A testing method of a pipe body caliber laser scanning detector

Abstract

The present application relates to a kind of pipe body caliber laser scanning detector test method.The test method includes the following steps: S1: according to the standard caliber of the pipe body to be measured and laser beam diameter, calculate ranging corner;S2: detector according to ranging corner in pipe body along pipe body caliber section rotates a round, detector measures its own and the interval of pipe body inner wall after each rotation;S3: according to interval and rotating radius, construct virtual circle and determine the center of virtual circle;S4: using cosine theorem, calculate the virtual radius corresponding to each virtual half chord;S5: using sine theorem, calculate the included angle of virtual diameter and virtual radius as corresponding virtual center angle;S6: according to virtual radius and laser beam diameter, calculate actual corner;S7: according to the mapping relationship between pipe body standard caliber and actual corner, establish conversion table.The present application can improve the efficiency of pipe body inner wall detection by calculating the actual diameter and virtual radius of pipe body, under the premise of maintaining detection accuracy.

Description

Technical Field

[0001] This invention relates to the field of pipe inspection technology, and in particular to a testing method for a laser scanning instrument for pipe diameter. Background Technology

[0002] In pipe inspection, the measurement of the inner diameter of the pipe is often inaccurate because the central axis of the pipe is difficult to determine. For example, it is difficult to directly measure the inner diameter of the pipe in the circumferential direction by manual measurement, and the inner diameter calculated by multi-point measurement can only be used as the average inner diameter, which is not suitable for accurately measuring the unevenness or ellipticity of the pipe wall.

[0003] Laser scanning detectors calculate the distance between an object and its target by emitting a laser and receiving the echo signal. While miniature laser scanning detectors can measure the inner diameter of tubes, achieving complete coverage of the inner wall and accurately measuring unevenness or ellipticity remain significant challenges. Furthermore, comprehensive scanning of the inner wall greatly reduces the efficiency of tube inspection. Summary of the Invention

[0004] Therefore, it is necessary to provide a testing method for a tube diameter laser scanning detector to address the problem of balancing detection accuracy and efficiency in tube diameter measurement.

[0005] This invention is achieved through the following technical solution: A testing method for a tube diameter laser scanning detector includes the following steps:

[0006] S1: Based on the standard pipe diameter and the laser beam diameter of the detector, calculate the minimum number of measurement points required to cover the entire inner circumference of the pipe, and then calculate the measuring angle of the detector. Therefore, the minimum number of measurement points N is:

[0007]

[0008] Where N is an even number, α is the central angle corresponding to the laser beam diameter being a chord of the tube's cross-sectional circle, L is the laser beam diameter, and R0 is the standard inner radius of the tube.

[0009] Distance measurement angle α f for:

[0010] α f =2π / N.

[0011] S2: The detector rotates one revolution along the cross-section of the pipe's diameter inside the pipe body according to the measuring angle. Each time the detector rotates one measuring angle, it measures the distance s between itself and the inner wall of the pipe body and records the number of rotations c.

[0012] S3: Obtain the rotation radius r of the detector, construct a virtual circle based on the spacing s, rotation radius r, and number of rotations, and determine the center of the virtual circle. The specific method is as follows:

[0013] S31: Add the radius of rotation to each measured interval as a virtual half-chord.

[0014] S32: Map the virtual half-strings to a planar coordinate system based on the chord length and number of rotations of each virtual half-string. The starting point of each virtual half-string is located at the origin O2. The angle between any two adjacent virtual half-strings is equal to the ranging rotation angle α. f .

[0015] S33: Calculate the sum of two virtual half-chords spaced 180° apart in the plane coordinate system as a virtual chord.

[0016] S34: Select the longest virtual chord as the virtual diameter, then the midpoint of the virtual diameter is the virtual center O1.

[0017] S4: Calculate the virtual radius corresponding to each virtual half-chord using the law of cosines. Assume the two endpoints of the virtual diameter are denoted as K and K', and the endpoint of any virtual half-chord furthest from the virtual center is P. Then the virtual radius O1P is expressed as:

[0018]

[0019] Among them, H K H is the distance from O2 to K. K+N H is the distance from O2 to K'. P Let θ be the distance from O2 to P, and θ be the angle between O2P and O2K.

[0020] S5: The angle between the virtual diameter and the virtual radius is calculated using the sine theorem and taken as the corresponding virtual central angle. The virtual central angle β is then expressed as:

[0021]

[0022] S6: Calculate the actual number of measurement points based on the virtual radius and laser beam diameter. Then, calculate the actual rotation angle measured by the detector each time based on the actual number of measurement points. The actual rotation angle θ0 is then expressed as:

[0023]

[0024] Where N1 is the actual number of measurement points, θ l θ is the central angle of the laser beam corresponding to its diameter. δ This is the central angle corresponding to the maximum error distance.

[0025] S7: Establish a conversion table based on the mapping relationship between the standard pipe diameter and the actual rotation angle. The conversion table is used to represent the one-to-one mapping relationship between pipe diameter, number of measurement points, and measurement rotation angle.

[0026] The aforementioned testing method obtains the measuring angle using the standard diameter of the pipe, and then measures the entire circular cross-section covering the inner wall of the pipe through equal-angle rotation to obtain the complete cross-sectional diameter. Based on the minimum central angle formed by the laser beam on the pipe wall during actual measurement, the minimum number of measurement points required to measure the entire circular cross-section of a pipe with a given diameter is determined. Simultaneously, when calculating the actual number of measurement points, a maximum measurement error is introduced to obtain the minimum number of measurement points required while maintaining detection accuracy, thus improving the efficiency of pipe inner wall inspection.

[0027] Preferably, if the minimum number of measurement points is 2m, then each virtual chord is denoted as:

[0028] l i =s i +s i+m +2r(i=1,2,3,...,m).

[0029] Among them, l i For the i-th virtual string, s i Let s be the distance measured when the detector rotates by i ranging angles. i+m The distance measured when the detector rotates i+m distance measuring angles.

[0030] Preferably, the method for calculating the virtual radius is as follows:

[0031] S41: When the virtual half-chord is exactly on the virtual diameter, take half of the virtual diameter as the virtual radius.

[0032] S42: When the virtual half-chord is not on the virtual diameter, the distance from the endpoint of the virtual radius furthest from the virtual center to the virtual center is calculated using the cosine theorem and taken as the virtual radius.

[0033] Preferably, the method for calculating the virtual central angle is as follows:

[0034] S51: When the virtual half-chord is exactly on the virtual diameter, the angle between the virtual radius and the virtual diameter is 0° or 180°, and the corresponding central angle is also 0° or 180°.

[0035] S52: When the virtual half-chord is not on the virtual diameter, the central angle is calculated using the sine theorem.

[0036] Preferably, the method for calculating the actual turning angle is as follows:

[0037] S61: Treat the laser beam diameter as a beam chord in a virtual circle, and calculate the central angle of the beam chord in the virtual circle as the beam central angle.

