A robot end effector integrating measurement and processing

Abstract

The present invention belongs to the field of robotic industrial processing technology, and discloses a robot end effector with integrated measurement and processing, which can complete milling and drilling processing of large-scale industrial structural parts and realize real-time detection of workpiece processing. The device is mainly composed of a Y-axis servo drive motor, a Y-axis limiter, a Y-axis guide rail, an electric spindle, an electric spindle fixture, a fixture mounting seat, a target ball, a point laser emitter, a line laser scanner, a Y-axis adapter plate, an X-axis servo drive motor, an X-axis limiter, an X-axis guide rail, an X-axis slide, a Y-axis slide, an X-axis grating ruler, a Y-axis grating ruler, and a laser tracker. The present invention has a simple structure, is easy to manufacture, has low cost, is easy to install, can realize real-time monitoring of processing, achieves the effect of reducing processing errors and improving overall processing accuracy, is a relatively cutting-edge technology in the field of large-scale structural parts processing, and has great application potential.

Description

Technical Field

[0001] The present invention belongs to the field of robotic industrial processing technology, and in particular relates to a robot end effector mechanism integrating measurement and processing, which can complete milling and drilling processing of large industrial structural parts and realize real-time detection of workpiece processing. Background Art

[0002] Large structural parts are widely found in the core components of high-end equipment, such as large wind turbine blades, high-speed rail bodies, and marine propellers. They are key parts and basic components of major equipment in the fields of new energy, marine, aerospace, rail transit, etc. Their manufacturing level is an important indicator of a country's industrial development level and comprehensive national strength. Although traditional CNC machine tools have high precision, they are expensive, lack flexibility, and have insufficient processing space, making them unable to meet the diverse needs of large structural part processing. Unlike machine tools, robots have advantages such as multiple degrees of freedom, high flexibility, large workspace, and low cost. However, the absolute positioning accuracy of robot processing is low, and the processing precision is insufficient. In particular, when robots are processing large structural parts, the position needs to be adjusted multiple times, resulting in lower precision. These are problems that urgently need to be solved in the field of robot processing.

[0003] Prior art document 1 “Review of robotic end-effector with force control. GL Zhang, J Zhang, YN Jiang et al. Chinese Journal of Engineering Design, 2019.” This document introduces the end effector of an industrial robot, which refers to a device installed at the end of the industrial robot arm that directly acts on the work object. It has the function of clamping, transporting and placing the workpiece to a certain position. As the final link and execution component of the interaction between the industrial robot and the external environment, it plays a very important role in improving the flexibility and ease of use of the industrial robot. It is generally designed according to the robot's operating requirements. The sum of its weight and operating force is the allowable load force of the robot, so it is required to be small in size, light in weight and compact in structure. Existing robot end effectors at home and abroad have poor versatility and are relatively limited in use.

[0004] A new type of robot end effector with integrated measurement and processing has been invented, which can complete milling, drilling and other processing tasks for large structural parts more accurately and flexibly. A line laser scanner scans the workpiece before processing begins to obtain the surface morphology of the workpiece; after processing, the workpiece is scanned again to determine whether the workpiece processing accuracy meets the error requirements. A target ball is installed on the electric spindle fixture. The target ball on the fixture is tracked and measured using a laser tracker to obtain the real-time coordinates of the electric spindle. At the same time, by using the conversion between coordinate systems, the coordinates of the workpiece in the global coordinate system can be obtained. In addition, three point laser emitters are installed on the end effector, which can determine the normal plane of the processed workpiece in real time to ensure the processing direction. Summary of the Invention

[0005] The technical challenge addressed by this invention is to overcome the technical deficiencies of existing robotic end effectors by inventing a robotic end effector that integrates measurement and machining, providing technical support for improving the machining accuracy of large structural parts. This integrated end effector is equipped with only a single line laser scanner, which scans the workpiece multiple times and achieves stitching, saving costs compared to using multiple line laser scanners. A laser tracker is used to track and measure the target ball on the electric spindle fixture, and three point laser emitters are added to the fixture to enable real-time monitoring of the machining process.

