Development discussion of TauLabs software such as flight controllers, sensors, radios and speed controllers.

Altitude hold refinement

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Danveal

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Re: Altitude hold refinement

by Danveal » Mon Apr 14, 2014 9:27 pm

Hi Peabody
yours is an important statement. In fact this frame generates a lot of vibration and I had to increase gyro tau (0.020) to fly well in attitude mode
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Danveal

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Re: Altitude hold refinement

by Danveal » Tue Apr 15, 2014 7:20 am

Since even the accelerometer acts in height control, it might be useful to include in the GCS a parameter similar to gyrotau / acceltau but only for the z accelerometer ?
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peabody124

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Re: Altitude hold refinement

by peabody124 » Tue Apr 15, 2014 1:28 pm

Essentially there already is. AttidudeSetting.VerticalTau. the problem is baro is already noisy and then if the accel is noisy too the fusion will definitely be noisy. I spent quite some time working on that frame making lots of video analysis and ultimately the vibration must be controlled somewhat in my experience.

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ziad

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Re: Altitude hold refinement

by ziad » Sat Dec 06, 2014 5:49 pm

Hello.
I could finally get AH to work. The issue I amfacing is that my quad is overpowered and hovers at 1/4 stick so I have to move the throttle up to 50% after activating AH. I was concerned about what would happen when I disabled the AH while in flight while the throttle was still at 50%. I tested it while holding the quad, once I disabled AH the throttle went way up and would have flew into the clouds if it were in flight. I can easily adjust the throttle curve from my transmitter to compensate but is there a way to adjust my throttle from GCS so that it hovers near 50% stick and not affect full throttle power? Im guessing a throttle curve like the attached pic?
Thanks so much.

curve.png
curve.png (20.95 KiB) Viewed 5745 times
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pug398

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Re: Altitude hold refinement

by pug398 » Mon Dec 08, 2014 1:27 am

Have a couple with similar problem and I choose to turn the AH climb/descend feature off so I can leave the stick what ever position it hovers at by setting AH max rate to 0.
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ziad

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Re: Altitude hold refinement

by ziad » Thu Dec 11, 2014 3:07 pm

Would be cool to put the current throttle position value in a global variable to be used by AH as a starting value.

BTW Im loving the sparky.
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Oso Grande

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Re: Altitude hold refinement

by Oso Grande » Thu Dec 11, 2014 3:25 pm

ziad wrote:Hello.
I could finally get AH to work. The issue I amfacing is that my quad is overpowered and hovers at 1/4 stick so I have to move the throttle up to 50% after activating AH. I was concerned about what would happen when I disabled the AH while in flight while the throttle was still at 50%. I tested it while holding the quad, once I disabled AH the throttle went way up and would have flew into the clouds if it were in flight. I can easily adjust the throttle curve from my transmitter to compensate but is there a way to adjust my throttle from GCS so that it hovers near 50% stick and not affect full throttle power? Im guessing a throttle curve like the attached pic?
Thanks so much.

curve.png


A throttle curve like that will work for what you're describing. I've got a similar one on a quad that would hover at 30% throttle if the throttle curve was linear.
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CheBuzz

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Re: Altitude hold refinement

by CheBuzz » Sun Dec 21, 2014 3:11 am

ziad wrote:Would be cool to put the current throttle position value in a global variable to be used by AH as a starting value.

BTW Im loving the sparky.


That was considered. The problem becomes that you quickly forget what your starting value was when you enabled AH. It might be different every time. Using 50% throttle, you always know what throttle you need to hover.
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laurent

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Re: Altitude hold refinement

by laurent » Sat Feb 07, 2015 11:40 pm

Hi there,

obviously I'm reading this thread too late.
I'm also playing with quite a powerful quad, it probably hovers at a wee bit less than 30% throttle.

from https://github.com/TauLabs/TauLabs/pull/1119
This also has another implicit change. When using this there is no longer the song and dance to enter vario mode as there was previously. It seemed like not many people liked that. If you do not want to have a vario mode then climb rate can be set to zero and it will never enter that mode. Do we want to make that the default?


imho the most important question is "Do we want to make that the default?"

IOW would it be safe not to have it set to 0 by default ?

This is what happened to me 2 times this year:
- arm, hover at ~30% throttle
- at about 30cm high, engage AltHold
- the quad slowly goes down
- the uav stays on ground, increase throttle
- pretty much my bad human behavior, since I was on ground I should have put my throttle back to 0, I didn't, I switched AltHold off and went to Leveling
=> the uav went AWOL

And it felt like this awful Leave wasn't the most straight one.
not straight as obviously it was quite distressful to see the uav going AWOL, but also it didn't feel like when I intentionally take off with full throttle (attitude felt worst)

I'm in favor of a safe climbrate set to 0 by default. ;-)
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gedsol

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Re: Altitude hold refinement

by gedsol » Sun Mar 08, 2015 11:40 pm

Altitude hold feels really great! If I engage it on the ground, lift off goes very smooth. I can even lift off with throttle to the max and watch it shoot to the sky, then reduce throttle to 50% and hear the propellers almost stop briefly to lock current altitude in a matter of split seconds.
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