A dual-manipulator base coordinate system calibration and coaxial positioning method

Abstract

The present invention discloses a method for calibration and coaxial positioning of a dual-manipulator base coordinate system, wherein the dual-manipulator comprises a first manipulator and a second manipulator, and the method comprises the following steps: S1: installing the same calibration device on the two manipulators respectively, and fixing the calibration workpiece on a workbench; S2: moving the first manipulator to the workbench, and aligning the calibration device with the calibration workpiece, and obtaining the posture information of the end of the first manipulator at this time; using the same method to obtain the posture information of the end of the second manipulator; S3: repeating step S2 for multiple times, and then processing the data obtained in step S2 to obtain a calibration matrix; S4: changing the position of the calibration workpiece, repeating steps S2-S4, until the number of changes reaches a preset number of times, and obtaining a final calibration matrix; S5: coaxially positioning the dual manipulators according to the final calibration matrix. The present invention can realize rapid and accurate positioning and calibration of the dual manipulators, and further improve the stability and reliability of the operation.

Description

Technical Field

[0001] The present invention relates to the field of robot technology, and in particular to a dual-manipulator base coordinate system calibration and coaxial positioning method. Background Art

[0002] In the task of tightening the contact network bolts, one robot arm is usually required to tighten the bolts and the other robot arm is required to fix the nuts. Traditionally, in order to achieve this task, a visual inspection device is needed to estimate the position of the bolts and nuts. However, in actual operation, the diversity of the nuts' shapes and the irregularity of their surface features make it difficult to extract their features, which makes it difficult to accurately identify their positions, increasing the complexity and uncertainty of the operation.

[0003] In addition, in unstructured application scenarios such as bolt tightening, the installation position of the dual robotic arms may change with task requirements. However, the base coordinate system relationship of the traditional dual robotic arms usually needs to be obtained through drawings and manual measurement. Overly complicated calibration operations at the work site will increase the operation time; and manual measurement requires accurate dimensional parameters of the robotic arms and the dimensions between the fixed bases. Due to the large number of measurement steps, the measurement errors are superimposed in multiple operations, resulting in large measurement errors. Summary of the invention

[0004] In view of the above problems, the present invention aims to provide a dual-manipulator base coordinate system calibration and coaxial positioning method.

[0005] The technical solution of the present invention is as follows:

[0006] A dual-manipulator base coordinate system calibration and coaxial positioning method, the dual-manipulator comprises a first manipulator and a second manipulator, the method comprising the following steps:

[0007] S1: Install the same calibration device on the first robot arm and the second robot arm respectively, and fix the calibration workpiece matching the calibration device on the workbench;

[0008] S2: moving the No. 1 robot arm to the workbench, and aligning the calibration device on the No. 1 robot arm with the calibration workpiece on the workbench, and obtaining the posture information of the end of the No. 1 robot arm at this time;

[0009] Move the second robot arm to the workbench, and align the calibration device on the second robot arm with the calibration workpiece on the workbench to obtain the posture information of the end of the second robot arm at this time;

[0010] S3: Repeat step S2 multiple times, and then process the data obtained in step S2 to obtain a calibration matrix for describing the conversion relationship between the two robot arm base coordinate systems;

[0011] S4: changing the position of the calibration workpiece, repeating steps S2-S4 until the number of changes reaches a preset number, and obtaining a final calibration matrix;

[0012] S5: Coaxially positioning the dual robotic arms according to the final calibration matrix.

[0013] Preferably, in step S1, the calibration device comprises a flange plate 1 and an alignment pin arranged on the flange plate 1, the calibration workpiece comprises a flange plate 2 and a calibration column arranged on the flange plate 2, and the calibration column is provided with an alignment pin hole for accommodating the alignment pin.

[0014] Preferably, three alignment pins and three calibration columns are provided, two of which are symmetrically arranged about the center of the flange, and the other is on the same radius as the two of them and is arranged at the midpoint of the semicircle where the two of them are located.

[0015] Preferably, the depth of the alignment pin hole is smaller than the length of the alignment pin.

