WHAT IS A GYROSCOPE?

A gyroscope (from Ancient Greek γῦρος gûros, "circle" and σκοπέω skopéō, "to look") is a device
used for measuring or maintaining orientation and angular velocity.[1][2] It is a spinning wheel or disc
in which the axis of rotation is free to assume any orientation by itself. When rotating, the
orientation of this axis is unaffected by tilting or rotation of the mounting, according to
the conservation of angular momentum.
Gyroscopes based on other operating principles also exist, such as the microchip-packaged MEMS
gyroscopes found in electronic devices, solid-state ring lasers, fibre optic gyroscopes, and the
extremely sensitive quantum gyroscope. It works on the principle of conservation of angular
momentum.
Working of a gyroscope

A gyroscope is a wheel mounted in two or three gimbals, which are pivoted supports that allow the
rotation of the wheel about a single axis. A set of three gimbals, one mounted on the other with
orthogonal pivot axes, may be used to allow a wheel mounted on the innermost gimbal to have an
orientation remaining independent of the orientation, in space, of its support. In the case of a
gyroscope with two gimbals, the outer gimbal, which is the gyroscope frame, is mounted so as to
pivot about an axis in its own plane determined by the support. This outer gimbal possesses one
degree of rotational freedom and its axis possesses none. The inner gimbal is mounted in the
gyroscope frame (outer gimbal) so as to pivot about an axis in its own plane that is always
perpendicular to the pivotal axis of the gyroscope frame (outer gimbal). This inner gimbal has two
degrees of rotational freedom.

The axle of the spinning wheel defines the spin axis. The rotor is constrained to spin about an axis,
which is always perpendicular to the axis of the inner gimbal. So the rotor possesses three degrees
of rotational freedom and its axis possesses two. The wheel responds to a force applied to the input
axis by a reaction force to the output axis.

The behaviour of a gyroscope can be most easily appreciated by consideration of the front wheel of
a bicycle. If the wheel is leaned 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.

A gyroscope flywheel will roll or resist about the output axis depending upon whether the output
gimbals are of a free or fixed configuration. Examples of some free-output-gimbal devices would be
the attitude reference gyroscopes used to sense or measure the pitch, roll and yaw attitude angles in
a spacecraft or aircraft.

The centre of gravity of the rotor can be in a fixed position. The rotor simultaneously spins about
one axis and is capable of oscillating about the two other axes, and it is free to turn in any direction
about the fixed point (except for its inherent resistance caused by rotor spin). Some gyroscopes have
mechanical equivalents substituted for one or more of the elements. For example, the spinning rotor
may be suspended in a fluid, instead of being mounted in gimbals. A control moment gyroscope
(CMG) is an example of a fixed-output-gimbal device that is used on spacecraft to hold or maintain a
desired attitude angle or pointing direction using the gyroscopic resistance force.

In some special cases, the outer gimbal (or its equivalent) may be omitted so that the rotor has only
two degrees of freedom. In other cases, the centre of gravity of the rotor may be offset from the axis
of oscillation, and thus the centre of gravity of the rotor and the centre of suspension of the rotor
may not coincide.

TYPES OF GYROSCOPES

MEMS gyroscopes found in electronic devices, solid-state ring lasers, fibre optic gyroscopes, and the
extremely sensitive quantum gyroscope.

Dopplers effect

The Doppler effect (or the Doppler shift) is the change in frequency or
wavelength of a wave in relation to an observer who is moving relative to the
wave source.[1] It is named after the Austrian physicist Christian Doppler, who
described the phenomenon in 1842.

A common example of Doppler shift is the change of pitch heard when a

The reason for the Doppler effect is that when the source of the waves is
moving towards the observer, each successive wave crest is emitted from a
position closer to the observer than the previous wave.[2][3] Therefore, each
wave takes slightly less time to reach the observer than the previous wave.
Hence, the time between the arrival of successive wave crests at the observer
is reduced, causing an increase in the frequency. While they are traveling, the
distance between successive wave fronts is reduced, so the waves "bunch
together". Conversely, if the source of waves is moving away from the
observer, each wave is emitted from a position farther from the observer than
the previous wave, so the arrival time between successive waves is
increased, reducing the frequency. The distance between successive wave
fronts is then increased, so the waves "spread out".

For waves that propagate in a medium, such as sound waves, the velocity of
the observer and of the source are relative to the medium in which the waves
are transmitted.[1] The total Doppler effect may therefore result from motion of
the source, motion of the observer, or motion of the medium. Each of these
effects is analyzed separately. For waves which do not require a medium,
such as light or gravity in general relativity, only the relative difference in
velocity between the observer and the source needs to be considered.

In classical physics, where the speeds of source and the receiver relative to
the medium are lower than the velocity of waves in the medium, the

relationship between observed frequency and emitted frequency is

where

is the velocity of waves in the medium;

is the velocity of the receiver relative to the medium; positive if the

is the velocity of the source relative to the medium; positive if the