[0038] S62: Calculate the number of measurement points required for the laser displacement sensor to cover the entire pipe diameter based on the beam center angle, and use this as the theoretical number of measurement points.

[0039] S63: Set the maximum error distance between any two adjacent detection points. Calculate the number of measurement points required for the detector to measure the complete pipe diameter based on the maximum error distance, and use this as the actual number of measurement points. Then, use the ratio of the circumferential angle to the actual number of measurement points as the actual rotation angle.

[0040] Preferably, assuming the laser beam diameter is L, the distance between the laser displacement sensor and the measurement point is s, and the rotation radius of the laser displacement sensor is r, then the central angle of the laser beam is expressed as:

[0041] θ l =arccos(((s+r) 2 +(s+r) 2 -L 2 ) / 2(s+r).

[0042] Preferably, the theoretical number of measurement points N0 is expressed as:

[0043] N0≥2π / min(θ l ).

[0044] Wherein, min(θ) l ) is the minimum value among all beam central angles.

[0045] Preferably, the central angle corresponding to the maximum error distance is expressed as:

[0046] θ δ =arccos{[2(s+r) 2 -δ 2 ] / 2(s+r)}.

[0047] Where δ is the maximum error distance.

[0048] Preferably, the number of measurement points supported by the detector is N. M (M = 2, 4, 6, ...), then the actual number of measurement points N1 is expressed as:

[0049]

[0050] Where N1 is an even number, N Mi N represents the number of measurement points supported by the i-th detector. M(i-1) This represents the number of measurement points supported by the (i-1)th detector.

[0051] Preferably, the detection range of the detector is determined based on the minimum rotation angle of the detector, and the detection range [D1, D2] of the detector is expressed as:

[0052]

[0053] Where γ is the minimum rotation angle of the detector.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] 1. This invention calculates the measuring angle based on the standard diameter of the pipe body, and then measures the entire circular cross-section covering the inner wall of the pipe by equal-angle rotation to obtain the complete cross-sectional diameter. Furthermore, based on the minimum central angle formed by the laser beam on the pipe wall during actual measurement, the minimum number of measurement points required to measure the entire circular cross-section of a pipe with a given diameter is obtained. Simultaneously, when calculating the actual number of measurement points, a maximum measurement error is introduced to obtain the minimum number of measurement points required while maintaining detection accuracy, thereby improving the efficiency of pipe inner wall detection and achieving a balance between detection accuracy and efficiency.

[0056] 2. Based on the correspondence between measurement spacing and angular offset, this invention maps the measured data to a plane coordinate system, which more intuitively and quickly calculates the virtual radius of each detection point, thereby obtaining the total virtual diameter. This facilitates an intuitive judgment of the wear or ellipticity of the pipe inner wall and improves the accuracy of pipe inner wall detection.

[0057] 3. This invention considers the diameter of the detection point formed on the inner wall of the tube after laser emission, and calculates the corresponding central angle based on the diameter of the laser beam, so that the laser detection range fully covers the entire circular cross-section of the tube with the minimum number of measurement points. This not only improves the accuracy of the detector test, but also improves the efficiency of the detector test. Attached Figure Description

[0058] Figure 1 This is a flowchart of the test method of the tube diameter laser scanning detector according to Embodiment 1 of the present invention;

[0059] Figure 2 for Figure 1 A schematic diagram of the structure mapping multiple spacings to a planar coordinate system;

[0060] Figure 3 for Figure 1 A graph showing the spacing data collected when the number of measurement points is 800.

[0061] Figure 4 for Figure 1 A schematic diagram of the virtual central angle;

[0062] Figure 5 for Figure 1 A schematic diagram of the central angle of the mid-beam;

[0063] Figure 6This is a three-dimensional structural diagram of the laser scanning detector for the inner diameter of the tube according to Embodiment 2 of the present invention;

[0064] Figure 7 for Figure 6 Schematic diagram of a laser scanning detector for the inner diameter of a central tube;

[0065] Figure 8 for Figure 6 Three-dimensional structural diagram of the rotating mechanism;

[0066] Figure 9 for Figure 8 A cross-sectional schematic diagram of the rotating mechanism;

[0067] Figure 10 for Figure 6 A three-dimensional structural diagram of the positioning device. Detailed Implementation

[0068] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] It should be noted that when a component is said to be "installed on" another component, it can be directly on the other component or it may be in a component that is centered on it. When a component is said to be "set on" another component, it can be directly set on the other component or it may also be in a component that is centered on it. When a component is said to be "fixed to" another component, it can be directly fixed to the other component or it may also be in a component that is centered on it.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0071] Example 1

[0072] Please see Figure 1 This is a flowchart of the testing method for the pipe diameter laser scanning detector provided in this embodiment. The testing method for the pipe diameter laser scanning detector includes the following steps:

[0073] S1: Calculate the minimum number of measurement points required to cover the entire inner wall of the pipe based on the standard diameter of the pipe and the diameter of the laser beam of the detector, and then calculate the measuring angle of the detector.

[0074] During manufacturing, pipe bodies are typically designed with a standard caliber, representing the ideal caliber for pipe production. However, in actual production, caliber errors due to manufacturing precision are unavoidable. Therefore, after pipe body manufacturing, the inspection of the finished product is crucial. Taking a gun barrel as an example, the gun barrel guides the projectile. Besides requiring sufficient rigidity to support the projectile's launch, it also has strict requirements for its inner diameter and rifling. Therefore, the inner wall of the gun barrel must be precisely inspected after production. A laser scanning inspection instrument can perform a circumferential scan of the pipe's inner wall to obtain multiple inner diameter data points, which can then be used to determine whether the inner diameter meets the standard. Furthermore, after the gun barrel is put into use, to ensure the safety and stability of projectile launch, the wear condition of the inner diameter needs to be precisely inspected to ensure that the projectile can be launched along the predetermined trajectory.

[0075] To ensure measurement accuracy, simplify the measurement process, and improve efficiency, the laser scanning detector first needs to be tested to determine the number of points it should measure under different aperture conditions. During the initial testing phase, to guarantee measurement accuracy, the maximum measuring angle required for the detector to rotate and cover the entire inner diameter needs to be calculated.

[0076] In ideal pipe diameter measurement, the laser beam emitted by the measuring instrument is perfectly aligned with each rotation. Assuming the cross-sectional circle of the pipe diameter is an ideal circle, the center of rotation of the measuring instrument is located precisely at the center of this ideal circle. The laser beam illuminates the ideal circle, forming an arc, and the chord length of this arc is exactly equal to the diameter of the laser beam. The central angle corresponding to this arc is then the ideal measuring angle. However, in actual measurements, due to current technological limitations, the measuring angle supported by the measuring instrument is related to the accuracy of its internal stepper motor, and it cannot be used for angles exceeding the accuracy of the stepper motor. Furthermore, when measuring the actual pipe diameter, to facilitate the calculation of the virtual diameter of the pipe, it is necessary to first calculate the chord lengths of multiple virtual chords passing through the center of rotation; therefore, the actual number of measurement points must be even.

