On-line automobile aluminium alloy hub blank deformation measurement method and measurement device

A technology for aluminum alloy wheels and wheel blanks, which is applied in the direction of measuring devices, optical devices, instruments, etc., can solve the problems of inaccurate measurement of wheel rim deformation, few measurement positions and points, and rare deformation measurement reports, etc., to achieve Improve detection accuracy, improve enterprise production efficiency, reduce the effect of measurement procedures and time

Inactive Publication Date: 2013-08-07
BEIJING ORIENT
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AI-Extracted Technical Summary

Problems solved by technology

In terms of wheel hub blank measurement, the application of laser on-line measurement has just emerged. Due to the extremely irregular shape of the blank, there are relatively few reports on its deformation measurement.
The Austrian MNI company has developed the MEAS DIS Serie30...
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Method used

[0051] Therefore, with the length k as the benchmark, the selected point range of the feature point can b...
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Abstract

The invention discloses an on-line automobile aluminium alloy hub blank deformation measurement method and a measurement device which relate to the field of automated measurement. The measurement device comprises a test table, a pneumatic clamping mechanism, an air cylinder lifting mechanism, a hub-rotating mechanism, two laser sensors, a motion control module, an industrial personal computer for storing and processing data, and data processing software. By scanning a hub blank in all directions, the measurement device can simultaneously measure the wheel rim deformation and the center axial deformation of the hub blank, thus achieving the effects of high measurement accuracy, more measurement points, high speed and high reliability, automatically measuring the hub blank on line, and increasing the production efficiency of enterprises. The process of measurement is automatic, measurement can be adapted to harsh environments, and cannot be affected by vibration, smoke or humidity, the total measurement time is 30 seconds, the measurement precision is 0.02mm, and the actual demand on measurement can be satisfied.

Application Domain

Technology Topic

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  • On-line automobile aluminium alloy hub blank deformation measurement method and measurement device
  • On-line automobile aluminium alloy hub blank deformation measurement method and measurement device
  • On-line automobile aluminium alloy hub blank deformation measurement method and measurement device

Examples

  • Experimental program(1)

