Method and system for offset calibration of a robot

Abstract

The application relates to the technical field of industrial automation, and discloses a mechanical hand offset calibration method and system. The method comprises the following steps: acquiring a surface image of a target workpiece when the mechanical hand is at a first position; determining the pixel coordinates and pixel size of the center point of a set mark; determining the vertical height between the camera and the target workpiece surface based on the physical size of the set mark, the camera internal parameter and the pixel size of the set mark; determining the three-dimensional coordinates of the center point of the set mark in the camera coordinate system according to the pixel coordinates of the center point of the set mark, the vertical height and the camera internal parameter; determining the position deviation between the actual position and the target position of the mechanical hand end according to the three-dimensional coordinates of the center point of the set mark and the position conversion relationship between the camera and the mechanical hand end; and performing offset calibration on the mechanical hand according to the position deviation. The application realizes efficient, low-cost and accurate calibration of the position of the mechanical hand, has good adaptability and a wider application range.

Description

Technical Field

[0001] This invention relates to the field of industrial automation technology, and in particular to a method and system for offset calibration of a robotic arm. Background Technology

[0002] Semiconductor manufacturing is the cornerstone of the modern microelectronics industry, and one of its core components is the efficient and lossless transfer of wafers between different process chambers. High-precision robotic arms play a crucial role in this process; the positioning accuracy of their end effectors directly determines whether the wafer can be precisely placed in the designated position on the electrostatic chuck of the target process chamber. As process nodes continue to shrink, the requirements for the repeatability and accuracy of robotic arms are increasing. Any micron-level deviation can lead to wafer malfunctions, wafer breakage, or decreased process uniformity, thereby affecting product yield and production line capacity.

[0003] To maintain and ensure this high standard of positioning accuracy, periodic position calibration of the robotic arm system is an indispensable maintenance task. After prolonged continuous operation, the robotic arm will inevitably experience mechanical wear, and the drive components may also undergo minor deformation or aging. In addition, potential external interference can lead to a decrease in the robotic arm's gripping and assembly accuracy.

[0004] To calibrate the position of a robotic arm, a common practice is to rely on manual calibration, where operators use standard measuring tools to manually measure and adjust. This method is not only inefficient, but the accuracy and consistency of the calibration results also largely depend on the operator's experience level. Furthermore, the lengthy calibration process means that the equipment requires longer downtime.

[0005] Another common approach is to use non-contact measurement systems such as laser displacement sensors for calibration. While these methods typically achieve high measurement accuracy, the sensors and associated optical systems are expensive, increasing the overall manufacturing cost of the equipment. Furthermore, laser measurement systems are sensitive to environmental vibrations and cleanliness, placing higher demands on maintenance conditions.

[0006] In recent years, calibration methods based on machine vision have received increasing attention. Among them, the fixed template matching method is a common approach. However, this method has certain limitations in practical applications, as it is difficult to adapt to changes in workpiece pose, ambient lighting, and height.

[0007] In summary, existing robotic arm position calibration technologies suffer from low efficiency, high cost, and poor adaptability. Summary of the Invention

[0008] To address the problems of low efficiency, high cost, and poor adaptability in existing robotic arm position calibration technologies, this invention provides a method and system for calibrating the offset of a robotic arm.

[0009] To achieve the above objectives, a first aspect of the present invention provides a method for offset calibration of a robotic arm, the method comprising:

[0010] A camera mounted on the end effector of the robotic arm acquires a surface image of the target workpiece at a first position. The target workpiece includes a set mark, and the surface image includes at least a portion of the set mark. The first position is the position reached by the robotic arm after executing the instruction to move directly above the target workpiece.

[0011] Determine the pixel coordinates of the center point of the set mark in the surface image and the pixel size of the set mark in the surface image;

[0012] Based on the physical dimensions of the set mark, the intrinsic parameters of the camera, and the pixel size of the set mark in the surface image, the vertical height of the camera relative to the surface of the target workpiece is determined;

[0013] Based on the pixel coordinates of the center point of the set mark in the surface image, the vertical height, and the intrinsic parameters of the camera, determine the three-dimensional coordinates of the center point of the set mark in the camera coordinate system;

[0014] Based on the three-dimensional coordinates of the center point of the set mark in the camera coordinate system and the position transformation relationship between the camera and the robotic arm end effector, the positional deviation between the actual position and the target position of the robotic arm end effector is determined.

[0015] The robot arm is offset calibrated based on the positional deviation.

[0016] In one possible implementation of the first aspect, the offset calibration of the robot arm based on the position deviation includes:

[0017] The motion compensation data of the robot is determined based on the position deviation, and the robot is driven to move to a second position based on the motion compensation data to achieve offset calibration of the robot, wherein the second position is closer to the target position than the first position.

[0018] In one possible implementation of the first aspect, determining the pixel coordinates of the center point of the set marker in the surface image and the pixel size of the set marker in the surface image includes:

[0019] The surface image is subjected to noise reduction filtering.

