Identification of limiting damping mechanisms in a high quality factor hybrid resonator of space application gyroscope

Abstract

• Studied hybrid gyroscope resonator damping mechanisms with imperfection sensitivity. • Realized thin film coated high precision resonator with few millions quality factor. • Limiting damping mechanisms are identified at each stage from design to realization. The performance of Hemispherical Resonator Gyroscopes (HRG) is decided by the mechanical resonator’s Quality factor ( Q factor). The Q factor is a measure of energy dissipation. A Q factor of few millions is needed to realize fine resolution millimeter size of the HRG for future interplanetary satellite missions. The objective is to carry out a detailed study of thermoelastic damping (TED), anchor loss, surface loss, material internal friction and fluid damping. A hybrid resonator is designed with very low TED. One of the major contributions of the present work is the study of the effect of thin film coating and different coating configurations on TED. Extensive simulations have been carried out on the effect of different fabrication deviations on anchor loss. A unique sensitivity study of mode interactions and mass unbalance pattern on frequency split and anchor loss mismatch is also done. Based on this, dimensional and geometric tolerances are derived for precision fabrication and the precision hybrid configuration resonator is realized. Surface loss and material internal friction are estimated. Also, surface characterisation has been done using nanoindentation techniques. Q factor of few millions is obtained in a fabricated precision resonator with thin film coating. Based on the estimation of different damping mechanisms and measurements, the limiting mechanisms are identified at each stage from the design to the realization. The Q factor of an uncoated resonator is limited by the surface loss while that of a coated resonator is limited by the coating induced additional TED, the coating material internal friction and the surface loss.