CN115046474B - System and method for measuring inner and outer surfaces of tubular part - Google Patents
System and method for measuring inner and outer surfaces of tubular part Download PDFInfo
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- CN115046474B CN115046474B CN202210553371.7A CN202210553371A CN115046474B CN 115046474 B CN115046474 B CN 115046474B CN 202210553371 A CN202210553371 A CN 202210553371A CN 115046474 B CN115046474 B CN 115046474B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2408—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures for measuring roundness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
- G01B11/27—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/30—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces
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- Length Measuring Devices By Optical Means (AREA)
Abstract
The invention discloses a system and a method for measuring the inner and outer surfaces of a tubular part, wherein the system comprises: a probe assembly and a probe adjustment mechanism; the probe assembly is used for measuring the inner surface and the outer surface of the tubular piece based on the optical fiber white light interferometry principle; the probe adjusting mechanism is used for adjusting the position of the probe assembly and is connected with the extension plate; the extension plate is connected with the z-direction displacement platform, and the z-direction displacement platform drives the probe assembly to move along the positive and negative directions of the z axis by driving the extension plate; the tubular member is clamped by a chuck; the chuck is connected with the rotary table and the x-direction displacement table in sequence. The method comprises the steps of firstly, calibrating an absolute reference of an optical system, adjusting a light path and calibrating before measurement to obtain a compensation value, keeping a probe adjusting mechanism still after calibration, scanning and measuring a tubular part, compensating a measurement result according to the compensation value to generate a three-dimensional point cloud data sequence of the tubular part, and analyzing to obtain measurement data.
Description
Technical Field
The invention belongs to the technical field of precision measurement, and particularly relates to a system and a method for measuring the inner and outer surfaces of a tubular part.
Background
In equipment or systems with high precision in the fields of national defense, aerospace, medicine, optics and the like, tubular parts with high machining precision generally exist, and the appearance of the inner surface and the outer surface of the tubular parts can greatly influence the performance of the systems in many cases. The method has the advantages that the inner surface and the outer surface of the tubular part are accurately and stably measured, whether the machining precision of the part reaches the standard or not can be effectively determined, the method is also the basis for improving the machining precision, and the method has important significance for the precision machining of the tubular part.
In the tubular member inner and outer surface measuring system adopting the tubular member rotating form, the eccentricity among the axis of the tubular member, the rotary axis of the rotary table and the axis of the probe and the like can cause measuring errors, so that the measuring errors are compensated by a simple, convenient and efficient method in combination with the structural characteristics of the rotary member, and the measuring system has important value in improving the measuring accuracy of the inner and outer surfaces of the tubular member.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a system and a method for measuring the inner and outer surfaces of a tubular part.
In order to achieve the technical purpose, the technical scheme of the invention is as follows: a first aspect of an embodiment of the present invention provides a system for measuring inner and outer surfaces of a tubular member, including: a probe assembly and a probe adjustment mechanism; the probe assembly is based on the optical fiber white light interferometry principle, collimates light beams input by an optical fiber, deflects the collimated light beams by 90 degrees, focuses the collimated light beams and then emits the collimated light beams to the inner surface or the outer surface of the tubular part, and feeds optical signals carrying optical path information back to a white light interferometer for processing to obtain distance information so as to finish measurement of the inner surface and the outer surface of the tubular part; the probe adjusting mechanism is used for adjusting the position of the probe assembly and is connected with the extension plate; the extension plate is connected with the z-direction displacement table, and the z-direction displacement table drives the probe assembly to move along the positive and negative directions of the z axis by driving the extension plate; the tubular member is clamped by a chuck; the chuck is connected with the rotary table and the x-direction displacement table in sequence.
Furthermore, the probe adjusting mechanism comprises a manual rotating table, a manual translation table, a manual angle swinging device, a support rod and a rotary mounting seat which are sequentially connected; the rotary mounting seat is connected with the probe assembly; the manual rotating platform is connected with the extension plate.
Further, the coarse adjustment range of the manual rotating table is 360 degrees, the fine adjustment range is +/-3 degrees, and the fine adjustment precision is +/-5'; the stroke of the manual translation stage is +/-6.5 mm, the straightness is 5 micrometers, and the adjustment precision is 10 micrometers; the adjusting range of the manual angle swinging device is +/-7 degrees, and the adjusting precision is 0.1 degree; the coarse adjustment range of the rotary mounting seat is 360 degrees, the fine adjustment range is +/-7 degrees, and the fine adjustment precision is 10 degrees.