[0020] Edge detection is performed on the filtered surface image to extract the contour of the set marker;

[0021] The pixel coordinates of the center point of the designated mark in the surface image and the pixel size of the designated mark in the surface image are determined based on the outline of the designated mark.

[0022] In one possible implementation of the first aspect, the vertical height of the camera relative to the surface of the target workpiece is determined by the following formula, based on the physical size of the set mark, the intrinsic parameters of the camera, and the pixel size of the set mark in the surface image:

[0023] h = (d1 * k) / d2

[0024] Where h is the vertical height between the camera and the surface of the target workpiece, d1 is the physical size of the set mark, d2 is the pixel size of the set mark in the surface image, and k is the conversion coefficient obtained by calibration based on the camera intrinsic parameters.

[0025] In one possible implementation of the first aspect, the intrinsic parameters of the camera include the physical size of the pixels corresponding to the camera and the focal length of the camera. Determining the three-dimensional coordinates of the center point of the set marker in the camera coordinate system based on the pixel coordinates of the center point of the set marker in the surface image, the vertical height, and the intrinsic parameters of the camera includes:

[0026] Obtain the pixel coordinates of the center point of the surface image;

[0027] Calculate the pixel offset of the center point of the set mark in the surface image relative to the pixel coordinates of the center point of the surface image;

[0028] The physical offset of the center point of the set mark on the camera sensor plane of the camera is determined based on the pixel offset and the physical size of the pixel;

[0029] Based on the physical offset, the vertical height, and the focal length of the camera, the three-dimensional coordinates of the center point of the designated mark in the camera coordinate system are determined.

[0030] In one possible implementation of the first aspect, driving the robotic arm to move to the second position based on the motion compensation data includes:

[0031] Calculate the concentricity between the target workpiece and the mask plate set at the end of the robot arm;

[0032] Determine whether the concentricity is greater than a preset concentricity threshold;

[0033] If the concentricity is greater than a preset concentricity threshold, the robotic arm is driven to move from the actual position to the second position based on the motion compensation data.

[0034] In one possible implementation of the first aspect, the concentricity of the target workpiece and the mask disposed at the end of the robot arm is calculated in the following manner:

[0035] Calculate the three-dimensional coordinates of the center point of the set mark in the target workpiece in the camera coordinate system and the planar distance between the center point of the mask;

[0036] The planar distance is used as the concentricity.

[0037] In one possible implementation of the first aspect, after driving the robotic arm to perform motion compensation, the method further includes:

[0038] Acquire a surface image of the target workpiece when the robot arm is in the second position, and calculate the positional deviation between the actual position of the robot arm's end effector and the target position when the robot arm is in the second position;

[0039] Determine whether the positional deviation is less than a preset deviation accuracy threshold;

[0040] If the positional deviation is less than the preset deviation accuracy threshold, the offset calibration of the robot arm is determined to be complete.

[0041] In one possible implementation of the first aspect, the method further includes:

[0042] Store a set number of the surface images.

[0043] Secondly, this application provides a displacement calibration system for a robotic arm, comprising:

[0044] The system includes a robotic arm, a photomask, a camera, an illumination assembly, and a control unit. The photomask is located at the end of the robotic arm, the camera is located at the standard center of the photomask, the illumination assembly is arranged around the camera, and the control unit is communicatively connected to the robotic arm and the camera.

[0045] The camera is used to acquire a surface image of a target workpiece, the target workpiece including a set mark, and the surface image including at least a portion of the set mark;

[0046] The lighting component is used to provide illumination for the camera to capture images of the target component;

[0047] The control unit is configured to:

[0048] The camera is controlled to acquire a surface image of the target workpiece when the robot arm is in a first position, where the first position is the position reached by the robot arm after executing the instruction to move directly above the target workpiece;

[0049] Determine the pixel coordinates of the center point of the set mark in the surface image and the pixel size of the set mark in the surface image;

[0050] Based on the physical dimensions of the set mark, the intrinsic parameters of the camera, and the pixel size of the set mark in the surface image, the vertical height of the camera relative to the surface of the target workpiece is determined;

[0051] Based on the pixel coordinates of the center point of the set mark in the surface image, the vertical height, and the intrinsic parameters of the camera, determine the three-dimensional coordinates of the center point of the set mark in the camera coordinate system;

[0052] Based on the three-dimensional coordinates of the center point of the set mark in the camera coordinate system and the position transformation relationship between the camera and the robotic arm end effector, the positional deviation between the actual position and the target position of the robotic arm end effector is determined.

[0053] The robot arm is offset calibrated based on the positional deviation.

[0054] In one possible implementation of the second aspect, the control unit is configured to perform offset calibration on the robot arm based on the position deviation in the following manner:

[0055] The motion compensation data of the robot is determined based on the position deviation, and the robot is driven to move to a second position based on the motion compensation data to achieve offset calibration of the robot, wherein the second position is closer to the target position than the first position.