[0077] The minimum number of measurement points N is expressed as:

[0078]

[0079] Where N is an even number, α is the central angle corresponding to the laser beam diameter being a chord of the tube's cross-sectional circle, L is the laser beam diameter, and R0 is the standard inner radius of the tube.

[0080] The laser beam diameter L can be obtained directly from the specifications of the testing instrument. The standard inner radius R of the tube body is half of the standard diameter of the tube body, and can also be obtained directly from the specifications of the tube body.

[0081] Distance measurement angle α f for:

[0082] α f =2π / N.

[0083] S2: The detector rotates one revolution along the cross-section of the pipe's diameter inside the pipe body according to the measuring angle. Each time the detector rotates one measuring angle, it measures the distance s between itself and the inner wall of the pipe body and records the number of rotations c.

[0084] When the detector measures the first distance, the direction of the laser emitted by the detector is recorded as the initial laser direction. Based on the number of rotations c and the ranging angle α... f The angle between the laser direction corresponding to each spacing and the initial laser direction can then be calculated and denoted as c*α. f Where c = (1, 2, 3, ..., N).

[0085] Please combine Figure 2 , it is Figure 1 A schematic diagram of the structure in which multiple spacings are mapped to a planar coordinate system.

[0086] S3: Obtain the rotation radius r of the detector, construct a virtual circle based on the spacing s, rotation radius r, and number of rotations, and determine the center of the virtual circle. The method for determining the center of the virtual circle is as follows:

[0087] S31: Add the rotation radius to each measured interval as a virtual half-chord. During testing, the measuring instrument measures the distance from the laser emission point to the inner wall of the tube, while the instrument's rotation center is not located at the laser emission point. The distance from the instrument's rotation center to the inner wall of the tube should include both the measured interval and the rotation radius, i.e., s + r.

[0088] S32: Map the virtual half-strings to a planar coordinate system based on the chord length and number of rotations of each virtual half-string. The starting point of each virtual half-string is located at the origin O2. The angle between any two adjacent virtual half-strings is equal to the ranging rotation angle α. f .

[0089] Mapping the distances measured by the detector onto a plane coordinate system, with the detector's rotation center as the origin O2, a movement path for the laser emission point can be constructed based on the rotation radius. Then, based on the length of each distance and the angle between the laser direction and the initial laser direction when measuring each distance, the distances are circumscribed outside the movement path of the laser emission point. The movement path of the laser emission point is circular, representing the trajectory of the laser emission point moving around the rotation center. A minimum circumscribed circle, or virtual circle, is constructed for the endpoints of multiple distances far from the rotation center. Within this virtual circle, the angle between any two adjacent virtual half-chords is equal to the ranging rotation angle α. f .

[0090] S33: Calculate the sum of two virtual half-chords spaced 180° apart in a planar coordinate system as a virtual chord. A line segment connecting any two points on a circle is a chord. In a virtual circle, any two virtual half-chords spaced 180° apart can form a virtual chord passing through the center of rotation O2.

[0091] S34: Select the longest virtual chord as the virtual diameter, then the midpoint of the virtual diameter is the virtual center O1. According to the definition of diameter, the line segment connecting any two points inside a circle has the longest diameter and passes through the center of the circle.

[0092] If the minimum number of measurement points is 2m, then each virtual chord is denoted as:

[0093] l i =s i +s i+m +2r(i=1,2,3,...,m).

[0094] Among them, l i For the i-th virtual string, s i Let s be the distance measured when the detector rotates by i ranging angles. i+m The distance measured when the detector rotates i+m distance measuring angles.

[0095] Please combine Figure 3 , it is Figure 1 The distance data graph is obtained when the number of measurement points is 800. In this embodiment, the number of measurement points is recorded as 800, so the angle of rotation of the detector each time is 360° / 800 = 0.45°. The detector acquires a distance between itself and the inner wall of the tube for every 0.45° rotation within the tube, denoted as {A}. n}(n=0, 1, 2, 3, …, 799). The corresponding chord length is denoted as {B}. n}(n=0,1,2,…,399). If the m-th chord is the longest among the 400 chords, then B m That is, the diameter, B mThe virtual circle passes through the center, and its midpoint is the virtual center O1. Then the virtual diameter D and the maximum virtual radius R are expressed as:

[0096] D = B m ,

[0097] R = D / 2.

[0098] S4: Use the law of cosines to calculate the virtual radius corresponding to each virtual half-chord.

[0099] The specific method for calculating the virtual radius is as follows:

[0100] S41: When the virtual half-chord is exactly on the virtual diameter, take half of the virtual diameter as the virtual radius.

[0101] Please combine Figure 4 , it is Figure 1 A schematic diagram of the virtual central angle. (The diagram shows B.) m The chord is defined as the virtual diameter D, the two endpoints of the diameter are denoted as K and K', the end of any virtual half-chord away from the origin is denoted as point P, the angle between the virtual half-chord and the actual inner diameter is denoted as θ, and the angle between the line segment connecting the virtual center O1 and point P and the actual inner diameter is denoted as the virtual central angle β.

[0102] When point P lies exactly on the virtual diameter, the virtual radius O1P is exactly half of the virtual diameter, denoted as:

[0103] O1P=(H K +H K+N ) / 2.

[0104] S42: When the virtual half-chord is not on the virtual diameter, the distance from the endpoint of the virtual radius furthest from the virtual center to the virtual center is calculated using the cosine theorem and taken as the virtual radius.

[0105] When point P is not on the virtual diameter, if 0° < θ < 180°, then in △O1O2P, according to the Law of Cosines, we know that:

[0106]

[0107] Given that R is the largest virtual half-chord, then

[0108] O1O2 = RH k =(H k +H k+n ) / 2-H k .

[0109] The virtual radius can then be expressed as:

[0110]

[0111] Among them, H KH is the distance from O2 to K. K+N H is the distance from O2 to K'. P Let θ be the distance from O2 to P, and θ be the angle between O2P and O2K.

[0112] If 180° < θ < 360°, and the laser beam strikes the inner wall of the tube at point P', then in △O1O2P',

[0113] According to the Law of Cosines:

[0114]

[0115] After sorting, we get:

[0116]

[0117] Since cosπ = -1, therefore

[0118] cos(π-θ)=cos(θ-π)=-cos(θ).

[0119] Therefore, the general formula for calculating the virtual radius over the entire circumference of the measured cross section is as follows:

[0120]

[0121] The virtual diameter is used to characterize the actual manufactured pipe diameter. The difference between the virtual diameter and the ideal value (i.e., the standard inner diameter of the pipe) represents the error present in the actual manufacturing process. The virtual radius can be used to calculate the ellipticity of the pipe and analyze the unevenness of the inner diameter. The virtual radius can also be used to determine the wear condition of the inner wall of the pipe. In practical applications of the testing instrument, the virtual diameter and virtual radius are the main parameters for judging whether the pipe wall is qualified.

