Industrial robot workpiece coordinate system rapid calibration device and method

Abstract

The invention belongs to the field of advanced manufacturing of industrial robots, and particularly relates to a quick calibration device and method for a workpiece coordinate system of an industrial robot. Comprising a rapid calibration assembly fixed at the tail end of the robot, and the rapid calibration assembly comprises an industrial robot tail end flange (1), an adapter (2), an air buoyancy force control device (3), a tool holder (4) and a calibration probe (7). One end of the industrial robot tail end flange (1) is fixedly connected with the tail end of a robot, the other end of the industrial robot tail end flange (1) is connected with one end of the adapter (2), the other end of the adapter (2) is fixedly connected with the fixed end of the air buoyancy force control device (3), and the movable end of the air buoyancy force control device (3) is connected with the tool holder (4). And the calibration probe (7) is positioned and clamped through the tool holder (4). Compared with a three-feature-point calibration method, the multi-feature-point calibration method provided by the invention has a redundancy advantage in data, and through construction of a covariance matrix and singular value matrix decomposition, single-point measurement noise is effectively suppressed, and the overall calibration precision is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of advanced manufacturing of industrial robots, and particularly relates to a device and method for quickly calibrating a workpiece coordinate system of an industrial robot. BACKGROUND

[0002] In the application scenarios of industrial robots, workpiece coordinate system calibration is the core basis for achieving precise work. For example, in typical tasks such as hole making, assembly, polishing, and painting, the robot end effector needs to plan a trajectory according to the actual position and attitude of the workpiece. Due to the mechanical tolerances in the installation of the workpiece on the fixture, and the possible slight deviation of the processing reference of different batches of workpieces, it is difficult to meet the actual work precision requirements relying only on the theoretical model. By calibrating the workpiece coordinate system, an accurate pose mapping relationship between the robot base coordinate system and the workpiece local coordinate system can be established, so that the robot motion instructions can be dynamically adapted to the actual workpiece position, significantly improving the work precision and consistency. In flexible manufacturing systems, frequent production changes result in an increase in the variety and size of workpieces, and fast and adaptive coordinate system calibration technology becomes a key to shortening the production line debugging cycle and improving equipment utilization. In addition, in the fields of aerospace and automobile manufacturing, the processing of complex curved surface workpieces or large size structural parts often requires multiple robots to work cooperatively, and high precision workpiece coordinate system calibration can ensure the spatial synchronization of multi-robot cooperation and avoid interference or processing defects caused by accumulated errors. With the evolution towards intelligentization and high-mix production, higher requirements are put forward for the efficiency, robustness and automation level of workpiece coordinate system calibration.

[0003] The current mainstream workpiece coordinate system calibration method in the field of industrial robots still has significant defects: first, the traditional three-point calibration method relies on manual control of the robot end tool to contact the workpiece feature points (such as three-point plane), and the calibration accuracy is easily affected by human operation errors, and the adaptability to non-planar workpieces is poor; second, the contact type calibration tool (such as a mechanical probe) is usually designed with a fixed size, which is difficult to match end effectors of different lengths or structures, and the calibration parameters need to be adjusted repeatedly when replacing the tool, which seriously restricts the production change efficiency; third, existing algorithms are mostly based on least squares or geometric analytical methods, which require strict compliance with the number of feature points (such as three-point method requiring coplanar and non-collinear), and are sensitive to point data noise, which may lead to matrix solution failure when the feature points are unevenly distributed or have measurement errors; fourth, there is a lack of real-time feedback mechanism in the calibration process, and the contact state of the tool and the workpiece depends on visual judgment, which may damage precision components due to collision overload. For example, in the public patent CN202310160278.4, although a calibration method based on visual guidance is proposed, it requires additional deployment of camera equipment and is susceptible to environmental light interference, which makes it difficult to be stably applied in industrial sites with oil stains, dust, etc. The above problems have become a common technical bottleneck restricting the intelligent upgrading of robots. SUMMARY

[0004] The purpose of the present application: the present application aims to solve the technical problems of low calibration accuracy, lack of contact feedback and serious mechanical damage caused by rigid contact in the traditional workpiece coordinate system calibration method, and the purpose of the present application is to provide a kind of industrial robot workpiece coordinate system fast calibration device and method.

