Kinematic parameter calibration method for multi-degree-of-freedom manipulator

Abstract

The present application provides a kinematic parameter calibration method for a multi-degree-of-freedom robot arm, comprising the steps of: fitting a first rotation axis axis and a second rotation axis axis; establishing a robot arm base coordinate system according to the first rotation axis axis and the second rotation axis axis; fitting a third rotation axis axis to obtain a 2-axis connecting rod length; fitting a fourth rotation axis axis to obtain a 3-axis connecting rod length and an offset of the fourth rotation axis axis relative to the second rotation axis axis; fitting a fifth rotation axis axis to obtain a 4-axis connecting rod length and an offset of the fifth rotation axis axis relative to the fourth rotation axis axis; fitting a sixth rotation axis axis to obtain a 5-axis connecting rod length and an offset of the sixth rotation axis axis relative to the fourth rotation axis axis.

Description

Technical Field

[0001] The present application belongs to the technical field of industrial robot calibration, and in particular, relates to a kinematic parameter calibration method for a multi-degree-of-freedom robotic arm. Background Art

[0002] At present, six-axis industrial robots generally have high repeatability but poor absolute positioning accuracy, which severely limits their application in areas with high precision requirements. There are many factors that affect accuracy, which can be divided into two categories according to the source of error. The first is geometric parameter error, which refers to the robot's geometric parameters, such as the actual value of the link length, offset, torsion angle and other parameters, which are inconsistent with the theoretical value. The second is non-geometric parameter error, which refers to the error caused by factors other than geometric parameter error, such as flexible deformation error caused by load and deadweight, error caused by temperature and humidity changes, error caused by friction, etc.

[0003] Research shows that robot positioning errors caused by geometric parameter deviations account for 85% of the total robot error. The currently commonly used method to reduce geometric parameter errors is kinematic parameter identification, which is to use kinematic modeling and error measurement to obtain the true value of the geometric parameters through the least squares method.

[0004] For example, a Chinese patent document with publication number CN111055273A discloses a two-step error compensation method for a robot, including: (1) establishing a robot positioning error model based on the modified DH method and differential kinematics; (2) solving all geometric parameter errors using the least squares iteration method, and directly compensating the geometric parameter errors that can be directly compensated into the DH configuration parameters of the robot; (3) converting the geometric parameter errors that cannot be directly compensated into joint angle compensation values, correcting the angle values ​​of each joint of the robot, and realizing indirect compensation.

[0005] A Chinese patent document with publication number CN114714348A discloses a method for improving the absolute positioning accuracy of an industrial robot, comprising: step S1, establishing a kinematic model of an industrial robot based on the MDH model method; step S2, analyzing the influence of various errors on the end position error in the joint space; step S3, establishing a robot error identification model for geometric errors; step S4, performing a large number of random sampling in the robot workspace, recording and calculating the theoretical value and measured value of each sampling point in the robot base coordinate system; step S5, partitioning the test data of step S4 into joint space; step S6, identifying error parameters in different joint space partitions using the damped iterative least squares method; step S7, fitting the residual error based on a neural network, and inputting it into the control system to improve the absolute positioning accuracy of the industrial robot.

[0006] However, when the gap between the actual value and the theoretical value is too large, the problem of falling into the local minimum may occur during the least squares solution iteration process. At the same time, kinematic parameter identification requires error modeling and iterative solution, which is a relatively complicated process. Summary of the invention

[0007] One of the purposes of the present application is to provide a kinematic parameter calibration method for a multi-degree-of-freedom robotic arm to improve the efficiency of parameter calibration.

[0008] To achieve the above-mentioned purpose and other related purposes, the present application provides a kinematic parameter calibration method for a multi-degree-of-freedom robot arm, comprising the steps of:

[0009] Fitting the first rotation axis to the second rotation axis;

[0010] Establishing a robot arm base coordinate system according to the first rotation axis and the second rotation axis;

[0011] Fit the axis of the third rotating axis to obtain the length of the 2-axis connecting rod;

[0012] Fit the axis of the fourth rotation axis to obtain the length of the 3-axis connecting rod and the offset of the axis of the fourth rotation axis relative to the axis of the second rotation axis;

[0013] Fitting the axis of the fifth rotation axis to obtain the length of the 4-axis connecting rod and the offset of the axis of the fifth rotation axis relative to the axis of the fourth rotation axis;

[0014] The axis of the sixth rotation axis is fitted to obtain the length of the 5-axis connecting rod and the offset of the axis of the sixth rotation axis relative to the axis of the fourth rotation axis.