[0122] S5: Use the sine theorem to calculate the angle between the virtual diameter and the virtual radius as the corresponding virtual central angle.

[0123] The specific method for calculating the virtual central angle is as follows:

[0124] S51: When the virtual half-chord is exactly on the virtual diameter, the angle between the virtual radius and the virtual diameter is 0° or 180°, and the corresponding virtual central angle is also 0° or 180°.

[0125] S52: When the virtual half-chord is not on the virtual diameter, the virtual central angle is calculated using the sine theorem.

[0126] If 0° < θ < 180°, then in △O1O2P, by the Law of Sines, we can obtain:

[0127]

[0128] Right now

[0129]

[0130] After sorting, we get:

[0131]

[0132] If 180° < θ < 360°, and the laser beam strikes the inner wall of the tube at point P', then in △O1O2P', according to the law of sines:

[0133]

[0134] Right now

[0135]

[0136] After sorting, we get:

[0137]

[0138] After summarizing the above virtual central angle β, we can obtain:

[0139]

[0140] S6: Calculate the actual number of measurement points based on the virtual radius and laser beam diameter. Then, calculate the actual rotation angle measured by the detector for each measurement based on the actual number of measurement points.

[0141] S61: Treat the laser beam diameter as a beam chord in a virtual circle, and calculate the central angle of the beam chord in the virtual circle as the beam central angle.

[0142] Because the rotation axis of the detector may not be collinear with the central axis of the tube during the measurement process, although the diameter of the laser beam remains constant and the arcs covered on the measured cross-section of the tube are approximately equal, the distance between the two measurement points formed by the laser on the inner wall of the tube will still be different in two adjacent measurements. Therefore, in order to ensure that the laser points completely cover the measured cross-section of the tube, it is necessary to first measure the minimum central angle corresponding to the arcs covered by all laser points.

[0143] Please combine Figure 5 , it is Figure 1 A schematic diagram of the central angle of the laser beam. Assume the laser beam diameter is L, the distance from the laser displacement sensor to the measurement point is s, the rotation radius of the laser displacement sensor is r, and the arc covered by the laser beam on the measured cross-section is... Since the value of L approximates a point, △AOB can be considered as an isosceles triangle, with the corresponding leg length being:

[0144] OA=OB≈s+r.

[0145] By the Law of Cosines, in a triangle with side lengths a, b, and c, if the angle opposite to c is C, then:

[0146] cosC=(a 2 +b 2 -c 2 ) / 2ab.

[0147] In triangle AOB, ∠AOB is the central angle θ of the light beam. l , can be expressed as:

[0148] θ l =arccos(((s+r) 2 +(s+r) 2 -L 2 ) / 2(s+r).

[0149] S62: Calculate the number of measurement points required for the laser displacement sensor to cover the entire pipe diameter based on the beam center angle, and use this as the theoretical number of measurement points.

[0150] The measuring range of the detector should cover the entire cross-section being measured; therefore, the theoretical number of measurement points N0 can be expressed as:

[0151] N0≥2π / min(θ l ).

[0152] Wherein, min(θ) l ) is the minimum value among all beam central angles.

[0153] In this embodiment, the diameter of the measured circular cross-section is 120 mm, the beam diameter L is 0.17 mm, and the measurement spacing s ranges from 40 mm to 60 mm. Since the measured circular cross-section is within the sensor's measurement range, we can obtain:

[0154] 50mm≤s+r≤70mm.

[0155] Correspondingly,

[0156] θ l ∈(0.0025,0.0034).

[0157] but

[0158] N0≥2π / min(θ l )≈2520

[0159] Therefore, for a 120mm diameter pipe, theoretically, at least 2520 data points need to be detected at equal angles to achieve full coverage measurement.

[0160] Within the measuring range of the instrument, the theoretical number of measurement points was calculated for multiple pipes of different diameters, and the correspondence between the pipe diameter and the number of measurement points is shown in Table 1.

[0161] Table 1. Correspondence between theoretical pipe diameter and number of measurement points

[0162]

[0163] S63: Set the maximum error distance between any two adjacent detection points. Calculate the number of measurement points required for the detector to measure the complete pipe diameter based on the maximum error distance, and use this as the actual number of measurement points. Then, use the ratio of the circumferential angle to the actual number of measurement points as the actual rotation angle.

[0164] In actual measurements, the more measurement points there are, the longer the total measurement time will be, given a fixed detection time per point. To achieve a balance between scanning cycle and detection accuracy, a maximum error distance δ is set for the distance between two adjacent points on the inner wall of the tube illuminated by the laser in actual measurements. The actual rotation angle θ0 can then be expressed as:

[0165] θ0 = 2π / N1, N1 ≥ 2π / (θ l +θδ)

[0166] θ δ =arccos(((s+r) 2 +(s+r) 2 -δ 2 ) / 2(s+r)

[0167] Where N1 is the actual number of measurement points, δ is the maximum error distance, and θ δ This is the central angle corresponding to the maximum error distance.

[0168] During the barrel inspection process, even very small cracks can block reflected light and cause errors in the data. Therefore, δ = 0.5 mm is set, and the corresponding relationship between the barrel diameter and the number of measurement points is shown in Table 2:

[0169] Table 2 Correspondence between Actual Pipe Diameter and Number of Measurement Points

[0170]

[0171] Considering the accuracy of motor rotation angle in actual measurements, and to improve the detection efficiency of the barrel inner wall while ensuring detection accuracy, 800 points can be selected as the actual measurement points for barrel diameters between 100mm and 155mm. Accordingly, the selected stepper motor should achieve a minimum step angle of 0.45° to achieve a measurement accuracy of 800 steps per revolution.

[0172] S7: Establish a conversion table based on the mapping relationship between the standard pipe diameter and the actual rotation angle. The conversion table is used to represent the one-to-one mapping relationship between pipe diameter, number of measurement points, and measurement rotation angle.

[0173] In addition to indicating the minimum number of measurement points and the maximum measurement angle corresponding to the standard pipe diameter, the conversion table should also specify the measuring range of the measuring instrument. The measuring range of the measuring instrument is related to its rotation radius and minimum rotation angle, and must meet the accuracy requirements for pipe diameter measurement. The measuring range of the measuring instrument should not be less than its rotation radius to allow it to be placed inside the pipe and complete the laser scan of the inner wall. The minimum rotation angle of the measuring instrument should not be greater than the central angle corresponding to the pipe diameter cross-section circle when the laser beam diameter is taken as the chord length.

[0174] The detection range of the detector is determined based on its minimum rotation angle. The detection range [D1, D2] can be expressed as:

[0175]

[0176] Where γ is the minimum rotation angle of the detector.

