Full-field three-dimensional scanning and measuring robot system for inner surface of long straight pipe

Abstract

The invention discloses a full-field three-dimensional scanning and measuring robot system for the inner surface of a long straight pipe. On the basis of the laser tracker and the spherical coordinate system laser scanner, full-field scanning of the inner surface of the long straight pipe is achieved through the plane mirror reflection spherical coordinate system laser scanner. Different from an existing long straight pipe inner wall detection method, the method has the advantages that the laser scanner is never moved from the beginning to the end of detection, so that point cloud acquisition at each time is in the same coordinate system, a complicated splicing algorithm is not needed, and errors caused by the algorithm are reduced; and the real-time calibration of the pose of the plane mirror is realized by using the laser tracker, the accurate position and pose information of the plane mirror can be efficiently obtained, and finally the efficient acquisition of the high-precision point cloud of the inner wall of the long straight pipe under the coordinate system of the spherical coordinate system laser scanner is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of measurement technology, and relates to a long straight pipe inner surface full-field three-dimensional scanning measurement robot system. BACKGROUND

[0002] At present, long straight pipes are key components of many important equipment in the fields of energy and chemical industry, industrial manufacturing, medical treatment and scientific research, aerospace and military, etc. How to realize precision detection of the inner diameter, straightness and bending degree, wall thickness uniformity, surface roughness and topography of long straight pipes based on sensing technology, information technology and Internet of Things technology is the key to ensuring the use quality and initial performance of long straight pipes and realizing their preventive maintenance and risk control.

[0003] Chinese invention patent (publication number: CN114199147A) proposes to set multiple installation grooves in the circumferential direction on the same section, and install a turning light probe in each installation groove to measure the inner diameter and coaxiality of the long straight pipe. However, this method is slow in measurement speed, and can only measure the inner diameter of a certain section, is easily affected by defects and environment, and has low understanding of the overall condition of the long straight pipe.

[0004] Chinese invention patent (publication number: CN119043127A) proposes a long straight pipe diameter measuring device and detection method. The long straight pipe diameter measuring device and detection method can control the extension of the clamping rod into the long straight pipe through the pipe diameter measuring mechanism, measure the pipe diameter and inner diameter of one end of the long straight pipe through the cooperation of the pointer and the corresponding size scale, have good measurement stability, reduce the measurement difficulty, and reduce the measurement error. However, the measurement device of this method is too large in size, is inconvenient to move, and is a contact type measurement, which is slow in measurement efficiency.

[0005] Chinese invention patent (publication number: CN110726731A) designs a small-caliber long straight pipe inner wall defect detection device. The device reflects the light of the pipe wall to an industrial camera through a plane mirror. This scheme adopts a telecentric lens and a linear array CCD camera, so that it has high resolution, low distortion, and fast and efficient imaging effect, which improves the image precision while greatly reduces the image distortion. The rotating table drives the workpiece to rotate to obtain a 360° expanded image of the inner wall of the cylinder, and the inner wall defect detection is realized by using the different reflection images of the defect-free part and the defect part. However, this method also has many deficiencies. The device has various precise components, which makes it have a higher cost, has higher requirements for the detection environment and operating conditions, and also has higher requirements for maintenance work. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a long straight pipe inner surface full-field three-dimensional scanning measurement robot system.

[0007] This invention provides a robotic system for full-field three-dimensional scanning and measurement of the inner surface of a long straight tube, comprising:

[0008] Industrial control computers;

[0009] A rotary motion module is used to drive the long rod to rotate;

[0010] Linear motion module, used to drive rotary motion module to move in a straight line;

[0011] A long rod, with a plane mirror fixed at one end and the other end connected to a rotary motion module;

[0012] Three target balls, fixed on a long rod and not in a straight line, are used to work with a laser tracker to determine the pose of the plane mirror;

[0013] A laser tracker is used to acquire the coordinate information of the target ball in order to determine the pose of the plane mirror;

[0014] A spherical coordinate system laser scanner is used to scan the inner wall of a long straight tube by reflecting light through a plane mirror to obtain point cloud data;

[0015] The rotary motion module and the linear motion module are driven by motors, which are electrically connected to motor drivers. The motor drivers are electrically connected to an industrial control computer. The laser tracker and the spherical coordinate system laser scanner are both electrically connected to the industrial control computer. The industrial control computer is used to control the motor motion and to receive and process data information from the laser tracker and the laser scanner.

