Single vision tcp calibration method and device for industrial robot

Abstract

The application provides a monocular vision TCP calibration method and device for an industrial robot, and the method comprises the following steps: determining a tool coordinate system to be calibrated and a TCP calibration instrument coordinate system C dev ; moving the robot so that the tool end is located at a calibration area of the TCP calibration instrument; measuring X and Y coordinate deviations of a tool-flange transformation matrix; calibrating X and Y coordinates of the tool-flange transformation matrix; measuring Z coordinate deviations of the tool-flange transformation matrix; calibrating Z coordinates of the tool-flange transformation matrix; checking TCP precision to determine whether the precision requirement is met; and completing TCP calibration. The monocular vision TCP calibration method is simple in principle, convenient to operate, low in hardware cost, high in calibration precision, and fast in calibration speed.

Description

Technical Field

[0001] This invention relates to the field of industrial robot technology, and in particular to a monocular vision TCP calibration method and device for industrial robots. Background Technology

[0002] With the rapid development of industrial robot technology, industrial robots are increasingly used in high-precision production operations. Industrial robots are often seen as carriers of specialized tools and equipment, used in operations such as welding, cutting, dispensing, grinding, milling, and material handling. In these operations, the robot operates according to a pre-programmed sequence, which defines the position coordinates of the tool's work points to establish the tool coordinate system. The position of the tool's work point relative to the flange coordinate system is usually called the tool center point, or TCP. The robot's path accuracy actually refers to the path accuracy of the TCP. When the robot's TCP coincides with the actual tool work point, the tool can operate along the planned path. When the robot's TCP deviates from the actual tool work point, the actual work point of the tool will deviate from the predetermined path, and the robot's path accuracy will deteriorate.

[0003] In actual production operations, robot position and orientation deviations are inevitable. First, due to errors in tool manufacturing and installation, using the nominal tool's work point as the TCP will inevitably result in inaccuracies. Second, in certain operations, such as wear and tear on the welding torch and wire in welding, bumps and deformation of the dispensing needle in dispensing, and normal tool replacement and disassembly, the TCP will inevitably shift. If the TCP is not calibrated in time or the motion program is not updated and the original TCP data is continued, the robot's work path accuracy will deteriorate, making it unable to meet high-precision requirements. Finally, the current robotics industry widely uses point-to-point teaching methods such as the four-point and six-point methods to calibrate the TCP. These methods are time-consuming and labor-intensive, unsuitable for high-cycle, automated operations. During TCP calibration, the coupled effects of human error, robot body error, and flexible deformation result in low TCP accuracy, making it only suitable for single-piece pin-type tools.

[0004] In response, automation equipment manufacturers and robot manufacturers have proposed several methods, or calibration systems, for calibrating TCP (Cut-Off-Cut) systems. Currently, mainstream robot TCP calibration methods typically involve moving the robot along a closed path in the tool coordinate system and measuring the path deviation between the actual TCP and the theoretical TCP using sensors. Existing TCP calibration equipment often employs photoelectric sensors, such as patents CN 115229779 A and CN 115122316 A, which use four sets of photoelectric sensors. Furthermore, patent CN108940745A uses two sets of CCDs as TCP calibration sensors for dispensing needles. By improving the calibration method, a single set of CCDs can be used to complete the calibration, further simplifying the entire calibration process and reducing costs.

[0005] The TCP calibration methods described above can meet market needs. However, due to the large number and high performance of the sensors used, the TCP calibration equipment itself is often expensive and costly. The price of a single TCP calibration device is comparable to that of a complete robot. Therefore, there is still much room for optimization in terms of the cost of the TCP calibration methods and equipment. Summary of the Invention

[0006] The purpose of this invention is to at least address one of the aforementioned technical deficiencies.

[0007] Therefore, the purpose of this invention is to propose a monocular vision TCP calibration method and device for industrial robots to solve the problems mentioned in the background art and overcome the shortcomings of the prior art.

[0008] To achieve the above objectives, embodiments of the present invention provide a monocular vision TCP calibration method for industrial robots, comprising:

[0009] Step S1: Determine the tool coordinate system to be calibrated and the TCP calibrator coordinate system C dev This includes: after the TCP calibrator is installed and debugged, obtaining the TCP calibrator coordinate system C based on the actual installation location of the TCP calibrator and the attitude angles fed back by the attitude sensor. dev To the base coordinate system C base Transformation matrix After installing the tool, the tool coordinate system to be calibrated is obtained. and its coordinate system C to the flange flan Transformation matrix

[0010] Step S2: The mobile robot positions the tool tip at the calibration area of ​​the TCP calibrator;

[0011] Step S3, Measuring tool—flange transformation matrix The X and Y coordinate deviations include: the robot's position in the tool coordinate system as recorded by the monocular camera of the TCP calibrator. By calculating the position of the tool's end point before and after rotating it around the Z-axis, the center and radius of the TCP error circle are determined, and then the deviation e of the TCP's X and Y coordinates is measured. x e y ;

[0012] Step S4, Calibration tool—flange transformation matrix The X and Y coordinates;

[0013] Step S5, Measuring tool—flange transformation matrix Z-coordinate deviation;

[0014] Step S6, Calibration tool—flange transformation matrix The Z-coordinate;

[0015] Step S7: TCP accuracy check. Determine if the accuracy requirements are met. If they are met, proceed to step S8; otherwise, proceed to step S2. During this process, the calibrated TCP coordinates are obtained. By point Data update tool - flange transformation matrix And re-establish the tool coordinate system, denoted as Cool; set the coordinates The value is updated to points Repeat steps S2 to S6 to perform TCP recalibration;

[0016] Step S8, complete TCP calibration.

