A space robot arm precision evaluation device and evaluation method

Abstract

A device and method for evaluating the accuracy of a space robotic arm are disclosed. The device includes a simulation wall, a floating shoulder support, a floating elbow support, a floating wrist support, a theodolite, a static target, a laser tracker, and a dynamic target. The simulation wall is fixed to a base to keep the base of the robotic arm stationary. The floating shoulder, elbow, and wrist supports are connected to the shoulder, elbow, and wrist of the robotic arm, respectively, providing a zero-gravity testing environment. The theodolite is used to measure the installation errors of each component of the robotic arm and the static positioning accuracy of the end effector through the static target. During the movement of the robotic arm, the laser tracker is used to measure the accuracy of the end effector's trajectory through the dynamic target. The end effector accuracy is evaluated. The equivalent single-joint error is calculated by comprehensively analyzing the robotic arm errors, and the end effector pose accuracy of the space robotic arm's on-orbit three-dimensional mission configuration is evaluated using a forward error analysis model. This invention ensures the consistency of the space robotic arm's end effector accuracy test results between space and ground.

Description

Technical Field

[0001] This invention relates to an apparatus and method for assessing the accuracy of a space robotic arm. Technical Background

[0002] Accuracy of space robotic arms is a crucial indicator for ensuring their safe on-orbit operation. Currently, the accuracy assessment methods for space robotic arms that have been successfully deployed in orbit, such as the Canadian robotic arm, mainly employ static accuracy analysis methods, with limited assessment of dynamic accuracy during the end-effector's movement. Furthermore, due to limitations imposed by air-bearing fixtures, the measurement configurations are all planar motion configurations, covering only two-dimensional motion. This results in poor real-time dynamic performance during testing and makes it impossible to achieve three-dimensional spatial motion accuracy assessment. Summary of the Invention

[0003] The technical problem solved by this invention is to address issues such as the setup of the overall testing environment for space robotic arms, real-time accuracy testing during the assembly process, overall arm accuracy testing, and accuracy evaluation of the three-dimensional mission configuration in space. This invention provides a device and method for accuracy evaluation of space robotic arms, ensuring the consistency of accuracy test results for the end effector of the space robotic arm between the ground and space.

[0004] The technical solution of the present invention is:

[0005] A precision evaluation device for a space robotic arm includes a simulation wall, a floating shoulder support, a floating elbow support, a floating wrist support, a theodolite, a static target, a dynamic target, and a laser tracker.

[0006] The simulated wall is fixed to the base and used to fix the root of the robotic arm;

[0007] The shoulder floating support is used to support the robotic arm's shoulder, providing a zero-gravity testing environment for the robotic arm's shoulder; the elbow floating support is used to support the robotic arm's elbow, providing a zero-gravity testing environment for the robotic arm's elbow; and the wrist floating support is used to support the robotic arm's wrist, providing a zero-gravity testing environment for the robotic arm's wrist.

[0008] Static targets are installed on the shoulder, elbow, and wrist of the robotic arm; a dynamic target is installed on the wrist of the robotic arm.

[0009] Theodolites are used to observe static targets mounted on the shoulder, elbow, and wrist of a robotic arm, and to obtain the installation errors of the shoulder, elbow, and wrist components of the robotic arm, as well as the position and attitude of the end effector of the entire arm.

[0010] The laser tracker measures the motion trajectory of the robotic arm's end effector in real time using a dynamic target mounted on the wrist of the robotic arm.

[0011] The method for evaluating the accuracy of a space robotic arm using the aforementioned space robotic arm accuracy evaluation device includes:

[0012] During the assembly of the robotic arm, a theodolite is used to observe the static targets installed on the shoulder, elbow, and wrist of the robotic arm to obtain the installation errors of the shoulder, elbow, and wrist components, thereby obtaining the length of the robotic arm and the joint deflection angle. If the length of the robotic arm and the joint deflection angle do not meet the requirements, the assembly and adjustment are repeated until the requirements are met.

