A Time Synchronization Method Between FBG Deformation Measurement System and Airborne DPOS Based on Waveform Matching

Abstract

The airborne Distributed Position and Orientation System (DPOS) is an important means for multi-point motion measurement required for earth observation with multi-task sensing loads. The sub-nodes in DPOS rely on the main node to perform transfer alignment for them to get high-precision motion data, which requires accurate deformation data and the relative motion relationship between different nodes. Fiber Bragg Grating (FBG) is one of the main means of deformation measurement at present. However, the time synchronization error between FBG and DPOS directly restricts the accuracy of transfer alignment. For this, a high-precision time synchronization method based on waveform matching is presented. Firstly, the data correlation between FBG and DPOS is analyzed. Then the main time error factors, sampling frequency and time delay are determined. On this basis, the empirical mode decomposition and wavelet analysis are used to extract and match the vibration data from the FBGS and bending angle data calculated by DPOS, thus updating the time-varying sampling frequency and time delay of FBGS, and finally achieving high-precision time synchronization between FBGS and DPOS. Results of ground dynamic experiment show that the standard deviation and mean value of FBG time error is less than 4ms and 2ms respectively, and the deformation displacement error of synchronized FBG data is less than 1%, which provides a prerequisite for high-precision transfer alignment of DPOS.