RU2534720C1 - Method of determining angle of thread twist - Google Patents

Abstract

FIELD: textiles, paper.

SUBSTANCE: in the method the analysis of the angular diagram of the light flow distribution in the diffraction pattern observed from the test material with illumination of the thread surface by parallel beam of monochromatic coherent light with a circular cross section, and the magnitude of the desired angle of twist is determined according to the angle measured between the direction to the maximum in the angular diagram of the light flux in the diffraction pattern, and the perpendicular to the thread, made in the plane of the pattern from its centre. And the computer microimage of the thread under study is examined, the diffraction pattern from which for this lighting is calculated using the fast two-dimensional Fourier transformation, and the angular diagram of the light flux distribution in the diffraction pattern is determined according to the diagram of the angular distribution of the average total intensity of illumination of pixels I_ΔS(φ), which is calculated in the ring, set by the radii R₁ and R₂ relative to the centre of the diffraction pattern in the polar coordinate system for each value of the angle φ in the range of values of 0-2π; by the formula $$I_{\Delta S}(\varphi )=\frac{{\displaystyle \sum _{n=1}^N{i}_{p_n}}}{N},$$

where ΔS is the square of the ring sector limited by the angle Δφ; the numerator is the sum of the intensities of image pixels i_p held in the selected sector ΔS; N is the number of pixels in ΔS.

EFFECT: improvement of measurement accuracy by reducing the measurement error, while simultaneous simplifying the measurement process.

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Description

The invention relates to non-destructive methods for measuring the angle, twist of the thread, that is, the angle of inclination of the strands from which the investigated thread is twisted, to the axis of the thread and can be used in solving issues of automatic control of this parameter.

There is a method of directly measuring the angle of twist of the thread using a microscope when illuminating the thread "for reflection" [Davydov AF Textile materials science. Tutorial. Russian Correspondence Institute of Textile and Light Industry. M., 1997, p. 54].

The method consists in the fact that the necessary measurements are made under a microscope, for example, using an angular grid mounted in the eyepiece of the microscope. The method is subjective and cannot be used with automatic control.

There is a calculation method for finding the twist angle α _K according to the formula

where d is the estimated diameter of the thread; h is the height of the turn; K = 1 / h - the value of the twist of the thread [Kukin G.H. Textile Materials Science (fibers and threads): Textbook for high schools. 2nd ed., Revised. and add. / G.H. Kukin, L.H. Soloviev, L.I. Koblyakov. - M .: Legprombytizdat, 1989, p. 38-39]. The disadvantage of this method is the difficulty in determining the estimated diameter of the thread twisted from strands, since the cross section of the thread is not a circle, and the thread itself is not cylindrical. In addition, this method requires measuring the value of the twist of the thread, which is still being implemented in factory laboratories using a twist gauge, a device that calculates the number of torsions of a sample of thread of a given length when it is fully untwisted. At the same time, the operation is monitored visually, that is, this method also cannot be used to automatically control the twist angle of the thread.

Closest to the claimed method is an optical method for controlling the angle of rotation of the thread [Patent USA 5210594 May 11, 1993 Process And Device For Measuring The Twist Of A Textile Yarn], which consists in analyzing the angular diagram of the distribution of light flux in the diffraction pattern observed from the studied material when the surface of the filament is illuminated by a parallel beam of monochromatic coherent light with a circular cross section, and the magnitude of the desired twist angle is judged by the angle measured between the direction to the maximum in the angular diagram of the light outflow in the diffraction pattern, and perpendicular to the filament drawn in the plane of the picture from its center. In this method, the diameter of the light beam is fundamentally chosen smaller than the diameter of the investigated filament. An analysis of the diffraction pattern obtained in reflected light is carried out using a screen in the center of which there is a light transmission gap. A screen with a slit can rotate around a vertical axis, coaxial to the perpendicular drawn from the center of the diffraction pattern. The direction of the slit is recorded at which the light flux passing through the slit has a maximum value corresponding to the direction to the maximum in the angular diagram of the distribution of the light flux in the diffraction pattern.

