CN201034557Y - On-line imaging detection device for machining accuracy of inner and outer walls of cylinder - Google Patents

Abstract

The utility model belongs to an online detection system based vision, in particular to an online imaging detection device for detecting the machining accuracy of the inner wall and outer wall of cylinder. The device includes a shell (1), a laser (2), a reflector (3), a light way conversion mirror (4) and a part for receiving and processing images. After the laser generated by the laser (2) is reflected by the reflector (3), the laser is cast on the detecting the inner surface of the cylinder. The diffuse reflection light spot is caught by the light way conversion mirror (4), which is assembled to the receiving and processing images part for processing. The part for receiving and processing images (5) includes an image acquisition and processing module, a digital signal processing module, a data preservation module and a data transferring and displaying module. The image of diffuse reflection light spot is collected and processed by the image collecting and processing module. The data from the image collecting and processing module is received by the data single processing module, after operation processing, the relative results are stored in the data preservation module.

Description

On-line imaging detection device for machining accuracy of inner and outer walls of cylinder

technical field

The utility model belongs to the field of on-line detection systems based on vision, in particular to an on-line imaging detection device for processing precision of inner and outer walls of a cylinder.

Background technique

The precursor process of cylindrical products is stamping and forming of high temperature steel. Due to vibration and wear, stamping equipment will have a large deviation after working for a period of time. For the above-mentioned deviation, the traditional solution is: punch a batch of cylinders, sample inspection after cooling, if unqualified, the batch will be scrapped, and the stamping equipment will be corrected at the same time, so as to continue production. There is a lot of waste in the above-mentioned traditional method, and it also greatly limits the working speed of the production line.

Based on the complexity of the shape factor of the object to be measured, the algorithm design must also have certain complexity. The cylinder to be tested has a small mouth, a large abdomen, and a bottom. It cannot be directly projected or remotely measured from the outside. It must have a detection device that extends into the inner wall to detect it. The measurement of the object to be measured generally includes two parts: the measurement of the inner wall point position and the fitting of the inner and outer wall positions. The surface of the inner wall is not smooth, the site conditions are complex, and the image noise is large, so it is necessary to design the algorithm accurately in combination with experiments. The fitting of the surface data of the inner and outer walls requires fitting the inner and outer wall planes from the position data of the inner and outer wall points, and calculating the uniformity of the inner and outer walls.

For the position detection of the inner wall point, there are the following candidate schemes:

1) Probe contact measurement

The probe is used to contact the surface of the object to be measured, and the surface uniformity of the object is determined according to the displacement of the probe. The disadvantages are:

1. The probe touches the surface of the object to be measured, but in this system, the surface of the object to be measured has high temperature and high hardness, and the probe is easy to be worn.

2. The probe is a mechanical structure, which needs a mechanical transmission device for precise displacement when moving, and the scanning speed is slow, which cannot meet the requirements of flow detection on the production line.

2) Infrared measurement

Irradiate the surface of the object with an infrared light source, and determine the surface uniformity of the object according to the reflected infrared rays. The disadvantages are:

1. The cylinder to be tested has a small mouth and a large belly, so it is difficult for infrared rays to scan the entire surface.

2. The material of the cylinder is high temperature steel, and the surface is covered with a black oxide layer, so the surface of the cylinder is a slightly rough black surface. This surface has a strong absorption of infrared rays, and it is difficult to obtain effective reflection characteristics.

3) Ultrasonic measurement

The uniformity of the object to be tested is determined by measuring the time of the entire process of ultrasonic transmission and reflection inside the object, and measuring the time of its emission and recovery. The disadvantages are:

1. The ultrasonic generating device needs to contact the surface of the object to be tested. The high temperature on the surface of the cylinder is easy to cause corrosion and wear to the ultrasonic generating device. The oxide layer on the surface of the cylinder makes the contact of the ultrasonic generating device not tight.

2. The high temperature of the cylinder has a great influence on the propagation speed of the ultrasonic wave, which is essentially a vibration wave, and the measurement accuracy will also be affected.

4) Laser measurement

A beam of laser light is irradiated on the surface of the object, and the change of the reflected laser intensity or the position of the spot is measured to detect the uniformity of the inner wall. The disadvantages are:

1. The mouth of the cylinder to be tested is small and the belly is big, so it is difficult for the laser to scan the entire surface.

2. The calculation is more complicated.

5) Visual measurement.

The light source is used to irradiate the object to be measured, and after the image is collected by the image sensor, three-dimensional fitting is performed to calculate the uniformity of the inner wall. The disadvantages are:

1. The cylinder to be tested has a small mouth and a big belly, and the light source cannot be directly irradiated, so it is difficult to directly collect images.

