the fixed arm, respectively. mide Position on the x, y, and z axes.

[0059] According to the following formula:

[0060]

[0061] It can be found that:

[0062]

[0063] In the formula, To represent the coordinate system at the end of the fixed arm

[0064] Then, by calculating according to formula (7), we can obtain the result. At the same time, combined with the input torso posture constraints and The result can be obtained by calculating according to formula (3).

[0065] Step 4: Convert the desired pose of the mobile device into the desired pose of each arm.

[0066] Let the base coordinate system of Arma be represented in the virtual torso coordinate system as follows: It is a constant that can be obtained through measurement; the target pose at the ARMA endpoint is... The pose of the ARMA endpoint in its base coordinate system can be determined. It is expressed as follows:

[0067]

[0068] Let the base coordinate system of armb be represented in the virtual torso coordinate system as follows: It is a constant that can be obtained through measurement; the target pose of the armb end effector is... The pose of the armb end effector in its base coordinate system can be determined. It is expressed as follows:

[0069]

[0070] Step 5: Call the single-branch arm inverse kinematics solver to calculate joint angles and integrate them.

[0071] Will and Substituting the values ​​into the Levenberg-Marquardt single-branch arm inverse kinematics solver, a parallel computing strategy is employed for synchronous computation. By fully utilizing the computing performance of the current hardware platform, the computation time cost of the inverse kinematics of the two branches is compressed to a level comparable to that of the single branch arm. The single-branch arm inverse kinematics solver is embedded into the method of this invention in a modular manner, and can be replaced with different solvers (such as the Broyden-Fletcher-Goldfarb-Shanno solver or a solver based on analytical methods) depending on the working scenario and branch arm configuration. The single-branch arm inverse kinematics solver will output the joint angles of the two branches separately. According to the task requirements, the joint angles of the two branches are integrated into the data format specified by the selected solver to obtain the inverse kinematics solution of the dual-arm space robot that meets the specified torso height and posture constraints.

[0072] In summary, the method of this invention enables a dual-armed space robot to apply height and attitude constraints to its torso at the inverse kinematics level when performing tasks, simulating the state scenarios of a dual-armed space robot performing tasks, combined with... Figure 3 As shown, by applying height and posture constraints to the torso, the torso and spatial mechanism can adjust the torso posture while maintaining a specified safe height, so as to facilitate the adjustment of the field of view of the torso camera. It also helps to reduce the disturbance to the spatial mechanism during robot movement and the obstacle avoidance function, providing more flexible and reliable kinematic technology support for the robot to perform spatial tasks.

[0073] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0074] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for solving the inverse kinematics of a dual-armed space robot integrating torso height and posture constraints, characterized in that: Includes the following steps: Step 1: Establish a geometry-based kinematic model for the dual-arm space robot Define a world coordinate system {O}. Establish a virtual torso coordinate system at the geometric center of the torso. Assign the two branch arms armma and armb, respectively. Establish the base coordinate system and end-effector coordinate system for the two branch arms. The poses of the end-effector coordinate systems of armma and armb and the virtual torso coordinate system under the world coordinate system {O} are as follows: and as well as Represented as: in, and Let x, y, and z represent the x, y, and z axis vectors of the end coordinate system of Arma, respectively. Represents the position vector of the end coordinate system of Arma. and Let x, y, and z represent the x, y, and z axis vectors of the end coordinate system of armb, respectively. This represents the position vector of the end coordinate system of armb. and Let x, y, and z represent the vectors of the virtual torso coordinate system, respectively. Represents the position vector of the virtual torso coordinate system; Step 2: Establish the virtual position formula for the torso The geometric center of the torso of the dual-arm space robot is located at the midpoint P of the line connecting the ends of the two branch arms. mide Directly above, define n ab Let n be the vector connecting the ends of the two branch arms. p for and If the plane normal vector formed is P, then P mide point to vector The unit vector is but Where h vtorso for Relative to the height of the line connecting the ends of the two branch arms, Composed of in, and They represent Position on the x, y, and z axes; Step 3: Calculate the virtual pose of the torso based on torso height and posture constraints. The input torso height constraint is h. abs The input torso posture constraint is and Choose ARMA or ARMB as the fixed arm, and then... abs This is represented as the value in the negative x-axis direction of the coordinate system at the end of the fixed arm. Will and P mide In the coordinate system at the end of the fixed arm, v is defined as... fixedee and in, and Let v represent the coordinates of the end of the fixed arm respectively. fixedee Positions along the x, y, and z axes, and Let P represent the coordinates of the end of the fixed arm, respectively. mide The positions along the x, y, and z axes are derived as follows: Therefore, it is possible to calculate By combining the input torso pose constraints, we can obtain Step 4: Convert the desired pose of the mobile device into the desired pose of each arm. The poses of the base coordinate systems of arma and armb in the world coordinate system {O} are respectively and Let the base coordinate system of Arma be represented in the virtual torso coordinate system as follows: but The target pose of the arma end effector is: Then the pose of the ARMA endpoint in its base coordinate system Let the base coordinate system of armb be represented in the virtual torso coordinate system as follows: but The target pose of the armb end effector is: Then the pose of the armb end in its base coordinate system Step 5: Call the single-branch arm inverse kinematics solver to calculate joint angles and integrate them. Will and Substitute the values ​​into the single-branch arm inverse kinematics solver, use a parallel computing strategy to calculate synchronously and output the joint angles of the two branches respectively. Integrate the joint angles of the two branches to obtain the inverse kinematics solution of the dual-arm space robot that meets the specified torso height and posture constraints.

2. The method for solving the inverse kinematics of a dual-arm space robot integrating torso height and posture constraints according to claim 1, characterized in that: In step one, the x-axis of the base coordinate system is perpendicular to the side of the torso and points to the geometric center of the torso; the z-axis is parallel to the edge of the side of the torso and points in the same counterclockwise direction around the geometric center of the torso; the y-axis is determined according to the right-hand coordinate definition. The x-axis of the end effector coordinate system is located on the extension line and points to the outside of the end of the branch arm; the z-axis is perpendicular to the gripper tool plane of the end effector; the y-axis is determined according to the right-hand coordinate definition. The x-axis of the virtual torso coordinate system points to the base of ARMA; the y-axis is determined according to the cross product of the x-axis of the base coordinate systems of ARMA and ARMB; the z-axis is determined according to the right-hand coordinate definition.

3. The method for solving the inverse kinematics of a dual-arm space robot integrating torso height and posture constraints according to claim 1, characterized in that: In step four and It is a constant that can be obtained through measurement.

4. The method for solving the inverse kinematics of a dual-arm space robot integrating torso height and posture constraints according to claim 1, characterized in that: In step five, the inverse kinematics solver for the single branch arm can be Levenberg-Marquardt, Broyden-Fletcher-Goldfarb-Shanno, or a solver based on analytical methods.

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