A rapid alignment method based on the relative position relationship of bolts of components

Abstract

The invention discloses a rapid alignment method based on the relative position relationship of bolts of parts and components, comprising the following steps: S1, calculating the posture information of parts and components; S2, using visual servoing to perform the first bolt tightening operation; S3, calculating the end posture adjustment matrix of the manipulator; S4, selecting the bolt closest to the tightened bolt as the bolt to be aligned, and reading the relative position parameters between the two; S5, calculating the end posture information of the manipulator when the end of the manipulator is aligned with the next bolt; S6, controlling the movement of the end of the manipulator to align the bolts; S7, controlling the tightening tool installed at the end of the manipulator to rotate into the bolt and perform the tightening operation; S8, repeating S3 to S7 until the alignment and tightening operation of all bolts of the part and component is completed. The invention can reduce the demand for visual inspection devices, improve maintenance efficiency and the accuracy of bolt alignment.

Description

Technical Field

[0001] The invention relates to the technical field of robots, and in particular to a rapid alignment method based on the relative position relationship of bolts of components. Background Art

[0002] The contact network is an important component of the railway system and is of irreplaceable importance. It provides a stable, safe, efficient and environmentally friendly power supply for the electrified railway system, ensuring the normal operation of trains and the travel safety of passengers. The contact network is composed of a series of metal components, such as contact wires, contact network poles, insulators, etc. These components need to be connected by bolts to ensure the structural stability and integrity of the entire contact network system. After long-term use and wear caused by natural environmental factors, the bolts have the risk of loosening and falling off. Therefore, it is particularly important to maintain and repair the bolts of the contact network.

[0003] Traditional overhaul of contact network bolts mainly adopts manual maintenance. The contact network bolts are widely distributed and numerous, and the maintenance process requires personnel to check and tighten them one by one. This manual maintenance method requires a lot of manpower and time, with high labor intensity, long maintenance cycle and low efficiency. If some contact networks are located in inaccessible areas such as elevated bridges and tunnels, they cannot be overhauled by conventional manual maintenance methods. Bolt overhaul in these areas may require the use of special tools and equipment, which increases the complexity and cost of maintenance. Therefore, a solution of using a robotic arm to replace manual maintenance of bolts has emerged. The alignment of the bolts by the robotic arm relies on the visual information obtained by the visual sensor it carries. Nowadays, visual servo technology is generally used for bolt alignment. It takes at least 10 seconds for the robotic arm to align a bolt using visual servo, but there are usually 3 to 5 bolts that need to be overhauled for the same component. Therefore, if all bolts are aligned using visual servo, the working time will be greatly increased, which is not conducive to practical application. Summary of the invention

[0004] In order to solve the problems of low maintenance efficiency and long working time in the process of bolt tightening using visual servoing by a robot arm, the present invention proposes a rapid alignment method based on the relative position relationship of component bolts to solve the above problems.

[0005] The present application discloses a rapid alignment method based on the relative position relationship of component bolts, comprising the following steps:

[0006] S1, the camera obtains a complete image of a component and calculates the posture information of the component;

[0007] S2, using visual servoing to align the robot arm with the first bolt and perform the first bolt tightening operation;

[0008] S3, read and record the end-arm posture information when the last bolt tightening operation was completed, and calculate the end-arm posture adjustment matrix of the robot arm in combination with the component posture information of S1 to facilitate subsequent bolt alignment;

[0009] S4, selecting the bolt closest to the tightened bolt in S3 as the bolt to be aligned, and reading the relative position parameters between the two;

[0010] S5, combining the end-of-arm posture information in S3, the end-of-arm posture adjustment matrix, and the known relative position parameters of the two bolts in S4, to calculate the expected end-of-arm posture information when the end-of-arm is aligned with the next bolt;

[0011] S6, outputting the desired end-of-arm posture information obtained in S5 to the robot arm through the MOVEL instruction, thereby controlling the movement of the end-of-arm to align the bolts;

[0012] S7, when the alignment of S6 is completed, the tightening tool installed at the end of the robot arm is controlled to rotate into the bolt and perform the tightening operation;

[0013] S8. Repeat S3 to S7 until the alignment and tightening of all bolts of the component are completed.