Example Embodiment

[0026] In order to further understand the content, features, and functions of the present invention, an embodiment of the present invention is introduced below, which is described in detail with the accompanying drawings.
[0027] See Figure 1-6 , The present invention is an on-line deformation measuring device for aluminum alloy hub blanks based on the laser triangulation method and a measuring method thereof. The measuring device includes a cylinder 2, a stepping motor 3, a servo motor 7, and a proximity switch 8 installed on the detection table 1. , Laser fixing device 9, laser 10, ball screw 11, pneumatic clamping mechanism 12, roller table 13, gear 14, guide rod 15 and pallet 16, such as figure 1 As shown, the cylinder 2, the gear 14 and the support plate 16 constitute a cylinder lifting device. The cylinder 2 is arranged at the center of the bottom of the testing platform 1, and the cylinder 2 is connected to the support plate 16 vertically upwards, such as image 3 , The supporting plate 16 is used to install the wheel hub blank 6. A horizontal gear 14 is fixedly connected between the piston of the cylinder 2 and the supporting plate 16. The gear 14 includes two gears, one of which is fixed on the piston of the cylinder 2, and the other is fixed on the output of the stepping motor 3. On the shaft, the piston of the cylinder 2 and the output shaft of the stepping motor 3 are parallel and vertical, and the gear 14 is horizontal. The stepping motor 3 is also fixed on the piston of the cylinder 2, and the piston of the cylinder 2 moves up and down. Adjust the height of the pallet 16. The meshing transmission of the big gear and the small gear realizes the adjustment of the horizontal rotation angle of the wheel hub blank 6 fixed by the pneumatic clamping mechanism 12 on the big gear. The gear 14 can be driven by the stepping motor 3 to mesh and rotate in a horizontal plane, so as to adjust the angle of the wheel hub blank 6 on the support plate 16. A ball screw 11 is arranged above the detection platform 1, and guide rods 15 are also arranged on the upper and lower sides of the ball screw 11, and the ball screw 11 and the guide rod 15 are located in the same vertical plane. The laser 10 is connected to the ball screw 11 through the laser fixing device 9 to ensure the scanning of the laser 10 in the vertical plane. Proximity switches 8 are provided at both ends of the ball screw 11. The ball screw 11 is driven by a servo motor 7 provided on the detection table 1 to rotate and drive, and the ball screw 11 rotates to drive the movement of the laser fixing device 9 to realize the movement scanning of the laser 10.
[0028] The laser 10 realizes interactive communication with the industrial computer 5 through a USB cable, and measurement data is transmitted to the industrial computer 5 through a USB data cable. The industrial computer 5 communicates interactively with the PLC 4 through an RS232 serial port line. The pneumatic clamping device 12 and the cylinder 2 contain solenoid valves. The PLC4 and the solenoid valve are connected by wires. The solenoid valve is located in the middle of the gas circuit. The PLC4 sends different instructions to the solenoid valve to control the opening and closing of the valve at different positions. The clamping and unclamping actions of the pneumatic clamping device 12 and the lifting and lowering actions of the cylinder 2 are controlled. The servo motor 7 is connected with the servo driver, and the PLC 4 sends instructions to the servo driver to realize the action control of the servo motor 7.
[0029] The online measurement of the wheel hub blank 6 using the measuring device specifically includes the following steps:
[0030] The first step is to use the measuring tool to adjust the exciter 10 in advance to install the position on the laser fixing device 9 to ensure that the connection direction of the laser points of the two lasers 10 is perpendicular to the movement direction of the laser 10 along the ball screw 11, adjust and measure The distance between the laser points of the two lasers 10 is such that the distance is smaller than the minimum diameter on the wheel hub blank 6;
[0031] The second step is to turn on the power, turn on the circuit, gas circuit and laser 10, and transport the wheel hub blank 6 to the roller table 13 corresponding to the position of the pallet 16, that is, the wheel hub blank 6 is transported to the inspection table roller table 13 via the roller table 13 or the robot And reach the position of the pallet 16, the detection station 1 sends a signal to the PLC4.
[0032] In the third step, PLC4 controls the cylinder 2 installed on the bottom of the inspection platform 1 to lift the hub support plate 16 and contact the wheel hub blank 6 on the roller table 13; at the same time, PLC4 controls the pneumatic clamping mechanism 12 to clamp the hub blank 6;
[0033] In the fourth step, after the wheel hub blank 6 is lifted to the measuring position, the PLC 4 sends an instruction to the industrial computer 5; the measurement position means that the measuring surface of the wheel hub blank 6 is within the range of the laser 10, ensuring that the laser 10 is on the wheel hub blank 6 Scan.
[0034] In the fifth step, the industrial computer 5 sends instructions to the laser 10, the laser 10 starts to collect data, and the PLC4 controls the servo motor 7 set above the detection platform 1 to drive the ball screw 11 to rotate, so that the laser 10 moves along the ball screw 11 and the guide rod 15 Scan the hub blank 6 at a constant speed from the position of the proximity switch 8 at the right end to the position of the proximity switch 8 at the left end. The industrial computer 5 sends instructions to the laser 10, and the laser 10 stops collecting data and stores the measured data to the industrial computer 5;
[0035] In the sixth step, PLC4 controls the stepping motor 3 to drive the gear 14 connected with the pneumatic clamping mechanism 12 to rotate, so that the pneumatic clamping mechanism 12 rotates precisely 45° counterclockwise. After stabilization, the industrial computer 5 sends instructions to the laser 10. 10 starts to collect data, PLC4 controls the servo motor 7 to drive the ball screw 11 to move, so that the laser 10 scans the hub blank 6 at a constant speed from the left end proximity switch 8 position to the right end proximity switch 8 stop, the industrial computer 5 sends instructions to the laser 10, the laser 10 Stop collecting data, and store the measurement data and transmit it to the industrial computer 5;
[0036] In the seventh step, PLC4 controls the actions of the stepping motor 3 and the gear 14 to make the pneumatic clamping mechanism 12 continue to rotate 45° counterclockwise. After stabilization, repeat the fifth and sixth steps to realize the four different wheel hub blanks 6 Scanning at positions 0°, 45°, 90°, 135°; according to the needs of measurement, two or more measurement positions are generally selected, and the specific positions can be adjusted according to actual needs.
[0037] In the eighth step, the laser 10 transmits the measurement data to the industrial computer 5 through the USB cable, and after processing, the outline of the wheel hub 6 can be obtained, see Image 6. The characteristic points at the rim surface 17 and the hub center 18 are respectively extracted according to the change in the curvature of the contour curve. With 4 scans, a total of 32 feature points can be extracted at the rim surface 17 and the hub center 18, and the rim surface deformation and the center axial deformation can be calculated according to the feature points;
