### Physics behind Gyroscope

```By: Wang Po En(3o3)
Definition
History
Physics Behind Gyroscope
Variations
Applications
The End
•
•
•
•
A gyroscope is a device for measuring or maintaining
orientation, based on the principles of conservation of
angular momentum.
A mechanical gyroscope consists of a spinning wheel or
disk with its axle free to move in any orientation.
This orientation changes very little when an external
torque is given due to its high rate of spin.
As a result, the orientation of the spinning wheel
remains almost constant while the other axles move in
all directions.
•
•
•
•
In 1817, Johann Bohnenberger from Germany made a
gyroscope-like instrument, a rotating massive sphere,
which he called the ‘Machine’.
In 1832, Walter R. Johnson, an American, developed a
similar device that was based on a rotating disk.
Later on, the French Mathematician Pierre-simon Laplace
used it as a teaching aid and this came to the attention of
Léon Foucault.
In 1852, Foucault used it in an experiment involving the
rotation of the Earth, and that was when he gave this
instrument its modern name. Gyro(‘rotation’ in Greek)
Scope(‘to see’ in Greek)
•
•
•
•
•
A gyroscope consists of a rotor meant for spinning
The journals of the rotor is mounted in an inner gimbal
for oscillation.
The inner gimbal is then mounted in an outer gimbal
for oscillation.
The outer gimbal is mounted so as to pivot about an
axis in its own plane.
The inner gimbal is mounted in the outer gimbal so as
to pivot about an axis that is perpendicular to the axis
of the outer gimbal.
•
•
•
The behaviour of a gyroscope can be illustrated with
the front wheel of a moving bicycle.
If the wheel is moved away from the vertical so that
the top of the wheel moves to the left, the forward rim
of the wheel also turns to the left.
In other words, rotation on one axis of the turning
wheel produces rotation of the third axis.

When the rotor is turning at a high rate, it stays at a
fixed orientation, while the inner gimbal and the outer
gimbal oscillate in all directions, perpendicular to each
other.

There are many different types of instruments that are
variants of the gyroscope model:
◦
◦
◦
◦
Gyrostat
MEMS
FOG
DTG
•
•
•
A gyrostat was designed by Lord Kelvin to illustrate the
more complicated state of motion of a spinning body
when free to wander about on a horizontal plane.
It consists of a massive flywheel, similar to a hoop or
bicycle wheel, concealed in a solid casing.
Its behaviour on a table clearly reverses the ordinary
laws of static equilibrium due to the gyrostatic
behaviour of the flywheel when rotated rapidly.
•
•
•
A MEMS(Micro Electro-Mechanical System) gyroscope
is a type of vibrating structure gyroscope.
It works as a gyroscope based on the principle that a
vibrating object tends to keep vibrating in the same
plane as its support is rotated.
It is a much more inexpensive alternative with similar
accuracy compared to a mechanical gyroscope.





A FOG, or fibre optic gyroscope, is a gyroscope that makes
use of the interference of light to detect mechanical
rotation.
It is made up of a coil of as much as 5km of optical fibre.
Two light beams travel along the fibre in opposite
directions and the beam travelling agains the rotation
experiences a shorter path than the other beam.
The resulting phase shift affects how the beams interfere
when they meet.
The intensity of the combined beam indicates the extent of
mechanical rotation of the device.


A FOG provides extremely precise rotational rate
information.
It is used in high performance space applications,
which require high precision in order to function.



A DTG, or dynamically tuned gyroscope, consists of a
rotor suspended by a universal joint with the pivots.
The dynamic inertias cancel each other, freeing the
rotor from torque, which gives the rotor an ideal
condition for gyroscope.
The fact that a DTG is relatively inexpensive but has
industrial precision makes it suitable for flight control
and flight simulators.
Gyroscope makes remote
control helicopters more
user-friendly and easier to control.
Flying remote control helicopters used
to be as hard as balancing a marble
on a smooth plane, but with the use
of a gyroscope
it becomes
much more
stable and
easier to control.
Nitendo Wii makes use of gyroscope by using in the
controller (Wii Remote) to sense motion to make game
play more enjoyable and realistic.
Every iPhone 4 has a
built-in gyroscope
which allows more
precise motion
sensing and six-axis
control that includes
rotation around
gravity.
FOG is used to stablise
antenna on a satellite as it
requires high precision.
FOG is used in RPG
to stabilise the missile
when it is moving towards the target.
FOG is used in
military GPS for
enhanced accuracy.
DTG is used in tanks so that
they can
lock on the
targets
while moving
in all directions.
DTG is used in aircrafts to monitor whether the
aeroplanes are flying level and control the rate
of turning by tilting the aeroplanes at different
angles.










www.wikipedia.org
www.apple.com
http://www.sagem-ds.com/eng/site.php?spage=02010306
http://www.nintendo.com/