Adjusting throttle PIDs (which should I adjust?)

Hi Guys, I finally got my newly built quad out for a test flight yesterday, set up is as follows:

X650 Carbon quad
APM 2.5 (currently no GPS fitted as it stopped working)
Tiger MN series 700Kv motors
13x6.5 props
3S 6000 mAh Lipo

I was pleasantly surprised at how stable the craft was and there was clearly plenty of available power. However, it became clear (particularly when it was time to try a controlled landing) that the throttle was very difficult to balance. The craft would either drop quickly, at which point i would input some throttle, then a bit more throttle, then it would climb quickly, so i'd back off the throttle, and back off some more, and it would drop again. It was very difficult to balance the throttle to get the craft into a controlled decent.

I finally got the craft back down to earth in what you might call a controlled crash. It's clear that some adjustment needs making to the throttle PIDs, but i'm not sure which, or which way to adjust them.

I'm using the latest Mission Planner, and my current settings are (default I think):

Throttle Accel
P: 0.8200
I: 1.6400
D: 0.0000
IMAX: 5.0

Throttle Rate
P: 6.0000
D: 0.5000


Altitude hold
P: 1.0000

Can anybody tell me what i might need to adjust, and which way, in order to smooth out my throttle response? I think at the moment the problem is that the throttle response is too sluggish, but i'm not sure how to correct it. Any help greatly appreciated.

Jake

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Replies

  • T3
    Is your transmitter a ratcheted model? When you move the throttle does it click? If so you need to either get a non ratcheted transmitter or remove the racket from your transmitter. If this is not your problem, then you just need to learn how to work the throttle in stabilize mode. Have fun and fly safe.
  • Jake, as a new flyer I was doing exactly what you describe, but it wasn't a tuning problem, it was just me. What made things much easier for me was to set up what's called "Exponential" (or Expo) or a "Throttle Curve" on my RC transmitter. 

    With a stock RC transmitter when you move the throttle stick the transmitter's output to your aircraft follows it exactly. It's linear. What Expo does is to change that shape and flatten it at locations of your choosing. Say for example your multirotor doesn't even start to lift off until 40% throttle and hovers at 50% throttle. You're moving the throttle stick over 40% of it's allowable travel and the multirotor is just sitting on the ground. Adding Expo or a Throttle Curve takes back that wasted movement. Below is a diagram that graphically explains the difference. Note that at the hover point at 50% throttle the example with Expo allows you a lot finer adjustment of the throttle and will lessen the yo-yo effect. The downside is you will have to wade through the likely convoluted manual on your RC transmitter and figure out how to set it up.

    3692811494?profile=original

  • Pending seeing a log file you might want to confirm via the flight mode page in Mission Planner that you are in fact in Stabilize mode, not Altitude Hold. Mentioned because the latter has a large dead-band at throttle mid-stick. 

    Also check that you don't have a lot of throttle expo dialed in on your transmitter, or a throttle curve established that acts in similar fashion.

    Aside from those things, fine manual throttle control on powerful rotorcraft requires skill that does take practice. Wild yo-yo action is pretty much normal for beginners. If this is your first rotorcraft, consider practicing throttle control with either a sim or a toy-class heli. It may also help to add some weight simulating a camera and gimbal or such, as many multirotors are way overpowered when unloaded and thus have really sensitive throttle responses.

  • Developer

    It sounds like you are in stabilise. If this is the case then none of the parameters are being used.

    Have you adjusted your mid throttle?

    If you post a log we can help you more.

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