[0015] Optionally, the specific steps of fitting the first rotation axis and the second rotation axis; and establishing the robot arm base coordinate system according to the first rotation axis and the second rotation axis include:

[0016] Rotate the first rotating seat, measure the coordinate value of the end of the robot arm at every predetermined angle, perform circle fitting on the coordinate value of the end of the robot arm, and obtain the coordinate value of the first rotating axis axis and the first circle center in the laser tracker coordinate system;

[0017] Determine the third direction of the robot base coordinate system with the first rotation axis; determine the position of the origin of the robot base coordinate system in the first direction and the second direction with the coordinate value of the first center of the circle;

[0018] Rotate the first rotating seat to a first predetermined position, measure the coordinate value of the end of the robot arm at every predetermined angle, perform circle fitting on the coordinate value of the end of the robot arm, and obtain the coordinate value of the second rotating axis axis and the second circle center in the laser tracker coordinate system;

[0019] Determine the second direction of the robot base coordinate system with the second rotation axis; determine the first direction of the robot base coordinate system according to the third direction and the second direction in combination with the right-hand rule; determine the position of the origin of the robot base coordinate system in the third direction with the coordinate value of the second center of the circle;

[0020] A robot arm base coordinate system is established according to the first direction, the second direction and the third direction and the position of the origin of the robot arm base coordinate system in the first direction, the second direction and the third direction.

[0021] Optionally, the step of fitting the axis of the third rotating shaft to obtain the length of the 2-axis connecting rod specifically includes:

[0022] Rotate the second rotating rod to the second predetermined position, fit the axis of the third rotating axis, obtain the coordinate values ​​of the axis of the third rotating axis and the third center of the circle in the laser tracker coordinate system, make the coordinate values ​​of the third center of the circle and the second center of the circle in the first direction in the robot arm base coordinate system equal, calculate the difference between the coordinate values ​​of the third center of the circle and the second center of the circle in the third direction in the robot arm base coordinate system, which is the 2-axis connecting rod length, wherein 2-axis refers to the second rotating axis.

[0023] Optionally, the second rotating rod is rotated to the second predetermined position by an angle, and the rotation angle can be determined by the following formula: Wherein, Δx is the difference in coordinate values ​​between the third circle center and the second circle center in the first direction of the robot arm base coordinate system, and Δz is the difference in coordinate values ​​between the third circle center and the second circle center in the third direction of the robot arm base coordinate system.

[0024] Optionally, fitting the fourth rotation axis to obtain the length of the three-axis connecting rod and the offset of the fourth rotation axis relative to the second rotation axis specifically comprises the following steps:

[0025] Rotate the third rotating rod to the third predetermined position, fit the fourth rotating axis axis, obtain the coordinate values ​​of the fourth rotating axis axis and the fourth center of the circle in the laser tracker coordinate system, so that the fourth rotating axis axis is parallel to the first direction of the robot arm base coordinate system, and calculate the distance between the fourth center of the circle and the third center of the circle in the third direction of the robot arm base coordinate system, which is the 3-axis connecting rod length, wherein the 3-axis refers to the third rotating axis; calculate the coordinate value of the fourth center of the circle in the second direction of the robot arm base coordinate system, which is the offset of the fourth rotating axis axis relative to the second rotating axis axis.

[0026] Optionally, fitting the axis of the fifth rotation axis to obtain the 4-axis connecting rod length and the offset of the axis of the fifth rotation axis relative to the axis of the fourth rotation axis specifically includes the following steps: rotating the fourth rotating rod to a fourth predetermined position, fitting the axis of the fifth rotation axis, obtaining the coordinate values ​​of the axis of the fifth rotation axis and the fifth center of the circle in the laser tracker coordinate system, so that the axis of the fifth rotation axis is parallel to the second direction in the robot arm base coordinate system, and calculating the distance between the fifth center of the circle and the third center of the circle in the first direction in the robot arm base coordinate system, which is the 4-axis connecting rod length, wherein the 4-axis refers to the fourth rotation axis; calculating the difference in coordinate values ​​between the fifth center of the circle and the fourth center of the circle in the third direction in the robot arm base coordinate system, which is the offset of the axis of the fifth rotation axis relative to the axis of the fourth rotation axis.

