The Study Of The HFFT Specimen Installation And Position System Based On Machine Vision Technology

At present,the test specimen is still mainly installed by hand in the high-frequency fatigue crack expanding test(HFFT),operating complicated and low in accuracy and efficiency.Therefore,basing on machine vision technology,constructing on the virtual instrumentation platform and using the leading method of image processing technology and Fuzzy PID Control technology,this dissertation proposed an installation and position system of the test specimen based on machine vision,through this system achieved the automation of specimen's installation positioning and a type of detection and location methods based on machine vision were analyzed.The main research works of this dissertation were as follows:(1)This dissertation put forward a design scheme on the installation and position system of the test specimen based on machine vision,virtual instrumentation and serial communication according to the previous investigations on the developments of the machine vision,virtual instrumentation and serial port communication technology.(2)Considering the various factors such as parameters matching,productivity,detection accuracy and economy,the hardware's major characteristics of the test system were studied and the hardware of the system was built up by choosing the light source,CCD camera,optical lens and the type of image acquisition card and so on.(3)The fundamental theories and methods of the digital image processing technology were studied.Image acquisition,processing and analysis of the specimen and fixture were done depending on the Lab VIEW IMAQ Vision toolkit implement.System calibration and hole distance measurements were finished.(4)Fuzzy PID control algorithm of the DC servo-motor for workbench movement was designed.The control command program of the motor was compiled,and the location of the motor in high accuracy and fast speed by RS232 serial port communication was achieved.(5)The system was designed by modular,and the excellent reliability,maintainability and expansibility were obtained.The hardware and software of the system were debugged and advanced.Combining with each function required to achieve,the task of specimen installed positioning was accomplished automatically.The data and the images were saved instantly.This subject assembled optics mechanics,electronics and computer science into a whole.The images of the specimen and fixture's holes were collected by the area-array CCD.Center coordinates and radius were identified by image processing.The distance was calculated based on position measurement algorithm.The distance was reduced to zero constantly by Fuzzy PID controlling the movement of the DC servo-motor,and finally the task of test specimen installation positioning was achieved correctly.