CN101706261A - Device for measuring diameter of large shaft working piece by non-contact-type online measurement - Google Patents

Abstract

The invention is a device for non-contact on-line measurement of the diameter of a large-scale shaft workpiece, which solves the problems of heavy inspection tools, inconvenient operation, low measurement accuracy and low measurement efficiency for precision measurement of large-diameter workpieces in machining. The cloud platform of the measuring base of the present invention is equipped with three guide rails connected by screw rods and threads, the base is equipped with a column, and the column is equipped with four guide rail sliders and locking screws. The sensor is connected by the locking screw, and the two guide rail sliders in the middle of the column are connected by the locking screw to install the sliding plate and the sensor. The length of the sliding plate of the middle guide rail slider is smaller than that of the upper and lower sliding plates. The sensor and the computer are connected by cables. Calibration A symmetrical support seat is fixed on the base, and the support seat is connected by a rotating shaft and equipped with bearings. There are two large discs and small discs with different diameters in the center of the rotating shaft. The speed regulating motor is connected and fixed on the calibration base by a bracket. Above, the shaft of the speed-regulating motor is connected to the rotating shaft at one end, and the rotating shaft at the other end is connected to the speed encoder fixed on the bracket of the calibration base. The measuring base and the calibration base are connected by a large platform. The invention has the advantages of scientific design, simple structure, convenient operation, data sampling by sensors, automatic centralized processing by computer and circular encoder, reliable precision of measuring large-scale shaft workpieces, and greatly improves the high-precision measuring instruments for measuring machining shaft workpieces in my country.

Description

A device for non-contact on-line measurement of the diameter of large shaft workpieces

technical field

The invention relates to a device for measuring the diameter of a machining large shaft workpiece, in particular to a non-contact online measuring device for the diameter of a large shaft workpiece.

Background technique

With the development of large-scale mechanical equipment in the direction of complexity and precision, the inspection requirements for the processing quality of large-sized workpieces required by these equipment are also continuously increasing. For a long time, a lot of research has been done on the measurement of large diameters at home and abroad, but there has been no ideal method and instrument, especially in the machining industry, the precision measurement of large diameters has not been well resolved.

For the measurement of large outer diameters, companies currently generally use direct measurement methods such as vernier calipers, outer micrometers, calipers, and π rulers. The inspection tools are heavy, inconvenient to operate, low in measurement accuracy, and low in efficiency. Compared with the direct measurement method, the indirect measurement method has obvious advantages in terms of measurement range, instrument portability, and measurement efficiency. Representative measurement methods include the roller method, three-point method, and circular element method.

The roller method for measuring large diameters has the advantages of small size, convenient operation, high work efficiency, and online dynamic measurement. However, there are many error factors such as relative slipping between the roller and the workpiece during the measurement process. At present, institutions such as Tianjin University and Hefei University of Technology are doing Engaged in the research of large-diameter measurement by the roller method, but in order to reduce the influence of errors and perform error compensation, the instrument structure and signal processing process are becoming more and more complicated.

The measurement principle of the three-point method is based on the theorem that a circle can be uniquely determined through three points that are not on the same straight line in plane geometry, and the diameter of a large-sized hole or shaft is obtained through indirect measurement. At present, portable products such as ETALON ZEDURAM general-purpose electronic measuring instrument produced by Swiss TESA Company, etc. Southwest Jiaotong University is also currently conducting research in this area, and has designed and developed a set of inspection tools for measuring the diameter of train wheels.

Circumferential element method diameter measurement, according to the measured circumferential elements, can be divided into: measuring the bow height and chord length of the circumference to obtain the measured diameter; measuring the angle between two tangents and the distance from the corner top to the workpiece surface to obtain the measured diameter, Measure the fixed angle and chord length to obtain the measured diameter, etc. The "intelligent large-diameter measuring instrument" developed by Yang Hongyu and others based on the marking method essentially uses the method of angle and chord length; the patent "method and device for measuring the diameter of large-diameter shaft and disk workpieces" also uses the same measurement principle.

In the method of measuring the diameter according to the elements of the circumference, the measuring instruments of bow height and chord length are widely used at present. At present, institutions such as Wuhan University of Technology, Southwest Jiaotong University, and Hunan University of Science and Technology where the applicant is located are actively carrying out research in this area. The key issue of the research is how to improve the diameter measurement accuracy of the bow-high-chord method.