After comparison and analysis, it can be seen that the detection of the position information of cylindrical products by any single method mentioned above is difficult to meet the requirements of the detection of the inner and outer walls.

Utility model content

The utility model aims to overcome the deficiencies of the prior art and provide an online imaging detection device for processing precision of inner and outer walls of a cylinder with high detection efficiency, small environmental impact factors and high measurement accuracy.

The purpose of this utility model is achieved in this way: the online imaging detection device for the machining accuracy of the inner and outer walls of the cylinder, which includes: a housing, a laser, a reflector, an optical path conversion mirror, and an image receiving and processing part; the laser, the reflector and the optical path conversion The mirror is installed in the casing; the laser light emitted by the laser is reflected by the mirror and projected onto the inner wall surface of the cylinder to be tested to form a diffuse reflection spot; the optical path conversion mirror captures the diffuse reflection spot and converges it to the image receiving and processing partially processed.

As a preferred solution, the optical path conversion mirror of the present invention uses a triangular prism; the laser converted by the optical path conversion mirror is parallel to the incident light emitted by the laser.

As another preferred solution, the image receiving and processing part of the utility model may include: an image acquisition and processing module, a digital signal processing module, a data storage module, and a data transmission and display module; the image acquisition and processing module collects diffuse reflection spot images and process it; the digital signal processing module receives the data from the image acquisition and processing module, and after performing calculation processing, stores the relevant results in the data storage module; to display.

As a third preferred solution, the utility model can also be equipped with a USB interface, a network interface or a UART chip; the UART chip and the digital signal processing module realize data exchange.

The utility model has high detection efficiency, can realize the automatic detection of the uniformity of the inner and outer walls of the cylinder, and can judge whether the cylinder is qualified or not. If it is qualified, it will pass normally, if it is not qualified, it will send an alarm signal, and at the same time, whether it is qualified or not, the measurement data can be retained for inspection. In terms of function, it can be roughly decomposed into three parts, including the location of inner wall points, the location of outer wall points, and the fitting of inner and outer wall points. In the working environment, the system can work stably for a long time under the harsh conditions of high temperature. In terms of measurement indicators, the measurement accuracy and range must meet the product requirements, and the measurement speed must meet the work requirements of the production line.

Description of drawings

Below in conjunction with accompanying drawing and specific embodiment, the utility model is further described. But the protection scope of the present utility model will not only be limited to the expression of following content.

Fig. 1 is the schematic diagram of the object to be measured of the utility model;

Fig. 2 is the principle schematic diagram of the utility model laser triangulation method;

Fig. 3 is a schematic diagram of the improved principle of the optical path of the utility model;

Fig. 4 is the utility model system workflow model diagram;

Fig. 5 is a structural schematic diagram of the optical detection part of the utility model system;

Fig. 6 is a schematic diagram of the hardware structure of the image receiving and processing part of the system of the present invention;

Fig. 7 is a circuit schematic diagram of the image receiving and processing part of the utility model.

Detailed ways

The utility model takes into account the non-contact method to avoid wear and corrosion and the requirements of high speed and high precision, and also considers the limitation of not being able to directly irradiate with light, the system decides to adopt a combination of laser detection and visual detection, and according to the The method of improving the particularity of the measurement target is designed by the laser triangulation detection method with two optical path changes.

As shown in Figure 5, the utility model system includes: a housing 1, a laser 2, a reflector 3, an optical path conversion mirror 4, and an image receiving and processing part 5; the laser 2, the reflector 3 and the optical path conversion mirror 4 are assembled on Inside the casing 1; the laser light emitted by the laser 2 is reflected by the reflector 3 and projected onto the inner wall surface of the cylinder to be tested to form a diffuse reflection spot; the optical path conversion mirror 4 captures the diffuse reflection spot and converges it to the image receiving The processing part is processed. The optical path conversion mirror 4 is a triangular prism; the laser light converted by the optical path conversion mirror 4 is parallel to the incident light emitted by the laser 2 . The image receiving and processing part 5 includes: an image acquisition and processing module, a digital signal processing module, a data storage module, and a data transmission and display module; the image acquisition and processing module collects diffuse reflection spot images and processes them; the digital signal The processing module receives the data from the image acquisition and processing module, performs calculation and processing, and then stores the relevant results in the data storage module; the data transmission and display module displays the position information of the inner wall of the cylinder. The utility model system is also equipped with a USB interface, a network interface and a UART chip; the UART chip realizes data exchange with the digital signal processing module.

