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 about one axis. 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.

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