[0177] The testing method of the pipe diameter laser scanning detector provided in this embodiment obtains the measuring angle by using the standard diameter of the pipe, and then measures the entire circular cross-section covering the inner wall of the pipe by rotating at equal angles to obtain the complete cross-sectional diameter. Then, based on the minimum central angle formed by the laser beam on the pipe wall during actual measurement, the minimum number of measurement points required to measure the entire circular cross-section of a pipe with a given diameter is obtained. Due to the limitations of existing processes and the allowable inner diameter errors in actual pipe applications, it is not necessary to completely measure the circular cross-section during measurement. To meet the requirements of accuracy and efficiency in detection, a maximum measurement error is introduced when calculating the actual number of measurement points, resulting in the minimum number of measurement points required while maintaining detection accuracy, thus improving the efficiency of pipe inner wall detection.

[0178] Example 2

[0179] Please combine Figure 6 and Figure 7 , Figure 6 This is a three-dimensional structural diagram of the laser scanning detector for the inner diameter of the tube in this embodiment; Figure 7 for Figure 6 A schematic diagram of the structure of a laser scanning detector for the inner diameter of a pipe. This embodiment provides a laser scanning detector for the inner diameter of a pipe used in this embodiment. The laser scanning detector for the inner diameter of a pipe includes a laser rangefinder 1, a rotating mechanism 2, a shaft 4, a positioning device 3, a controller 5, a display device (not shown), and an operation panel (not shown).

[0180] The laser rangefinder 1 is used to emit a laser detection signal and measure the distance between itself and the target object by receiving the echo signal scattered by the target object. The laser rangefinder 1 includes a laser emitter and an optical sensor. The laser emitter emits the laser detection signal. The optical sensor receives the laser echo signal and records the time elapsed from laser emission to laser reception, and then calculates the distance between the target object and the laser rangefinder 1 based on the angle and duration of the received echo signal.

[0181] The laser rangefinder sensor 1 can be a triangular reflective displacement sensor, such as the ILD1420 sensor, with a detection range of 50mm to 150mm and a repeatability of 4μm. The ILD1420 sensor is suitable for temperatures ranging from -20℃ to 50℃, meeting the detection requirements for pipe diameters from 100mm to 155mm. Triangular reflective displacement sensors offer higher accuracy and faster detection efficiency, effectively improving measurement efficiency while ensuring measurement accuracy.

[0182] Laser rangefinder 1 can also be equipped with an industrial-grade high-precision rangefinder. Compared with the triangular reflective displacement sensor, the industrial-grade high-precision rangefinder has a larger range, but its accuracy is only 1.0 mm, which is suitable for the detection of pipes with larger diameters.

[0183] Please combine Figure 8 , it is Figure 6 A three-dimensional structural diagram of the rotating mechanism is shown. The rotating mechanism 2 is fixedly connected to the laser rangefinder 1 and is used to drive the laser rangefinder 1 to rotate according to a predetermined ranging angle. During the measurement of the inner diameter of the tube, since it is difficult to directly measure the tube diameter, the detector in this embodiment uses circumferential measurement of the inner diameter of the tube, and then analyzes and calculates based on the multiple measured data to obtain the actual size of the inner diameter of the tube. To ensure measurement accuracy, the error between two consecutive measurement points must not exceed a preset maximum error value. Therefore, the detector in this embodiment uses an equal-angle measurement method to complete the circumferential detection of the tube cross-section. To meet measurement accuracy, the rotating mechanism 2 uses a stepper motor 21 to drive the laser rangefinder 1 to rotate. Specifically, the rotating mechanism 2 includes a stepper motor 21, a cantilever 22, and a conductive slip ring 23.

[0184] One side of the cantilever 22 is fixedly connected to the laser rangefinder 1, and the other side is fixedly connected to the output shaft of the stepper motor 21. The cantilever 22 can be plate-shaped, such as a square or round plate, used to mount the laser rangefinder 1 on the stepper motor 21, ensuring that the laser emission direction of the laser rangefinder 1 is always perpendicular to the rotation axis of the stepper motor 21. The rotation axis of the stepper motor 21 is set to be parallel to the central axis of the tube, thereby controlling the laser emission direction of the laser rangefinder 1 to always be perpendicular to the central axis of the tube, thus detecting the entire circular cross-section of the tube and reducing detection errors. The stepper motor 21 can rotate a fixed angle according to the input control signal, and then calculates the angle of each rotation according to the preset number of measurement points, driving the laser rangefinder 1 to rotate by one ranging angle each time, and measuring the corresponding distance. In this embodiment, the minimum step angle of the stepper motor 21 is 0.45°, which can meet the detection requirements of 800 detection points, thus meeting the detection requirements of tubes with a diameter of 100mm to 155mm. The stepper motor 21 can be a 42BYGH3413B4K type hollow shaft stepper motor 21, with an output shaft outer diameter of 10mm and a front shaft length of 25mm. Of course, in other embodiments, stepper motors 21 with other signals can also be selected, as long as they can meet the measurement requirements of the minimum step angle.

[0185] One end of the conductive slip ring 23 is fixedly connected to the cantilever 22, and the other end is fixedly connected to the stepper motor 21. The input end of the conductive slip ring 23 is connected to the laser rangefinder 1, and the output end is connected to the controller 5. The conductive slip ring 23 not only transmits the power output from the stepper motor 21, indirectly controlling the rotation of the laser rangefinder 1, but also transmits the signal detected by the laser sensor to the controller 5.

[0186] The laser rangefinder 1 requires not only its own power supply but also signal communication with the controller 5. Therefore, in practical applications, the laser rangefinder 1 needs to maintain a continuous connection with the controller 5. If a wire is used for this connection, the wire will rotate with the stepper motor 21, potentially becoming entangled on the output shaft of the stepper motor 21, causing signal interference or even damage to the wire. The conductive slip ring 23, also known as a conductive ring, current collector ring, or current bus ring, uses built-in brushes to ensure that the outer ring is fixedly connected to the stepper motor 21 while the inner shaft rotates, maintaining conductivity between the outer ring and the inner shaft. By using the conductive slip ring 23, the laser rangefinder 1 remains connected to the controller 5 throughout its rotation, maintaining stable signal transmission. A six-channel miniature conductive slip ring 23 can be used, offering high insulation, and the wire length can be customized to meet precise pipe diameter requirements. Of course, in other embodiments, other types of conductive slip rings 23 can also be selected, such as LPM-12U miniature cap-type conductive slip rings, etc.

