Research On Detection Of Tire Out-of-plane Displacement Based On Shear Speckle Interferometry

Tires are an important part of transportation,and their safety testing is particularly important.Using laser speckle non-destructive testing technology can detect surface defects and internal air bubbles of tires.However,most of this technology only detects the location of tire defects,and does not systematically conduct quantitative and qualitative analysis on the hidden dangers of tire defects.Aiming at the above problems,this paper proposes a method of measuring tire out-of-plane displacement by laser shearing speckle interferometry,in order to provide a more accurate analysis method for tire defect detection.The research contents of this thesis mainly include:1.A sine-cosine filtering algorithm based on weighted moving average is proposed.By combining the weighted moving average algorithm with the sine-cosine filtering algorithm,the weighted moving average algorithm can effectively reduce the characteristics of random phase fluctuations caused by noise,and realize the smoothing of the phase jump in the phase data.Compared with the sine-cosine filtering algorithm,this method has a better effect on noise processing in the filtering of the phase image,can better preserves the phase information and reduces errors,and provides more accurate phase information for calculating the out-of-plane displacement.2.The discrete cosine transform unwrapping algorithm based on phase gradient smoothing correction is proposed to provide more accurate phase data for the final measurement of out-of-plane displacement.Using the weighted moving average algorithm has the characteristics of practicability and flexibility when dealing with large fluctuations in data.Before performing the discrete cosine transform unwrapping,the weighted moving average algorithm is used to correct the phase gradient,so that the phase data before unwrapping is closer to actual value.Not only can the noise be eliminated to a certain extent,but more importantly,the possibility of phase error transmission can be reduced.3.The liquid crystal phase shifter is calibrated using the Mach-Zehnder optical system.Obvious interference fringes can be obtained by using the Mach-Zehnder optical path.A phase shifter is placed in one of the interference optical paths to achieve phase shift.The phase shifter is calibrated after obtaining the phase fringe pattern that changes with the voltage.This method is relatively simple in operation and implementation and has high calibration accuracy,which provides a new idea for the calibration of liquid crystal phase shifters.4.This paper designs and builds a laser shearing speckle interferometry system for measuring tire out-of-plane displacement.The speckle interferogram is obtained by actual detection of aluminum discs and tires;the speckle interferogram undergoes phase extraction,phase filtering,and phase unwrapping to finally obtain the out-of-plane displacement data of the deformation of the object to be measured.By analyzing the measurement results of the experiment and analyzing the errors of the proposed system and algorithm,the measurement effect of the tire out-of-plane displacement detection system is optimized.The difference between the actual load and the measured out-of-plane displacement is 0.1-2.5um.The maximum relative error is 3.5%.