TW201900358A - Method for calibrating coordinator of robot arm - Google Patents

Abstract

The invention is to disclose a method for calibrating the coordinator of a robot arm, snapshotting the image of a square calibration pate, discriminating the four corners of the calibration pate with the color difference, calculating the center coordinator with the crossover point of diagonals, aligning the central shaft line of the camera with the center, filtering the laser beam with the calibration pate of deep color, achieving two light end points at the two sides of the calibration pate, forming a laser line, guiding the laser line to overlap the center, and acquiring TCP coordinator for automatic calibration.

Description

 Method of correcting coordinates of robot arm  

The present invention relates to a robotic arm, and more particularly to a coordinate correction method for an industrial robotic arm and its tool center.

The robotic arm has the characteristics of flexible movement, precise positioning and continuous operation, although it has become the best tool for manufacturing and assembly on the production line. However, the robot arm drives the assembly, wear and component assembly errors of the multi-axis actuator to form a difference between the control and the actual moving coordinates, resulting in inaccurate positioning. Therefore, correcting the coordinates is an important issue for the robot arm.

When the prior art corrects the coordinates of the robot arm, it usually drives the robot's Tool Center Point (TCP) to directly contact the reference point of the known coordinate to correct the coordinates of the robot's tool center point. However, the uncorrected robot arm often collides with the reference point when the movement error is too large, causing damage to the robot's tool and reference point instrument. Therefore, there is another prior art that uses a precision measuring instrument such as a laser range finder to measure the coordinates of the center point of the tool. Although the coordinate can be non-contact-corrected, the laser range finder is expensive and requires a large installation. Space, forming a limit on the use. Therefore, in the prior art U.S. Patent Publication No. US20110320039, a black-and-white correction plate is set in a specific relationship between the opposite coordinates of the robot arm, and the image of the black and white correction plate is captured by the camera on the robot arm to calculate the camera and The relative relationship of the calibration plates of the coordinates is known to correct the robotic arm.

However, although the aforementioned prior art robot arm can be automatically corrected without contact, there are various types of calibration plates of various manufacturers, and each type of calibration plate has its own unique installation structure and a relative relationship of calculation, and cannot be used interactively or compatiblely. For general operators who use a variety of models or brand robots, it is not easy to use maintenance management. Therefore, the robot arm still has problems to be solved on the calibration coordinates.

The object of the present invention is to provide a method for correcting coordinates of a robot arm, which uses a camera on a robot arm to capture an image of a calibration block, and identifies four corners of the calibration block by calibrating the difference between the square and the environment to obtain a center point coordinate to quickly align the camera. The central axis.

The object of the present invention is to provide a method for correcting coordinates of a robot arm, which uses a dark calibration block to filter laser light, obtains bright end points of the edge of the calibration block, forms a lightning ray strip, and then guides the lightning ray strip to coincide with the calibration square along the central axis of the camera. Center point to automatically correct the coordinates of the TCP.

Another object of the present invention is to provide a method for correcting coordinates of a robot arm. A calibration block of a plurality of orientations is set in a calibration target, and coordinates of different robot arms are used, coordinates of the calibration target are corrected, and coordinates of the TCP are corrected to automatically correct the robot arm. The coordinates of the coordinates.

In order to achieve the object of the foregoing invention, the method for correcting coordinates of the robot arm of the present invention has a fixed relative relationship between the camera of the robot arm and the laser device, and adjusts the intersection of the central axis of the camera and the laser light of the laser device as a tool center point, and then Place the calibration block, use the camera to capture the image of the calibration block, distinguish the four corners of the calibration block through image processing, use the diagonal intersection to obtain the coordinates of the center point of the calibration block, move the center axis of the camera to align the center point of the square, and filter Projecting the laser light to the calibration block, obtaining the bright end points of the two edges of the calibration block, establishing a lightning ray strip, moving the camera to drive the lightning ray strip to coincide with the center point of the calibration square while maintaining the center axis of the camera against the center of the calibration square Set the coordinates of the center point of the calibration block to the center point of the control tool.

