Gyroscopes used in mobile phones are inexpensive but inaccurate. Now, University of Michigan researchers have developed a highly accurate gyroscope that could help drones and autonomous cars stay on track without a GPS signal.
"Our gyroscope is 10,000 times more accurate but only 10 times more expensive than gyroscopes used in your typical cell phones. This gyroscope is 1,000 times less expensive than much larger gyroscopes with similar performance," said Khalil Najafi, the Schlumberger Professor of Engineering at U-M and a professor of electrical engineering and computer science, in an article appearing on the University of Michigan website.
The accuracy becomes critical for an autonomous vehicles, which typically use high-performance gyroscopes that are larger and much more expensive.
"High-performance gyroscopes are a bottleneck, and they have been for a long time. This gyroscope can remove this bottleneck by enabling the use of high-precision and low-cost inertial navigation in most autonomous vehicles," added Jae Yoong Cho, an assistant research scientist in electrical engineering and computer science.
The key to making this affordable, the small gyroscope is a nearly symmetrical mechanical resonator. It resembles a Bundt pan crossed with a wine glass, made one centimeter wide. As with wine glasses, the duration of the ringing tone produced when the glass is struck depends on the quality of the glass, but instead of being an aesthetic feature, the ring is crucial to the gyroscope's function. The complete device uses electrodes placed around the glass resonator to push and pull on the glass, making it ring and keeping it going.
The way that the vibrating motion moves through the glass reveals when, how fast and by how much the gyroscope spins in space.
To make their resonators as perfect as possible, Najafi's team starts with a nearly perfect sheet of pure glass, known as fused-silica, about a quarter of a millimeter thick. They use a blowtorch to heat the glass and then mold it into a Bundt-like shape, known as a "birdbath" resonator since it resembles an upside-down birdbath.