[0016] This invention provides a method for full-field three-dimensional scanning measurement of the inner surface of a long straight tube, comprising the following steps:

[0017] Step 1. Control the linear motion module to move the plane mirror to the near end of the long straight tube and stop it;

[0018] Step 2. Use a laser tracker to obtain the coordinate information of the centers of the three target spheres;

[0019] Step 3. Determine the pose of the plane mirror based on the coordinates of the target ball's center;

[0020] Step 4. Control the laser scanner to scan the inner wall of the long straight tube through reflection from the plane mirror to obtain point cloud data;

[0021] Step 5. Process the acquired point cloud data based on the pose information of the plane mirror;

[0022] Step 6. Control the plane mirror to move a preset distance along the axis of the long straight tube, and repeat the steps of obtaining the target ball center coordinates with the laser tracker, determining the plane mirror pose, and scanning with the laser scanner until the full-field scan of the inner surface of the long straight tube is completed.

[0023] Step 7. Stitch together the point cloud data obtained from each scan to form a full-field 3D point cloud of the inner wall of the long straight pipe, and output the scan results for further analysis.

[0024] This invention utilizes a laser tracker and a spherical coordinate system laser scanner to achieve full-field scanning of the inner surface of a long straight tube using a plane mirror reflecting the spherical coordinate system laser scanner. Unlike existing methods for detecting the inner wall of long straight tubes, in this invention, the laser scanner never moves from the start to the end of the detection process. Therefore, each point cloud acquisition is performed in the same coordinate system, eliminating the need for complex stitching algorithms and reducing errors caused by algorithms. Furthermore, the laser tracker enables real-time calibration of the plane mirror's pose, efficiently obtaining accurate position and attitude information of the plane mirror. Ultimately, this achieves efficient acquisition of high-precision point clouds of the inner wall of a long straight tube in the spherical coordinate system laser scanner coordinate system. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0026] Figure 2 This is a flowchart of the measurement method of the present invention;

[0027] Figure 3 This is a diagram showing the relationship between planes α, β, and γ. Detailed Implementation

[0028] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this specification. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this specification as detailed in the appended claims.

[0029] like Figure 1 As shown, the system provided in this application embodiment includes an industrial control computer 17, a rotary motion module 8, a linear motion module 11, three target balls (target ball 5, target ball 3, and target ball 4), a long rod 9, a plane mirror 10, a first motor 2, a second motor 6, a first motor driver 13, a second motor driver 12, a worktable 14, and an industrial control computer 17.

[0030] The rotary motion module 8 includes a connecting flange 7. One end of a long rod 9 is fixed to a plane mirror 10, and the other end is connected to the rotary motion module 8 via the connecting flange 7, passing through the connecting flange 7 to the other side of the rotary motion module 8. Three target balls are fixed to the top of the long rod on the other side of the connecting flange 7. The three target balls are not in a straight line; target ball 3 (number 2), target ball 4 (number 3), and the long rod 9 are in the same plane. The axis of the long rod 9 coincides with the rotation axis of the rotary motion module 8. The rotary motion module 8 is mounted on the slider 19 of the linear motion module 11, and the long rod 9 is parallel to the direction of movement of the linear motion module 11.

[0031] Furthermore, the rotary motion module 8 is driven by motor 6 (number two), and the linear motion module is driven by motor 2 (number one). Motor 2 (number one) and motor 6 (number two) are electrically connected to motor driver 13 (number one) and motor driver 12 (number two), respectively, and are driven by these two motor drivers. The industrial control computer 17 is electrically connected to the two motor drivers and controls the movement of the two motors.

[0032] Furthermore, such as Figure 3 As shown, the plane α formed by the centers of the three target balls is perpendicular to the long rod. Target ball 3 and target ball 4 form plane β with the long rod. The plane γ containing the plane mirror makes an angle θ with plane β, ranging from 5° to 175°.

[0033] When the system is working, it works in conjunction with a laser tracker 1 and a spherical coordinate system laser scanner 18. The laser tracker 1 is placed near one side of the three target spheres, and the spherical coordinate system laser scanner 18 is placed next to the plane mirror. The long straight tube 15 being measured is fixed between the spherical coordinate system laser scanner 18 and the rotation module 8. The long straight tube 15 and the linear motion module 11 are both supported and fixed by a bracket 16 or a worktable 14. The laser emitted by the spherical coordinate system laser scanner 18 is reflected by the plane mirror and irradiates the inner wall of the long straight tube.

[0034] The linear motion module is parallel to the axis of the long straight tube. Both the laser scanner and laser tracker are electrically connected to the industrial control computer. The industrial control computer can control the two motors and receive data from the laser tracker and laser scanner. The spherical coordinate laser scanner obtains the three-dimensional coordinates of the scanned point by measuring the pitch angle, yaw angle, and laser range of its laser beam.