The calibration block of the method for correcting coordinates of the robot arm of the present invention is an identifiable color or a dark or black positive square for absorbing the projected laser light, and a bright end point which produces a significant difference in brightness at both edges of the calibration block to obtain two bright End point. When coincident, the coordinates of the center point of the calibration block fall on the lightning ray strip, and the relative fixed relationship of the center point of the camera, the laser device and the calibration block is recorded when the coincidence is recorded. In addition, when the center point of the calibration block is placed, the actual measurement coordinates are used as the actual tool center point coordinates, and the coordinates of the center point coordinate of the control tool and the actual tool center point coordinate are obtained to correct the coordinates of the center point of the robot tool.

In another embodiment of the present invention, a method for correcting coordinates of a robot arm has a fixed relative relationship between a camera of a robot arm and a laser device, and then a calibration target having a known coordinate and including a calibration block is fixed at a position relative to the robot arm, and the target is corrected. For the cube and set the multiple calibration blocks on each plane, use the posture of the robot to drive the camera to capture the image of the calibration target, automatically select a calibration square on the calibration target, and distinguish the four corners of the calibration block by image processing. The intersection of the corner lines obtains the coordinates of the center point of the calibration block, the center axis of the moving camera is aligned with the center point of the calibration block, and the laser light projected to the calibration block is filtered to obtain the bright end points of the two edges of the calibration block, and the thunder beam is established. While maintaining the central axis of the camera aligned with the center point of the calibration block, the moving camera drives the lightning ray bar to coincide with the center point of the calibration block, and when coincident, records the control coordinates of the center point of the calibration block, and checks that the number of postures of the robot arm does not reach When the threshold is preset, changing the posture of the robot arm drives the camera When the complex correction step, the number of position inspection robot arm reaches a preset threshold, the control center point coordinates of the calibration block acquired, calculating the number of columns into rows of the matrix, to obtain correction parameters for correcting the coordinates of the robotic arm.

1‧‧‧Machine arm

2‧‧‧Axis arm

3‧‧‧Actuator

4‧‧‧Base

5‧‧‧End device

6‧‧‧ camera

7‧‧‧ Laser device

8‧‧‧Working rack

9‧‧‧ calibration block

10‧‧‧Laser light

11‧‧‧ center axis

12‧‧‧ images

13‧‧‧ four corners

14‧‧‧ center point

15‧‧‧Ray Bar

16‧‧‧ bright end

17‧‧‧ calibration target

TCP‧‧‧Tool Center Point

Figure 1 is a schematic view of the correction arm of the robot arm of the present invention.

2 is a calibration block image of the camera captured by the present invention.

3 is a schematic view of a moving lightning ray strip of the present invention.

4 is an image diagram of a center point of a lightning bar coincidence calibration block of the present invention.

Figure 5 is a flow chart of a method for correcting coordinates of a robot arm of the present invention.

6 is a schematic diagram of a robot arm correction coordinate according to another embodiment of the present invention.

7 is a flow chart of a method for correcting coordinates of a robot arm according to another embodiment of the present invention.

The technical means and the efficacies of the present invention for achieving the above objects are as follows, and the preferred embodiments are described below with reference to the drawings.

Please refer to FIG. 1 and FIG. 2 simultaneously. FIG. 1 is a schematic diagram of the calibration of the TCP coordinates of the robot arm of the present invention, and FIG. 2 is a calibration block image of the camera captured by the present invention. The robot arm 1 of the present invention in FIG. 1 is formed by a plurality of axial arms 2 spaced apart in series with an actuator 3, one end of which is fixed to the base 4, forming a robot arm coordinate M, and the other end is at the last end of the shaft arm 2, the end device 5, the end device 5 The coordinates of the coordinates M of the robot arm can be calculated by the rotation record of the actuator 3. The camera 6 and the laser device 7 are disposed on the terminal 5, and the camera 5 has a fixed relative relationship with the end device 5, so that the coordinates of the robot arm coordinate M can also be calculated. The robot arm 1 drives the image of the calibration block 9 on the work frame 8 (see Fig. 2), and the laser device 7 emits the planar scanning laser light 10. The camera 6 of the present invention has a fixed relative relationship with the laser device 7, and the intersection of the central axis 11 of the setting camera 6 and the scanning device 10 for scanning the laser light 10 is a tool center point (TCP).

