CN104807403A - Driving light measuring rod for size measurement of large workpiece - Google Patents

Abstract

The invention relates to an active light measuring rod for measuring the size of large workpieces, which includes a wireless switch control box, a measuring rod main body, a smoothing plate, a diffusion plate, a measuring head, a cover plate, a power switch, a brightness adjustment knob, and a lamp bead circuit board The wireless switch control box is installed on the control box groove at the front part of the measuring stick main body, the measuring head is connected to the tail of the measuring stick main body through threads, the diffusion plate is installed in the diffusion plate groove of the measuring stick main body, and It is fixed by the cover of the smoothing board, and the smoothing board is fixed on the main body of the measuring stick by screws; the lamp bead circuit board is fixed in the groove of the aluminum substrate of the main body of the measuring stick by screws; the power switch and the brightness adjustment knob Fixed on the cover plate; the cover plate is fixed on the main body of the measuring rod with screws. Compared with the articulated arm type three-coordinate measuring machine and the retroreflective type hand-held measuring head visual measurement system, the present invention has the advantages of large measurement range, strong resistance to ambient light interference, convenient identification of feature points, and the like.

Description

An Active Optical Probe for Dimensional Measurement of Large Workpieces

technical field

The invention relates to the field of optical measurement, in particular to an active optical measuring stick used for dimension measurement of large workpieces.

Background technique

The manufacturing industry is one of the pillar industries for the development of the national economy, and measurement technologies such as spatial positioning and dimension measurement are necessary conditions for the development of the machinery manufacturing industry. With the development of aerospace, shipbuilding, metallurgy, automobile manufacturing, port machinery, and wind power equipment, the trend of heavy-duty and integrated equipment is becoming more and more obvious. In the manufacturing and assembly process of large-scale equipment, how to realize the precision measurement of the geometric dimensions and spatial positions of large-scale workpieces is a key factor to ensure the quality of the entire set of equipment. In the field of large-scale measurement, the existing precision measurement methods and equipment cannot effectively solve practical problems in engineering applications. The bottleneck in the development of large-scale measurement field calls for new measurement technology. In recent years, due to the rapid development of laser, semiconductor, automatic control, computer, precision manufacturing and other technologies, a variety of new space large-scale measurement technologies have emerged, which can be summarized into three categories: articulated arm three-coordinate measuring machine, laser space Tracking measuring instrument, hand-held probe vision measuring system.

The above three instruments can realize the measurement of large-sized parts, but there are certain shortcomings: the measurement space of the articulated arm CMM is restricted by the articulated arm, the measurement distance is quite limited, and it takes up a lot of space, which is inconvenient Portable; although the laser space tracker has the advantages of fast measurement speed, high measurement accuracy and large measurement range, the purchase cost of the laser laser tracker is high, and the core technology is monopolized by foreign companies. It is currently difficult to achieve localization, and there are only a few It is used by large multinational manufacturing enterprises and domestic famous research institutions, and belongs to high-precision measuring equipment. The hand-held probe visual measurement system, namely the stick measurement system, is a measurement device that can meet the general precision requirements for large-scale space measurement. It is more and more popular among domestic small and medium-sized enterprises because of its affordable price and easy use. Attention and use, but now the measuring sticks used in the market are all retro-reflective. Because this kind of measuring stick is reflected light, the loss of light intensity is large during the process, so the brightness presented in the CCD is limited, and feature points are prone to incompleteness and brightness. Insufficient, uneven brightness and other shortcomings, especially in the detection of large parts that require a large change in the working distance, these shortcomings are particularly obvious. In addition, backlight reflection is easy to introduce environmental noise on site, especially in the machining site, there are many features that can cause specular emission, such as specular reflection on the surface of smooth parts, these noises bring great difficulty and uncertainty to the extraction of cooperative mark points. Determinism, which also severely restricts the scope of use of the measuring rod.

Contents of the invention

In view of the above problems, the purpose of the present invention is to provide an active optical measuring rod for measuring the size of large workpieces. The probe can generate an infrared active geometric light source with specific characteristics, uniform brightness, accurate position and shape, its probe can accurately locate the measurement point, and its wireless switch can trigger the camera for image acquisition. Since the active light source is used to generate the characteristic pattern of visual inspection, it has a large viewing angle and measurement range. The detection algorithm of the cooperative mark point of the measuring rod can realize the accurate extraction of the characteristics of the active geometric light source, and then realize the purpose of measuring the feature size .

