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

Hemispherical resonator gyroscope (HRG) is a high-precision inertial sensor for the measurement of rate and attitude angle, and the fused silica hemispherical resonator is the key component of HRG, which the ultralow 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 article, 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 that the identification error of frequency split and stiffness-axis-angle is less than $3.58{\times }10^{-{7}}$ Hz and 0.0207°, respectively. Then, the hardware of trimming system including vacuum chamber with ion mill and neutralizer, fiber optic interferometer, and field-programmable gate array (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 0.0005 Hz and the best result can achieve 0.00005 Hz.