[0027] Optionally, fitting the axis of the sixth rotation axis to obtain the 5-axis connecting rod length and the offset of the axis of the sixth rotation axis relative to the axis of the fourth rotation axis specifically includes the following steps: rotating the fifth rotating rod to the fifth predetermined position, fitting the axis of the sixth rotation axis, obtaining the coordinate values ​​of the axis of the sixth rotation axis and the sixth center of the circle in the laser tracker coordinate system, so that the axis of the sixth rotation axis is parallel to the first direction in the robot arm base coordinate system, and calculating the coordinate value difference between the sixth center of the circle and the fifth center of the circle in the first direction in the robot arm base coordinate system, which is the 5-axis connecting rod length, wherein the 5-axis refers to the fifth rotation axis; calculating the coordinate value difference between the sixth center of the circle and the fourth center of the circle in the second direction in the robot arm base coordinate system, which is the offset of the axis of the sixth rotation axis relative to the fourth rotation axis.

[0028] This application has at least the following beneficial effects:

[0029] 1. The kinematic parameter calibration method of the multi-degree-of-freedom robot arm of the present invention can determine the kinematic parameters of the robot by laser tracker measurement and simple calculation, without the need for complex modeling and parameter identification iterative solution, thereby improving the efficiency of parameter calibration;

[0030] 2. The kinematic parameter calibration method of the multi-DOF manipulator of the present invention can be used as a pre-process for parameter identification in situations where higher accuracy is required, so as to solve the problem of iterative calculation falling into a local minimum. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A schematic diagram of the structure of a multi-degree-of-freedom robotic arm according to an embodiment of the present invention;

[0033] Figure 2 The present invention is a flowchart of a method for calibrating kinematic parameters of a multi-degree-of-freedom robotic arm according to an embodiment of the present invention.

[0034] Illustration Description:

[0035] O B Robot arm base coordinate system O B -X B Y B Z B The origin of the axis; A1 is the first rotation axis; A2 is the second rotation axis; A3 is the third rotation axis; A4 is the fourth rotation axis; A5 is the fifth rotation axis; A6 is the sixth rotation axis; L1 is the 1st axis connecting rod length; L2 is the 2nd axis connecting rod length; L3 is the 3rd axis connecting rod length; L4 is the 4th axis connecting rod length; L5 is the 5th axis connecting rod length. DETAILED DESCRIPTION

[0036] The following describes the implementation methods of the present application through specific specific embodiments, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific implementation methods, and the details in the present application can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0037] In the description of the present application, it should be noted that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0038] Reference Figure 1 The multi-degree-of-freedom robot arm includes a base, a first rotating member, a second rotating member, a third rotating member, a fourth rotating member, a fifth rotating member, and a sixth rotating member connected in sequence. The end of the sixth rotating rod away from the fifth rotating member is the end of the robot arm.

[0039] Wherein, the first rotating member includes a first rotating seat and a first rotating shaft, the first rotating shaft is fixed on the base, and the first rotating seat is sleeved on the first rotating shaft and rotates relative to the base unit. The second rotating member includes a second rotating shaft and a second rotating rod; the second rotating shaft is fixed on the first rotating member, and the second rotating rod is hinged to the first rotating member through the second rotating shaft. The third rotating member includes a third rotating shaft and a third rotating rod; the third rotating shaft is fixed to an end of the second rotating member away from the second rotating shaft, and the third rotating rod is hinged to the second rotating member through the third rotating shaft. The fourth rotating member includes a fourth rotating shaft and a fourth rotating rod; the fourth rotating shaft is fixed to an end of the third rotating member away from the third rotating shaft, and the fourth rotating rod is hinged to the third rotating member through the fourth rotating shaft. The fifth rotating member includes a fifth rotating shaft and a fifth rotating rod; the fifth rotating shaft is fixed to an end of the fourth rotating member away from the fourth rotating shaft, and the fifth rotating rod is hinged to the fourth rotating member through the fifth rotating shaft. The sixth rotating member includes a sixth rotating shaft and a sixth rotating rod; the sixth rotating shaft is fixed to an end of the fifth rotating member away from the fifth rotating shaft, and the sixth rotating rod is hinged to the fifth rotating member through the sixth rotating shaft.

[0040] This embodiment is used according to Figure 1 and Figure 2 The kinematic parameter calibration method of the multi-degree-of-freedom robotic arm of the present invention is described in detail.