Furthermore, the probe assembly, the adjusting mechanism and the extension plate are in a shape of Jiong; the cross section of the extension plate is I-shaped; the z-direction displacement platform is an air-floating guide rail displacement platform; the rotary table is an air-float rotary table.
A second aspect of the embodiments of the present invention provides a method for measuring inner and outer surfaces of a tubular member, which is applied to the system for measuring inner and outer surfaces of a tubular member, and the method includes the following steps:
s1, calibrating an absolute reference of an optical system in a probe assembly;
s2, utilizing the calibration ring gauge to adjust a light path and calibrate before measurement, measuring to obtain a three-dimensional point cloud data sequence of the calibration ring gauge, performing least square fitting on the generated three-dimensional point cloud data sequence of the calibration ring gauge to obtain a fitting cylinder diameter, and taking the difference value between the fitting cylinder diameter and a nominal value of the ring gauge as a compensation value;
and S3, actually measuring the inner and outer surfaces of the tubular part of the measured part, compensating the measured value by using the compensation value obtained in the step S2, generating three-dimensional point cloud data of the tubular part, and performing fitting analysis on the three-dimensional point cloud data to obtain form and position tolerance and surface roughness.
Further, the step S1 specifically includes: and measuring the inner cylindrical surface under the condition that the axial line of the probe and the axial line of the inner cylindrical surface with the accurately calibrated inner diameter keep higher coaxiality, recording the grating ruler reading of the scanning displacement table corresponding to the envelope peak value of the interference signal, wherein the reading position corresponds to the radius of the inner cylindrical surface, and the subsequent measurement value takes the radius value as the reference.
Further, the step S2 specifically includes the following sub-steps:
s201: returning all manual adjusting tables of the probe adjusting mechanism to zero;
s202: clamping the calibration ring gauge by using a chuck, and controlling a z-direction displacement table and an x-direction displacement table to enable a central point O of the probe assembly 1 At a cross-sectional position substantially in the ring gauge in the z-direction, such that the point O 1 The distance of the inner surface of the ring gauge is equal to the effective focal length of the probe;
s203: the light emitting direction of the probe is adjusted by adjusting a manual rotating table, a manual translation table and a manual angle swinging device, the ring gauge is measured based on an optical fiber white light interference measurement technology, meanwhile, the light intensity value of a light beam returned by a measuring arm is monitored, the light intensity value reaches a threshold value which can be matched with the light intensity value of a reference arm, and the position of the maximum light intensity value is found as far as possible;
s204: finely adjusting the rotary mounting seat, and observing a distance value measured by a measuring system for the inner surface and the outer surface of the tubular part until the minimum distance is found;
s205: setting the height positions of the beginning and the end of scanning measurement and the rotating speed of the rotary table, controlling the simultaneous movement of the z-direction displacement table and the rotary table, and performing spiral scanning measurement on the inner surface of the ring gauge;
s206: in scanning measurement, a measurement distance s value, a z-direction displacement table position value and a rotary table rotation angle value are collected, and the point cloud data is generated in the following mode: taking a z-direction displacement table position value at a certain moment as a z coordinate, decomposing the measured distance into an x coordinate and a y coordinate by using a rotary table rotation angle value at the corresponding moment, obtaining the absolute position of one point in the point cloud data in the space, and carrying out the same processing on the data collected at different moments to obtain the three-dimensional point cloud data of the inner cylindrical surface of the calibration ring gauge;
s207: and performing least square fitting on the generated calibration ring gauge point cloud data to obtain the diameter of a fitting cylinder, wherein the difference between the diameter and the nominal value of the ring gauge is a compensation value.
Further, the step S3 includes the following substeps:
s301: clamping the tubular member in a suitable height position with a chuck; the movement of the z-direction displacement table and the x-direction displacement table is controlled to enable a center point O in the probe assembly to move 1 The distance to the inner surface or the outer surface of the tubular member is within the effective measuring range of the probe;
s302: setting the height positions of the beginning and the end of scanning measurement and the rotating speed of the rotary table, controlling the z-direction displacement table and the rotary table to move simultaneously, and performing scanning measurement on the inner surface or the outer surface of the tubular part; compensating the measured value by using the compensation value obtained in the step S2 to obtain three-dimensional point cloud data of the tubular part;
s303: and performing fitting analysis on the three-dimensional point cloud data of the tubular piece to obtain form and position tolerance and surface roughness.
Further, the scanning measurement in step S302 is a helical scanning measurement, a circular scanning measurement or a linear scanning measurement.
