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Aug 13, 2007, 01:27 PM
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Characterizing anomalies


Still with no autonomous position hold, it's time to get back to characterizing anomalies. The attitude hold tended to stop working after several attitude hold maneuvers in a single campaign. It also didn't work at all in wind. Increased the limits on the cyclic feedback and attitude hold seemed to return. Unfortunately there was no wind by that time.

To test attitude hold, we yank the cyclic to the point where she stops tilting because the autopilot is fighting. Then release the cyclic to verify she returns to the starting attitude. For the most part, it works, but repeated yanking in the same direction and the starting attitude seems to drift. The same thing happens with yaw, and more obviously.

Maybe the gyros are drifting too much and requiring more accelerometer weight. Not sure why the drift didn't show up in INS plots. Maybe didn't do enough repeated tilt in the same direction, maybe the drift was too slight, or maybe the drift was only diffused over very long time periods but during a single autopilot run was significant.

Maybe the feedback is getting just within range of the starting attitude and giving up. It could be falling below some minimum servo deflection, below which the feedback has no effect.
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