[0017] Preferably, in step S1, the tool coordinate system to be calibrated is... Transformation matrix via tool-flange Establish;

[0018] in, The description tool's work point is in the flange coordinate system C. flan The following pose P tool P tool =(x,y,z,α,β,γ);

[0019] Among them, P tool In the coordinate system, x, y, and z are Cartesian coordinates, describing the position of the tool's working point in the flange coordinate system; α, β, and γ are Euler angles, describing the orientation of the tool's working point in the flange coordinate system.

[0020] Preferably, in step S2, the transformation matrix from the TCP calibrator coordinate system to the base coordinate system is used. The calibration point is represented as a Cartesian point P in the robot's base coordinate system. calib, where P calib =(x calib y calib , z calib α calib ,β calib γ calib );

[0021] Where, x calib y calib z calib Let α be the Cartesian coordinates of the TCP calibrator coordinate system in the robot's base coordinate system; calib β calib γ calib The coordinates of the TCP calibrator are the Euler angles in the robot's base coordinate system;

[0022] Transformation matrix And Descartes point P calib Based on the installation pose of the TCP calibrator, the robot controller will plan the movement path so that the TCP moves to the Cartesian point P. calib .

[0023] Preferably, during TCP calibration, the monocular camera takes a picture and records the coordinates p of the tool's end point in the pixel coordinate system. pix =(x pix y pix According to pixel coordinate system C pix To TCP calibrator coordinate system C dev Transformation matrix The displacement Δx in pixel coordinates pix Δy pix Converted to displacement in the TCP calibrator coordinate system;

[0024] Let the resolution of each pixel in the viewfinder be ρ, then the displacement l in the TCP calibrator coordinate system is... x , l y , l z Represented as:

[0025]

[0026] Where, displacement Δx pix Δy pix and l x l y l z Both are vectors.

[0027] Preferably, in step S3, the measuring tool-flange transformation matrix is... The X-coordinate deviation includes:

[0028] (1) The robot moves to the Cartesian point in the tool coordinate system. say Let point 0 be the measurement point; take a picture of the tool with a monocular camera and record the pixel coordinates of the tool's end point in the viewfinder, denoted as .

[0029] (2) The robot moves to the Cartesian point in the tool coordinate system. say Measurement point 1; after the robot moves to the target point, the monocular camera takes a picture and records the corresponding pixel coordinates of the tool end point.

[0030] (3) The robot moves to the Cartesian point in the tool coordinate system. say Measurement point 2; after the robot moves to the target point, the monocular camera takes a picture and records the corresponding pixel coordinates of the tool end point.

[0031] (4) Based on pixel coordinates Calculate the displacement l of the tool end point in the TCP calibrator coordinate system during the two rotations. x1 l x2 .

[0032] Preferably, in step S4, the displacement l of the tool end point is obtained by measurement. x1 l x2 l y1 l y2 Solving the system of equations, we obtain the following system of equations:

[0033]

[0034] Solving for the tool-flange transformation matrix yields the solution. X and Y coordinate deviation e x e y This refers to the X and Y coordinate deviation of the TCP.

[0035] Modify the TCP coordinates for establishing the tool coordinate system within the robot controller. for Complete calibration tool - flange transformation matrix The calibration of the X and Y coordinates, where

[0036] Preferably, in step S6, the tool-flange transformation matrix is ​​measured. Z-coordinate deviation e z ;

[0037] Modify the TCP coordinates for establishing the tool coordinate system within the robot controller. for Complete calibration tool - flange transformation matrix Calibration of the Z-coordinate;

[0038] in,

[0039] Preferably, in step S7, if the tool-flange transformation matrix obtained during the second calibration process... X, Y, Z coordinate deviation e x e y e z If the following conditions are met, the TCP accuracy is considered to meet the requirements, and the TCP calibration ends; otherwise, repeat the step.

[0040]

[0041] Where, ε x ε y ε z These are the tool-flange transformation matrices. The accuracy of the X, Y, Z coordinates.

[0042] In another aspect, the present invention provides a monocular vision TCP calibration device for industrial robots, characterized in that the monocular vision TCP calibration device for industrial robots is used to perform the method described in any one of claims 1-8, wherein the monocular vision TCP calibration device for industrial robots is installed in the front area of ​​the robot body, and the TCP calibration device includes: a TCP calibrator and a TCP calibrator mounting base;

[0043] The TCP calibrator includes: a monocular camera, a backlight source, a calibration controller, an attitude sensor, communication components, and cables; wherein, the monocular camera and the backlight source are used for measuring TCP deviation; the calibration controller is used for processing sensor data, interacting with the robot controller, and calculating calibration parameters; and the attitude sensor is used for measuring the attitude angle of the TCP calibrator.

[0044] Preferably, as described in any of the above schemes, the TCP calibration device's workflow includes:

[0045] (1) Install and debug the TCP calibrator: Before installing the TCP calibrator, return it to zero. The zero point of the attitude sensor is the attitude angle of the robot base. Then, fix the TCP calibrator on the TCP calibrator mounting base with bolts, connect its power supply and the communication cable between it and the robot control cabinet, and wait for the robot controller to be able to interact normally with the TCP calibrator and for all sensors to work normally.

[0046] (2) Running the TCP calibration module: Run the TCP calibration module in the robot control system on the teach pendant or PC; when running the TCP calibration module, the user moves the robot under the guidance of the graphical interface so that the end of the tool is located in the calibration area of ​​the TCP calibrator; when the monocular camera of the TCP calibrator can normally recognize the end of the tool, the controller drives the robot to perform the movement according to the predetermined program; the monocular camera in the TCP calibrator will collect the position information of the end of the tool during the movement, and the calibration controller will calculate the TCP calibration value in real time; the TCP calibration value will be transmitted to the robot controller through the communication link;

[0047] (3) After receiving the TCP calibration data, the robot controller automatically updates the TCP parameters of the current tool and completes the TCP calibration.