The realization of the system function of the utility model is mainly composed of three parts, including the position detection of the inner wall point, the position detection of the outer wall point, and the fitting of the position data of the inner and outer wall points. Among them, the detection of the position of the outer wall point is less difficult due to the openness of the detection surface, and there are many methods, so it is not the main focus of the research. The fitting of the position data of the inner and outer wall points is relatively mature in research, and the research results are relatively rich, and it largely depends on the data collection of the inner and outer wall point positions, so it is not the main difficulty of the research. The detection of inner wall points is most restricted by time, space, environment, etc., which is the focus and difficulty of function realization. Therefore, the functional analysis and model establishment are mainly based on the position detection of inner wall points.

Due to the limitations of cylinder shape, material and temperature, the position detection of cylinder inner wall point is the most complicated part of the system. Now start the analysis from the characteristics of the cylinder to be measured.

Cylindrical Shape Features

  Dimensions The overall shape is cylindrical, the mouth is small, the abdomen is large, and there is a bottom Material and temperature The high-temperature steel is stamped and formed by the precursor process, and the surface temperature is very high. The surface of the cylinder is covered with a layer of black oxide layer

Inner wall detection requirements The detection accuracy and range requirements of the inner wall position meet the product quality requirements and the detection time is as short as possible

The cylinder is cylindrical as a whole, and the inner wall is a slightly irregular cylindrical surface. The horizontal cross-section of the inner wall is circular, and the points on the circumference can be sampled according to the radial direction to measure the circle, and then the circles at different horizontal positions can be used to fit the cylindrical surface. Then the detection of the cylindrical surface of the inner wall can be simplified as the position detection of the points on the inner wall.

Due to the openness of the outer wall, the selection of the outer wall point position detection scheme is only limited by the material, without the limitation of space and shape, and the range of scheme selection is relatively large. Considering the convenience of data fitting of inner and outer wall points, the same method as that of inner wall points can be used for detection. Considering the openness of outer wall point detection, methods such as parallelism can be used to increase the number of sampling points and improve measurement accuracy. Other simple and efficient methods can also be considered. Here, no more details.

Selection of system hardware working platform

Since the system requires high precision and high speed, a large number of mathematical operations are required, and a powerful computing platform is required. Therefore, a high-performance processor is required for data processing. The environmental conditions of the system are very demanding, and it is difficult for a general-purpose computer to meet the requirements, so the embedded microprocessor is selected for embedded development.

The embedded microprocessor has a small appearance, which is convenient for embedding into the system and for thermal insulation protection. The embedded microprocessor has low energy consumption and high efficiency, and is suitable for industrial inspection applications.

On the basis of the powerful computing capability of the embedded microprocessor, the image sensor is used to collect visual images. Image sensors can directly output digital image signals and integrate some basic image processing functions. The subsequent circuit design is simplified and the image acquisition quality is improved.

The hardware design is carried out by combining the embedded microprocessor and the image sensor, which saves a lot of space. Therefore, you can even consider isolating the hardware system if the operating temperature of the system becomes an obstacle.

The inner wall point detection adopts the method of combining laser detection and visual detection, and improving it according to the particularity of the target to be measured, and the laser triangulation detection method with optical path change is designed. First analyze the working principle of the laser triangulation method, and then introduce the method of the utility model.

1. Working principle of laser triangulation (as shown in Figure 2)

The laser triangulation method is composed of a laser, a focusing lens, an imaging lens and a photoelectric sensor. After passing through the focusing lens, the laser light emitted by the laser is projected onto the surface of the measured object to form a diffuse reflection spot. The diffuse reflection spot is used as the sensing signal, and the collected reflected light is focused on the focal plane of the imaging lens by using the principle of lens imaging, where the photoelectric sensor is placed. When the diffuse reflection spot moves with the surface of the measured object, the imaging spot moves correspondingly on the surface of the photoelectric sensor. According to the size of the image movement distance and the structural parameters of the sensor, the displacement of the surface of the measured object can be determined. The laser beam is like a mechanical probe for contact measurement, which can determine the position of the measured point on the surface. In order to reduce the impact of the measured surface quality on the measurement, the triangulation measurement method in which the laser beam is vertically incident on the surface of the measured object is usually used.

In the figure, s is the surface displacement of the object to be measured, s' is the relative displacement of the light spot on the surface of the object to be measured on the sensor, a is the object distance from the lens to the object, b is the image distance from the lens to the imaging surface, and θ is the observation angle. According to the relevant references, the relationship between s’ and s can be obtained from the knowledge of geometrical optics as follows,

$\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}{\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; \&PlusMinus;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}$

When the measured distance is greater than the reference distance, take the minus sign, and take the plus sign when it is smaller than the reference distance.

2. Analysis of the principle of optical path improvement (as shown in Figure 3)

Due to the limitation of the shape of the cylinder, the laser cannot irradiate the entire inner wall surface; due to the high temperature and small inner diameter of the cylinder, the laser triangulation device cannot extend into the cylinder for detection, so the basic laser triangulation method needs to be improved.

