To overcome the accuracy limitation due to the machining error of standard parts in measurement system, a threedimensional
coordinate measurement method with subwavelength-aperture-fiber point diffraction interferometer (PDI) is
proposed, in which the high-precision measurement standard is obtained from the ideal point-diffracted spherical
wavefront instead of standard components. On the basis of the phase distribution demodulated from point-diffraction
interference field, high-precision three-dimensional coordinate measurement is realized with numerical iteration
optimization algorithm. The subwavelength-aperture fiber is used as point-diffraction source to get precise and highenergy
spherical wavefront within high aperture angle range, by which the conflict between diffraction wave angle and
energy in traditional PDI can be avoided. Besides, a double-iterative method based on Levenbery-Marquardt algorithm is
proposed to realize precise reconstruct three-dimensional coordinate. The analysis shows that the proposed method can
reach the measurement precision better than microns within a 200×200×300 (in unit of mm) working volume. This
measurement method does not rely on the initial iteration value in numerical coordinate reconstruction, and also has high
measurement precision, large measuring range, fast processing speed and preferable anti-noise ability. It is of great
practicality for measurement of three-dimensional coordinate and calibration of measurement system.
A weak fault feature extraction method of rolling bearing based on scale-transformation stochastic resonance (STSR) is proposed. Combined with ensemble empirical mode decomposition (EEMD), the vibration signal with noise is adaptively decomposed for antialiasing by EEMD method to get intrinsic mode functions (IMFs) of different frequency bands, then the IMFs are inputted into scale-transformation mono-stable system. The low frequency fault features are extracted by using a frequency scale R to change the step length of numerical calculation and the adjustment of mono-stable system parameters, and finally slice bi-spectrum is adopted to perform the postprocessing of the output of the mono-stable system. Simulation analysis is performed to validate the characteristics of STSR, and analysis of measured signal of the rolling bearing with strong background noise shows that the approach can extract the weak fault features of rolling bearing successfully.