What Is a Steel Rule Die?

Tape measure is a commonly used measuring tool in daily life, and is one of the essential tools for families. Luban ruler, Feng Shui ruler, and metric meter are also steel tape measure. Steel tape measure is a common tool for construction and decoration.

Steel tape measure can be divided into self-rolling

In the history of scientific and technological inventions in the world, China also invented the world's first tape measure.

Measure the size or distance of longer objects.

Composition of steel tape measure parts

A measuring device includes a measuring mechanism such as a tape measure with a tape, the measuring mechanism has an end hook with a hook, and a magnet such as a magnet for selectively fixing the tape to an object such as a pipe The mechanism, the optional fixing mechanism is connected to the end hook of the measuring mechanism. A measuring device includes: a measuring tool having a tip hook; and a magnetic tool embedded in the tip hook.

(1) Direct reading method

When measuring, the zero scale of the steel tape measure is aligned with the starting point of the measurement, and an appropriate tensile force is applied (the tensile force of the tape is determined by the steel tape measure or the calibrated tensile force on the ruler.

Affect steel

The accuracy of the steel tape measure will directly affect the measurement accuracy, so the steel tape measure must be quality checked during use. Most metrology institutes still use manual operations to complete the measurement of steel tapes. On the long measuring table of steel tapes, the errors of the measured steel tapes and standard steel tapes are compared with a microscope. This method has low degree of automation, digitization, and labor intensity. Therefore, the verification mechanism urgently needs a steel tape error automatic detection system that can meet the inspection accuracy of the steel tape measure and improve the inspection efficiency. Aiming at the requirements of steel tape measurement, an automatic measuring system for steel tape based on CCD image was developed, and image processing software was developed using Visual Basic6. It can realize automatic image acquisition and processing, output report of test results, repeat accuracy less than 12 m, easy operation, A steel tape measure greater than 10m can be tested in sections. ^[4]

Image acquisition system

The structure of the detection system is shown in Figure 1. The image acquisition system consists of

Figure 1 Structure of steel tape measuring system

It consists of a stepping motor, a stepper motor driver, a 10m inspection platform, an industrial camera and a sensor. The control command is input through the software interface in the computer, which is jointly controlled by the computer and the single-chip computer to complete the operation of the inspection vehicle, image acquisition, image recognition processing, and printing of test result reports.

During the inspection, the standard steel tape is fixed on the long inspection table. The zero position of the steel tape is positioned and clamped by the zero adjuster. The other end is loaded with a weight of the quality specified in the verification regulations, and then the tested steel tape is parallel. Lay it in parallel position, fix it on the workbench, add weight to the other end, adjust the zeroing screw to align with the zero position. The software system in the computer enters the detection information and control commands through the computer's serial

Figure 2 System composition

The communication port outputs control commands and related parameters to the microcontroller in the controller. The microcontroller analyzes the received string, extracts the control command, and outputs the pulse signal and direction signal with the given frequency to the stepper motor driver according to the command. The input motor drives the detection trolley to run. After the computer controls the slide table to move to each verification position through a single chip computer, the CCD camera takes computer control to capture the line pattern images of the standard steel tape and the measured steel tape, which are converted into digital images by a high-speed real-time graphic acquisition card , And enter the computer for digital image processing. The software system written in VB is used to perform grayscale processing, binarization processing, edge extraction processing, and straight line search on the image, and compare the coordinate values of the detection rule of the standard steel tape and the measured steel tape to obtain the difference and length. Correspond to the corresponding value of the pixel and then perform the corresponding processing, and the result is output as the original record of the test, and it is automatically filed for the record. For steel tapes larger than 10m, the end-to-end method is used for verification.

Control system design

The control system is mainly based on a single-chip microcomputer.

Figure 3 Control circuit

Serial communication controls the operation of the actuator. The industrial camera is installed on the detection trolley. The detection trolley is driven by a stepper motor. The single chip microcomputer controls the movement distance, direction and speed of the stepper motor according to the control command sent by the host computer. The movement of the entire system is controlled by the PC through serial communication between the microcontroller and the PC, as shown in Figure 2.

Figure 3 shows the serial communication and stepper motor control circuit based on the STC89C52 microcontroller. Serial communication is used between the PC and the single-chip computer. Because the serial logic of the serial port of the PC is RS-232C level, and the serial logic of the serial port of STC89C52RC is TTL level, the two cannot be directly connected, so level conversion is required. In the system, MAX232 was selected as the level conversion device. The serial communication interface circuit between STC89C52RC single chip computer and PC is shown in Figure 3. The RS-232C serial signal converted by MAX232 is connected to the DB9 socket and connected to an external PC, and an RS-232C communication interface can be established. The three pins P2.0, P2.1 and P2.2 of the P2 port of the single-chip microcomputer are used to output pulse, steering and enable signals, respectively, and send them to the stepper motor driver.

Image processing technology and system

The image acquisition system transmits the collected whole-meter images of the steel tape measure to the upper computer, and the pictures are processed by the software in the upper computer. Due to the large number of steel tape models, different colors, and large differences in line structure, The problem that needs to be solved in image processing is: the correct method is used to detect the center position of the meter line of the standard and measured steel tape, so that the measurement accuracy of the system is guaranteed.

(1) Image graying processing

The acquired images cannot be directly identified by a recognition program. First, grayscale preprocessing is required. A grayscale image is a special color image with the same R, G, and B components. The variation range of one pixel is 255. Therefore, in digital image processing, in order to reduce the calculation amount of subsequent images, Generally, the images of various formats are first converted into grayscale images. The description of grayscale images, like color images, still reflects the distribution and characteristics of the overall and local chroma and brightness levels of the entire image. The gray-scale processing of the image can be realized by two methods.

(2) Image partition type binary processing

The binarization process of the image is to set the gray level of the points on the image to 0 or 255, that is,

Figure 4 Binarized image by partition method

The entire image is rendered in noticeable black and white. That is, a grayscale image of 256 brightness levels is selected through an appropriate threshold to obtain a binary image that can still reflect the overall and local characteristics of the image. In digital image processing, binary images occupy a very important position. Especially in practical image processing, there are many systems constructed by binary image processing. To perform binary image processing and analysis, first of all, Binarize a grayscale image to obtain a binary image. This is helpful for further processing of the image. The collective nature of the image is only related to the position of the point with a pixel value of 0 or 255. It does not involve multi-level pixels. Value, making processing simple, and the amount of data processing and compression is small. The scale and background color of the measured steel tape are various in the study. The color of the standard steel tape is fixed. This requires selecting different thresholds for the standard tape area and the measured tape area included in the same image. Binarization. The image after partitioned binarization is shown in Figure 4. ^[5]