Micro-fabricated gyroscope accuracy beats MEMS

November 30, 2014 // By R. Colin Johnson
"The most accurate gyroscope in the world" is the claim made by Qualtre (Marlborough, Mass.) for its bulk-acoustic wave (BAW) single-axis gyroscope. Originally licensed from the Georgia Institute of Technology (Georgia Tech, Atlanta) the BAW uses a totally different approach from the traditional "tuning fork" type of architecture used by all other MEMS gyroscopes.

"TFGs [tuning-fork gyroscopes] have hit the wall in terms of performance, but bulk acoustic wave gyroscopes have overcome these obstacles," said Sreeni Rao, vice president of Vertical Markets at Qualtre told EE Times. "And we have a head start by holding the patents on that which could improve those tuning-fork gyros."

The single crystal silicon disk (center) moves to track angular motion, which is sensed capacitively by the electrodes around the edge.
(Source: Qualtre)

According to Rao, since licensing the basic patents from Georgia Tech, Qualtre has been busy improving and perfecting the BAW gyroscope by improving it in ways tuning forks could also be improved. So far they have over 30 granted patents with more pending. Their first generation gyroscope, four years in development, is a three-axis unit that Qualtre has been sampling to select customers since June 2014.

Since it is more expensive but higher performance, than three-axis tuning-fork MEMS gyros, its first customers are manufacturers of heavy industrial machinery who are willing to pay for higher performance, and platforms that must maintain absolutely perfect stability -- or as close to it as they can get. For instance, satellite and other antennae on military ships must maintain near perfect aim at the antennae with which they are communicating. Qualtre claims its BAW-based gyroscopes outperform all other types for stabilising ship antenna platforms as the ship yaws, rolls and pitches.

Its newest single axis BAW gyroscope, on the other hand, has capitalszed on those 30 granted patents to make it even higher performance than the most expensive single-axis tuning fork gyroscope, as well as lower in cost.