基于激光多普勒的索力测量系统设计与研究

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

根据激光多普勒测振工作原理,设计了一种小型低频高精度激光多普勒测振系统并用于桥梁斜拉索索力测量。首先分析外差式声光移频激光多普勒测振系统的频率稳定特性,提出直接数字频率合成驱动串行双移频器构成的外差式激光多普勒测振计,并利用自适应滤波器消除测振系统中环境振动带来的干扰。利用自行研制的低频测振系统开展了低频测振实验与拉索实测。实验表明,基于DDS的移频系统有很高的频率稳定度,测振计的本底噪音分布平坦,且测振系统有很强的抗震能力和高分辨率,可以用于工程现场快速索力测量工作。

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.