Further, in the step S303, for a portion of the geometric profile of the measured surface close to the profile surface of the standard geometric body, the point cloud data may be subjected to least square fitting by using standard geometric features including a circle, a cylinder, and a cone; then quickly measuring and evaluating form and position tolerance and surface roughness which need to be known; for a measured piece with complex inner and outer surface topography characteristics including threads and rifles, point cloud data are triangulated, and then size parameters needing to be known are measured.
The invention has the beneficial effects that: the invention provides a system and a method for measuring the inner and outer surfaces of a tubular piece, which are based on the principle of optical fiber white light interferometry, realize single-point absolute distance measurement through a probe assembly on the basis of a rapid and convenient method for calibrating the absolute reference of an optical system, expand single-point scanning to three-dimensional scanning with the assistance of an x-direction displacement table, a z-direction displacement table and a turntable, realize multi-mode scanning measurement of the inner and outer surface appearances of the tubular piece and construct three-dimensional point cloud data, provide a pre-measurement calibration method based on a calibration ring gauge, realize compensation of measurement errors, extract and evaluate form and position tolerances and the like of the tubular piece according to the point cloud data, and improve the measurement efficiency and the measurement precision of the inner and outer surfaces of the tubular piece.
Drawings
FIG. 1 is a schematic mechanical diagram of a system for measuring the inner and outer surfaces of a tubular member;
FIG. 2 is a schematic diagram of probe pose adjustment;
FIG. 3 is a top view of the measured conditions of the inner and outer surfaces;
FIG. 4 is a schematic view of a helical scan measurement of the inner surface of a tubular member;
FIG. 5 is a schematic illustration of a circular scan measurement of the inner surface of a tubular member;
fig. 6 is a schematic view of a linear scan measurement of the inner surface of a tubular member.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.
The following describes a system and a method for measuring the inner and outer surfaces of a tubular member in detail with reference to the accompanying drawings. The features of the following examples and embodiments may be combined with each other without conflict.
As shown in fig. 1, a system for measuring the inner and outer surfaces of a tubular member comprises a probe assembly 5, a probe adjusting mechanism, an extension plate 1, a z-direction displacement table 6, a chuck 8, an x-direction displacement table 9 and a turntable 10.
The basic principle of probe measurement is an optical fiber white light interferometry, and a spatial scanning Michelson interferometer based on a white light source is structurally characterized in that light emitted by a broadband white light source reaches a coupler through an optical fiber and then is divided into two paths, one path of light is collimated by a collimator and then is directly reflected by a plane reflector perpendicular to an incident beam and then returns to the optical fiber, the path is called a reference arm, a scanning displacement table is arranged below the reflector and can drive the reflector to move back and forth in the emergent light direction of the collimator, and the optical path of the reference arm is changed to realize spatial scanning. The other path of light is collimated by a collimator (the collimator is contained in the probe assembly 5), and finally projected to the surface of the measured piece, and the other path of light is reflected and returns to the optical fiber, and the path is called as a measuring arm. The basic principle of measurement is that two optical signals returned by the reference arm and the measurement arm form interference signals through an output port of a coupler, the interference signals reach a photoelectric detector through optical fibers and are converted into electric signals to be collected by a data collector, the data collector synchronously collects the grating ruler readings of the scanning displacement table, after an interference signal envelope peak value is extracted, the grating ruler readings of the scanning displacement table at the moment when the peak value corresponds to the peak value can be finally obtained, the optical paths of the reference arm and the measurement arm are equal at the moment, when different points on the surface of a measured piece are measured, the position of the interference signal envelope peak value changes due to the change of the optical path of the measurement arm, and the height difference between the different points on the surface to be measured can be calculated through the change of the grating ruler readings of the scanning displacement table corresponding to the position of the peak value.