[0014] Preferably, the calculation formula of the posture information in S1 is:

[0015]

[0016] in, is the transformation matrix from the robot base coordinate system to the component coordinate system, is the transformation matrix from the robot base coordinate system to the robot end coordinate system, is the transformation matrix from the robot end coordinate system to the camera coordinate system, It is the transformation matrix from the camera coordinate system to the component coordinate system.

[0017] Preferably, S3 comprises the following steps:

[0018] When the first bolt tightening operation is completed, the end position of the robot arm is read and recorded by RTDE, and its homogeneous matrix form is recorded as At this time, there is a deviation between the posture of the robot arm end coordinate system and the posture of the component coordinate system, and adjustment and alignment are required. After adjustment and alignment, the robot arm end and the first tightened bolt A still coincide, and the following formula exists:

[0019]

[0020] in, is the transformation matrix from the base of the robot to the first tightened bolt A, To adjust the transformation matrix from the base to the end of the robot after alignment, Adjust the matrix for the end-arm posture. Depend on and t=(0,0,0), where for The rotation matrix part of ;

[0021] Because the robot base and components have not changed, It can be obtained by the following formula:

[0022]

[0023] in, Represents the transformation matrix from the current robot end coordinate system to the component coordinate system.

[0024] Preferably, the relative position parameters of the bolts that have been tightened closest to it in S4 are:

[0025] Note that the bolt closest to the first tightened bolt A is bolt B, then:

[0026]

[0027] Where -a represents the relative offset of bolt B relative to bolt A on the y-axis.

[0028] Preferably, S5 comprises the following steps:

[0029] Calculate the end-arm position of the robot aligned with bolt B:

[0030]

[0031] When the end of the robot arm is aligned with bolt B:

[0032]

[0033] Then we can get:

[0034]

[0035] in, is the desired end position of the robot arm.

[0036] Preferably, S6 comprises the following steps:

[0037] S61, when the robot arm visual servo is aligned to tighten bolt A, first The MOVEL command of RTDE is output to the robot arm, causing the end of the robot arm to move back 0.05m to a safe area to prevent collision in subsequent operations;

[0038] S62, the desired end position obtained in S5 The MOVEL instruction of RTDE is output to the robot arm to control the movement of the robot arm so that the tightening tool installed at the end of the robot arm is aligned with bolt B.

[0039] Beneficial effects of the present invention:

[0040] (1) After the first servo alignment of bolts on a certain component is completed, the present invention will abandon visual information for the alignment of the remaining bolts of the component, and quickly align them based on the relative position relationship of the pre-acquired and aligned bolts. The time required to align a bolt is no more than 5 seconds, which can reduce the demand for visual inspection devices.

[0041] (2) The total time required for aligning all bolts on a component by the present invention is much shorter than the total time required for aligning all bolts by visual servoing, which greatly shortens the time for bolt maintenance using a robotic arm and improves the maintenance efficiency and the accuracy of bolt alignment. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flow chart of a rapid alignment method based on the relative position relationship of bolts of components according to an embodiment of the present invention;

[0043] Figure 2 A coordinate system diagram of the end of the robot arm, the camera, and the components according to an embodiment of the present invention;

[0044] Figure 3 A component pose graph obtained by the visual algorithm of an embodiment of the present invention;

[0045] Figure 4 It is a schematic diagram of aligning the first bolt A through visual servoing according to an embodiment of the present invention;

[0046] Figure 5 This is a schematic diagram of the end of the robot arm retreating to a safe area according to an embodiment of the present invention;

[0047] Figure 6 A schematic diagram of the end of the mechanical arm of an embodiment of the present invention aligning with the next bolt;

[0048] Figure 7 A schematic diagram of the end of the robot arm according to an embodiment of the present invention screwing in the next tightening bolt;

[0049] Figure 8 It is a front view of parts of an embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples.

