Discussions

PID config

Posted by Recmaster on October 26, 2010 at 5:37am
Yellow people!

I've a question about PID.
Is there some situation than I need to tune a PID parameters (AP_PID_settings.h)?
How to calculate it and where from depends (I mean airframe size, mass, and so one)

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Replies

  • Rui Manuel Cravo Marques May 31, 2011 at 6:44pm
    Hello. I'm a Quadcopter newbie...not only that but an entirely RC piloting newbie... "Earth Control, we've got 2 major problems"... First let me introduce myself : Rui, from Portugal, 37 years old, Computer Engineering student. I've began with Arducopter project only about a month ago. I've made may own structure with the help of some friends (cutting acrilic pieces and alloy pieces). My copter is about 60 cms motor to motor and after all the assembly needed (soldering terminals on ardupilot and oilpan, magnometer, gps, etc, motor terminals, esc terminals, building my own power distribuition board, etc), I's time to teste my quadcopter / arducopter. Even though I'm getting a lot of boot fails (don't know why), and quad stopping respondig to rc commands (also don't knowing why), I've managed to get my first test run, and...DECEPTION : A lot of wobbling side to side( flying in X configuration, wobbling also in X, not side by side or front to back). So I decide to start studying PID settings. I've altered the default PID settings from original/default configuration and managed to get a much stable flight test. I'll be twicking it more in the fouthcoming days, but I believe we could be making a database with the tested configurations and settings. I believe this are the most important specs in order to get a good stable PID setting : arms length, motor to motor ( center) length, motor specs (Kv) and dimensions, ESC's A's and weight, ESCs attached to arms or center, proppelers used, battery type, battery weight and dimensions as well as mounting place, height from base to bottom, height from arms to top, arms dimensions, material and section (round or square), magnetometer (compass), gps, etc. We are part of a developing comunity :) I'll be glad if I can help someone. As soon as I can get my quad stable, I'll be posting here it's specs and PID mods.
  • Developer
    Jason Short October 27, 2010 at 8:17pm
    Here is a tip. you don't need I or D to get a plane to fly OK. set them to 0. Start with the P term used for stabilization and raise it until the plane gets unstable. Then lower it back to a value that works. Use Fly-by-wire to do this tuning.

    Don't use the D term for stabilization. You don't need it.
  • Developer
    Jason Short October 26, 2010 at 8:49pm
    The navigation PID gains were derived from Xplane. The stabilization PID gains were trial and error. Think of P as the immediate response, I as the gain to overcome opposing forces, such as gravity. And D a a dampener that slows down the change. I is good to overcome steady state errors. An example is the rudder response of an easystar. If you set P too high, it will over respond and the plane will rock back and forth. If you reduce it to remove the rocking, P will be too small to hold the plane at a full roll angle. That's where I comes in and gives you a boost when it sees you can't get there with P alone. It does this by adding up the error over time and applying that number to the rudder.
  • Moderator
    Sgt Ric October 26, 2010 at 3:45pm
    Adjusting your PID settings requires alot of hands on field work and is half the fun (?) (chuckle) of the AP project.

    People have been sharing their PID settings for common airframe types like the EZ, etc., but there is almost always more tuning required since not every EZStar, etc is built, trimmed, or configured identically.

    I am sure there exists a library of settings already.
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