The probe assembly 5 belongs to the end part of a measuring arm in an optical measuring system and mainly comprises a probe shell and an optical component. The optical component integrated in the probe assembly 5 is used for collimating the light beam input from the optical fiber, deflecting the collimated light beam by 90 degrees, focusing the collimated light beam, emitting the collimated light beam to the inner surface or the outer surface of the tubular member 7, and feeding back the optical signal carrying the optical path information to the white light interferometer for processing to obtain the distance information. The probe shell is a carrier of optical components, the optical components capable of realizing the optical path are integrated in the probe shell, the total length of the probe can be changed by increasing or reducing the number of probe sleeves in the probe shell, and extension plates 1 with different heights are correspondingly matched to meet the measurement requirements of tubular members 7 with different height ranges. The positive and negative ranges near the effective focal length of the off-axis parabolic reflector, i.e. the circular bands with the distance t in fig. 3, are effective measurement ranges of the probe, and the value of t is generally 2 to 4mm according to the quality of the measured surface. By selecting the off-axis parabolic reflectors with different effective focal lengths in the probe assembly 5, a series of probe assemblies 5 with different focal lengths can be obtained to meet the measurement requirements of tubular members 7 with different inner diameters. The probe assembly 5 with a standard effective measurement range is generally selected, and the point O in the probe assembly 5 is adjusted by the x-direction displacement table 9 1 The distance to the measured surface is only required to be within the effective measuring range of the probe, but the stroke of the x-direction displacement platform 9 is limited, when the inner diameter of the tubular member 7 is smaller, the adjustment space of the x-direction displacement platform 9 is insufficient, or the inside of the tubular member 7 is insufficientIf the distance to be adjusted exceeds the stroke of the x-direction displacement table 9 due to the overlarge diameter, the probe assembly 5 with other effective measurement ranges needs to be replaced according to actual measurement conditions. For the measurement of the inner surface, the principle of selecting the effective measuring range of the probe is that the effective focal length is less than or equal to half of the measured inner diameter, so when the distance from the probe assembly 5 to the measured surface is adjusted by the x-direction displacement table 9, the probe assembly 5 is only close to the inner surface of the tubular member 7 along the light emitting direction of the probe assembly 5.
As shown in fig. 1, the probe adjustment mechanism includes a manual rotation stage 2, a manual translation stage 11, a manual tilt angle device 3, a support rod 12, and a rotation mounting base 4, which are connected in sequence. The coarse adjustment range of the manual rotating table 2 is 360 degrees, the fine adjustment range is +/-3 degrees, and the fine adjustment precision is +/-5 degrees. The stroke of the manual translation stage 11 is +/-6.5 mm, the straightness is 5 mu m, and the adjustment precision is 10 mu m. The adjusting range of the manual angle swinging device 3 is +/-7 degrees, and the adjusting precision is 0.1 degree. The coarse adjustment range of the rotary mounting seat 4 is 360 degrees, the fine adjustment range is +/-7 degrees, and the fine adjustment precision is 10 degrees.
As shown in fig. 2, the position of the probe is the state when all the adjusting tables in the probe adjusting mechanism are in the zero position. Straight line OO 1 As probe axis, with O 1 The ray as the end point is the probe light-emitting direction, the straight line where the x axis is located is the rotation axis of the manual rotating platform 2, the manual angle swinging device 3 realizes the swinging of the platform surface by the rotation of the platform surface around the axis where the y axis is located, the ellipse in the figure is the projection of the circular track of the rotation of the center of the platform surface around the rotation axis for one circle on the plane xoz, and the rotation axis passes through the point O. The net effect of the manual bevel 3 is therefore to rotate the probe about the y-axis. The straight line of the z-axis is the rotation axis of the rotary mounting seat 4, and the table top of the manual translation table 11 moves in a translation mode along the positive and negative directions of the y-axis. The point O is the intersection point of the axis of the strut 12 and the axis of the probe, and when all the adjusting mechanisms are in zero position, the three rotating axes use the point O as an origin point stroke space rectangular coordinate system. When the adjusting mechanism is adjusted, the three rotating axes do not form a space rectangular coordinate system.
The manual rotating platform 2 is used for enabling all components mounted on the table top to rotate around the rotating axis of the manual rotating platform, the manual translation platform 11 is used for enabling all components mounted on the table top to translate together, the manual angle swinging device 3 is used for enabling all components mounted on the table top to swing together with the table top, and the rotating mounting seat 4 is used for fixing the probe assembly and enabling the probe assembly to rotate around the axis of the probe assembly.
The optical fiber white light interferometry requires that incident light meets corresponding requirements, and a relatively obvious interference signal which can be used for extracting an interference signal envelope or a fringe peak value can be obtained only when the light intensities of the measuring arm and the reference arm are matched, so that the adjustment of the angle of the incident light is realized by using the adjusting mechanism to carry out combined fine adjustment on the pose of the probe, and the conditions of the intensity of the reflected light and the like meet the measurement requirements.
