Method and System for Calibrating Robot Tool Center Point Based on Offline Programming Software

Abstract

The present invention relates to a method and system for calibrating the robot tool center point based on an offline programming software. The method coincides the TCP of the fixture to be calibrated with the workpiece coordinate system, reads the joint values and the rotational position values of each axis of the robot when they coincide, inputs them into the industrial control computer, and uses the offline programming software installed in the industrial control computer to perform forward kinematics calculations in a virtual environment to obtain the value of the tool coordinate system TCP. The method and system for calibrating the robot tool center point based on the offline programming software according to the present invention utilize the virtual reproducibility of the offline programming software, visually read the corresponding coordinate values, and thus realize the rapid calibration of the tool center point of the robot for the fixture.

Description

Technical Field

[0001] The present invention relates to the field of robots, and particularly to a method and system for calibrating the tool center point of a robot based on offline programming software. Background Art

[0002] With the popularization of industrial intelligence, industrial robots have been widely promoted and used in enterprise production. Enterprises are paying more and more attention to the operation technology of robots. Among them, in the commissioning and operation process of industrial robots, the coordinate system of the robot is of great importance. Among the various coordinate systems of the robot, the accuracy of the tool coordinate system directly affects the trajectory accuracy of the robot. Therefore, establishing an accurate and fast calibration method is of great significance for the application of robots.

[0003] The existing calibration methods generally construct the D-H coordinate system of the robot. Generally, the end point positions of the flange are calculated from the six-axis degrees of freedom of the robot, and then the corresponding Euler angle matrix is obtained through the translation and rotation combination of the homogeneous transformation of the whole body, and then the X, Y, and Z position values of the end TCP and the corresponding U, V, and W attitude values are obtained to construct the end tool coordinate system; then the TCP is calibrated.

[0004] The currently commonly used TCP calibration methods are the 6-point method and the 23-point method. The coincidence of points in this way must be completed manually and requires fine adjustment. If the alignment is inaccurate, it is easy to have too large an error; and for special-shaped jigs, that is, jigs without end tips, it is difficult to calibrate, and corresponding special calibration needles need to be made for calibration, which wastes materials, and there will be corresponding assembly errors when the robot jigs are reinstalled. Therefore, TCP calibration is very time-consuming and laborious, affecting the working efficiency of the robot. There is also a commonly used calibration method at present, which is to perform calibration operations through a laser calibration instrument, but it requires a high cost, and there are also certain operation difficulties and light and space limitations in the actual site for calibration.

[0005] Therefore, there is a need for a fast calibration method that can effectively calibrate special-shaped jigs without end tips quickly. Summary of the Invention

[0006] Based on this, the purpose of the present invention is to provide a method and system for calibrating the tool center point of a robot based on offline programming software. By using the virtual reproducibility of the offline programming software, the corresponding coordinate values are visually read, so as to realize the rapid calibration of the tcp point positions of the robot for the jig.

[0007] A method for calibrating the tool center point of a robot based on offline programming software includes the following steps:

[0008] Step S1: Establish a robot base coordinate system;

[0009] Step S2: Calibrate the workpiece coordinate system to obtain the X, Y, Z, U, V, and W values of the workpiece coordinate system;

[0010] Step S3: Enter the X, Y, Z, U, V, and W values of the generated workpiece coordinate system into the industrial control computer. At this time, the industrial control computer generates the corresponding position and attitude of the workpiece coordinate system;

[0011] Step S4: Install a jig at the end joint of the robot and mark a preset point, which is the TCP of the jig to be calibrated; Move each joint of the robot to make the TCP of the jig to be calibrated coincide with the tip point of the fixed calibration needle;

[0012] Step S5: Read the joint values of the robot and the rotational position values of each axis and input them into the industrial control computer;

[0013] Step S6: Set the TCP value of the jig in the virtual environment of the offline programming software of the industrial control computer;

[0014] Step S7: The industrial control computer performs the forward kinematic calculation of the robot D-H coordinate system in the virtual environment to obtain the corresponding TCP value of the tool coordinate system; Input the TCP value into the manual teaching pendant, and the calibration of the TCP of the tool coordinate system is completed.