Since the virtual central axis 11 of the camera 6 and the intersection of the laser device 7 scanning the laser light 10 are not visible, the TCP of the robot arm cannot be directly determined visually. In order to obtain the coordinates of the robot arm TCP, the calibration block 9 is placed on the work frame 8, and the calibration block 9 can be a black positive square. The calibration block 9 of this embodiment is illustrated by a black square, but includes and is not limited to black. Positive squares, which are easily recognizable colors or dark colors, and which are easy to determine the center point, are within the scope of the invention.

The robot arm 1 of the present invention drives the camera 6 to capture the image 12 of the calibration block 9 on the work frame 8, such as the image 12 of the calibration block 9 in FIG. 2, and uses the camera 6 to capture the focal length of the image 12, the center of the image 12, and the pixels. The coordinates of the points of the image 12 can be calculated by the camera 6 of the known coordinates. Since the black calibration block 9 in the image 12 is significantly different from the surrounding light color environment, the calibration block 9 can be quickly distinguished through the image processing, and the coordinates of the four corners 13 of the calibration block 9 are determined, and the diagonal intersection of the squares of the calibration squares 9 is formed. At center point 14, the coordinates of the center point 14 of the calibration block 9 are obtained. The camera 6 is then used to drive the camera 6 so that the central axis 11 of the camera 6 aligns the center point 14 of the square 9.

In Fig. 2, the laser device 7 emits a planar scanning laser light 10, and in the image 12, a thunder beam 15 traversing the calibration block 9 is formed. The thunder beam 15 of the laser light is relatively bright, but is projected in a black calibration block. The thunder beam 15 of 9 is absorbed by the black calibration block 9 and the brightness is relatively dimmed. Therefore, the bright end point 16 which produces a significant difference in brightness at both edges of the calibration block 9 is used to obtain the coordinates of the two bright end points 16 and utilize The line formed by the two bright ends 16 positions the lightning ray strip 15.

Please refer to FIG. 3 and FIG. 4 at the same time. FIG. 3 is a schematic diagram of a moving lightning ray strip according to the present invention, and FIG. 4 is an image diagram of a center point of a lightning ray strip coincident calibration block according to the present invention. In FIG. 3, while maintaining the central axis 11 of the camera 6 against the center point 14 of the positive calibration block 9, the robotic arm drives the camera 6 to move the laser device 7 along the central axis 11 to cause the laser beam 15 emitted by the laser device 7 to move. Point to the center point 14 of block 9. In Fig. 4, when the coordinates of the center point 14 fall on the thunder beam 15, it is confirmed that the thunder beam 15 coincides with the center point 14. The relative fixed relationship between the camera 6, the laser device 7, and the center point 14 is recorded, and the focal length of the image 12, the center of the image 12, and the pixels are captured by the camera 6, and the coordinates of the center point 14 are calculated, and the coordinates of the center point 14 are set. The coordinates of the TCP.

The coordinates of the aforementioned TCP are the control TCP coordinates obtained according to the robot arm control. If the robot arm has been corrected, the control TCP coordinates are the actual TCP coordinates. Otherwise, when the calibration block 9 is placed on the work frame 8, the coordinates of the center point 14 of the calibration block 9 can be actually measured, and the coordinate of the center point 14 is used as the actual TCP coordinate, and the center point of the TCP coordinate and the actual measurement is controlled by the comparison. The coordinates of 14 obtain the error of controlling the TCP coordinates and the actual TCP coordinates, and further correct the coordinates of the robot arm TCP.