[0187] Please combine Figure 9 and Figure 10 , Figure 9 for Figure 8 A cross-sectional schematic diagram of the rotating mechanism; Figure 10 for Figure 6 A three-dimensional structural diagram of the positioning device. The positioning device 3 is slidably connected to the shaft 4, supporting the shaft 4 and ensuring that the shaft 4 is always parallel to the central axis of the tube. The positioning device 3 includes a positioning cylinder 31, an umbrella-shaped bracket 33, the shaft 4, and a nut 34. The shaft 4 is fixedly connected to the stepper motor 21, and the shaft 4 is parallel to the rotation axis of the stepper motor 21. In practical applications, the detector may need to detect different depths inside the tube separately. By driving the motor through the shaft 4 to translate, the laser rangefinder 1 can be moved to the position to be measured inside the tube, or multiple different positions inside the tube can be detected to improve the accuracy of the tube's inner diameter detection. It is important to note that the shaft 4 should always remain parallel to the central axis of the tube during the driving process.

[0188] The positioning cylinder 31 is coaxially arranged with the shaft 4 and slidably connected to the outside of the shaft 4 to achieve a sliding connection between the positioning device 3 and the rotating mechanism 2. One end of the umbrella-shaped bracket 33 is rotatably connected to one end of the positioning cylinder 31, and the other end abuts against the nut 34. The other end of the positioning cylinder 31 is provided with an external thread for screwing the nut 34.

[0189] The positioning cylinder 31 is a cylinder with uniform thickness and a smooth surface. The shaft 4 can slide smoothly inside the positioning cylinder 31. The end of the umbrella-shaped bracket 33 that is pressed against the nut 34 can also slide smoothly outside the positioning cylinder 31. When the nut 34 rotates clockwise outside the positioning cylinder 31, it can drive the umbrella-shaped bracket 33 to open outward, thereby fixing the positioning cylinder 31 inside the tube. When the nut 34 rotates counterclockwise, the umbrella-shaped bracket 33 is reset by elastic force, and the positioning device 3 can be removed from the tube.

[0190] To reduce wear during the opening and closing of the umbrella bracket 33, a spring 32 can be installed between the umbrella bracket 33 and the nut 34. The spring 32 is coaxially positioned on the outside of the positioning cylinder 31, with one end abutting against the umbrella bracket 33 and the other end abutting against the nut 34. The spring 32 transforms the rigid contact between the nut 34 and the umbrella bracket 33 into a flexible contact. This avoids direct wear when the nut 34 abuts against the umbrella bracket 33, and simultaneously converts the driving force of the nut 34 into the elastic force of the spring 32, acting as a buffer between the nut 34 and the umbrella bracket 33. This ensures the umbrella bracket 33 maintains its installation stability while preventing damage caused by rigid contact, thereby extending the service life of the umbrella bracket 33.

[0191] The positioning cylinder 31, nut 34, spring 32, and umbrella-shaped bracket 33 can be made of metal, plastic, or wood. To ensure the accuracy of the detection and reduce wear between the positioning device 3 and the cylinder during the measurement process, this embodiment uses a positioning cylinder 31, nut 34, spring 32, and umbrella-shaped bracket 33 made of stainless steel.

[0192] The umbrella-shaped support 33 includes a slip ring (not shown) and multiple folding triangular rods. The slip ring is slidably connected to the positioning cylinder 31 and abuts against the spring 32. The multiple folding triangular rods are arranged alternately in opposite directions and are evenly distributed on the outside of the positioning cylinder 31. Each folding triangular rod has one end rotatably connected to the slip ring and the other end rotatably connected to the positioning cylinder 31. The straight lines containing the two ends of each folding triangular rod are always parallel to the central axis of the positioning cylinder 31. Furthermore, the plane containing each folding triangular rod passes through the central axis of the positioning cylinder 31.

[0193] The folding triangular rod includes a long rod 332 and a short rod 331. The long rod 332 and the short rod 331 are rotatably connected to each other. In half of the folding triangular rods, one end of the long rod 332 is rotatably connected to one end of the positioning cylinder 31, and the other end of the long rod 332 is rotatably connected to one end of the short rod 331. The other end of the short rod 331 is rotatably connected to the slip ring. In the other half of the folding triangular rods, one end of the long rod 332 is rotatably connected to the slip ring, and the other end of the long rod 332 is rotatably connected to the short rod 331. The other end of the short rod 331 is rotatably connected to the positioning cylinder 31. When the umbrella-shaped bracket 33 opens outward, multiple folding triangular rods open outward, forming multiple support points equidistant from the central axis of the positioning cylinder 31. Because the folding triangular rods are alternately arranged in opposite directions, the multiple support points can form two sets of parallel and rotationally symmetrical equilateral polygons, thereby forming two expansion supports on the outside of the positioning cylinder 31, thus supporting the positioning cylinder 31 so that the positioning cylinder 31 is coaxial with the tube body to be tested. When the umbrella-shaped bracket 33 is folded inward, the connection between the long rod 332 and the short rod 331 moves closer to the outer wall of the positioning cylinder 31 and maintains a preset distance gap with the positioning cylinder 31 to avoid the long rod 332 and the short rod 331 being on the same straight line, so as to facilitate the folding triangular rod to open outward.

[0194] The long rod 332 and the short rod 331 are rotatably connected via a pin 334 and a pulley 333. Specifically, each of the long rod 332 and the short rod 331 has a U-shaped end, with the U-shaped end of the short rod 331 positioned outside the U-shaped end of the long rod 332. The pin 334 is fixedly connected to the U-shaped end of the short rod 331 and rotatably connected to the U-shaped end of the long rod 332, thus achieving the rotatable connection between the long rod 332 and the short rod 331. To prevent wear between the long rod 332 or the short rod 331 and the inner wall of the tube when the folding triangular rod is opened outward, a pulley 333 is rotatably connected to the outside of the pin 334. The pulley 333 is positioned inside the U-shaped end of the long rod 332. The central axis of the pulley 333 is perpendicular to the folding triangular rod it is attached to, and the outer diameter of the pulley 333 is greater than the thickness of the U-shaped ends of the long rod 332 and the short rod 331. By setting pulley 333, when the umbrella-shaped bracket 33 retracts inward, pulley 333 first contacts the positioning cylinder 31, ensuring that the angle between the long rod 332 and the short rod 331 is always less than 180°, facilitating the opening of the folding triangular rod. When the umbrella-shaped bracket 33 opens outward, pulley 333 first contacts the inner wall of the tube, preventing wear between the long rod 332 or the short rod 331 and the inner wall of the tube. Furthermore, pulley 333 can rotate outside the pin 334, avoiding rigid contact with the inner wall of the tube, reducing its own wear, and extending the service life of the umbrella-shaped bracket 33.

[0195] By installing the positioning device 3, the shaft 4 can slide stably inside the positioning cylinder 31. Thus, when the driving rotating mechanism 2 is translated, the rotation axis of the shaft 4 and the rotating mechanism 2 is always parallel to the central axis of the tube, so that the laser emission direction of the laser range sensor 1 is always perpendicular to the central axis of the tube, thereby improving the accuracy of the tube's inner diameter measurement.

[0196] Controller 5 processes the signals transmitted by laser rangefinder 1 and controls the operating state of rotating mechanism 2. Specifically, controller 5 is used for:

[0197] a. Obtain the corresponding ranging angle from the standard inner diameter of the pipe to be measured using a conversion table. The conversion table represents the mapping relationship between the standard inner diameter and the ranging angle.

