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Quick PID Help ...

Posted by Damien Healy on June 14, 2014 at 10:57am

Hi All!

I'm hoping that someone can give me a quick tip on PID tuning on arducopter 3.1.5 ... I am fresh over from Naza land.

I have built a hex with the following:

Tarot t810 frame

Pixhawk

6x Tiger MN3508 380kv motors

Tiger 15x5 props

 ublox compass + GPS

T-motor s25A 600Hz escs

4S power system (usually >10k mah)

Some pics attached ... the hood is from a tarot 680 pro ...

I hear that the default PIDs aren't well suited for my low-KV setup. You'll see from the attached blurry video that I have some significant oscillations and I ended up in a minor crash on my first day out.

I've also found that the copter is sluggish in responding to throttle.

Can someone give me an idea of basic PIDs I can use to get stable enough to autotune?

Thanks HEAPS. Very keen to get this guy stable.

IMG_0309.mov

photo.jpg

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Replies

  • faria July 29, 2014 at 3:09am

    Hi there,

    Do you have resolve this problem? I have the same problem. I cant stabilize my hexa. My controller is pixhawk and my firmware is 3.2 rc 3. I cant flight

    • Damien Healy > faria July 29, 2014 at 9:53am

      My problem was solved by upgrading my power system to 6S. My hexa just needed some extra power. It now hovers at about 50% of maximum thrust, which is perfect. 

      If your hexa is wildly unstable then the first thing I would look at is your motor or prop configuration i.e. to you have the motors hooked up in the right order and to you have the right clockwise and counter-clockwise propellers on the right motors ... 

      There is actually a handy tool in arducopter that runs each engine for a second or so, in sequence, clockwise to check motor order. I can't for the life of me recall how I did it however. I seem to remember executing a 'motors' command in the command-line interface (CLI?)

      • faria > Damien Healy July 29, 2014 at 10:02am

        thanks a lot for your response.

        I have tested everthing, i believe the motor configuration are correct. However when i take off i adjust the trims. But the radio are very sensitive.i cant control the hexa

        • Michael > faria January 13, 2016 at 6:28am
          If you go into the config/tuning page scroll down just below half way through the page and you should find a setting for RC feelRoll/Pitch(RC_Feel_RP) slide the slide bar across a little towards 0 from 100. 100 being crisp 0 being very soft. This may help although it could be a mix of that and needing to be better tuned.
          Maybe I aren't understanding your question though.
  • Stuart Brookes June 14, 2014 at 11:18am

    what mode are you flying? stabilise or loiter?

    looks like loiter to me. If so this may also be why you think throttle is sluggish, as in alt hold and loiter the throttle stick is climb rate control as does feel sluggish compared to stabilise mode.

    does it osculate in stabilise mode? stab mode needs to be set well before moving onto other modes.

    • Damien Healy > Stuart Brookes June 14, 2014 at 11:26am

      Thanks for the response. I do recall going into loiter at some point during the flight, so perhaps that's it.

      The copter wasn't very stable in stabilise mode however, and still did wobble around.

      Should I expect it to be OK on default settings with my kind of setup?

      I have tweaked my setup since the flight since the batteries had been hung directly off the plate that the Pixhawk was on, and I think that they might have made the platform a little unstable. I've moved things around to avoid that for next flight.

      • Stuart Brookes > Damien Healy June 14, 2014 at 11:32am

        ok, first thing to do befor egetting to carried away making adjustments assuming you have enough control for short flights a meter up or so is make sure you don't have excessive vibration. 

        http://copter.ardupilot.com/wiki/ac_measuringvibration/

        • Damien Healy > Stuart Brookes June 14, 2014 at 11:40am

          OK. I have adjusted the logging to capture this on my next flight. I'll just get a bit up in the air and will aim to stick in stab mode.

          If it is stable enough, I presume that I should get into alt hold and do an autotune.

          • Stuart Brookes > Damien Healy June 14, 2014 at 12:32pm

            Probably best to analyse the logs to make sure you don't have excessive vibes before doing an auto tune. I haven't used autotune yet though.

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