[0038] The ninth step, the calculation is completed, the industrial computer 5 sends instructions to the PLC4, and the PLC4 controls the cylinder 2 to lower the pneumatic clamping device 12, and at the same time, the PLC4 controls the pneumatic clamping device 12 to loosen the wheel hub blank 6;
[0039] In the tenth step, the industrial computer compares the result obtained in the eighth step with the set value, the out-of-tolerance is the unqualified product, and an alarm is issued, and the unqualified product is sorted by the robot.
[0040] In the above-mentioned measurement method, the processing of the measurement data is realized by the data processing software inside the industrial computer 5. The data processing software is based on the principle of non-contact laser triangulation in the process of data processing, using dual lasers to cooperate with Rotate the hub blank 6 to scan the surface of the hub blank 6 in all directions, and calculate the axial deformation of the rim surface 17 and the center plane 18 by extracting the characteristic points of the rim surface 17 and the center plane 18 of the hub blank 6. The specific calculation method is as follows:
[0041] (1) Coordinate calibration.
[0042] When scanning starts at different positions of the wheel hub blank 6, the movement direction of the laser 10 along the ball screw 11 is set as the x-axis direction. Since the two lasers 10 start collecting data and stop collecting data at the same time, the number of sampling points of the two lasers 10 is the same each time. Taking the starting position of the laser 10 as the x-axis zero position, the x-axis coordinates of each point are:
[0043] x=mv/n
[0044] In the formula, m is the number of sampling points at any position of the laser 10 at each scan, v is the linear motion speed of the laser 10 along the ball screw 11, and n is the sampling rate of the laser 10 (the number of points collected per second).
[0045] Set the connecting direction of the light spots of the two lasers 10 as the y-axis direction. Taking the starting position of one laser 10 as the y-axis zero point, the y-axis coordinates of all points on this scan line are 0, and the y-axis coordinates of all points on the other scan line are L (L is the distance between light points).
[0046] Set the laser beam irradiation direction as the z-axis direction, the midpoint of the range of the laser 10 is the z-axis zero point, and the z-axis coordinate value of each point is the actual laser 10 collection height value. From this, the three-dimensional coordinate values ​​of the collected points can be obtained. A separate coordinate system is established for each scan, but according to the rotation angle and geometric relationship of the hub, the coordinates of the points of the four scans can be assigned to the same coordinate system.
[0047] (2) Extraction of feature points on the surface of the wheel hub blank.
[0048] The feature points are extracted based on the change of the surface curvature of the hub. The shape of the wheel hub blank 6 is very irregular, but there are flat or near-plane places at the hub rim surface 17 and the center plane 18, and the contour of the hub blank 6 scanned by the laser 10 appears as a straight line (such as Image 6 Shown). Before the laser 10 scans the wheel hub blank 6, it is out of its range, and the displayed value of the collected point is NULL, which is an invalid value. Processing data can be obtained, the linear length k of the laser 10 scanning the surface of the hub is:
[0049] k=m 1 v/n
[0050] Where m 1 Is the number of effective sampling points of the laser 10 per scan, v is the linear movement speed of the laser 10 along the ball screw 11, and n is the sampling rate of the laser 10 (the number of points collected per second).
[0051] Therefore, taking the length k as the reference, the range of the feature points can be determined near the rim surface and the center plane of the hub, reducing the amount of data processing.
[0052] Since there are plane features at the rim surface of the hub and the center of the hub, determine the plane:
[0053] Near point i, there is the following relationship with the z-axis height values ​​of nearby points (i-n1 and i+n1):
[0054] |z i-n1 -z i |
[0055] |z i+n1 -z i |
[0056] Among them, n1 is the set point number (the difference in the number of sampling points between the characteristic point i and the nearby points), generally 40 to 80; S is the plane threshold, generally 0.1 to 0.15; z i Is the z-axis coordinate of the feature point i.
[0057] It can be considered that the vicinity of point i is a plane, and point i is a characteristic point. According to the coordinate calibration method, the coordinates (x i , Y i ,z i ).
[0058] According to the above algorithm, in the whole measurement process, a total of 32 feature points can be obtained, of which 16 are located on the rim surface, and the rest are located on the center plane of the hub, distributed as Figure 5 Shown.
[0059] (3) Calculation of the flatness of the rough rim surface of the wheel hub.
[0060] The least square method is used to calculate the plane error of the rim surface, which is its deformation. See the document "Analysis of Flatness Error Least Squares" (Zhang Fang, Machinery Manufacturing and Research, 2002, (3): 17-19). According to step (2), 16 feature points are uniformly extracted on the rim surface, and the coordinate value of each point is obtained.
[0061] Fit the ideal plane according to these points as follows:
[0062] Ax+By+Cz+D=0
[0063] A, B, C, D are the coefficients determined according to the coordinate of the characteristic point.
[0064] Using the distance equation from the point to the plane, calculate the distance from each characteristic point on the rim surface to this ideal plane. Then the rim plane deformation and plane error △z 1 That is:
[0065] △z 1 =z max -z min
[0066] z max Is the maximum distance from each characteristic point of the rim surface to the ideal plane, z min Is the minimum distance from each characteristic point on the rim surface to the ideal plane.
[0067] (4) Calculation of axial deformation of the center plane.
[0068] According to the ideal plane determined by the characteristic points on the rim surface,
[0069] Ax+By+Cz+D=0
[0070] A, B, C, D are the coefficients determined according to the characteristic points of the wheel rim surface.
[0071] Using the distance equation from the point to the plane, calculate the distance from the 16 feature points at the center of the blank to the ideal plane of the rim surface, and 16 distance values ​​h can be obtained i (I=1,2,3…16). Choose the maximum h from these 16 values max And minimum h min.
[0072] The maximum axial deformation at the center is:
[0073] h max -h 0
[0074] The minimum axial deformation at the center is:
[0075] h min -h 0
[0076] h 0 It is the theoretical distance value from the center of the hub to the rim surface.
[0077] If the maximum and minimum values ​​of axial deformation at the center are within the tolerance range, the wheel hub blank is qualified; any value is out of tolerance, the wheel blank is unqualified.
[0078] The data processing software described in the present invention is written in VC++ language, used for extracting the surface feature points and coordinates of the wheel hub blank, and calculating the rim surface deformation of the wheel hub blank and the axial deformation of the center plane. In addition, the data processing software also has measurement process display, measurement statistics, settings, measurement history and wheel hub discrimination functions.
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