Contents of the invention

The purpose of the present invention is to provide a scientific design, simple structure, according to the size optimization of the measured large shaft to determine the calibration system large disk and small disk and the chord length value of the test system, the chord length and initial bow height parameters of the test system Perform on-site calibration. The laser displacement sensor is used to measure the bow height, and the computer automatically eliminates abnormal data. It is a device for non-contact online measurement of the diameter of large shaft workpieces.

The technical scheme adopted by the present invention to solve its technical problems is: three guide rails (6) are mounted on the cloud platform (5) of the measurement base (4) and are connected by screw rods (7) and threads, and columns (8) are mounted on the base (4) ), four guide rail sliders (9) are set on the column (8) and locking screws (10) are housed, and the slide plates (11) fixed on the upper and lower guide rail sliders (9) have the same length and are equipped with sensors (12) Connected by the locking screw (13), the two guide rail sliders (9) in the middle of the column (8) are connected by the locking screw (14) to be equipped with a slide plate (11) and a sensor (12), and the middle guide rail slider ( 9) the length of the slide plate (11) is less than the upper and lower slide plates (11), the sensor (12) and the computer (1) are connected by cables, the calibration base (15) is fixed with a symmetrical support seat (16), the support seat ( 16) Connected by the rotating shaft (17) and equipped with bearings (18), the center of the rotating shaft (18) is equipped with two discs (19) and small discs (20) with different diameters, and the speed regulating motor (2) Connected and fixed on the calibration base (15) by the bracket (21), the shaft of the speed-regulating motor (2) is connected with one end of the rotating shaft (17), and the other end of the rotating shaft (17) is fixed on the calibration base (15) bracket (21 ) on the rotational speed encoder (22), the measuring base (4) and the calibration base (15) are connected by a large platform (23). The measurement base (4) and the calibration base (15) can be used alone, because the measured object The special-shaped or super-large, the measuring base (4) can be installed with tripods, curved frames and other special-shaped frames.

The advantages of the present invention are: 1. Scientific design and simple structure. According to the size optimization of the measured large shaft, the large disc and small disc of the calibration system and the chord length value of the test system are determined, and the chord length and initial bow height parameters of the test system are calibrated on site. The symmetrical arrangement of three high-precision laser displacement sensors is used for the relative measurement of the bow height, which reduces the position accuracy requirements between the test system and the measured large axis during measurement. 2. The data sampling is diversified, and the error of centralized processing data is small. Adjust the symmetry of the upper and lower sensors through the readings of the sensors during the measurement process, and automatically eliminate abnormal data through the processing of the measurement data. The calibration and measurement process automatically samples uniformly within the entire circumference and takes the average method to reduce the influence of random measurement errors and roundness errors on the measurement results. 3. The production cost is low and the operation cost is small.

Description of drawings

Accompanying drawing 1 present invention measuring base and calibration base structural diagram

Accompanying drawing 2 is the structural schematic diagram of measuring base of the present invention

Accompanying drawing 3 is the structural schematic diagram of the calibration base of the present invention

The present invention will be described in further detail below according to accompanying drawing:

Detailed ways

The present invention can know from Fig. 1, Fig. 2 and Fig. 3, three guide rails (6) are housed on the cloud platform (5) of measuring base (4) of the present invention and are connected by screw mandrel (7) and screw thread, and base (4) is equipped with Upright column (8), four guide rail sliders (9) are set on the upright column (8) and locking screws (10) are housed, and the slide plates (11) fixed on the upper and lower guide rail sliders (9) are of the same length and equipped with sensors (12) Connected by the locking screw (13), the two guide rail sliders (9) in the middle of the column (8) are connected by the locking screw (14) and equipped with a slide plate (11) and sensor (12), and the middle guide rail The length of slide block (9) slide plate (11) is less than upper and lower slide plate (11), is connected by cable between sensor (12) and computer (1), is equipped with symmetrical support base (16) on the calibration base (15), Support seat (16) is connected by rotating shaft (17) and bearing (18) is housed, and rotating shaft (18) center is housed with two discs (19) and small discs (20) with different diameters, and the speed-regulating motor (2) Connected and fixed on the calibration base (15) by the bracket (21), the shaft of the speed-regulating motor (2) is connected with one end of the rotating shaft (17), and the other end of the rotating shaft (17) is fixed on the calibration base (15) The speed encoder (22) on the bracket (21) is connected, and the measuring base (4) and the calibration base (15) are connected by a large platform (23). The function of the guide rail slider (9) is that when the sensor (12) on the middle lower plate (11) has established the orientation and distance to the object to be measured, the guide rail slider (9) connected with it can pass through the locking screw (14) Correct and fine-tune the lower rail slider (9), slide plate (11) and sensor (12) to ensure reliable and accurate data. The measurement base (4) and the calibration base (15) can be used alone. Irregular or super large, the measuring base (4) can be installed with tripods, curved frames and other special-shaped frames. First, according to the diameter of the measured large shaft, comprehensively consider the space size of the test system and the transmission relationship between the bow height measurement error and the diameter measurement result, Reasonably choose the chord length parameter. Generally speaking, for a large shaft with a diameter of D, it is more appropriate to choose the chord length (L) of about L=2D/3. If the large shaft workpiece is oversized or shaped, the measuring base (4) can be installed and lengthened Tripods and other supports, used separately.

According to the diameter D of the measured large shaft, the chord length L and the measurement range of the laser displacement sensor (12), the approximate dimensions D ₁ =D+Δ and D ₂ =D-Δ of the calibration large disk are determined. Under the premise that the measurement range of the sensor (12) allows, the value of Δ is as large as possible. Since the diameter value of the large disk will be measured and calibrated on the three-coordinate measuring machine, there is no special requirement for its dimensional tolerance. In addition, the initial bow height and chord length parameters of the measuring device are calibrated by taking the average of multiple calibration results after rotating a full circle. value, so there is no strict requirement on the roundness error of the disc.

On the three-coordinate measuring machine, the two outer circles of the large disk (19) and the small disk (20) are densely and uniformly measured and sampled to obtain the coordinate values of the points on the N circles, and the sequence of coordinate values obtained by sampling is according to the parity The serial number is divided into two sequences of equal length, and the frequency domain analysis method is used to estimate the main harmonic component and noise intensity σ of the circle, and the contour is reconstructed according to the main harmonic component value of the circle contour, and the reasonable tolerance range of the contour is given according to σ, exceeding The bad ones are abnormal data to be eliminated, and finally the least square method is used to calculate the disc diameters D ₁ and D ₂ . When the main harmonic component of the disc profile is not greater than 50 microns, and the coordinate measurement error is not more than 5 microns, and 256 points are evenly sampled on the circumference, the simulation results show that the diameter calibration error is less than 1 micron.

The calibration of the measurement system’s chord length and initial bow height parameters is shown in Figure 1. First move the guide rail slider (9) according to the selected chord length parameter, the distance between the upper and lower sensor (12) light is roughly equal to the selected chord length; the middle sensor (12) light roughly passes through the axis of the measuring shaft; The measuring device is close to the calibration disc, adjust the upper, middle and lower plates (11) to ensure that the measurement of the large disc (19) and the small disc (20) is within the measurement range of the sensor (12), lock the slide plate ( 11), start the motor (2), adjust the speed and measure the speed with the encoder (22), to ensure that it is basically consistent with the speed of the large shaft to be measured.

Let l ₁ be the distance from the disk axis to the light of the upper sensor (12), and l ₃ the distance to the light of the lower sensor (12), then define the asymmetric error of the light of the upper and lower sensors (12) as |l ₁ -l ₃ | . Assuming that the readings of the upper and lower sensors (12) are S ₁₁ and S ₁₃ when measuring the large disk (19), and the readings of the upper and lower sensors (12) are S ₂₁ and S ₂₃ when measuring the small disk (20), it is guaranteed that the sensor ( 12) The height changes slightly when measuring the two circles, then when S ₁₁ -S ₂₁ =S ₁₃ -S ₂₃ , it indicates that the light rays of the upper and lower sensors (12) have been symmetrical during the calibration process. According to this phenomenon, adjust one of the sensors ( 12) Height until S ₁₁ -S ₂₁ =S ₁₃ -S ₂₃ . Then adjust the middle guide rail slider (9) up and down, when the reading of the sensor (12) is minimum, it shows that the light of the middle sensor (12) is centered, and each guide rail slider (9) is locked. In the above adjustment process, the readings of the sensor (12) are averaged by taking multiple samples during one rotation, so as to reduce the impact of disc roundness errors on the symmetry adjustment and centering adjustment. After the test system is adjusted, the calibration of the parameters of the chord length and initial bow height of the test system can be implemented. Let the bow height of the large disc (19) be the initial bow height, denoted as H, and the chord length denoted as L. Put the measuring system close to the big disc (19) to obtain the average readings of the three sensors (12) for one week: S ₁₁ , S ₁₂ and S ₁₃ ; similarly place the measuring system close to the small disc (20) to obtain the average readings: S ₂₁ , S ₂₂ and S ₂₃ . The three sensors (12) sample N points in a whole week, and for the N point data, a method similar to that of measuring the diameter of a disk with three coordinates is used for data processing, and abnormal values are eliminated.