[0048] The monocular vision TCP calibration method and device for industrial robots according to embodiments of the present invention employs a single 2D industrial camera as a sensor for measuring TCP deviation. By capturing images of the tool before and after movement using the 2D industrial camera, the TCP deviation is calculated by a calibration algorithm, thereby completing the TCP calibration. The monocular vision TCP calibration method of the present invention is simple in principle and easy to operate. The accompanying monocular vision TCP calibration hardware for industrial robots is low-cost, highly accurate, and fast, and can be adapted to a wide range of tool types, possessing significant practical value and broad market prospects.

[0049] Compared with the prior art, the present invention has the following advantages:

[0050] 1. The monocular vision TCP calibration method can measure the TCP deviation with high precision and complete the automatic calibration of TCP.

[0051] 2. The monocular vision TCP calibration method can be adapted to tools of various shapes and structures, and the TCP calibration location (including tool end point, tool working point, and tool external point) can be selected according to user needs.

[0052] 3. The monocular vision TCP calibration method is simple in principle, the TCP calibration equipment is low in cost, and it can calibrate the TCP of multiple robots.

[0053] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0054] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0055] Figure 1A flowchart of a monocular vision TCP calibration method for industrial robots according to an embodiment of the present invention;

[0056] Figure 2 To determine the tool coordinate system to be calibrated according to embodiments of the present invention and the TCP calibrator coordinate system C dev A schematic diagram;

[0057] Figure 3 This is a diagram showing the actual position of the tool end point after moving the TCP to the calibration point according to an embodiment of the present invention.

[0058] Figure 4 This is a schematic diagram illustrating the actual position of the tool according to an embodiment of the present invention and the tool position calculated in the controller after establishing the tool coordinate system;

[0059] Figure 5 To provide a robot in the tool coordinate system according to an embodiment of the present invention A schematic diagram of rotation around the Z-axis;

[0060] Figure 6 This is a schematic diagram showing the position of the image machine in the viewfinder of the tool when measuring the X-coordinate deviation according to an embodiment of the present invention;

[0061] Figure 7 for Figure 6 A schematic diagram of the projection distribution of the end point of the measuring tool in the XY plane of the base coordinate system;

[0062] Figure 8 This is a schematic diagram showing the position of the image machine in the viewfinder of the tool when measuring the Y-coordinate deviation according to an embodiment of the present invention;

[0063] Figure 9 for Figure 8 A schematic diagram of the projection distribution of the end point of the measuring tool in the XY plane of the base coordinate system;

[0064] Figure 10 The flange transformation matrix is ​​a measuring tool according to an embodiment of the present invention. A schematic diagram of the Z-coordinate deviation;

[0065] Figure 11 This is a schematic diagram showing the position of the image machine in the viewfinder of the tool when measuring the Z-coordinate deviation according to an embodiment of the present invention.

[0066] Figure 12 for Figure 11 A schematic diagram of the projection distribution of the end point of the measuring tool in the XZ plane of the base coordinate system;

[0067] Figure 13 This is a schematic diagram of a tip tool according to an embodiment of the present invention mounted on the flange of a test robot in this example;

[0068] Figure 14 This is a schematic diagram of the four-point method result in a robot controller according to an embodiment of the present invention;

[0069] Figure 15 This is a schematic diagram of a monocular vision TCP calibration device for industrial robots according to an embodiment of the present invention;

[0070] Figure 16 This is a flowchart illustrating the operation of a monocular vision TCP calibration device for industrial robots according to an embodiment of the present invention. Detailed Implementation

[0071] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0072] like Figure 1 As shown, the monocular vision TCP calibration method for industrial robots according to an embodiment of the present invention includes:

[0073] Step S1: Determine the tool coordinate system to be calibrated and the TCP calibrator coordinate system C dev .

[0074] Specifically, once the TCP calibrator is installed and debugged, the coordinate system C of the TCP calibrator is obtained based on the actual installation location of the TCP calibrator and the attitude angles fed back by the attitude sensor. dev To the base coordinate system C base Transformation matrix After installing the tool, the tool coordinate system to be calibrated is obtained. and its coordinate system C to the flange flan Transformation matrix

[0075] like Figure 2 As shown, once the TCP calibrator is installed and debugged, the coordinate system C of the TCP calibrator can be obtained based on the actual installation location of the TCP calibrator and the attitude angles fed back by the attitude sensor. dev To the base coordinate system C base Transformation matrix

[0076] After installing the tools, the tool coordinate system to be calibrated is obtained. and its coordinate system C to the flange flan Transformation matrix Tool coordinate system to be calibrated Through the tool-flange transformation matrix Established. Among them, The description tool's work point is in the flange coordinate system C. flan The following pose P tool .

[0077] P tool =(x,y,z,α,β,γ) (1)

[0078] P tool In the coordinate system, x, y, and z are Cartesian coordinates, describing the position of the tool's working point in the flange coordinate system. α, β, and γ are Euler angles, describing the orientation of the tool's working point in the flange coordinate system.

[0079] It should be noted that P tool The representation of attitude includes, but is not limited to, the form mentioned above; it can also be represented by quaternions, etc.