As shown in FIG. 5, it is a flowchart of a method for correcting coordinates of a robot arm of the present invention. The detailed steps of the method for correcting the coordinates of the robot arm of the present invention are as follows: in step S1, when the TCP is started to be corrected, the camera of the present invention has a fixed relative relationship with the laser device, and the central axis of the camera is adjusted and the laser device is scanned for the laser light. The intersection point is TCP; in step S2, the calibration block is placed; in step S3, the image of the calibration block is captured by the camera; in step S4, the calibration block is distinguished by image processing, the four corners of the calibration block are obtained, and the center of the calibration block is obtained by intersecting the diagonal lines. Point coordinates; then, in step S5, the center axis of the moving camera is aligned with the center point of the square; in step S6, the laser device emits the laser light in the calibration block, and obtains bright bright ends of the two sides of the calibration block to establish a lightning ray strip. Step S7, while maintaining the center axis of the camera facing the calibration square, moving the camera to drive the lightning ray strip so that the lightning ray strip coincides with the center point of the calibration square; step S8, recording the coincidence camera, laser device and center The relative fixed relationship of the points, the coordinates of the center point are set to control the TCP coordinates; in step S9, the TCP block is controlled The calibration is corrected for the known actual coordinates of the center point of the calibration block; then, at step S10, the TCP coordinate correction is ended.

Therefore, the method for correcting the coordinates of the robot arm of the present invention can use the camera on the robot arm to capture the image of the calibration block, and by identifying the difference between the color of the calibration block and the environment, quickly identify the coordinates of the four corners of the calibration block, from the diagonal The intersection of the lines calculates the coordinates of the center point, allowing the robot to automatically move the center axis of the camera and quickly align the center point. Then use the dark calibration block to filter the laser light, obtain the bright end points of the two edges of the calibration block, form the lightning ray strip, and then let the camera guide the lightning ray strip along the central axis to coincide with the center point of the calibration square, and avoid the damage under non-physical contact. The obtained TCP coordinates are compared with the actual measured center point coordinates to further achieve the purpose of automatically correcting the TCP coordinates.

FIG. 6 is a schematic diagram of a method for correcting coordinates of a robot arm according to another embodiment of the present invention. This embodiment basically uses the technique of correcting the TCP coordinates of the foregoing embodiment to perform the correction of the coordinates of the robot arm. In order to simplify the description, the same components as the previous embodiment are used in the same part number, which will be described first. In this embodiment, a plurality of calibration blocks 9 are respectively disposed on the respective planes of the correction target 17, and the correction target 17 is disposed at a fixed position relative to the base 4 of the robot arm 1 and has a known robot arm coordinate. The correction target 17 of the present embodiment is illustrated by a cube, but includes, but is not limited to, a cube, such as a polyhedron.

Then, the robot arm 1 is corrected, and the camera 1 drives the camera 6 to capture the image of the calibration target 17, and automatically selects a calibration block 9 on the calibration target 17, and performs the TCP correction step of the previous embodiment, that is, the selected calibration block 9 is captured. The image identifies the four corners of the calibration block 9, the center point of the calibration block 9 is determined by the diagonal line, the central axis 11 of the camera 6 is automatically moved to align the center point of the square 9, and then the laser device 7 is projected to project the laser light to form a thunder. The ray strip moves the camera 6 along the central axis 11 to cause the lightning ray strip to coincide with the center point of the calibration block 9, which is considered to coincide with the center point of the TCP to obtain the controlled TCP coordinates as the center of the selected calibration block 9. The control coordinates of the point. Then changing the posture of the robot arm 1, selecting another calibration block 9, repeating the aforementioned TCP correction step until the number of postures of the robot arm 1 is changed to a preset threshold, and then the control coordinates of the center point of the obtained calibration block 9 are A matrix sequence calculation of a prior art such as the Jacobian Matrix is performed to obtain coordinates correction parameters to complete the correction of the robotic coordinates.

FIG. 7 is a flow chart of a method for correcting coordinates of a robot arm according to another embodiment of the present invention. The detailed steps of the method for correcting coordinates of the robot arm in this embodiment are as follows: in step T1, the coordinates of the robot arm are started to be corrected; in step T2, the correction target including the known coordinates and including the calibration block is set at a fixed position relative to the robot arm; T3, automatically selects a calibration block on the calibration target to perform TCP correction; in step T4, records the selection center point control coordinate of the calibration block; then, in step T5, checks whether the number of postures of the changing robot arm reaches a preset threshold value. If the number of postures does not reach the preset threshold, proceed to step T6 to change the posture of the robot arm, and then return to step T3 to repeat the step. If the number of postures reaches the preset threshold, proceed to step T7 to obtain the center point of the calibration block. The control coordinates are subjected to matrix sequence calculation to obtain correction parameters for correcting the robot arm coordinates; then, at step T8, the coordinate correction is ended.