[0051] The embodiment of the present application discloses a rapid alignment method based on the relative position relationship of bolts of components, the process is as follows: Figure 1 As shown, the following steps are included:

[0052] S1. The camera obtains a complete image of a component and calculates the posture information of the component.

[0053] The coordinate systems of the robot end, camera, and parts are as follows: Figure 2 As shown in the figure, the calculation formula of posture information is:

[0054]

[0055] in, is the transformation matrix from the robot base coordinate system to the component coordinate system; It is the transformation matrix from the robot base coordinate system to the robot end coordinate system, which can be directly read through RTDE; is the transformation matrix from the robot end coordinate system to the camera coordinate system, which can be obtained by camera extrinsic calibration; is the transformation matrix from the camera coordinate system to the component coordinate system, which is obtained by the visual algorithm. Its accuracy will affect the accuracy of the final alignment. In this implementation, the visual algorithm uses a template matching algorithm. The image obtained by the visual algorithm is as follows: Figure 3 shown.

[0056] S2, such as Figure 4 As shown, the first bolt A to be tightened is selected, and the end tool of the robot arm is aligned with the first bolt A through the existing visual servoing, and then the end tool of the robot arm is rotated to enter and tighten the bolt A. This is the first bolt tightening operation.

[0057] S3. When the last bolt tightening operation is completed, the end position information of the robot arm is read and recorded through RTDE, which is expressed in the form of translation vector and rotation vector. Its homogeneous matrix form is recorded as The embodiment of the present application uses the robot end coordinate system as a reference to control the movement of the end tool. At this time, there is a deviation between the posture of the robot end coordinate system and the posture of the component coordinate system, and adjustment and alignment are required to facilitate the subsequent rapid alignment operation. After adjustment and alignment, the end of the robot arm and the first tightened bolt A still overlap, and the following formula exists:

[0058]

[0059] in, is the transformation matrix from the base of the robot to the first tightened bolt A, To adjust the transformation matrix from the base to the end of the robot after alignment, Adjust the matrix for the end-arm posture. Depend on and t=(0,0,0), where for The rotation matrix part of ;

[0060] Because the robot base and components have not changed, It can be obtained by the following formula:

[0061]

[0062] in, Represents the transformation matrix from the current robot end coordinate system to the component coordinate system.

[0063] S4, select the bolt B closest to the tightened bolt A in S3 as the bolt to be aligned, and read the known relative position relationship parameters between bolts A and B, recorded as Depend on Figure 8 It can be seen that:

[0064]

[0065] The parameter -a represents the relative displacement of bolt B relative to bolt A on the y-axis, and its value is obtained from the CAD drawing or measured by other means. In this embodiment, it is obtained by measurement, and the measuring tool used is a height gauge, and its measurement accuracy can reach 0.02mm.

[0066] S5. Combining the end-arm posture information in S3, the end-arm posture adjustment matrix and the known relative position parameters of the two bolts in S4, the expected end-arm posture information when the end-arm is aligned with the next bolt is calculated.

[0067] Calculate the end-arm position of the robot aligned with bolt B:

[0068]

[0069] When the end of the robot arm is aligned with bolt B:

[0070]

[0071] Then combined with S3 we can get:

[0072]

[0073] in, is the desired end position of the robot arm.

[0074] S6. Output the desired robot arm end position information obtained in S5 to the robot arm through the MOVEL instruction, thereby controlling the movement of the robot arm end to align the bolts.

[0075] S61, when the robot arm visual servo is aligned to tighten bolt A, first The MOVEL instruction of RTDE is output to the robot arm, so that the end of the robot arm moves back 0.05m to the safe area to prevent collision in subsequent operations, such as Figure 5 shown.

