CN104515481A - Device and method for measuring planeness of large-diameter torus - Google Patents

Abstract

The device and method for measuring the flatness of a large-diameter torus relate to the measurement technology in the field of mechanical processing, assembly and testing, and solve the problems of complex structure and limited use of the existing measuring device for the flatness of the torus. Low precision leads to large measurement errors and other problems, including precision turntable, internal focusing light tube, fiber optic point light source, turntable leveling mechanism, measuring rod and CCD detector. In this method, the optical fiber point light source is imaged above the toroidal surface by using the internal focusing light tube first, and the precision turntable drives the image point of the point light source to rotate to draw a circle in space, and then the plane where the circle is located is used as the reference, and the CCD detector is used to Receive the point light source image point, measure the distance between the measured point and the reference plane according to the off-target amount, and finally obtain the flatness of the measured torus through data processing and calculation. The invention has the advantages of high measurement precision, simple data processing, convenient operation, high efficiency and low cost; the invention is suitable for the detection of the flatness of large-sized ring parts.

Description

Device and method for measuring the flatness of a large-diameter torus

technical field

The invention relates to the measurement technology in the field of mechanical processing, assembly and adjustment detection, in particular to a device and method for detecting the flatness of a large-diameter torus.

Background technique

The high-precision measurement of flatness is an important link in the process of machining, assembly and testing. The diameter of large-sized circular parts is on the order of several meters, and the accurate measurement of its flatness has always been a difficult point. The method currently used in production There are level instrument method, multi-probe error separation method, three-coordinate measurement method, liquid level method, turntable rotation method, three-point measuring device method and micro-collimation telescope method, etc.

Among them, the level meter method is the most widely used. Because the pitch is measured point by point, the measurement speed is too slow, and there are many external interference factors. In addition, the most mature application of this method is mainly for large planes without holes in the middle, so as to facilitate the division of measurement grids; The multi-probe separation method can obtain micron-level high precision, but due to the use of many sensors, the amount of data to be processed is large, the structure is complex, the operation is inconvenient, and the use is limited; the accuracy of the three-coordinate measurement method decreases with the increase of the measurement size , the mobile bridge coordinate measuring machine can only measure ring parts with a diameter of about two meters at most, and the portable coordinate measuring machine (articulated arm or laser tracker) can measure large-sized parts, but the accuracy is low and the price is expensive; the liquid surface method The hardware configuration of the system is complicated, and the point measurement process needs to wait for the liquid level to be stable, which is inefficient, greatly affected by the environment, and has poor accuracy; due to the influence of the stiffness of the measuring cantilever by the turntable rotation method, the measurement accuracy of large-sized rings is low; three points The detector method is specially developed for the flatness measurement of the bearing ring of the turntable of the photoelectric theodolite, but due to the influence of the stiffness of the three-point detector itself, it is only well applied to the bearing ring with a diameter of about one meter or less; The collimating telescope cooperates with the rotation of the pentaprism to form a reference plane. This method is more suitable for the measurement of the flatness of the circular ring. However, because it uses the principle of a flat plate micrometer to read, it is affected by the image quality and magnification of the optical system during long-distance measurement. The measurement error is large.

Contents of the invention

The present invention solves the problems of complex structure and limited use in existing measuring devices for the flatness of circular rings. The current measuring method has problems such as large measurement errors due to low measurement accuracy, and provides a method for measuring the flatness of large-diameter circular rings. devices and methods.

A device for measuring the flatness of a large-diameter torus, including a precision turntable, an inner focusing light tube, a fiber optic point light source, a turntable leveling mechanism, a measuring rod, and a CCD detector; the precision turntable is placed on the turntable leveling mechanism, and the inner focus is adjusted The light pipe is fixed on the surface of the precision turntable, the optical axis of the inner focusing light pipe is perpendicular to the rotation axis of the precision turntable, the rotation axis of the precision turntable coincides with the center of the measured torus, and the optical fiber point light source is connected to the The focus position of the inner focusing light tube, the target surface of the CCD detector is parallel to the axis of the measuring rod, the axis of the measuring rod is perpendicular to the toroidal surface to be measured, and the head of the measuring rod is a spherical surface, which is in point contact with the toroidal surface to be measured.