[0013] After the robotic arm has moved to its final position and come to rest, a theodolite is used to observe the static target mounted on the wrist of the robotic arm to obtain the position and attitude of the entire end effector. This is then compared with the theoretically planned position and attitude to obtain the static pose accuracy Δe of the robotic arm. sp ;

[0014] During the movement of the robotic arm, a laser tracker is used to measure the trajectory of the robotic arm's end effector in real time through a dynamic target mounted on the wrist of the robotic arm. The dynamic trajectory tracking accuracy Δe of the robotic arm is obtained by comparing it with the theoretical trajectory. dp ;

[0015] Static pose accuracy Δe is calculated using a data weighting method. sp and dynamic trajectory tracking accuracy Δe dp Data fusion processing is performed to obtain the end effector accuracy Δe of the robotic arm. p ;

[0016] Assuming that the parameter errors of all joints of the robotic arm are equal, based on the robotic arm's end effector accuracy Δe p Based on the error model of the robotic arm, the equivalent single-joint error is inferred; the end-effector pose accuracy of the space robotic arm in the on-orbit three-dimensional mission configuration is evaluated based on the equivalent single-joint error and the forward error analysis model.

[0017] Preferably, the end effector accuracy Δe of the robotic arm p satisfy

[0018] Δe p =ρ1×Δe sp +ρ2×Δe dp

[0019] In the formula, ρ1 and ρ2 represent the static pose accuracy Δe of the end effector of the space robot. sp and dynamic trajectory tracking accuracy Δe dp The weighting coefficients.

[0020] Preferably, a positive error analysis model for the end effector of the robotic arm is formed by accumulating the errors of each joint.

[0021] Preferably, the end-effector error caused by joint i is relative to the error model Δe of joint i-1. i =[dx i dy i dz i δx i δyi δz i ] T δx represents the positional error at the end of joint i. i ,δy i ,δz i This represents the attitude error at the end of joint i.

[0022] The preferred forward error analysis model for the space robotic arm is shown below:

[0023]

[0024] In the formula, Δe p =[dx dy dz δx δy δz] T , where dx, dy, dz represent the end-effector position accuracy of the space robot under a specific combination of kinematic parameters, and δx, δy, δz represent the end-effector attitude accuracy of the space robot under a specific combination of kinematic parameters;

[0025] The generalized coordinate transformation matrix represents the end effector of the robotic arm joint i relative to the base;

[0026] Δq i Indicates joint parameter error;

[0027] K i Let represent the error coefficient matrix of joint i.

[0028] Preferred,

[0029] The generalized coordinate transformation matrix between joint i and joint i-1 of the robotic arm is:

[0030]

[0031] Where, θ i Let X be the joint angle of joint i, i = 1, 2, ..., 7, and let X be the three coordinate axes of joint i. i Axis, Y i Axis, Z i Axis; α i For X i The axis is Z i-1 Axis rotates to Z i The deflection angle of the axis; β i To wrap around Y i The axis is Z i-1 Axis rotates to Z i The deflection angle of the axis; d i This refers to the relative position of the links between adjacent joints; a iis the common normal distance between adjacent joints; c is the abbreviation of the cosine function, and s is the abbreviation of the sin function.

[0032] Preferably, the axis is parallel to the joint d i =0, axis non-parallel joint β i It is 0.

[0033] Preferred,

[0034]

[0035] Preferably, Δq i =[Δθ i Δd i Δa i Δαi Δβ i ] T , Δθ i Let Δd be the change in joint angle of joint i. i Δa represents the relative positional change of the connecting rods between adjacent joints. i Let Δα be the change in the common normal distance of the connecting rod. i For X i The axis is Z i-1 Axis rotates to Z i The change in the deflection angle of the axis, Δβ i To wrap around Y i The axis is Z i-1 Axis rotates to Z i The change in the axis's deflection angle.

[0036] The advantages of this invention compared to the prior art are as follows:

[0037] (1) Based on the static and dynamic measurement results of two-dimensional planar motion, this invention uses a data weighting method to perform data fusion processing, and uses the comprehensive error of the robotic arm to back-calculate the equivalent single joint error. Finally, it evaluates the end pose accuracy of the on-orbit three-dimensional mission configuration of the space robotic arm through positive error analysis, which solves the problem of accuracy evaluation of the on-orbit three-dimensional mission configuration of the space robotic arm system and ensures the consistency of the on-orbit end accuracy index test between space and ground.

[0038] (2) This invention overcomes the shortcomings of existing robotic arm precision testing and evaluation technologies. It comprehensively considers environmental simulation, static positioning accuracy and dynamic accuracy, enabling the robotic arm precision evaluation to cover any three-dimensional configuration of on-orbit missions. It can realize real-time and accurate evaluation of the end-effector precision of space robotic arms, improve the collision avoidance safety of robotic arm movement, and the accuracy of the evaluation results has been verified by my country's space robotic arm in on-orbit flight. Attached Figure Description

[0039] Figure 1 This is a layout diagram of the ground accuracy test for the space robotic arm, which is the subject of this invention patent.

