daveapplemotors

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Some directions for setting up a CP helicopter with Libre Pilot.

Neither TX Wizard nor Vehicle Setup Wizard works for me so this is how I do things.   

++Software download & install http://opwiki.readthedocs.io/en/latest/user_manual/gcs_install.html ++
Use another UAV file to get started. Examples here:  https://forum.librepilot.org/index.php?topic=557.0

Setup:
++plug in servos and radio ++ http://opwiki.readthedocs.io/en/latest/user_manual/cc3d/cc3d.html++

Board Orientation – Configuration / Attitude
     set board level

Setup TX to get at as many flight modes as possible (DX6, DX7, DX7S and DX8 can get 6 flight modes)
++ http://www.rcgroups.com/forums/showthread.php?t=1967153&page=995] ++

Calibrate TX  – Configuration / Input / Manual Calibration
++ TX defaults (no expo or Dual Rate, default throttle and pitch curves, no tail mix) ++
Move the sticks straight when calibrating. DO NOT add Yaw when moving throttle. DO NOT add any Roll when moving stick for Pitch. And DO NOT add Pitch when doing roll. And flip the flight mode switches during calibration to show LP. After Manual Calibration reset throttle neutral to just a couple of points higher than minimum to avoid swash jitters.

Setup servo , and ESC frequencies on Configuration / Output. I use 50 on all servos and ESC. If you use higher numbers check for buzzing or heat from a servo. 

Change Manual Rates to at least 540 degree / second and Maximum somewhat higher. This is in Configuration / Stabilization (near the top of the page). Do this to see servos move since they don’t move much at the default, 220.

Configuration / Vehicle ++Get servos to move++ You must “Jerry Save” (save with 140 degree swash and then save again immediately 120 degree swash) if you make any changes on Configuration / Vehicle page otherwise the servos won’t move. Be sure that "Curve2" source is collective. "Curve1" is throttle. 

Arming: don’t use Always Armed (dangerous) or Always Disarmed (nearly useless). Instead use any other combination because the Swash Leveling routine sets it to Always Disarmed if your heli is armed when you start.

Two ways to Level Swash (I use the second):
     1  Swash Level routine in Configuration / Vehicle needs “Jerry Save” otherwise servos go dead. This routine moves the swash quickly to limits of 1,000 and 2,000 so be careful. Do this with servo push rods disconnected at first to avoid damage.     

2  Use System /  Settings / Actuator Settings – channel neutral, minimum and maximum. Adjust Channels ',[0],  [1], and [2]'. And '[channel 0]' is the rear on my 250s. If a servo is alone then it is '[channel 0]'.   Make the swash move smoothly fully up and down.  Start conservatively at say 1350 and 1800 to begin.  Save your work via the red arrow at top of the page.
    Set swash level values
    Set limits and set level at limits. Get the maximum pitch you prefer.
*Be careful not to wreck a lipo here. Without running the motor there is no LVC to tell you when to charge.

Tail:  set conservative limits to begin, set neutral to 1522 and have arm at right angle. Approach the limits carefully to avoid damage. THEN set up helicopter mechanically to hover there. Ideal world! Your setup can have any adjustment that works.

Orientation: if the swash servos and tail servo all react in the correct directions go on to Tuning. When you tip your heli forward (Pitch) the swash should tip back. I put my finger under the servo ball so that I can feel it at the beginning of the tip. Likewise I put my finger between the main gear and a front servo arm to feel the reaction when I tip the heli sideways (Roll) .

If the the Roll or Pitch reaction is reversed then change board orientation in Configuration / Attitude . Also check that the aileron servos are connected properly.

If Yaw reaction is backwards but tail servo moves correctly with TX then merely change the TX yaw direction AND Yaw in Configuration / Output – checkbox to reverse.

Set headspeed low to begin with. PID number will be larger smaller for higher headspeeds.

Tuning:

I recommend using Rate (Roll),Rate (Pitch) , AxisLock (Yaw)  to tune.  Use Configuration / Input /Flight Mode Settings  set up three flight modes that use Rate, Rate, AxisLock each : one with Settings Bank 1 another with Settings Bank 2 and another with Settings Bank 3 . You can change flight modes and thus PIDs midflight or land to flip the switch. [EDIT] recently I found little difference between Rate and AxisLock on the tail. I prefer Rate so far. And I am playing with the AxisLock parameter, AxisLockKp, to get it to feel more like Rate. 

Use Configuration / Stabilization / Advanced to tune. Use all three Settings Banks.
Start with some PID numbers from someone’s UAV. Set Settings Bank 2 slightly higher than Settings Bank 1 and Settings Bank 3 slightly higher than Settings Bank 2.

Test hover:
    Does it roll left or right or pitch  back or forward on liftoff? Adjust swash and / or board level.   
    Does it Yaw? Change the yaw physically with push rod or servo placement and readjust endpoints. This keeps servo arm at 90 degree and servo centered at 1522. Fanatic? Yes but I think this is the very best way. Correct me if I am off. Please?

My last tuning session Configuration / Stabilization went like this:
FM (flight mode) 3 = way too pitchy—it oscillates fore and aft--, roll and tail mushy
FM 1 = way too pitchy, R and  Y mushier
didn’t bother trying FM 2
Land, Made Settings Bank 1==Settings Bank 3 and reduced the pitch P from .00390 down to .00240
made Settings Bank 2 slightly larger at .00250 and Bank 3 at .00260. (I know the default P is double I but my I numbers are a little more than ½ P on each axis.)
Flew again. Still too pitchy and mushy on R and Y
Put the largest GOOD known PI numbers into Bank 1 , larger yet in Bank 2 and larger in Bank 3.
Flew again, adjust, etc.
I crept up on the Roll and Yaw and lowered the Pitch until it was sweet.

