Laser Gyros - v. basic info rqd
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Join Date: May 2002
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Laser Gyros - v. basic info rqd
Anyone have any web references which could explain the workings of laser gyros to me in very simple terms ?
Have searched PPRUNE and the web but found it all a little too technical. Understand basic Physics, i.e. lasers, light propagation, wavelength etc
Thanks
Have searched PPRUNE and the web but found it all a little too technical. Understand basic Physics, i.e. lasers, light propagation, wavelength etc
Thanks
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The objective of a "gyro" is to provide a static directional reference in space. Therefore all it has to do is either
- maintain its orientation in space so you can measure your offset -> classic mechanical gyro
- measure every tiny change in its orientation in space and add it all up -> laser gyro
Now, how does the laser gyro measure rotation? Imagine a monochromatic light beam, that travels around in a circle.
Without movement, a detector will see nothing but the original wavelength of the laser beam.
As soon as you move, the wavelength at the detector will change, depending on rotation speed and direction in relation to the laser loop.
All you need, really, are three laser loops arranged in 3D and some expensive hardware to do the maths - pronto!
- maintain its orientation in space so you can measure your offset -> classic mechanical gyro
- measure every tiny change in its orientation in space and add it all up -> laser gyro
Now, how does the laser gyro measure rotation? Imagine a monochromatic light beam, that travels around in a circle.
Without movement, a detector will see nothing but the original wavelength of the laser beam.
As soon as you move, the wavelength at the detector will change, depending on rotation speed and direction in relation to the laser loop.
All you need, really, are three laser loops arranged in 3D and some expensive hardware to do the maths - pronto!
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A LASER provides coherent light, that is the waves are all in sync. This allows you to observe/count their movment across a detector. Light is to all intents and purposes massless so it is not affected by the movements of the aircraft. Your detector can therefore count the number of wavefronts passing it and turn this into a physical displacement. The waves are obviously incredibly small so you need a very very fast counter. After that however it's just maths.
You'll get this off Google but to help try 'Ring Laser'
You'll get this off Google but to help try 'Ring Laser'
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Laser Gyro
Some time ago I found a nice description in the Boeing Maintenance Manual of the B737. I'll try to recall here:
A laser is emitting monochromatic light (that is light with a single wavelength).
This light is sent through the gyro. One part of it through 2 mirrors in a right hand triangle pattern and another part through the same 2 mirors in a left hand triangle pattern.
At the end there is a receiver, the result of this two light patterns is a bright-dark-bright-dark-bright-dark-bright-... pattern.
If the gyro now is turned right or left, this pattern also moves right or left as the time and as a result of the time the distance travelled through the device changes.
This movement of the resulting pattern can be measured and the computer can calculate the rate of turn with some easy maths.
Hope it helps...
FL
A laser is emitting monochromatic light (that is light with a single wavelength).
This light is sent through the gyro. One part of it through 2 mirrors in a right hand triangle pattern and another part through the same 2 mirors in a left hand triangle pattern.
At the end there is a receiver, the result of this two light patterns is a bright-dark-bright-dark-bright-dark-bright-... pattern.
If the gyro now is turned right or left, this pattern also moves right or left as the time and as a result of the time the distance travelled through the device changes.
This movement of the resulting pattern can be measured and the computer can calculate the rate of turn with some easy maths.
Hope it helps...
FL