[0015] A method and system for calibrating the tool center point of a robot based on an offline programming software, by utilizing the virtual reproducibility of the offline programming software and visually reading the corresponding coordinate values, thereby realizing the rapid calibration of the tool center point of the robot for the jig.

[0016] Further, in the above method for calibrating the tool center point of the robot, the coordinates of the workpiece coordinate system are obtained by homogeneous transformation rotation and translation calculation of the base coordinate system.

[0017] Further, the above method for calibrating the tool center point of the robot uses the three-point marking method to calibrate the workpiece coordinate system. The robot control system calculates the workpiece coordinate system and generates the X, Y, Z, U, V, and W values of the workpiece coordinate system in the manual teaching pendant.

[0018] A system for calibrating the tool center point of a robot based on an offline programming software, used to implement the method for calibrating the tool center point of a robot based on an offline programming software, includes: a robot, a fixed calibration needle, a jig, a robot control module, a manual teaching pendant, and an industrial control computer;

[0019] The robot includes a fixedly installed robot base;

[0020] The fixed calibration needle is fixedly arranged relative to the robot base;

[0021] The jig is installed at the end of the robot;

[0022] The robot control module is signal-connected to the robot; based on the robot control system and algorithms, the robot control module is used to calculate the workpiece coordinate system of the fixed calibration needle.

[0023] The manual teaching pendant is signal-connected to the robot control system and is used to control the robot to drive the jig to move.

[0024] The industrial computer is signal-connected to the manual teaching pendant; the industrial computer is equipped with offline programming software for processing.

[0025] Further, the jig is a special-shaped jig without a tip at the end.

[0026] For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings. Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the system for calibrating the tool center point of the robot provided by the embodiment of the present application;

[0028] Figure 2 It is a schematic diagram of the robot coordinate system;

[0029] Figure 3 It is a flowchart of the method for calibrating the tool center point of the robot provided by the embodiment of the present application.

[0030] In the figure: 1 - robot; 2 - fixed calibration needle; 3 - jig; 4 - robot control module; 5 - manual teaching pendant; 6 - industrial computer. Detailed Embodiment

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] In the description of the present invention, it should also be noted that unless otherwise clearly defined and limited, the terms "set", "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or a connection through an intermediate medium. It can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0033] Please refer to Figure 1, A system for calibrating the robot tool center point based on an offline programming software, which is used to implement the method of the robot tool center point, includes: a robot 1, a fixed calibration needle 2, a fixture 3, a robot control module 4, a manual teaching pendant 5, and an industrial control computer 6.

[0034] The robot 1 includes a fixedly installed robot base; the robot base is provided with a base coordinate system O o , and the robot end is provided with an end coordinate system O a .

[0035] The fixed calibration needle 2 is fixedly arranged on the robot working platform, and the fixed calibration needle 2 is fixedly arranged relative to the robot base; a workpiece coordinate system O is set at the fixed calibration needle 2 p .

[0036] The fixture 3 is installed at the end of the robot 1, and a tool coordinate system O is set at the fixture b . Specifically, in the embodiment of the present application, the fixture is a special-shaped fixture without an end tip.

[0037] The robot control module 4 is signal-connected to the robot 1; based on the robot control system and algorithm, in the embodiment of the present application, the robot control module 4 is used to calculate the workpiece coordinate system of the fixed calibration needle 2.

[0038] The manual teaching pendant 5 is signal-connected to the robot control system, and is used to control the robot to drive the fixture to move; and generate a teaching program.

[0039] The industrial control computer 6 is signal-connected to the manual teaching pendant 5; the industrial control computer 6 is equipped with offline programming software and can import the algorithm model of the robot 1 with D-H parameters for data processing.