[0080] Tools - Flange Transformation Matrix and P tool The position P of the tool's working point can be obtained through mechanical design theory or calibration using the four-point method. Under the influence of factors such as installation, use, and wear, the position P of the tool's working point... tool There is usually a deviation from the actual value, which causes the tool coordinate system to be calibrated to deviate. With respect to the actual tool coordinate system C tool There is a deviation. If the deviation is too large, subsequent calibration steps may not be able to proceed normally. Therefore, the TCP calibration method described in this invention has limitations regarding the coordinate system of the tool to be calibrated. A certain level of precision is required.

[0081] In summary, the calibration TCP in this embodiment of the invention refers to the calibration tool's working point in the flange coordinate system C. flan P position tool and transformation matrix To calibrate the tool coordinate system Corrected to the actual tool coordinate system C tool .

[0082] Step S2: The mobile robot positions the tool tip at the calibration area of ​​the TCP calibrator.

[0083] Specifically, this step involves moving the TCP to the calibration point, that is, moving the robot so that the tool tip is located in the calibration area of ​​the TCP calibrator.

[0084] TCP refers to the tool coordinate system. The origin of TCP typically refers to the tool's end point or the tool's working point (TCP can also be a non-tool end point, as defined by the user). For ease of description, TCP in this example specifically refers to the tool's end point.

[0085] TCP is described as a Cartesian point in the flange coordinate system. Its Cartesian coordinates and P tool The same applies; both Euler angles are 0.

[0086] The calibration point refers to the coordinate system C of the TCP calibrator. dev The origin of the calibrator is defined at the geometric center of the TCP calibrator. This point is the intersection of the focal plane of the monocular camera and the extended line of the viewfinder center. Here, the monocular camera can capture the clearest tool outline and ensure that the tool image remains within the viewfinder during subsequent calibration movements.

[0087] Based on the transformation matrix from the TCP calibrator coordinate system to the base coordinate system in step S1 The calibration point can be represented as a Cartesian point P in the robot's base coordinate system. calib .

[0088] P calib =(x calib y calib , z calib α calib ,β calib γ calib (2)

[0089] Where, x calib、 y calib z calib Let α be the Cartesian coordinates of the TCP calibrator coordinate system in the robot's base coordinate system. calib β calib γ calib Let be the Euler angles of the TCP calibrator coordinate system in the robot's base coordinate system. Transformation matrix. And Descartes point P calib The method for obtaining the TCP calibrator's values ​​depends on its installation orientation; this invention does not elaborate on this. The robot controller will plan the movement path so that the TCP moves to the Cartesian point P. calib .

[0090] like Figure 3 As shown, after moving the TCP to the calibration point, due to the tool coordinate system... There is a discrepancy, so the actual end point of the tool is not in the center of the viewfinder.

[0091] During TCP calibration, the monocular camera will take a picture and record the coordinates p of the tool's end point in the pixel coordinate system. pix =(x pix y pix According to pixel coordinate system C) pix To TCP calibrator coordinate system C dev Transformation matrix The displacement Δx in pixel coordinates can be pix Δy pix Convert the displacement to the TCP calibrator coordinate system. Let the resolution of each pixel in the viewfinder be ρ (in mm), then the displacement l in the TCP calibrator coordinate system... x , l y , l z Represented as:

[0092]

[0093] Since the relative position of the monocular camera in the TCP calibrator is fixed, the pixel coordinate system C pix To TCP calibrator coordinate system C dev Transformation matrix It is a known constant, and its data is stored in the calibration controller. Displacement Δx pix Δy pix and l x l y l z Both are vectors.

[0094] Step S3, Measuring tool - flange transformation matrix The X and Y coordinate deviations include: the robot's position in the tool coordinate system as recorded by the monocular camera of the TCP calibrator. By calculating the position of the tool's end point before and after rotating it around the Z-axis, the center and radius of the TCP error circle are determined, and then the deviation e of the TCP's X and Y coordinates is measured. x e y .

[0095] Specifically, step S3 will use an example to illustrate the measuring tool – the flange transformation matrix. The method and process for determining the X and Y coordinate deviations.

[0096] like Figure 4 As shown, Figure 4 The solid line outline represents the actual position of the tool, while the dashed line represents the tool position calculated in the controller after establishing the tool coordinate system. In this embodiment of the invention, the tool TCP is the tool end point. Due to the deviation of TCP, the actual tool end point position differs from the Cartesian point in the flange coordinate system of the controller. The positions are inconsistent. Let the actual tool endpoint be the actual TCP, and the tool coordinate system... The origin is the error TCP, which is the TCP to be calibrated later. The actual TCP and the error TCP of the tool are then compared in the flange coordinate system C. flan There is a deviation e below x e y e z .

[0097] like Figure 5 As shown, due to the deviation e on the X and Y axes of TCP x e y Then when the robot is in the tool coordinate system When rotating around the Z-axis, the actual tool end point will move along an arc. Let this arc be the TCP error circle. The center of this arc is the TCP to be calibrated in the robot controller, and the radius of the arc is...

[0098] Measuring tools - flange transformation matrix Methods for determining X and Y coordinate deviations: Recording the robot's position in the tool coordinate system using a monocular camera. By determining the position of the tool's end point before and after rotating around the Z-axis, the center and radius of the TCP error circle can be calculated based on the geometric properties of the arc. This allows for the measurement of the deviation e in the TCP's X and Y coordinates. x e y .

[0099] Measuring tools - flange transformation matrix The method for determining the X-coordinate deviation is as follows:

[0100] (1) The robot moves to the Cartesian point in the tool coordinate system. say Let point 0 be the measurement point. Take a picture of the tool with a monocular camera and record the pixel coordinates of the tool's endpoint within the viewfinder, denoted as .