The disadvantages of this method include:

1. The method is suitable for determining the twist angle of a multifilament yarn twisted from multiple monofilaments, but is completely unsuitable for controlling the twist angle of yarns twisted from multifilament yarns (strands). The fact is that in this method the diameter of the light beam is fundamentally chosen smaller than the diameter of the investigated thread, but in fact, as follows from the description of the corresponding device that implements the method, this spot is focused using lenses on the studied surface of the thread. In this case, in the angular diagram of the light flux coming from the diffraction pattern, the direction of the fibers in the twisted strand will be reflected, which obviously depends both on the magnitude and direction of the twist of the fibers in each strand, and on the direction and magnitude of the twist of the thread. That is, in this case, not the twist angle of the thread will be measured, but a certain total orientation angle of individual fibers in the strand.

2. It is obvious that during the movement of the complex filament with a relatively small light spot, the distribution of the light flux and its value in the diffraction pattern will substantially change due to the uneven note in the orientation of the elementary fibers of the studied filament, the hairiness of the filament, and differences in the orientation of neighboring fibers, the larger less light spot. This should greatly reduce the measurement accuracy, which obviously should also depend on the optical properties and geometry of the elementary fibers.

3. The device used to implement it is difficult to manufacture, expensive, requires precision tuning and qualified service.

The aim of the present invention is to eliminate these disadvantages, namely, improving the accuracy of the measurement by reducing the measurement error while simplifying the measurement process.

которую рассчитывают в кольце, задаваемом радиусами R₁ и R₂ относительно центра дифракционной картины в полярной системе координат для каждого значения угла φ в диапазоне значений 0-2π; по формулеThis goal is achieved by analyzing the angular diagram of the distribution of light flux in the diffraction pattern observed from the material under study when the surface of the filament is illuminated by a parallel beam of monochromatic coherent light with a circular cross section, and the magnitude of the desired twist angle is judged by the angle measured between the direction to the maximum the angular diagram of the light flux in the diffraction pattern, and perpendicular to the filament drawn in the plane of the picture from its center, characterized in that blowing computer microimage investigated the filament, from which the diffraction pattern for this coverage is calculated using the two-dimensional fast Fourier transform, and an angular distribution diagram of the light flux in the diffraction pattern is judged by the average angular distribution diagram of the total intensity of illumination of pixels

which is calculated in a ring defined by the radii R ₁ and R ₂ relative to the center of the diffraction pattern in the polar coordinate system for each value of the angle φ in the range of 0-2π; according to the formula

where ΔS is the area of the sector of the ring bounded by the angle Δφ; the numerator is the sum of the intensities of the image pixels i _p that fall into the selected sector ΔS; N is the number of pixels in ΔS.

Significant differences of the proposed solutions are:

1. "examine the computer microimage of the investigated filament." The prototype investigated the illuminated portion of the investigated filament, which was illuminated by monochromatic coherent light.

2. "the Fraunhofer diffraction pattern from which for such illumination is calculated using the fast two-dimensional Fourier transform", that is, in the case when the wave front coincides with the plane of the microimage of the investigated filament. In the prototype, a diffraction pattern is created by the scattering of light coming not only from reflection from the surface of the outer fibers, but also due to the re-reflection of light from fibers located in the depth of the illuminated volume. This picture in the prototype is displayed on an opaque screen with a gap. Diffraction in this case is not Fraunhoferian and theoretically in the general case cannot be calculated.

которую рассчитывают в кольце, задаваемом радиусами R₁ и R₂ относительно центра дифракционной картины в полярной системе координат для каждого значения угла φ в диапазоне значений 0-2π; по формуле3. “the angular distribution diagram of the light flux in the diffraction pattern is judged by the angular distribution diagram of the average total pixel illumination intensity

which is calculated in a ring defined by the radii R ₁ and R ₂ relative to the center of the diffraction pattern in the polar coordinate system for each value of the angle φ in the range of 0-2π; according to the formula

where ΔS is the area of the sector of the ring bounded by the angle Δφ; the numerator is the sum of the intensities of the image pixels i _p that fall into the selected sector ΔS; N is the number of pixels in ΔS.

In the prototype, the analysis of the angular diagram of the distribution of the light flux in the diffraction pattern is carried out by rotating the screen with a slit around a vertical axis, coaxial to the perpendicular drawn from the center of the diffraction pattern. The direction of the slit is recorded at which the light flux passing through the slit has a maximum value corresponding to the direction to the maximum in the angular diagram of the distribution of the light flux in the diffraction pattern.

