JP2002148270A - Method and instrument for measuring particle velocity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the velocity of a particle, such as a projected material in a blast jet, etc., having a small particle diameter by effectively utilizing the image processing method. SOLUTION: A multiple-exposure shadow photograph, taken by photographing a jet J which is transported under pressure together with compressed air jetted from a jetjection nozzle 11 and contains the projected material P, using a stroboscope 12 and a digital camera 13, is fetched in an image processor 20 and two particle images which are estimated to be the images of the same solid particle are extracted from the shadow photograph. Then the velocity of the solid particle is calculated by measuring the moving distance of the particle by calculating the relation between the positions of the particle in the two images.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the projection velocity of solid particles in a two-phase jet in which solid particles are mixed into a gas or liquid fluid, such as a jet of a blasting material in blasting. It is about.

[0002]

2. Description of the Related Art Roughness, burrs, scales, etc. adhering to a metal surface are removed as pre-adhesion treatments for metals, and rust, burrs, scales, etc. attached to a metal surface are removed, or a coating agent attached to a jig or a mold surface is removed. As a method, abrasive sand or iron, copper,
Fine-grained projectiles, such as metal pieces such as lead and aluminum, are mixed into compressed air and pumped, and sprayed onto the surface of the treated material.
A blast treatment for polishing the surface of the treatment material is known. In order to perform such blasting efficiently,
It is necessary to appropriately control the impact force (projection force) of the shot material applied to the processing material. The above-mentioned projecting force can be estimated by measuring the ejection speed of the shot material, but at present,
An apparatus that can accurately measure the ejection speed of the blast material has not been put to practical use.

[0003]

Conventionally, as a method of measuring the velocity of a solid flying in space, a solid or a solid body is irradiated with ultrasonic waves or electromagnetic waves continuously or at predetermined intervals, and information on the reflected waves is obtained. There is a method of detecting the moving speed of the solid from the above, and a method using the laser Doppler effect, but these devices are very expensive,
The operation was complicated and impractical. That is, in the laser Doppler measurement method, since the operation of the apparatus is complicated and the apparatus is a dedicated machine, a large installation place is required,
There is a disadvantage that it is difficult to handle because expensive parts such as a laser, a camera, and a lens are integrated. In the measurement method using an ultrasonic wave or an electromagnetic wave, not only the particle diameter of the shot material is as small as 0.1 mm to 1.0 mm but also the speed is as high as 10 m / s to 100 m / s. Measurement accuracy could not be obtained. Further, a method of calculating the velocity of solid particles from the photographed image by photographing the jet by normal light photographing is also conceivable.However, since the particle size of the projection material is small, a close-up lens is used. Since the photograph must be taken in an enlarged manner, it requires not only advanced technology but also extremely strong illumination, which is not practical in terms of heat generation and power consumption.

[0004] The present invention has been made in view of the conventional problems, and a method for measuring the speed of particles having a small particle size, such as a blast material in a blast jet, by effectively utilizing an image processing method. And an apparatus thereof.

[0005]

According to a first aspect of the present invention, there is provided a method for measuring a particle velocity, wherein a multi-exposure shadow photograph of a jet in which solid particles are mixed into a fluid is taken, and then the jet photograph is selected from the shadow photographs. Extracting a particle image estimated to be at least two identical particles, measuring a moving distance of the particles, and calculating a velocity of the solid particles based on the moving distance and a photographing interval. And

According to a second aspect of the present invention, there is provided a method for measuring a particle velocity.
The method is characterized in that the particle image is taken into an image processing apparatus, and the positional relationship of the particle image on the image is calculated to measure the moving distance of the particle.

According to a third aspect of the present invention, there is provided a particle velocity measuring device for irradiating light to a jet, which is ejected from an injection means and containing solid particles mixed in a fluid, and photographing a multi-exposure shadow photograph of the jet. Means for performing image processing by capturing an image including a particle image estimated to be at least two identical particles from a shadow photograph taken by the photographing means; and Means for calculating a moving distance, and an image processing apparatus comprising means for calculating the speed of the solid particles based on the calculated moving distance and photographing interval, wherein the photographed multi-exposure shadow photograph is provided. And image processing to calculate the velocity of the solid particles.