[0198] The tube body is generally designed with a standard diameter during manufacturing, which is the ideal diameter for the tube body. Based on the rotation radius of the laser rangefinder 1, the ranging angle corresponding to measuring tube bodies of different diameters can be calculated, thereby improving detection efficiency while ensuring measurement accuracy.

[0199] b. Based on the ranging angle, control the rotation mechanism 2 to drive the laser ranging sensor 1 to rotate one revolution, and obtain the distance measured after each ranging angle rotation of the laser ranging sensor 1. The distance is the distance from the laser ranging sensor 1 to the inner wall of the tube in the laser emission direction.

[0200] Assuming the ranging angle is θ0, the rotating mechanism 2 drives the laser ranging sensor 1 to rotate by θ0 each time, detecting a total of 2π / θ0 distance signals.

[0201] c. Based on the rotation radius of laser rangefinder 1, the spacing is mapped onto a planar coordinate system to form multiple line segments. The distance between the line segment and the origin is equal to the rotation radius, and the angle between the line segment and the positive direction of the horizontal axis of the coordinate system is equal to the angle between the laser direction and the initial laser direction when measuring the corresponding spacing.

[0202] d. Construct the minimum circumcircle for multiple line segments as a virtual circle, calculate the diameter of the virtual circle as the actual inner diameter, and calculate the distance between the end of each line segment furthest from the center of the virtual circle and the center of the virtual circle as the virtual radius.

[0203] Assuming the radius of rotation is r, the measured distance is denoted as A. i (i = 1, 2, 3, ..., n), taking the sum of each spacing and the rotation radius as a virtual half-chord, the virtual half-chord can be expressed as:

[0204] C i =A i +r, (i=1,2,3,...,n).

[0205] If we take the sum of two virtual half-chords that are 180° apart as the virtual chord, then virtual chord B... i It can be represented as:

[0206] B i =C i +C i+180 .

[0207] As defined by diameter, the longest line segment connecting any two points within a circle has a diameter that passes through the center of the circle. In this embodiment, the number of measurement points is recorded as 800, so the stepper motor rotates by an angle of 360° / 800 = 0.45° each time. The detector obtains a distance between itself and the inner wall of the tube for every 0.45° rotation within the tube, denoted as {A}. n}(n=0, 1, 2, 3, …, 799). The corresponding chord length is denoted as {B}. n}(n=0,1,2,…,399). If the m-th chord is the longest among the 400 chords, then B m That is, the diameter, B m Passing through the center of the circle, the actual inner diameter D can be expressed as:

[0208] D = B m .

[0209] The specific method for calculating the virtual radius is as follows:

[0210] When the virtual half-chord is exactly on the actual inner diameter, half of the actual inner diameter is taken as the virtual radius.

[0211] B m The chord is defined as the actual inner diameter D, the two endpoints of the actual inner diameter are denoted as K and K', the end of any virtual half-chord away from the origin is denoted as point P, the angle between the virtual half-chord and the actual inner diameter is denoted as θ, and the angle between the line segment connecting the virtual center O1 and point P and the actual inner diameter is denoted as the virtual central angle β.

[0212] When point P lies exactly on the actual inner diameter, the virtual radius O1P is exactly half of the actual inner diameter, denoted as:

[0213] O1P=(H K +H K+N ) / 2.

[0214] When the virtual half-chord is not on the actual inner diameter, the distance from the endpoint furthest from the virtual center to the virtual center is calculated using the cosine theorem and taken as the virtual radius.

[0215] When point P is not on the actual inner diameter, if 0° < θ < 180°, then in △O1O2P, according to the Law of Cosines, we know that:

[0216]

[0217] Given that R is the largest virtual half-chord, then

[0218] O1O2 = RH k =(H k +H k+n ) / 2-H k .

[0219] The virtual radius can then be expressed as:

[0220]

[0221] Among them, H K H is the distance from O2 to K. K+N H is the distance from O2 to K'. P Let θ be the distance from O2 to P, and θ be the angle between O2P and O2K.

[0222] If 180° < θ < 360°, and the laser beam strikes the inner wall of the tube at point P', then in △O1O2P',

[0223] According to the Law of Cosines:

[0224]

[0225] After sorting, we get:

[0226]

[0227] Since cosπ = -1, therefore

[0228] cos(π-θ)=cos(θ-π)=-cos(θ)

[0229] Therefore, the general formula for calculating the virtual radius over the entire circumference of the measured cross section is as follows:

[0230]

[0231] e. Determine whether the actual inner diameter and the virtual radius exceed the preset threshold range. If yes, output an unqualified signal; otherwise, output a qualified signal.

[0232] The preset threshold ranges include a threshold range for the actual inner diameter and a threshold range for the virtual radius. The threshold range for the actual inner diameter can be set based on the standard inner diameter of the tube being tested, such as not exceeding 1% of the standard inner diameter. The threshold range for the virtual radius can also be set based on the actual inner diameter, such as not exceeding 1% of the actual inner diameter. Of course, in other embodiments, the threshold ranges for both the actual inner diameter and the virtual radius can be larger or smaller.

[0233] When manually measuring the inner wall of a pipe, it is necessary not only to control the motor to run at a fixed angle each time and record the data detected by the laser rangefinder 1 in real time, but also to calculate the actual inner diameter and virtual radius of the pipe based on a large amount of data, and then determine whether the pipe meets the preset standards. Manual measurement is not only difficult to control the accuracy of the measurement, but also has a relatively large amount of operation and calculation, resulting in low detection efficiency. Existing equipment that observes the wear condition of the inner wall by imaging the inner wall of the pipe and then using image recognition methods is not only difficult to detect the actual inner diameter, but also difficult to distinguish the concave and convex positions of the pipe wall because the color of the inner wall of the pipe is almost unchanged, resulting in low detection accuracy.

[0234] The operation panel is connected to controller 5. The operation panel is used to input control commands or data to controller 5. The data includes the standard inner diameter and threshold range of the tube to be tested. In actual testing, the operator can control the testing instrument through the operation panel, such as inputting the standard inner diameter of the tube to be tested and the rotation radius of the testing instrument. The operator can also control the rotating mechanism 2 through the operation panel, such as controlling its start / stop or rotation angle.

[0235] The display device is connected to the controller 5. The display device shows the actual inner diameter and virtual radius values ​​obtained after each step is executed by the controller 5. It also displays the pass / fail signals output by the controller 5. To facilitate real-time observation of the measured pipe inner diameter data by the operator, multiple data points obtained during the measurement process can be displayed on the display device, such as the distance detected in real-time by the laser rangefinder 1, and the calculated actual and virtual inner diameters. The display device can be a display screen or other electronic products with display functions.