[0041] This embodiment provides a method for calibrating kinematic parameters of a multi-degree-of-freedom robotic arm, comprising the following steps:

[0042] Establish the robot base coordinate system O B -X B Y B Z B ; Among them, the first direction is X B direction, the second direction is Y B Direction, the third direction is Z B direction;

[0043] Establish the robot base coordinate system O B -X B Y B Z B The specific steps include:

[0044] Fitting the first rotation axis A1. The specific steps of fitting the first rotation axis A1 include rotating the first rotating seat, measuring the coordinate values ​​of the end of the robot arm at every predetermined angle, performing circle fitting on the coordinate values ​​of the end of the robot arm, and obtaining the coordinate values ​​(0,0,z1) of the first rotation axis A1 and the first circle center O1 (not shown in the figure) in the laser tracker coordinate system.

[0045] The robot base coordinate system O is determined by the first rotation axis A1 B -X B YB Z B Z B Direction; Determine the robot base coordinate system O with the coordinate value (0,0,z1) of the first circle center O1 B -X B Y B Z B Origin O B In X B Direction and Y B Position in direction (not shown in the figure);

[0046] The first rotating seat is rotated to the first predetermined position to fit the second rotating axis A2. The specific steps of fitting the second rotating axis A2 include rotating the second rotating rod, measuring the coordinate value of the end of the robot arm at every predetermined angle, performing circle fitting on the coordinate value of the end of the robot arm, and obtaining the coordinate value (x2, y2, 0) of the second rotating axis A2 and the second circle center O2 (not shown in the figure) in the laser tracker coordinate system.

[0047] The robot base coordinate system O is determined by the second rotation axis A2 B -X B Y B Z B Y B Direction; According to Z B Direction, Y B Direction, combined with the right-hand rule to determine O B -X B Y B Z B X B Direction; Determine the robot base coordinate system O with the coordinate value (x2, y2, 0) of the second center O2 in the laser tracker coordinate system B -X B Y B Z B Origin O B In Z B Position in direction;

[0048] According to X B Direction, Y B Direction, Z B Direction and origin O B In X B Direction, Y B Direction and Z B The position in the direction establishes the robot arm base coordinate system O B -X B Y B Z B , that is, the coordinates of the points measured by the laser tracker coordinate system can be expressed by the robot base coordinate system O B -X BY B Z B The coordinates are used to describe the laser tracker coordinate system and transfer it to the robot arm base coordinate system.

[0049] According to the second circle center O2 in the robot base coordinate system O B -X B Y B Z B X B The coordinate x2 in the direction obtains the spatial distance x2 between the first rotation axis axis A1 and the second rotation axis axis A2, where x2 is the 1-axis connecting rod length L1, wherein 1-axis refers to the first rotation axis.

[0050] It should be noted that when rotating the first rotating seat, the end of the robot arm is required not to be in the robot arm base coordinate system O B -X B Y B Z B Z B When rotating the second rotating rod, the end of the robot arm is not in the robot arm base coordinate system O B -X B Y B Z B Y B In direction.

[0051] Fitting the third rotation axis A3, the specific steps include: rotating the third rotating rod, measuring the coordinate value of the end of the robot arm at every predetermined angle, performing circle fitting on the coordinate value of the end of the robot arm, and obtaining the coordinate value (x3, y3, z3) of the third rotation axis A3 and the third circle center O3 (not shown in the figure).

[0052] Determine whether x3 is equal to x2. If not, rotate the second rotating rod to the second predetermined position, and then fit the third rotating axis A3 so that x3 is equal to x2. The third rotating axis A3 and the second rotating axis A2 are obtained at Z. B The distance z3 in the direction, z3 is the 2-axis link length L2, where 2-axis refers to the second rotation axis.

[0053] The second rotating rod rotates to the second predetermined position by an angle θ, and the magnitude of the rotation angle θ can be determined by the following formula: Among them, Δx is the difference between x3 and x2, and Δz is the value of z3.

[0054] Fitting the fourth rotation axis A4, the specific steps include: rotating the fourth rotation rod, measuring the coordinate values ​​of the end of the robot arm at every predetermined angle, performing circle fitting on the coordinate values ​​of the end of the robot arm, and obtaining the coordinate values ​​(x4, y4, z4) of the fourth rotation axis A4 and the fourth circle center O4 (not shown in the figure).

[0055] Determine the fourth rotation axis A4 and the robot base coordinate system O B -X B Y B Z B X B If not, rotate the third rotating rod to the third predetermined position, and then fit the fourth rotating axis A4 so that the fourth rotating axis A4 is parallel to the robot arm base coordinate system O B -X B Y B Z B X B The fourth rotation axis A4 and the third rotation axis A3 are parallel in Z direction. B The distance in the direction is the difference between z4 and z3, and the difference between z4 and z3 is the length of the 3-axis connecting rod L3, where 3-axis refers to the third rotation axis. Calculate the fourth rotation axis axis A4 at the second rotation axis axis A2 in Y B The spacing in the direction is the difference between y4 and y2, that is, the offset of the fourth rotation axis A4 relative to the second rotation axis A2.

