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Discussion and analysis: the use of video segmentation skills for bearing coaxiality detection
Source: Bearing network time: 2017-12-25
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Graphite bearing inspection principle <br> The graphite bearing is placed on the inspection workbench. The artificial bearing centering device is used to position the graphite bearing in the correct orientation. The backlight transmission illumination is selected to ensure that the middle of the graphite bearing and the CCD optical axis are completely coincident. The picture is clear. The picture of the graphite bearing is received by the camera objective lens and the CCD, and the video picture signal is sent to the video superimposer, which appears on the display. The CCD video picture is superimposed on the three concentric rings by the video superimposer, three The middle of the concentric ring is synchronously adjustable; the inner circle is used as the reference circle, and the inner circle of the graphite bearing is aligned during the detection; the diameter of the two outer diameters corresponds to the coaxiality of the graphite bearing and is synchronously adjustable to ensure the standard civil service. Change. When testing, only the outer margin of the graphite bearing falls between the two outer circles, and it is concluded that the coaxiality of the graphite bearing is qualified.
The primary goal and function <br> The primary skill target for graphite bearing inspection is the graphics resolution and detection resolution. The target is 512 × 512 pixels and 0. 03mm. The primary function is to actively determine the coaxiality of the circle in the table (manual Feeding, semi-active positioning).
Accuracy analysis <br> Here, the camera's horizontal resolution is Sx, the straight direction resolution is Sy, the graphics resolution is 512 × 512 pixels, and the CCD camera's field of view size is 7.95mm × 6.04mm, then:
Sx=7. 95/512=15. 5mm,
Sy=6.04/512=11. 8mm.
Let the eye alignment error be d1. The way to align the graphite bearing is to use the inner circle of the concentric ring as the appropriate circle to aim the inner circle of the graphite ring. The difference between the two outer circles is the scale of the public service, the graphite ring The outer circle falls within two rings, the resolution error is one pixel, and the Sx is larger.
The concentric circle adjusts the error, and adjusts the error of the concentric circle and the inner circle registration of the graphite bearing to one pixel.
Because the error of the disturbance is one pixel d3=±15. 5mm. Because the above are all random errors, according to the random error induction criteria are:
The video overlayer completed by the single-chip microcomputer <br> According to the above data analysis, we can know that in theory, only the random error is more than ±26. 8mm, we can conclude that the coaxiality of the circle is qualified. Here, the system setting. The video overlay is this The key to the system, the video picture signal is input through the CCD, and the system is PAL. The video graphics signal is generated by the video adder, and its scanning method and the picture signal are synchronized. The system requires three concentric ring patterns, which pass through. Button conditioning, freely move on the CCD drawing picture displayed by the display, and the radius is actively expanded and reduced. This system selects AT89C51 and address rewriting circuit to design video graphics drawing adder.
Hardware circuit <br> Hardware circuit block diagram shown in Figure 1. AT89C51 single-chip system is the primary function is to write graphics data to RAM, in the meantime, WR control two options one address strobe, single-chip 15-bit address bus actively rewrite RAM address bus, WR control The line manipulates the read and write status of the RAM and the buffer. The graphic data can be written to the RAM by the data bus of the RAM through the buffer. When the graphic data is read from the RAM, the WR controls the 15-bit address bus of the strobe address rewriting circuit, together with the RAM. The address is actively refreshed, the graphic data is read out, the serial data is outputted through parallel and serial conversion, and the analog switch IC4053 is manipulated. When the control level is high level, the adjustable grayscale level of the analog output of the switch output is simulated, and the control level is low. At the level, the analog switch outputs a video picture signal, thereby completing the superposition of the graphic signal and the video picture signal.
