To investigate micro-Doppler signatures of precession for a warhead with empennages, the model of precession is built and mathematical formulas of a micro-Doppler induced by different scattering centres are derived. The relationship between the micro-Doppler appearing frequency of empennages and micro-motion frequencies is first acquired, then two important precession features, namely coning frequency and spinning frequency, are extracted based on the micro-Doppler. Simulation results are provided to demonstrate the validity of the proposed method.
An optical imaging based fully automatic stereo vision system for aircraft assembly online
measurement is presented and analyzed. In this system, the relative position of the two cameras can
easily calibrated by imaging an optical reference bar in different locations and orientations throughout
the measurement space according to epipolar constraint and the certified distance of the features on
the reference bar. For measurement, the system takes infrared LEDs which attached at measured
object as imaging targets, and makes use of the measurement results of these feature points space
coordinates to calculate the related positions of the assembly aircraft parts. Furthermore, using
automatic infrared LED light intensity and CCD cameras exposure time improve the calibration and
measurement accuracy. The effectiveness of the proposed system has been test by experiments.
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