MultiWii 2.2 Alt hold shoots up while flying

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Vaattari
Posts: 14
Joined: Tue Mar 27, 2012 8:17 am

MultiWii 2.2 Alt hold shoots up while flying

Post by Vaattari »

I upgraded to MW2.2 with great results with my middle size Hexa. PIDs are tuned OK. Everything seems a little more smoother and better than MW2.1, however Altitude hold is having some issues.
While the hex is hovering in Angle mode and I activate the Altitude hold, it's staying in about +/- 20cm area in calm no wind weather and around 0.5m when windy.
When I try to fly while Altitude hold is active (not moving yaw or throttle) the copter shoots up after I return the pitch/roll back to center. It will descent to the original hover altitude but why does it shoots up?
PID for hover is excellent but what PID value to tune to get the flying altitude stable as it is in hover?
With Angle mode there is no problems to fly around but altitude hold would be nice extra : 8-)

Thanks,
janne

Electro 2
Posts: 27
Joined: Tue Mar 19, 2013 4:05 am

Re: MultiWii 2.2 Alt hold shoots up while flying

Post by Electro 2 »

Is this *only* with Alti-hold engaged, or any time you get off the sticks ??? If it's only with hold, I'd guess PIDs for A.H. may need twiddling, at least I'd try that first. I'm aware that one is supposed to only activate alti-hold after reaching the desired hover point, but I have left it latched on right off the ground numerous times and it doesn't seem to hurt anything.

Vaattari
Posts: 14
Joined: Tue Mar 27, 2012 8:17 am

Re: MultiWii 2.2 Alt hold shoots up while flying

Post by Vaattari »

Problem is only when Alt hold is active and I fly with fixed altitude. Small correction to previous post is that the copter will increase the altitude after couple of seconds while flying fast forward as well. While I fly slowly forward the altidude increases only when I release the roll/pitch stick. But the speed in that case is really slow.
While only hovering the altitude hold is OK. While flying/hovering in Angle mode, no problems.
Alt hold P & D are tuned and if I change them from the current values the slow yoyo starts. I'm not sure about the I, which is small at the moment and I did not see any difference when I increased I-term.
Should I focus on ACCz filter values or Angle mode PID instead?

I would like to use Alt hold to get FPV more easyer as there is no need to change altitude. Hovering in one position is boring..

Thanks,
janne

Electro 2
Posts: 27
Joined: Tue Mar 19, 2013 4:05 am

Re: MultiWii 2.2 Alt hold shoots up while flying

Post by Electro 2 »

OK, understood. Just on a hunch, reduce derivative ("D") for "Level" from 100, (stock), to 80, and see what it does.

Vaattari
Posts: 14
Joined: Tue Mar 27, 2012 8:17 am

Re: MultiWii 2.2 Alt hold shoots up while flying

Post by Vaattari »

Level D-term was 85 all the time. I have tried 70, 80 and 100. Only thing is that with 100 the level mode is like flying with very slow response. Everything under 100 will make the Level mode to work as it was before MW2.1.
I do not see any change to ALTitude hold issue.
By the way, the same issue was seen also with smaller 35size quad. However it does not shoot up everytime or the altitude change is smaller.
Maybe the Altitude hold should take into account the pitch/roll changes to limit quick throttle change as MW does not take into account the ACC x or y? :roll:

Thanks,
janne

evvaldis
Posts: 1
Joined: Wed Mar 05, 2014 3:03 pm

Re: MultiWii 2.2 Alt hold shoots up while flying

Post by evvaldis »

Hello, I have very similar problem.
I have MS5611 baro installed on mwc, software is v2.3.
In stable hover barometer works pretty well, but when I start to fly forward, or especially make turn with yaw, copter starts to go down (or up) more than +-2-3meters.
I am wondering is it PID's or software issue, and ALTHOLD works just in stable hover, or something else?

What is your experience with flying when altitude hold is ON?

Thanks

scrat
Posts: 925
Joined: Mon Oct 15, 2012 9:47 am
Location: Slovenia

Re: MultiWii 2.2 Alt hold shoots up while flying

Post by scrat »

Set throttle angle correction in config.h.

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