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Jun 11, 2007, 03:36 AM
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Really really really really small numbers


So finally had a break with Vicacopter. Gyro elimination is stable enough to fly. It's not like flying in molasses like the PG-03 gives. It's more like flying on a spring. It took really really small adjustments to the PID constants.

P=0.1 I=0.001 D=0.05

Then,

PID limits: -0.1 - 0.1
Lowpass filter bandwidth: a=0.08
Gyro sampling rate: 172Hz
PID iteration rate: 25Hz
Gyro scale: 3000

The PID loop really did require tuning. Increase D just 0.05 more and she oscillates. Increase P by 0.05 and she oscillates. Get rid of I and she oscillates. The constants aren't symmetric and it took hours of running in and out of dumpy apartment, flashing firmware to get it this tuned.

The lesson: we have to set the PID constants using the transmitter, from a graphical interface, in the field.

So gyro elimination was originally tackled to fix problems in the Kalman filter and the lack of space in U. Know. Where.. Unfortunately, the Kalman filter ended up too unreliable to trust with manual yaw control so it was moved to raw gyro data.

The indoor test stand moved gyro elimination forward really fast, but took significant trimming to overcome the loss of main blades, and didn't have real vibration effects.

Now the bad news. The IDG300 for yaw is starting to fail. It occasionally fails to initialize and returns constant voltage. Power cycling has fixed the problem so far. We have 1 spare gyro and after that, may end up back with the PG-03 and a breakout connector from its gyroscope for autopilot. This is the way it should have been done originally.

In today's video, the IDG300 for yaw failed on the first flight, so we have footage of flight with no tail gyro. A power cycle got the IDG300 running and the rest is software tail gyro.

Also with the latest radio update, we have a 1 second delay from the first valid radio packet to the first servo command. So it's impossible for the motor to start if the transmitter is off, even if a freak CRC check for an invalid packet succeeds. It would take 2 successful CRC checks exactly 1 second apart for the motor to start.



Goo Tube is taking 24 hours to upload videos. Here is a higher quality version on Goo Tube.

Software tail gyro success (1 min 34 sec)


And the Goog Video version from yesterday.

http://video.google.com/videoplay?do...29001200372395
Last edited by Jack Crossfire; Jun 11, 2007 at 12:44 PM.
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