Study of vibration frequency of bridge structure with the help of Doppler laser vibration meter

In this paper, the vibrational frequency of the bridge construction structure has been studied by both experimental and simulation forms using the laser doppler vibrometer. The calculations are performed using simulation of MATLAB simulink and using of interference set-up to divide the laser beam into two reference and measurement arms. The time and frequency behavior of the received signals is calculated for vibration of the bridge structure by considering all of noises including optical noise, electrical circuit noise and test environment. Also in this paper, studies are performed during the construction of a laser Doppler vibrometer and by an interferometric set-up. The used set-up in this experiment is the same as the homodyne arrangement of the Michelson interferometer. It should be noted that in this arrangement, a differential circuit has been used to reduce noise in the electronic part of the device.Moreover, by properly processing the signals and removing all optical, electrical, and environmental noise, the frequency of the vibrating target has been investigated with high accuracy. The results of this study indicate an acceptable consistency between the results of simulation and experimental studies, which indicates the high accuracy of the device in measurements.