TW201603979A - Calibration device and method for robot arm - Google Patents

Abstract

A calibration device and method is disclosed for a robot arm. An encoded calibrating plate is fixed in the working environment of the robot arm and the encoded calibrating plate has chessboard pattern with the coordinate encoding. The coordinate encoding indicates the position of the encoded calibration plate. The visual system of the robot arm catch the image of the encoded calibrating plate and calculate the coordinate encoding to position the visual system and the positioning error of the robot arm and the visual system can be calibrated.

Description

Correction device and method for robot arm

The invention relates to a device and a method for correcting a robot arm, in particular to a device and a method for correcting a movement error of a robot arm by using a vision system and a code correction plate.

With the rapid development of industrial production technology, in order to pursue the speed of mass production, the stability of product quality and the reduction of labor costs, the factory production line has replaced the labor force with the robot arm to carry out the workpiece picking, arranging or assembling. The automated robotic arm further uses the vision system to position the workpiece and position it, guiding the robotic arm to automatically and accurately grasp the workpiece for assembly and manufacturing. How to reduce the error of the positioning of the vision system and correct the accuracy of the movement of the robot arm has become an important issue for the robot arm.

Please refer to FIG. 1 , which is a standard calibration plate 10 of the prior art robot arm, wherein the standard calibration plate 10 is a rectangular lattice plate, and the black lattice 11 and the white lattice 12 are spaced apart from each other. When the standard calibration plate 10 corrects the robot arm, it mainly passes through the vision system of the robot arm (not shown). The vision system includes an EIH (Eye in Hand, EIH) camera on the robot arm to guide the robot arm to grasp. The workpiece, as well as an ETH (Eye to Hand, ETH) camera outside the robot arm, is used to monitor the working environment of the robot arm. Taking the EIH camera mounted on the robot arm as an example, the mobile robot arm is used to drive the EIH camera to approach the standard calibration plate 10, and focus on the image of the standard calibration plate 10 captured in the EIH camera, according to the capture. The image of the standard calibration plate 10, the relative positional relationship between the computing robot arm and the standard calibration plate 10, completes the correction of the robot arm.

The reference standard calibration plate has a variety of correction methods, such as the prior art U.S. Patent No. 6,985,175, which utilizes two cameras to capture the distorted image condition of the standard calibration plate, and performs image comparison to correct the camera. In addition, the Chinese patent case CN102927908 uses a laser device to project strip light on the opposite side of the standard calibration plate. The camera on the robot arm captures the image of the strip light, and then moves the laser device and the robot arm to pick up the strip light. The image of the other diagonal position of the projection standard calibration plate is corrected by the intersection of the strip rays at two diagonal positions to correct the positioning of the three-dimensional space of the robot arm.

However, the standard calibration plate used in the foregoing prior art has a certain size and is in the same lattice shape of black and white. For example, when the space provided by the robot arm is limited, and the relative distance between the robot arm and the standard calibration plate is insufficient, the vision mounted on the robot arm is The system cannot obtain all the complete images of the standard calibration plate. It is difficult to determine the relative direction and position of the partial image of the standard calibration plate, so that the visual system on the robot arm and the standard calibration plate cannot be correctly corrected for relative coordinates. Therefore, the robot arm still has problems to be solved in the calibration device and method.

The object of the present invention is to provide a robot arm correcting device, which is provided with a plurality of coordinate codes on a code correction plate, and the coordinate code has a preset coordinate, so that the robotic vision system can capture the coordinate code of the local code correction plate. Quickly obtain position correction to increase the flexibility of the robot arm setting space.

Another object of the present invention is to provide a method for correcting a robot arm, which utilizes a vision system of a robot arm to focus on an image of a coding correction plate coordinate code, and calculates a coordinate of the coordinate code. Set the coordinates to position the vision system to correct the robot arm.

Still another object of the present invention is to provide a method for correcting a robot arm, which utilizes a robotic arm movement vision system, multi-faceted focusing to capture an image of a coding correction plate coordinate code, and an average visual system positioning error to improve the accuracy of the robot arm correction.

Another object of the present invention is to provide a method for correcting a robot arm, which uses an encoder calibration plate to sequentially position an ETH camera and an EIH camera of a robot arm to correct the robot arm.

