Doc wrote:
What I'd like to do is spin a gyro up with one degree of freedom
perpendicular to it's spin axis and measure the angular change in the
gimbal. Much like the artificial horizons that have been in airplanes
for the last 70 years.
Artificial horizons have to sense the down vector, which _is_ an
acceleration, or they don't stay accurate for very long.
This has nothing to do with Einstein.
No, just with how the universe works. In your original post you said
"angle" without the qualifier "change". This implied some magical
absolute angle (which doesn't exist -- see the theory of General
Relativity) or the angle relative to the Earth (which requires you to
sense acceleration).
I don't need any major precision here...probably +-2 degs.
Well, that's good. But you're leaving out the other part -- 2 degrees
over what period of time? As I already stated, _all_ gyros drift. The
less you want them to drift, the more space you have to find for them,
and the more money you have to pay. But even if you build one as big as
your house, and spend 10^6 bucks on it, it'll still drift -- just not
much if you're getting your money's worth.
As far as "rate gyros", the only reason they work is based on
acceleration. Tim, "rate gyros" are quite different than actual
gyroscopes.
A "rate gyro" is any gyro that reads out in rate. The good ones have
spinning wheels inside of them.
How is an assembly with bearings, a motor, a spinning wheel and some
electronics different from an "actual" gyroscope? If an actual
gyroscope doesn't have a spinning wheel, what does it have?
Please educate me. I've been using rate gyros (with spinning wheels) in
aerospace applications for going on 10 years now -- obviously I need my
ignorance corrected. Perhaps you could call up all the major defense
suppliers and systems integrators in the world and straighten them out,
too? I'm sure it'll be taken as a public service.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
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