1. Use mirrors to reflect the laser and change the laser light path. The detection device extends into the cylinder, and a reflector is placed to change the incident laser light path parallel to the inner wall surface to illuminate the inner wall surface vertically. This allows vertical placement of the laser at a long distance outside the cylinder.

2. Use a prism as an observation device to observe the imaging inside the prism. Similarly, a triangular prism for the refraction light path is placed in the part where the detection device extends into the cylinder. The angle of the prism has been carefully designed so that the visual image acquisition device can be placed vertically at a long distance outside the cylinder to collect the image formed by the prism to observe the displacement of the laser diffusion spot.

Advantages of the above design:

1. The mirror placed at 45 degrees makes the laser light path perpendicular to the surface of the inner wall, which can reduce the error of laser triangulation detection and facilitate calculation.

2. The two reflections that occur in the prism are all total reflections. Therefore, on the one hand, there is no loss of reflected light energy in theory. On the other hand, in optical theory, the final real image formed by the prism is equal in size and direction to the actual object. The same, but with some changes in relative distance.

The working model of the system is designed according to the improved laser triangulation detection method with two optical path changes. The system workflow model is shown in Figure 4.

The cylinder moves on the conveyor belt of the production line, and stops after reaching the position of the detection device for detection. The detection device extends into the inside of the cylinder for detection, and after the detection is completed, the device is pulled out. If the detection result is qualified, the conveyor belt will be notified to move on and prepare to detect the next cylinder. If the test result is unqualified, call the police, notify the predecessor process, and check the working process. According to the needs of the application, the detection device can be linked with other systems in the factory through the network; the detection data can also be retained for review.

As shown in Figure 5, the optical detection part is responsible for irradiating the laser vertically to the surface of the inner wall, and imaging the optical image onto the sensitive surface of the image acquisition system. It includes a laser that emits laser light, a reflector that refracts laser light, a prism that observes images, a lens that has been focused for imaging, and a housing that mounts and fixes various devices. The optical detection part, in addition to realizing the functions of imaging and transmission, also plays the role of positioning and fixing, which is directly related to the positioning accuracy of the system. The optical detection part should also ensure an appropriate working distance so that the circuit part can work in a normal environment.

The circuit part (Figure 6, Figure 7) is mainly responsible for the digital acquisition and processing of images. It mainly consists of image acquisition, program storage, image and control information processing.

When the laser light irradiates the surface of the inner wall, the position information is modulated to generate the original image information. The position information is integrated into the image information, and then transmitted in the optical system in the form of an image, where the image is transmitted as a carrier of position information. At the receiving end, the received image information is not completely consistent with the original image information, some are loss changes during transmission, and some are interference noise during transmission. After being sampled and quantized by the sensor into a digital image, the position information is demodulated through further image processing.

Claims (6)

1. On-line imaging detection device of drum inner and outer wall machining precision, its characterized in that includes: the device comprises a shell (1), a laser (2), a reflecting mirror (3), a light path conversion mirror (4) and an image receiving and processing part (5); the laser device (2), the reflector (3) and the light path conversion mirror (4) are assembled in the shell (1); laser emitted by the laser (2) is reflected by the reflector (3) and then projected to the surface of the inner wall of the cylinder to be measured to form a diffuse reflection light spot; and the light path conversion mirror (4) captures the diffuse reflection light spots and converges the diffuse reflection light spots to the image receiving and processing part for processing.

2. The on-line imaging detection device for processing accuracy of inner and outer walls of a cylinder according to claim 1, wherein: the light path conversion mirror (4) is a triangular prism; the laser converted by the light path conversion mirror (4) is parallel to the incident light emitted by the laser (2).

3. The on-line imaging detection device for processing accuracy of inner and outer walls of a cylinder according to claim 1 or 2, wherein: the image reception processing section (5) includes: the device comprises an image acquisition processing module, a digital signal processing module, a data storage module and a data transmission and display module; the image acquisition and processing module acquires and processes the diffuse reflection light spot image; the digital signal processing module receives the data from the image acquisition processing module, performs operation processing, and then stores the related result in the data storage module; and the data transmission and display module displays the position information of the inner wall of the cylinder.

4. The on-line imaging detection device for processing accuracy of inner and outer walls of a cylinder according to claim 1 or 2, wherein: and is also provided with a USB interface or a network interface.

5. The on-line imaging detection device for processing accuracy of inner and outer walls of a cylinder according to claim 3, wherein: and is also provided with a USB interface or a network interface.

6. The on-line imaging detection device for processing accuracy of inner and outer walls of a cylinder according to claim 5, wherein: a UART chip is also arranged; and the UART chip and the digital signal processing module realize data exchange.

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