[0101] (2) The robot moves to the Cartesian point in the tool coordinate system. say Measurement point 1. After the robot moves to the target point, the monocular camera takes a picture and records the corresponding pixel coordinates of the tool end point.

[0102] (3) The robot moves to the Cartesian point in the tool coordinate system. say Measurement point 2. After the robot moves to the target point, the monocular camera takes a picture and records the corresponding pixel coordinates of the tool end point.

[0103] (4) Based on pixel coordinates Calculate the displacement l of the tool end point in the TCP calibrator coordinate system during the two rotations. x1 l x2 .

[0104] like Figure 6 As shown, the displacement l in step (4) x1 l x2 Transformation matrix for measuring tools - flange The X-coordinate deviation is the displacement of the tool end point on the X-axis in the TCP calibrator coordinate system.

[0105]

[0106] like Figure 7 As shown, the projections of the tool end points of measurement points 0, 1, and 2 onto the XY plane of the base coordinate system lie on the TCP error circle. Based on the displacement l obtained previously... x1 , l x2 The following expression can be obtained from geometric relationships.

[0107]

[0108] in θ = atan(e y / e x )

[0109] Measuring tools - flange transformation matrix The method for calculating the Y-coordinate deviation is as follows:

[0110] (1) The robot moves to the Cartesian point in the tool coordinate system. say Let point 0 be the measurement point. Take a picture of the tool with a monocular camera and record the pixel coordinates of the tool's endpoint within the viewfinder, denoted as .

[0111] (2) The robot moves to the Cartesian point in the tool coordinate system. say Measurement point 1. After the robot moves to the target point, the monocular camera takes a picture and records the corresponding pixel coordinates of the tool end point.

[0112] (3) The robot moves to the Cartesian point in the tool coordinate system. say Measurement point 2. After the robot moves to the target point, the monocular camera takes a picture and records the corresponding pixel coordinates of the tool end point.

[0113] (4) Based on pixel coordinates Calculate the displacement l of the tool end point in the TCP calibrator coordinate system during the two rotations. y1 l y2 .

[0114] like Figure 8 As shown, the displacement l in step (4) y1 l y2 Transformation matrix for measuring tools - flange The Y-coordinate deviation is the displacement of the tool end point on the X-axis in the TCP calibrator coordinate system.

[0115]

[0116] like Figure 9 As shown, the projections of the tool end points of measurement points 0, 1, and 2 onto the XY plane of the TCP calibrator coordinate system lie on the TCP error circle. Based on the displacement l obtained previously... x1 , l x2 From geometric relations, we can obtain the following expression:

[0117] The following expression can be obtained from geometric relationships, where the formulas for r and θ are consistent with those used when calibrating the X-axis deviation.

[0118]

[0119] in θ = atan(e y / e x ).

[0120] Step S4, Calibration tool - flange transformation matrix The X and Y coordinates.

[0121] Specifically, in step S3, the displacement l at the end point of the tool was measured. x1 l x2 l y1 l y2 Solving the system of equations, we obtain the following set of equations.

[0122]

[0123] The above system of equations is a nonlinear system of equations. Solving the nonlinear system of equations yields the tool-flange transformation matrix. X and Y coordinate deviation e x e y This refers to the X and Y coordinate deviation of TCP.

[0124] Modify the TCP coordinates for establishing the tool coordinate system within the robot controller. for Complete the calibration tool—flange transformation matrix The calibration of the X and Y coordinates.

[0125] Step S5, Measuring tool—flange transformation matrix Z-coordinate deviation.

[0126] like Figure 10As shown, the solid line outline represents the actual position of the tool, while the dashed line represents the tool position calculated in the controller after establishing the tool coordinate system. In an embodiment of the present invention, TCP has a deviation e on the Z-axis component. z When the robot is in the tool coordinate system When rotating around the X or Y axis, the actual movement trajectory of the tool's end effector is also on an arc. This arc is called the TCP error circle, the center of which is the TCP to be calibrated in the robot controller, and the radius of the arc is r = |e^(-π / 2)|^(-π / 2) z |

[0127] Measuring tools—flange transformation matrix The method for measuring the Z-coordinate deviation is similar to the method for measuring the X and Y coordinate deviations in step S4.

[0128] Measuring tools—flange transformation matrix The method for determining the X-coordinate deviation is as follows:

[0129] (1) The robot moves to the Cartesian point in the tool coordinate system. say Let point 0 be the measurement point. Take a picture of the tool with a monocular camera and record the pixel coordinates of the tool's endpoint within the viewfinder, denoted as .

[0130] (2) The robot moves to the Cartesian point in the tool coordinate system. say Measurement point 1. After the robot moves to the target point, the monocular camera takes a picture and records the corresponding pixel coordinates of the tool end point.

[0131] (3) The robot moves to the Cartesian point in the tool coordinate system. remember Measurement point 2. After the robot moves to the target point, the monocular camera takes a picture and records the corresponding pixel coordinates of the tool end point.

[0132] (4) Based on pixel coordinates Calculate the displacement l of the tool end point in the pixel coordinate system during the two rotations. z1 l z2 .

[0133] like Figure 11 As shown, the displacement l mentioned in step (4) z1 l z2 Transformation matrix for measuring tools - flange The Z-coordinate deviation is the displacement of the tool's end point on the X-axis in the pixel coordinate system.

[0134]

[0135] like Figure 12 As shown, the projections of the tool end points of measurement points 0, 1, and 2 onto the XZ plane of the TCP calibrator coordinate system lie on the TCP error circle. Based on the previously obtained displacement l... z1 , l z2 From geometric relations, we can obtain the following expression:

[0136]

[0137] Step S6, Calibration tool - flange transformation matrix The Z-coordinate.

