A robot tool coordinate system calibration method based on a laser tracker

Abstract

A kind of robot tool coordinate system calibration method based on laser tracker, first, the axis of robot end flange is collected to feature point;Second, the feature point needed for establishing tool coordinate system is collected;Third, the feature point of another axis of flange is collected;Finally, the robot end tool coordinate system is established by fitting line surface feature.This method can realize the quick and accurate calibration of robot end tool, improve the calibration efficiency of tool coordinate system, and the feature point data collection is one-way in the calibration process, which avoids the error introduced by robot repeated positioning.The method is simple to operate, and the calibration effect is good.

Description

Technical Field

[0001] This invention belongs to the field of robot machining coordinate system calibration technology, and specifically relates to a method for calibrating the tool coordinate system of a robot end effector. Background Technology

[0002] Industrial robots are increasingly being used in automobile manufacturing, machining, welding, grinding and polishing, assembly, painting and other fields due to their advantages such as low cost, flexible operation and strong scalability.

[0003] Robotic machining often utilizes end effectors to achieve various processing requirements. To ensure high precision and efficiency in robotic machining, rapid and accurate calibration of the workpiece and tool coordinate systems is crucial. Currently, robot tool coordinate system calibration methods require repeated positioning of key data points, which is not only complex but also fails to effectively avoid the accumulation of positioning errors caused by repeated positioning, resulting in low calibration accuracy. To address this issue, this invention proposes a rapid robot tool coordinate system calibration method based on a laser tracker and data processing software that avoids repeated positioning. Summary of the Invention

[0004] To address the problem of rapid positioning of end-effectors in industrial robots, this invention provides an efficient calibration method for robot end-effectors based on a laser tracker, enabling rapid and accurate calibration of the robot end-effector coordinate system.

[0005] A method for calibrating the coordinate system of a robot tool based on a laser tracker, characterized by the following specific steps:

[0006] S1. Start the robot processing and calibration system;

[0007] S2. Fix the laser target ball onto the end tool of the robot processing system;

[0008] S3. Establish the robot's base coordinate system, represented by {B};

[0009] S4. Obtain the first axis vector required to establish the flange coordinate system. Fix the laser target ball on the target ball seat, rotate the robot end flange around the Z-axis, and collect feature point data Pi. Fit the end flange axis with the outward pointing direction as positive to obtain the robot flange coordinate Z-axis vector, denoted as F. z F z =[a z ,b z ,c z ] T ;

[0010] S5. Keeping the robot's pose unchanged, obtain the origin and two-axis vector feature points needed to establish the tool coordinate system. Collect feature point data on the tool using a target ball to obtain the origin O of the tool coordinate system. t With the tool holder vector T z T z =[i z ,j z ,k z ] T And using the flange coordinate system Z-axis F z Components as tool coordinate system T x or T y axis, where T x =[i x ,j x ,k x ] T ,T y =[i y ,j y ,k y ] T This allows the tool coordinate system {T} to be established;

[0011] S6. Obtain the second axis vector of the flange coordinate system. Place the laser target ball on the target ball seat fixed to the tool as described in S4, rotate it around the X or Y axis of the robot's end flange, and obtain the flange X-axis vector F by fitting the collected point data. x Or the Y-axis vector F y F x =[a x ,b x ,c x ] T or F y =[a y ,b y ,c y ] T ;

[0012] S7. Obtain the origin O of the flange coordinate system. f The origin O of the flange coordinate system is the intersection of the fitted flange's Z-axis and X-axis (or Y-axis). f This allows us to obtain the flange coordinate system {F}.

[0013] S8. Obtain the transformation matrix R between coordinate systems through software, input it into the robot control system, and complete the calibration.

[0014] A method for calibrating the coordinate system of a robot tool based on a laser tracker is characterized in that the establishment of the robot tool coordinate system is achieved by measuring and fitting the geometric features of the tool using a laser tracker.

