HH gyro's "other" uses
02-12-2003, 11:36 PM
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HH gyro's "other" uses
Has anyone ever tried to hook a heading hold gyro up for latitude stabilization in a Helli or aircraft to get constant angles relative to stick position? And on a side note, how exactly does a heading hold gyro work?
The only way I can justify them functioning is they use math inside the gyro to compensate for any piro not by canceling out the piro but by adding extra control input to actually correct the deviation not just jangle it. I.E. If it spins for .5 seconds at 5 degrees per second for it to try to spin it in the opposite direction for .5 seconds at 5 degrees per second to actually put it back in it's original position, not just stop it from spinning. Granted the time pieces used would be smaller. Anyone know? And exactly how accurate are they? Can they be used as reliable attitude measuring devices, or are they still basically advanced rate sensors?
The only way I can justify them functioning is they use math inside the gyro to compensate for any piro not by canceling out the piro but by adding extra control input to actually correct the deviation not just jangle it. I.E. If it spins for .5 seconds at 5 degrees per second for it to try to spin it in the opposite direction for .5 seconds at 5 degrees per second to actually put it back in it's original position, not just stop it from spinning. Granted the time pieces used would be smaller. Anyone know? And exactly how accurate are they? Can they be used as reliable attitude measuring devices, or are they still basically advanced rate sensors?
02-13-2003, 12:13 AM
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HH gyro's "other" uses
Your supposition is more or less correct. They are based on rate sensors, and integrate the output to derive positions.
The rudder input is interpreted as a rotation-rate command. E.g. full rudder input could be 720 deg/s, and 50% rudder 360 deg/s. In practice, there is a fair amount of expo applied so it's possible to accurately control rotation down to 5 deg/s or less.
A zero stick you get no rotation, so if you were banked at 45 deg with a HH gyro on aileron, that bank angle will be held (or attempted to be held) against external influences until you change the bank angle using the stick.
They are reliable in the short term. Long term (more than a minute or so) you may start to see drift. Some are better than others with respect to drift.
The rudder input is interpreted as a rotation-rate command. E.g. full rudder input could be 720 deg/s, and 50% rudder 360 deg/s. In practice, there is a fair amount of expo applied so it's possible to accurately control rotation down to 5 deg/s or less.
A zero stick you get no rotation, so if you were banked at 45 deg with a HH gyro on aileron, that bank angle will be held (or attempted to be held) against external influences until you change the bank angle using the stick.
They are reliable in the short term. Long term (more than a minute or so) you may start to see drift. Some are better than others with respect to drift.