[0076] S62, the desired end position of the robot arm obtained in S5 The MOVEL instruction of RTDE is output to the robot arm to control the movement of the robot arm so that the tightening tool installed at the end of the robot arm is aligned with bolt B, such as Figure 6 shown.

[0077] S7. When the alignment of S6 is completed, the tightening tool installed at the end of the robot arm is controlled by RTDE to rotate into the bolt and perform the tightening operation, such as Figure 7 shown.

[0078] S8. Repeat S3 to S7 for bolts B and bolts C, align and tighten bolt C and the remaining bolts until the alignment and tightening of all bolts of the component are completed.

[0079] In a specific embodiment, the feasibility and effect of the method of the present application are verified through experiments. The UR collaborative robot is used for experimental verification, and the movement of the robotic arm is controlled through the robot control and data exchange protocol RTDE (Real-Time Data Exchange). RTDE can synchronize external applications with the UR robot controller through standard TCP / IP. It only needs to input the desired posture of the end of the robotic arm to control the motion of the end of the robotic arm. Therefore, how to obtain the accurate desired posture of the end of the robotic arm is the core of achieving rapid alignment. However, due to the differences in the installation methods of the same component in different positions under the contact network environment, there is currently no accurate measurement method on site to obtain the tilt angle θ, such as Figure 8 As shown. Failure to obtain this angle means that the desired position and posture of the end of the robot arm cannot be accurately obtained, and thus rapid alignment cannot be achieved. The method of the present application circumvents this problem by estimating the position and posture of the components through an image algorithm.

[0080] The positioning tube clip installed on the positioning tube is selected as an example for explanation. The relevant coordinate systems involved are as follows: Figure 2 As shown, an experimental verification was carried out, the bolt position parameters a and b on 20 positioning pipe clamps were measured and an alignment experiment was carried out, and the obtained data results are shown in Table 1:

[0081] Table 1 Alignment of parameters a and b using measured values

[0082]

[0083]

[0084] As shown in Table 1, among the 20 sets of experimental data, when the visual servo is aligned to tighten bolt A, Figure 7 The success rate of quick alignment of bolt B is 100%, and the success rate of quick alignment of bolt C is 85%. The average alignment time of the two is 3.715s and 4.555s respectively. The a and b values ​​used in the quick alignment are obtained by measurement.

[0085] Next, a second round of experiments was conducted using the average values ​​for both a and b. The alignment of the 20 components is shown in Table 2:

[0086] Table 2 Alignment of parameters a and b using average values

[0087] 1 2 3 4 5 6 7 8 9 10 Align a √ √ √ √ √ √ √ √ √ √ Time(s) 3.541 3.654 3.571 3.689 3.771 3.831 3.767 3.682 3.828 3.519 Align b √ √ × √ × √ √ √ √ √ Time(s) 4.656 4.608 4.632 4.517 4.443 4.602 4.671 4.842 11 12 13 14 15 16 17 18 19 20 Align a √ √ √ √ √ √ √ √ √ √ Time(s) 3.666 3.524 3.589 3.921 3.877 3.818 3.636 3.747 3.409 3.352 Align b √ √ × √ √ √ √ √ √ √ Time(s) 4.533 4.605 4.881 4.498 4.473 4.510 4.446 4.465 4.461

[0088] It can be seen from Table 2 that after the visual servoing is aligned and tightened on bolt A, the rapid alignment success rate of bolt B is 100%, and the rapid alignment success rate of bolt C is 85%. The average alignment time of the two is 3.670s and 4.579s, respectively.

[0089] In the embodiment of the present application, the judgment of successful bolt quick alignment is: the distance deviation between the center of the tool sleeve and the center of the bolt surface is 3mm; the alignment time is the time of the entire process of the sleeve tightening bolt A, withdrawing to the safe area, and then aligning with bolt B, excluding the time of the final end tool screwing in to tighten bolt B.

[0090] The errors in the method of the present application mainly include two aspects: one is the measurement error of the relative position parameters of the bolt, which does not exceed 1 mm; the other is the component posture error obtained by the visual algorithm, which has a great influence on the result. Therefore, it is necessary to select a suitable visual algorithm. The template matching algorithm is used in this embodiment.