A particle velocity measuring apparatus according to a fourth aspect of the present invention includes a means for marking and specifying an image of a particle assumed to be the same particle taken into the means for image processing, and the image of the marked particle. Means for calculating the respective position data of, and means for calculating the moving distance of the axial component and the orthogonal component of the jet flow of the particles and the rotation angle from the calculated position data of each particle image. An image processing device, and calculates the axial component and the orthogonal component of the speed of the specific particle and the rotational speed from the moving distance and the rotation angle of the calculated axial component and the orthogonal component, and the photographing interval. It is like that.

According to a fifth aspect of the present invention, in the particle velocity measuring apparatus, a transparent case is provided, the jetting means is fixed to the transparent case, and the strobe and the camera are arranged outside the transparent case. This prevents the solid particles from scattering on the strobe or camera.

According to a sixth aspect of the present invention, in the same manner as in the actual blasting process, a processing material for causing the jet to collide with the jet is disposed below the jet, and in the scattering direction of the solid particles, A baffle plate that is inclined with respect to the direction of the jet is provided to prevent the solid particles from bouncing off, so that only the falling solid particles can be photographed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing a configuration of a particle velocity measuring apparatus 10 according to the present embodiment, in which reference numeral 11 denotes an injection nozzle for injecting a blasting material P such as abrasive sand which is fed together with compressed air, and reference numeral 12 denotes a jet from the injection nozzle. A strobe for irradiating light to J, a high-resolution C for taking a multiple exposure photograph of the jet J in conjunction with the irradiation of the strobe
A digital camera 14 equipped with a CD image pickup device sets the exposure time and delay time of the digital camera 13, the number of times of multiple exposure, and the like, and controls the timing of irradiation of the strobe 12 and the timing of shooting of the digital camera 13. The controller 20 is an image processing apparatus that captures image data of a captured multiple-exposure shadow photograph, which is the output of the digital camera 13, performs image processing, and calculates the velocity of the solid particles in the jet.

FIG. 2 is a block diagram showing the configuration of the image processing apparatus 20, wherein 21 is image data input means, 22 is image operation means having a keyboard and a mouse, and 23 is a multi-exposure shadow photograph taken. Image data calculating means for calculating the position data of the particle image in the image, 24 is a moving distance calculating means for calculating the moving distance of the particles from the image of the position data particles, 25 is the calculated moving distance, A particle velocity calculating means for calculating the velocity of the solid particles based on the multiple exposure shooting interval sent from the controller 15, displays a multi-exposure shadow photograph image input from the video data input means 21. This is a display which is an image display means for displaying. The photographing interval of the multiple exposure may be input by using the image operation unit 22. The image data calculator 23 extracts at least two particle images estimated to be the same particle from the particle images captured by the image processing device 20 and calculates respective position data. The same particle is estimated by software
This is possible by calculating the coordinates of the contour of each particle image and estimating a substantially congruent particle image, but since there are many particle images and a part of the particle images overlaps, the calculation process becomes complicated, In the present embodiment, the measurer estimates the same particle image on the screen of the display 26, operates the image operation means 22, and preliminarily marks the contours of the two estimated particle images. The position data of the two marked particle images is calculated by the image data calculating means 21. The moving distance calculating means 24 calculates the moving distance of the axial component and the orthogonal component of the jet and the rotation angle of each of the particles from the calculated position data of each particle image. The particle velocity calculation means 25 calculates the axial distance component and the orthogonal component of the velocity of the specific particle, the rotation speed, and the calculated moving distance and rotation angle of the axial component and the orthogonal component, and the shooting interval. Is calculated.

Next, a method for measuring the particle velocity will be described. In the present embodiment, as shown in FIG. 3, a blast chamber for measurement composed of a transparent case (hereinafter, referred to as a blast chamber).
15, the spray nozzle 11 is installed on the ceiling 15 a, and a work holding table 16 is provided at the center of the blast chamber 15 in the same manner as in the actual blasting process.
The projection material P ejected from the ejection nozzle 11 together with the compressed air is caused to collide with the workpiece W, and the projection material P
While irradiating light from a strobe onto the jet J including the jet, the digital camera 13 is used to perform two shadow shootings of the state of the jet J at a predetermined shooting interval. Image processing of the shadow photograph is measured to measure the falling speed of the projection material P. In FIG. 3, the controller 14 and the image processing device 20 are omitted. The digital camera 13 and the strobe 12 are connected to the blast chamber 15
The strobe 12 is set so that the irradiation light of the strobe 12 directly enters the lens of the digital camera 13 that performs shadow shooting. In addition, since it is shadow photography, it is not necessary to make the irradiation light from the strobe 12 particularly strong. The lens of the digital camera 13 is appropriately selected depending on the size of the projection material P to be photographed, the ejection pressure, and the like, and a close-up lens or a zoom lens may be used as necessary. The photographing interval and the exposure time are adjusted according to the speed of the projection material P so that the positions of the particle images photographed twice can be identified. In addition, Z is a shutter provided at the upper part of the blast chamber 15 for blocking the jet flow from the injection nozzle 11, and is normally in an open state.