[0016] Preferably, in step S3, when processing the data obtained in step S2, the following sub-steps are included:

[0017] S31: Eliminate outliers and perform data averaging to obtain a data set;

[0018] S32: Convert the translation vector and rotation vector in the data set into a homogeneous matrix;

[0019] S33: According to the homogeneous matrix of the first robot arm and the homogeneous matrix of the second robot arm, a calibration matrix for describing the transformation relationship between the base coordinate systems of the two robot arms is obtained.

[0020] Preferably, in step S32, the rotation vector is converted into a rotation matrix using the Rodriguez rotation formula, and the Rodriguez rotation formula is:

[0021]

[0022] Where: is the rotation matrix; θ is the rotation angle; u x 、u y 、u z are the normalized rotation axes of the x, y, and z axes, respectively, (u x ,u y ,u z ) is the axis of rotation; are the average values ​​of the rotation vectors rx, ry, and rz respectively;

[0023] The homogeneous matrix obtained according to the translation vector and the rotation matrix is:

[0024]

[0025] Where: is a homogeneous matrix; x, y, z are the translation vectors of the x, y, and z axes of the tool coordinate system in the robot base coordinate system.

[0026] Preferably, in step S33, the calibration matrix used to describe the conversion relationship between the two robot base coordinate systems is:

[0027]

[0028] Where: is the calibration matrix used to describe the transformation relationship between the two robot base coordinate systems; is the homogeneous matrix of robot arm No. 1; is a 4×4 identity matrix; is the homogeneous matrix of the second robot arm The inverse matrix of .

[0029] Preferably, in step S4, the final calibration matrix is ​​obtained by averaging the calibration matrices obtained multiple times for describing the conversion relationship between the two robot arm base coordinate systems.

[0030] Preferably, step S5 specifically includes the following sub-steps:

[0031] S51: Move the robot arm No. 1 to the target position;

[0032] S52: Rotate the end posture of the first robot arm 180° around the y axis and translate the end posture of the first robot arm by a distance z_move in the negative direction of the z axis of the rotated coordinate system to obtain a symmetrical posture of the first robot arm on the same axis;

[0033] S53: Obtaining an expected positioning posture of the second robotic arm being coaxial with the first robotic arm according to the final calibration matrix.

[0034] Preferably, in step S53, the expected positioning posture of the second robotic arm being coaxial with the first robotic arm is obtained by the following formula:

[0035]

[0036]

[0037] Where: is the expected positioning posture of the second robot arm coaxial with the first robot arm; is the final calibration matrix; is the homogeneous matrix of robot arm No. 1 at the target position; H rotation_y_180is a homogeneous matrix rotated 180° around the y axis; H translate_z is the homogeneous matrix of the translation z along the z-axis; z_move is the straight-line distance from the end of the second robot arm to the end of the first robot arm in the z-axis direction.

[0038] The beneficial effects of the present invention are:

[0039] The present invention calculates the expected position and posture of another robotic arm through the position and posture of one robotic arm, thereby achieving collaborative operation between the two, making the movements between the robotic arms more coordinated and accurate. Compared with the traditional method, the present invention no longer relies on the accurate recognition of the nut position by the visual detection device, but derives the nut position through the position and posture information between the robotic arms, thereby avoiding the dependence on the nut features; this not only greatly simplifies the difficulty of the task, improves the accuracy and efficiency of the operation, but also reduces the dependence on the visual system and the failure rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0041] Figure 1 It is a schematic diagram of the process of the dual-manipulator base coordinate system calibration and coaxial positioning method of the present invention;

[0042] Figure 2 A schematic diagram of the installation position of a calibration device and a calibration workpiece in a specific embodiment;

[0043] Figure 3 It is a schematic diagram of the alignment position of the first robot arm in a specific embodiment;

[0044] Figure 4 It is a schematic diagram of the alignment position of the second robot arm in a specific embodiment;

[0045] Figure 5 It is a schematic diagram of the coaxial alignment coordinate relationship of the dual-manipulator base coordinate system calibration and coaxial positioning method of the present invention. DETAILED DESCRIPTION

[0046] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, in the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those generally understood by those of ordinary skill in the art to which this application belongs. The words "including" or "comprising" and the like used in the disclosure of the present invention mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0047] like Figure 1-5 As shown, the present invention provides a dual-manipulator base coordinate system calibration and coaxial positioning method, the dual-manipulator includes a first manipulator and a second manipulator, and the method includes the following steps:

[0048] S1: Install the same calibration device on the No. 1 robot arm and the No. 2 robot arm respectively, and fix the calibration workpiece matching the calibration device on the workbench.

