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DeveloperPermalink Reply by R_Lefebvre on April 30, 2012 at 9:35am

Oh man, poor guy.  I'm not sure what that does or why it changed.  In fact, I don't even think it should have changed due to an MP  update?  That's weird.

Did you take off and immediately change to Alt_Hold?  

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Permalink Reply by Wesley Chuen on April 30, 2012 at 9:58am

The heli took off from my deck, which is a few feet off the ground.  Then I swing it around to the back of my tiny backyard and hovers there.  It has a little more room both below and above.

 

There were a few things changed, and probably not the Trim_Throttle's fault.  The log was not saved again, since I was kinda frustrated and just unplugged the power.  I've switched the sonic's location, also using Ch6 to try to adjust the Rate Throttle P which was at 0.383.  I put in a range of 0.2 to 0.9 and the Ch6 was at the lowest setting.

 

Anyway, let me fix it up and test again.  This time, I would fly it a bit and make sure my sonar is working first.

 

Oh, my 3DR telem was on.  Does the rlog/tlog have the sonar information?

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DeveloperPermalink Reply by R_Lefebvre on April 30, 2012 at 10:17am

Yes, the Tlog may have some info.  Do you have it?

I don't understand why you are not getting logs.  It doesn't have anything to do with arming or disarming or how you unplug the power.  It's supposed to record the log *live*.

Hopefully once I get this little guy running I can try to figure out what's going on.

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Permalink Reply by Wesley Chuen on April 30, 2012 at 10:33am

Yea, I've noticed that I don't get logs in numerous occasions.  The only sure way to get log is to disarm it at the end of the flight.  Of course I would have to arm it at the beginning of the flight in order to disarm it.

Here is the tlog file.  I really have no idea how to browse around it.  Does the play log function always start from the beginning?  No way to browse around like the Terminal Log screen?

Attachments:

• 2012-04-30 11-57-08 slam to the ground.tlog, 736 KB

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Permalink Reply by Wesley Chuen on April 30, 2012 at 11:29am

Replaced the front torque tube gear set and testing again.  This time, I just hover.  Looking at the log, the sonar is working extremely well.

 

One more thing you may noticed that the Pitch_IN/Pitch keep increasing.  I was simply holding the heli at the same spot hovering, yet, I had to give it more and more pitch to hold it still.  Then it became a bit much, so I landed it.  Disarm and re-arm, and hover again.  I have no "I" in the Stab Roll/Pitch just to rule out that the "I" would have something to do with it.

 

Attachments:

• 2012-04-30 14-14 1 nice sonar.log, 287 KB

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DeveloperPermalink Reply by Randy on May 2, 2012 at 8:17am

Wesley,

     So we refer to this as a case of "the leans".  What's going on is most likely you have some vibration in your frame which is creating a lot of interference for the accelerometers.  This noise causes the APM to slowly lose track of it's attitude so you need to correct it more and more.

     I've looked at your logs again and the pitch is really quite weird.  It has this gap between what you're telling it to do and what it's actual pitch is...and it never seems to get to the right pitch.  I think you need some I term or maybe slightly higher P.

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Permalink Reply by Wesley Chuen on May 2, 2012 at 8:22am

I have P=0.7, I=0, and I tried some random "I" numbers like 0.1 or 0.01 but didn't seem to matter.  I'll try P=0.8 for a little.

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DeveloperPermalink Reply by R_Lefebvre on May 2, 2012 at 8:57am

Do you have an Xbee for telemetry? Tridge would like Tlogs of your issue here.  We thought we had this licked, so it's strange that you're getting it again.

It'll be interesting to see what happens to me because I used to have this elaborate vibration damping setup that was working well.  But since we thought we solved it, I have removed all that, but not yet flown without the damping.

And then there's my new 450 where I wasn't planning much damping either.

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Permalink Reply by Wesley Chuen on May 2, 2012 at 9:06am

I use 3DR telem.

Attachments:

• 2012-04-30 14-01-01 nice sonar.tlog, 737 KB

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DeveloperPermalink Reply by R_Lefebvre on May 2, 2012 at 10:35am

Excellent!

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DeveloperPermalink Reply by R_Lefebvre on May 2, 2012 at 10:55am

Now, I just looked at your other log, and the pitch/pitchin gap doesn't seem as bad as it was before, but it does look like it is "leaning" because I can see you holding more and more pitch.

But on this flight, it looks like it was the pitch is much worse than the roll?

The sonar looks great, other than the huge gap between sonar and baro.  That might be concerning.  It could be a few things.  One, that your APM2 is being blasted with downwash, raising the pressure around the board, and artificially increasing the baro pressure, making it think the alt is low.  That theory fits.

It could also be the baro pressure actually changed while you're flying due to weather.  It happens, but it seems like it happened too fast unless a storm front just rolled in.

You can see that the baro reading dropped through the floor before you even took off, as evidenced by sonar reading flat.  In fact I might even hypothesize that you can see the ground effect, as the baro drops while you are spooling up, and then it rises again, before the sonar starts to rise, which you'd see because of the 20cm deadzone of the sonar.  You might have lifted off, but not above 20cm yet, and ground effect decreased.  Also it seems like whenever the sonar gets close to the ground, the baro drops steeply as ground effect comes into force again.

Does this same effect happen on all your logs?

Normally with APM1's, we placed foam over the sonar to help with this, but that's hard with an APM2.  I'm not even sure you can?  I haven't looked yet.

Also, where you have the APM mounted is much closer to the disk, and closer to the center, than anybody has done before.  The theory works.

Anyway, how did you clean up the sonar signal?  Just the RC filter?

I'll send these files to Tridge.

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Permalink Reply by Wesley Chuen on May 2, 2012 at 11:21am

Yes, I came to the same conclusion for the increased baro reading as well.  They are very consistence among all my logs.

 

The "leaning" problem is in random direction.  Sometimes to the left or right and I have to hold the roll more and more.  Sometimes is the pitch.  And it could change direction during one session of hovering.  That's why I used to call it the random drifting problem.

 

I have a theory that because of the vancinity of the APM2 to the main blades, the constant hovering pushing my APM2 down against the anti-vibration pad and get it to lean.  If I land it or fly around, the pressure on the APM board from the hovering pressure can change to lean to different side/direction.

 

To clean up the sonar signal, I just used a simple RC filter.  However, I still get one or two spike for a 10-15 minutes flight.  I'm adding another bigger capacitor right onto the output rail and see if it makes any more improvement.

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