In the scattering direction of the projection material P by the work W, a plurality of baffle plates 17 inclined in directions opposite to each other with respect to the direction of the jet flow J are provided alternately in a plurality of stages in the upward and downward directions. P is prevented from rebounding. As a result, the blasted projection material P is applied to the falling baffle plate 1.
7 flows downward along the inclined surface and falls on the floor surface 15d of the blast chamber 15, so that only the falling shot material P can be photographed. The blast material P that has dropped onto the floor surface 15d of the blast chamber 15 is discharged to the outside of the blast chamber 15 from the suction port 18S of the suction means 18 provided below the side surface (here, the side surface 15c) of the blast chamber 15. . In addition,
When measuring the weight of the projection material P injected at a predetermined time, the shutter Z is opened and closed at a predetermined timing, and a collection tank 19 for collecting the dropped projection material P is disposed below the baffle plate 17. Then, the dropped projection material P is collected.

FIG. 4A is a schematic view showing an image of a multiple exposure shadow photograph taken into the image processing apparatus 20 and displayed on the screen of the display 26. Is operated, and a keyboard or a mouse as the image operation means 22 is operated to perform marking along the contours of the estimated two particle images A and B, respectively, as indicated by the thick solid line in FIG. In the present embodiment, since the measurer estimates two identical particles from the image, for example, the user operates the keyboard or the mouse as the image operating means 22 to obtain the outlines of the two estimated particle images A and B. Are marked along with the solid line shown in FIG. In the present embodiment, since the measurer estimates the same particle image on the screen of the display 26 and marks the contour of the particle image, for example,
As shown in FIG. 4B, even when the same particle images C and D partially overlap, the contour of the particle images C and D of the particles can be marked.

Next, as shown in FIG. 5, the position data of the two particle images A and B which are estimated and marked as the same particle image are calculated by the image data calculating means 21.
Note that, on the screen, the falling direction of the blast material P is the X axis, the direction perpendicular to the falling direction is the Y axis, and the origin O of the coordinate axis is the position of the injection port of the injection nozzle 11. Image data calculation means 2
1 reads the coordinates of the contours of the particle images A and B, calculates the coordinates of the respective centers of gravity G and g, and sends them to the moving distance calculating means 24 as position data of the particle images A and B. When the distance between the particle images A and B is a certain distance, the particle images A and B specified on the screen by the measurer are used.
There is no problem in terms of accuracy even if the points within are used as the centers of gravity G and g. The moving distance calculation means 24 calculates the distance L between the calculated center of gravity positions G and g, and uses this as the moving distance of the jet of the particle image. The moving distances of the axial component and the orthogonal component are obtained as orthogonal projections x and y of the distance L, and the rotation angle θ is a line segment connecting the origin O, which is not on the screen, and the center of gravity G, g. It is obtained as an angle between OG and Og. The particle velocity calculation means 25 calculates the velocity V of the particle by the following equation based on the calculated moving distances L, x, y and the rotation angle θ and the shooting interval T1 of the multiple exposure sent from the controller 14. And its axial component u and orthogonal component v, and the rotational speed ω. V = L / T1, u = x / T1, v = y / T1 ω = θ / T1 In the present embodiment, axial components u _i of a plurality of particle velocities are used.
= / T1 (i = 1, 2, ‥‥) was measured, and the average value was defined as the falling speed of the blast material P.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With the use of the particle velocity measuring device 10 having the above-described structure, the ejection pressure of a blast material (pressure immediately before a nozzle) is changed.
The shooting speed of the blasting material was measured by appropriately selecting the photographing interval T1 and the exposure time T2, photographing a multi-exposure shadow photograph, and performing image processing. The results are shown in Table 1 below.

