Overshoot in RTH

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Re: Overshoot in RTH

Postby plexus » Tue Mar 05, 2013 11:24 am

Solved with tilt angle P=20
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Re: Overshoot in RTH

Postby LPR » Tue Mar 05, 2013 3:55 pm

The only reason I can think of that you would need a P setting that low is that your motor mix is not a normal mix.

Larry
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Re: Overshoot in RTH

Postby plexus » Tue Mar 05, 2013 5:47 pm

Hi Larry,
I am using this one and it seems to run well. But ???


[i]Postby plexus » Thu Dec 13, 2012 11:20 pm
I use the mixing table of teramax with front left CW. No wobble.
---------------throttle---pitch---roll-----yaw
front left----100--------50------100---- -100
front---------100-------100--------0------100
front right--100--------50----- -100--- -100
rear left-----100------ -50-------100------100
rear----------100----- -100--------0---- -100
rear right---100------ -50----- -100------100
[/i]
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Re: Overshoot in RTH

Postby LPR » Wed Mar 06, 2013 1:37 am

That is what I thought. With your motor mix you need to have a lower tilt angle P than default. I'm not sure if other PIDs would have to be adjusted to get all functions to work properly.

If you want to use default PIDs pitch and roll numbers would need to add up to 100 or less.
So to have the same proportional motor mix you could use 33 and 66 instead of 50 and 100.

Then increase the Tilt angle P to default 60.

On the three AQ copters I've built I used defaults, except for Tilt Rate D. I like to lower D till I get some osculations while hovering and then raise slowly till the osculation stop and then try RTH.

Your current settings are working but I would think your hex would be a little slower moving than it should be.

Larry
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Re: Overshoot in RTH

Postby plexus » Wed Mar 06, 2013 11:32 am

Hi Larry,
I changed my mixing table by 33 and 66 instead 50/100. All parameters are default. Tilt angle P=60
It fly very well and the RTH too. No overshoot now.
Now, but it's rain, i must lower the Rate D to see the action. As you say.
Many thanks for your help.
alain.
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Re: Overshoot in RTH

Postby LPR » Wed Mar 06, 2013 2:02 pm

Alain

The only reason to lower Tilt Rate D is to get RTH to work with no overshoot. The higher the D value is the more stable your hexa will be. Lowering D just allows the hexa to tilt faster so it can stop on home.

With my copters I've always had to lower D some because occasionally but not every time I would see overshoot.

Larry
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Re: Overshoot in RTH

Postby plexus » Thu Mar 07, 2013 1:06 pm

Hi Larry,
Today some flight with different Tilt rate D. Begin at 7140 and the lower was 4000. At 4000 it begin to oscillate in Roll and pitch when the stick come back to center, But it is a very small oscillation.
In RTH it was always very good. I am with all default parameters.
An other difficulty I have is the stability of Hold position. It is very critical and I have a lot of difficulties to find the good point. I hover at 700 and i dont understand.
An idea Larry ?
Screenshot - 07_03_2013 , 13_12_02.jpg

Screenshot - 07_03_2013 , 13_11_46.jpg

Screenshot - 07_03_2013 , 13_11_08.jpg
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Re: Overshoot in RTH

Postby LPR » Thu Mar 07, 2013 2:03 pm

plexus

I use as high a Tilt Rate D setting that gives good RTH. The higher the D setting the more stable in wind your hexa should be.
To get the throttle stick centered or at 700 and stay in the 40 deahdband spot is not easy unless you do that I have done to all three Tx that I use to control an AQ copter. I uses parts out of old Tx to make the throttle stick spring back to center. So all you have to do to get good position hold is to let the throttle stick spring to center position.

If you plan to used the Tx only on the AQ copter then I think it's worth the effort.

I have been playing with the navi altitude position P, I, IM and OM to get better altitude hold and I don't have an answer yet. Start with foam on the barometer.

Larry
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