I am opening this topic to serve as the go-to place for talking about the upcoming 2.9 software release for Trad Helis.  I think this will be necessary as 2.9 will have SIGNIFICANT changes in the way that the helis fly, and also in the settings you will use.

Yesterday, I flew 4 packs of "2.9 - rc2" from the downloads section on my 450 heli.  The file is located here:

http://code.google.com/p/arducopter/downloads/detail?name=ArduCopte...

I would be interested in having some other people try some test flying with this.  I'll have to walk you through the setup, as it requires a bit of work to get a flying parameter setting using the rate controllers which are now active.  You CANNOT fly using the old parameters for Stabilize PID.  Don't even try it.  Also, the Alt_Hold parameters will have significantly changed.

This is slightly complicated by the fact that we have some new Heli-specific Rate PID parameters called "Rate_Pitch_FF", also for Roll and Yaw.  Unfortunately these are only accessible in MP from the Advanced Parameters List.  Hopefully I can get that fixed.  What I'd like to do is for TradHeli, in MP, remove the Rate_Pitch_D, in the Config PID screen, and replace it with Rate_Pitch_FF.  This is because I have found the D-term to be completely unusable anyway.  The FF is feed-forward.  This was what I found was the key to getting the heli to be able to fly in rate mode.  Basically, it is like P-term, but has no error correction.  It's sort of like this:

P-output = P-term x (Rate Input - Current Rate)

FF-output = FF-term x Rate Input

then you also have the I-term output.  So the total servo command is:

Servo-output = P-output + I-output + FF-output

I have also implemented the FF on the yaw controller, and found that it actually helps to stop the slight "tail wag" that we always had.  

There are also some new settings for the collective.  These are Stab_Col_Min and Stab_Col_Max.  What these are for is sort of like Idle-up pitch curves.  You can now set up your swash plate with full negative pitch, maybe a range of -10° to +10°, or +/-12°, but when flying in Stabilize mode, you can set Stab_Col_Min to reduce the amount of negative pitch available to something like -3° or whatever you prefer.  This gives a nice soft feel.  However, in Acro mode, you will get the full range, and also the auto-pilot modes get the full range.  For example, I set my Col_Min and Col_Max to give me +/-10°, and then I set Stab_Col_Min to 40, which is 40%, and this changes the negative pitch to only -2° in Stab mode.

The only thing to know here is that when you change modes between Acro and Stab, the swash-plate will jump up and down, so you have to be ready for it.  It's no different than using Idle-up in your Tx.

My test flights yesterday went quite well.  The Alt_Hold now works beautifully, and I actually prefer landing in Alt_Hold rather than Stabilize!  I also did a few flips with it in Acro mode (very ugly, I'm not good at this) using full negative collective when upsidedown, and it worked well.  It didn't seem to get confused.  Finally, I tried going into Acro, rolling it over upside-down or sideways, then back to Stabilize, and it flipped right way up which is good.

The only problem I have seen so far is that when flying in Alt_Hold, if you push the cyclic full forward and get up a high speed, the altitude starts to oscillate badly.  I suspect this is a classic "phugoid", or pitch/throttle oscillation.  We'll have to work on this. However it seems to fly well up to about 1/2 Vmax.  

I'll try to post my Parameter file here tonight, but I caution that the settings will be HIGHLY dependent on your servo speed, as well as many other setup differences.

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Robert, Randy

I hope I won’t appear impatient or pushy, and I know you are busy, but I would like to test the recommended patched version of 2.9.1, using the gyro rotation rates rotated by the trim values as discussed above, to check if it rectifies this Heli specific problem.

Thanks a lot

Manfred, I don't think anything is available yet.  Looks like nothing has gone into the pre-HAL branch since 2.9.1 went out.

Oh, then I have misunderstood Randy very much, when he said,

“i think the next step is to make a patched version of 2.9.1 that you can upload but which uses the gyro rotation rates rotated by the trim values.

I guess Rob or I will do that..it's just a line or two of code i think within the function to set the rate controller targets.”

I thought it’s just a matter of minutes then hours, to make it happen.

If I knew what line and where, I could do it myself.    

Oh, I missed where he said that.  It does sound like you understood correctly.  Best to take it up with him.  It's not something that I know what to do. 

Thanks Robert

I’ll contact Randy via e-mail about it.

Manfred, Randy and I spoke about this, and basically it comes down to...  you're going to have to be patient on this.  I don't like trying to diagnose by "radio control" and I don't understand the problem, nor have I seen it, and haven't flown in a few weeks so I can't even recreate it.

I've got a few things that I'm working on right now that are taking priority.  Once I get my 450 flying again, I'll be looking for your issue.

I actually smoked a servo on my 450 playing around with a variable voltage power supply trying to figure out this low voltage failsafe stuff.  I think I have a spare.  If not it's going to be a while.  Darn Chinese new year...

,,,and on my side, I most need to focus on the 2.9.2 release with the inertial loiter.  We expect this is going to greatly improve loiter accuracy for everyone and may largely resolve the issue you're talking about...it may not correct the specific issue but it'll likely improve loiter performance so much that it will move much less than it is now.

Robert, Randy
I will be patient, don’t get me wrong on this, I know you are all busy, I only thought I could help to resolve the issue in the meantime regarding the trim, and the yaw swash interaction as discussed.

My configurations files of the TX8

Attachments:

Following Rob's advice I have started reading this whole thread and am up to page 22.  I started getting confused with what I had learnt and to avoid missing something I started writting a manual.  I'd appreicate your thoughts on my progress so far and if you think it worthwhile I will continue to compile it across all 42 pages.

Please let me know what you think.

 

 

Attachments:

Anthony,

    Wow, going through the whole thread huh?  That's dedication.  The manual looks pretty ok so far.

Thanks for your encouragement Randy.  

It's well past midnight here so tomorrow's another day and hopefully I can complete what I've started.  I'll try and incorporate some of the other threads on v2.9.1 and GPS stability.

Looking forward so seeing v2.9.2

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