[0049] In a specific embodiment, the calibration device includes a flange plate 1 and an alignment pin disposed on the flange plate 1, and the calibration workpiece includes a flange plate 2 and a calibration column disposed on the flange plate 2, and the calibration column is provided with an alignment pin hole for accommodating the alignment pin. When using this embodiment, the flange plate 1 is fixed on the robot arm, and the flange plate 2 is fixed on the workbench.

[0050] Optionally, three alignment pins and three calibration columns are provided, two of which are symmetrically arranged about the center of the flange, and the other is on the same radius as the two of them and is arranged at the midpoint of the semicircle where the two of them are located.

[0051] Optionally, the depth of the alignment pin hole is less than the length of the alignment pin. In this embodiment, the depth of the alignment pin hole of the calibration workpiece is less than the length of the alignment pin of the calibration device, so the three alignment pins of the calibration device must be aligned to the bottom of the alignment pin hole in sequence. This process accurately controls and fine-tunes the robotic arm to ensure that each alignment pin is completely in contact with the bottom of the alignment pin hole, thereby achieving precise alignment of the calibration device and the calibration workpiece. During the adjustment process, the position of each alignment pin should be carefully observed, and the robotic arm should be moved step by step until all alignment pins are completely aligned with the bottom of the alignment pin hole, and their end posture information is read.

[0052] In a specific embodiment, three cylindrical alignment pins with a diameter of 6 mm and a height of 20 mm are provided on the flange. The center position of these alignment pins is located at any intersection of the extension line of the connection line between the center of the flange and the center of the bolt hole and a circle with a diameter of 72 mm centered on the center of the flange. The center position of the alignment pin hole of the corresponding calibration workpiece is mirror-symmetrical to the center position of the alignment pin. In other words, the position of the alignment pin hole on the calibration workpiece is exactly the same as the position of the alignment pin on the calibration device. The inner diameter of the alignment pin hole is 6.5 mm, leaving a tolerance of 0.5 mm, so as to avoid the calibration workpiece and the calibration device from being fully matched due to dimensional errors. The outer diameter of the alignment pin hole is 8 mm and the height is 15 mm. When the three alignment pins of the calibration device are fully inserted into the alignment pin holes at the corresponding positions, the relative position relationship between the calibration device and the calibration workpiece will be fixed.

[0053] It should be noted that the calibration device and calibration workpiece of the above embodiment have a simple structural design, simple registration operation, and a standard flange installation method suitable for a variety of industrial robotic arms, which can quickly obtain and collect a set of fixed postures of the dual robotic arms, thereby achieving fast and accurate calibration in an industrial environment. However, in addition to the calibration device and calibration workpiece used in the above embodiment, other calibration devices and calibration workpieces in the prior art that can fix the relative position relationship between the two can also be applied to the present invention.

[0054] S2: moving the No. 1 robot arm to the workbench, and aligning the calibration device on the No. 1 robot arm with the calibration workpiece on the workbench, and obtaining the posture information of the end of the No. 1 robot arm at this time;

[0055] Move the No. 2 robotic arm to the workbench, and align the calibration device on the No. 2 robotic arm with the calibration workpiece on the workbench to obtain the posture information of the end of the No. 2 robotic arm at this time.

[0056] It should be noted that in this step, the posture information of the end of the No. 1 robotic arm can be obtained first, and then the No. 1 robotic arm can be moved away to obtain the posture information of the end of the No. 2 robotic arm; or the posture information of the end of the No. 2 robotic arm can be obtained first, and then the No. 2 robotic arm can be moved away to obtain the posture information of the end of the No. 1 robotic arm.

[0057] S3: Repeat step S2 multiple times, and then process the data obtained in step S2 to obtain a calibration matrix for describing the transformation relationship between the two robot arm base coordinate systems.

