Problem During Split-S

Discussion in 'Build & Tune' started by Michael Clendening, May 25, 2018.

  1. I have modified my Torrent with new motors and camera. It flies good most of the time. Left the PID settings as they were. Not a lot of oscillation or jitter, takes sharp turns and is pretty smooth. However, when doing a split-s, just as I am rolling to the upside down point, the quad suddenly makes a big movement back towards the start of the roll (maybe 30 degrees). It's a big enough jerk that I often lose orientation and crash. Seems to do straight out rolls just fine. Could that much correction be caused by high I-gain? Ideas? I-gain at Roll=57 and pitch=58.

    Thanks.
     
  2. RENOV8R

    RENOV8R Well-Known Member

    Go to your configuration tab in BF and enable anti-gravity. That should fix it!
     
  3. DrAbsurd

    DrAbsurd Well-Known Member

    big hard bounces can mean to much P gain. A soft bounce is to low and a hard bounce is to high. Keep that antigravity kinda low or it can cause the same bouncing im my experience. My PIDs ended up being way lower than default. right out the gate D was to high and caused motors to over heat some. Heres your grain of salt cause im new to this too.
     
    mozquito1 likes this.
  4. Thanks. Taking laptop and a few batteries out with me this weekend. If anti-grav doesn’t work, I’m gonna try a tuning from scratch. It’ll be my first time trying it.
     
  5. Well. I tried anti-gravity and lowing P rate but still having that hard jerk at the top of my split-s just as it nears or gets to the upside down position. Maybe I'll post on YouTube to show what I'm taking about.
     
  6. Gyro Doctor

    Gyro Doctor Electronics Tech for over 45 years

    Anti-Gravity momentarily boosts the " I-Term" of your PIDs to prevent unwanted interactive results
    in attitudes when making abrupt throttle changes. The most commonly affected axis are pitch and yaw
    though which leads me to suspect that, while it would be helpful overall to have antigrav tweaked, that
    it isn't going to specifically address what you're experiencing. I would recommend against scrapping your
    PIDs entirely though, as they're presumably fine other than needing some minor adjusting.
    Aside from the established functions of each term in PIDs, it may be helpful to consider some of the
    peculiarities of each term. While the P term is faster acting than I, it has a shorter "memory".
    While the I term is slower in reacting, it has a "longer memory". This having been said, my advise
    would be to experiment with the P and I terms for roll only with an INCREASE of the P term primarily
    (you said you lowered it ?), accompanied with minor increases in the I term and leaving the antigrav
    settings where they are (or, better yet, where they were). ;)

    Addendum: You say that a straight roll doesn't exhibit this problem ?
    If it's happening only during a split-s or Immelmann maneuver then is it upon pitch command that it occurs ?
    If so, then you may need to also address the P and I terms for pitch as well. Making small adjustments to each term for each axis until it's fixed is the key, because overdoing it will cause the quad be feel too "stiff".
    It's kind of a game of "hunt and peck" resolving such problems, but if you're performing acrobatics like these I'm hoping you'll also have the "feel" for the improvements as these adjustments are being made. :)
     
    Last edited: May 26, 2018
  7. OK. Lots of flying done lately. I have figured my problem occurs after a punch out. That is what I was doing just before going into my split s. However, I am able to duplicate the issue but just punching straight up and then cutting throttle. A second after I cut the throttle, the quad jerks into a roll and/or pitch of about 30 degrees. It's usually enough to make me lose control. If I keep some throttle on it, no problems. I have tried with air mode on and off. Neither make a difference to this prob. What's causing the erratic behavior after punching? Please help.

    Thanks.
     
  8. Gyro Doctor

    Gyro Doctor Electronics Tech for over 45 years

    Airmode doesn't engage except for at low throttle points.
    Punching out causing pitch and roll deflections is exactly what antigrav was meant to handle.
    Boost "I" gain a little for pitch and roll, then set antigrave to 2.5 and see what that does for you.
    Antigrav will momentarily multiply the "I" term by whatever it's setting is whenever it senses abrupt
    throttle commands, which sounds just like what you need. ;)
     
  9. BINGO! I solved my problem. I figure I will post my fix so that others may benefit. Chalk it up to being a nube. Neither "I gain" or Gravity mode solved my problem so I decided to record my flight so I could show what I was talking about. During the recording, I could see in the goggles that one or both props in my view would come to a complete stop at the top of the punch out after zero throttle. Then, when I gave throttle again, the props would spin up and it would jerk violently (either pitch or roll). I always thought it was a good thing to have no props spinning when throttle all the way down. My drone came that way. When I armed it, the props wouldn't spin until I applied throttle. The min throttle was set to 1070 by default. I increased this to 1110. Now, when I arm. My props spin slow even when there is no throttle applied. Anyway, problem solved no more erratic behavior after zero throttle and I'm getting a very smooth and buttery flight. YAY!
     
    Gyro Doctor likes this.

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