в рассчитанной дифракционной картине.Figure 1 explains the meaning of the notation made in the claims (a) and the work of the proposed solution (b). In FIG. 1-a shows the diffraction pattern from the microimage of the filament located during the survey along the ordinate axis, calculated using the two-dimensional fast Fourier transform program [Shlyakhtenko PG, Kofnov OV, Nefedov VP "The Fourier program for processing micro-images of the surface of textile materials to determine the values of the periodic parameters of the investigated structure." RU OBPBT No. 4 (81). Computer Programs. Reg. number 2012618350 (09/14/2012)]. The program made it possible to perform the subsequent calculation of the Fourier transform when illuminating the studied microimage with a round light spot with an exponential decrease in the light intensity from its center to the periphery, which models laser illumination well. In the center of the calculated diffraction pattern there is always a point with a maximum light intensity, around which a ring with radii R ₁ and R ₂ is described, in whose area a diagram of the angular distribution of the average total pixel illumination intensity is calculated

in the calculated diffraction pattern.

была создана программа, результаты работы которойTo calculate this distribution on a personal computer using the formula

a program was created, the results of which

shown in figures 1-6.

From this figure it is seen that the angular diagram is oriented in nature, so that the maximum distance from the center of the diagram corresponds to the direction in which the intensity of the maxima in the diffraction pattern has a maximum value (Figure 1-a). The program determines the value of the angle between the abscissa axis and this direction and displays it in digital form along with the value of the twist direction of the studied thread S or Z (Fig.1-b).

Figure 2-a, b shows computer microimages of the thread patterns (a) with the S-direction (I) and Z-direction (II) of the twist and the corresponding results of their computer processing (b).

Figure 3-a, b shows similarly arranged microimages of real threads (a) twisted from 2 (I, II) and 3 (III, IV) of the same metal wires (strands) with S-direction (I, III) and Z - direction (II, IV), taken with a Leica computer microscope.

Figure 4-a, b shows similarly located microimages of textile threads:

I - beige thread from polyester with a linear density of 26.8 tex with a twist direction Z;

II - blue thread of the brand "bestex" made of polyester with a linear density of 40 tex with a twist direction Z;

III - red thread from a mixture of cotton and viscose with a linear density of 39.2 tex with a twist direction S;

IV - white cotton thread with a linear density of 96.08 tex with twist direction S.

From a comparison of the data of Figures 2-4, it can be seen that the direction to the maximum of the angular diagrams (b) in all cases coincides with the direction of the perpendicular drawn to the direction of inclination of the strands of the investigated fiber in its center (a). Therefore, the controlled angle between the perpendicular to the direction of the thread (abscissa axis) and the direction to the maximum of the angle diagram is equal to the measured twist angle between the slope of the strand in the center of the thread and the axis of the thread coinciding with the ordinate axis (like angles with mutually perpendicular sides).

The results of calculating the magnitude of this angle for all studied samples of the threads were checked directly under the microscope when measuring the angle of twist of the thread. In all these cases, the observed difference with a confidence probability of P = 0.9 did not exceed the error of the microscopic method (± 0.5 °).

It should be noted that the result of calculations according to the claimed solution does not depend on the color and nature of the material of the investigated yarn.

The experimental data indicate that the inventive non-hardware method is workable.

Claims (1)

The method for determining the twist angle of the thread, which consists in analyzing the angular diagram of the distribution of light flux in the diffraction pattern observed from the material under study by illuminating the surface of the thread with a parallel beam of monochromatic coherent light with a circular cross section, and the magnitude of the desired twist angle is judged by the angle measured between the direction to the maximum in the angular diagram of the light flux in the diffraction pattern and the perpendicular to the filament drawn in the plane of the picture from its center, yuschiysya that examined computer microimage investigated the filament, from which the diffraction pattern for this coverage is calculated using the two-dimensional fast Fourier transform, and an angular distribution diagram of the light flux in the diffraction pattern is judged by the average angular distribution diagram of the total intensity of illumination of pixels $$I_{\Delta S}(\varphi )$$

calculated in the ring defined by the radii R ₁ and R ₂ relative to the center of the diffraction pattern in the polar coordinate system for each value of the angle φ in the range of values
0-2π by the formula
$$I_{\Delta S}(\varphi )=\frac{{\displaystyle \sum _{n=\mathrm{one}}^N{i}_{p_n}}}{N}$$

,
where ΔS is the area of the sector of the ring bounded by the angle Δφ; the numerator is the sum of the intensities of the image pixels i _p that fall into the selected sector ΔS; N is the number of pixels in ΔS.

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