Throttle issues in maiden flight on 400 frame

Info and discussion about the autonomous Micro FC, suitable for nanos, micros and mini multirotors

Re: Throttle issues in maiden flight on 400 frame

Postby axi » Tue Aug 18, 2015 6:22 pm

Wow, just made some test today, the bad behavior has been agravated a bit, the quad is accelerating by itselft in manual mode, sometimes with yaw movement, scary. I tried to change PID params, but nothing seems to affect...

¿What this can be? It's the first time I've seen anything like this.
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Re: Throttle issues in maiden flight on 400 frame

Postby aBUGSworstnightmare » Tue Aug 18, 2015 8:06 pm

axi wrote:Hi Abug,
thanks for the video, but, that is what I used as guide to tune position hold, if it wasn't for that video, only with the "throubleshooting" section in the wiki, it would be very difficult to have a practical clues.
In the video I posted I show the problem on manual mode, I'm not refering to the high freq oscillations at the end.
¿Altitude PIDs affect also on manual mode?

My frame is difficult to put "on the ropes" for angle and tilt tuning because it has four bobbins holding the upper part of the quad, and I'm afraid they could tear ... I usually tune my minis from scratch with that method because is the easiest way to get good results.
Image


Are this rubber standoffs (the yellow things)? AQ don't like soft mounts.

Well, honestly I don't tune my craft that well... I just take two fingers under the COG log to where it tilts and adjust the battery either back- or forwards. :oops: I don't do rocket science there ...
Do have foam over your baro?

Your log is empty --> not very useful :cry:
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Re: Throttle issues in maiden flight on 400 frame

Postby axi » Tue Aug 18, 2015 9:23 pm

Crap, my fault!
Yep they are soft, maybe ACC_Z isn't happy?
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Re: Throttle issues in maiden flight on 400 frame

Postby aBUGSworstnightmare » Wed Aug 19, 2015 6:20 pm

axi wrote:Crap, my fault!
Yep they are soft, maybe ACC_Z isn't happy?


Yes, you're z-Axis is looking strange! Something is oscillating there.
Here is what 'bad vibrations on all axis' usually look like:
Image
Side note: This craft flies quite well!

And this is from your log:
vibs.jpg

Something seems to move in Z-Axis --> this is what rubber looks like.


Exchange them against plastic standoffs and try again. Please also post a picture of a fully rigged craft. Would like to see where all components are located and how they are mounted to the frame.

By the way: Very good GPS quality. Do you use a shield? Which antenna?
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Re: Throttle issues in maiden flight on 400 frame

Postby axi » Sat Aug 22, 2015 7:20 pm

Hi aBug,
sorry for the late response, after a lot of testing I could mitigate the vibrations effects lowering I and D values, but the effect was definitively there, with more weight it was more noticeable and slight changes of CoG also affects the issue. I'm giving up with this frame/FC combination, it's not worth it the soft orange bobbins are a problem for Autoquad. This was my first build when I started FPVing, it was collecting dust... I tried to recycle it, but it seems like a bad combo. With other FCs the frame works very well, I wonder what is the difference here.

This is the GNSS antenna I'm using http://www.tallysman.com/wp-content/upl ... _Rev21.pdf
I had two from another project hanging around, it should be better to use a GLONASS compatible one with wider bw +1600Mhz. Since I'm not receiving any other signals than GLONASS ( the lower bands ) and GPS. I'm using a 100mm diameter round pcb as a ground plane, cutted with scissors. I removed the magnet and soldered the can shielding of the antenna to the PCB ground plane.
I just followed the minimum required ground plane size for not detune antenna too much, the manufacturer of this antenna recommends 1/2 wavelenght.
I never tested MAXTENA helical GPS/GLONASS antennas, but they don't require ground plane like patch antennas, it's interesting area to dig about.
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