[0056] In one possible implementation of the second aspect, the target workpiece includes an electrostatic chuck in a semiconductor process apparatus, and the setting mark includes a central circular hole in the electrostatic chuck.

[0057] By adopting the above technical solution, the present invention has the following beneficial effects:

[0058] The technical solution of this invention acquires a surface image of the target workpiece when the robot is in its first position using a camera mounted on the end effector of a robot arm. This provides the data basis for robot arm offset calibration, avoiding the need for a high-cost laser measurement system and thus reducing hardware costs at the system level. Because the camera is mounted on the end effector, it can capture images promptly as the robot moves to the first position, reducing calibration time. By determining the pixel coordinates of the center point of the set marker in the surface image and the pixel size of the set marker in the surface image, key parameters are automatically extracted. Compared to traditional manual calibration methods that rely on visual observation and manual measurement, this automates a tedious and error-prone task, improving the efficiency and consistency of the calibration process and reducing reliance on operator experience. Based on the physical dimensions of the set marker, the camera's intrinsic parameters, and the pixel dimensions of the set marker in the surface image, the vertical height between the camera and the target workpiece surface is determined. This allows for dynamic and real-time calculation of the actual height for each shot, rather than relying on a fixed preset value. This adaptability mitigates the effects of mechanical tolerances, repeatability errors in the robot's stop position, or variations in workpiece installation height, significantly improving the system's adaptability and robustness under different working conditions and broadening its applicability. After obtaining the height information, the three-dimensional coordinates of the set marker's center point in the camera coordinate system are determined based on the pixel coordinates of the center point in the surface image, the vertical height, and the camera's intrinsic parameters. This achieves a precise conversion from two-dimensional image information to three-dimensional spatial coordinates, providing accurate quantitative input for subsequent deviation calculations and laying the foundation for high-precision calibration. Based on the three-dimensional coordinates of the set marker's center point in the camera coordinate system and the positional transformation relationship between the camera and the robot's end effector, the positional deviation between the actual position and the target position of the robot's end effector is determined. This avoids the subjectivity and inaccuracy of manual judgment. The robot is then offset calibrated based on this positional deviation, thereby improving the accuracy and reliability of the calibration.

[0059] In summary, the technical solution of this invention achieves efficient, low-cost, and accurate calibration of the position of the robotic arm, with good adaptability and a wider range of applications. Attached Figure Description

[0060] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0061] Figure 1 According to some embodiments of the present invention, a structural block diagram of an offset calibration system for a robotic arm is shown;

[0062] Figure 2 According to some embodiments of the present invention, a flowchart of an offset calibration method for a robotic arm is shown;

[0063] Figure 3 The diagram illustrates the center point of the marker in the surface image and the center point of the surface image itself. Detailed Implementation

[0064] The illustrative embodiments of the present invention include, but are not limited to, a method and system for offset calibration of a robotic arm.

[0065] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0066] As mentioned earlier, existing robotic arm position calibration technologies suffer from low efficiency, high cost, and poor adaptability.

[0067] In view of this, the present invention provides a method and system for offset calibration of a robotic arm.

[0068] Figure 1 According to some embodiments of this application, a structural block diagram of an offset calibration system 10 for a robotic arm 12 is shown, with reference to... Figure 1 The present invention provides an offset calibration system 10 for a robotic arm 12, comprising: a robotic arm 12, a mask 11, a camera 13, an illumination assembly 14, and a control unit 15. The mask 11 is disposed at the end of the robotic arm 12, the camera 13 is disposed at the standard center of the mask 11, the illumination assembly 14 is arranged around the camera 13, and the control unit 15 is communicatively connected to the robotic arm 12 and the camera 13.

[0069] Camera 13 is used to acquire a surface image of a target workpiece, the target workpiece including designated marks, and the surface image including at least a portion of the designated marks. Illumination assembly 14 is used to provide illumination for the camera 13 to capture the target workpiece, thereby making the acquired surface image clearer. Here, the surface image refers to an image obtained by capturing the upper surface of the target workpiece.

[0070] It should be noted that since the camera 13 is set at the standard center of the mask 11, the optical center of the camera 13 coincides with the origin of the coordinate system of the mask 11.

[0071] The control unit 15 is configured to: control the camera 13 to acquire a surface image of the target workpiece when the robot arm 12 is in a first position, the first position being the position reached by the robot arm 12 after executing the command to move directly above the target workpiece; determine the pixel coordinates of the center point of the set mark in the surface image and the pixel size of the set mark in the surface image; determine the vertical height of the camera 13 relative to the surface of the target workpiece based on the physical size of the set mark, the intrinsic parameters of the camera 13, and the pixel size of the set mark in the surface image; determine the three-dimensional coordinates of the center point of the set mark in the coordinate system of the camera 13 according to the pixel coordinates of the center point of the set mark in the surface image, the vertical height, and the intrinsic parameters of the camera 13; determine the positional deviation between the actual position and the target position of the end of the robot arm 12 according to the three-dimensional coordinates of the center point of the set mark in the coordinate system of the camera 13 and the position transformation relationship between the camera 13 and the end of the robot arm 12; and perform offset calibration on the robot arm 12 based on the positional deviation.