则大圆盘(19)和小圆盘(20)的弓高差为：ΔH＝S′₂-S′₁，则小圆盘(20)的弓高为H+ΔH。remember

Then the bow height difference between the big disk (19) and the small disk (20) is: ΔH=S′ ₂ −S′ ₁ , and the bow height of the small disk (20) is H+ΔH.

Construction equation:

Given the large disk (19), small disk (20) and ΔH, L and H can be obtained by solving the above equation, and the parameters H, L and parameters S ₁₁ , S ₁₂ , S ₁₃ are stored to complete the test device. calibration.

则被测大轴的直径D为：Once the test device is calibrated, the relative positions of the three sensors (12) are fixed and cannot be adjusted. When measuring the large shaft to be tested, it is only necessary to install the test system on the tripod, and adjust the screw (7) nut on the measurement base (4) to ensure the symmetrical requirements of the upper and lower sensors (12), that is, to ensure S ₁₁ -S ₃₁ =S ₁₃ -S ₃₃ is enough. The measurement process is exactly the same as the data processing method in the process of measuring the large disc (19) in the calibration link, and three values S ₃₁ , S ₃₂ and S ₃₃ are obtained, then the bow height of the measured large shaft is:

Then the diameter D of the major shaft to be measured is:

$\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="H2009102271967E0000031.png"\; state="\{\{state\}\}">L</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}{<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}}^{<span\; class="notranslate">\; \&prime;</span>}$

The accuracy analysis of the measurement results will be analyzed in the following section with an implementation example.

Example

It is required to measure the size of the large axis with a diameter of 505mm, and the LK-G30 laser displacement sensor (12) is selected. The working distance is 30mm, and the measurement range is -5mm-5mm. Compared with the ML10 laser interferometer, the measurement accuracy is 1μm about. The chord length is selected as 400mm, and the diameters of the calibrated large discs are respectively taken as 508mm and 500mm.

Three sizes of outer discs are processed on a large disc, and calibrated on a three-coordinate measuring machine. The upper, middle and lower sections of each size of the circle are measured respectively, and the diameters and roundness of the three outer circles are obtained as follows As shown in the table:

Diameter (mm) Roundness (μm) round one 499.786499.789499.791 26.39.915.5 round two 503.600503.601503.605 13.712.417.7 round three 507.750507.751507.752 25.615.021.9

When calibrating, firstly, the middle sensor (12) can be roughly centered, locked, and the position of the lower sensor (12) is fixed, and the calibration disc (19) is measured to obtain the readings S ₁₁ , S ₁₂ and S ₁₃ . Calibrate the small disc (20) for height position measurement to obtain readings S ₂₁ , S ₂₂ and S ₂₃ ; record ΔS ₁ =S ₁₁ -S ₂₁ ; ΔS ₃ =S ₁₃ -S ₂₃ ; if ΔS ₁ =ΔS ₃ , it indicates The upper and lower sensors (12) are symmetrical, otherwise the position of the upper sensor (12) needs to be adjusted until ΔS ₁ =ΔS ₃ . Taking the chord length of 400mm and the calibrated major shaft diameters of 500mm and 508mm as an example, when the asymmetry error is 4mm, the difference between ΔS ₁ and ΔS ₃ will be about 0.23mm; when the asymmetry error is 2mm, the difference between ΔS ₁ and ΔS ₃ will be 0.11 About mm, the displacement sensor (12) finds that there is no problem with such a large difference. In the actual calibration process, the difference between ΔS ₁ and ΔS ₃ is controlled within 20 μm, which is enough to ensure the asymmetrical error requirement during calibration.