In order to achieve the object of the foregoing invention, the correcting device for the robot arm of the present invention has one end of the robot arm fixed to the base and the other end provided with a movable end on which the EIH camera of the vision system is fixed. The code correction plate is fixed in the working environment of the robot arm by the support frame, and has a fixed relative coordinate with the robot arm. The code correction plate is a checkerboard pattern, and the coordinate code is marked in the grid to indicate the direction and position of the code correction plate, and the control device utilizes Receiving the image captured by the vision system, controlling the EIH camera on the active end of the robot arm to capture the coordinate code of the code correction plate to correct the positioning error of the robot arm and the EIH camera. The vision system additionally includes an ETH camera. The ETH camera is fixed to the outside of the robot arm and has a fixed relative coordinate with the robot arm. The control device moves the movable end of the robot arm to a position of a plurality of predetermined coordinate codes on the code correction plate to correct the robot arm. Positioning error with ETH camera.

The lattice of the code correction plate of the present invention is composed of a black grid and a white grid spaced apart from each other. In the upper left corner of each black grid, the direction circle of the direction circle is coded to indicate the direction of the coordinate origin of the coordinate correction plate. The coding circle of the hollow circle and the solid circle is arranged in the white grid to form a position coordinate code to indicate the position of the coordinate origin of the coordinate correction plate. The coded circle in the white grid is arranged in two rows, the first row represents the X axis and the second row represents the Y axis, and each row has a coding circle of the first column A, the second column B, and the third column C, the position is determined by The bottom to top is represented as 0 to the 2nd power of 2, and the coordinate formula of the white lattice is: X=A*2 ⁰ +B*2 ¹ +C*2 ²

Y=A*2 ⁰ +B*2 ¹ +C*2 ²

The method for correcting the robot arm of the present invention fixes the code correction plate with a preset coordinate in the photographing range of the robotic vision system; uses the robotic vision system to focus the captured code correction plate image; and according to the captured code correction plate Image and focal length, calculate the coordinate code of the coding correction plate, locate the vision system; compare the positioning of the vision system and correct the front coordinates; correct the movement error of the robot arm.

The vision system of the robot arm correction method of the present invention comprises an ETH camera and an EIH camera, and respectively performs positioning correction of the ETH camera and the EIH camera. After the EIH camera is calibrated, the number of predetermined corrections is insufficient. The mobile robot arm captures the different coordinate codes of the code correction plate and continues to correct. When the number of corrections is sufficient, the average movement error is corrected for the robot arm.

20‧‧‧Code Correction Board

21‧‧‧Black plaid

22‧‧‧White plaid

23‧‧‧ Directional circle

24‧‧‧ hollow circle

25‧‧‧ Solid circle

26‧‧‧Partial imagery

30‧‧‧ calibration device

31‧‧‧Machine arm

32‧‧‧Control device

33‧‧‧ active end

34‧‧‧EIH camera

35‧‧‧Base

36‧‧‧Support frame

37‧‧‧Clamping mechanism

40‧‧‧ETH camera

Figure 1 is a schematic diagram of a prior art standard calibration plate.

2 is a schematic diagram of a code correction plate of the present invention.

3 is a schematic view of a method of correcting a robot arm of the present invention.

4 is a flow chart of a method of correcting a robot arm of the present invention.

FIG. 5 is a schematic diagram of a method for correcting a vision system by a robot arm of the present invention.

6 is a flow chart of a method for correcting a vision system by a robot arm 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. 2. FIG. 2 is a code correction plate of the robot arm correcting device of the present invention. The code correction plate 20 is a rectangular lattice plate composed of a black lattice 21 and a white lattice 22 spaced apart from each other. In the upper left corner of each black grid 21, the direction of the direction circle 23 is coordinately coded to indicate the up, down, left and right direction of the code correction plate 20, that is, the direction of the calibration coordinate origin O of the code correction plate 20. Further, a position coordinate code in which the hollow circle 24 and the solid circle 25 are arranged in combination is provided in the white lattice 22 inside the code correction plate 20 to indicate the relative positions of the respective white lattices 22 and the code correction plate 20 for correcting the coordinate origin O. Taking the implementation as an example, the position coordinate code sets a coding circle including a hollow circle 24 and a solid circle 25 in the white lattice 22, and the coding circle is arranged in two rows, the first row on the left side represents the X axis and the second row represents the Y axis. Each row has three columns of coding circles, such as the first column A, the second column B, and the third column C, and the position is represented by the bottom to the top of the 0 to 2 power of 2, and the open circle represents the value of 0 and the solid circle represents The value is 1 to form the coordinates (X, Y) of the white lattice 22