[0072] In some embodiments, the control unit 15 is configured to perform offset calibration on the robot arm 12 based on the aforementioned position deviation by determining motion compensation data of the robot arm 12 based on the aforementioned position deviation, and driving the robot arm 12 to move to a second position based on the motion compensation data, thereby achieving offset calibration of the robot arm 12, wherein the second position is closer to the target position than the first position.

[0073] In some embodiments, the target workpiece includes an electrostatic chuck in a semiconductor process apparatus, and the setting mark includes the central circular hole of the electrostatic chuck.

[0074] In other embodiments, the target workpiece may also include other chucks, such as mechanical chucks or vacuum chucks.

[0075] Understandable, Figure 1 The structural block diagram shown does not constitute a specific limitation on the offset calibration system 10 of the robotic arm 12. In other embodiments of the present invention, the offset calibration system 10 of the robotic arm 12 may include a... Figure 1 This may involve more or fewer components, or combining certain components, or splitting certain components, or different component arrangements.

[0076] For example, in some embodiments, the offset calibration system 10 of the robot arm 12 provided by the present invention can also be equipped with a light sensor to detect the light intensity of the lighting component 14, and eliminate shadow interference through adaptive histogram equalization, so that the surface image of the target workpiece acquired by the camera 13 is clearer.

[0077] Figure 2 According to some embodiments of this application, an offset calibration method for a robotic arm 12 is shown, with reference to... Figure 2The offset calibration method for a robotic arm 12 provided in this application includes the following steps:

[0078] Step S11: Obtain a surface image of the target workpiece when the robot arm 12 is in the first position by using a camera 13 set at the end of the robot arm 12. The target workpiece includes a set mark, and the surface image includes at least a portion of the set mark. The first position is the position reached by the robot arm 12 after executing the instruction to move directly above the target workpiece.

[0079] It should be understood that after the robot arm 12 executes the command to move directly above the target workpiece, its first position should be directly above the target workpiece. However, due to long-term operation or external interference, the first position reached by the robot arm 12 after executing the command to move directly above the target workpiece has shifted, resulting in the first position not being directly above the target workpiece and not aligned with the markings on the target workpiece. Assuming the target workpiece is an electrostatic chuck, then the first position is not aligned with the central hole of the electrostatic chuck.

[0080] Step S12: Determine the pixel coordinates of the center point of the setting mark in the surface image and the pixel size of the setting mark in the surface image.

[0081] In some embodiments, determining the pixel coordinates of the center point of the set mark in the surface image and the pixel size of the set mark in the surface image includes: performing noise reduction filtering on the surface image, performing edge detection on the filtered surface image, extracting the contour of the set mark, and determining the pixel coordinates of the center point of the set mark in the surface image and the pixel size of the set mark in the surface image based on the contour of the set mark.

[0082] Taking an electrostatic chuck as the target workpiece as an example, in some embodiments, a Gaussian filtering algorithm is used to perform noise reduction filtering on the surface image of the electrostatic chuck, thereby avoiding environmental noise interference with subsequent edge detection. The contour edge of the central circular hole of the electrostatic chuck is extracted using the Canny operator, and then the pixel diameter d2 of the circular hole and the pixel coordinates (u, v) of the center of the circular hole are calculated using a least-squares circle fitting algorithm.

[0083] Step S13: Based on the physical dimensions of the set mark, the intrinsic parameters of the camera 13, and the pixel dimensions of the set mark in the surface image, determine the vertical height of the camera 13 relative to the surface of the target workpiece.

[0084] In some embodiments, the vertical height of the camera 13 relative to the surface of the target workpiece is determined using the following formula, based on the physical size of the set mark, the intrinsic parameters of the camera 13, and the pixel size of the set mark in the surface image:

[0085] h = (d1 * k) / d2 Formula (1)

[0086] Where h is the vertical height between the camera 13 and the surface of the target workpiece, d1 is the physical size of the set mark, d2 is the pixel size of the set mark in the surface image, and k is the conversion coefficient obtained by calibration based on the intrinsic parameters of the camera 13.

[0087] Among them, the intrinsic parameters of camera 13 include the focal length of camera 13.

[0088] Assuming the target workpiece is an electrostatic chuck, and the center hole of the electrostatic chuck is designated as the center hole, since the physical size (d1) of the center hole is known, based on the similar triangle principle of pinhole imaging: the ratio of the actual size (d1) of the center hole to the previously calculated pixel diameter d2 is equal to the ratio of the distance (h) from camera 13 to the electrostatic chuck to the focal length (f) of camera 13. Therefore, the derivation process for calculating the vertical height h between camera 13 and the surface of the electrostatic chuck is as follows:

[0089] Assuming the projected diameter of the central circular hole on the sensor of camera 13 is d3 (in mm), according to the definition of pixel size: d3 = d2 × s, where s is the physical size of a pixel (in mm / pixel). The pinhole imaging similarity ratio is: d1 / d3 = h / f. Eliminating d3 and substituting s = sensor size / resolution (camera 13 calibration parameter), we finally simplify to: h = (d1 × f × resolution) / (d2 × sensor size).

