Automatic Measurement of Elongation at Break of Cable Sheath Based on Binocular Vision

In order to solve the problem of accuracy and automation of manual measurement for elongation at break of cable sheath,an automatic measurement based on binocular vision is proposed.Firstly,after the sample tensile video is collected,location method based on information entropy is used on the first frame for the center coordinates of two circle markers,if markers are correctly identified,the center coordinate is used as the marked point,otherwise the point closest to the center of circle in SURF feature points with good ste-reo matching results is selected as the marked point.Secondly,the marked points tracking based on L-K op-tical flow is used in the sampled video of sheath stretching process,the determination of the rough frame position of sheath breaking is based on the calculated three-dimensional coordinates and acceleration,then two sampling intervals are backtracked for frame by frame detection.Finally,the breaking frame is located precisely then elongation at break is calculated.The experimental results in the field of quality inspection of cable sheath show that the measured root mean square error of elongation at break is 7.13%which is lower than that of manual measurement method(21.84%),compared with the true values measured by 240 fps high-speed camera,and the processing speed of the method reaches 107.8 fps.Propose method can obviously improve the detection accuracy,speed and automation in practical application.