X=A*2 ⁰ +B*2 ¹ +C*2 ²

Y=A*2 ⁰ +B*2 ¹ +C*2 ²

For example, as shown in the white grid 22 in FIG. 2, the first column A of the X-axis of the first row from the left is a hollow circle 24, the value is 0, that is, A=0, and the second column B and the third column C are solid. Circle 25, the value is 1, that is, B=1 and C=1. The first column A of the Y-axis of the second row from the left is a solid circle 25, the value is 1, that is, A=1, the second position and the third position are hollow circles 24, and the value is 0, that is, B=0 and C=0. The coordinates of the white lattice 22 are calculated as follows: X=0*2 ⁰ +1*2 ¹ +1*2 ² =6

Y=1*2 ⁰ +0*2 ¹ +0*2 ² =1 Get the coordinates (6,1). Therefore, the coordinates can be calculated according to the arrangement of the hollow circle 24 and the solid circle 25, and the relative position of the white grid 22 and the code correction plate 20 for correcting the coordinates origin O is obtained.

As shown in FIG. 3, it is a schematic diagram of the correcting device 30 of the robot arm of the present invention. The robot arm correcting device 30 of the present invention includes a vision system, a robot arm 31, a control device 32, and a code correction plate 20. Among them, the vision system includes an EIH camera 34 disposed on the robot arm 31. One end of the robot arm 31 is fixedly disposed on the base 35, has a specific arm reference coordinate M, and the movable end 33 at the other end of the robot arm 31 fixes the EIH camera 34, and the arm reference coordinate M has a coordinate before correction. Due to the movement error of the multi-joint robotic arm 31, there is a positioning error in the vision system. In order to manipulate the precise displacement of the robot arm 31, the robot arm 31 must be positioned and corrected with the EIH camera 34 of the vision system. When the correction device 30 of the present invention prepares the correction, the code correction plate 20 is fixed to the working environment of the robot arm 31 and the EIH camera 34 by the support frame 36, and has a specific correction reference coordinate N, so the correction reference on the code correction plate 20 is used. The position of the coordinate origin relative to the corrected reference coordinate N is known. The respective white grids 22 in the code correction plate 20 are encoded via position coordinates, and the position of the relative reference coordinate N is also known. Since the arm reference coordinate M of the robot arm 31 and the correction reference coordinate N of the code correction plate 20 are fixed to each other and have a relatively fixed coordinate relationship, coordinate conversion can be performed.

When the calibration device 30 of the present invention performs the correction, the control device 32 moves the robot arm 31 to drive the EIH camera 34 to approach the code correction plate 20, adjust the focal length of the EIH camera 34, and capture a clear partial image 26 of the code correction plate 20, and The focal length F obtains the distance from the white lattice 22. Then, according to the direction coordinate coding of the white grid 22 and the direction circle 23 in the partial image 26, the predetermined coordinates of the white lattice 22 relative to the corrected reference coordinate N are obtained by the position coordinate coding of the white lattice 22, and thus the focal length F and the white lattice 22 are obtained. The coordinates of the EIH camera 34 relative to the corrected reference coordinate N are obtained by the predetermined coordinates. By using the corrected reference coordinate N to convert the arm reference coordinate M coordinate, the correct coordinates of the EIH camera 34 at the arm reference coordinate M can be determined, and the EIH camera 34 The robot arm 31 movement error can be corrected by comparing the corrected front coordinates of the arm reference coordinate M.

The correcting device 30 of the robot arm of the present invention can perform the correction at any position before the robot arm moves the EIH camera 34 to the encoding correction plate 20 as described above. However, due to the assembly error of the general robot arm and its own gravity, the movement error is not uniform. Therefore, the correcting device 30 of the robot arm of the present invention can preset a plurality of different positions based on the characteristics of the robot correcting plate 20 without using too much space to move the robot arm 31, capture the image of the local encoding correcting plate, and perform correction multiple times. , averaging or adapting to uneven movement errors to achieve the purpose of improving the movement accuracy of the robot arm 31.