[0006] The technical solution adopted in the present invention is:

[0007] A robot end effector with integrated measurement and processing mainly consists of a Y-axis servo drive motor 1, a Y-axis limiter 2, a Y-axis guide 3, an electric spindle 4, an electric spindle fixture 5, a fixture mounting seat 6, a target ball 7, a point laser emitter 8, a line laser scanner 9, a Y-axis adapter plate 10, an X-axis servo drive motor 11, an X-axis limiter 12, an X-axis guide 13, an X-axis slide 14, a Y-axis slide 15, an X-axis grating ruler 16, a Y-axis grating ruler 17 and a laser tracker 18; wherein the end of the whole is adsorbed on the robot by a suction cup, the Y-axis servo drive motor 1 is installed on the top of the Y-axis slide 15, the Y-axis limiter 2 is installed below the Y-axis servo drive motor 1, the Y-axis guide 3 is installed on the surface of the Y-axis slide 15 along the Y-axis direction, and the electric spindle 4 is clamped by the electric spindle fixture 5 The electric spindle fixture 5 is fixed on the Y-axis guide rail 3, the electric spindle fixture 5 is fixed to the Y-axis guide rail 3 through the fixture mounting base 6, the target ball 7 is fixed to the electric spindle fixture 5 by the target ball base, the point laser emitter 8 is installed on the outside of the electric spindle fixture 5, the line laser scanner 9 is installed on the Y-axis slide 15 through the Y-axis adapter plate 10, the X-axis servo drive motor 11 is installed on the right end of the X-axis slide 14, the X-axis limiter 12 is installed on the left end of the X-axis slide 14, the X-axis guide rail 13 is installed on the surface of the X-axis slide 14 along the X-axis direction, the X-axis slide 14 and the Y-axis slide 15 constitute the main part of the end effector, the X-axis grating scale 16 and the Y-axis grating scale 17 are installed on the X-axis slide 14 and the Y-axis slide 15 respectively, and the laser tracker 18 is installed based on the target ball 7 on the electric spindle fixture.

[0008] The beneficial effects of the present invention are as follows: the invented robot end effector with integrated measurement and processing can complete high-precision milling and drilling processing of large structural parts, and obtain the surface accuracy after processing by scanning to verify whether the processing meets the error requirements. The target ball on the electric spindle fixture is tracked and measured by a laser tracker, and the real-time coordinates of the electric spindle can be obtained. At the same time, the principle of three-point determination of the normal plane is used to determine the normal plane of the workpiece in real time during the processing process through three-point laser to ensure the processing direction, thus solving the problem of low processing accuracy caused by the inability of the robot end effector to achieve real-time monitoring; by using a separate line laser scanner to scan the workpiece multiple times and then perform splicing processing, there is no need to use multiple line laser scanners, which reduces costs and provides technical support for the processing of large structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram of the overall structure of the robot end effector that integrates measurement and processing;

[0010] Figure 2 This is a schematic diagram of the various coordinate systems when the laser tracker tracks and measures the target sphere;

[0011] Figure 3This is a schematic diagram of the measurement part of the integrated end effector of the robot;

[0012] Figure 4 Schematic diagram of the processing part of the robot's end integrated actuator.

[0013] In the figure: 1-Y-axis servo drive motor, 2-Y-axis limiter, 3-Y-axis guide rail, 4-electric spindle, 5-electric spindle fixture, 6-fixture mounting base, 7-target ball, 8-point laser transmitter, 9-line laser scanner, 10-Y-axis adapter plate, 11-X-axis servo drive motor, 12-X-axis limiter, 13-X-axis guide rail, 14-X-axis slide, 15-Y-axis slide, 16-X-axis grating ruler, 17-Y-axis grating ruler, 18-laser tracker. DETAILED DESCRIPTION