[0035] In one specific embodiment, the spherical coordinate laser 3D scanner is a Surphaser terrestrial laser scanner, model 100HSXIR, with a typical scan rate of 208,000 pps. The plane mirror has a laser reflectivity ≥90%, a planeness ≤10μm, and is elliptical in shape with a major axis of 180mm, a minor axis of 140mm, and is at a 45-degree angle to the axis of the long straight tube. Both the rotary motion module and the linear motion module use stepper motors, model 57BYG250B, with corresponding DRV8825 drivers. The target ball is made of ceramic with a gray frosted surface, a diameter of 30mm, and a sphericity ≤5μm. The industrial computer is an Advantech IPC-610L-510L equipped with a wireless network card.

[0036] Based on the above system structure, this application also provides a method for full-field three-dimensional scanning measurement of the inner surface of a long straight tube, see [link to relevant documentation]. Figure 2 This embodiment targets a 155mm long straight tube, with an inner diameter of 155mm and a length of 8.06 meters, and internal rifling. A long rod equipped with a plane mirror and a standard sphere is placed into the opening of the long straight tube. A spherical coordinate laser 3D scanner is then supported and fixed near the opening of the tube using a bracket, approximately 30cm away from the opening. The laser tracker is placed behind the rotating module, at a distance of about one meter. The method of this embodiment includes the following steps:

[0037] (1) The industrial control computer controls the linear module to move the plane mirror to the near end of the long straight tube and stop it. The number of rotations of the plane mirror i=0 is recorded (the x-axis of the laser tracker is parallel to the direction of the linear module and the direction of the long rod, the z-axis is perpendicular to the horizontal plane, and the y-axis is determined by the right-hand rule);

[0038] (2) Use an industrial computer to control the laser tracker to obtain the coordinates of the centers of the three target spheres at this time, and record the coordinates of the centers of the three target spheres in the coordinate system of the laser tracker as follows: (Where 1, 2, and 3 represent the three target spheres on the side of the connecting flange furthest from the plane mirror, k represents the k-th adjustment of the plane mirror's pose, the point cloud coordinates of the three target spheres acquired by the laser tracker in the k-th iteration, and the point cloud data of the inner wall of the long straight pipe acquired by the laser scanner in the k-th iteration); Plane α is calculated using the coordinates of the three sphere centers: , rotate plane α around the straight line Rotate θ so that plane α is parallel to the plane mirror, and move a distance L along the x-axis of the laser tracker coordinate system (L is the distance from plane α to the plane γ where the plane mirror is located). The overall transformation matrix is:

[0039]

[0040] in

[0041]

[0042]

[0043] In matrix R

[0044]

[0045] The reflecting plane of the plane mirror is A. im x+B im y+C im z+D=0;

[0046] (3) Use the transformation matrix t0 (before the system starts working, the transformation relationship between the coordinate systems of the spherical coordinate system laser scanner and the laser tracker is known, transformation matrix t0) to transform the coordinates of the reflecting plane in the coordinate system of the laser tracker to the coordinate system of the laser scanner. An industrial computer controls a laser scanner to scan the mirror image of the inner wall of a long straight tube within a plane mirror. The point cloud coordinates of this mirror image are recorded as follows: Where m represents the number of times the plane mirror moves forward and backward (i.e., the number of times the straight module moves), i represents the number of times the plane mirror rotates after the i-th movement (i.e., the number of times the rotating module rotates), and n represents the point cloud sequence number of each movement scan. The actual point cloud of the inner wall of the long straight pipe is obtained through a planar symmetric algorithm. While the laser scanner acquires the point cloud, the laser tracker can continuously measure the three target spheres and solve the reflection plane using the formula in step two to detect the pose of the plane mirror, ensuring the accuracy of the point cloud acquisition.

[0047] (4) The industrial control computer controls the plane mirror to rotate by an angle η, let m=m+1, and determine whether m is greater than or equal to the rounded-up value of 360 / η. If so, proceed to step (5); otherwise, return to step (2).

[0048] (5) The industrial control computer controls the motor of the linear motion module to move the plane mirror forward by a distance D. Let i = i + 1, and determine whether i is greater than or equal to the rounded-up value of L / D, where L is the length of the long straight tube. If yes, proceed to step (6); otherwise, the industrial control computer controls the linear motion module to move the plane mirror to the far end of the long straight tube by a distance D and let m = 0, and then return to step (2).