[0005] The content of the technical scheme of the present application: according to the first aspect of the present application, an industrial robot workpiece coordinate system fast calibration device is provided, which comprises a fast calibration assembly fixed to the end of the robot, the fast calibration assembly component includes industrial robot end flange (1), adapter seat (2), gas floating force control device (3), tool holder (4), calibration probe (7);One end of the industrial robot end flange (1) is fixedly connected with the end of the robot, the other end is connected with one end of the adapter seat (2), the other end of the adapter seat (2) is fixedly connected with the fixed end of the gas floating force control device (3), the movable end of the gas floating force control device (3) is connected with the tool holder (4), and the calibration probe (7) is positioned and clamped by the tool holder (4). Contact pressure sensing is carried out through the calibration probe (7), so as to judge whether the probe (7) is in contact with the workpiece.

[0006] In one possible embodiment, the calibration probe (7) is connected with the tool holder (4) through a positioning pin.

[0007] According to the second aspect of the present application, an industrial robot workpiece coordinate system fast calibration method is provided, which adopts the above-mentioned industrial robot workpiece coordinate system fast calibration device, and comprises the following steps: Step 1: establish the matrix transformation equation of robot base coordinate system and workpiece coordinate system feature points; Step 2: move the calibration probe (7) to the pre-defined multiple feature points on the workpiece, observe the probe contact force feedback data, when the contact force data is greater than zero, record the robot probe tool Cartesian coordinate data at this time, and traverse all feature points; Step 3: according to the coordinate data of each feature point in step 2, data preprocessing calculation is carried out; Step 4: according to the coordinate data after preprocessing in step 3, the rotation matrix of the matrix transformation equation in step 1 is solved; Step 5: based on the coordinate data after preprocessing in step 3 and the rotation matrix solved in step 4, the translation vector of the matrix transformation equation in step 1 is solved; Step 6: based on the rotation matrix solved in step 4 and the translation vector solved in step 5, the transformation matrix of robot base coordinate system and workpiece coordinate system is constructed according to the principle of homogeneous coordinate matrix.

[0008] In one possible embodiment, in step 1, the matrix transformation equation is specifically as follows: Assume the transformation matrix from the workpiece coordinate system to the base coordinate system is ,and Then the following relationship is satisfied:

[0009] in Let be a rotation matrix. The translation vector represents the coordinates of the contact point in the robot's base coordinate system. Meanwhile, based on the workpiece model, the theoretical coordinates of the feature points in the workpiece coordinate system are known. , It is a natural number greater than or equal to 4. This is the matrix transpose symbol.

[0010] In one possible embodiment, the specific process of data preprocessing in step 3 includes: First, calculate the center point: ,

[0011] in, The center point of the contact point coordinate data in the robot's base coordinate system. These are the theoretical coordinate data points of the feature points in the workpiece coordinate system.

[0012] To eliminate the influence of translation components and retain only rotation relationships, the point information needs to be decentralized according to the following formula: ,

[0013] in, for Preprocessed data, for Preprocessed data.

[0014] In one possible embodiment, step 4 specifically includes the following steps: To obtain the rotation matrix with optimal accuracy, the following error function was constructed:

[0015] The optimal rotation matrix is ​​solved by minimizing the error function. The calculation process is as follows: First, construct the covariance matrix. as follows:

[0016] Next, the covariance matrix Perform singular value decomposition (SVD), assuming:

[0017] where, , are the covariance orthogonal matrix decomposed, singular value diagonal matrix.

[0018] Then, calculate the rotation matrix:

[0019] In order to ensure that the rotation matrix is a right-handed coordinate system, the constraint condition is: if the matrix determinant value is -1, it needs to be corrected to .

[0020] In one possible embodiment, the step 5 specifically includes the following steps: According to the rotation matrix , the translation vector can be solved by using the center point coordinate difference as follows: .

[0021] In one possible embodiment, in the step 6, specifically includes the following steps: Construct the homogeneous transformation matrix of the workpiece coordinate system to the base coordinate system:

[0022] According to the homogeneous coordinate transformation matrix , the workpiece coordinate system can be calibrated, and the conversion of coordinate data between the robot base coordinate system and the workpiece coordinate system can be realized.