[0090] In practical applications, by calibrating the intrinsic parameters of camera 13, (f×resolution) / sensor size is pre-calculated as the "pixel-distance conversion coefficient" k, then we get: h=(d1×k) / d2.

[0091] In a specific embodiment, it is assumed that d1 = 10 mm and k = 800 pixels·mm are known. - ¹, if d2 = 200 pixels, then h = (10 × 800) / 200 = 40 mm.

[0092] Step S14: Determine the three-dimensional coordinates of the center point of the set mark in the coordinate system of the camera 13 based on the pixel coordinates and vertical height of the center point of the set mark in the surface image and the intrinsic parameters of the camera 13.

[0093] In some embodiments, the intrinsic parameters of the camera 13 include the physical size of the pixel corresponding to the camera 13 and the focal length of the camera 13. Determining the three-dimensional coordinates of the center point of the set mark in the camera 13 coordinate system based on the pixel coordinates, vertical height, and intrinsic parameters of the set mark in the surface image, includes: obtaining the pixel coordinates of the center point of the surface image; calculating the pixel offset of the pixel coordinates of the center point of the set mark in the surface image relative to the pixel coordinates of the center point of the surface image; determining the physical offset of the center point of the set mark on the camera sensor plane of the camera 13 based on the pixel offset and the physical size of the pixel; and determining the three-dimensional coordinates of the center point of the set mark in the camera 13 coordinate system based on the physical offset, vertical height, and focal length of the camera 13.

[0094] Figure 3 The diagram illustrates the center point of the marker in the surface image and the center point of the surface image itself. The center point of the surface image is the projection point of the standard center of mask 11 onto the surface image. Assuming the pixel coordinates of the center point of the surface image are (u0, v0) and the pixel coordinates of the center point of the marker in the surface image are (u, v), then the lateral offset Δu = uu of the pixel coordinates of the center point of the marker in the surface image relative to the pixel coordinates of the center point of the surface image is... 0， The vertical offset Δv = v - v0. Then, based on the pixel's horizontal offset Δu, vertical offset Δv, and pixel's physical size s, the physical offset of the center point of the setting mark on the camera sensor plane of camera 13 is determined as Δx = Δu × s, Δy = Δv × s. Based on these physical offsets Δx and Δy, the previously calculated vertical height h, and the focal length f of camera 13, combined with the pinhole imaging similarity ratio, the three-dimensional coordinates of the center point of the setting mark in the camera 13 coordinate system are calculated as follows: X = Δx × h / f + 0; Y = -Δy × h / f + 0; Z = -h + 0. It should be understood that, assuming the Z-coordinate of the mask center is 0 and the Z-coordinate of the optical center of camera 13 is 0, then the Z-coordinate of the electrostatic chuck surface is -h + 0.

[0095] In a specific embodiment, given that the standard center pixel coordinates of the mask 11 are u=640 pixels, the center pixel coordinates of the circular hole are u=640 pixels, s=0.01mm / pixel, h=40mm, f=8mm, o=0mm, then: Δu=10 pixels, Δx=10×0.01=0.1mm, X=0.1×40 / 8+0=0.5mm; similarly, Y=-0.3mm, and the final actual coordinates of the center of the circular hole are (0.5,-0.3,-40)mm.

[0096] Step S15: Based on the three-dimensional coordinates of the center point of the set mark in the coordinate system of the camera 13 and the position transformation relationship between the camera 13 and the end of the robot 12, determine the position deviation between the actual position and the target position of the end of the robot 12.

[0097] The specific derivation process is as follows: Through the preceding steps, the three-dimensional coordinates of the center point of the set mark in the coordinate system of camera 13 have been obtained. The origin of the coordinate system of camera 13 is the center of the lens of camera 13. Through prior calibration, the position transformation relationship between camera 13 and the end effector of robot 12 is known. This transformation relationship describes how to convert the coordinates of a point in the coordinate system of camera 13 to the coordinate system of the end effector of robot 12. Using this known transformation relationship, the three-dimensional coordinates of the center point of the set mark in the coordinate system of camera 13 can be transformed from the coordinate system of camera 13 to the coordinate system of the end effector of robot 12, thereby obtaining the vector P pointing from the origin of the end effector of robot 12 to the center point of the set mark on the target workpiece in the coordinate system of the end effector of robot 12. tool Since camera 13 is positioned at the end effector of robot arm 12, the relative position between camera 13 and the end effector of robot arm 12 is fixed. Therefore, the position of the setting mark relative to camera 13 is geometrically equivalent to the position of the setting mark relative to the end effector of robot arm 12, only the coordinate systems used to express them are different. Furthermore, it can be considered that the offset of the actual position of the end effector of robot arm 12 relative to the setting mark point is the opposite vector of the vector pointing from the origin of the end effector of robot arm 12 to the center point of the setting mark on the target workpiece in the coordinate system of the end effector of robot arm 12. Also, since the target position of the end effector of robot arm 12 is a theoretically known coordinate value, this target position is the ideal position that robot arm 12 should reach, aligned with the center of the setting mark. Therefore, the actual position of the end effector of robot arm 12 can be calculated: Actual position = Target position - P tool Ultimately, the position deviation = actual position - target position.

