introduction
The length and width of the steel plate are related to its quality index. To ensure the quality control of the steel plate production, it is necessary to monitor the bandwidth of the steel plate during the rolling process to facilitate the improvement of the product's width performance index. As a basic automation function of the plate rolling mill An important part, the length measuring instrument plays an important role in the detection of the width of the steel sheet.
1, the principle of length measurement
Steel plate length measurement The width meter measures the length of the steel plate and uses the image processing method of the industrial camera to measure the image. In order to take a clear measurement reference line during the measurement, a linear laser is placed above the steel plate, and the laser emits a laser beam. The length direction of the steel plate is parallel. When the end face of the steel plate is within the camera's field of view, the image of the line-shaped laser beam captured by the industrial camera will be a bright band with an inflection point, as shown in the following figure. The inflection point of the bright band during processing is steel plate. The length of the boundary, through the number of pixels contained between the two boundaries can be calculated length of the steel plate.
The above method is a measurement method in which the steel plate is within the field of view of one camera. The length of the steel plate measured by this solution is large, and the accuracy of measurement with one camera is too low. Therefore, two cameras are respectively installed at the front and rear ends of the steel plate to measure the same. The principle is shown in Fig. 2. The blind area between the field of view and the field of view of the two cameras in Fig. 2 constitutes the length of the entire measurement area covering the steel plate. When the plate enters the field of view of the two cameras, the steel plate can be measured in the field of view of the camera. The length L1, L2, plus the length L0 of the dead zone is the plate length L, ie: L = L0 + L1 + L2. The measuring accuracy of the length measuring instrument is related to the resolution and field of view of the industrial camera when the range of a single camera For 1000mm, using a 5.1-megapixel industrial camera, the measurement accuracy of a single camera is ±0.8mm. The overlay accuracy of two cameras is ±1.6mm. The shooting speed of an industrial camera is 10 to 15 frames per second, so the measurement frequency is 10~15 times/sec.
2, width measurement principle
The length measuring instrument for measuring the length of the steel plate measures the width of the steel plate using the double-barrel photoelectric detector. The double-barrel photoelectric measuring head consists of two groups of transmitting lenses and two groups of receiving lenses. The geometric dimensions are determined by using LED clean light source and CCD imaging method. Measuring probe. Its basic measuring principle is shown in the figure below:
In the figure, two LED emitters are provided inside the emitter lens, and the light emitted by the point light source is converted into parallel light beams through the lens to the two receiver lenses. The parallel light beam is imaged on the photoelectric conversion device CCD chip by receiving the lens in the lens. When the object to be measured passes through the field of view consisting of two beams of parallel light, a virtual shadow appears on the image of the photoelectric conversion element, and its width is L1, L2. After the photoelectric signal processing and calculation of the photoelectric conversion element can be performed. Obtain the dimensions B1, B2, B1 plus B2 corresponding to L1, L2 plus the net spacing C between the two shots to obtain the width dimension of the measured object.
3, equipment composition and structure
The entire equipment length measuring unit, the width measuring unit and the control cabinet, etc., are specifically composed of: 2 sets of camera control box (industrial camera and linear guide slide table are installed in the box), 2 linear lasers, 2 sets of width measuring probes, Mounting brackets, control cabinets, industrial computers, monitors and audible and visual alarms, etc. The composition and overall structure of the equipment are shown in the figure below.
In the figure above, the front and rear camera control boxes and linear lasers are the length measurement units of the equipment. The linear guide slides in the control box, industrial cameras and linear laser brackets are mounted on the slide table. Measurements should be made between the front and rear cameras The distance is equal to the length of the steel plate. When the length specification of the steel plate is changed, the distance of the sliding table can be adjusted to the required size by the stepping motor. The adjustment of the stepping motor is set by the program according to the distance, and the recalibration is not required after the adjustment is completed. Can be measured normally.
The two probes for width measurement are mounted on a mounting bracket, which is fixedly mounted near the probe with the rib side. The probe on the other side is mounted on a linear guide rail. When the width dimension of the steel plate changes, The stepping motor drives the slider to adjust the probe to the desired position. The stepper motor is adjusted according to the distance by the program. After the adjustment is completed, normal measurement can be performed without recalibration.
Width measuring head has edge straightness detection function. The detection method is to use the imaging position of the two ends of the steel plate on the chip to fit a straight line. When the edge of the steel plate is bent, the image position of the edge of other positions will deviate. The straight line. Measuring each sheet, the system will record a maximum deviation distance.
The raw data and images collected by the length measuring unit and the width measuring unit are transmitted to the industrial computer through the communication system for processing and calculation. The measurement results will be directly displayed on the display and the on-site LED display. When the measured data exceeds the set tolerance range. When, the control system will control the sound and light alarm for sound and light alarm.
Conclusion
The use of length measurement and width measurement instrument has brought great convenience to the detection of sheet products. The length measurement and width measurement instrument is an on-line testing equipment. It can display the length measurement value, width measurement value and the standard value of length and width in real time. Tolerance, etc., The maximum arcuate height of the board edge is displayed after each board measurement is completed, and the length and width change fluctuation curve can be fitted, which brings great convenience to the steel plate rolling and inspection.
This article was written by Baoding Lanpeng Measurement & Control Technology Co., Ltd.
