基于雷达振动测试技术的时变索力识别方法研究

Time-varying cable force identification method based on radar vibration measurement technique

根据振动频率法索力测试原理,提出了基于连续复小波变换的分时段等值线法进行时变索力识别。将拉索的振动信号划分为多个较小的分析时段,对每个分析时段信号进行连续复Morlet小波变换得到小波系数,采用改进后的小波阈值去噪函数对小波系数进行降噪处理。通过等值线法在等幅值面上提取小波脊带,利用最邻近法对等值线进行拟合插值。然后把插值在频域进行均值化处理,识别出拉索的瞬时频率,进而计算出时变索力。以微波雷达为测试手段,设计了时变索力识别试验,试验结果表明:该方法能够提取到振动信号连续的瞬时频率,无论是索力呈线性变化还是正弦变化,均能准确的识别出索力变化规律,索力识别结果和实际索力误差最大仅为3.8%,且在信噪比较低的情况下仍表现出了较好的适用性。实桥应用结果表明,雷达测试手段结合时变索力识别方法,可以便捷、有效的获取拉索的索力时程。

Here,according to the principle of vibration frequency method for cable force measurement,a time-phased contour method based on continuous complex wavelet transform was proposed to identify time-varying cable force.A vibration signal of cable was divided into several smaller analysis time intervals,wavelet coefficients were obtained by performing continuous complex Morlet wavelet transform on each analysis time-interval signal,and wavelet coefficients were de-noised with the improved wavelet threshold de-noising function.Wavelet ridge band was extracted on equal amplitude value surface with the contour method,and the nearest neighbor method was used to fit and interpolate equal value curve.Then,interpolation was averaged in frequency domain to identify instantaneous frequency of cable,and further calculate time-varying cable force.Time-varying cable force identification tests were designed by taking microwave radar as testing means.The test results showed that the proposed method can extract continuous instantaneous frequency of vibration signal,and accurately identify cable force varying laws whether cable force changes linearly or sinusoidally;the maximum error between cable force identification results and actual cable force is only 3.8%,and it has better applicability under the condition of lower signal-to-noise ratio.The actual bridge application results showed that radar testing means combining the time-varying cable force identification method proposed here can easily and effectively obtain cable force time-histories.