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Chris
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 Posted: Mon Jun 04, 2007 2:19 am Post subject: V2 / A4 Guidance |
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I have been trying to understand how the A4's gyroscopically
stabilized platform worked. Specifically the guidance version that
had a platform mounted inside of a three-axis gimbal. The platform
had 3 gyroscopes on it, one for each axis, to keep the platform fixed
as the missile moved, thus providing a reference for position.
Why were three gyroscopes needed? Was each hard-mounted to this
platform? If a gyroscope tends to maintain position why use three and
not one? |
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Henry Spencer
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| Posted: Mon Jun 04, 2007 7:40 am Post subject: Re: V2 / A4 Guidance |
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In article <1180909184.043039.39880@k79g2000hse.googlegroups.com>,
Chris <kayak10ft@aol.com> wrote:
| Quote: |
...3 gyroscopes on it, one for each axis, to keep the platform fixed
as the missile moved, thus providing a reference for position.
Why were three gyroscopes needed? Was each hard-mounted to this
platform?
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No, the way this works is that each gyroscope is used to *sense* one axis
of motion, and the associated electronics package then drives the platform
in the opposite direction so the sensor gyro's output always reads zero.
The gyros are purely sensors; the system doesn't rely on them physically
resisting platform rotation.
| Quote: |
If a gyroscope tends to maintain position why use three and not one?
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Because a single gyro does not resist rotation around its own axis.
Worse, any *combination* of gyros mounted firmly to a rigid platform is
equivalent to a single gyro having the same total angular momentum, as
far as physical resistance to rotation goes. You can't use gyroscopic
"stiffness" to provide three-axis stabilization for a platform -- it
doesn't work.
Moreover, a gyro used for stiffness has to be much bigger and heavier than
ones used as pure sensors.
As for why you need three gyroscopic *sensors* for three-axis stability,
that gets into details of hardware; the quick summary is that it turns out
to be rather easier to sense only one axis of rotation per gyro.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. | henry@spsystems.net |
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