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Vibrating structure gyroscope
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In science, a vibrating structure gyroscope is a type of
gyroscope that functions much like the halteres
of insects. Miniaturized devices on this principle
can be used as a relatively inexpensive type of
attitude indicator.
The physical principle is very simple: a vibrating
object tends to keep vibrating in the same plane
as its support is rotated. It is therefore much
simpler and cheaper than is a conventional rotating
gyroscope of similar accuracy.
In the engineering literature, this type of device
is also known as a Coriolis vibratory gyro because
as the plane of oscillation is rotated, the response
detected by the transducer results from the coriolis
term in its equations of motion ("Coriolis force").
ider two proof masses vibrating in plane (as in the MEMS gyro) at frequency .
Discussion
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Encyclopedia
In science, a vibrating structure gyroscope is a type of
gyroscope that functions much like the halteres
of insects. Miniaturized devices on this principle
can be used as a relatively inexpensive type of
attitude indicator.
The physical principle is very simple: a vibrating
object tends to keep vibrating in the same plane
as its support is rotated. It is therefore much
simpler and cheaper than is a conventional rotating
gyroscope of similar accuracy.
In the engineering literature, this type of device
is also known as a Coriolis vibratory gyro because
as the plane of oscillation is rotated, the response
detected by the transducer results from the coriolis
term in its equations of motion ("Coriolis force").
Theory of operation
Consider two proof masses vibrating in plane (as in the MEMS gyro) at frequency . Recall that the Coriolis effect induces an acceleration on the proof masses equal to , where is velocity and is the angular rate of rotation. The in-plane velocity of the proof masses is given by: , if the in-plane position is given by . The out of plane motion , induced by rotation, is given by:
is the mass of the proof mass
is the spring constant in the out of plane direction
is magnitude of a rotation vector in the plane of and perpendicular to the driven proof mass motion
Implementations
Piezoelectric gyroscope
A piezoelectric material can be induced to vibrate, and lateral motion due to coriolis force can be measured to produce a signal related to the rate of rotation .
Wine glass resonator
Also called the hemispherical resonator gyro, or the HRG. Hemisphere driven to resonance and nodal points measured to indicate rotation.
Tuning fork gyroscope
A pair of test masses are driven to resonate and their displacement from the plane of oscillation is measured to produce a signal related to the rate of rotation.
The tuning fork gyro is not a new concept. F.W.Meredith took out a patent for such a device in 1942 when he was working at the RAE(Royal Aircraft Establishment). Further development was carried out at the RAE in the late 1950s by Messrs G.H.Hunt and A.E.W.Hobbs who demonstrated a performance of less than 1o/hour drift.
Vibrating wheel gyroscope
A wheel is driven to rotate a fraction of a full turn about its axis. Tilt of the wheel is measured to produce a signal related to the rate of rotation..
MEMS gyroscope
Relatively inexpensive (around US$30 per part in quantity as of late 2007) vibrating structure gyroscopes using MEMS technology are available. These can be implemented as the tuning fork resonator, vibrating wheel or (planar) wine glass resonator .
Applications
Spacecraft orientation
The oscillation can also be induced and controlled in the vibrating structure gyroscope for the
positioning of spacecraft such as . These small made of quartz operate in vacuum. They provide accurate 3 axis positioning of the spacecraft and are highly reliable over the years as they don't have any moving parts.
Automotive
Automotive yaw sensors can be built around vibrating structure gyroscopes. These are used to detect error states in yaw compared to a predicted response when connected as an input to electronic stability control systems in conjunction with a steering wheel sensor. Advanced systems could conceivably offer rollover detection based on a second VSG but it is cheaper to add longitudinal and vertical accelerometers to the existing lateral one to this end.
Entertainment
The Nintendo Game Boy Advance game WarioWare: Twisted! uses a piezoelectric gyroscope to detect rotational movement. The Nintendo Wii MotionPlus accessory uses multi-axis MEMS gyroscopes to augment the motion sensing capabilities of the Wii Remote.
Photography
Many Image stabilization systems on video and still cameras employ vibrating structure gyroscopes.
Hobbies
Vibrating structure gyroscopes are commonly used in radio-controlled helicopters to help control the helicopter's tail rotor or in radio-controlled airplanes to help keep the tail steady during take-off or hand (especially with discus launched gliders) launch.
Other
The Segway Human Transporter employs a vibrating structure gyroscope made by Silicon Sensing Systems to maintain stability of the operator platform .
External links
- John Geen, Analog Devices
- Vladislav Apostolyuk
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