When using the calibrated test system to measure the large shaft to be tested, adjust the measuring base (4) lead screw (7) nut until the difference between ΔS ₁ and ΔS ₂ is controlled within 20 μm, which is enough to ensure that the overall position of the sensor (12) is biased during measurement. The shift is less than 0.02mm.

Assuming that after the equipment is adjusted, when measuring the calibration circle 1, the asymmetric error of the upper and lower sensors (12) obeys the normal distribution of 3σ=4mm, and the misalignment error of the middle sensor (12) obeys the normal distribution of 3σ=5mm; In circle 2, the overall position of the sensor (12) has an upper and lower random offset of 3σ=0.02mm relative to the measurement circle 1; when the large axis to be measured is measured, the overall position of the sensor system also has an overall upper and lower deviation of 3σ=0.02mm. shift.

The simulation calculation results show that when the asymmetric error of the upper and lower sensors (12) is controlled during calibration and measurement, the misalignment error of the middle sensor (12), and the overall relative offset of the upper and lower positions of the sensor (12) during calibration and measurement is controlled within the above range , the diameter measurement error of the large shaft to be tested is less than 1.5 μm.

It can be seen from the above analysis that the above measurement conditions can be easily satisfied through simple adjustment. The low requirements on the measuring device benefit from the implementation of technical means such as relative bow height measurement and symmetrical arrangement of upper and lower sensors in the measurement process.

Calibration errors of the calibration circle size, non-coplanar and non-parallel light rays of the sensor (12) also have a certain influence on the measurement results, which will not be explained one by one here. Due to the method of obtaining the average value by sampling multiple times a week, the influence of random measurement errors of the sensor (12), roundness of the contour, and shaft runout during the rotation process on the measurement results is greatly reduced.

Use circle 1 and circle 3 to calibrate the test system, and then measure circle 1, circle 2 and circle 3 respectively at the middle cross-section position. According to the above table, the diameters are 499.789mm, 503.601mm and 507.751mm respectively. After the calibration is completed, the three diameters are measured 20 times respectively. The deviation of the diameter measurement results of circle 1 and circle 3 is less than ±3μm, and the deviation of the diameter measurement result of circle 2 is larger, about ±4μm. It can be seen that the measurement results The system can achieve a measurement accuracy of 5 μm.

Claims (2)

1. A device for non-contact on-line measurement of the diameter of a large-scale shaft workpiece, comprising a computer (1), a speed-regulating motor (2) and a sensor (12), characterized in that: the pan-tilt (5) on the measurement base (4) Three guide rails (6) are connected by screw mandrels (7) and threads, a column (8) is housed on the base (4), and four guide rail sliders (9) are set on the column (8) and locking screws (10 ), the length of the fixed slide plate (11) of the upper and lower guide rail sliders (9) is the same and the sensor (12) is connected by the locking screw (13), and the two guide rail sliders (9) in the middle of the column (8) A slide plate (11) and a sensor (12) are connected by a locking screw (14). The length of the middle guide rail slider (9) and the slide plate (11) is shorter than that of the upper and lower slide plates (11). The distance between the sensor (12) and the computer (1) The center of the calibration base (15) is fixed with a symmetrical support seat (16). The support seat (16) is connected by the rotating shaft (17) and equipped with a bearing (18). The center of the rotating shaft (18) is equipped with Two large discs (19) and small discs (20) with different diameters, the speed-regulating motor (2) is connected and fixed on the calibration base (15) by a bracket (21), and the speed-regulating motor (2) shaft is connected with the One end of the rotating shaft (17) is connected, and the other end of the rotating shaft (17) is connected with the speed encoder (22) fixed on the bracket (21) of the calibration base (15), between the measurement base (4) and the calibration base (15) Connected by large platform (23). 2. The device for non-contact on-line measurement of the diameter of large-scale shaft workpieces according to claim 1, characterized in that: the measurement base (4) and the calibration base (15) can be used alone, and due to the abnormal shape or oversize of the measured object, the measurement Base (4) can install tripod, curved frame and other special-shaped frames.

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