1 Introduction
In the field of industrial flaw detection, due to various problems in the welding process, the welds contain defects such as pores and cracks, which affect the quality of the product, so the detection of defects in the welding image is very important. Influenced by the technical quality and experience of the filmmakers of traditional X-ray weld image inspection, the detection of weld defects gradually changed from manual evaluation to computer intelligent recognition. The on-line detection and analysis of the X-ray real-time detection system can effectively overcome the misjudgment caused by the manual evaluation, so that the on-line inspection of the weld film defect is objective, standardized and standardized. It is a high-tech project that was born by combining various disciplines such as computer, automatic control, mechanical transmission, non-destructive testing, etc. Its successful development will make a "quality" leap in the non-destructive testing technology of China's oil and gas pipeline welds. , bringing a huge impact to the traditional process of weld inspection. The portable weld film digital detector is because of its portability can bring great convenience to customers, so it has greater development prospects.
The design and development of the portable weld film digital detector needs to complete the following aspects. According to the function, the system can be divided into the following four parts:
(1) Mechanical part: The mechanical part includes a film transfer mechanism and an automatic control part. The transfer mechanism drives the weld film to move in the horizontal direction. This part consists of a wear-free rail, a rubber drive wheel, a synchronous drive belt and a stepper motor.
(2) System illumination: The cold field of the energy-saving electronic ballast is used to illuminate the target field of view.
(3) Image acquisition part: This part uses a high speed industrial camera to acquire images. This ensures image quality and scan speed compatibility.
(4) Pattern recognition part: The image acquired by the camera is preprocessed, image segmented and pattern recognized by the computer, and the weld defects are extracted for classification.
This paper mainly designs the hardware structure of the portable digital weld seam film detector. For the design of the mechanical part, the transfer mechanism must first be designed to meet the portable requirements. Then, the single-chip microcomputer is used to realize the control of the stepping motor to realize the movement of the transmitting mechanism. Design the circuit control schematic and write the microcontroller control program.
2. Overall design
According to the requirements of non-destructive testing of weld seams in oil and gas pipelines, the system structure design is shown in Figure 1.
The portable digital weld seam film detector is mainly composed of two parts: a notebook computer and a collection system. The main components of the acquisition system are: line scan camera, film transfer mechanism, lighting system, stepper motor control circuit board, stepper motor driver and stepper motor.
The system first completes the digital input of the ray film, and then performs graphic image processing and analysis. The working principle is as follows: under the cooperation of the cold light source illumination system, the heat dissipation system and the power supply system, the upper computer and the lower computer establish various information data communication, and the computer issues a film walking command and a walking direction command to the serial interface, and the single chip receives the processing through the receiving process. Related commands send CP signal and DIR signal to the stepper motor driver in the mechanical servo drive system. The driver subdivides the CP signal and recognizes the DIR signal to drive the three-phase hybrid stepper motor. The stepper motor drives the film through the synchronous belt. The mechanism drives the film to run smoothly in a certain direction; when the film passes directly under the industrial camera, the upper computer software precisely controls the electronic shutter action of the camera, and in combination with the illumination system, the camera accurately collects the film image frame to the upper computer by line scanning; The upper computer then processes the collected image data for division of labor, one part is sent to the computer for auxiliary processing, and the other part is sent to the graphic image processing board for processing; the processed large amount of image data is dumped to the mass storage system, and the processing is completed. The entire workflow.
The volume of the acquisition system housing is 200mm & TImes; 200mm & TImes; 400mm, the weight does not exceed 10kg. The main layout is shown in Figure 2:
3. Transmitting agency design
Since the width of the industrial ray film is not single fixed, in order to improve work efficiency and work quality, and to ensure the accuracy of detecting the film, it is necessary to conceive a continuously adjustable test seam film system. In this paper, we can accurately position the industrial radiographic film of different widths (70mm-120mm) by adjusting the width of the side plates at both ends of the transfer mechanism to ensure the centering of the camera. The design of the filming mechanism is shown in Figure 3:
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