when takeoff, can't hold the heading

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when takeoff, can't hold the heading

Postby EX_TRUE » Sat Apr 11, 2015 6:21 am

I have build QUAD 450 in X mode
propeller 10*47
motor sunny sky V2216-12 800KV
battery 3S 4400mah.

1. When AQ takeoff, it didn't hold the heading.
Instead it would first rotate, then back to the Heading preset on the ground.
This would happen,no matter on ALT hold or Postion hold mode.

2. When AQ move forward after or right left,it descend and then ascend.
Is it mean, it in a bad altitude hold.
By the way,I have put a black foam on barometer.

3. The AQ'attitude control still exsit a little unstable,
especially when a gust wind come, it can't keep the attitude.
Attachments
heading.jpg
heading.jpg (38.01 KiB) Viewed 5417 times
EX_TRUE
 
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Re: when takeoff, can't hold the heading

Postby EX_TRUE » Sat Apr 11, 2015 6:36 am

My PIDs

Tilt Rate
D 7000 F 0.25
Tilt Angle
P 70
I 0.004
D 5500
F 0.25
Yaw Rate PID
P 1445 I 0.725 D 240 F 0.25
Yaw Angle
P 0.05 I 2e-05
Nav Alt Speed
P 130 I 1
Nav Alt Pos
P 0.18 I 0

the attachament is my ACC LOG.

Thanks
Attachments
ACC.jpg
EX_TRUE
 
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Re: when takeoff, can't hold the heading

Postby chschmid » Sat Apr 11, 2015 8:47 pm

You have a lot of vibs.
You ACC values should be close to 1. Yours are close to 10.
Check your props for balancing.

Cheers
Christof
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Re: when takeoff, can't hold the heading

Postby EX_TRUE » Sun Apr 12, 2015 6:39 am

Thanks for reply.

ACC valuse where above 5 can be AQ respond to the pitch command.

I have balance the pro and motor, also I have put a 3M foam rubber between AQ and Airframe.

if there any suggestion, vibration is really an issue. :D
EX_TRUE
 
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Re: when takeoff, can't hold the heading

Postby plexus » Sun Apr 12, 2015 9:14 am

Hi
If yours motors and prop are well balanced, the vib may coming from the center plate and arms. But see too the value of the tilt rate D if it is too high.
Can you give a photo of your bird ?
I see you have 7000. What your version of QGC?. You have an old version and not the 1.6.3.
Alain
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Re: when takeoff, can't hold the heading

Postby chschmid » Sun Apr 12, 2015 6:58 pm

EX_TRUE wrote:Thanks for reply.

ACC valuse where above 5 can be AQ respond to the pitch command.

I have balance the pro and motor, also I have put a 3M foam rubber between AQ and Airframe.

if there any suggestion, vibration is really an issue. :D


Try to remove the 3M foam and put the AQ board on short nylon standoffs.

Cheers
Christof
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Re: when takeoff, can't hold the heading

Postby Max » Sun Apr 12, 2015 7:45 pm

EX_TRUE wrote:I have build QUAD 450

If that means one of those plastic "flame wheel" frames, it won't work, they're way too floppy (flexible).

#1 advice for AutoQuad is to use very stiff frame and arms. It's not always that simple, but in general AQ doesn't like flexible frames at all. Do not mount the flight controller on shock absorbing devices (or foam), that usually makes it worse as well.

-Max
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Re: when takeoff, can't hold the heading

Postby EX_TRUE » Mon Apr 13, 2015 8:23 am

chschmid wrote:
Try to remove the 3M foam and put the AQ board on short nylon standoffs.

Cheers
Christof


Many thanks, I will give it a try. :lol:
EX_TRUE
 
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Re: when takeoff, can't hold the heading

Postby EX_TRUE » Mon Apr 13, 2015 8:35 am

Max wrote:If that means one of those plastic "flame wheel" frames, it won't work, they're way too floppy (flexible).

#1 advice for AutoQuad is to use very stiff frame and arms. It's not always that simple, but in general AQ doesn't like flexible frames at all. Do not mount the flight controller on shock absorbing devices (or foam), that usually makes it worse as well.

-Max


1. It's not the plastic flame wheel, but a carbon fiber frame, later I will post the frame.

2. Accelerometer is sensitive to vibration. So we need to take measures including software and hardware.
The software such as a window average filter, but it can't solve the problem alone.
In general, damper or foam would be used to isolate the vibs. That's why I mount AQ on foam.
Why the vibration damper don't suitable for AQ :)

Thanks.
EX_TRUE
 
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Joined: Mon Nov 10, 2014 8:57 am

Re: when takeoff, can't hold the heading

Postby chschmid » Mon Apr 13, 2015 8:41 am

EX_TRUE wrote:2. Accelerometer is sensitive to vibration. So we need to take measures including software and hardware.


That's what the FC is doing. Measuring the ACC.

EX_TRUE wrote:In general, damper or foam would be used to isolate the vibs.


Or the foam amplifies the vibs depending on the frequencies of the vibs and the material.
We just found out by trial and error that not dampened mounts work better in most cases.

Cheers
Christof
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