[0098] Step S16: Perform offset calibration on the robot arm 12 based on the position deviation.

[0099] In some embodiments, offset calibration of the robot arm 12 based on the position deviation includes: determining motion compensation data of the robot arm 12 based on the position deviation, and driving the robot arm 12 to move to a second position based on the motion compensation data to achieve offset calibration of the robot arm 12, wherein the second position is closer to the target position than the first position.

[0100] It should be understood that after the robot arm 12 in the first position is calibrated, the robot arm 12 will be closer to the target position, so the second position is closer to the target position than the first position.

[0101] In some embodiments, driving the robot arm 12 to move to the second position based on motion compensation data includes: calculating the concentricity of the target workpiece and the mask plate 11 disposed at the end of the robot arm 12, determining whether the concentricity is greater than a preset concentricity threshold, and driving the robot arm 12 to move from the actual position to the second position based on motion compensation data if the concentricity is greater than the preset concentricity threshold.

[0102] If the concentricity is greater than the preset concentricity threshold, the robot arm 12 is driven to move from the actual position to the second position based on motion compensation data to achieve position calibration of the robot arm 12 until the concentricity is less than or equal to the preset concentricity threshold, indicating that no further calibration is needed.

[0103] In some embodiments, the concentricity of the target workpiece and the mask 11 set at the end of the robot arm 12 is calculated by: calculating the three-dimensional coordinates of the center point of the set mark in the target workpiece in the coordinate system of the camera 13 and the planar distance between the center point of the mask 11, and using the planar distance as the concentricity.

[0104] In some embodiments, assuming the standard center coordinates of the mask 11 are (0,0,0) and the center point coordinates of the target workpiece setting mark are (x,y,0), the formula for calculating the concentricity of the target workpiece and the mask 11 set at the end of the robot arm 12 is as follows:

[0105] Formula (2)

[0106] In some embodiments, after driving the robot arm 12 to perform motion compensation, the above method further includes: acquiring a surface image of the target workpiece when the robot arm 12 is in the second position, and calculating the positional deviation between the actual position of the end of the robot arm 12 and the target position when the robot arm 12 is in the second position; determining whether the positional deviation is less than a preset deviation accuracy threshold; and determining that the offset calibration of the robot arm 12 is completed if the positional deviation is less than the preset deviation accuracy threshold.

[0107] Therefore, after completing the first calibration, a second verification is performed. If the position deviation is greater than or equal to the preset deviation accuracy threshold, it indicates that the calibration is not up to standard and the calibration process of the offset calibration method of the robot arm 12 provided in this application needs to be repeated until the accuracy requirements are met.

[0108] In some embodiments, the method described above further includes storing a predetermined number of historical surface images. This facilitates analysis based on the stored predetermined number of historical surface images.

[0109] It is understood that the execution order of steps S11 to S16 above is only an illustration. In other embodiments, other execution orders may be used, and some steps may be split or combined. This is not limited here.

[0110] This invention provides a data foundation for robot offset calibration by acquiring a surface image of the target workpiece when the robot is in its first position using a camera mounted on the end effector of a robot. This avoids the need for a high-cost laser measurement system, thereby reducing hardware costs at the system level. Since the camera is located at the end effector, it can capture images promptly as the robot moves to the first position, reducing calibration time. By determining the pixel coordinates of the center point of the set marker and its pixel size in the surface image, key parameters are automatically extracted. Compared to traditional manual calibration methods that rely on visual observation and manual measurement, this automates a tedious and error-prone task, improving the efficiency and consistency of the calibration process and reducing reliance on operator experience. Based on the physical dimensions of the set marker, the camera's intrinsic parameters, and the pixel dimensions of the set marker in the surface image, the vertical height between the camera and the target workpiece surface is determined. This allows for dynamic and real-time calculation of the actual height for each shot, rather than relying on a fixed preset value. This adaptability mitigates the effects of mechanical tolerances, repeatability errors in the robot's stop position, or variations in workpiece installation height, significantly improving the system's adaptability and robustness under different working conditions and broadening its applicability. After obtaining the height information, the three-dimensional coordinates of the set marker's center point in the camera coordinate system are determined based on the pixel coordinates of the center point in the surface image, the vertical height, and the camera's intrinsic parameters. This achieves a precise conversion from two-dimensional image information to three-dimensional spatial coordinates, providing accurate quantitative input for subsequent deviation calculations and laying the foundation for high-precision calibration. Finally, based on the three-dimensional coordinates of the set marker's center point in the camera coordinate system and the positional transformation relationship between the camera and the robot's end effector, the positional deviation between the actual position of the robot's end effector and the target position is determined. This avoids the subjectivity and inaccuracy of manual judgment, thereby improving the accuracy and reliability of calibration. The motion compensation data of the robot is determined based on the position deviation, and the robot is driven to move to the second position based on the motion compensation data, thus completing the closed-loop control from perception to execution and realizing full-process automation.

