Replies to This Discussion

Permalink Reply by Paul Emous on June 22, 2012 at 2:35am

Hey James,

I have no ambition to compile firmware as I lack experience with this.

It could be because I am flying on a less fresh battery, but I have a feeling putting THR_MAX = 600 does not let the drone sky rocket as it did before when the setting was on THR_MAX = 1000.

Nevertheless I just had to use a ladder and climb into a ridiculous high tree because my drone got stuck... (:

It is a bit strange though. I am a new flyer and learning alot but I never experienced so much struggle when trying to control the drone.

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Wiki NinjaPermalink Reply by Gary McCray on June 24, 2012 at 5:59pm

Just a thought Paul,

You might want to look at the appendix in the Arducopter Wiki, they have a pretty complete walk through on how to bring up the relaxed version of Arduino and to compile Arducopter.

I was up and operating in under an hour.

Without the help this would have taken MUCH longer.

I just looked at the config.h file and it MINIMUM_THROTTLE is defined as 200 on line 444.

I have a similar problem to yours and am going to try reducing this value myself. (like to 0).

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Permalink Reply by Paul Emous on June 25, 2012 at 12:00am

How did it work out for you? What quad config you have?

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Permalink Reply by Klaus Heinrich on June 22, 2012 at 8:35am

Hello

I always have the latest firmware V 2.6 Arducopter Octa V
on the APM two charged and has repeatedly version V 2.6 octa X.
All engines have been tested individually, it is the version octa X.

Doing something wrong or is there a software / programming error?

Big thanks for quick help

Klaus -Germany-

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Permalink Reply by Jonathan M on June 22, 2012 at 10:38am

I have quite a bit more successful flights with my heavy hexa using V2.6.  Stabilize is awesome.   However, I am still getting some wobbles on faster descents.  Anyone having success tuning that out?  I know it's a difficult issue due to descending in your own prop wash.

My thought is that it's more of a stab_P/D parameter adjustment since it's trying to hold it's level while descending.  Though I am sure it's a combo of rate and stab parameters.  It's curious to me that v2.6 stock PIDs no longer have any stab_D component, when we used to have .15 or .12. 

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Permalink Reply by Rui Manuel Cravo Marques on June 22, 2012 at 10:47am

Hello Jonathan, you may try to raise a bit more your RATE P and see if that helps. I have a smal hexa (Xaircraft X550 pro) with 10" props and I have descents without any noticeable wobble. I don't understand your sentence about STAB_D, since mine by default was at 0.1 in version 2.6 with a scaling parameter of 0.5.

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Permalink Reply by Jonathan M on June 22, 2012 at 11:16am

Really?  Yup, the stock parameters had Stab_D = 0 for me.  Rate_D = 0.004

I will up the rates a bit more, but I am close to the point where I get wobbles due to overactive gains.  Do you mind sharing your param file?  Thanks!

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DeveloperPermalink Reply by Randy on June 22, 2012 at 11:35am

I guess it depends on the degree of the wobbles during descent...but I think it's pretty normal for that to happen (it happens with my quad anyway) just because the heli is going through it's own wash as it descends.  That air is much more turbulent than the copter moves through when hovering or climbing.

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Permalink Reply by Jonathan M on June 22, 2012 at 1:52pm

It's definitely a corner case for the FC.  Very turblent, swirling flow with a velocity to it.  Not easy to stabilize.  From what I have read about other controllers, they generally handle it pretty well (DJI, etc).  So, I am assuming that the APM can be tuned to handle that as well.  I am sure it's function of disk loading and prop size with smaller props handling it better because they can react more quickly.  I really like my 12x3.8SFs though because of my expected payload weight

I will keep playing with it.

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Permalink Reply by Rui Manuel Cravo Marques on June 22, 2012 at 1:57pm

it depends on the space between the downwash columns of air, if the props are too big the turbulence underneath will be much higher, I've tested my quad with 12" and 10" props and there was a huge difference in behaviour, however in my hexa, the props are very close to each other and I can get quick descents with almost no wobble, I believe you are correct and the smaller props demand less torque for faster responses, compensating much faster and preventing the effect.

 

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Permalink Reply by Bruce Jones on June 22, 2012 at 2:26pm

It also depends on the distance between props.  I've had my tricopter set up with arms ranging from 20-40cm long.  Descents are definitely more stable with the longer arms.  But there are other problems on my tri with the longer arms.  I've settled on them being about 40cm and I'm still able to descend pretty well.

I also have a little Quadrixette 40 that has a 40cm mtm distance and I've never been able to get it super steady when descending.  I've tried props from 8", 9", and 10" props and all kinds of PID settings and can't get it to descend stably.

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Wiki NinjaPermalink Reply by Gary McCray on June 22, 2012 at 5:24pm

My KK came with 3 bladed 9" props and it did descend rapidly more stably with those than the 11" x 4.7 GemFan 2 bladed ones I have on it now.

Among other things the 3 blade smaller diameter prop represents a more symmetrical aerodynamic load at each motor than the slowly turning 2 blade ones.

You can also hear the noisy chop of stalled blades when you are descending rapidly and that is always a source of asymmetric turbulence and loading. (and also compromises the APM's ability to stabilize).

That having been said I wouldnt go back to the 3 bladed ones for anything.

The GemFans use considerably less power, have higher performance and are much quieter (at least when you aren't descending so fast that they are stalled.)

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