The z-direction displacement table 6 is an air-floating guide rail displacement table, is driven by a linear motor, and can be replaced by other displacement tables. The stroke of the device is generally 500mm, the positioning precision can reach +/-0.5 mu m, the pitching, the deflection and the rolling angles are smaller relative to the mechanical guide rail rotary table, and the positioning precision, the motion error and the like directly influence the measurement precision of the system. The probe assembly 5, the adjusting mechanism and the extension plate 1 are integrally installed on the table top of the z-direction displacement table 6, and the z-direction displacement table 6 drives the probe to move along the positive and negative directions of the z axis by driving the extension plate 1.
As shown in fig. 1, when the tubular member 7 is longer, the probe assembly 5,z with a larger length-diameter ratio is required to swing towards the table top of the displacement table 6, which easily causes instability of the probe end, and the cross section of the extension plate 1 is i-shaped, so as to improve the vibration resistance of the long plate and reduce amplification of the table vibration during movement. The probe assembly 5, the adjusting mechanism and the extension plate 1 are integrally in the shape of Jiong when viewed from the y direction, and the structure can effectively improve the end point O of the probe 1 Thereby reducing the measurement error and improving the measurement accuracy.
The chuck 8 is a three-jaw self-centering chuck, which may be replaced by another clamp, the function of which is to clamp the tubular element 7. Because the tubular member 7 is basically a rotary body, the three claws of the chuck 8 move synchronously, so that the tubular member 7 is centered, namely, the axial line of the tubular member 7 and the axial line of the chuck are ensured to have certain coaxiality.
The rotary table 10 is arranged on an x-direction displacement table 9, the x-direction displacement table 9 is a mechanical guide rail displacement table, the positioning precision can reach +/-1 mu m, and the rotary table is driven by a ball screw and can be replaced by other displacement tables. It is used for driving the tested piece to move along the positive and negative directions of the x axis so as to adjust the point O of the long probe assembly 1 The distance to the inner and outer surface of the tubular member 7. The zero position of the x-displacement table 9 is the position in which the probe axis theoretically coincides with the turntable axis of rotation, which position has been calibrated beforehand when the measuring system is assembled.
The embodiment of the invention also provides a tubular member inner and outer surface measuring method based on the tubular member inner and outer surface measuring system, which specifically comprises the following steps:
s1, carrying out absolute reference calibration on an optical system in a probe assembly (5):
as described in the basic principle of measurement, the interferometer can only measure the absolute value of the relative distance, so that a point O is specified as the absolute distance measurement reference in the light-emitting direction of the probe 1 The distance to this point is known. Point O in FIG. 2 1 The arrow is the schematic of the emergent light, which is the intersection point of the probe axis and the emergent light axis.
After the probe assembly 5 is assembled, absolute reference calibration needs to be performed on the optical system, and the specific method is to measure the inner cylindrical surface under the condition that the axis of the probe and the axis of the inner cylindrical surface with the accurately calibrated inner diameter keep higher coaxiality, record the reading of the grating ruler of the scanning displacement table corresponding to the envelope peak value of the interference signal, wherein the reading position corresponds to the radius of the inner cylindrical surface, and the subsequent measurement value takes the radius value as the reference. The invention uses the three-jaw self-centering chuck to clamp the excircle of the probe, measures the inner hole of the chuck, ensures the coaxiality of the axis of the inner hole of the chuck and the axis of the probe, has the radius of the inner hole which is a relatively accurate known quantity and is limited by the problems of clamping precision and the like, so the reference is a relatively accurate reference, the calibration error is generally more than 10 mu m, and the subsequent further correction is still needed.
As shown in FIG. 3, the absolute reference is a point O 1 The radius value r of a circle, which is the center of the circle, is known. At point O 1 The dotted line as the end point is the optical axis of the light emitted from the probe, and the original value measured after calibration is the distance m from the reference (in FIG. 3, the distance m from the inner surface of the tubular member to the reference is shown as the distance m 1 And the distance m of the outer surface of the tubular member relative to the reference 2 ) Point of, O 1 The distance s to the inner and outer surface of the tubular member 7 is:
s＝r+m
in summary, the absolute reference calibration of the optical system enables the measurement system to have absolute distance measurement capability, and the measurement value is s.
S2, utilizing the calibration ring gauge to adjust the light path and calibrate before measurement, measuring to obtain a three-dimensional point cloud data sequence of the calibration ring gauge, carrying out least square fitting on the generated three-dimensional point cloud data sequence of the calibration ring gauge to obtain a fitting cylinder diameter, and taking the difference value between the fitting cylinder diameter and the nominal value of the ring gauge as a compensation value.