[0138] Specifically, after step S5, the tool-flange transformation matrix was measured and obtained. Z-coordinate deviation e z .

[0139] Modify the TCP coordinates for establishing the tool coordinate system within the robot controller. for Complete calibration tool - flange transformation matrix The calibration of the Z-coordinate. Among them,

[0140]

[0141] Step S7: TCP accuracy check. Determine if the accuracy requirements are met. If they are met, proceed to step S8; otherwise, proceed to step S2. During this process, the calibrated TCP coordinates are obtained. By point Data update tool - flange transformation matrix And re-establish the tool coordinate system, denoted as C. tool ; coordinates The value is updated to points Repeat steps S2 to S6 to perform TCP recalibration.

[0142] The calibrated TCP coordinates were obtained through the above steps. By point Data update tool—Flange transformation matrix And re-establish the tool coordinate system, denoted as C. tool Coordinates The value is updated to points Repeat steps S2 to S6 to perform TCP recalibration.

[0143] If the tool-flange transformation matrix is ​​obtained during the second calibration process... X, Y, Z coordinate deviation e x e y ez If the following conditions are met, the TCP accuracy is considered to meet the requirements, and the TCP calibration ends; otherwise, repeat the step.

[0144]

[0145] Where, ε x ε y ε z These are the tool-flange transformation matrices. The precision of the X, Y, and Z coordinates, which is user-defined.

[0146] Step S8, complete TCP calibration.

[0147] The following is for reference. Figure 3 The effects of the present invention will be described with reference to specific embodiments, and all data in the embodiments are in mm.

[0148] Figure 13 The image shows a pointed tool mounted on the flange of the test robot in this example.

[0149] A coordinate measuring machine can be used to measure the coordinates from the tool tip to the center of the robot flange, thus obtaining the actual tool-flange transformation matrix. Practical tool—flange transformation matrix The specific representation is shown in Table 1:

[0150] Table 1

[0151] 6.0099e-05 1.0000e+00 2.0000e-03 0.042 9.9939e-05 -2.0000e-03 1.0000e+00 100.530 0 0 0 1

[0152] The practical tool described above—the flange transformation matrix The data inside the thick box on the right, from top to bottom, is the tool-flange transformation matrix. The X, Y, and Z coordinates are used to determine the tool's TCP (Coordinate Transmission Point). The tool's TCP is a three-element vector. The actual TCP obtained using a coordinate measuring machine is shown in Table 2.

[0153] Table 2

[0154] 0.051 0.042 100.530

[0155] The tool coordinate system is established using the four-point method. The result of the four-point method in the robot controller is as follows: Figure 14 As shown in Table 3, the TCP of the tool in the robot controller is as follows:

[0156] Table 3

[0157] -0.320 0.240 100.040

[0158] It can be seen that the TCP of the tool coordinate system established using the four-point method deviates from the actual TCP of the tool. Therefore, the tool-flange transformation matrix to be calibrated obtained by the four-point method... As shown in Table 4:

[0159] Table 4

[0160] 6.0099e-05 1.0000e+00 2.0000e-03 0.240 9.9939e-05 -2.0000e-03 1.0000e+00 100.040 0 0 0 1

[0161] The TCP deviation that can be measured after using the monocular vision TCP calibration method described in this invention is shown in Table 5:

[0162] Table 5

[0163] 0.380 -0.230 0.044

[0164] The TCP data of the tool in the controller after monocular vision TCP calibration is shown in Table 6:

[0165] Table 6

[0166] 0.060 0.010 100.480

[0167] The calibrated tool-flange transformation matrix As shown in Table 7:

[0168] Table 7

[0169] 6.0099e-05 1.0000e+00 2.0000e-03 0.010 9.9939e-05 -2.0000e-03 1.0000e+00 100.480 0 0 0 1

[0170] At this point, the calibrated tool—the flange transformation matrix—is... It can be considered to be related to the actual tool—the flange transformation matrix. They are basically the same now; TCP calibration is complete.

[0171] In an embodiment of the present invention, the TCP calibration coordinate accuracy is set to ε. x =0.5, ε y =0.5, ε z =0.5.

[0172] like Figure 15 As shown, this embodiment of the invention also provides a monocular vision TCP calibration device for industrial robots, used to perform the above-described calibration method.

[0173] The tool to be calibrated is mounted on the end flange of the robot body. The monocular vision TCP calibration device for industrial robots is located in the front area of ​​the robot body. The TCP calibration device includes a TCP calibrator and a TCP calibrator mounting base.

[0174] Specifically, the TCP calibrator integrates a monocular camera, a backlight source, a calibration controller, an attitude sensor, communication components, and cables. The monocular camera and backlight source are used to measure TCP deviation. The calibration controller processes sensor data, interacts with the robot controller, and calculates calibration parameters. The attitude sensor measures the attitude angles of the TCP calibrator.

[0175] The TCP calibrator has multiple mounting holes, allowing it to be installed not only on the included TCP calibrator mounting base but also independently on a workbench, wall, or other locations. The height of the TCP calibrator mounting base is adjustable, and its bottom has pre-drilled holes for bolt or screw mounting to the ground. Furthermore, the TCP calibration equipment comes with a storage box. When not in use, the TCP calibrator's vision camera lens cap can be closed, and the mounting base can be retracted to its minimum height and stored in the storage box.

