Micromachined gyroscope concept allowing interchangeable operation in both robust and precision modes

Abstract

This paper presents a new gyroscope design concept with a multi-degree of freedom (DOF) sense mode enabling interchangeable operation in robust or precision modes. This is accomplished using a complete 2-DOF coupled system which, unlike previous multi-DOF designs based on dynamic vibration absorbers, allows for the specification of the sense mode resonances and coupling between the masses independent of operational frequency. The robust mode corresponds to operation between the 2-DOF sense mode resonant peaks providing a response gain and bandwidth controlled at the design level by frequency spacing; the precision mode, however, relies on mode-matching the drive to one of the sense mode resonant frequencies where larger response gains are achieved through vacuum operation. The complete 2-DOF sense mode provides the gyroscope with distinct advantages over similar devices based on 1-DOF systems: the robust mode introduces a gain advantage versus conventional mismatched operation, while the precision mode gain-bandwidth is larger for the same pressures. Experimental rate characterization of a silicon-on-insulator prototype in air for both robust and precision modes demonstrated scale factors of 0.282 and 0.690 mV/°/s, respectively, while the scale factor improvement due to precision mode operation is projected to increase by 40 dB for operation in 1 mTorr vacuum.