A novel two-dimensional small angle probe is introduced, which is based on principle of auto-collimation and utilizes
quadrant Si-photoelectric detector (QPD) as detection device. AC modulation, AC magnification and absolute value
demodulation are incorporated to restrain the DC excursion caused by background light and noise etc and to improve the
sensitivity and stability of angle detection. To ensure that while the laser is shining, the current signal (converted into
voltage signal) of QPD also is linear to the AC modulation voltage, this paper adopted AC modulation signal (5400Hz)
with a DC offset. AC magnification circuit with reasonable parameters is designed to inhibit DC drift and the impact of
industrial frequency noise and to ensure good amplification to signal frequency at the same time. A piezoelectric-driven
micro-angle generator is designed to demarcate the angle. The calibration data are input to single chip, and the
measurement of angles can be shown in SMC1602A.
The vibration signal of a rotor bearing system is usually nonlinear and non-stationary. Fourier transform is hard to
analyze these signals. A new method based upon empirical mode decomposition (EMD) and Hilbert spectrum is
proposed for fault diagnosis of roller bearings. We get vibration signals from 6205-type ball bearings with inner-race
faults and with outer-race faults, then analyzing its local Hilbert spectrum and local Hilbert marginal spectrum.
Comparing the results with theory value, we can diagnose the fault of rotary machinery fault. In this study, we find that
local Hilbert spectrum and local Hilbert marginal spectrum are very useful. Hilbert Transformation is introduced to
confirm the HHT method is fit to process nonlinear and non-stationary signals.