As shown in FIG. 4, it is a flowchart of a method for correcting a robot arm of the present invention. The detailed steps of the method of correcting the robot arm of the present invention are as follows: First, in step R1, the code correction plate is set in a predetermined range in the photographing range of the vision system of the robot arm. Go to step R2, adjust the focal length of the vision system, and capture the image of the code correction plate. In step R3, according to the captured code correction plate image, the positioning of the coordinate code in the coding correction plate is calculated, and the coordinate system positioning is performed by coordinate coding positioning and focal length. At step R4, the positioning of the vision system and the corrected front coordinates at the arm reference coordinates are compared to correct the movement error of the robot arm. Next, in step R5, it is checked whether a predetermined number of corrections is performed. If the process proceeds to step R7 to move the robot arm to another predetermined coordinate code of the code correction plate, return to step R2 to continue to correct the different positions. If sufficient correction times have been performed, Proceed to step R6 to adapt to the uneven movement error to complete the correction of the robot arm.

Therefore, the correcting device for the robot arm of the present invention can use the coding correction plate to encode the position coordinates of the combination of the hollow circle and the solid circle, and the coordinate system of the robot arm can capture the coordinate code of any position of the coding correction plate, so that The robot arm does not need to capture the active space of the entire code correction plate to achieve the purpose of improving the flexibility of the robot arm setting space. And can be done multiple times Correction, adapt to uneven movement error, to improve the movement accuracy of the robot arm.

As shown in FIG. 5, a schematic diagram of positioning the vision system of the correction device 30 of the robot arm of the present invention is shown. The robotic arm 31 vision system of the present invention can include an ETH camera 40 that is external to the robotic arm 31 and has a fixed front coordinate that is fixed relative to the arm reference coordinate M. The ETH camera 40 is used to capture an image of the external working environment of the robot arm 31 to monitor the working environment of the robot arm 31, and to guide the movable end 33 of the robot arm 31 to fix the EIH camera 34 to approach the workpiece. Next, the workpiece image is captured by the EIH camera 34, and the workpiece is positioned by the control device 32, so that the control device 32 controls the robot arm 31 according to the arm reference coordinate M, and the gripping mechanism 37 is provided by the movable end 33 to grip and assemble the workpiece. Due to the positioning error of the robot arm 31 and the vision system, in order to accurately grip and assemble the workpiece, the robot arm 31 must perform positioning correction with the EIH camera 34 and the ETH camera 40 of the vision system, respectively, without prioritization.

Correction of the robot arm 31 and the EIH camera 34 has been completed prior to the present invention, followed by correction of the robot arm 31 and the ETH camera 40. The movable end 33 of the robot arm 31 is moved away from the code correction plate 20 before correction. The code correction plate 20 is fixed to the photographing range of the ETH camera 40 by the support frame 38, and has a specific correction reference coordinate N, so that the position of the corrected reference coordinate origin on the code correction plate 20 with respect to the correction reference coordinate N is known. The position of the respective white lattice 22 in the code correction plate 20 via the position coordinate encoding is also known relative to the position of the corrected reference coordinate N. Since the arm reference coordinate M of the robot arm 31 and the correction reference coordinate N of the code correction plate 20 are fixed to each other and have a relatively fixed coordinate relationship, coordinate conversion can be performed.

When the invention is calibrated, the image of the clear code correction plate 20 is captured by the ETH camera 40. If the distance is sufficient, the ETH camera 40 can capture the complete image of the code correction plate 20 and perform the positioning of the ETH camera 40 in accordance with the prior art. If the distance is not enough, ETH camera 40 Only the partial image 26 of the code correction plate 20 can be captured, and the position of the corrected reference coordinate N is obtained by the focal length F of the focus and the position coordinate code in the partial image 26, and then converted by the arm reference coordinate M of the fixed distance to obtain ETH. The camera 40 is at the coordinates of the arm reference coordinate M to complete the positioning of the ETH camera 40, and then compared with the ETH camera 40 to correct the front coordinates to correct the error between the ETH camera 40 and the robot arm 31. The robot arm 31 has no control error with the EIH camera 34 and the ETH camera 40 to accurately guide the movement of the robot arm 31.