Therefore, in the method for correcting the coordinates of the robot arm of the present invention, a calibration block of a plurality of orientations can be set in the calibration target, and the coordinates of the different robot arms can be used to correct the coordinate coordinates of the calibration target, and then the obtained calibration block is obtained. The coordinates of the center point are used to calculate the calibration parameters using the matrix sequence to achieve the purpose of automatically adjusting the coordinates of the robot arm without contact.

The above is only a preferred embodiment for facilitating the description of the present invention, and the scope of the present invention is not limited to the preferred embodiments, and any changes made in accordance with the present invention may be made without departing from the spirit of the present invention. All of them are within the scope of the patent application of the present invention.

Claims (10)

 A method for correcting a coordinate of a robot arm, the camera of the robot arm and the laser device having a fixed relative relationship, adjusting an intersection point between a central axis of the setting camera and the laser light of the laser device as a tool center point, the step comprising: placing a calibration block; Using the camera to capture the image of the calibration block; distinguishing the four corners of the calibration block by image processing, using the diagonal intersection to obtain the coordinates of the center point of the calibration block; moving the center axis of the camera to align the center point of the square; filtering and projecting to the calibration block Laser light, obtain the bright end of the two edges of the calibration block, establish a lightning ray strip; while maintaining the center axis of the camera to align the center point of the square, move the camera to bring the lightning ray strip to coincide with the center point of the calibration square; The coordinates of the center point of the calibration block are set to control the tool center point coordinates.    The method for correcting coordinates of a robot arm according to claim 1, wherein the calibration block is a black square.    The method for correcting coordinates of a robot arm according to claim 1, wherein the calibration block absorbs the projected laser light, and produces bright end points with significant brightness differences at both edges of the calibration block to obtain two bright end points.    The method for correcting a coordinate of a robot arm according to claim 1, wherein the coordinate coincident with a center point of the calibration block falls on the lightning ray strip.    A method of correcting coordinates of a robotic arm as claimed in claim 4, wherein the coincidence records a relative fixed relationship of a center point of the camera, the laser device, and the calibration block.    The method for correcting coordinates of a robot arm according to claim 1, wherein the center point of the calibration block is actually measured as a coordinate point of the actual tool center point, compared with the center point coordinate of the control tool and the actual tool center point. The coordinates get an error to correct the coordinates of the center point of the robot tool.    A method for correcting coordinates of a robot arm, the camera of the robot arm having a fixed relative relationship with the laser device, the steps comprising: setting a calibration target having a known coordinate and including the calibration block at a fixed position relative to the robot arm; using the robot arm The gesture drives the camera to capture the image of the calibration target, automatically selects a calibration block on the calibration target; distinguishes the four corners of the calibration block by image processing, and obtains the coordinates of the center point of the calibration block by diagonal intersection; moving the central axis of the camera Aligning the center point of the calibration block; filtering the laser light projected onto the calibration block, obtaining the bright end points of the two edges of the calibration block, and establishing a lightning ray strip; moving the center axis of the calibration frame while maintaining the center axis of the camera The camera drives the lightning ray bar to coincide with the center point of the calibration block; when coincidently, records the control coordinate of the center point of the calibration block; when the number of postures of the robot arm reaches a preset threshold, the control coordinates of the center point of the calibration block to be obtained are obtained. , perform matrix number calculation, obtain calibration parameters, and perform calibration machine Arm coordinates.    The method for correcting coordinates of a robot arm according to claim 7, wherein when the number of postures of the robot arm is not up to a preset threshold, changing the posture of the robot arm causes the camera to repeat the correcting step.    The method of correcting coordinates of a robot arm according to claim 7, wherein the correction target is a cube.    The method for correcting coordinates of a robot arm according to claim 9, wherein the calibration target sets a plurality of calibration blocks on each of the planes.