To achieve the above object, the present invention adopts the following technical solutions:

An active light measuring rod for measuring the size of large workpieces, comprising a wireless switch control box, a measuring rod main body, a smoothing plate, a diffuser plate, a measuring head, a cover plate, a power switch, a brightness adjustment knob, and a lamp bead circuit board; The wireless switch control box is installed on the control box slot at the front of the measuring rod body, the measuring head is connected to the tail of the measuring rod body through threads, the diffusion plate is installed in the diffusion plate groove of the measuring rod body, and is controlled by the The light repairing board cover is fixed on it, and the light repairing board is fixed on the main body of the measuring rod by screws; the lamp bead circuit board is fixed in the aluminum substrate groove of the main body of the measuring rod by screws; the power switch and brightness adjustment knob are fixed on the cover plate; the cover plate is fixed on the main body of the measuring rod with screws.

The wireless switch control box is composed of a control box upper cover, a wireless switch button, a continuous shooting button, a wireless switch circuit board, and a lower cover of the control box. The wireless switch button, the continuous shooting button and the wireless switch circuit board are installed on the Put on the upper cover of the control box and fix it with the lower cover of the control box, and fix the upper cover of the control box and the lower cover of the control box with screws.

The measuring head is composed of a measuring head extension rod and a measuring needle, and the measuring needle is connected with the measuring head extending rod through threads.

The stylus is composed of two parts: a needle shaft and a measuring ball, and the needle shaft and the measuring ball are adhered with a high-strength adhesive; the measuring ball should ensure that its external dimensions will not change due to wear during long-term use , so it is made of materials with high hardness and high wear resistance. The needle bar should ensure that when the contact force between the measuring ball and the surface of the workpiece is 1.25N, the maximum distance between the center of the measuring ball and the original center position does not exceed 0.005 mm, so it should be made of high hardness and high rigidity materials.

The lamp bead circuit board is composed of a heat-dissipating aluminum substrate and lamp beads, and the lamp beads are welded on the heat-dissipating aluminum substrate according to the position of the lamp groove; a circuit for parallel connection of all lamp beads is printed on the heat-dissipating aluminum substrate, and Provide heat dissipation for the lamp beads to ensure the service life of the lamp beads.

The lamp beads described above use lamp beads with a beam spread angle of 80°-135° to ensure uniform lighting within the area of the feature points on the diffuser plate.

The smoothing plate is a thin-walled structure with a thickness of no more than 0.5mm. The seven holes on the smoothing plate are used to ensure the size and mutual position of the cooperation mark points, so the relative position error between the holes should ensure that the comparison rod The accuracy of the measurement is high. For this reason, these holes are processed by slow wire walking. At the same time, in order to ensure the viewing angle of the cooperation mark points, a 60-degree chamfer is chamfered on the outer edge of each round hole. The size of the narrow side of the chamfer consistent with the plate thickness.

The diffusion plate is made of a material with good light diffusion effect, so as to ensure that the brightness of the geometrical light source is uniform enough.

The geometric light source feature of the measuring rod is: a combination of T-shaped seven-point cooperative marking points, three-point horizontal lines, and five-point vertical lines, or a combination of T-shaped multi-point or cross-shaped multi-point. Each cooperation mark point is a circle feature, and it can also be a polygon feature or a combination of circle and polygon features. The cooperation sign point itself is an active light source with a circular feature, and the light source used is infrared light with a wavelength band of 850nm, which is provided by the lamp bead, or it can be monochromatic light of other bands, and is installed in front of the camera by corresponding The band-pass filter of the band is used to filter out the influence of ambient light to ensure that the circle feature can present a pure ellipse or circle image in the camera. The general implementation process of the combination of the T-shaped seven-point cooperative markers is: extraction of the probe cooperative markers→identification of the cooperative markers→ordering of the cooperative markers.

The present invention has the following advantages compared with those measuring methods enumerated above due to taking the above technical scheme:

Since each cooperative mark point is an active geometric light source, compared with the brightness distribution information, the shape feature is not easily affected by the brightness change caused by factors such as measurement distance, and there will be no brightness distribution detection caused by oversaturation of brightness features or too dark brightness The problem of decreased accuracy.

