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This thread is privately moderated by Jack Crossfire, who may elect to delete unwanted replies.
Aug 10, 2007, 03:44 PM
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GPS terrorism

Well OK. 1Hz GPS updates aren't fast enough 2 fly a copter. With large feedback deflections, she would oscillate exponentially before hitting a very large movement that caused uncontrollable yaw followed by loss of orientation. With small feedback, she would get overtaken by the wind. It would probably work if there was no wind.

After a brief period, Rain Ramon is back to strong west wind at night. So we're back to accelerometer derived position. Dividing the accelerometer by the discrete cosine matrix of the attitude measurement should give acceleration in world frame. That would only work for brief periods, because acceleration over time becomes the attitude measurement and that points acceleration straight down.

Then it's the same trick as the attitude measurement. Blend a fraction of GPS position with accelerometer derived position 200 times a second. Only this time GPS changes once a second. Probably can get some blended velocity, but forget about blended acceleration.

Unfortunately, this isn't the most efficient algorithm. A perfect inertial navigation system feeds everything back into everything else. Accelerometer derived attitude into gyro derived attitude into accelerometer derived position back into accelerometer derived attitude.

That's probably what the Kalman did but it was too unstable, a condition of garbage being fed back instead of being thrown out.
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