Design Of A Laser Automatic Tracking Material Deformation Test System

The strain performance index of the material is a very important property in thefield of construction and manufacturing. As a crucial instrument used in material test,extensometer has been got lots of attention. In this thesis, the extensometer’s historyand development in domestic and overseas are discussed generally. For meeting thepractical measuring range and high precision of the material deformation test resultsrequirements, a novel laser automatic tracking materials test system with a classstructure LD light as the mark has been designed.The work principle of the test system is described, and the mechanicalcomposition and the structure of the optical path of the system are analyzed in thisthesis. Then the parameter range and the relationship between the constituent partshave been gotten. Hardware circuit and software program of the system has beendesigned. The motor driver has been designed. The relationship between the lasertracking speed and the motor turn speed has been analyzed. Using the data of picturethat sampled by the CCD camera, image processing method which including filtering,edge detection and monitoring area selection has been designed. After getting theresults of pretreatment, using the laser mark as the identification, image processingalgorithm has been designed.Finally, for research and development about the system, the experimentalapparatus is constructed. In order to verify the method proposed in this thesis and totest property of the constructed system, some experiments are done as follows:(1) Inthe structured light comparative experiment, different structure LD light has beencompared and the type of the light which is suitable for the system has been selected.(2) Laser marker stability experiment shows that the laser vertical mark line is about25pixels width by the laser marker detection algorithm to judge.(3) In the sameconditions that the motor turning step angle is0.014°, the experiment results of scanning precision compared with step-motor and servo-motor show that precision isabout200um under the step-motor and100um under the servo-motor. And theservo-motor is more stability.(4) When specimen’s motion speed is1mm/s, theresults of laser tracking experiment show that tracking error is less than200um. Theabove experiments verify the feasibility of the designed system in this thesis.