- Small, inexpensive, and highly accurate gyroscope
- Optimal for autonomous vehicles
Gyroscopes nowadays are present in most smartphones and are essential in complementing several path navigation apps. Although they do decent work while detecting the screen orientation and thus, help figure out in which direction a person is facing, they however, lack accuracy at times because of which the user faces inconvenience while travelling through an unknown location.
This problem to an extent can be ignored by a pedestrian or any person behind the wheel, but a driverless car, which heavily relies on its various sensor systems, could get lost quickly due to a loss of GPS signal.
A look inside their backup navigation systems reveals that autonomous vehicles currently use high-performance gyroscopes that are larger and much more expensive.
To solve this persisting problem, a team of researchers from the University of Michigan has developed a small, inexpensive and highly accurate gyroscope that can greatly assist autonomous vehicles to stay on track in absence of 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.
Rings like a glass
An inertial measurement unit (IMU) enables navigation without a consistent orienting signal. It is made up of three accelerometers and three gyroscopes, one for each axis in space. But existing IMUs are quite expensive. And incorporating them within the already costly autonomous vehicles is not desired.
Therefore, a key to making them small and affordable is by designing them as a symmetrical mechanical resonator. It looks like a combination of a Bundt pan and a wine glass. But as with a wine glass, where the duration of the ringing tone produced when struck depends on the glass’s quality, the gyroscopic device has electrodes placed around the glass resonator that push and pull on the glass, making it ring. This is crucial to the gyroscope’s function.
“Basically, the glass resonator vibrates in a certain pattern. If you suddenly rotate it, the vibrating pattern wants to stay in its original orientation. So, by monitoring the vibration pattern it is possible to directly measure rotation rate and angle,” said Sajal Singh, a doctoral student in electrical and computer engineering who helped develop the manufacturing process.
The vibrating motion through the glass reveals when, how fast and by how much the gyroscope spins in space.
To further perfect the resonators, about a quarter of a millimetre thick sheet of pure glass, known as fused-silica was used. Then with the help a blowtorch, the glass was heated and moulded into a Bundt-like shape (known as a “birdbath” resonator as it resembles an upside-down birdbath).
A metallic coating was subsequently added to the shell and electrodes were placed around it to initiate and measure vibrations in the glass. The entire thing was encased in a vacuum package (about half a centimetre tall) to prevent air from damping out the vibrations.
“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,” said Jae Yoong Cho, an assistant research scientist in electrical engineering and computer science.
Besides autonomous vehicles, soldiers can also benefit from this navigation equipment to help find their way in treacherous areas where GPS signals have been jammed. Warehouse robots involved in performing complex indoor navigation will also be able to do the same accurately.