A gyroscope (or angular rate sensor) is a device that provides an output in response to a rotation applied to it.
Angular rate sensors, are used whenever rate of turn sensing is required without a fixed point of reference. The speed of rotation is measured in ‘inertial space’ and, as such, our gyros are also part of a family of ‘inertial sensors’. This separates gyros from any other means of measuring rotation, such as a tachometer. The speed of rotation can be defined in terms of RPM but more commonly as °/s.
Traditionally, gyros (gyroscopes) were much like the children’s toy – a spinning mass supported such that its position in inertial space remains fixed and allowing rotation of its support structure to be measured. Indeed, such gyros remain the technology of choice for a variety of applications where accuracy is paramount (and where other high-precision sensors, like ring-laser gyros, remain unaffordable).
But over the last twenty years, the world of inertial sensors has turned on its head with the emergence of ’solid state’ non-rotating rate sensors, still colloquially known as gyros. Their construction in silicon (or sometimes quartz) explains their other descriptive name of ‘MEMS’ (Micro machined Electro-Mechanical Systems) devices.
MEMS gyros emerged through the need to overcome the biggest problems associated with traditional spnning wheel gyros – mechanical issues such as fragility, reliability, stiction, wear, backlash and overall life. Based a vibrating element, MEMS gyros sense rotation rate through a phenomenon known as coriolis, not too different to the operating concepts of traditional gyros, namely precession and nutation.
Comparison Spinning Wheel and Solid State Gyroscopes
Conventional spinning wheel gyroscope:
- Have been available for more then 100 years
- Very accurate
- Very expensive (intricate manufacture and set up)
- Difficult to integrate
Everyone knows the conventional gyroscope as a fairly massive rotor suspended in light supporting rings called gimbals which have nearly frictionless bearings and which isolate the central rotor from outside torques. At high speeds, the gyroscope exhibits extraordinary stability of balance and maintains the direction of the high speed rotation axis of its central rotor.
If a gyroscope is tipped, the gimbals will try to reorient to keep the spin axis of the rotor in the same direction. If released in this orientation, the gyroscope will precess in the direction because of the exerted by gravity on the gyroscope.
Solid state gyroscopes are relatively new. Available in last 15-20 years:
- Low Cost
- Simple
- No moving “parts”
- Very robust and reliable
Our MEMS gyroscopes are Vibrating Structure Gyroscopes. These VSGs use cylinder or ring structures and work on the Coriolis principle where forces are observed when a linear motion occurs in a rotating frame.
The closed loop technology provides excellent scale factor and performance over wide rate and temperature ranges. The technology has a very rugged design and construction and delivers superior performance than its competitors using other structures (e.g. tuning fork).
How the vibrating structure works
No angular rate applied