[0014] The implementation of the present invention is described in detail with reference to the accompanying drawings and technical solutions. The present invention is designed to be a robot end effector that integrates measurement and processing. Figure 1 This is the overall structural diagram of the integrated actuator at the end of the robot. Figure 2 This is a schematic diagram of the various coordinate systems when the laser tracker tracks the target ball. Figure 3 This is a schematic diagram of the measurement part of the robot's end integrated actuator. Figure 4This is a schematic diagram of the processing section of the robot's end effector. The robot's end effector includes a Y-axis servo drive motor 1, a Y-axis limiter 2, a Y-axis guide rail 3, an electric spindle 4, an electric spindle fixture 5, a fixture mounting base 6, a target sphere 7, a point laser emitter 8, a line laser scanner 9, a Y-axis adapter plate 10, an X-axis servo drive motor 11, an X-axis limiter 12, an X-axis guide rail 13, an X-axis slide 14, a Y-axis slide 15, an X-axis linear scale 16, a Y-axis linear scale 17, and a laser tracker 18. The X-axis slide 14 and the Y-axis slide 15 form the main body of the end effector. The Y-axis servo drive motor 1 is mounted on top of the Y-axis slide 15 and provides power for the Y-axis slide 14. The Y-axis limiter 2 limits the overall movement range of the electric spindle 4 along the Y-axis, preventing it from exceeding the slide range. The Y-axis guide rail 3 is mounted on the Y-axis slide 15, and other components can be fixedly connected to the Y-axis guide rail 3 and thus move along the Y-axis slide 15. The electric spindle 4 is fixedly clamped on the Y-axis guide rail 3 by the electric spindle fixture 5. The electric spindle 4 moves through the Y-axis guide rail 3 during operation, and the end integrated actuator performs processing operations through the electric spindle 4. There are four target balls 7, which are mounted on the outside of the electric spindle fixture 5. The laser tracker 18 obtains the real-time coordinates of the electric spindle 4 by tracking and measuring the target balls 7. The point laser emitter 8 is mounted on the outside of the electric spindle fixture 5, and there are three point laser emitters 8 installed in total. The principle of determining the normal plane by three points is used to determine the normal plane of the workpiece in real time during the processing process through three point lasers to ensure the processing direction. The X-axis servo drive motor 11 is mounted on the right end of the X-axis slide 14 to provide power for the movement of the X-axis slide 14. The X-axis limiter 12 limits the overall movement range of the Y-axis slide 15 in the X-axis to prevent it from exceeding the slide range. The X-axis guide rail 13 is installed on the X-axis slide 14 , and other components can move along the X-axis slide 14 by being fixed to the X-axis guide rail 13 . Figure 2 This is a schematic diagram of each coordinate system when the laser tracker tracks and measures the target ball. During processing, the laser tracker 18 can obtain the real-time coordinates of the electric spindle by tracking the four target balls 7. Figure 3 This is a schematic diagram of the measurement part of the integrated actuator at the end of the robot. The X-axis slide 14 and the Y-axis slide 15 constitute the main body of the end. The line laser scanner 9 moves with the Y-axis slide 15 through the Y-axis adapter plate 10 to achieve up-dimensional scanning, and expands the scanning range by following the X-axis slide 14. The X-axis grating scale 16 is installed on the X-axis slide 14, and the Y-axis grating scale 17 is installed on the Y-axis slide 15. The grating scale ensures the accuracy of the slide movement. Before processing the workpiece, the line laser scanner 9 is first used to scan the entire workpiece through the X-axis slide 14 and the Y-axis slide 15 to determine the surface morphology of the workpiece. After the workpiece is processed, it is scanned as a whole again by the line laser scanner 9 to determine whether the processing accuracy meets the error requirements. Figure 4This is a schematic diagram of the processing part of the integrated end effector of the robot. During processing, the electric spindle 4 fixed on the Y-axis guide rail 3 by the electric spindle fixture 5 is fed along the processing direction to complete operations such as milling and drilling. At the same time, the three point laser emitters 8 on the electric spindle fixture 5 emit point lasers downward. The principle of determining the normal plane by three points is used to determine the normal plane of the workpiece to ensure the processing direction.

[0015] During the specific implementation process, the host computer issues instructions to the robot's end effector, which integrates measurement and processing. First, a line laser scanner 9 is used to scan the workpiece as a whole via the X-axis slide 14 and the Y-axis slide 15 to determine the surface morphology of the workpiece before processing. Then, the processing program is written and executed. The electric spindle 4 arrives at the processing station and begins processing. The laser tracker 18 tracks and measures the target ball 7 on the electric spindle fixture 5 to obtain the real-time coordinates of the electric spindle 4. The three-point laser emitter 8 emits point lasers to determine the normal plane of the workpiece. The program is adjusted based on the measurement results to reduce the feed error. At the same time, the laser tracker 18 maintains tracking and measurement of the target ball 7 on the electric spindle fixture 5, and the three-point laser emitters 8 emit point lasers to achieve real-time monitoring of the processing process and ensure overall processing accuracy. After processing is completed, the workpiece is scanned again using the line laser scanner 9 to check whether the processing accuracy meets the error requirements. The overall processing flow can achieve the goals of real-time monitoring and high-precision processing.