[0040] In the process of constructing the coordinate systems of each component of the robot, first construct the robot base coordinate system O o ; the robot end coordinate system O a is obtained according to the construction principle of the D-H coordinate system of the robot base coordinate, that is, as long as the rotation joint values of each axis of the robot body are known to form a robot forward kinematics matrix equation, the robot end coordinate system O can be calculated by the operation of the industrial control computer equipped with offline programming software a , and the principle is as follows:

[0041] Please refer to Figure 2 , determine the kinematic model of the robot by the D-H parameter method and establish a link coordinate system. The robot D-H parameter table is as follows,

[0042] joint <![CDATA[α i > <![CDATA[a i > <![CDATA[θ i > <![CDATA[d i > 1 <![CDATA[α 1 = 90]]> 0 <![CDATA[θ 1 > <![CDATA[d 1 > 2 0 <![CDATA[a 2 > <![CDATA[θ 2 > 0 3 0 <![CDATA[a 3 > <![CDATA[θ 3 > 0 4 <![CDATA[α 4 = 90]]> 0 <![CDATA[θ 4 > <![CDATA[d 4 > 5 <![CDATA[α 5 = -90]]> 0 <![CDATA[θ 5 > <![CDATA[d 5 > 6 0 0 <![CDATA[θ 6 > <![CDATA[d 6 >

[0043] Among them, α i is the rotation of the X axis; a iTranslation along the X-axis; θ i is the rotation about the Z-axis of the joint variable, d i is the translation along the Z-axis, where a i and d i are known constants.

[0044] Thus, the homogeneous transformation matrix of the robot coordinate system i in the coordinate system i-1 can be established:

[0045]

[0046]

[0047] Substitute the D-H parameters into the above homogeneous transformation matrix to obtain the transformation matrices of all adjacent coordinate systems:

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] The transformation matrix from the end coordinate system to the base coordinate system:

[0055]

[0056] Input the six joint angles θ i , and obtain the transformation matrix T of the end coordinates in the base coordinate system.

[0057] Let:

[0058]

[0059] The upper left 3x3 matrix of T is the rotation matrix, which is converted through the Rodrigues transformation, and the rotation matrix is converted into the rotation vector [rx, ry, rz]; the upper right 3x1 of T is the spatial position [x, y, z], and the six elements of the coordinates of the origin of the robot end coordinate system [x, y, z, rx, ry, rz] are obtained.

[0060] In this way, the forward kinematic calculation of the robot coordinate system is completed.

[0061] The tool coordinate system O of the fixture installed at the end of the robot b can be obtained through homogeneous transformation rotation and translation:

[0062]

[0063] Through the end - effector coordinate system O of the robot a First, rotate around the Za axis Rotate around the Ya axis Rotate around the Xa axis Then translate by t to obtain the tool coordinate system O b .

[0064] Similarly, the coordinates of the workpiece coordinate system O p are obtained by homogeneous transformation rotation and translation calculations from the base coordinate system O o .

[0065] Based on the above principles, combined with Figures 1-3 , a method for calibrating the robot tool center point based on an offline programming software provided in an embodiment of the present application will be elaborated in detail.

[0066] Step S1, establish the robot base coordinate system O o .

[0067] Step S2, calibrate the workpiece coordinate system O p .

[0068] Step S21, install a fixed calibration pin on the robot working platform. The fixed calibration pin is fixed relative to the robot base, and establish the initial workpiece coordinate system O p .

[0069] Step S22, use the three - point method to calibrate the workpiece coordinate system O p .

[0070] Specifically, control the robot through the manual teaching pendant to read the coordinate values of 3 teaching points on the fixed calibration pin. Usually, the first teaching point is taken as the origin of the workpiece coordinate system; the second teaching point is taken as a point on the X - axis. The line connecting the first teaching point and the second teaching point is the X - axis, and the direction is the positive X - direction; the third teaching point is in the positive Y - axis region. Then, through the robot control module, calculate the corresponding workpiece coordinate system O p , and generate the X, Y, Z, U, V, W values of the workpiece coordinate system O p on the manual teaching pendant.

[0071] Step S3, import the robot algorithm model with D - H parameters that has been set in the industrial control computer; enter the X, Y, Z, U, V, W values of the generated workpiece coordinate system O p into the industrial control computer. At this time, the industrial control computer generates the position and attitude of the corresponding workpiece coordinate system O p .

[0072] Step S4, install a jig at the end joint of the robot, mark the preset point, which is the TCP of the jig to be calibrated; move each joint of the robot through the manual teaching pendant to make the preset point coincide with the tip point of the fixed calibration pin. At this time, the TCP of the jig to be calibrated coincides with the workpiece coordinate system O p coincides.

