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Re: [Paparazzi-devel] Tuning Suggestions?

From: Roman Krashanitsa
Subject: Re: [Paparazzi-devel] Tuning Suggestions?
Date: Tue, 20 Jan 2009 17:24:49 -0700

Hello Toby,
First of all, congratulations! You have made a huge progress, but more to come!
Here are three advices that I feel should help.
1. Before the flight take your airplane in your hands, keep it above the your head and ask someone to look at the values of pitch and roll on the ground station. They should show zero pitch, zero roll.
2. Switch to Auto1, again, check the values - they should be same. Now look at the values of desired pich and desired roll. With both of roll stick and pich stick at neutral, the desired values should be also zero.
3. Pitch airplane up, sey, 45 deg, then down 45 deg, check values of the measured pitch and roll  - they should be +45 deg and -45 deg; do the same for roll.
I think at some point you will see wrong values, and then you will know what to do.

2009/1/20 TurboTas <address@hidden>
Hi All.

I have a funjet with a tiny 2.11 installed.  I've been slowly building it over the past year or so and have achieved quite a few MANUAL flights, say around 10 for a total of about an hours flying time.  In all cases I have the ground station running so I have the telemetry files.

In MANUAL, the plane flies nice and level when hands off the stick and the neutrals have not been tweaked on the radio.  The HSI looks good on the telemetry replay.

With that in mind I have made quite a few attempts (at high altitude) at AUTO1 flight.  The first couple of flights were awful and it transpired that I had the orientation of the single axis IR sensor wrong and we had some interesting recovery flights after uncommanded rolls and pitches.  Yeuch.

Okay.  Got that problem fixed and the current issue is that each time I attempt AUTO1 flight, I get a pretty violent pitching downwards.  Occasionally I get perhaps a second of level flight before that happens.  During these breif stable spells I see a tiny roll oscillation.  I see this as a good sign that the feedback loop is working! I never let the dive get far enough to see if the plane does a bunt as I'm quick to grab it back under MANUAL control.  This all happens rather fast and the plane reaches an almost vertical dive.

Additionally, under MANUAL control, I find the plane really lively and a joy to fly.  Should I be tweaking the control throws so that the plane is more placid – maybe the problem is over control?

In all the AUTO1 test flights, it has always been nose down, rather than nose up.  I've never been tempted to try invoking AUTO1 when inverted!

My question is more of a cry for help really: Any methodologies for diagnosing the problem?  I have the log files and know how to use the graphing tool, but am not entirely sure what to look at first!  Does this sound like a tuning error or something more critical maybe wrong?  I've been looking at the replays on and off for months, but am a bit lost! I could maybe post my airframe file and\or the flight logs.

PS, I have not seen this posted in the digests over the last few months, so thought it worthy of comment: I recently did a CVS update after about 4 months and immediately noticed a huge speed increase in the GUI.  Not sure what has changed that may explain the improvement, but thanks!

Kind regards,


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