[0049] (6) The industrial control computer generates the actual point cloud of the inner wall of the long straight pipe obtained from each scan. The points are stitched together to form a full-field 3D point cloud of the inner wall of a long straight pipe, denoted as . The scan results are then output for further calculation of the inner wall dimensions of long straight pipes and defect identification.

[0050] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A long straight tube inner surface full-field three-dimensional scanning measurement robot system, characterized in that, include: Industrial control computers; A rotary motion module is used to drive the long rod to rotate; Linear motion module, used to drive rotary motion module to move in a straight line; A long rod, with a plane mirror fixed at one end and the other end connected to a rotary motion module; Three target balls, fixed on a long rod and not in a straight line, are used to work with a laser tracker to determine the pose of the plane mirror; A laser tracker is used to acquire the coordinate information of the target ball in order to determine the pose of the plane mirror; A spherical coordinate system laser scanner is used to scan the inner wall of a long straight tube by reflecting light through a plane mirror to obtain point cloud data; The rotary motion module and the linear motion module are driven by motors, which are electrically connected to motor drivers. The motor drivers are electrically connected to an industrial control computer. The laser tracker and the spherical coordinate system laser scanner are both electrically connected to the industrial control computer. The industrial control computer is used to control the motor motion and to receive and process data information from the laser tracker and the laser scanner.

2. The long straight tube inner surface full-field three-dimensional scanning measuring robot system according to claim 1, characterized in that, The three target balls are target ball number one, target ball number two, and target ball number three. Target ball number two, target ball number three, and the long rod are located in the same plane, and the plane formed by the centers of the three target balls is perpendicular to the long rod.

3. The long straight tube inner surface full-field three-dimensional scanning measuring robot system according to claim 2, characterized in that, The plane containing the plane mirror forms an angle with the plane formed by the second target ball, the third target ball, and the long rod, and the angle ranges from 5° to 175°.

4. The long straight tube inner surface full-field three-dimensional scanning measuring robot system according to claim 1, characterized in that, The rotary motion module includes a connecting flange, through which the long rod is connected to the rotary motion module and passes through the connecting flange to the other side of the rotary motion module.

5. The long straight tube inner surface full-field three-dimensional scanning measuring robot system according to any one of claims 1 to 3, characterized in that, The target ball is made of ceramic, has a gray frosted surface, a diameter of 30 mm, and a sphericity of ≤5 micrometers.

6. The long straight tube inner surface full-field three-dimensional scanning measuring robot system according to claim 1, wherein, The plane mirror has a reflectivity of ≥90% for laser light, a flatness of ≤10μm, and is elliptical in shape with a major axis of 180mm, a minor axis of 140mm, and is at a 45-degree angle to the axis of the long straight tube.

7. A method for full-field three-dimensional scanning and measuring the inner surface of a long straight pipe, using the robotic system of any one of claims 1-6, characterized in that The method includes the following steps: Step 1. Control the linear motion module to move the plane mirror to the near end of the long straight tube and stop it; Step 2. Use a laser tracker to obtain the coordinate information of the centers of the three target spheres; Step 3. Determine the pose of the plane mirror based on the coordinates of the target ball's center; Step 4. Control the laser scanner to scan the inner wall of the long straight tube through reflection from the plane mirror to obtain point cloud data; Step 5. Process the acquired point cloud data based on the pose information of the plane mirror; Step 6. Control the plane mirror to move a preset distance along the axis of the long straight tube, and repeat the steps of obtaining the target ball center coordinates with the laser tracker, determining the plane mirror pose, and scanning with the laser scanner until the full-field scan of the inner surface of the long straight tube is completed. Step 7. Stitch together the point cloud data obtained from each scan to form a full-field 3D point cloud of the inner wall of the long straight pipe, and output the scan results for further analysis.

8. The method for full-field three-dimensional scanning measurement of the inner surface of a long straight pipe according to claim 7, characterized in that: In step 2, the three-dimensional coordinates of the target ball's center are recorded in the coordinate system of the laser tracker, and the equation of the target ball's plane is obtained through calculation.

9. The method for full-field three-dimensional scanning measurement of the inner surface of a long straight pipe according to claim 8, characterized in that: In step 3, the equation of the reflection plane of the plane mirror is calculated based on the equation of the target sphere plane, and the equation of the reflection plane is transformed from the coordinate system of the laser tracker to the coordinate system of the laser scanner through the coordinate system transformation matrix.

10. The method for full-field three-dimensional scanning measurement of the inner surface of a long straight pipe according to any one of claims 7 to 9, characterized in that: In step 5, the point cloud data is processed using a planar symmetric algorithm to obtain the actual point cloud data of the inner wall of the long straight pipe.

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