5 or 6 packs and 4 test flights per pack with 3 flight modes on each test flight allowed at least 60 different sets of PID numbers for comparison.   
  Outer Loop is default for now. Tests in strong wind might change that.
  Result is a really crisp handling 250 heli. 1628Amarillo.uav posted on the UAV page.

I save (and export to hard drive) my current UAV file with a name that starts with the date: "0514Blackie.uav"- for May 14.

Another tuning session:
Refine the PIDs get 3 significant figures PIDs. Once I settled on a P number (3 decimal places) that I liked I tried changing "I" until it 'felt' good. For instance with P at .00368 on all three Settings Banks I tried 0.00183, 0.00185 and 0;00187 and later 0.00184 0.00185 and .00186.   

If you put your favorite PI numbers into System / StabilizationSettings / VbarRollPI, PitchPI and YawPI then Vbar will fly pretty well. Change VbarTau if you want to see some differences there.

Anyone else have an idea for this page? Let us know, please?

I hope this helps.



« Last Edit: June 01, 2016, 02:19:48 pm by daveapplemotors »
Happy Landings!

tuor

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Re: A simple guide to get started with a CP helicopter
« Reply #1 on: May 13, 2016, 07:10:07 am »
Nice one here, maybe you can get it more beginners accessible? I think in some passages your level is way to high for a beginner to start with LP-Helis.

daveapplemotors

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Re: A simple guide to get started with a CP helicopter
« Reply #2 on: May 13, 2016, 12:21:28 pm »
Thanks, I know that it assumes some knowledge of setup. I will add to it to make it easier.

Any thing that you want me try to make more clear? I will try...

Questions? Suggestions?   

 
Happy Landings!

karla

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Dave, keep it up!
This is very good as is. It does help :)
Its a high level summary of the steps you need to do to get any Helicopter fly with LP/OP with current software. So I understand new to this will just lose it. Really.
Anyway, pictures with more detailed descriptions to beef it up will help (but will also make it a lot longer).
What I right now found really useful was your experience on how you make the incremental changes of PIDs when tuning.
Not too large and not too small. I used too large increments (life is short like to take short cuts). Using your example works better in the field.
When Tuning I know you like to use Rate, Rate, AxisLock for Pitch, Roll, Yaw.
I don't :) No worries.
I use Vbar, Attitude and Rate flight modes together (Bank 1 for Vbar, Bank 2 for Rate, Bank 3 for Attitude) to get understanding of the particular helicopter. But in doing this using your incremental value changes works better for me.
Thanks a lot :)

My current project to turn a Trex 450L dominator in to a FPV and filming platform is a challenge to tune, i think mostly due to the heavy weight ;D

daveapplemotors

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It might make Vbar easier to use if you reset the default Vbar PI numbers to equal Rate numbers. Immediately following are defaults:
            <field values="0.005,0.002" name="VbarRollPI"/>
            <field values="0.005,0.002" name="VbarPitchPI"/>
            <field values="0.005,0.002" name="VbarYawPI"/>

And these are numbers (from a 250 CP helicopter) that I use when I get to Vbar mode:
              <field values="0.0033,0.0018" name="VbarRollPI"/>
            <field values="0.003,0.00175" name="VbarPitchPI"/>
            <field values="0.00308,0.0148" name="VbarYawPI"/>
         
Thanks for the suggestions, good people.
Happy Landings!

karla

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Thanks Dave,
Yes actually I do set the PID values very similar for all flight modes (Vbar|Rate|Atti) while tuning.
I do it to compare what is cause and effect, is the behaviour due to PID setting changes or to Flight mode logic.
. Vbar- closest feel to old flybar helicopter flights
. Rate- hard but best 'grip'
. Attitude- easiest with most support once locked in
Comparing test flights works faster for me to arrive at reasonable PIDs for all modes. There are so many variables working on the final flight behaviour like responsiveness and outer loop. I found it easier this way. Also I only use P values and zero out the I and Ds until its working well and then add them on.
Your guide works fine I think. Just sharing this for reference.

By the way, have you ever seen a TROUBLE SHOOTING GUIDE for a LP/OP controlled Helicopters?
Just for most common flight issues: Problem | Cause(s) | Solution(s)
Maybe something to add on at end of the guide?

Hello Dave,

I am following your settings and have a question.

In the swash setting, I set servos limits to get the pitch to +10/-10 degrees already and calibrated the transmitter.

After all done, when I move the throttle stick max up and down I cannot get +10/-10 degree pitch but only +6/-4 degree, how to fix this ?

Edited: I've found your answer here https://forum.librepilot.org/index.php?topic=1412.msg11173#msg11173.
Follow that and now I can get +12/-12 degree hope to airborn tomorrow.
« Last Edit: May 27, 2016, 12:25:15 pm by Airwolf »

Opps

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Great info. My two cents is i use one flight mode in the 3 banks to tune the pids. So you understand its the pids that is changing the feel of the way your craft is flying not vbar or rates or altitude  or manual flight mode that your getting confused about.