CN109489555B - Method for measuring position error of robot end effector - Google Patents
Method for measuring position error of robot end effector Download PDFInfo
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- CN109489555B CN109489555B CN201910004521.7A CN201910004521A CN109489555B CN 109489555 B CN109489555 B CN 109489555B CN 201910004521 A CN201910004521 A CN 201910004521A CN 109489555 B CN109489555 B CN 109489555B
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
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Abstract
The invention discloses a method for measuring position errors of a robot end effector, belongs to the field of industrial robots, and provides a method for acquiring position information of the end effector at a working position accessory by adopting a method of shooting images by a camera. The method is characterized in that the industrial robot is driven to reach different positions of an operation area, the positions of a needle point image and a calibration board graph in a camera are analyzed and calculated, and the position error of the industrial robot is obtained. The size and the placement position of the calibration plate can be designed according to the actual target working area, so that the method has better flexibility; the calibration operation can be carried out only by machine vision matching devices such as an industrial camera and the like, and the calibration system is simple.
Description
Technical Field
The invention belongs to the technical field of robots, and relates to a method for measuring position errors of a robot end effector.
Background
With the great development of automation technology and robotics, it has a profound effect on precision assembly. In the automatic robot assembly technology, the low positioning accuracy of the robot becomes a bottleneck restricting the application of the robot to high-accuracy assembly. How to calibrate the robot fast and effectively has very important meaning to the improvement of robot assembly precision, plays the key role to reducing the assembly error.
The positioning accuracy of the robot comprises two important indexes, namely the absolute positioning accuracy of the robot, which refers to the capability of the robot to reach a certain space point; the other is the repeated positioning precision of the robot, which refers to the ability of the robot to reach a certain point repeatedly after teaching the point in space. Generally speaking, the repeated positioning precision of the robot is higher and can reach +/-0.03-0.05 mm, but the absolute positioning precision of the robot is lower and can reach millimeter magnitude. Because the robot needs to be programmed off-line before working, and because the virtual working environment and the real working environment have deviation, the robot needs to be calibrated before working normally, so as to improve the absolute position precision of the robot.
The calibration method generally comprises the four steps of ① kinematic modeling, ② data measurement, ③ parameter identification, ④ error compensation, welding, 2017(12), 17-22, welding robot system calibration technical research, wherein data measurement is to measure robot posture data and mainly comprises measurement by means of external precise equipment, such as application of a laser tracker (laser tracker) in robot posture characteristic detection, machine tools and hydraulic pressure, 2018(46) 21: 29-33), a ball rod instrument and a three-coordinate measuring machine (three-dimensional surface scanning robot system body calibration new method, mechanical engineering report, 2011(47)17: 9-14) and the like.
In summary, at present, a method for quickly and accurately acquiring data during calibration of a robot at a working position accessory still needs to be researched and developed so as to simplify a calibration process and improve the positioning accuracy of the calibrated robot.
Disclosure of Invention
The invention provides a method for measuring position errors of a robot end effector, which adopts a method of shooting images by a camera to complete the acquisition of position information of the end effector near a working position.
The end effector of the robot is equipped with a calibration needle. And manufacturing a calibration plate and placing the calibration plate in a working area. And moving the camera driving mechanism to enable the calibration graph on the calibration plate to clearly enter the visual field of the camera. And driving the robot to reach different positions of the operation area, analyzing and calculating the positions of the needle point image and the calibration board image in the camera to obtain the position error of the robot, and providing a data basis for a positioning precision compensation algorithm.
The technical scheme of the invention is as follows:
a method for measuring position errors of a robot end effector comprises the following steps:
(1) a calibration needle is arranged on the robot end effector, a calibration plate is fixed at the working position of the robot, and a camera driving mechanism moves a camera to automatically focus the camera; shooting an image by a camera to obtain the position relation between the calibration needle and the calibration pattern on the calibration plate;
(2) driving the robot to move the calibration needle to the set calibration position, recording the position information of the robot, and the position (X) of the nth point in the robot coordinate systemn，Yn，Zn) (ii) a Through image processing, the position (X ') of the calibration needle on the calibration plate is obtained'n，Y’n，Z’n)；
(3) If the moving distance of the calibration needle is smaller and is within the field of view of the camera, the camera does not need to be moved;
if the moving distance of the calibration pin is larger and exceeds the field of view range of the camera, a camera driving mechanism needs to be driven, so that the images on the calibration pin and the calibration plate are in the field of view range of the camera, and the driving distance of the camera in a robot coordinate system needs to be introduced when the position deviation of the robot movement is calculated; the coordinate systems of the robot, the calibration plate and the camera driving mechanism are parallel and have the same direction, and the driving displacement of the camera is defined as (X)n camera，Yn camera，Zn camera) When calculating the position deviation of the robot movement, linearly superposing the position deviation with other two coordinate system values; the positional deviation of the robot movement at this time is:
ΔXn＝(X’n-X’n-1)+Xn camera-(Xn-Xn-1)，
ΔYn＝(Y’n-Y’n-1)+Yn camera-(Yn-Yn-1)，
ΔZn＝(Z’n-Z’n-1)+Zn camera-(Zn-Zn-1)。
When n is 1, that is, the first point, both are considered to have no position error.