[0073] Step S5, read the joint values of each joint of the robot and the rotational position values of each axis from the manual teaching pendant, and input them into the industrial control computer to build a 3D environment; at this time, the joint positions of the robot in reality are consistent with the joint positions in the virtual environment.

[0074] Step S6, set the value of the TCP of the jig in the virtual environment of the industrial control computer offline programming software; the industrial control computer performs the forward kinematics calculation of the robot D-H coordinate system in the virtual environment to obtain the corresponding TCP value.

[0075] Step S7,; read the TCP value calculated in the industrial control computer, and input the TCP value into the manual teaching pendant. The calibration of the TCP of the tool coordinate system is completed.

[0076] Compared with the prior art, a method and system for calibrating the tool center point of a robot based on offline programming software provided by the embodiments of the present application, by utilizing the virtual reproducibility of the offline programming software, and visually reading the corresponding coordinate values, while ensuring the calibration accuracy, can achieve the rapid calibration of the TCP of the jig, reduce the operation time cycle and the debugging cost of the robot. At the same time, for special-shaped jigs without end tips, there are not too many restrictions on the space around the coordinates during calibration, and there is no need to make corresponding special calibration pins for calibration, avoiding the repeated clamping of the robot jig and the corresponding assembly errors. In addition, the offline programming can be downloaded on an external computer and can be used temporarily when calibration is required, which is simple and fast.

[0077] The above embodiments only represent one or several implementation manners of the present invention, and the description is relatively specific and detailed, but it cannot be understood as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and the present invention also intends to include these modifications and improvements.

Claims

1. A method for calibrating the robot tool center point based on offline programming software, characterized in that, it includes the following steps: Step S1: Establish a robot base coordinate system; Step S2: Set a workpiece coordinate system at the fixed calibration pin, calibrate the workpiece coordinate system, and obtain the X, Y, Z, U, V, and W values of the workpiece coordinate system; Step S3: Enter the X, Y, Z, U, V, and W values of the generated workpiece coordinate system into the industrial control computer. At this time, the industrial control computer generates the corresponding position and attitude of the workpiece coordinate system; Step S4: Install a jig at the end joint of the robot, mark a preset point, which is the jig TCP to be calibrated; Move each joint of the robot to make the jig TCP to be calibrated coincide with the tip point of the fixed calibration pin; Step S5: Read the joint values of the robot and the rotational position values of each axis, and input them into the industrial control computer; Step S6: Set the value of the jig TCP in the virtual environment of the offline programming software of the industrial control computer; Perform the forward kinematics calculation of the robot D-H coordinate system in the virtual environment of the industrial control computer to obtain the value of the corresponding tool coordinate system TCP; Step S7: Enter the value of TCP into the manual teaching pendant, and the calibration of the tool coordinate system TCP is completed.

2. A method for calibrating the robot tool center point based on offline programming software according to claim 1, characterized in that: In step S2, the coordinates of the workpiece coordinate system are obtained by homogeneous transformation rotation and translation calculation of the base coordinate system.

3. A method for calibrating the robot tool center point based on offline programming software according to claim 2, characterized in that: In step S3, the three-point marking method is used to calibrate the workpiece coordinate system. The robot control system calculates the workpiece coordinate system and generates the X, Y, Z, U, V, and W values of the workpiece coordinate system in the manual teaching pendant.

4. A system for calibrating the robot tool center point based on offline programming software, characterized in that, used to implement the method for calibrating the robot tool center point based on offline programming software according to any one of claims 1-3, including: a robot, a fixed calibration pin, a jig, a robot control module, a manual teaching pendant, and an industrial control computer; The robot includes a fixedly installed robot base; The fixed calibration pin is fixedly arranged relative to the robot base; The jig is installed at the end of the robot; The robot control module is signal-connected to the robot; The robot control module is based on the robot control system and algorithm, and is used to calculate the workpiece coordinate system of the fixed calibration pin; The manual teaching pendant is signal-connected to the robot control system and is used to control the robot to drive the jig to move; The industrial control computer is signal-connected to the manual teaching pendant; The industrial control computer is equipped with offline programming software for data processing.

5. A system for calibrating the robot tool center point based on offline programming software according to claim 4, characterized in that: The jig is a special-shaped jig without a tip at the end.

Images