AQ Motor outputs show large swing (and clipping)

[johandm_be]

Hi,

We are trying to set up an X650 frame with AutoQuad.
The frame is a quad-X configuration.
We're using ESC32, and the motors are 2217 (880Kv). The props are 13x4.
For the craft to hover, we have to hold throttle at about 40%.

The AQ is running firmware 6.6.1
This our first attempt to setup an AutoQuad - we have worked with other controllers in the past.

Initially, the copter was very unstable in manual mode.
After experimenting with the PIDs, we did get it better. It flies OK now in manual mode; but (just for the sake of comparison) not quite as good as a DJI Naza in manual mode.

We changed the following PIDs from their defaults:

Tilt Rate D 5200 (default was 7180)
Tilt Angle P 20 (default was 60)
Tilt Angle D 1300 (default was 1744)


While reviewing the logs, we noticed that the motor outputs are always clipped. See the included screenshot.
Is my understanding correct that this is something we still need to fix using the PIDs? Or could there be another cause for that?
If it is the PIDs, which parameter(s) should we focus on in this case?

The troubleshooting Attitude PID in the AQ online manual suggests "Put I and D terms to zero. Start tuning your P alone, and then move to I, and then to D.", but if we do that then it is completely uncontrollable. I get the impression it cannot fly at all with Tilt Rate D = 0.

We'd appreciate all the help we can get.

Kind regards,
Johan.

[LPR]

Johan

Your problem is very common. You need to balance the props carefully and you still may have vibration issues if you frame is not ridged enough.

When the vibrations are small enough you will be able to fly very well with the default settings if your parameter file is good. Lowering Tilt rate D is needed sometimes.

Have you set the throttle factor so your quad will hover at 50% throttle?

Larry

[johandm_be]

Hi Larry,

Thank you for your help.

We did balance the props very carefully (both horizontal and vertical).

So, you think our problem is likely more due to vibrations than to PIDs at this point?

I have not yet set the throttle factor, but I am aware that settings exists (and we'll need it when we want to switch into PH). I mentioned the 40% position to indicate that the power to weight ratio of our copter is OK.

Thanks again and kind regards,
Johan.

[Max]

Hi Johan,

I suggest you post some full logs of your flight(s). The AQ is certainly more sensitive to vibrations than a Naza, but it's hard to tell what is going in your situation w/out more information.

Cheers,
-Max

[johandm_be]

Hi Max,

Thanks for your message. I have attached the full log.

Thanks & kind regards,
Johan.

[Max]

Yea vibrations seem to be an issue...

Yours:

What you want it to look like (this one has 6 motors):

Your vibrations on the Y axis are worse than on the X for some reason. Also check the MOT_YAW graph -- the quad is compensating in one direction, perhaps due to a slightly tilted motor or other power imbalance. You want the average yaw output to be around zero, like the pitch and roll outputs.

Another comparison of vibration levels, perhaps useful... both graphs here are with well balanced props, just different brands and material: viewtopic.php?f=24&t=2318&p=13047&hilit=vibration#p13047

You will find more discussion on vibration issues on this forum since it's a fairly common problem, as Larry mentions.

HTH,
-Max

[johandm_be]

Hi Max,

Thank you for looking at my log and for pointing this out. We will work on the vibration levels of the setup.

Thanks again and kind regards,
Johan.

[Cookiemonsta]

Did you do the static and dynamic balancing of the prop? I always just check against static imbalance, put the prop on the motor and balance the whole prop-motor combo dynamically with a laserpointer and a mirror. That gives very low vibrations

Cookie

[johandm_be]

Hi Cookie,

Thanks for the advice. So far we only did static balance. Hmmm... I need to think about how to make the setup to do the dynamic balance. I have seen samples on Youtube, I'll have look at these again.

Thanks & kind regards,
Johan.

[LPR]

Johan

A photo of the quad might help to understand the problem. How the AQ board is mounted sometimes causes increased vibrations.

Larry