And finishing the position errors of all points needing to be calibrated of the robot, inputting the position errors into a position compensation algorithm formula, and obtaining the position compensation quantity of the position working point in the working area.
The invention has the advantages that: the manufacturing precision of the pattern on the calibration plate can reach 1 micron, so the calibration precision is high; the size and the placement position of the calibration plate can be designed according to the actual target working area, so that the calibration plate has better flexibility; the calibration operation can be carried out only by machine vision matching devices such as an industrial camera and the like, and the calibration system is simple; the position error of the robot end effector obtained after calibration can be used for calibrating the positioning precision of the robot, and the method has practical value.
Drawings
FIG. 1 is a schematic diagram of the measurement of the present invention.
Fig. 2 is a calibration plate of the present invention.
Fig. 3 is a calibration image taken by the camera.
In the figure: 1, a robot; 2 marking the needle; 3, calibrating the plate; 4, a camera; 5 a camera driving structure; 6 calibrating the graph; 7 calibrating the line sequence number of the graph; 8, calibrating the column serial number of the graph; 9 a calibration needle image of the first calibration point; 10 a stylus image of a second index point.
Detailed Description
The specific implementation steps of the invention are described in combination with the technical scheme and the attached drawings in the specification.
The camera 4 in the specific embodiment is driven by a guide rail, the motion resolution of the guide rail is 1 micron, and the driving shaft of the camera driving mechanism 5 and the X, Y, Z of the robot 1 are respectively parallel. The field of view of the camera 4 is 7.38mm by 4.91 mm. The cross pattern on the calibration plate 3, the "horizontal" and "vertical" of the cross are rectangles with the size of 0.05mm x 0.5mm, the space between the cross and the cross pattern is 1.5mm, and the size deviation of the image is less than +/-0.5 microns.
The numbers of the second quadrant of the calibration cross figure represent the row serial numbers of the calibration figure, the numbers of the first quadrant of the calibration cross figure represent the column serial numbers of the calibration figure, and the calibration image is marked as (row serial number and column serial number) so as to quickly obtain the position of the calibration needle image in the calibration plate.
The XYZ axes of the robot are at the base. The X 'Y' Z 'axis of the calibration plate, as shown in fig. 1 and 2, has the zero point of the Y' axis at the position of the camera driving structure when obtaining a clear first calibration point image, and the zero points of X 'and Z' are at the center point of the calibration point image (54, 1).
Firstly, mounting a calibration needle 2 on an end effector of a robot 1, placing a calibration plate 3 at the working position of the end effector of the robot 1, driving a camera 4 to automatically focus so that the camera can clearly see an image on the calibration plate 3, and recording the numerical value of a camera driving structure 5 at the moment as Y1’＝0。
Secondly, the robot 1 is driven to move the calibration needle 2 to the position required for calibration, and for the convenience of image processing, the position is usually at the blank of the calibration graph 6 close to the cross point to obtain a calibration needle image 9 of the first calibration point, and the position information of the robot is X at this moment1＝330，Y1＝95，Z1＝545。
Third, the position of the image on the calibration plate, X, is obtained1’＝0.075，Y1’＝0，Z1' -2.075, no position error.
