RATE INTEGRATING GYROSCOPE TUNED BY FOCUS ION BEAM TRIMMING AND INDEPENDENT CW/CCW MODES CONTROL

In this paper, structural asymmetries in a dual-axis symmetric resonator were reduced by FIB-trimming and electrostatic tuning and then fully compensated by the driving signal adjustment to achieve operation as a rate integrating gyroscope ( RIG) for direct angle measurement. The as-fabricated frequency difference was minimized from 145 Hz to 24 Hz by applying symmetric focus ion beam (FIB) trimming on the suspension springs. The mode matching and quadrature null were further achieved by electrostatic softening the non-diagonal stiffness with a DC bias of 45 V. Finally, two degenerated modes were fully decoupled with a cross-coupling as small as 100 ppm enabled by adjusting the amplitude ratio and phase difference between the two-axis driving signals. The angle locking phenomenon was prevented and a 1.8 degrees/s self-precession rate was observed. The phase difference between clockwise (CW) and counterclockwise (CCW) modes, i.e. the RIG output, could be successfully modulated by a step-changed rotation. A rotation rate as small as 8.5 degrees/s could be detected.