Restraining EMI of Displacement Sensors Based on Wavelet Fuzzy Threshold Denoising

Because of the serious electromagnetic interference environments where the displacement sensors work, the wavelet transform method is used to reduce influences the electromagnetic interference. And in this paper, the wavelet fuzzy threshold method is proposed to de-noising, which can overcome the disadvantages of using the hard threshold method or soft threshold solely. Besides, in order to make the estimation accuracy of uncertainty interference higher, the variance estimation method is used to improve the denoising performances. By simulating and analyzing, the sensor signal with serious noise produced by the electromagnetic interference was reconstructed well by disassembled to 6 levels used the sym8 wavelet function. On the basis of this, the noise was reduced by the wavelet fuzzy threshold method. Compared with soft threshold de-noising and hard threshold de-noising, fuzzy threshold de-noising way can restrain EMI better. Finally, the variance estimation method is proved to be able to identify the type of interference signals.