[0111] This invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps described in the various method embodiments above.

[0112] This invention provides a computer program product that, when run on a mobile terminal, enables the mobile terminal to implement the steps described in the above-described method embodiments.

[0113] This invention also provides an electronic device comprising: at least one processor, a memory, and a computer program stored in the memory and executable on the at least one processor, wherein the processor executes the computer program to implement the steps in any of the above method embodiments.

[0114] In some cases, the disclosed embodiments may be implemented in hardware, firmware, software, or any combination thereof. The disclosed embodiments may also be implemented as instructions carried or stored thereon on one or more temporary or non-temporary machine-readable (e.g., computer-readable) storage media, which may be read and executed by one or more processors. For example, the instructions may be distributed via a network or through other computer-readable media. Therefore, machine-readable media may include any mechanism for storing or transmitting information in a machine-readable (e.g., computer-readable) form, including but not limited to floppy disks, optical disks, CD-ROMs, magneto-optical disks, read-only memory (ROM), random access memory (RAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic cards or optical cards, flash memory, or tangible machine-readable storage for transmitting information (e.g., carrier waves, infrared signals, digital signals, etc.) using the Internet in the form of electrical, optical, acoustic, or other forms of propagated signals. Therefore, machine-readable media include any type of machine-readable medium suitable for storing or transmitting electronic instructions or information in a machine-readable (e.g., computer-readable) form.

[0115] In the accompanying drawings, some structural or methodological features may be shown in a specific arrangement and / or order. However, it should be understood that such a specific arrangement and / or order may not be necessary. Rather, in some embodiments, these features may be arranged in a manner and / or order different from that shown in the illustrative drawings. Furthermore, the inclusion of structural or methodological features in a particular figure does not imply that such features are required in all embodiments, and in some embodiments, these features may be omitted or may be combined with other features.

[0116] It should be noted that the units / modules mentioned in the various device embodiments of the present invention are all logical units / modules. Physically, a logical unit / module can be a physical unit / module, a part of a physical unit / module, or a combination of multiple physical units / modules. The physical implementation of these logical units / modules themselves is not the most important factor; the combination of functions implemented by these logical units / modules is the key to solving the technical problem proposed by the present invention. Furthermore, to highlight the innovative aspects of the present invention, the above-described device embodiments of the present invention have not introduced units / modules that are not closely related to solving the technical problem proposed by the present invention. This does not mean that the above-described device embodiments do not contain other units / modules.

[0117] It should be noted that in the examples and description of this patent, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0118] Although the invention has been illustrated and described with reference to certain preferred embodiments thereof, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims

1. A method for offset calibration of a robotic arm, characterized in that, The robotic arm has a mask at its end, and a camera is positioned at the standard center of the mask. The method includes: The camera acquires a surface image of the target workpiece when the robot arm is in a first position. The target workpiece includes a set mark, and the surface image includes at least a portion of the set mark. The first position is the position reached by the robot arm after executing the instruction to move directly above the target workpiece. Determine the pixel coordinates of the center point of the set mark in the surface image and the pixel size of the set mark in the surface image; Based on the physical dimensions of the set mark, the intrinsic parameters of the camera, and the pixel size of the set mark in the surface image, the vertical height of the camera relative to the surface of the target workpiece is determined; Based on the pixel coordinates of the center point of the set mark in the surface image, the vertical height, and the intrinsic parameters of the camera, determine the three-dimensional coordinates of the center point of the set mark in the camera coordinate system; Based on the three-dimensional coordinates of the center point of the set mark in the camera coordinate system and the position transformation relationship between the camera and the robotic arm end effector, the positional deviation between the actual position and the target position of the robotic arm end effector is determined. The robot arm is offset calibrated based on the positional deviation.

2. The calibration method according to claim 1, characterized in that, The offset calibration of the robot arm based on the position deviation includes: The motion compensation data of the robot is determined based on the position deviation, and the robot is driven to move to a second position based on the motion compensation data to achieve offset calibration of the robot, wherein the second position is closer to the target position than the first position.

3. The offset calibration method for a robotic arm according to claim 2, characterized in that, Determining the pixel coordinates of the center point of the set marker in the surface image and the pixel size of the set marker in the surface image includes: The surface image is subjected to noise reduction filtering. Edge detection is performed on the filtered surface image to extract the contour of the set marker; The pixel coordinates of the center point of the designated mark in the surface image and the pixel size of the designated mark in the surface image are determined based on the outline of the designated mark.