[0058] In this step, step S2 is repeated multiple times under the condition that the process calibration workpiece is fixed in position, which can ensure the accuracy and reliability of the data and ensure that the obtained calibration matrix can accurately describe the conversion relationship between the two robot base coordinate systems. Optionally, in this step, step S2 is repeated a total of 8 times.

[0059] In a specific embodiment, the processing of the data obtained in step S2 includes the following sub-steps:

[0060] S31: Eliminate outliers and perform data averaging to obtain a data set.

[0061] S32: Convert the translation vector and rotation vector in the data set into a homogeneous matrix.

[0062] In a specific embodiment, the rotation vector is converted into a rotation matrix using the Rodriguez rotation formula, and the Rodriguez rotation formula is:

[0063]

[0064]

[0065] Where: is the rotation matrix; θ is the rotation angle; u x 、u y 、u z are the normalized rotation axes of the x, y, and z axes, respectively, (u x ,u y ,u z ) is the axis of rotation; are the average values ​​of the rotation vectors rx, ry, and rz respectively;

[0066] The rotation matrix is ​​used to represent the posture of the tcp (tool coordinate system) under the base (manipulator base coordinate system);

[0067] The homogeneous matrix obtained according to the translation vector and the rotation matrix is:

[0068]

[0069] Where: is a homogeneous matrix; x, y, z are the translation vectors of the x, y, and z axes of the tool coordinate system in the robot base coordinate system.

[0070] S33: According to the homogeneous matrix of the first robot arm and the homogeneous matrix of the second robot arm, a calibration matrix for describing the transformation relationship between the base coordinate systems of the two robot arms is obtained.

[0071] In a specific embodiment, the calibration matrix obtained to describe the conversion relationship between the two robot base coordinate systems is:

[0072]

[0073] Where: is the calibration matrix used to describe the transformation relationship between the two robot base coordinate systems; is the homogeneous matrix of robot arm No. 1; is a 4×4 identity matrix; is the homogeneous matrix of the second robot arm The inverse matrix of .

[0074] S4: changing the position of the calibration workpiece, and repeating steps S2-S4 until the number of changes reaches a preset number, thereby obtaining a final calibration matrix.

[0075] In this step, by changing the position of the calibration workpiece multiple times and repeating steps S2-S4, the stability and reliability of the final calibration matrix calibration result can be improved. In a specific embodiment, the preset number of times is 6-8 times.

[0076] In a specific embodiment, the final calibration matrix is ​​obtained by averaging the calibration matrices obtained multiple times for describing the conversion relationship between the two robot arm base coordinate systems.

[0077] S5: coaxially positioning the dual robotic arms according to the final calibration matrix, specifically comprising the following sub-steps:

[0078] S51: Move the robot arm No. 1 to the target position.

[0079] S52: Rotate the end posture of the No. 1 robot arm 180° around the y-axis and translate the end posture of the No. 1 robot arm in the negative direction of the z-axis of the rotated coordinate system by a distance of z_move to obtain a symmetrical posture of the No. 1 robot arm on the same axis.

[0080] S53: According to the final calibration matrix, the expected positioning posture of the second robot arm coaxial with the first robot arm is obtained by the following formula:

[0081]

[0082] Where: is the expected positioning posture of the second robot arm coaxial with the first robot arm; is the final calibration matrix; is the homogeneous matrix of robot arm No. 1 at the target position; H rotation_y_180 is a homogeneous matrix rotated 180° around the y axis; H translate_z is the homogeneous matrix of the translation z along the z-axis; z_move is the straight-line distance from the end of the second robot arm to the end of the first robot arm in the z-axis direction.

