PID for Hoverthings Flip FPV quad (rectangle)

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PID for Hoverthings Flip FPV quad (rectangle)

Postby arachnida » Sun Apr 21, 2013 12:40 pm

Does anyone have good PID values to compare for this kind of frame, or any other rectangular frame? The motor positions on this frame are not in a square, but in a rectangle of 28x37 cm.

I have a wobble in pitch direction, not in roll. Also making flips in that direction when releasing the stick fast after a forward flight like mentioned in another thread in this forum.
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Re: PID for Hoverthings Flip FPV quad (rectangle)

Postby Max » Sun Apr 21, 2013 8:14 pm

What mix table are you using?

This is an excellent example of what the mix table is really good for (IMHO :) )... since we only have one set of PID setting for roll & pitch, we can use the mix to balance the power to each axis. A rectangle quad will have a lot more pitch authority than roll, since the motors are further out from center on that axis. So you would want to reduce output to those motors for the pitch control. I'd have to draw it out and do the math to tell you the exact numbers... Basically need to determine the percentage by which the distance from center varies on the 2 axes. Does that make sense?

-Max
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Re: PID for Hoverthings Flip FPV quad (rectangle)

Postby arachnida » Mon Apr 22, 2013 8:13 pm

I'm using the normal X mix table.

What you're saying does make sense as there is no separate PID control for roll and pitch. But what I don't understand is how to adjust rate when one can't fly in rate, stabilized is the only flight mode available. I'm used to fly OP CC and CC3D for years where these settings are easier to adjust TMHO. There I would start adjusting rate until my qaud keeps nice the angle set by the sticks and then move on to adjust the stabilized PID settings. I'm a bit lost here.

Today I did a test with the quad fixed on a bar that can only move in the pitch direction. But then I don't see the wobble effect. Strange!
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Re: PID for Hoverthings Flip FPV quad (rectangle)

Postby LPR » Tue Apr 23, 2013 1:36 am

Arachni

I had three CC quads and octos. I tried to do the same as you adjusting the PID for rate. All I got for my efforts is a bunch of broken props. None of the four flight controllers I've used have been like the AQ. Default values give just about any craft great performance. The only PID I've found that needs adjusting is tilt rate D.
Your rectangle frame problem should be fixed by adjusting your motor mix.
If you give more information like a picture and your motor mix I could give you a motor mix to try.

Larry
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Re: PID for Hoverthings Flip FPV quad (rectangle)

Postby arachnida » Tue Apr 23, 2013 12:27 pm

Here is some more info about my setup:

Frame: HT Flip FPV
Motors: Robbe Roxxy 2824-34
Props: 9" x 4.7" GemFan
Android Nexus 7 link: 3DR 433 MHz
ESC: FlyDuino NFET 20A SimonK

Mixer:
[Throttle]
Motor1=100
Motor3=100
Motor7=100
Motor10=100


[Pitch]
Motor1=-50
Motor3=50
Motor7=-50
Motor10=50

[Roll]
Motor1=50
Motor3=50
Motor7=-50
Motor10=-50

[Yaw]
Motor1=100
Motor3=-100
Motor7=-100
Motor10=100
Attachments
HT Flip FPV dimensions.jpeg
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Re: PID for Hoverthings Flip FPV quad (rectangle)

Postby arachnida » Tue Apr 23, 2013 6:33 pm

Some more strange behaviour: https://dl.dropboxusercontent.com/u/974 ... st%202.mp4

After a few forward and backward tilting the quad doesn't come flat anymore, I could a strange motor spinning sound.

Right when I want to touch the sticks the copter moves back horizontal.

Stupid me, I didn't have a SD card in de FC. Will try again tomorrow, this time with a SD card inserted!
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Re: PID for Hoverthings Flip FPV quad (rectangle)

Postby LPR » Tue Apr 23, 2013 7:52 pm

arachnida

This mix should give you the same control for pitch and roll. If your still having osculation with default PID settings you most likely have too much vibration getting to the AQ board.

If your quad does not have any osculation then the only PID your likely to need to change is the tilt rate D. Lowering D will let the quad tilt faster and not over shoot the point it should stop at in Altitude/ position Hold and RTH. Lowering D too much will cause osculations. The lowest D setting I've seen people use is 4500.

Mixer:
[Throttle]
Motor1=100
Motor3=100
Motor7=100
Motor10=100


[Pitch]
Motor1=-57
Motor3=57
Motor7=-57
Motor10=57

[Roll]
Motor1=43
Motor3=43
Motor7=-43
Motor10=-43

[Yaw]
Motor1=100
Motor3=-100
Motor7=-100
Motor10=100

Hope the mix works for you.

Larry
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Re: PID for Hoverthings Flip FPV quad (rectangle)

Postby arachnida » Tue Apr 23, 2013 8:23 pm

Thanks Larry!

I will try this out tomorrow, but I believe I also have another problem. Did you see the video I posted? Unfortunately I didn't have a SD card in the AQ, will do the very same test again with a card inserted. Looks like the ACC being shifted for a few seconds. All my ESC cables have ferrite rings on the datat cable so I don't suspect them.

Cheers,
Ivo
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Re: PID for Hoverthings Flip FPV quad (rectangle)

Postby LPR » Tue Apr 23, 2013 10:40 pm

arachnida

You'll find that the AQ has a mind of it's own. Because of it's use of accelerometers and smoothing the AQ copter just doesn't like to be tied down. I would expect your quad to fly well.

Larry
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Re: PID for Hoverthings Flip FPV quad (rectangle)

Postby arachnida » Thu Apr 25, 2013 10:03 am

Larry,

looking at the logs (LOG MOT YAW) it seems that the quad suddenly want to make a YAW, but because of the fixation it obviously can't do that. You are right, the AQ is not into SM, doesn't like to be tied. The weather is changing over here so I'm not able to test your mixer yet. Will get back to you with the results.


Ivo
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