Before the measured piece is formally measured, the light path adjustment and the calibration before the measurement are needed. The calibration before measurement needs to use a calibration standard, specifically a 5-grade calibration ring gauge conforming to JB/T11233-2012 standard, and the roundness, straightness and diameter variation of the ring gauge can reach micron-scale (generally 1-3 μm, which increases with the increase of the size of the ring gauge). The gauge size of the ring gauge is selected according to the measured dimensions of the tubular member 7 and the effective measurement range of the probe assembly 5. The specific steps of the light path adjustment and the calibration before measurement are as follows:
s201: and (4) resetting all manual adjusting tables of the probe adjusting mechanism to zero.
S202: clamping the ring gauge with a chuck 8 by controlling the z-displacement stage 6 and the x-displacementThe table 9 is moved to make the point O 1 At a cross-sectional position substantially in the ring gauge in the z-direction, such that point O 1 The distance to the inner surface of the ring gauge is within the effective measuring range of the probe (for the probe assembly 5 with different effective measuring ranges and the calibration ring gauge combination with different specifications, the positions of the z-direction displacement table 6 and the x-direction displacement table 9 are recorded in advance so as to improve the efficiency of light path adjustment and calibration before measurement).
S203: the light emitting direction of the probe is adjusted in a combined mode by adjusting the manual rotating table 2, the manual translation table 11 and the manual angle swinging device 3, the ring gauge is measured by applying the tubular member inner and outer surface measuring system based on the optical fiber white light interferometry technology, meanwhile, the light intensity value of a light beam returned by a measuring arm displayed by equipment such as an oscilloscope is observed, the light intensity value reaches a threshold value which can be matched with the light intensity value of a reference arm, and the position of the maximum light intensity value is found as far as possible.
S204: the rotation mounting base 4 is finely adjusted, and the distance value obtained by the measurement of the system is observed until the minimum distance is found, as shown in fig. 3, at this time, the optical axis of the emergent light beam of the probe passes through the center of the circle of the ring gauge.
S205: after setting parameters such as the height position at the beginning and the end of the scanning measurement, the rotating speed of the turntable and the like, the z-direction displacement table 6 and the turntable 10 are controlled to move simultaneously, and the spiral scanning measurement as shown in fig. 4 is carried out on the inner surface of the ring gauge.
S206: in the scanning measurement process, the system synchronously acquires a measurement distance s value, a z-direction displacement table 6 and an x-direction displacement table 9 position value and a rotary table 10 rotation angle value through a data acquisition instrument, and the sampling frequency is generally 30kHz. The point cloud data is generated in such a way that the position value of a z-directional displacement table at a certain moment is taken as a z coordinate, the sum (measurement inner surface) or the difference (measurement outer surface) of a measured value s and the offset e of the x-directional displacement table 9 from the zero position of the displacement table is decomposed into x and y coordinates by using the rotation angle value of a rotating table 10 at the corresponding moment, the absolute position of one point in the point cloud data in the space is obtained, the data acquired at different moments are processed in the same way, and the three-dimensional point cloud data sequence of the inner cylindrical surface of the ring gauge is obtained.
S207: and performing least square fitting on the generated point cloud data to obtain the diameter of the fitting cylinder. Due to misalignment of the chuck 8, mis-installation between the chuck 8 and the turntable 10A series of errors such as differences are accumulated, a certain offset exists between the axis of the cylindrical surface in the ring gauge and the rotation axis of the rotary table 10, so that the measured value s of a single point periodically fluctuates in continuous multi-turn measurement, and the influence of the offset is eliminated through the diameter of the cylinder obtained through fitting. Nominal value of ring gauge D nom And fitting the diameter D of the cylinder mea The difference of (c) is a compensation value rc which compensates for the absolute ranging synthetic error: rc = D nom -D mea (ii) a When the measured piece is actually measured subsequently, the compensated measured value s' is as follows: s' = s + rc.
And S3, actually measuring the inner surface and the outer surface of the measured piece (namely the tubular piece 7), compensating the measured value by using the compensation value obtained in the step S2 to obtain three-dimensional point cloud data, fitting the point cloud data, and analyzing to obtain form and position tolerance (roundness, cylindricity, taper, coaxiality and the like) and surface roughness.