4. The offset calibration method for a robotic arm according to claim 3, characterized in that, The vertical height of the camera relative to the target workpiece surface is determined using the following formula, based on the physical size of the set mark, the intrinsic parameters of the camera, and the pixel size of the set mark in the surface image: h = (d1 k) / d2 Where h is the vertical height between the camera and the surface of the target workpiece, d1 is the physical size of the set mark, d2 is the pixel size of the set mark in the surface image, and k is the conversion coefficient obtained by calibration based on the camera intrinsic parameters.

5. The offset calibration method for a robotic arm according to claim 4, characterized in that, The intrinsic parameters of the camera include the physical size of the corresponding pixels and the focal length of the camera. Determining the three-dimensional coordinates of the center point of the set marker in the camera coordinate system based on the pixel coordinates of the center point of the set marker in the surface image, the vertical height, and the intrinsic parameters of the camera includes: Obtain the pixel coordinates of the center point of the surface image; Calculate the pixel offset of the center point of the set mark in the surface image relative to the pixel coordinates of the center point of the surface image; The physical offset of the center point of the set mark on the camera sensor plane of the camera is determined based on the pixel offset and the physical size of the pixel; Based on the physical offset, the vertical height, and the focal length of the camera, the three-dimensional coordinates of the center point of the designated mark in the camera coordinate system are determined.

6. The offset calibration method for a robotic arm according to claim 5, characterized in that, The step of driving the robotic arm to move to the second position based on the motion compensation data includes: Calculate the concentricity between the target workpiece and the mask plate set at the end of the robot arm; Determine whether the concentricity is greater than a preset concentricity threshold; If the concentricity is greater than a preset concentricity threshold, the robotic arm is driven to move from the actual position to the second position based on the motion compensation data.

7. The offset calibration method for a robotic arm according to claim 6, characterized in that, The concentricity of the target workpiece and the mask set at the end of the robot arm is calculated in the following way: Calculate the three-dimensional coordinates of the center point of the set mark in the target workpiece in the camera coordinate system and the planar distance between the center point of the mask; The planar distance is used as the concentricity.

8. The offset calibration method for a robotic arm according to claim 7, characterized in that, After driving the robotic arm to perform motion compensation, the method further includes: Acquire a surface image of the target workpiece when the robot arm is in the second position, and calculate the positional deviation between the actual position of the robot arm's end effector and the target position when the robot arm is in the second position; Determine whether the positional deviation is less than a preset deviation accuracy threshold; If the positional deviation is less than the preset deviation accuracy threshold, the offset calibration of the robot arm is determined to be complete.

9. The offset calibration method for a robotic arm according to any one of claims 1 to 8, characterized in that, The method further includes: Store a set number of the surface images.

10. An offset calibration system for a robotic arm, characterized in that, include: The system includes a robotic arm, a photomask, a camera, an illumination assembly, and a control unit. The photomask is located at the end of the robotic arm, the camera is located at the standard center of the photomask, the illumination assembly is arranged around the camera, and the control unit is communicatively connected to the robotic arm and the camera. The camera is used to acquire a surface image of a target workpiece, the target workpiece including a set mark, and the surface image including at least a portion of the set mark; The lighting component is used to provide illumination for the camera to capture images of the target component; The control unit is configured to: The camera is controlled to acquire a surface image of the target workpiece when the robot arm is in a first position, where the first position is the position reached by the robot arm after executing the instruction to move directly above the target workpiece; Determine the pixel coordinates of the center point of the set mark in the surface image and the pixel size of the set mark in the surface image; Based on the physical dimensions of the set mark, the intrinsic parameters of the camera, and the pixel size of the set mark in the surface image, the vertical height of the camera relative to the surface of the target workpiece is determined; Based on the pixel coordinates of the center point of the set mark in the surface image, the vertical height, and the intrinsic parameters of the camera, determine the three-dimensional coordinates of the center point of the set mark in the camera coordinate system; Based on the three-dimensional coordinates of the center point of the set mark in the camera coordinate system and the position transformation relationship between the camera and the robotic arm end effector, the positional deviation between the actual position and the target position of the robotic arm end effector is determined. The robot arm is offset calibrated based on the positional deviation.

11. The offset calibration system for a robotic arm according to claim 10, characterized in that, The control unit is configured to perform offset calibration on the robot arm based on the positional deviation in the following manner: The motion compensation data of the robot is determined based on the position deviation, and the robot is driven to move to a second position based on the motion compensation data to achieve offset calibration of the robot, wherein the second position is closer to the target position than the first position.

12. The offset calibration system for a robotic arm according to claim 10, characterized in that, The target workpiece includes an electrostatic chuck in a semiconductor process equipment, and the setting mark includes the central circular hole of the electrostatic chuck.

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