[0023] Compared with the prior art, the beneficial effects of the present application include a) Precision improvement: the multi-feature point calibration method proposed in the present application has the advantage of data redundancy compared with the three-feature point calibration method. By constructing the covariance matrix and singular value matrix decomposition, single-point measurement noise is effectively suppressed, and the overall calibration precision is improved.

[0024] b) Operation safety improvement: the compliant control of contact force is realized by the air floating force control device, and the contact state is fed back in real time by the air floating device extension distance, which can effectively avoid mechanical damage such as punch, and improve the calibration safety.

[0025] c) Efficiency improvement: the fast mechanism is adopted, which can realize the quick replacement of calibration tools and machining tools, save tool replacement time, and improve operation efficiency.

[0026] d) The calibration algorithm is flexible and stable: a multi-feature point workpiece coordinate system calibration method with higher precision is proposed, and the transformation matrix of the workpiece coordinate system and the base coordinate system can be automatically obtained through matrix operation. In the later stage, the number of feature points can be expanded to further improve the precision and reliability of the calibration algorithm. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic structural diagram of an industrial robot workpiece coordinate system rapid calibration device according to a preferred embodiment of the present application; Figure 2 is a flowchart of an industrial robot workpiece coordinate system rapid calibration method according to a preferred embodiment of the present application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments.

[0029] In the specification, claims and drawings of the present application, the terms "first", "second", "third", "fourth" and the like are used to distinguish similar objects, not necessarily to describe a particular order or sequence. It should be understood that the data thus used can be interchanged, if appropriate, so that the embodiments described herein can be implemented in other than the order illustrated or described herein, and furthermore, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or apparatus that includes a series of steps or units need not be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to such processes, methods, products or apparatuses.

[0030] Embodiment 1 According to Figure 1 As shown in the figure, an industrial robot workpiece coordinate system rapid calibration device includes a rapid calibration assembly fixed to the end of the robot, the rapid calibration assembly includes an industrial robot end flange (1), an adapter seat (2), a gas floating force control device (3), a tool holder (4), and a calibration probe (7). One end of the industrial robot end flange (1) is fixedly connected with the end of the robot, and the other end is connected with one end of the adapter seat (2). The other end of the adapter seat (2) is fixedly connected with the fixed end of the gas floating force control device (3). The movable end of the gas floating force control device (3) is connected with the tool holder (4). The calibration probe (7) is positioned and clamped by the tool holder (4). Contact pressure sensing is performed by the calibration probe (7) to determine whether the probe (7) is in contact with the workpiece. The calibration probe (7) is connected with the tool holder (4) through a positioning pin.

[0031] Embodiment 2 As Figure 2 shown, a fast calibration method of workpiece coordinate system of industrial robot is proposed, which adopts the fast calibration device of workpiece coordinate system of industrial robot, and includes the following steps: (1) Control the robot to approach the six predefined feature points on the workpiece once, and record the coordinates of each point in the robot base coordinate system at the contact time according to the contact state of the probe and the feature points fed back by the air floating extension distance.

[0032] (2) The coordinate matrix of the predefined feature points in the workpiece coordinate system is

[0033] The coordinate matrix of the feature points in the robot base coordinate system is

[0034] (3) Data preprocessing: a) Calculate the center point; ,

[0035] b) Decentering processing.

[0036]

[0037]

[0038] (4) Matrix calculation: a) Construct the covariance matrix;

[0039] b) Singular value decomposition calculation is performed on the covariance matrix.

[0040]

[0041]

[0042] c) Calculate the rotation matrix

[0043] d) Calculate the translation vector

[0044] (5) According to the rotation matrix and the translation vector, the homogeneous coordinate transformation matrix of the robot coordinate system and the workpiece coordinate system is constructed.

