The High-Precision Balance Method For Hemispherical Resonator Based on Synchronous Trimming System

Hemispherical resonator gyroscope (HRG) is a high precision inertial sensor for measurement of rate and attitude angle, and the fused silica hemispherical resonator is key component of HRG which the ultra-low frequency split is required. During the entire fabrication process of the resonator, the imperfects of the resonators should be trimmed by evaluating the quality-factor and frequency split in real-time. Therefore, the high-precision balance method based on synchronous trimming system has been proposed in this paper, and the quality-factor, frequency split and principle-axis angle could be identified at the same time in a single test. At first, the high precision orbital parameter identification algorithm based on nonlinear least square method has been adopted, which shows the identification error of frequency split and stiffness-axis-angle is less than 3.58×10 ^-7 Hz and 0.0207° respectively. Then, the hardware of trimming system including vacuum chamber with ion mill and neutralizer, fiber optic interferometer and FPGA control board with the proposed identification algorithm has been implemented. Finally, the focus ion beam (FIB) etching experiment has been carried out to verify the proposed trimming method. The experimental result shows that the proposed method has excellent performance, which can reduce the frequency split of all resonators under 0.0005Hz and the best result can achieve 0.00005Hz.