[Table 1] From Table 1 above, the falling speed of the blast material increases as the ejection pressure increases, but it is not always proportional to the ejection pressure. It was confirmed that it was necessary to measure

In the above embodiment, the data of the multi-exposure shadow photograph taken by the digital camera 13 is taken into the image processing device 20 and subjected to image processing to calculate the velocity of the solid particles in the jet. After taking a shadow photograph using a camera of the formula, the shadow photograph may be developed, the developed photograph may be read by a scanner or the like, digitized, and loaded into the image processing apparatus 20. In the above example, the number of multiple exposures is set to two. However, the number of multiple exposures is not limited to this, and the number of multiple exposures, the shooting interval, and the exposure time are appropriately determined according to the injection pressure, the type of the projection material P, and the like. Is what is done. In addition, the measurement distance and the rotation angle can be determined by marking the user along the contours of the two estimated particle images A and B on the screen, and then dragging one of the particle images by operating the mouse. By rotating on the keyboard, a movement / rotation operation may be performed so as to overlap the other particle image, and the movement and rotation may be obtained from the movement amount and the rotation amount. This operation is particularly effective when a part of the same particle image is overlapped. In addition, depending on the type of the projection material P, the shape of the particles may be uniform and it may be difficult to distinguish the particles. In such a case, test particles having a characteristic shape are mixed with the projection material and ejected. The particle velocity may be obtained.

[0019]

As described above, according to the present invention,
After taking a multi-exposure shadow photograph of the jet in which the solid particles are mixed into the fluid, the above-mentioned shadow photograph is taken into an image processing device, and from among the above-mentioned shadow photographs, at least two particles on the image of the particle image estimated to be the same particle are taken. Since the velocity of the solid particles is calculated by calculating the positional relationship in the above and calculating the moving distance of the particles, the speed of particles having a small particle size, such as a blast material in a blast jet, can be accurately calculated. And it can be easily measured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a particle velocity measuring device according to the present embodiment.

FIG. 2 is a block diagram illustrating a configuration of an image processing apparatus.

FIG. 3 is a schematic view showing the appearance of a particle velocity measuring device.

FIG. 4 is a view showing a particle image of a shadow photograph of multiple exposure.

FIG. 5 is a diagram showing a method for measuring the moving speed of particles.

[Explanation of symbols]

10 particle velocity measuring device, 11 injection nozzle, 12 strobe, 13 digital camera, 14 controller,
15 Blasting chamber for measurement, 16 Work holder, 17
Baffle plate, 18 suction means, 18S suction port, 19 recovery tank, 20 image processing device, 21 video data input means, 22 image operation means, 23 image data calculation means,
24 moving distance calculating means, 25 particle velocity calculating means, 2
6 Display.

Claims (6)

[Claims] 1. After taking a multi-exposure shadow photograph of a jet in which solid particles are mixed in a fluid, at least two particle images presumed to be the same particle are extracted from the shadow photograph to move the particles. A method for measuring the velocity of a particle, comprising measuring a distance and calculating a velocity of the solid particles. 2. The apparatus according to claim 1, wherein said particle image is taken into an image processing apparatus, and a positional relationship of said particle image on the image is calculated to measure a moving distance of said particle.
The method for measuring the particle velocity according to the above. And a photographing means for photographing a multi-exposure shadow photograph of the jet, the photographing means comprising: a means for irradiating light to a jet, which is ejected from the jetting means and containing solid particles in a fluid; Means for taking in an image containing at least two particle images presumed to be the same particle from the taken shadow photograph and performing image processing; means for calculating a moving distance of the particle from the image of the particle; An image processing device comprising: means for calculating the velocity of the solid particles based on the determined moving distance and the photographing interval. 4. The image processing apparatus further comprises means for marking and specifying an image of a particle assumed to be the same particle taken into the image processing means, and a position of each of the marked particle images. Means for calculating data, and from the calculated position data of each particle image,
The particle velocity measuring device according to claim 3, further comprising: means for calculating a moving distance of an axial component and an orthogonal component of the jet of the particles and a rotation angle. 5. A transparent case, wherein said jetting means is fixed to said transparent case, and said light irradiating means and photographing means are arranged outside said transparent case. The particle velocity measuring device according to claim 4. 6. A treatment material for colliding the jet flow is provided below the jet flow, and a baffle plate inclined in the direction of the jet flow in the direction of scattering the solid particles is provided. The particle velocity measuring device according to claim 5.