MIcromachined Cylindrical Acoustic Resonator for Angular Rate Sensing

The Army wishes to develop low cost, acceleration survivable gyroscopes and accelerometers for peojectile guidance systems. SatCon has identified a novel angular rate sensor which has been shown to be undamaged after gun induced accelerations of up to 25,000 g. Our device is a microfabricated adaption of the so called "wine glass resonator" but in a version which is electrostatically excited and sensed. A long, thin cylindrical structure is driven to produce a standing acoustic mode around the rim of the cylinder. The shift of the nodal positions is correlated with rotation rate and detected by a high frequency capacitance sensor. The rate sensor is inherently insensitive to high linear accelerations unlike cantilevers and spinning disc gyros yet insensitive to first order temperature-caused variations since resonance is electronically maintained. We have a significant opportunity to fabricate the structure with the LIGA process by virtue of our access to the CAMD facility at LSU. This technique is optimized for mold production and if combined with hybridized drive and sensing electronics, allows inexpensive mass production. The Phase I program will establish the optimum structure geometry, the details of a tailored LIGA microfabrication process, and a component level design of the sensing and drive electronics. In Phase II, the micro-resonator will be fabricated and tested with off-chip electronics.