[0176] like Figure 16 As shown, the workflow of the monocular vision TCP calibration device for industrial robots in this embodiment of the invention is as follows:

[0177] First, install and debug the TCP calibrator. Installing and debugging the TCP calibrator means: before installing the TCP calibrator, return it to zero; the zero point of the attitude sensor is the attitude angle of the robot base. Then, fix the TCP calibrator to the TCP calibrator mounting bracket (or elsewhere where pre-drilled mounting holes are provided), connect its power supply and the communication cable between it and the robot control cabinet, and wait until the robot controller can interact normally with the TCP calibrator and all sensors are working properly.

[0178] Secondly, run the TCP calibration module. Running the TCP calibration module means that the user needs to run the TCP calibration module within the robot control system on the teach pendant or PC. When running the TCP calibration module, the user moves the robot under the guidance of the graphical interface until the tool tip is located in the calibration area of ​​the TCP calibrator. Once the monocular camera of the TCP calibrator can correctly identify the tool tip, the user needs to enable TCP calibration. Afterward, the controller drives the robot to perform a series of movements according to the predetermined program. The monocular camera in the TCP calibrator will collect the position information of the tool tip during the movement, and the calibration controller will calculate the TCP calibration value in real time. The TCP calibration value will be transmitted to the robot controller through a communication link, which includes, but is not limited to, wired communication links and wireless communication links.

[0179] Finally, after receiving the TCP calibration data, the robot controller automatically updates the TCP parameters of the current tool to complete the TCP calibration.

[0180] In summary, the monocular vision TCP calibration method and equipment for industrial robots in this embodiment of the invention uses a monocular camera to photograph and measure the actual TCP position of the tool, and solves the TCP deviation based on geometric properties. In addition, it proposes an algorithm and technology based on visual recognition of the tool contour to calculate the tool end point, tool working point, and user-defined TCP pixel coordinates.

[0181] It should be noted that the term "monocular vision TCP calibration" refers to any TCP calibration method or equipment used in industrial robots, and descriptions that are synonymous or similar to "monocular vision" or "single camera, visual measurement" are protected by this invention.

[0182] The monocular vision TCP calibration method and equipment for industrial robots according to this invention uses a single 2D industrial camera as the measurement sensor for TCP deviation. By capturing images of the tool before and after movement using the 2D industrial camera, the TCP deviation is calculated by a calibration algorithm, thus completing the TCP calibration. This monocular vision TCP calibration method is simple in principle and easy to operate. The accompanying monocular vision TCP calibration hardware for industrial robots is low-cost, highly accurate, and fast, and it is compatible with a wide range of tool types, possessing significant practical value and broad market prospects.

[0183] Compared with the prior art, the present invention has the following advantages:

[0184] 1. The monocular vision TCP calibration method can measure the TCP deviation with high precision and complete the automatic calibration of TCP.

[0185] 2. The monocular vision TCP calibration method can be adapted to tools of various shapes and structures, and the TCP calibration location (including tool end point, tool working point, and tool external point) can be selected according to user needs.

[0186] 3. The monocular vision TCP calibration method is simple in principle, the TCP calibration equipment is low in cost, and it can calibrate the TCP of multiple robots.

[0187] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0188] It will be readily understood by those skilled in the art that this invention includes any combination of the inventive description and specific embodiments outlined in the foregoing specification, as well as the various parts shown in the accompanying drawings. Due to space limitations and for the sake of brevity, not all of these combinations have been described in detail. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

[0189] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A monocular vision TCP calibration method for industrial robots, characterized in that, Includes the following steps: Step S1: Determine the tool coordinate system to be calibrated and TCP calibrator coordinate system This includes: once the TCP calibrator is installed and debugged, obtaining the TCP calibrator coordinate system based on the actual installation location of the TCP calibrator and the attitude angles fed back by the attitude sensor. To base coordinate system Transformation matrix After installing the tool, the tool coordinate system to be calibrated is obtained. and its coordinate system to the flange Transformation matrix The attitude sensor is used to measure the attitude angle of the TCP calibrator. Step S2: The mobile robot positions the tool tip at the calibration area of ​​the TCP calibrator; Step S3, Measuring tool—flange transformation matrix The X and Y coordinate deviations include: the robot's position in the tool coordinate system as recorded by the monocular camera of the TCP calibrator. By calculating the position of the tool's end point before and after rotating it around the Z-axis, the center and radius of the TCP error circle are determined, and then the deviation of the TCP's X and Y coordinates is measured. , ; Measuring tools—flange transformation matrix The X-coordinate deviation includes: (1) The robot moves to the Cartesian point in the tool coordinate system. ,say Let point 0 be the measurement point; take a picture of the tool with a monocular camera and record the pixel coordinates of the tool's end point in the viewfinder, denoted as . ; (2) The robot moves to the Cartesian point in the tool coordinate system. ,say Measurement point 1; after the robot moves to the target point, the monocular camera takes a picture and records the corresponding pixel coordinates of the tool end point. ; (3) The robot moves to the Cartesian point in the tool coordinate system. ,say Measurement point 2; after the robot moves to the target point, the monocular camera takes a picture and records the corresponding pixel coordinates of the tool end point. ; (4) Based on pixel coordinates , , Calculate the displacement of the tool end point in the TCP calibrator coordinate system during the two rotations. , ; Measuring tools—flange transformation matrix The method for calculating the Y-coordinate deviation is as follows: (1) The robot moves to the Cartesian point in the tool coordinate system. ,say Let point 0 be the measurement point; take a picture of the tool with a monocular camera and record the pixel coordinates of the tool's end point in the viewfinder, denoted as . ; (2) The robot moves to the Cartesian point in the tool coordinate system. ,say Measurement point 1; after the robot moves to the target point, the monocular camera takes a picture and records the corresponding pixel coordinates of the tool end point. ; (3) The robot moves to the Cartesian point in the tool coordinate system. ,say Measurement point 2; after the robot moves to the target point, the monocular camera takes a picture and records the corresponding pixel coordinates of the tool end point. ; (4) Based on pixel coordinates , , Calculate the displacement of the tool end point in the TCP calibrator coordinate system during the two rotations. , ; Among them, the displacement of the tool end point is obtained by measurement. , , , Solving the system of equations, we obtain the following system of equations: The solution yields the flange transformation matrix. X and Y coordinate deviation , This refers to the X and Y coordinate deviation of the TCP. Step S4, Calibration tool—flange transformation matrix The X and Y coordinates; This includes modifying the TCP coordinates used to establish the tool coordinate system within the robot controller. for Complete the calibration of the tool—flange transformation matrix. Calibration of X and Y coordinates, where ; Step S5, Measuring tool—flange transformation matrix Z-coordinate deviation; Step S6, Calibration tool—flange transformation matrix The Z-coordinate; Step S7: TCP accuracy check. Determine if the accuracy requirements are met. If they are met, proceed to step S8; otherwise, proceed to step S2. During this process, the calibrated TCP coordinates are obtained. by point Data update tool—Flange transformation matrix And re-establish the tool coordinate system, denoted as ; coordinates The value is updated to points Repeat steps S2 to S6 to perform TCP recalibration; Step S8, complete TCP calibration.