[0016] The end effector system of the integrated robot scanning and processing uses multiple coordinate system transformations to complete the relevant positioning and monitoring. The coordinate systems used are as follows: Figure 2 As shown, it includes the coordinate system A of the line laser scanner 9, the custom coordinate system B at the end of the Y-axis slide 15, the robot axis base coordinate system C, the coordinate system D of the suction cup at the connection between the robot and the end, and the coordinate system E of the laser tracker 18. During the processing, the relevant workpiece coordinates are first obtained by scanning with the line laser scanner 8. The coordinates under the coordinate system A of the line laser scanner 9 are first converted to the custom coordinate system B at the end of the Y-axis slide 15 through coordinate conversion. Let (X1, Y1, Z1) be the three-dimensional coordinates of a point in the coordinate system A of the line laser scanner 9, (X2, Y2, Z2) be the three-dimensional coordinates of a point in the custom coordinate system B at the end of the Y-axis slide 15, (t X ,t Y ,t Z ) are three translation parameters for a point from the coordinate system A of the line laser scanner 9 to the custom coordinate system B at the end of the Y-axis slide 15,

[0017] are the three rotation parameters for a point converted from the coordinate system A of the line laser scanner 9 to the custom coordinate system B at the end of the Y-axis slide 15, and K is the scale parameter for a point converted from the coordinate system A of the line laser scanner 9 to the custom coordinate system B at the end of the Y-axis slide 15. The model for converting from the coordinate system A of the line laser scanner 9 to the custom coordinate system B at the end of the Y-axis slide 15 is:

[0018]

[0019] Where:

[0020]

[0021]

[0022]

[0023] Its rotation matrix can be expressed as:

[0024]

[0025] Solving the transformation relationship between the two coordinate systems is to solve the rotation matrix R and the translation matrix T. In this paper, the quaternion method is used for solution:

[0026] Suppose that in coordinate system A there is a point set W={w1,w2,…,w i ,…,w n},w i =(X A ,Y A ,Z A ) T , in the coordinate system B, there is a corresponding common point set V={v1,v2,…,v i ,…,v n},v i =(X B ,Y B ,Z B ) T The centroids of the two point sets W and V are and The cross-co-occurrence matrix is

[0027] Let matrix M = HH T , use the values ​​in the matrix to form a new vector S=[M 23 M 31 M 12 ] T , let matrix N = H + H T -trace(H)·I, where I is the 3×3 unit matrix, and then we can get the symmetric matrix Solve the eigenvalue of the matrix Q, and then calculate the eigenvector E corresponding to its maximum eigenvalue = [e1e2e3e4] T ,(e1≥0), normalizing it to get the unit quaternion:

[0028]

[0029] Then the rotation matrix R(ω) can be expressed by a quaternion array as:

[0030]

[0031] After calculating the rotation matrix R(ω), all point pairs in the point set are substituted into Equation (1) to obtain multiple sets of translation matrices. The average value of all translation matrices is used as the final translation matrix T. The quaternion method can effectively utilize all point pairs in the common point set obtained by the scanner and has high solution accuracy.

[0032] After the workpiece coordinates are converted to the custom coordinate system B at the end of the Y-axis slide 15, the robot's base coordinate system C is a known fixed coordinate system. The workpiece coordinates in the custom coordinate system B can be converted to the robot's base coordinate system C using the above method. The relationships between the robot's own axes are all known, so the robot's base coordinate system C and the coordinate system D of the suction cup at the connection between the robot and the end can be converted to each other. The target ball 7 is installed on the outside of the electric spindle fixture 5 in a fixed position, and its corresponding coordinates can be measured. In this way, the coordinates of the target ball 7 can be placed in the coordinate system D, and the relative position of the workpiece coordinates and the target ball 7 coordinates in the coordinate system D can be obtained. The laser tracker 18 can obtain the coordinates of the target ball 7 in the laser tracker 18 coordinate system E by tracking and measuring the target ball 7. In addition, with the relative position of the workpiece coordinates and the target ball 7 coordinates obtained previously, the workpiece coordinates can be converted to the coordinate system of the laser tracker 18, thus obtaining the final workpiece coordinates. The laser tracker 18 transmits the obtained coordinate data to the host computer, thereby obtaining the coordinates of the workpiece in the global coordinate system.