After the calibration is completed, the probe adjusting mechanism is kept still, and the scanning measurement of the tubular member 7 is directly performed, wherein the scanning measurement comprises the following specific steps:
s301: the tubular member 7 is held at a suitable height by a chuck 8, and the movement of the z-displacement stage 6 and the x-displacement stage 9 is controlled to bring a center point O of the probe assembly 5 1 The distance to the inner or outer surface of the tubular member 7 is within the effective measurement range of the probe;
s302: after parameters such as the height position at the beginning and the end of scanning measurement, the rotating speed of the rotary table and the like are set, the z-direction displacement table 6 and the rotary table 10 are controlled to move simultaneously, and according to requirements, spiral scanning measurement as shown in figure 4, circular scanning measurement as shown in figure 5 or linear scanning measurement as shown in figure 6 is carried out on the inner surface or the outer surface of the tubular member 7; and (5) compensating the measured value by using the compensation value obtained in the step (S2) to obtain the three-dimensional point cloud data of the tubular member 7.
S303: after the generated point cloud data is obtained, the point cloud data can be processed in point cloud data processing software, for the part of the geometric outline of the measured surface close to the outline surface of a standard geometric body, the point cloud data can be subjected to least square fitting by using standard geometric characteristics (circle, cylinder, cone and the like), and then form and position tolerance (roundness, cylindricity, conicity, coaxiality and the like) and surface roughness which need to be known are quickly measured and evaluated; for a measured piece with a complex inner and outer surface appearance, such as irregular surface appearance characteristics of threads, rifling and the like, point cloud data can be triangulated, and then size parameters needing to be known are measured.
The above embodiments are only used for illustrating the design idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention accordingly, and the protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications based on the principles and design concepts disclosed herein are intended to be included within the scope of the present invention.
Claims (9)
1. A system for measuring the internal and external surfaces of a tubular member, comprising: a probe assembly (5) and a probe adjustment mechanism; the probe assembly is based on the optical fiber white light interferometry principle, collimates light beams input by an optical fiber, deflects the collimated light beams by 90 degrees, focuses the collimated light beams and then emits the collimated light beams to the inner surface or the outer surface of the tubular part (7), and feeds optical signals carrying optical path information back to the white light interferometer for processing to obtain distance information, so that the measurement of the inner surface and the outer surface of the tubular part (7) is completed; the probe adjusting mechanism is used for adjusting the position of the probe assembly and is connected with the extension plate (1); the extension plate (1) is connected with a z-direction displacement table (6), and the z-direction displacement table (6) drives a probe assembly (5) to move along the extension plate (1)zThe shaft moves in positive and negative directions; the tubular member (7) is clamped by a chuck (8); the chuck (8) is sequentially connected with the rotary table (10) and the x-direction displacement table (9);
the probe adjusting mechanism comprises a manual rotating table (2), a manual translation table (11), a manual angle swinging device (3), a support rod (12) and a rotary mounting seat (4) which are connected in sequence; the rotary mounting seat (4) is connected with the probe assembly (5); the manual rotating platform (2) is connected with the extension plate (1); the combined fine adjustment of the position and the posture of the probe is carried out through the adjusting mechanism so as to realize the adjustment of the incident reflection light angle.
2. A system for measuring the internal and external surfaces of tubular elements according to claim 1, wherein said manual rotation table (2) has a coarse adjustment range of 360 °, a fine adjustment range of ± 3 ° and a fine adjustment precision of ± 5'; the stroke of the manual translation table (11) is +/-6.5 mm, the straightness is 5 microns, and the adjustment precision is 10 microns; the adjusting range of the manual angle swinging device (3) is +/-7 degrees, and the adjusting precision is 0.1 degree; the coarse adjustment range of the rotary mounting seat (4) is 360 degrees, the fine adjustment range is +/-7 degrees, and the fine adjustment precision is 10 degrees.
3. The system for measuring the inner and outer surfaces of the tubular member according to claim 1, wherein the probe assembly (5), the adjusting mechanism and the extension plate (1) are in a shape of Jiong, the cross section of the extension plate (1) is I-shaped; the above-mentionedzThe directional displacement table (6) is an air-float guide rail displacement table; the rotary table (10) is an air-floating rotary table.
4. A method for measuring the inner and outer surfaces of a tubular member, which is applied to the system for measuring the inner and outer surfaces of a tubular member according to any one of claims 1~3, the method comprising the steps of:
s1, carrying out absolute reference calibration on an optical system in a probe assembly (5);
s2, utilizing the calibration ring gauge to adjust a light path and calibrate before measurement, measuring to obtain a three-dimensional point cloud data sequence of the calibration ring gauge, performing least square fitting on the generated three-dimensional point cloud data sequence of the calibration ring gauge to obtain a fitting cylinder diameter, and taking the difference value between the fitting cylinder diameter and a nominal value of the ring gauge as a compensation value;
and S3, actually measuring the inner surface and the outer surface of the tubular part (7) of the measured part, compensating the measured value by using the compensation value obtained in the step S2, generating three-dimensional point cloud data of the tubular part (7), and performing fitting analysis on the three-dimensional point cloud data to obtain form and position tolerance and surface roughness.