[0056] Fitting the fifth rotation axis A5, the specific steps include: rotating the fifth rotation rod, measuring the coordinate value of the end of the robot arm at every predetermined angle, performing circle fitting on the coordinate value of the end of the robot arm, and obtaining the coordinate value (x5, y5, z5) of the fifth rotation axis A5 and the fifth circle center O5 (not shown in the figure).

[0057] Determine the fifth rotation axis A5 and the robot base coordinate system O B -X B Y B Z B Y B If not, rotate the fourth rotating rod to the fourth predetermined position, and then fit the fifth rotating axis axis A5 so that the fifth rotating axis axis A5 is parallel to the robot arm base coordinate system O B -X B Y B Z B Y B The fifth rotation axis A5 and the third rotation axis A3 are parallel in the X direction. B The distance in the direction is the difference between x5 and x3, and the difference between x5 and x3 is the length of the 4-axis connecting rod L4, where 4-axis refers to the fourth rotation axis. Calculate the distance between the fifth rotation axis A5 and the fourth rotation axis A4 in Z B The spacing in the direction is the difference between z5 and z4, that is, the offset of the fifth rotation axis A5 relative to the fourth rotation axis A4.

[0058] Fitting the sixth rotation axis A6; the specific steps include: rotating the sixth rotation rod, measuring the coordinate values ​​of the end of the robot arm at every predetermined angle, performing circle fitting on the coordinate values ​​of the end of the robot arm, and obtaining the coordinate values ​​(x6, y6, z6) of the sixth rotation axis A6 and the sixth circle center O6 (not shown in the figure).

[0059] Determine the sixth rotation axis A6 and the robot base coordinate system O B -X B Y B Z B X B If not, rotate the fifth rotating rod to the fifth predetermined position, and then fit the sixth rotating axis A6 so that the sixth rotating axis A6 is parallel to the robot arm base coordinate system O B -X B Y B Z B X B The sixth rotation axis A6 and the fifth rotation axis A5 are parallel in the X direction. B The distance in the direction is the difference between x6 and x5, and the difference between x6 and x5 is the length of the 5-axis connecting rod L5, where the 5-axis refers to the fifth rotation axis; calculate the distance between the sixth rotation axis A6 and the fourth rotation axis A4 in the Y direction. B The spacing in the direction is the difference between y6 and y4, which is the offset of the sixth rotation axis A6 relative to the fourth rotation axis A4.

[0060] The kinematic parameter calibration method of the present application is not only applicable to the six-axis industrial robot described in this embodiment, but can also be used for the kinematic parameter calibration method of industrial robots with three axes, four axes, five axes and more than six axes.

[0061] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present application. These improvements and substitutions should also be regarded as the scope of protection of the present application.