[0033] During the specific implementation process, the laser tracker 18 can realize real-time monitoring of the machining process by tracking and measuring the target ball 7. When the machining starts, the host computer issues an instruction to first obtain the initial position coordinates of the electric spindle 4 and its relative position with the target ball 7 and place them in the coordinate system E of the laser tracker 18. After the linear laser scanner 9 completes the initial scan, the electric spindle 4 begins to move according to the program settings. When the electric spindle 4 reaches the program-set position, the relative position of the electric spindle 4 and the target ball 7 is obtained again and its coordinates are converted into the coordinate system E of the laser tracker 18. It can be obtained whether the feed distance meets the machining requirements. If it does not meet the requirements, the machining program is modified to reduce the feed error and ensure the overall machining accuracy, thus achieving the requirement of real-time monitoring during machining.

[0034] The robot end effector with integrated measurement and processing has a simple structure, is easy to manufacture, has low cost, is convenient to install, and can realize real-time monitoring of processing, thereby reducing processing errors and improving overall processing accuracy. It is a relatively cutting-edge technology in the field of large-scale structural parts processing and has great application potential.

Claims

1. A robot end effector integrating measurement and processing, characterized in that: The robot end effector mainly comprises a Y-axis servo drive motor (1), a Y-axis limiter (2), a Y-axis guide rail (3), an electric spindle (4), an electric spindle fixture (5), a fixture mounting seat (6), a target ball (7), a point laser emitter (8), a line laser scanner (9), a Y-axis adapter plate (10), an X-axis servo drive motor (11), an X-axis limiter (12), an X-axis guide rail (13), an X-axis slide (14), a Y-axis slide (15), an X-axis grating ruler (16), a Y-axis grating ruler (17) and a laser tracker (18); The X-axis slide (14) and the Y-axis slide (15) constitute the main body of the robot end effector, and the whole is adsorbed on the robot by a suction cup; wherein, the Y-axis servo drive motor (1) is installed on the top of the Y-axis slide (15), and the Y-axis limiter (2) is installed below the Y-axis servo drive motor (1), and the Y-axis limiter (2) is used to limit the moving range of the electric spindle (4) in the Y-axis direction; the Y-axis guide rail (3) is installed on the surface of the Y-axis slide (15) along the Y-axis direction, and the electric spindle (4) is fixed by the electric spindle fixture. (5) is clamped and fixed on the Y-axis guide rail (3), the electric spindle fixture (5) is fixedly connected to the Y-axis guide rail (3) through the fixture mounting seat (6), and the electric spindle (4) moves in the Y-axis direction through the Y-axis guide rail (3); the target ball (7) is fixed on the electric spindle fixture (5) by the target ball base, and the laser tracker (18) obtains the real-time coordinates of the electric spindle (4) by tracking and measuring the target ball (7); three point laser emitters (8) are installed on the outside of the electric spindle fixture (5), and the principle of determining the normal vector plane by three points is used to determine the real-time coordinates of the electric spindle (4) during the processing. The normal plane of the workpiece is determined in real time by three point lasers; the line laser scanner (9) is installed on the Y-axis slide (15) through the Y-axis adapter plate (10); the line laser scanner (9) moves with the Y-axis slide (15) through the Y-axis adapter plate (10) to achieve dimensional scanning, and expands the scanning range by following the X-axis slide (14); the X-axis servo drive motor (11) is installed at the right end of the X-axis slide (14), the X-axis limiter (12) is installed at the left end of the X-axis slide (14), and the X-axis limiter (12) is used to limit the moving range of the Y-axis slide (15) in the X-axis direction; the X-axis guide rail (13) is installed on the surface of the X-axis slide (14) along the X-axis direction, and other components move along the X-axis slide (14) by being fixed to the X-axis guide rail (13); the X-axis grating ruler (16) and the Y-axis grating ruler (17) are installed on the X-axis slide (14) and the Y-axis slide (15) respectively, ensuring the accuracy of the slide movement; the laser tracker (18) is installed based on the target ball (7) on the electric spindle fixture (5).

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