PID Tuning with Airmode?

Discussion in 'Build & Tune' started by DrAbsurd, May 24, 2018.

  1. DrAbsurd

    DrAbsurd Well-Known Member

    It seems to me that tuning should be done without airmode on. what do you guys think. Airmode seems like it masks flaws in the tune.
     
    mozquito1 likes this.
  2. Gyro Doctor

    Gyro Doctor Electronics Tech for over 45 years

    Given that all airmode does is increase the minimum throttle point in order to balance motors for full command authority at low speeds, it shouldn't matter whether it's on or not when tuning PIDs. o_O

    What you may be calling "flaws in the tune" could actually just be the limitations of command authority otherwise inherent at lower speeds. ;)
     
  3. Rick M

    Rick M Absent-minded professor

    I'm with GD on this one. Most of the subtleties of tuning are happening at the higher end control extremes. Air mode is operating at the other end of the power spectrum. I wouldn't expect it would change the results of your tuning.
     
  4. DrAbsurd

    DrAbsurd Well-Known Member

    Hmmm. Not my understanding or experience with airmode at all. It seems to be a fully functioning system that uses gyro input to stabilize, not just higher min throttle. thats why there is airmode bounce and some crazy things that happen when you get to close to something and there is air disturbance and airmode trys to correct causing huge jumps or bounces. I try not to use airmode much because I cant skid with it on cause of said bouncing and spinning, but it does make things smoother and you keep better control when you hit min throttle. Turn on airmode and arm it and try to move it around in your hand, it will fight you hard to stay still, adj motor speeds to do it.
     
  5. DrAbsurd

    DrAbsurd Well-Known Member

    Ive got a better understanding of it now. It basically just keeps the PIDs working even during min throttle. Just turning off blade stop doesnt necessarily keep PIDs functioning. changing your throttle min closer to actual min will do mostly the same thing. Ive just got 2 of my rate profiles identical and used that switch position on the 2nd one to activate airmode. this lets me turn airmode on and off easily during flight and not loose another switch. gonna tune it both ways and see what gets the better overall feel.
     
  6. DrAbsurd

    DrAbsurd Well-Known Member

    So it turns out anti-gravity gain was the cause of my tuning problems. Kept getting noise and a lot of nose movement after throttle ups. Couldnt get it to go all the way away with PID changes. Turned anti-gravity down from 15 to 5 and everything smoothed out.
     
  7. Gyro Doctor

    Gyro Doctor Electronics Tech for over 45 years

    Glad you got it sorted out. :)

    Of course it's a fully functioning system that still uses the gyro, it's just that the PIDs get
    "thrown out the window" because you've exceeded their ability to properly function at too low of a level.

    Some command inputs become unstable (which is to say basically either ineffective or producing highly undesirable results) at lower throttle levels without airmode enabled because there's simply not enough available reactivity at lower throttle levels to execute those commands. And, yes, all it basically does is to
    momentarily raise min throttle just enough to perform the command function adequately.

    It works like this: Let's suppose you're at 10% throttle. You now input a command that requires a 30% reaction from the props. The reaction is a function of affecting one of props set by 15% positively while
    the other set gets 15% negatively. At only 10% throttle you do not have the command authority needed to
    impose a 15% reduction of spin on any pair of props, so air mode bumps up the min throttle by 5%
    automatically so that the opposing prop sets can adequately impose the required 30% differential required
    to satisfy the command input. ;)
     
    Last edited: May 26, 2018
  8. mozquito1

    mozquito1 Well-Known Member

    Rick is bang on the money. When I first started flying, the bottom end done my head in. Going down close to minimum throttle it would stall on me & fall.
    Then Mr Bardwell done a video on it & I ain't looked back since. Landing is a bit harder but not as hard as pulling out of a stall. But it's all good now.
     
  9. mozquito1

    mozquito1 Well-Known Member

    I read something a while ago, it can be done another way but you lose resolution. I don't think it works in angle or horizon modes either.
     

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