The Whole Process Of Structural Deformation Measurement Based On Stereovision

With the development of civil engineering,the traditional contact measurementhave gradually exposed some disadvantages such as low efficiency and limitedmeasurement range in structural deformation detection. In order to overcome theselimitations and meet the requirements of whole process deformation mesurement,researches on the whole process of structural deformation measurement based onstereovision have been carried out. In this method, three-step calibration algorithmbased on the length of diagonal has been studied, algorithm of whole process ofdeformation measurement based on stereovision has also been studied. On the basisof the above algorithm, a software of the whole process of structural deformationmeasurement based on stereo vision has been compiled. Then, correspondingexperiments have been done.The main content are introduced as below:Firstly, improve the traditional two-step calibration method and proposealgorithm of stereovis ion calibration based on the diagonal length. In paper, thesecond step optimization process uses LM algorithm to improve the efficiency. Onthe basis, optimize cameras' inner and outer parameters using LM algorithmagain.An automatic calibration software is compiled. Then commercial calibrationboard diagonal length reconstruction experiment using two step calibration methodhas been taken, length reconstruction compare experiments using commercialcalibration board and self-made calibration board have been done. The experimentresults show that calibration algorithm in paper is better than the two step method.Secondly, the structual deformation measurement algorithm based onstereovision is proposed. In the method, digital image correlation method for stereoand sequence matching is used, chooses ZNCC as correlation function and usesurface fitting method in sub-pixe l search. To reduce the matching time, blockingmatching method has been proposed. In large deformation condition, update thereference image to make sure the success of matching. Also, build three-orderLagrange shape function and use moving average method to finishdisplacement-field calculation. In the end, introduce Green strain tensor to calculatestrain-fie ld. Based on these algorithm, use MATLAB compile a software for thewhole process of structural deformation measurement based on stereo vision.Thirdly, finish304stainless steel specimen tensile test and the three layerframework model for vibration monitoring test. Compare stereovision method withgauge extensometer in displacement measurement and strain gauge extensometer instrain measurement to verify the reliability. On the basis, out of plane displacement, displacement field, strain field are given to verify the practibility. Comparestereovision method with displacement gauge data of a three-layer frame modelunder earthquake, to verify the reliability. Then, measure the displacement timehistory when displacement gauge is broken or frame model is collapsed to verify thealgorithm in paper can be used in whole process of deformation measurement.