Cable Force Measurement of Bridge Cables Based on Computer Vision

Aiming at the shortcomings of high cost and difficult sensor layout of traditional bridge cable force measurement, as well as the difficulty of general target tracking algorithms to accurately measure the small vibration of cables under environmental excitation, a cable force measurement method based on phase motion amplification algorithm and diamond research sub-pixel template matching algorithm is proposed.Firstly, the vibration video of the cable is collected by a smartphone, and the phase motion amplification algorithm is processed.Secondly, the cable displacement time-history is extracted by the sub-pixel template matching algorithm of diamond search and surface fitting.Finally, the vibration frequency of the cable is obtained by Fourier transform, and then the cable force is calculated by using the relationship between cable force and frequency.The method is verified by the laboratory cable-stayed bridge model and the outdoor footbridge cable test, and the results show that the errors of the first-order and second-order vibration frequency and acceleration response are within 2.4% and 2.7%,respectively.Compared with the tensile force, the calculation results of the cable force in the laboratory cable model test show that with the increase of tensile force, the influence of bending stiffness decreases, and the deviation between the theoretical calculated value and the actual value gradually decreases, which can become a new method for cable force measurement.