Improved adaptive filter and its application in acoustic emission signals

In order to de-noise and filter the acoustic emission(AE) signal, the adaptive filtering technology is applied to AE signal processing in view of the special attenuation characteristics of burst AE signal. According to the contradiction between the convergence speed and steady-state error of the traditional least mean square(LMS) adaptive filter, an improved LMS adaptive filtering algorithm with variable iteration step is proposed on the basis of the existing algorithms. Based on the Sigmoid function, an expression with three parameters is constructed by function translation and symmetric transformation.As for the error mutation, e(k) and e(k-1) are combined to control the change of the iteration step. The selection and adjustment process of each parameter is described in detail, and the MSE is used to evaluate the performance. The simulation results show that the proposed algorithm significantly increases the convergence speed, reduces the steady-state error, and improves the performance of the adaptive filter. The improved algorithm is applied to the AE signal processing, and the experimental signal is demodulated by an empirical mode decomposition(EMD) envelope to obtain the upper and lower envelopes. Then, the expected function related to the AE signal is established. Finally, the improved algorithm is substituted into the adaptive filter to filter the AE signal. A good result is achieved, which proves the feasibility of adaptive filtering technology in AE signal processing.

微型非本征光纤法布里-珀罗压力传感器

设计并研制了一种新的微型非本征光纤法布里-珀罗（F-P）压力传感器。传感器采用普通的商用单模光纤和多模光纤制作。全石英结构,能长期使用,且稳定性好。传感器制作过程仅通过切割光纤、腐蚀光纤和光纤熔接实现,基于F-P多光束干涉原理测量压力。分析了F-P腔的直径、膜厚与灵敏度的关系,确定了传感器的膜厚和腔深等参量,设计了传感器的加工步骤,讨论了氢氟酸腐蚀多模光纤与熔接光纤的关键技术。用单峰谱峰波长法解调出传感器的腔长。建立了实验解调系统,实验结果表明,在0~0.1 MPa范围内,传感器线性好。