Claims

1. A method for calibrating kinematic parameters of a multi-degree-of-freedom robotic arm, characterized in that: Includes steps: Fitting the first rotation axis to the second rotation axis; Establishing a robot arm base coordinate system according to the first rotation axis and the second rotation axis; Fit the axis of the third rotating axis to obtain the length of the 2-axis connecting rod; Fit the axis of the fourth rotation axis to obtain the length of the 3-axis connecting rod and the offset of the axis of the fourth rotation axis relative to the axis of the second rotation axis; Fitting the axis of the fifth rotation axis to obtain the length of the 4-axis connecting rod and the offset of the axis of the fifth rotation axis relative to the axis of the fourth rotation axis; Fit the axis of the sixth rotation axis to obtain the length of the 5-axis connecting rod and the offset of the axis of the sixth rotation axis relative to the axis of the fourth rotation axis; Wherein, the first rotation axis and the second rotation axis are fitted; according to the first rotation axis and the second The specific steps of establishing the robot base coordinate system of the rotating axis include: Rotate the first rotating seat, measure the coordinate value of the end of the robot arm at every predetermined angle, perform circle fitting on the coordinate value of the end of the robot arm, and obtain the coordinate value of the first rotating axis axis and the first circle center in the laser tracker coordinate system; Determine the third direction of the robot base coordinate system with the first rotation axis; determine the position of the origin of the robot base coordinate system in the first direction and the second direction with the coordinate value of the first center of the circle; Rotate the first rotating seat to a first predetermined position, measure the coordinate value of the end of the robot arm at every predetermined angle, perform circle fitting on the coordinate value of the end of the robot arm, and obtain the coordinate value of the second rotating axis axis and the second circle center in the laser tracker coordinate system; Determine the second direction of the robot base coordinate system with the second rotation axis; determine the first direction of the robot base coordinate system according to the third direction and the second direction in combination with the right-hand rule; determine the position of the origin of the robot base coordinate system in the third direction with the coordinate value of the second center of the circle; Establishing a robot base coordinate system according to the first direction, the second direction and the third direction and the position of the origin of the robot base coordinate system in the first direction, the second direction and the third direction; The steps of fitting the axis of the third rotating axis to obtain the length of the 2-axis connecting rod specifically include: Rotate the second rotating rod to the second predetermined position, fit the axis of the third rotating axis, obtain the coordinate values ​​of the axis of the third rotating axis and the third center of the circle in the laser tracker coordinate system, so that the coordinate values ​​of the third center of the circle and the second center of the circle in the first direction in the robot base coordinate system are equal, and calculate the difference between the coordinate values ​​of the third center of the circle and the second center of the circle in the third direction in the robot base coordinate system, which is the 2-axis connecting rod length, wherein the 2-axis refers to the second rotating axis; The second rotating rod is rotated to the second predetermined position by an angle, and the rotation angle can be determined by the following formula: Wherein, Δx is the difference in coordinate values ​​between the third circle center and the second circle center in the first direction of the robot arm base coordinate system, and Δz is the difference in coordinate values ​​between the third circle center and the second circle center in the third direction of the robot arm base coordinate system.

2. The kinematic parameter calibration method according to claim 1, characterized in that: Fitting the fourth rotation axis to obtain the length of the three-axis connecting rod and the offset of the fourth rotation axis relative to the second rotation axis specifically includes the following steps: Rotate the third rotating rod to the third predetermined position, fit the fourth rotating axis axis, obtain the coordinate values ​​of the fourth rotating axis axis and the fourth center of the circle in the laser tracker coordinate system, so that the fourth rotating axis axis is parallel to the first direction of the robot arm base coordinate system, and calculate the distance between the fourth center of the circle and the third center of the circle in the third direction of the robot arm base coordinate system, which is the 3-axis connecting rod length, wherein the 3-axis refers to the third rotating axis; calculate the coordinate value of the fourth center of the circle in the second direction of the robot arm base coordinate system, which is the offset of the fourth rotating axis axis relative to the second rotating axis axis.

3. The kinematic parameter calibration method according to claim 1, characterized in that: Fitting the axis of the fifth rotation axis to obtain the length of the 4-axis connecting rod and the offset of the axis of the fifth rotation axis relative to the axis of the fourth rotation axis specifically includes the following steps: rotating the fourth rotation rod to a fourth predetermined position, fitting the axis of the fifth rotation axis, obtaining the coordinate values ​​of the axis of the fifth rotation axis and the fifth center of a circle in the laser tracker coordinate system, so that the axis of the fifth rotation axis is parallel to the second direction in the robot base coordinate system, and calculating the distance between the fifth center of a circle and the third center of a circle in the first direction in the robot base coordinate system, which is the length of the 4-axis connecting rod, wherein the 4-axis refers to the fourth rotation axis; calculating the difference in coordinate values ​​between the fifth center of a circle and the fourth center of a circle in the third direction in the robot base coordinate system, which is the offset of the axis of the fifth rotation axis relative to the axis of the fourth rotation axis.

4. The kinematic parameter calibration method according to claim 2, characterized in that: Fitting the sixth rotation axis to obtain the length of the 5-axis connecting rod and the offset of the sixth rotation axis relative to the fourth rotation axis specifically includes the following steps: Rotate the fifth rotating rod to the fifth predetermined position, fit the sixth rotating axis axis, obtain the coordinate values ​​of the sixth rotating axis axis and the sixth circle center in the laser tracker coordinate system, so that the sixth rotating axis axis is parallel to the first direction in the robot arm base coordinate system, calculate the coordinate value difference between the sixth circle center and the fifth circle center in the first direction in the robot arm base coordinate system, which is the 5-axis connecting rod length, wherein the 5-axis refers to the fifth rotating axis; calculate the coordinate value difference between the sixth circle center and the fourth circle center in the second direction in the robot arm base coordinate system, which is the offset of the sixth rotating axis axis relative to the fourth rotating axis axis.

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