The Research On The Camera Automatic Adjustment Technology Of The Fatigue Crack Length On-line Monitoring System

The traditional testing system which acquire fatigue crack image with the fixed-focus camera in the online high-frequency fatigue crack length detection system bring the problem that we can't observe both the whole and the part crack image.Therefore the electrical zoom camera is used in the method proposed in this paper,it satisfy the demand that we can observe both the crack whole and the crack tip at the same time,and it makes the online fatigue d crack detection system to be more perfect.The electrical zoom camera can change the focal length in real time in order to amplifier and reduce images,but on the same time it bring the problem of the image fuzzy by the aside of the focus-plane and the imaging-plane.In order to solve this problem,a camera controller for the fatigue testing system has been designed and developed in this paper.The research history and current developing situation of the Camera control at home and abroad had been studied,the performance of DC motor applied to this system has been analyzed and the mathematical model to selected control scheme has been established,also,the technology of automatic focus that bases on image processing developed by Lab VIEW platform has been carefully studied,and the key focused is put on the research of the choice of the clear figure evaluation function and the design of the optimum algorithms.The system hardware and software based on it had been designed and realized.Finally we test the system by the part and whole.The details of this paper are As follows:1.The function demand of the system is presented through the research history and current developing situation of the Camera control at home and abroad,and the implementation scheme of this system is proposed according to the system needs.2.Two key technology(the motion control technology of DC motor and the technology of automatic focus that bases on image processing developed by LabVIEW)are researched in theory which is the needs of the system solutions,and the motion control scheme and automatic focus scheme are given for this system.3.The hardware of the lower computer is designed and implemented which used ARM7TDMI as the core,and the camera controller has been carried out.4.the software of the PC and lower computer is written by the C language and LabVIEW as the software programming language.5.The software and hardware of the system is debugged and the experimental data and experimental rendering is recorded,the experiment results show that this system has achieved the expected function demand and accuracy request.The three motors applied to the camera movement system can be controlled in the relatively ideal condition,the effect of automatic focus also is very significant.