Each active geometric light source is composed of an infrared light source, an optical diffusion device, and a geometric light hole. The information of the cooperation mark points is determined by transforming the traditional light source brightness distribution information into the shape characteristics of the geometric light hole. The geometric light hole is a high-precision workpiece, and its contour information can be obtained through high-precision testing equipment. The optical diffusion device ensures the uniformity of the brightness of the geometric light source and increases the viewing angle. The infrared light source has a narrow-band characteristic, which is quite different from the spectrum of the industrial on-site light source. With the corresponding band-pass filter, it can well eliminate the influence of ambient light and on-site scene light.

The T-shaped distribution of the cooperation mark points provides the direction information and orientation information of the long and short axis (z, y axis) of the plane, which facilitates the identification of the mark points of the measuring stick.

Description of drawings

Fig. 1 is a three-dimensional schematic view of the structure of the measuring rod of the present invention.

Fig. 2 is a schematic diagram of the structure and composition of the measuring rod of the present invention.

Fig. 3 is a schematic diagram of the main structure of the measuring stick of the present invention.

Fig. 4 is a schematic diagram of the structure and composition of the wireless switch control box of the present invention.

Fig. 5 is a schematic diagram of the composition of the measuring head of the present invention.

Fig. 6 is a schematic diagram of the composition of the lamp bead circuit board of the present invention.

Fig. 7 is a schematic diagram of the structure of the probe of the present invention.

Fig. 8 is a schematic diagram of the arrangement of cooperative mark points of the measuring rod (T-shaped seven-point type) of the present invention.

Fig. 9 is a schematic diagram of the detection process of the detection rod cooperative marker point of the present invention.

Fig. 10 is a schematic diagram of the use of the measuring stick of the present invention.

Fig. 11 is a schematic diagram of the imaging effect of the measuring rod and the marking result of the present invention.

Fig. 12 is a schematic diagram of the detail imaging effect of the round characteristic imaging of the rod cooperative mark point of the present invention.

Detailed ways

The following embodiments will further illustrate the present invention in conjunction with the accompanying drawings.

Referring to Fig. 1, Fig. 2 and Fig. 3, an active light measuring stick for measuring the size of large workpieces is characterized in that it includes a wireless switch control box 2, a measuring stick main body 3, a smoothing plate 4, a diffusion plate 5, and a measuring head 6. Cover plate 7, power switch 8, brightness adjustment knob 9, lamp bead circuit board 10; the wireless switch control box 2 is installed on the control box groove 13 at the front part of the measuring rod main body 3, and the measuring head 6 is threaded Connect the tail of the measuring rod main body 3, the diffuser plate 5 is installed in the diffuser plate groove 11 of the measuring rod main body 3, and is fixed on it by the smoothing plate 4, and the smoothing plate 4 is fixed on the measuring rod by screws On the main body 3; the lamp bead circuit board 10 is fixed in the aluminum substrate groove 14 of the measuring stick main body 3 by screws; the power switch 8 and the brightness adjustment knob 9 are fixed on the cover plate 7; the cover plate 7 is fixed with screws Fixed on the probe body 3.

Referring to Fig. 4, described wireless switch control box 2 is made up of control box upper cover 17, wireless switch button 18, continuous shooting button 19, wireless switch circuit board 20, control box lower cover 21, described wireless switch button 18, continuous shooting Button 19 and wireless switch circuit board 20 are installed on the control box loam cake 17 by clearance fit, and fix with control box loam cake 21, and control box loam cake 17 and control box loam cake 21 are fixed with screws.

Referring to FIG. 5 , the probe 6 is composed of a probe extension rod 22 and a probe 23 , and the probe 23 is connected to the probe extension rod 22 through threads.

Referring to FIG. 6, the lamp bead circuit board 10 is composed of a heat dissipation aluminum substrate 24 and a lamp bead 25, and the lamp bead 25 is welded on the heat dissipation aluminum substrate 24 according to the position of the lamp groove 12; A circuit for connecting all the lamp beads 25 in parallel is printed and provides heat dissipation for the lamp beads 25 to ensure the service life of the lamp beads 25 .

Referring to Fig. 7, the stylus 23 is composed of a needle shaft 26 and a measurement ball 27, and the needle shaft 26 and the measurement ball 27 are bonded with a high-strength adhesive; Can cause its external dimension to change because of wearing and tearing, so select the material with high hardness and high wear resistance to make such as ruby, described needle bar 26 should guarantee that when the contact force between measuring ball 27 and workpiece surface is 1.25N, measuring The ball center of the ball 27 deviates from the original center position by a maximum distance of no more than 0.005mm, so it should be made of high hardness and high rigidity materials such as tungsten carbide.