FIG. 6 is a flow chart of a method for correcting a vision system of a robot arm according to the present invention. The detailed steps of the method for correcting the robot arm of the present invention are as follows: First, in step S1, the preset coordinates on the code correction plate are fixed in the working environment of the robot arm, the EIH camera, and the ETH camera. Proceeding to step S2, the robot arm is moved to the code correction plate. In step S3, the coordinate code is calculated according to the code correction plate image captured by the EIH camera, and the positioning of the EIH camera is completed to correct the robot arm. At step S4, the mobile robot arm leaves the photographic range of the ETH camera. Next, in step S5, the coordinate coded position ETH camera is calculated based on the code correction plate image captured by the ETH camera to correct the robot arm. Finally, in step S6, the positioning error of the correction robot arm with the ETH camera and the EIH camera is completed.

Therefore, in the method for correcting the robot arm of the present invention, the encoder correction plate can be used to respectively position the ETH camera and the EIH camera of the robot arm to correct the movement error of the robot arm, so as to accurately control the movement of the robot arm.

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.

20‧‧‧Code Correction Board

21‧‧‧Black plaid

22‧‧‧White plaid

23‧‧‧ Directional circle

24‧‧‧ hollow circle

25‧‧‧ Solid circle

Claims (12)

A robot arm correcting device comprises: a robot arm, one end is fixedly disposed on the base and the other end is provided with a movable end; a visual system has an opposite coordinate with the robot arm, and captures a working environment image of the robot arm; a control device The image captured by the vision system is used to control the movement of the movable end of the robot arm; a code correction plate is fixed in the working environment of the robot arm, and has a fixed relative coordinate with the robot arm, and the code correction plate is a checkerboard shape, and the inside of the grid is marked. The coordinate code indicates the direction and position of the relative calibration plate; wherein the vision system focuses on the coordinate coded image of the code correction plate and positions the vision system to correct the movement error of the robot arm. The robot arm correction device according to claim 1, wherein the vision system comprises an ETH camera and an EIH camera, the ETH camera is fixed on the outside of the robot arm, and the EIH camera is fixed on the movable end of the robot arm. The apparatus for correcting a robot arm according to claim 1, wherein the grid of the code correction board is composed of a black grid and a white grid, and a direction coordinate code is indicated in each black grid to indicate relative coding correction. The direction of the board, the position coordinate code is indicated in the white grid to indicate the position of the relative code correction board. The apparatus for correcting a robot arm according to claim 3, wherein the direction coordinate is encoded in an upper left corner in the black grid, and a direction circle is indicated to indicate a direction in which the encoder calibration plate corrects the origin of the coordinates. The apparatus for correcting a robot arm according to claim 3, wherein the position coordinate code is formed by combining a circular circle and a solid circle in a white grid to represent a white grid. The sub-correction code correction plate corrects the position of the coordinate origin. The apparatus for correcting a robot arm according to claim 5, wherein the coding circle in the white grid is arranged in two rows, the first row represents the X axis and the second row represents the Y axis, and each row has the first The coding circle of column A, the second column B, and the third column C, the position is represented by the bottom to the top of the 0 to 2 power of 2, the coordinate formula of the white lattice is: X = A * 2 ⁰ + B * 2 ¹ + C*2 ² Y=A*2 ⁰ +B*2 ¹ +C*2 ² A method for correcting a robot arm, the method comprising: fixing a code correction plate to a photographing range of a vision system of a robot arm with a preset coordinate; and focusing the captured code correction plate image by using a vision system of the robot arm; Encode the calibration plate image and focal length, calculate the coding calibration plate coordinate code, locate the vision system; compare the positioning of the vision system and correct the front coordinates; correct the movement error of the robot arm. The method of correcting a robot arm according to claim 7, wherein the vision system is an ETH camera fixed to the outside of the robot arm. The method for correcting a robot arm according to claim 7, wherein the vision system is an EIH camera fixed to the robot arm. The method for correcting a robot arm according to claim 7, wherein the vision system comprises an ETH camera and an EIH camera, and the positioning correction of the ETH camera and the EIH camera are respectively performed in sequence. The method for correcting a robot arm according to claim 8, wherein the number of times the predetermined correction is corrected after the correction is insufficient, and the mobile robot arm captures different coordinate codes of the code correction plate, and continues. Correction. The method for correcting a robot arm according to claim 11, wherein the number of times the predetermined correction is performed is sufficient, the average movement error is performed, and the correction of the robot arm is completed.