A method for measuring the flatness of a large-diameter torus, the method is realized by the following steps:

Step 1. Place the measuring rod in turn on the position of the measured point at equal intervals on the measured toroidal surface, so that the CCD detector receives the image points of the optical fiber point light sources at different positions of the measured point, Rotate the precision turntable so that the off-target amount of the image point of the optical fiber point light source at the different measured point positions in the horizontal direction of the CCD detector is zero, and record the off-target amount in the vertical direction of the CCD detector;

Step 2: Perform data processing on the off-target amount recorded in the vertical direction of the CCD detector described in step 1 to obtain the error of the flatness of the measured torus, and realize the detection of the flatness of the measured torus.

Beneficial effects of the present invention: the present invention innovates and improves on the basis of the traditional method, overcomes the deficiencies of the traditional method, adopts the method of optics and image processing, uses the inner focusing light tube combined with the precision turntable, and uses the optical fiber point light source image point in the space The circular surface formed by the rotation is used as the reference, and the CCD detector is used to receive the image point of the optical fiber point light source and measure the off-target amount, and finally calculate the flatness of the measured circular surface through data processing. The invention has clear principle, simple structure, convenient operation, high precision and strong practicability. The invention forms the reference plane in an optical way, and the precision is not affected by the structural rigidity; the distance between the reference spot and the measured surface is directly measured by the CCD, and the measurement accuracy is high; for the measured circular rings with different diameters, the inner focusing light tube is adjusted , the fiber optic point light source image point is transmitted to the top of the measured ring, and the measurement adaptability is strong; at the same time, on-site inspection can be carried out to guide the assembly and adjustment of large rings with poor stiffness, so that the flatness error can meet the requirements.

Description of drawings

Fig. 1 is a schematic diagram of a device for measuring the flatness of a large-diameter torus according to the present invention.

In the figure: 1. CCD detector, 2. Fixed lens group, 3. Focusing lens group, 4. Optical fiber point light source, 5. Precision turntable, 6. Turntable leveling mechanism, 7. Measuring rod, 8. Measured circle ring.

Detailed ways

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 1. This embodiment is described in conjunction with FIG. 1 , a device for measuring the flatness of a large-diameter torus, which includes a precision turntable 5, an inner focusing light tube, an optical fiber point light source 4, a turntable leveling mechanism 6, and a measuring rod. 7 and CCD detector 1. The inner focusing light pipe is composed of a fixed lens group 2 and a focusing lens group 3 . The precision turntable 5 is placed on the turntable leveling mechanism 6, the inner focusing light tube is fixed on the surface of the precision turntable 5, the optical fiber point light source 4 is connected to the focus position of the inner focusing light tube, and the CCD detector 1 is installed on the measuring rod 7 .

The focusing lens group 3 in the inner focusing light pipe described in this embodiment can move along the optical axis direction, and the rotation axis of the precision turntable 5 coincides with the center of the measured torus 8 . The optical axis of the inner focusing light tube is perpendicular to the rotation axis of the precision turntable 5 . The target surface of the CCD detector 1 is parallel to the axis of the measuring rod 7 , the axis of the measuring rod 7 is perpendicular to the measured torus 8 , and the head of the measuring rod 7 is a spherical surface, which is in point contact with the measured torus 8 .

Specific embodiment two, present embodiment is the method for the device for measuring the flatness of large-diameter torus described in specific embodiment one, and the concrete steps of this method are:

First, adjust the inner focusing light tube before the measurement, put the measuring rod 7 vertically on the torus 8 to be tested, and the CCD detector 1 receives the image point of the optical fiber point light source 4, and adjusts the position of the focusing lens group 3 so that The image spot is the smallest.

Secondly, adjust the posture of the precision turntable 5, move the position of the measuring rod 7, make the CCD detector 1 receive the image points of the optical fiber point light source 4 at three different positions equally spaced on the torus 8 to be measured, and adjust the adjustment of the precision turntable. The flat mechanism 6 makes the off-target amount of the image point in the vertical direction of the CCD detector 1 equal.

When measuring, first mark the positions of the measured points at equal intervals on the measured torus 8, then place the measuring rod 7 at the position θ _i of the measured points in turn, and rotate the precision turntable 5 so that the image point is on the CCD detector 1 The off-target amount in the horizontal direction is zero, and the off-target amount _yi in the vertical direction of the CCD detector 1 is recorded.

Finally, to process the measured data, first expand the measured data y _i into a Fourier series f(θ _i ) for harmonic analysis, and then remove the constant term and the first-order harmonic Y ₁ to obtain the data t _i .

