Improving Altitude Hold Performance

[wektorx]

First test of althold with MPXH6115 + ADS1114 + MCP40D18-103 https://picasaweb.google.com/1159846768 ... 3772034674 and new FC https://picasaweb.google.com/1159846768 ... Controller and custom MWC

http://www.youtube.com/watch?v=_VuE-Wkn ... ature=plcp

wektor

[LenzGr]

Good job! Looks promising. I'm waiting for my Sonar (Devantech SRF02) to arrive, so I can toy around with this, too...

[mahowik]

Hi Wektor!

It looks very stable! Could you share your changes for alt-hold?
integrator IMU? own PID regulator? or just more precised baro?

thx-
Alex

[nhadrian]

Hi,

With my mini hexacopter now alt old looks like works perfectly:
http://www.youtube.com/watch?v=CMAQJtvvILM

I have an idea if we should set up some pre-compensation into the altitude hols algorythm depenging on degrees of leaning. I think for example, 1% increase in throttle value for every 1 degree of lean (compared to level). That should be useful for fast forward flying during alt. hold (and later for GPS RTH, etc... when copter is not in level mode.

BR
Adrian

[ankimo]

Hi Adrian

Is it very stable
Is a version DEV_20120121?
Is a PID parameter sharable?

regards
kazz

[nhadrian]

No, I didn't succed with 20120121 since it miss the VEL parameters. For good At hold behaviour you have to syncronize the Accelerometers (VEL) and the barometers (ALT) working.
Now I use the same parameters as EOSBandi (we tested them out together):

ALT P: 2.5, I: 0,023, D: 0
VEL: P: 4,1, I: 0,020, D: 40

I'm on dev20111220 now.

BR
Adrian

[nhadrian]

One thing I have to note is that after I activate the altitude hold, copter slowly climbs 1-1,5 m up and that will be the setpoint. It is independent from the altitude. I couldn't figure out what causes this behaviour, maybe something in the calculations... any idea???

BR
Adrian

[KeesvR]

I have the same result with only Alt I can't get better result as 3 meter.
I go back to Dev 20111220, the best I get with Alt and Vel was 1 meter with also the same PID's, need some more tuning .

[dodecopter]

moin,

i just tested my new quad with all PIDs stock setting, using 1.9, trusted accZ.

flies awesome stable , and even altitude hold works almost fine.

i covered the bmp085 breakout with 5mm foam, and put it into a shrink tube..seems to keep the wind away from baro quite good.


altitude hold works between 0,5 and 1m - not really bad , makes me happy .

but maybe it could be improved.


now the copter doesnt overshoot , and changes altitude slow., kind of "soft"-hovering... almost impossible for me to hold height manually in that calm way... just could be little more accurate, f.e. max 0,5m


need some help there with settings, as i do not know, what ALT and VEL pids do , or which effect this settings have.

which settings in VEL + ALT should i change. to get the height-difference smaller, or make reactions smaller or fasterr?

[Alexinparis]

One thing I have to note is that after I activate the altitude hold, copter slowly climbs 1-1,5 m up and that will be the setpoint. It is independent from the altitude. I couldn't figure out what causes this behaviour, maybe something in the calculations... any idea???

BR
Adrian

Hi,

I think to VEL PID works, but there is still something wrong about the Z velocity estimation.
Without moving, there is a constant non null velocity estimation which I think explains "slowly climbs 1-1,5 m up and that will be the setpoint"
Velocity variation are however well estimated that's why the overall function seems to work.

On the last dev, I removed temporarily the VEL PID because of this.

On the version of today (03/02), I tried to introduce a velocity estimator based on the actual position and refreshed every 0.5s
This velocity is used to decreased the overall throttle correction.
This way, it prevents any over amplification and growing oscillation problem. The throttle correction is just lowered when the Z velocity increases.
This can be tuned via ALT D Term.

Could someone tests the last dev ALT HOLD function with default PID ?
It works fine in my living room with MS baro and BMA180 ACC. (1 meter range)