[0040] Figure 2 This is a flowchart of the end-effector accuracy evaluation process for the three-dimensional task configuration of the space robotic arm, which is the subject of this invention patent. Detailed Implementation

[0041] like Figure 1 As shown, this invention provides a method for constructing, accurately testing, and evaluating a zero-gravity testing environment for a space robotic arm. The layout of this zero-gravity testing environment includes a simulation wall 11, a shoulder floating support 12, an elbow floating support 13, a wrist floating support 14, a theodolite 21, a static target 21, a laser tracker 31, and a dynamic target 32. The simulation wall 11 is fixed to the base, keeping the base of the robotic arm fixed and providing sufficient support rigidity. The shoulder floating support 12, elbow floating support 13, and wrist floating support 14 are connected to the shoulder, elbow, and wrist of the robotic arm, respectively, providing a zero-gravity testing environment.

[0042] Figure 2 This invention patent presents a flowchart for evaluating the end-effector accuracy of a three-dimensional task configuration of a spatial robotic arm. During the robotic arm assembly process, a theodolite 21 is used to measure the installation errors between various components of the robotic arm through static targets 22 mounted on the shoulder, elbow, and wrist, thereby obtaining kinematic parameters such as the arm length and joint angles. If the measured parameters do not meet the assembly requirements, repeated adjustments can be made until they are met. When the robotic arm is in its stationary state after movement, the theodolite 21 can be used to measure the end-effector position and posture of the entire arm through the static target 22 mounted on the wrist. By comparing this with the theoretically planned position and posture, the static pose accuracy Δe of the robotic arm is obtained. sp During the movement of the robotic arm, a laser tracker 31 is used to measure and acquire the end effector's motion trajectory in real time through a dynamic target 32 ​​mounted on the wrist. The dynamic trajectory tracking accuracy Δe of the robotic arm is obtained by comparing it with the theoretical motion trajectory. dp To improve the safety of the robotic arm in performing tasks, a data weighting method is used to evaluate the static pose accuracy Δe, which is related to both static positioning accuracy and motion trajectory accuracy. sp and dynamic trajectory tracking accuracy Δe dp Data fusion processing is performed to improve the accuracy Δe of the robotic arm's end effector. p A comprehensive evaluation is conducted. In this case, the weighting coefficients for static accuracy and dynamic accuracy are each set to 0.5. Different weighting ratios can be set for different task speeds and load conditions. Then, all modular joint parameter errors are set to be consistent. The equivalent error of a single joint is calculated by comprehensively analyzing the inverse error of the robotic arm. Finally, the end pose accuracy of the space robotic arm in the on-orbit three-dimensional task configuration is evaluated by using a forward error analysis model.

[0043] The forward error analysis model for the space robotic arm is shown below:

[0044] First, a generalized coordinate transformation matrix is ​​established. Based on the order of translation and rotation matrices, a rotation-then-translation approach is adopted for modeling.

[0045] Establish the generalized coordinate transformation matrix between joint i and joint i-1 of the robotic arm. as follows:

[0046]

[0047] Where, θ i Let X be the joint angle (the angle between the normals of the two links) of joint i, i = 1, 2, ..., 7; the three coordinate axes of joint i are denoted as X. i Axis, Y i Axis, Z i Axis; α i For X i The axis is Z i-1 Axis rotates to Z i The deflection angle of the axis; β i To wrap around Y i The axis is Z i-1 Axis rotates to Z i The deflection angle of the axis; d i This refers to the relative position of the links between adjacent joints; a i The distance between the common normals of the links between adjacent joints is defined as d, and the axis is parallel to the joint. i =0, axis non-parallel joint β i =0; c is the abbreviation for cosine function, s is the abbreviation for sinine function; Rot is the rotation matrix, Tran is the translation matrix.

[0048] Based on the definition of end effector error of a robotic arm, the error model of joint i relative to joint i-1 is obtained as follows:

[0049]

[0050] Where Δ i Let be the kinematic differential transformation matrix, denoted as:

[0051]

[0052] Where dx i ,dy i ,dz i δx represents the positional error at the end of joint i. i ,δy i ,δz i This represents the attitude error at the end of joint i;

[0053] The generalized coordinate transformation matrix is ​​applied using a differential kinematic model between joints. Taking the total differential, we get:

[0054]

[0055] Using Δq i =[Δθ i Δd i Δa i Δα i Δβ i ] T To express the joint parameter error, we get:

[0056] Δe i =K i Δq i (5)

[0057]

[0058] Where Δe i =[dx i dy i dz i δx i δy i δz i ] T K represents the error model of the end effector error caused by joint i relative to joint i-1. i This represents the error coefficient matrix for joint i. Δθ i Let Δd be the change in joint angle of joint i. i Δa represents the relative positional change of the connecting rods between adjacent joints. i Let Δα be the change in the common normal distance of the connecting rod. i For X i The axis is Z i-1 Axis rotates to Z i The change in the deflection angle of the axis, Δβ i To wrap around Y i The axis is Z i-1 Axis rotates to Z i The change in the axis's deflection angle.

