Cable force measurement system design and experiment based on heterodyne laser Doppler vibrometer

Abstract

Cable force of bridge cable is an important standard to measure the safety of bridge. According to the working principle of laser Doppler vibration measurement, a small and high-precision laser Doppler vibration measurement system is designed and applied to cable tension measurement. Firstly, the frequency stability characteristics of the heterodyne acousto-optic frequency shifter laser Doppler vibration system are analysed, and the heterodyne laser Doppler vibrometer which is composed of the direct digital frequency synthesizer and the serial dual frequency shifter is then proposed, and the adaptive filter is used to eliminate the disturbance caused by the environmental vibration in this vibration measurement system. The low frequency vibration measurement experiments and real cable force measurement experiments show that the frequency shift system based on DDS has high frequency stability. The background noise of the vibration meter shows a flat distribution in the low frequency range, and the vibration measurement system itself has very strong seismic ability. It provides an effective method for bridge cable force monitoring.

Keywords

• heterodyne laser doppler
• acousto-optic frequency shifter
• vibration method
• cable force
• low frequency