[0083] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A dual-manipulator base coordinate system calibration and coaxial positioning method, characterized in that: The dual robotic arms include a first robotic arm and a second robotic arm, and the method includes the following steps: S1: Install the same calibration device on the first robot arm and the second robot arm respectively, and fix the calibration workpiece matching the calibration device on the workbench; S2: moving the No. 1 robot arm to the workbench, and aligning the calibration device on the No. 1 robot arm with the calibration workpiece on the workbench, and obtaining the posture information of the end of the No. 1 robot arm at this time; Move the second robot arm to the workbench, and align the calibration device on the second robot arm with the calibration workpiece on the workbench to obtain the posture information of the end of the second robot arm at this time; S3: Repeat step S2 multiple times, and then process the data obtained in step S2 to obtain a calibration matrix for describing the conversion relationship between the two robot arm base coordinate systems; S4: changing the position of the calibration workpiece, repeating steps S2-S4 until the number of changes reaches a preset number, and obtaining a final calibration matrix; S5: coaxially positioning the dual robotic arms according to the final calibration matrix, specifically comprising the following sub-steps: S51: Move the robot arm No. 1 to the target position; S52: Rotate the end posture of the first robot arm 180° around the y axis and translate the end posture of the first robot arm by a distance z_move in the negative direction of the z axis of the rotated coordinate system to obtain a symmetrical posture of the first robot arm on the same axis; S53: Obtain the expected positioning posture of the second robot arm coaxial with the first robot arm according to the final calibration matrix by the following formula: Where: is the expected positioning posture of the second robot arm coaxial with the first robot arm; is the final calibration matrix; is the homogeneous matrix of robot arm No. 1 at the target position; H rotation_y_180 is a homogeneous matrix rotated 180° around the y axis; H translate_z is the homogeneous matrix of the translation z along the z-axis; z_move is the straight-line distance from the end of the second robot arm to the end of the first robot arm in the z-axis direction.

2. The dual-manipulator base coordinate system calibration and coaxial positioning method according to claim 1, characterized in that: In step S1, the calibration device includes a flange plate 1 and an alignment pin arranged on the flange plate 1, and the calibration workpiece includes a flange plate 2 and a calibration column arranged on the flange plate 2, and the calibration column is provided with an alignment pin hole for accommodating the alignment pin.

3. The dual-manipulator base coordinate system calibration and coaxial positioning method according to claim 2, characterized in that: There are three alignment pins and three calibration columns, two of which are symmetrically arranged about the center of the flange, and the other is on the same radius as the two of them and is arranged at the midpoint of the semicircle where the two of them are located.

4. The dual-manipulator base coordinate system calibration and coaxial positioning method according to claim 2, characterized in that: The depth of the alignment pin hole is smaller than the length of the alignment pin.

5. The dual-manipulator base coordinate system calibration and coaxial positioning method according to claim 1, characterized in that: In step S3, when processing the data obtained in step S2, the following sub-steps are included: S31: removing outliers from the data obtained in step S2 and performing data averaging to obtain a data set; S32: Convert the translation vector and rotation vector in the data set into a homogeneous matrix; S33: According to the homogeneous matrix of the first robot arm and the homogeneous matrix of the second robot arm, a calibration matrix for describing the transformation relationship between the base coordinate systems of the two robot arms is obtained.

6. The dual-manipulator base coordinate system calibration and coaxial positioning method according to claim 5, characterized in that: In step S32, the rotation vector is converted into a rotation matrix using the Rodriguez rotation formula, and the Rodriguez rotation formula is: Where: is the rotation matrix; θ is the rotation angle; u x 、u y 、u z are the normalized rotation axes of the x, y, and z axes, respectively, (u x ,u y ,u z ) is the axis of rotation; are the average values ​​of the rotation vectors rx, ry, and rz respectively; The homogeneous matrix obtained according to the translation vector and the rotation matrix is: Where: is a homogeneous matrix; x, y, z are the translation vectors of the x, y, and z axes of the tool coordinate system in the robot base coordinate system.

7. The dual-manipulator base coordinate system calibration and coaxial positioning method according to claim 6, characterized in that: In step S33, the calibration matrix used to describe the conversion relationship between the two robot base coordinate systems is: Where: is the calibration matrix used to describe the transformation relationship between the two robot base coordinate systems; is the homogeneous matrix of robot arm No. 1; is a 4×4 identity matrix; is the homogeneous matrix of the second robot arm The inverse matrix of .

8. The dual-manipulator base coordinate system calibration and coaxial positioning method according to claim 1, characterized in that: In step S4, the final calibration matrix is ​​obtained by averaging the calibration matrices obtained multiple times for describing the conversion relationship between the two robot arm base coordinate systems.

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