[0236] In this embodiment, the laser scanning detector controller 5 automatically measures the pipe diameter. Based on the standard inner diameter of the pipe to be measured, it controls the rotating mechanism 2 to drive the laser ranging sensor 1 to rotate according to the corresponding ranging angle, thereby measuring the distance between the laser ranging sensor 1 and the inner wall of the pipe. Based on the measured distance and the rotation radius of the laser ranging sensor 1, it calculates the actual inner diameter and virtual radius of the pipe, and then determines whether the pipe diameter exceeds a preset threshold range. This not only improves the accuracy of pipe diameter detection, but also improves detection efficiency.

[0237] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0238] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A testing method for a pipe diameter laser scanning detector, characterized in that, It is used to determine the maximum actual rotation angle of signal scanning under different tube diameter conditions, while achieving a balance between scanning cycle and detection accuracy; the test method includes the following steps: S1: Calculate the minimum number of measurement points required to cover the entire inner circumference of the pipe body based on the standard pipe diameter and the laser beam diameter of the detector; then calculate the measuring angle of the detector; the minimum number of measurement points N is: Where N is an even number, α is the central angle corresponding to the laser beam diameter being a chord of the tube's cross-sectional circle, L is the laser beam diameter, and R0 is the standard inner radius of the tube. The ranging angle α f for: α f ＝2π / N； S2: The detector rotates one revolution along the cross-section of the pipe diameter inside the pipe according to the distance measuring angle; the detector measures the distance s between itself and the inner wall of the pipe every time it rotates one distance measuring angle and records the number of rotations c. S3: Obtain the rotation radius r of the detector, construct a virtual circle based on the spacing s, the rotation radius r, and the number of rotations, and determine the center of the virtual circle. The specific method is as follows: S31: Add the radius of rotation to each measured interval as a virtual half-chord; S32: Map the virtual half-strings to a planar coordinate system based on the chord length of each virtual half-string and the number of rotations; wherein the starting point of each virtual half-string is located at the origin O2; the angle between any two adjacent virtual half-strings is equal to the ranging rotation angle α. f ; S33: Calculate the sum of two virtual half-chords spaced 180° apart in the plane coordinate system as a virtual chord; S34: Select the virtual chord with the longest length as the virtual diameter, and the midpoint of the virtual diameter is the virtual center O1; S4: Calculate the virtual radius corresponding to each virtual half-chord using the law of cosines; assuming the two endpoints of the virtual diameter are denoted as K and K', and the endpoint of any virtual half-chord furthest from the virtual center is P, then the virtual radius O1P is expressed as: Among them, H K H is the distance from O2 to K. K+N H is the distance from O2 to K'. P Let θ be the distance from O2 to P, and θ be the angle between O2P and O2K. S5: The angle between the virtual diameter and the virtual radius is calculated using the sine theorem and taken as the corresponding virtual central angle; then the virtual central angle β is expressed as: S6: Calculate the actual number of measurement points based on the virtual radius and the laser beam diameter; then calculate the actual rotation angle measured by the detector each time based on the actual number of measurement points; the actual rotation angle θ0 is then expressed as: Where N1 is the actual number of measurement points, θ l θ is the central angle of the laser beam corresponding to its diameter. δ The central angle corresponding to the maximum error distance; S7: Establish a conversion table based on the mapping relationship between the standard pipe diameter and the actual rotation angle; the conversion table is used to characterize the one-to-one mapping relationship between the pipe diameter, the number of measurement points, and the measurement rotation angle.

2. The testing method of the tube diameter laser scanning detector according to claim 1, characterized in that, In S33, assuming the minimum number of measurement points is 2m, each virtual chord is denoted as: l i =s i +s i+m +2r(i=1,2,3,……,m); Among them, l i For the i-th virtual string, s i Let s be the distance measured when the detector rotates by i ranging angles. i+m The distance measured when the detector rotates i+m distance measuring angles.

3. The testing method of the tube diameter laser scanning detector according to claim 1, characterized in that, In S4, the virtual radius is calculated as follows: S41: When the virtual half-chord is exactly located on the virtual diameter, take half of the virtual diameter as the virtual radius; S42: When the virtual half-chord is not on the virtual diameter, the distance from the endpoint of the virtual radius away from the virtual center to the virtual center is calculated using the cosine theorem and taken as the virtual radius.

4. The testing method of the tube diameter laser scanning detector according to claim 1, characterized in that, In S5, the method for calculating the virtual central angle is as follows: S51: When the virtual half-chord is exactly located on the virtual diameter, the angle between the virtual radius and the virtual diameter is 0° or 180°, and the corresponding central angle is also 0° or 180°. S52: When the virtual half-chord is not on the virtual diameter, the central angle is calculated using the sine theorem.

5. The testing method of the tube diameter laser scanning detector according to claim 1, characterized in that, In S6, the method for calculating the actual rotation angle is as follows: S61: Treat the laser beam diameter as a beam chord in a virtual circle, and calculate the central angle of the beam chord in the virtual circle as the beam central angle; S62: Calculate the number of measurement points required for the laser displacement sensor to cover the entire pipe diameter based on the central angle of the beam, and use this as the theoretical number of measurement points; S63: Set the maximum error distance between any two adjacent detection points; calculate the number of measurement points required for the detector to measure the diameter of the complete pipe body based on the maximum error distance as the actual number of measurement points, and then use the ratio of the circumferential angle to the actual number of measurement points as the actual rotation angle.

6. The testing method of the tube diameter laser scanning detector according to claim 5, characterized in that, In S61, assuming the laser beam diameter is L, the distance from the laser displacement sensor to the measurement point is s, and the rotation radius of the laser displacement sensor is r, then the central angle of the laser beam is expressed as: θ l =arccos(((s+r) 2 +(s+r) 2 -L 2 ) / 2(s+r)。 7. The testing method of the tube diameter laser scanning detector according to claim 5, characterized in that, In S62, the theoretical number of measurement points N0 is expressed as: N0≥2π / min(θ l ); Wherein, min(θ) l ) is the minimum value among all beam central angles.

8. The testing method of the tube diameter laser scanning detector according to claim 5, characterized in that, In S63, the central angle corresponding to the maximum error distance is expressed as: i δ =arccos{[2(s+r) 2 -d 2 ] / 2(s+r)}; Where δ is the maximum error distance.

9. The testing method of the tube diameter laser scanning detector according to claim 5, characterized in that, In S63, let N be the number of measurement points supported by the detector. M (M = 2, 4, 6, ...), then the actual number of measurement points N1 is expressed as: Where N1 is an even number, N Mi N represents the number of measurement points supported by the i-th detector. M(i-1) This represents the number of measurement points supported by the (i-1)th detector.

10. The testing method of the tube diameter laser scanning detector according to claim 1, characterized in that, In S7, the detection range of the detector is determined based on the minimum rotation angle of the detector. Therefore, the detection range [D1, D2] of the detector is expressed as: Where γ is the minimum rotation angle of the detector.

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