The use process and principle of the present invention are as follows:

Referring to Fig. 8, the geometric light source of the measuring stick 1 is characterized by: a combination of T-shaped seven-point cooperative marking points, three-point horizontal lines, five-point vertical lines, and can also be T-shaped multi-point or cross-shaped multi-point The combination. Each cooperation mark point is a circle feature, and it can also be a polygon feature or a combination of circle and polygon features. The said cooperative sign point itself is an active light source with circular characteristics, and the used light source is infrared light with a wave band of 850nm, which is provided by the lamp bead 25, and can also be monochromatic light of other wave bands. A band-pass filter of a corresponding band is installed to filter out the influence of ambient light to ensure that the circle feature can present a pure ellipse or circle image in the camera 29 .

Referring to Figure 9, the method and steps for identifying the cooperative marker points of the measuring stick are as follows:

(1) Extraction of cooperative identification points on the measuring stick.

After the camera 29 collects the image of the measuring stick, the image is firstly preprocessed, which includes a filtering operation to remove discrete noise points in the image and adaptive binarization processing; then perform morphological processing to obtain a more regular elliptical spot. Secondly, use the canny operator to detect the edge of the image and perform ellipse fitting operation on the extracted edge points, so that the center image coordinates of the target point can be extracted.

(2) Cooperating identification points on the long axis and short axis of the measuring stick.

On the T-shaped feature on the measuring rod 1 proposed by the present invention, the number of cooperative identification points on the long axis is more than that on the short axis. Therefore, according to the obtained cooperation identification point information, two cooperation identification points are randomly selected to obtain a straight line. If the remaining cooperation identification points, the number of cooperation identification points whose distance to the straight line is less than a certain threshold value is greater than a fixed value ( This value can be taken between the number of cooperation identification points on the long axis and the number of cooperation identification points on the short axis), and the cooperation identification points whose distance to the line is less than a certain threshold can be considered as the cooperation identification points on the long axis . On the contrary, a straight line can be obtained by taking two cooperative identification points randomly. If the number of cooperative identification points whose distance to the straight line is less than a certain threshold among the remaining cooperative identification points is less than a fixed value (this value can be taken on the long axis between the number of cooperation identification points on the short axis and the number of cooperation identification points on the short axis), it can be considered that the cooperation identification points whose distance to the line is less than a certain threshold are the cooperation identification points on the short axis.

(3) Sorting of the cooperative identification points on the long axis and short axis of the measuring stick. Referring to Figure 8, it is assumed that the cooperation mark point a located on the vertical foot of the T-shaped feature and the cooperation mark point on the remaining long axis are respectively defined as cooperation mark point b and cooperation mark point a according to the distance from the cooperation mark point a from small to large. Mark point c, cooperation mark point d, cooperation mark point e. On the short axis, the cooperation mark point to the left of the cooperation mark point a is the cooperation mark point f, and the right side is the cooperation mark point g.

First, fit the cooperation mark points on the long axis into a straight line, and obtain the foot point of the T-shaped feature (that is, the cross point of the T-shaped feature) according to the cooperation mark points on the short axis. Secondly, according to the vector direction obtained from the cooperation mark point and the foot point on the short axis, the cross product of the vector direction and the long axis direction is positive, which is the cooperation mark point f, and if the cross product value is negative, it is the cooperation mark point g. Finally, the distances from the feature points on the long axis to the vertical foot points are obtained respectively, from small to large, which are cooperation mark point b, cooperation mark point c, cooperation mark point d, and cooperation mark point e.

Referring to FIG. 10 , it is a schematic diagram of the use of measuring stick 1 to measure the length of a part. As long as the measuring ball 27 of the measuring stick is in contact with the two end faces of the part, and simultaneously press the wireless switch button 18 on it to trigger the camera 29 to take pictures, in the computer 28 The acquired image is processed to extract the position of the probe center respectively, and then the length of the part is calculated.

See Figure 11, which shows the imaging effect of the measuring rod 1 in actual use. The imaging effect of the cooperative mark points in actual use is good: the circle feature is accurate, and the background noise on the scene is effectively suppressed, and it is easy to take pictures The processing work is to obtain the point number of the cooperative mark point on the probe 1. Among them (a) is the frontal imaging effect of measuring rod 1 at half a meter away from camera 29, (b) is the imaging effect of measuring rod 1 after it is rotated 60° relative to camera 29, (c) is 2.5m away from measuring rod 1 to camera 29 imaging effect.