And fourthly, sequentially moving the calibration needle 2 to the calibration required position and shooting an image. If the moving distance of the calibration pin 2 is small and within the field of view of the camera 4, the camera 4 does not need to be moved; if the movement distance of the calibration pin 2 is large and exceeds the field of view range of the camera 4, the camera driving mechanism 5 is driven so that the images on the calibration pin 2 and the calibration plate 3 are within the field of view range of the camera 4. In practice, the second index point is the position information of the robot X2＝366，Y2＝95，Z2The amount of movement of the camera drive mechanism 5 is X503Camera with a camera module＝30，YCamera with a camera module＝0，ZCamera with a camera module＝-40。
Fifthly, obtaining the position of the calibration needle image 10 of the second calibration point in the coordinate system of the calibration plate as X by using image processing software2’＝5.825，Y2’＝0，Z2' -4.095, so the position error of the robot is Δ X2＝(5.825-0.075)+30-36＝-0.25，ΔY2＝0，ΔZ2＝(-4.095+2.075)-40-(-42)＝-0.02。
The sixth stepAnd the position information of the third calibration point robot is X3＝336，Y3＝92，Z3543, the moving camera driving mechanism 5 automatically focuses to obtain that the camera driving guide rail moves by-3.08 mm along the Y' axis, and the position of the robot in the coordinate system of the calibration plate is obtained as X3’＝5.825，Y3’＝-3.08，Z3' -4.095, position error Δ X3＝0，ΔY3＝0-3-(-3.08)＝0.08，ΔZ3＝0。
And completing the position errors of all points needing to be calibrated by the robot according to the methods from the second step to the sixth step.
Claims (1)
1. A method for measuring position errors of a robot end effector is characterized by comprising the following steps:
(1) a calibration needle is arranged on the robot end effector, a calibration plate is fixed at the working position of the robot, and a camera driving mechanism moves a camera to automatically focus the camera; shooting an image by a camera to obtain the position relation between a calibration needle and a calibration graph on a calibration plate;
(2) driving the robot to move the calibration needle to the set calibration position, recording the position information of the robot, and the position (X) of the nth point in the robot coordinate systemn、Yn、Zn) (ii) a Through image processing, the position (X ') of the calibration needle on the calibration plate is obtained'n、Y’n、Z’n)；
(3) If the moving distance of the calibration needle is smaller and is within the field of view of the camera, the camera does not need to be moved;
if the moving distance of the calibration pin is larger and exceeds the field of view range of the camera, a camera driving mechanism needs to be driven, so that the images on the calibration pin and the calibration plate are in the field of view range of the camera, and the driving distance of the camera in a robot coordinate system needs to be introduced when the position deviation of the robot movement is calculated; the coordinate systems of the robot, the calibration plate and the camera driving mechanism are parallel and have the same direction, and the driving displacement of the camera is defined as (X)n camera、Yn camera、Zn camera) When calculating the position deviation of the robot movement, the method is linear with other two coordinate system valuesSuperposing; the positional deviation of the robot movement at this time is:
ΔXn＝(X’n-X’n-1)+Xn camera-(Xn-Xn-1)，
ΔYn＝(Y’n-Y’n-1)+Yn camera-(Yn-Yn-1)，
ΔZn＝(Z’n-Z’n-1)+Zn camera-(Zn-Zn-1)；
When n is 1, namely the first point, the two are considered to have no position error;
and finishing the position errors of all points needing to be calibrated of the robot, inputting the position errors into a position compensation algorithm formula, and obtaining the position compensation quantity of the position working point in the working area.
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| CN111659633A (en) * | 2020-06-05 | 2020-09-15 | 珠海格力智能装备有限公司 | Tooling product classification system and method |
| CN113858265B (en) * | 2020-06-30 | 2023-07-18 | 上海微创数微医疗科技有限公司 | Method and system for detecting pose errors of mechanical arm |
| CN118442924B (en) * | 2024-07-08 | 2024-09-24 | 迈为技术(珠海)有限公司 | Shafting precision measurement method and device, spining equipment and storage medium |
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| CN100557378C (en) * | 2008-04-11 | 2009-11-04 | 华南农业大学 | Machinery and visual related positioning experiment platform |
| CN105066884B (en) * | 2015-09-09 | 2018-07-06 | 大族激光科技产业集团股份有限公司 | A kind of robot end's deviations bearing calibration and system |
| JP2017071033A (en) * | 2015-10-09 | 2017-04-13 | キヤノン株式会社 | Working reference object, working reference object manufacturing method, robot arm adjusting method, vision system, robot apparatus, and indicator member |
| CN105945909A (en) * | 2016-05-13 | 2016-09-21 | 大族激光科技产业集团股份有限公司 | Error correction method and system for three-degree-of-freedom parallel robot |
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