[0045] ​​

[0046] The above examples are only used to illustrate the technical solutions of the present application, but not to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those ordinarily skilled in the art should understand: the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A rapid calibration device for the workpiece coordinate system of an industrial robot, characterized in that, The system includes a rapid calibration assembly fixed to the end of a robot. The rapid calibration assembly includes an industrial robot end flange (1), an adapter (2), an air buoyancy force control device (3), a tool holder (4), and a calibration probe (7). One end of the industrial robot end flange (1) is fixedly connected to the end of the robot, and the other end is connected to one end of the adapter (2). The other end of the adapter (2) is fixedly connected to the fixed end of the air buoyancy force control device (3). The movable end of the air buoyancy force control device (3) is connected to the tool holder (4). The calibration probe (7) is positioned and held by the tool holder (4).

2. The rapid calibration device for the workpiece coordinate system of an industrial robot according to claim 1, characterized in that, The calibration probe (7) is connected to the tool holder (4) via a positioning pin.

3. A method for rapid calibration of the workpiece coordinate system of an industrial robot, employing the rapid calibration device for the workpiece coordinate system of an industrial robot as described in any one of claims 1-2, characterized in that, Includes the following steps: Step 1: Establish the transformation equations of the feature point matrix between the robot base coordinate system and the workpiece coordinate system; Step 2: Move the calibration probe (7) to multiple predefined feature points on the workpiece, observe the probe contact force feedback data, and when the contact force data is greater than zero, record the Cartesian coordinate data of the robot probe tool at this time, and traverse all feature points; Step 3: Perform data preprocessing calculations based on the coordinate data of each feature point in Step 2; Step 4: Solve for the rotation matrix of the matrix transformation equation in Step 1 based on the preprocessed coordinate data in Step 3; Step 5: Based on the preprocessed coordinate data in Step 3 and the rotation matrix obtained in Step 4, solve for the translation vector of the matrix transformation equation in Step 1. Step 6: Based on the rotation matrix obtained in Step 4 and the translation vector obtained in Step 5, construct the transformation matrix between the robot base coordinate system and the workpiece coordinate system according to the principle of homogeneous coordinate transformation matrix.

4. The method for rapid calibration of the workpiece coordinate system of an industrial robot according to claim 3, characterized in that, In step 1, the matrix transformation equation is as follows: Assume the transformation matrix from the workpiece coordinate system to the base coordinate system is ,and Then the following relationship is satisfied: in For rotation matrix, The translation vector represents the coordinates of the contact point in the robot's base coordinate system. Meanwhile, based on the workpiece model, the theoretical coordinates of the feature points in the workpiece coordinate system are known. , It is a natural number greater than or equal to 4. This is the matrix transpose symbol.

5. The method for rapid calibration of the workpiece coordinate system of an industrial robot according to claim 3, characterized in that, In step 3, the specific process of data preprocessing includes: First, calculate the center point: ， in, The center point of the contact point coordinate data in the robot's base coordinate system. These are the theoretical coordinate data centers for feature points in the workpiece coordinate system. To eliminate the influence of translation components and retain only rotation relationships, the point information needs to be decentralized according to the following formula: ， in, for Preprocessed data, for Preprocessed data.

6. The method for rapid calibration of the workpiece coordinate system of an industrial robot according to claim 3, characterized in that, Step 4 specifically includes the following steps: To obtain the rotation matrix with optimal accuracy, the following error function was constructed: The optimal rotation matrix is ​​solved by minimizing the error function. The calculation process is as follows: First, construct the covariance matrix. as follows: Next, the covariance matrix Perform singular value decomposition (SVD), assuming: in, , All are covariance The orthogonal matrix obtained by decomposition It is a singular value diagonal matrix; Then, calculate the rotation matrix: To ensure the rotation matrix is ​​in a right-handed coordinate system, the constraint is: if the matrix The determinant value is -1, and it needs to be corrected to... 。 7. The method for rapid calibration of the workpiece coordinate system of an industrial robot according to claim 3, characterized in that, Step 5 specifically includes the following steps: Based on the obtained rotation matrix The translation vector can be solved using the difference in the coordinates of the center points. as follows: 。 8. The method for rapid calibration of the workpiece coordinate system of an industrial robot according to claim 3, characterized in that, Step 6 specifically includes the following steps: Construct the homogeneous transformation matrix from the workpiece coordinate system to the base coordinate system: 。

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