[0091] In summary, the rapid alignment method based on the relative position relationship of component bolts disclosed in the present application has been proven to be feasible through experiments, with a success rate of over 85%. By performing visual template matching on the entire component, the posture adjustment problem of the end tool alignment is solved, and the total time required to align all bolts on a component using the method of the present application is much less than the total time required to align all bolts through visual servoing, indicating that the present application is practical.

[0092] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A rapid alignment method based on the relative position relationship of bolts of components, characterized in that: The following steps are involved: S1, the camera obtains a complete image of a component and calculates the posture information of the component; The calculation formula of posture information is: in, is the transformation matrix from the robot base coordinate system to the component coordinate system, is the transformation matrix from the robot base coordinate system to the robot end coordinate system, is the transformation matrix from the robot end coordinate system to the camera coordinate system, is the transformation matrix from the camera coordinate system to the component coordinate system; S2, using visual servoing to align the robot arm with the first bolt and perform the first bolt tightening operation; S3, read and record the end-arm posture information when the last bolt tightening operation was completed, and calculate the end-arm posture adjustment matrix of the robot arm in combination with the component posture information of S1 to facilitate subsequent bolt alignment; When the first bolt tightening operation is completed, the end position of the robot arm is read and recorded by RTDE, and its homogeneous matrix form is recorded as At this time, there is a deviation between the posture of the robot arm end coordinate system and the posture of the component coordinate system, and adjustment and alignment are required. After adjustment and alignment, the robot arm end and the first tightened bolt A still coincide, and the following formula exists: in, is the transformation matrix from the base of the robot to the first tightened bolt A, To adjust the transformation matrix from the base to the end of the robot after alignment, Adjust the matrix for the end-arm posture. Depend on and t=(0,0,0), where for The rotation matrix part of ; Because the robot base and components have not changed, It can be obtained by the following formula: in, Represents the transformation matrix from the current robot end coordinate system to the component coordinate system; S4, selecting the bolt closest to the tightened bolt in S3 as the bolt to be aligned, and reading the relative position parameters between the two; S5, combining the end-of-arm posture information in S3, the end-of-arm posture adjustment matrix, and the known relative position parameters of the two bolts in S4, to calculate the expected end-of-arm posture information when the end-of-arm is aligned with the next bolt; S6, outputting the desired end-of-arm posture information obtained in S5 to the robot arm through the MOVEL instruction, thereby controlling the end-of-arm movement to perform bolt alignment; S7, when the alignment of S6 is completed, the tightening tool installed at the end of the robot arm is controlled to rotate into the bolt and perform the tightening operation; S8. Repeat S3 to S7 until the alignment and tightening of all bolts of the component are completed.

2. The rapid alignment method based on the relative position relationship of component bolts according to claim 1 is characterized in that: The relative position parameters of the bolts that have been tightened closest to it in S4 are: Note that the bolt closest to the first tightened bolt A is bolt B, then: Where -a represents the relative offset of bolt B relative to bolt A on the y-axis.

3. The rapid alignment method based on the relative position relationship of component bolts according to claim 2 is characterized in that: The S5 comprises the following steps: Calculate the end-arm position of the robot aligned with bolt B: When the end of the robot arm is aligned with bolt B: Then we can get: in, is the desired end position of the robot arm.

4. The rapid alignment method based on the relative position relationship of component bolts according to claim 3 is characterized in that: The S6 comprises the following steps: S61, when the robot arm visual servo is aligned to tighten bolt A, first The MOVEL command of RTDE is output to the robot arm, causing the end of the robot arm to move back 0.05m to a safe area to prevent collisions in subsequent operations; S62, the desired end position obtained in S5 The MOVEL instruction of RTDE is output to the robot arm to control the movement of the robot arm so that the tightening tool installed at the end of the robot arm is aligned with bolt B.

Images