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; k\&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; k</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>$

in:

${\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}$

${\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; \&ap;</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; k</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}$

${\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; \&ap;</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; k</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}$

The kth order harmonic function: Y _k ＝a _k cos kθ _i +b _k sin kθ _i

${\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}$

Then perform least squares straight line fitting on (θ _i , t _i ) in the plane, the straight line equation is:

Aθ+Bt+C=0

Then calculate the distance from each point (θ _i , t _i ) to the fitted line:

${\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; A\&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; Bt</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; C</span>}}{\sqrt{{\mathrm{<span\; class="notranslate">\; A</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}$

Finally calculate the flatness error: Flatness=D _max -D _min .

In the formula: y _i is the off-target amount of the CCD detector in the vertical direction, θ _i is the angle value of the measuring point position on the torus, a _k is the coefficient of the cosine component in the harmonic function of the kth term, and b _k is the coefficient of the kth harmonic function The coefficient of the sine component in the kth order harmonic function; Y _k is the kth order harmonic function, t _i is the data after removing the constant item and the first order item after the harmonic analysis, and A, B and C are the fitting straight line coefficient, D _i is the distance from each point to the fitting line, D _max is the maximum distance, D _min is the minimum distance, and Flatness is the flatness error.

The measurement method of the present invention forms a reference plane in an optical manner, and the accuracy is not affected by the structural rigidity; the distance between the reference spot and the measured torus is directly measured by a CCD detector, and the measurement accuracy is high; for measured circles with different diameters The torus optical part adjusts the inner focusing light pipe, transmits the image point of the optical fiber point light source to the top of the torus to be measured, and has strong measurement adaptability; the invention is suitable for machining enterprises, large component installation and construction units, and inspection and measurement departments. .

Claims (5)

1. measure the device of large diameter circle facial plane degree, comprise precise rotating platform (5), interior focusing light pipe, fiber optic point source (4), leveling turntable mechanism (6), measuring staff (7) and ccd detector (1), precise rotating platform (5) is placed in leveling turntable mechanism (6), interior focusing light pipe is fixed on precise rotating platform (5) table top, it is characterized in that, the rotational axis vertical of described interior focusing light pipe optical axis and precise rotating platform (5), the turning axle of described precise rotating platform (5) and the center superposition of measured circle anchor ring (8), described fiber optic point source (4) is connected to the focal position of interior focusing light pipe, the axis being parallel of ccd detector (1) target surface and measuring staff (7), measuring staff (7) axis is vertical with measured circle anchor ring (8), measuring staff (7) head is sphere, and be point cantact with measured circle anchor ring (8).

2. the device of described measurement large diameter circle facial plane degree according to claim 1, it is characterized in that, described interior focusing light pipe is made up of fixed lens group (2) and focusing lens group (3); Focusing lens group (3) in described interior focusing light pipe moves along optical axis direction.

3. the method for the device of measurement large diameter circle facial plane degree according to claim 1, it is characterized in that, the method is realized by following steps:

Step one, successively measuring staff (7) is placed on the position of measured point described in the upper position, equally spaced mark measured point of measured circle anchor ring (8), ccd detector (1) is made to receive the picture point of the fiber optic point source (4) of position, different measured point, rotate precise rotating platform (5), make the picture point of the fiber optic point source (4) of position, described different measured point be zero at the miss distance of ccd detector (1) horizontal direction, and record the miss distance of ccd detector (1) vertical direction;

Step 2, data processing is carried out to the miss distance of record ccd detector (1) vertical direction described in step one, obtain the error of measured circle anchor ring (8) flatness, realize the detection of the flatness to measured circle anchor ring.

4. the method for measurement large diameter circle facial plane degree according to claim 3, it is characterized in that, the detailed process obtaining flatness error in step 2 is: first measurement miss distance data are launched into Fourier series and carry out frequency analysis, secondly, removal constant term and once item harmonic wave, again, carry out least square fitting, finally calculate flatness error.

5. the method for the measurement large diameter circle facial plane degree according to claim 3 or 4, it is characterized in that, before step, also comprise the adjustment to interior focusing light pipe, measuring staff (7) is vertically placed on measured circle anchor ring (8), ccd detector (1) receives the picture point of fiber optic point source (4), and the position of adjustment focusing lens group (3), makes picture point hot spot minimum; To the adjustment of precise rotating platform (5) attitude, the position of mobile measuring staff (7), ccd detector (1) is made to receive the picture point of fiber optic point source (4) at the equally spaced diverse location of the upper mark of measured circle anchor ring (8), adjustment leveling turntable mechanism (6), makes picture point equal at the miss distance of ccd detector (1) vertical direction.