[0015] Furthermore, the tool coordinate system is calibrated on the robotic machining system that has been equipped with an end effector.

[0016] Furthermore, the calibration sequence of the tool device coordinate system should follow steps S1 to S8 described above. (This step has a problem.)

[0017] Furthermore, to ensure fitting accuracy while meeting the feature fitting requirements, the number of feature points i ≥ 2n, where n is the theoretical number of points required for fitting. (Example: For spherical fitting, at least 8 data points should be collected).

[0018] Furthermore, in S5 above, for cylindrical tools, the cylindrical axis T of the tool holder can be determined using SA software. z By fitting the tool end face plane P, the intersection point O between the axis and the end face can be obtained. t The intersection of the cylindrical axis and the end face is used as the Z-axis of the tool and the origin of the tool coordinate system, respectively. For spherical tools, the feature points of the spherical head can be acquired and fitted using SA software, with the tool shank axis T... z and the fitted sphere center O t These are respectively used as the Z-axis and origin of the tool coordinate system. The flange coordinate system Z-axis F... z The component is used as the X(Y) axis T of the tool coordinate system. x (T y By using the vector, the tool coordinate system {T} can be obtained;

[0019] Furthermore, based on the features obtained from S4 to S7, we can simultaneously obtain:

[0020]

[0021]

[0022] Furthermore, the data acquisition sequence of the feature points is as follows: flange shaft feature points - tool feature points - flange shaft feature points. The flange shaft only needs to ensure that the measured axes are different, that is, the following sorting methods are available: flange Z-axis (feature point) - tool (feature point) - flange Y-axis (feature point), flange Z-axis - tool - flange X-axis, flange Y-axis - tool - flange Z-axis, flange Y-axis - tool - flange X-axis, flange X-axis - tool - flange Z-axis, flange X-axis - tool - flange Y-axis.

[0023] Furthermore, after establishing the tool coordinate system, based on the transformation relation {T} = R × {F}, the homogeneous transformation matrix R of the tool coordinate system relative to the robot flange is obtained through software.

[0024] Where R is:

[0025] Afterwards, the tool head can be replaced as needed for processing without recalibration.

[0026] This invention, based on a laser tracker, proposes a method for calibrating the coordinate relationship between a robot's end effector and the robot. This method enables rapid and accurate calibration of the robot's end effector, improving the efficiency of tool coordinate system calibration. In this invention, feature point data acquisition is performed unidirectionally during the calibration process, avoiding measurement errors introduced by repeated robot positioning. This invention is simple to operate and yields good calibration results. Attached Figure Description

[0027] Figure 1 Flowchart of Robot Tool Coordinate System Calibration Based on Laser Tracker

[0028] Figure 2 Schematic diagram of a robot coordinate system calibration system based on a laser tracker

[0029] Figure 3 Partial feature fitting diagram Detailed Implementation

[0030] The invention will now be further described with reference to the accompanying drawings.

[0031] The equipment used in this embodiment includes a KUKA robot (1), a target ball (2) fixed to the robot's end effector, and a laser tracker (3), etc.

[0032] A method for calibrating the coordinate system of a robot tool based on a laser tracker, the specific steps of which are as follows:

[0033] Step S1: Start the robot and laser tracker, and open the SA application software;

[0034] Step S2: Install the tool at the end of the robot and fix the laser target ball holder on the tool;

[0035] Step S3: Establish the robot's base coordinate system using a laser tracker, denoted by {B};

[0036] Step S4: Fix the laser target ball onto the target ball holder. In tool mode, rotate the robot's end effector axis and acquire feature point P using SA software. i For data where i ≥ 2n, and n is the number of theoretical points required for fitting, the Z-axis vector of the robot flange coordinates can be obtained by fitting the end axis with the outward pointing direction as the positive direction. This vector is denoted as F. z F z =[a z ,b z ,c z ] T ;

[0037] Step S5: Keeping the robot pose unchanged, collect tool point data through the target ball, and use SA software to measure the tool holder cylindrical axis T. z By fitting the tool end face plane P, the axis T can be further obtained. z Intersection point O with end face P t Using the intersection of the cylindrical axis and the end face as the Z-axis of the tool and the origin of the tool coordinate system, and the Z-axis component of the flange coordinate system as the X-axis of the tool coordinate system, the tool coordinate system {T} can be obtained.