5. The method for measuring the inner and outer surfaces of the tubular member according to claim 4, wherein the step S1 is specifically: and measuring the inner cylindrical surface under the condition that the axial line of the probe and the axial line of the inner cylindrical surface with the accurately calibrated inner diameter keep higher coaxiality, recording the grating ruler reading of the scanning displacement table corresponding to the envelope peak value of the interference signal, wherein the reading position corresponds to the radius of the inner cylindrical surface, and the subsequent measurement value takes the radius value as the reference.
6. The method for measuring the inner and outer surfaces of the tubular member according to claim 4, wherein the step S2 comprises the following steps:
s201: returning all manual adjusting tables of the probe adjusting mechanism to zero;
s202: clamping the calibration ring gauge by a chuck (8), and controllingzTo a displacement table (6) andxto the displacement table (9) to make the probe assembly center pointO 1 In thatzUp to a position substantially at the mid-section of the ring gauge, so as to form a pointO 1 The distance of the inner surface of the ring gauge is equal to the effective focal length of the probe;
s203: the light emitting direction of the probe is adjusted by adjusting a manual rotating table (2), a manual translation table (11) and a manual angle swinging device (3), the ring gauge is measured based on an optical fiber white light interference measurement technology, meanwhile, the light intensity value of a light beam returned by a measuring arm is monitored, the light intensity value reaches a threshold value which can be matched with the light intensity value of a reference arm, and the position of the maximum light intensity value is found as far as possible;
s204: finely adjusting the rotary mounting seat (4), and observing the distance value measured by the inner and outer surface measuring systems of the tubular part until the minimum distance is found;
s205: setting the height position of the scanning measurement start and end and the rotation speed of the turntable, and controllingzSimultaneously moving the displacement table (6) and the rotary table (10) to perform spiral scanning measurement on the inner surface of the ring gauge;
s206: in scanning measurement, the measurement distance is acquiredsValue (c),zThe point cloud data is generated according to the position value of the displacement table (6) and the rotation angle value of the rotary table (10) in the following mode: at a certain momentzTo a displacement table position value ofzCoordinates, resolving the measured distance into values corresponding to the time of rotation of the turntable (10)xCoordinates andycoordinates, the absolute position of a point in the point cloud data in space is obtained, and the absolute position is acquired at different momentsPerforming the same processing on the data to obtain three-dimensional point cloud data of the inner cylindrical surface of the calibration ring gauge;
s207: and performing least square fitting on the generated calibration ring gauge point cloud data to obtain the diameter of a fitting cylinder, wherein the difference between the diameter and the nominal value of the ring gauge is a compensation value.
7. A method for measuring the inner and outer surfaces of a tubular member according to claim 4, wherein the step S3 comprises the substeps of:
s301: clamping the tubular member (7) in a suitable height position by means of a chuck (8); by controllingzTo a displacement table (6) andxmove to the displacement table (9) to make the inner circle center point of the probe component (5)O 1 The distance to the inner surface or the outer surface of the tubular member (7) is within the effective measuring range of the probe;
s302: setting the height positions of the beginning and the end of scanning measurement and the rotating speed of the rotary table, controlling the z-direction displacement table (6) and the rotary table (10) to move simultaneously, and scanning and measuring the inner surface or the outer surface of the tubular part (7); compensating the measured value by using the compensation value obtained in the step S2 to obtain three-dimensional point cloud data of the tubular part (7);
s303: and performing fitting analysis on the three-dimensional point cloud data of the tubular member (7) to obtain form and position tolerance and surface roughness.
8. The method for measuring inner and outer surfaces of a tubular member according to claim 7, wherein the scanning measurement in step S302 is a helical scanning measurement, a circular scanning measurement or a linear scanning measurement.
9. The method for measuring the inner and outer surfaces of the tubular member as claimed in claim 7, wherein in step S303, for the portion of the geometric profile of the measured surface close to the profile of the standard geometric body, the point cloud data is subjected to least square fitting by using standard geometric features including a circle, a cylinder and a cone; then rapidly measuring and evaluating form and position tolerance and surface roughness which need to be known; for a measured piece with complex inner and outer surface topography characteristics including threads and rifles, point cloud data are triangulated, and then size parameters needing to be known are measured.
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