2. The monocular vision TCP calibration method for industrial robots as described in claim 1, characterized in that, In step S1, the tool coordinate system to be calibrated Using the tool—Flange Transformation Matrix Establish; in, Description tool operation point in flange coordinate system Lower position , ; in, In , , Using Cartesian coordinates, this describes the position of the tool's working point in the flange coordinate system; , , The Euler angles describe the orientation of the tool's working point in the flange coordinate system.

3. The monocular vision TCP calibration method for industrial robots as described in claim 1, characterized in that, In step S2, the transformation matrix from the TCP calibrator coordinate system to the base coordinate system is used. The calibration point is represented as a Cartesian point in the robot's base coordinate system. ,in ; in, , , The coordinates of the TCP calibrator coordinate system are Cartesian coordinates in the robot's base coordinate system; , , The coordinates of the TCP calibrator are the Euler angles in the robot's base coordinate system; Transformation matrix and Descartes point The robot controller will plan the movement path based on the installation pose of the TCP calibrator, so that the TCP moves to the Cartesian point. .

4. The monocular vision TCP calibration method for industrial robots as described in claim 3, characterized in that, During TCP calibration, the monocular camera will take a picture and record the coordinates of the tool's end point in the pixel coordinate system. According to pixel coordinate system To TCP calibrator coordinate system Transformation matrix The displacement in pixel coordinates , Convert to displacement in the TCP calibrator coordinate system; Let the resolution of each pixel in the viewfinder be . The displacement in the TCP calibrator coordinate system , , Represented as: Among them, displacement , as well as , , Both are vectors.

5. The monocular vision TCP calibration method for industrial robots as described in claim 1, characterized in that, In step S6, the tool-flange transformation matrix is ​​measured. Z-coordinate deviation ; Modify the TCP coordinates for establishing the tool coordinate system within the robot controller. for Complete the calibration of the tool—flange transformation matrix. Calibration of the Z-coordinate; in, .

6. The monocular vision TCP calibration method for industrial robots as described in claim 1, characterized in that, In step S7, if the tool-flange transformation matrix obtained during the second calibration process... X, Y, Z coordinate deviation , , If the following conditions are met, the TCP accuracy is considered to meet the requirements, and the TCP calibration ends; otherwise, repeat the step. in, , , These are the tool-flange transformation matrices. The accuracy of the X, Y, Z coordinates.

7. A monocular vision TCP calibration device for industrial robots, characterized in that, The monocular vision TCP calibration device for industrial robots is used to perform the method according to any one of claims 1-6, wherein the monocular vision TCP calibration device for industrial robots is installed in the front area of ​​the robot body, and the TCP calibration device includes: a TCP calibrator and a TCP calibrator mounting base; The TCP calibrator includes: a monocular camera, a backlight source, a calibration controller, an attitude sensor, communication components, and cables; wherein, the monocular camera and the backlight source are used for measuring TCP deviation; the calibration controller is used for processing sensor data, interacting with the robot controller, and calculating calibration parameters; and the attitude sensor is used for measuring the attitude angle of the TCP calibrator.

8. The monocular vision TCP calibration device for industrial robots as described in claim 7, characterized in that, The TCP calibration device workflow includes: (1) Install and debug the TCP calibrator: Before installing the TCP calibrator, return it to zero. The zero point of the attitude sensor is the attitude angle of the robot base. Then, fix the TCP calibrator on the TCP calibrator mounting base with bolts, connect its power supply and the communication cable between it and the robot control cabinet, and wait for the robot controller to be able to interact normally with the TCP calibrator and for all sensors to work normally. (2) Running the TCP calibration module: Run the TCP calibration module in the robot control system on the teach pendant or PC; when running the TCP calibration module, the user moves the robot under the guidance of the graphical interface so that the end of the tool is located in the calibration area of ​​the TCP calibrator; when the monocular camera of the TCP calibrator can normally recognize the end of the tool, the controller drives the robot to perform the movement according to the predetermined program; the monocular camera in the TCP calibrator will collect the position information of the end of the tool during the movement, and the calibration controller will calculate the TCP calibration value in real time; the TCP calibration value will be transmitted to the robot controller through the communication link; (3) After receiving the TCP calibration data, the robot controller automatically updates the TCP parameters of the current tool and completes the TCP calibration.

Images