Referring to FIG. 12 , the circular feature imaging detail effect of the cooperative marker point of the measuring rod 1 , the cooperative marker point of the measuring rod 1 can still present a very accurate ellipse when there is a large deflection angle relative to the camera 24 in actual use.

Claims (8)

1. An active light measuring stick for measuring the size of large workpieces, characterized in that it includes a wireless switch control box (2), a measuring stick main body (3), a smoothing plate (4), a diffusion plate (5), and a measuring head (6), cover plate (7), power switch (8), brightness adjustment knob (9), lamp bead circuit board (10); the wireless switch control box (2) is installed on the front part of the main body (3) of the measuring rod On the control box slot (13), the measuring head (6) is screwed to the tail of the probe body (3), and the diffuser plate (5) is installed in the diffuser plate slot (11) of the probe body (3) ), and is fixed by covering it with the smoothing plate (4), the smoothing plate (4) is fixed on the main body (3) of the measuring stick by screws; the lamp bead circuit board (10) is fixed on the measuring stick by screws In the aluminum substrate groove (14) of the rod main body (3); the power switch (8) and the brightness adjustment knob (9) are fixed on the cover plate (7); the cover plate (7) is fixed on the measuring rod with screws On the main body (3). 2. The active light measuring rod for large workpiece size measurement according to claim 1, characterized in that: the wireless switch control box (2) consists of a control box upper cover (17), a wireless switch button (18), The continuous shooting button (19), the wireless switch circuit board (20), and the lower cover of the control box (21), the wireless switch button (18), the continuous shooting button (19) and the wireless switch circuit board (20) through clearance Install it on the control box upper cover (17), and fix it with the control box lower cover (21), and the control box upper cover (17) and the control box lower cover (21) are fixed with screws. 3. The active optical measuring rod for large workpiece size measurement according to claim 1, characterized in that: the measuring head (6) is composed of two parts: the measuring head extension rod (22) and the measuring needle (23), The stylus (23) is threadedly connected to the probe extension rod (22). 4. The active light measuring rod for large workpiece size measurement according to claim 3, characterized in that: the stylus (23) is composed of two parts: a needle shaft (26) and a measuring ball (27), and the The needle bar (26) and the measuring ball (27) are adhered with high-strength adhesive; the measuring ball (27) should ensure that its external dimensions will not change due to wear and tear during long-term use, so it is selected to have high hardness and The needle bar (26) should ensure that when the contact force between the measuring ball (27) and the surface of the workpiece is 1.25N, the center of the measuring ball (27) deviates from the original center position by a maximum distance of More than 0.005mm, so it should be made of high hardness and high rigidity materials. 5. The active light measuring rod for measuring the size of large workpieces according to claim 1, characterized in that: the lamp bead circuit board (10) is composed of a heat-dissipating aluminum substrate (24) and lamp beads (25), and the The lamp beads (25) are welded on the heat dissipation aluminum substrate (24) according to the position of the lamp groove (12); the circuit for parallel connection of all lamp beads (25) is printed on the heat dissipation aluminum substrate (24), and is The lamp bead (25) provides heat dissipation to ensure the service life of the lamp bead (25). 6. The active light measuring rod for measuring the size of large workpieces according to claim 5, characterized in that: said lamp bead (25) selects a lamp bead with a beam spread angle of 80°~135° to ensure Lighting is uniform within the range of the feature point area on the board (5). 7. The active light measuring rod for measuring the size of large workpieces according to claim 1, characterized in that: the smoothing plate (4) is a thin-walled structure with a thickness of no more than 0.5 mm, and the smoothing plate (4) is The seven holes are used to ensure the size and mutual position of the cooperation mark points, so the relative position error between the holes should be higher than the measurement accuracy of the measuring rod. For this reason, the slow wire-feeding method is used to process these holes. At the same time, in order to ensure the viewing angle of the cooperation mark points, a 60-degree chamfer is chamfered on the outer edge of each round hole, and the size of the narrow side of the chamfer is consistent with the thickness of the plate. 8. The active light measuring rod for measuring the size of large workpieces according to claim 1, characterized in that: the diffusion plate (5) is made of a material with good light diffusion effect to ensure the geometric light source characteristics Brightness is uniform enough.