[0059] A positive error analysis model for the robotic arm's end effector is formed by accumulating the errors of each joint:

[0060]

[0061] In the formula, Δe p =[dx dy dz δx δy δz] T , where dx, dy, dz represent the end-effector position accuracy of the space robot under a specific combination of kinematic parameters, and δx, δy, δz represent the end-effector attitude accuracy of the space robot under a specific combination of kinematic parameters;

[0062] The error is transformed into the robot's end-effector coordinate system, thus introducing a generalized coordinate transformation matrix for the end-effector of the robotic arm joint i relative to the base. The generalized coordinate transformation matrix representing the end effector of robotic arm joint i relative to the base is:

[0063]

[0064] The measured static pose accuracy Δe of the robotic arm's end effector can be obtained using testing methods. sp and dynamic trajectory tracking accuracy Δe dp The end effector accuracy Δe of the robotic arm is obtained through data fusion processing. p

[0065] Δe p =ρ1×Δe sp +ρ2×Δe dp (8)

[0066] In the formula, ρ1 and ρ2 represent the static pose accuracy Δe of the end effector of the space robot. sp and dynamic trajectory tracking accuracy Δe dp The weighting coefficients.

[0067] By setting the parameter errors of all modular joints to be consistent, the equivalent error of a single joint can be calculated in reverse based on the end-effector position and attitude accuracy according to the test results. Then, the end-effector pose accuracy of the space robot arm in the on-orbit three-dimensional mission configuration can be calculated and evaluated based on the equivalent single-joint error and the forward error analysis model.

[0068] To accurately assess the precision of a robotic arm's end-effector's three-dimensional motion during on-orbit three-dimensional mission configurations, and to overcome the limitations of traditional robotic arm precision measurements which rely solely on static positioning measurements and are restricted to planar motion by air-bearing platforms, this invention utilizes static and dynamic measurement results of two-dimensional planar motion. It employs a data weighting method for data fusion processing, uses comprehensive robotic arm error analysis to inversely deduce equivalent single-joint errors, and finally evaluates the end-effector pose precision of the space robotic arm's on-orbit three-dimensional mission configuration through forward error analysis. The effectiveness of this assessment method has been verified through on-orbit flight testing of a Chinese space robotic arm, effectively ensuring consistency between on-orbit and space-to-ground precision measurement.

[0069] The parts of this invention not described in detail are common knowledge to those skilled in the art.

Claims

1. A method for evaluating the accuracy of a space robotic arm, characterized in that: The accuracy evaluation of the space robotic arm is achieved using a space robotic arm accuracy evaluation device, which includes a simulation wall (11), a shoulder floating support (12), an elbow floating support (13), a wrist floating support (14), a theodolite (21), a static target (22), a dynamic target (32), and a laser tracker (31). The simulated wall (11) is fixed to the base and is used to fix the root of the robotic arm; The shoulder floating support (12) is used to support the shoulder of the robotic arm and provide a zero-gravity testing environment for the shoulder of the robotic arm. The elbow floating support (13) is used to support the elbow of the robotic arm and provide a zero-gravity testing environment for the elbow of the robotic arm. The wrist floating support (14) is used to support the wrist of the robotic arm and provide a zero-gravity testing environment for the wrist of the robotic arm. Static targets (22) are installed on the shoulder, elbow and wrist of the robotic arm; dynamic targets (32) are installed on the wrist of the robotic arm. The theodolite (21) is used to observe the static target (22) installed on the shoulder, elbow and wrist of the robotic arm, and to obtain the installation error of the shoulder, elbow and wrist components of the robotic arm as well as the position and attitude of the end of the entire arm; The laser tracker (31) measures the motion trajectory of the end effector of the robotic arm in real time through a dynamic target (32) mounted on the wrist of the robotic arm; The method for evaluating the accuracy of the space robotic arm includes: During the assembly of the robotic arm, a theodolite (21) is used to observe the static targets (22) installed on the shoulder, elbow and wrist of the robotic arm to obtain the installation error of the shoulder, elbow and wrist components of the robotic arm, and then obtain the length of the robotic arm and the joint deflection angle; if the length of the robotic arm and the joint deflection angle do not meet the index requirements, the assembly and adjustment are repeated until the index requirements are met. After the robotic arm has moved to its final position and come to rest, a theodolite (21) is used to observe the static target (22) mounted on the wrist of the robotic arm to obtain the position and attitude of the entire end of the arm. The position and attitude are then compared with the theoretically planned position and attitude to obtain the static pose accuracy Δe of the robotic arm. sp ; During the movement of the robotic arm, a laser tracker (31) is used to measure the motion trajectory of the robotic arm end effector in real time through a dynamic target (32) installed on the wrist of the robotic arm. The dynamic trajectory tracking accuracy Δe of the robotic arm is obtained by comparing it with the theoretical motion trajectory. dp ; Static pose accuracy Δe is calculated using a data weighting method. sp and dynamic trajectory tracking accuracy Δe dp Data fusion processing is performed to obtain the end effector accuracy Δe of the robotic arm. p ; Assuming that the parameter errors of all joints of the robotic arm are equal, based on the robotic arm's end effector accuracy Δe p Based on the error model of the robotic arm, the equivalent single-joint error is inferred; the end-effector pose accuracy of the space robotic arm in the on-orbit three-dimensional mission configuration is evaluated based on the equivalent single-joint error and the forward error analysis model.

