Abstract
Vibration coupling in out-of-plane resonators was investigated to design low acceleration sensitivity tuning fork gyroscopes (TFGs) of out-of-plane sensing axis type. Numerical and theoretical analysis was carried out on a spring-coupled translational x-axis TFG. The vibration coupling was controlled by separating the in-phase mode (fin) from anti-phase mode (fanti). The theoretical and numerical analysis showed that the acceleration sensitivity is inversely proportional to decoupling ratio, whereas the angular rate sensitivity does not change by keeping the fanti constant. For experimental verification, we designed four types of coupled resonators and fabricated them from SOI wafer: two of them are frame-coupled and the other two are spring-coupled. In each coupling type, one adopted a translational resonator and the other adopted a torsional resonator. The measured anti-phase vibration amplitude against in-phase oscillation decreased by weakening coupling which agreed with the numerical analysis. As decoupling ratio (=(fin-fanti)/fanti) of the spring-coupled translational resonator increased from 0.09 to 0.29, the anti-phase vibration amplitude in the analysis and measurement decreased to 28% and 51%, respectively.
