erratic yaw

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Vertigo
Posts: 41
Joined: Mon Jul 08, 2013 6:58 pm

erratic yaw

Post by Vertigo »

(crosspost from rcgroups)

When throttling up, the compass and the figurative representation of the quad yaw to the right pretty significantly.
I tied down my quad and hooked up to multiwiiconf to better illustrate the problem:



I also moved the ESC wires as far from the FC as I could for this test. Please note that I fixed the flimsy landing gear to the table, and this causes excessive vibrations because of its flex which allows it move vertically a bit, but then pulls it back down (or forward or sideways) and the FC begins to fight this movement, making it worse and it vibrates pretty badly as a result. It doesnt vibrate anything like that without props or in flight (props are balanced, even the motors I tried to balance). IN flight its relatively smooth except for semi random yaw issues.

In flight, even in acro mode, so without MAG, it yaws to the right upon throttle. Which seems odd, if the FC is getting some misreadings about a right turn upon throttle, like it seems to get in the video, you would expect a counter reaction to the left. But then again, magneto meters arent used in acro mode, are they?

So Im confused. First I dont understand what is causing this misreading when I open the throttle. All I can think of is EM noise, but I cant move the wires any further than that, and Ive tried with 2 different sets of ESCs, the 4-1 Qbrain you see in the video, and more regular SimonK flashed ESCs.

Secondly what the impact would be ( if any) in acro mode without MAG enabled of this misreading and why I am apparently getting an opposite effect?

Any ideas would be appreciated.
Last edited by Vertigo on Tue Jul 16, 2013 8:21 am, edited 1 time in total.

Alexinparis
Posts: 1630
Joined: Wed Jan 19, 2011 9:07 pm

Re: erratic yaw

Post by Alexinparis »

Hi,

The position of ESC is not the only thing to consider.
Power wires position and isolation is something also very important to consider regarding EM perturbation.

You can fly in acro mode safely if you don't activate mag. it's independent.

Vertigo
Posts: 41
Joined: Mon Jul 08, 2013 6:58 pm

Re: erratic yaw

Post by Vertigo »

Alexinparis wrote:Hi,

The position of ESC is not the only thing to consider.
Power wires position and isolation is something also very important to consider regarding EM perturbation.

You can fly in acro mode safely if you don't activate mag. it's independent.


To be clear, Im having the yaw issue in flight in acro mode (as well as in angle mode), with MAG disabled. Its yawing to the right, just like the MAG sensor seems to do when the quad is tied down.

As for EM; besides twisting the high amp wires, what else can I do ?

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clough42
Posts: 70
Joined: Sat Dec 08, 2012 6:10 pm
Location: Boise, Idaho

Re: erratic yaw

Post by clough42 »

EM field density falls off as the square of the distance. Your most effective solution will be to move the mag away from the power system.

I have a DJI 450 with the controller mounted to the power distribution board with nylon standoffs. As you can imagine, this was a disaster for the mag. I solved my problem by desoldering the mag chip from the controller and mounting a mag on a breakout board on a 6" mast on top of the frame.

Desoldering the chip is not difficult, but it requires special tools. (hot air rework station) Some have reported success grinding the chip off with a Dremel.

As for uncommanded yaw with the mag off, you may have something else going on there.

doppler
Posts: 64
Joined: Wed Sep 26, 2012 1:35 pm

Re: erratic yaw

Post by doppler »

Got a picture of your mast? I've been struggling with a "nice" way to do this....

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clough42
Posts: 70
Joined: Sat Dec 08, 2012 6:10 pm
Location: Boise, Idaho

Re: erratic yaw

Post by clough42 »

doppler wrote:Got a picture of your mast? I've been struggling with a "nice" way to do this....


I do. I used a 3D printer to make the platform, cap and mounting bracket. Probably overkill, but I had access to the tools...
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scrat
Posts: 925
Joined: Mon Oct 15, 2012 9:47 am
Location: Slovenia

Re: erratic yaw

Post by scrat »

Beautiful :)

doppler
Posts: 64
Joined: Wed Sep 26, 2012 1:35 pm

Re: erratic yaw

Post by doppler »

Very nice... now back to my waffling, CNC machine (basic one) or 3d printer first....

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