[0038] Step S6: Place the laser target ball on the target ball seat fixed to the tool as described in S4, rotate it around the X or Y axis of the robot end flange, and obtain the X or Y axis of the flange by fitting the collected point data.

[0039] Step S7: Take the intersection of the Z-axis and the X-axis (Y-axis) as the origin O of the flange coordinate system. f This allows us to obtain the flange coordinate system {F}.

[0040] Step S8: The transformation matrix R between the tool coordinate system and the flange coordinate system in {T}=R×{F} can be determined using SA software.

[0041] By inputting this transformation relationship into the robot control system, the coordinate system calibration can be completed.

[0042] In summary, this invention calibrates the tool coordinate system in a robot machining system based on a laser tracker. The laser tracker, with its high-precision measurement capabilities, combined with the method proposed in this invention, can efficiently and accurately calibrate the tool coordinate system.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calibrating the coordinate system of a robot tool based on a laser tracker, characterized in that, The specific steps are as follows: S1. Start the robot processing and calibration system; S2. Fix the laser target ball onto the end tool of the robot processing system; S3. Establish the robot's base coordinate system, represented by {B}; S4. Obtain the first axis vector required to establish the flange coordinate system; fix the laser target ball on the target ball seat, rotate the robot end flange around the Z-axis of the robot end flange, and collect feature point data. By fitting the end axis with the outward pointing direction as the positive direction, the Z-axis vector of the robot flange coordinates can be obtained, denoted as . ,in = ; S5. Keeping the robot's pose unchanged, obtain the origin and two-axis vector feature points needed to establish the tool coordinate system; collect feature point data on the tool using the target ball to obtain the origin of the tool coordinate system. With the tool holder vector ,in = ; and using the flange coordinate system Z-axis Components as tool coordinate system or Axis, where = , = The tool coordinate system {T} can then be established; the specific process is as follows: →{T}， For cylindrical tools, the tool shank axis can be set using SA software. By fitting the tool end face plane P, the axis can be further obtained. Intersection with end face P With the axis of the tool holder Intersection with end face The Z-axis and origin serve as the coordinate system for the tool; for spherical tools, the feature points of the spherical head can be acquired and fitted using SA software, with the tool shank axis as the reference point. and fitted sphere center As the Z-axis and origin of the tool coordinate system; S6. Obtain the second axis vector of the flange coordinate system; fix the laser target ball on the target ball seat described in step S4, rotate it around the X or Y axis of the robot's end flange, and obtain the flange X-axis vector by fitting the collected point data. or Y-axis vector ,in = or = ; S7. Obtain the origin of the flange coordinate system. The origin of the flange coordinate system is the intersection of the flange's Z-axis and X-axis, or the flange's Z-axis and Y-axis. The flange coordinate system {F} can then be obtained. The specific process is as follows: →{F}； S8. Obtain the transformation matrix between coordinate systems using software. R Input the data into the robot control system to complete the calibration.

2. The method for calibrating the coordinate system of a robot tool based on a laser tracker according to claim 1, characterized in that, The coordinate system is established by measuring and fitting the geometric features of the tool using a laser tracker.

3. The method for calibrating the coordinate system of a robot tool based on a laser tracker according to claim 1, characterized in that, The tool coordinate system is calibrated on a robotic machining system that has been equipped with an end effector.

4. The method for calibrating the coordinate system of a robot tool based on a laser tracker according to claim 1, characterized in that, To ensure fitting accuracy while meeting feature fitting requirements, the number of feature points... i ≥ 2 n , n The required number of theoretical points for fitting.

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