Figure 1 Hardware block diagram Address rewriting circuit's mission is to actively rewrite the RAM address synchronously with the video signal. It consists of synchronous separation, pixel vibrator, eight-way circuit, byte counter, line counter, and two-select switch. Synchronization is used in The CCD video picture signal is separated from the line sync, field sync pulse and odd and even field pulse; the pixel vibrator is controlled by the line sync pulse to perform the forward path vibration and the line back range stop vibration. The vibrator period is the picture point clock pulse width, and its output It is the picture point pulse; the input of the eight-way circuit is the picture point pulse, the output is the byte clock; the byte counter counts the byte, the lower six bits correspond to the A0~A5 bits of the RAM address bus. The byte counter counts one pulse per time. The RAM is rewritten once. The line sync signal is used as the clear signal of the byte counter. When the 64-byte pulse is counted, the line sync signal is cleared, and the byte pulse of the next line is counted from the beginning. Synchronization signal counting, the line counter counts up to 512 lines, is cleared by the field sync signal, and counts the line sync pulse from the head to the next field. The eight-bit output of the line counter corresponds to the A7~A14 bits of the RAM address bus. Similarly, the counter counts one pulse per pulse, and the RAM address is rewritten. For the interlaced CCD, one frame of picture is divided into an odd field and an even field. If the graphic data is stored line by line in the RAM, the byte counter and the line counter are directly used. The output is to rewrite the RAM, then the wrong graphics data will be obtained. If you want to superimpose a circle, the screen will appear up and down two ellipse. Connect the odd and even field pulse signal to the A6 of the RAM, you can handle the interlaced and progressive write between the graphics Opposition.
The output of the second selection switch is controlled by the single chip microcomputer. When writing the graphic data, the RAM address is actively rewritten by the address bus of the single chip, and the RAM address is actively rewritten by the high speed address bus when the graphic data is read.
Software design <br> The software design flow block diagram is shown as in Fig. 2. The program firstly performs the keyboard initialization graphic storage RAM clearing, the second selection switch switches to the single-chip microcomputer, and the circle subroutine is called according to the center of the circle and the radius, and the concentric coordinates are calculated. Write to the display RAM. Then switch the switch to the address rewriting circuit. After the initial graphics are obtained on the display, the system is waiting. The button selects the abort method to respond, distinguishes the key number, and analyzes the middle orientation of the graphic or the concentric circle size change. , to modify the content of the display RAM, so that the apparent orientation and radius of the image change.
Figure 2 Software block diagram Using this hardware circuit, according to the computer graphics programming software, you can complete the video overlay of lines, cross lines, ellipse and other graphics, you can also complete the superposition of Chinese characters or numbers.
Debugging and conclusion <br> After the CCD video signal is synchronized, the pixel vibrator is manipulated through a delay circuit, so that the address orientation of the rewriting circuit will change on the screen. The graphic data stored in the RAM is not available. Change, this is equivalent to the corresponding coordinate (0,0) on the screen is changed according to the conditioning of the delay circuit. In the case that the data in the SRAM is unchanged, the address rewriting circuit rewrites the RAM according to the new coordinate superimposed graph. Three concentric circles move synchronously on the screen. The system avoids the simultaneous movement of three concentric circles through software, which greatly reduces the amount of software debugging.
The video input requirement of character superposition is above 2. 5V, and the voltage of the CCD video signal in the system is about 1.0V. Therefore, it is necessary to pull up the voltage of the CCD video signal. Here, the voltage of the triode is expanded to pull the video up to 2V. To ensure the normal operation of character superposition. However, if the video output signal is not processed, it will appear on the display directly, and the screen will be too bright. Therefore, after the character adder is out, the DC voltage of the pull-up should be removed. Filtering and triode follow-up to ensure that the video signal is not distorted.
Because the dot pitch between the pixels in the horizontal direction of the renderer is 4:3 in the straight direction, in the circular algorithm of the graphics software, the result will be an ellipse. Thus, in the algorithm of the circle, the coordinate system The circle in the circle is reduced by 1/4 in the horizontal direction, and then stored in the RAM by the transformation of the screen coordinates and the RAM, and then a circle is obtained.
The test indicates that the system can quickly complete the quality inspection of graphite bearings, its accuracy can meet the demand, and it is stable and reliable. Together, it also greatly reduces the labor intensity of workers and is used by electric energy meter companies.
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