2. The method for evaluating the accuracy of a space robotic arm according to claim 1, characterized in that: robotic arm end-efficiency Δe p satisfy Δe p =ρ1×Δe sp +ρ2×Δe dp In the formula, ρ1 and ρ2 represent the static pose accuracy Δe of the end effector of the space robot. sp and dynamic trajectory tracking accuracy Δe dp The weighting coefficients.

3. The method for evaluating the accuracy of a space robotic arm according to claim 1, characterized in that, A positive error analysis model for the end effector of the robotic arm is formed by accumulating the errors of each joint.

4. The method for evaluating the accuracy of a space robotic arm according to claim 3, characterized in that, The end-effector error caused by joint i relative to the error model Δe of joint i-1 i =[dx i dy i dz i δx i δy i δz i ] T , where dx i ,dy i ,dz i δx represents the positional error at the end of joint i. i ,δy i ,δz i This represents the attitude error at the end of joint i.

5. The method for evaluating the accuracy of a space robotic arm according to claim 4, characterized in that, The forward error analysis model for the space robotic arm is shown below: In the formula, Δe p =[dx dy dzδxδyδz] T , where dx, dy, dz represent the end-effector position accuracy of the space robot under a specific combination of kinematic parameters, and δx, δy, δz represent the end-effector attitude accuracy of the space robot under a specific combination of kinematic parameters; The generalized coordinate transformation matrix represents the end effector of the robotic arm joint i relative to the base; Δq i Indicates joint parameter error; K i Let represent the error coefficient matrix of joint i.

6. The method for evaluating the accuracy of a space robotic arm according to claim 5, characterized in that, The generalized coordinate transformation matrix between joint i and joint i-1 of the robotic arm is: Where, θ i Let X be the joint angle of joint i, i = 1, 2, ..., 7, and let X be the three coordinate axes of joint i. i Axis, Y i Axis, Z i Axis; α i For X i The axis is Z i-1 Axis rotates to Z i The deflection angle of the axis; β i To wrap around Y i The axis is Z i-1 Axis rotates to Z i The deflection angle of the axis; d i This refers to the relative position of the links between adjacent joints; a i is the common normal distance between adjacent joints; c is the abbreviation of the cosine function, and s is the abbreviation of the sinine function.

7. The method for evaluating the accuracy of a space robotic arm according to claim 6, characterized in that, Axis parallel joint d i =0, axis non-parallel joint β i It is 0.

8. The method for evaluating the accuracy of a space robotic arm according to claim 6, characterized in that, 9. The method for evaluating the accuracy of a space robotic arm according to claim 6, characterized in that, Δq i =[Δθ i Δd i Δa i Δα i Δβ i ] T , Δθ i Let Δd be the change in joint angle of joint i. i Δa represents the relative positional change of the connecting rods between adjacent joints. i Let Δα be the change in the common normal distance of the connecting rod. i For X i The axis is Z i-1 Axis rotates to Z i The change in the deflection angle of the axis, Δβ i To wrap around Y i The axis is Z i-1 Axis rotates to Z i The change in the axis's deflection angle.

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