利用改进阈值的平移不变量小波处理FBG传感信号

Treatment of FBG sensing signal by translation invariant wavelet with an improved threshold

噪声是影响光纤布拉格光栅(FBG)传感系统精确解调中心波长的一种重要因素。小波变换因具有良好的时频特性和多分辨率特性而去噪性能较好。本文通过分析小波传统软、硬阈值去噪方法,发现它们存在影响系统的测量精度缺陷,并且其函数表达式有难以确定的可调因子。提出一种不含调节因子的改进阈值函数并将这种改进阈值与平移不变量(TI)小波去噪法相结合处理FBG传感信号噪声,以提高传统小波去噪法的去噪效果。对FBG模拟信号与实验信号去噪,结果表明,采用基于改进阈值的TI小波能处理不同FBG含噪(从5dB到40dB)信号,且获得最好的信噪比(SNR)和均方根误差(RMSE)性能。与传统软阈值去噪法相比,信噪比平均提高3dB,与参考的改进阈值去噪法相比,信噪比平均提升2dB,满足提高FBG传感系统测量精度的要求。

Noise is one key factor to affect the precision of fiber Bragg grating （FBG） sensor system for demodulating the central wavelength. The wavelet transform can get good de-noising performance due to its good characteristics of time-frequency and the multi-resolution. By analyzing the features of typical soft and hard threshold methods applied for wavelet de-noising, the drawback is to affect the system measurement precision. Moreover, the soft and hard threshold methods need to optimize the threshold function＇s adjustable factor which is difficult to be determined. An improved threshold function without adjustable factor is put forward for wavelet transform in this paper. Integrating the function with the translational invariant （TI） wavelet de-noising method,an application of de-noising the FBG sensor sig- nal is studied to overcome the pseudo-Gibbs phenomena. The simulation and experimental results show that the translational invariant wavelet with improved threshold function can deal with FBG sensor signal with different signal-to-noise ratios （SNR from 5 dB to 40 dB） ,and can get the best SNR and root of mean square error （RMSE） simultaneously. Compared with the traditional soft threshold method,its av- erage SNR increases by 3 dB, while compared with the reference improved threshold method,its average SNR improves by 2 dB. So, the system can meet the requirement of improving FBG sensor detection pre cision.