Loiter Mode tuning with Arducopter 3.0.1

Posted by Nikhil Upadhye on October 24, 2013 at 7:40am

Hello,

I am trying to tune my quad with arducopter 3.0.1 firmware for loiter mode. My copter sometime twitches when I switch to loiter mode and in guided mode. Also copter loose altitude significantly when in loiter mode after some time.

 I want to understand what is the significance of 'Loiter PID' and 'Rate Loiter' parameters which are displayed at APM:copter PID tab in MP. I tried to find the meaning of these parameters on Arducopter Manual website but parameters given there seem to be outdated. I even looked at the comments in code on github to find significance of these parameters but did not find anything.

Any help on tuning with these parameters will be appreciated.

You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –
Follow

Replies

  • Piers C March 21, 2014 at 7:22am

    I'm seeing quite big twitches as well when I switch into loiter mode while moving, on quite a big rig, an S800 Evo hexa.  For me it also happens switching into Auto on a mission and on reaching a waypoint, say a 90 deg. turn, where it throws a violent wobble (quite terrifying to anticipate!) on arrival at the waypoint before smoothing out and carrying on its course.  Would reducing P or damping it a bit with D theoretically help I wonder?

    • Piers C > Piers C March 29, 2014 at 3:24am

      Ok, I've solved my problem!  In short by using the ANGLE_RATE_MAX parameter, and even at the default of 18000 it makes a huge difference, and at last makes the craft safe. I've now dropped it down further to 9000. 

      However for some odd reason it didn't appear in the build I had loaded which I had thought was 3.1.2.  I originally cloned arducopter master branch I think from Github, in early march (i,e. after 3.1.2 release), and the release notes there came all the way up to 3.1.2.  I modified the SBUS.c file to work on my futaba R7008 and then compiled.  However the ANGLE_RATE_MAX parameter wasn't in that build I cloned for some reason.

      When later digging around the code for arducopter 3.1.2 branch (not master branch) on Github, I found this promising ANGLE_RATE_MAX paarameter in there, and wondered why it wasn't in my build. Anyway, I never figured that out, but I rebuilt what I now believe is the proper 3.1.2 release (with my SBUS mod) and uploaded, set the ANGLE_RATE_MAX to 90000 and all is now well.

      Thank goodness for this new parameter, though, because without it i imagine large powerful MRs in general would be unsafe.

    • Oliver Volkmann > Piers C April 26, 2014 at 5:00am

      90000? :-) I believe 9000 is safer ;)

  • Oliver Volkmann January 27, 2014 at 8:26am

    Hi Nikhil,

    I too am facing this issue. The twitching between modes isn't bothering me though. What I am experiencing is that while flying in loiter, my copter has a bit of a bumble-bee effect going on and is consistently losing altitude when flying into the wind. By "bumble-bee" effect, I mean that it does not maintain a pitch or roll angle and thus a set speed but seems to pitch/roll back and fourth on its course. Have you managed to solve your issue? Perhaps there is a developer who could comment on this?

    Thanks,

    Oliver

  • dr0n3droid October 24, 2013 at 8:27pm
    Seems to me that the twitch is related to mode change while moving. Faster you go, worse it gets. Guess what happens when a failsafe is triggered @ high speed. My copter does the funky tumble. LVfailsafe triggered RTL, which always caused a confused transition between modes. @ hover, mode change is seamless.
    I can reproduce the behavior by manually switching modes @ speed. Couldn't say why, but extreme direction change confuses the copter, causing the same effect without mode change.
  • Mike Darnall October 24, 2013 at 2:39pm

    Hi Nikhil,

    If you flip to Alt Hold instead of Loiter to take the gps out of the equation, do you see similar behavior? I'm curious if you see the twitch and/or same slow descent over time. I just finished a quad build that is a little on the heavy side and a small change to the Throttle Hover setting helped to fix a stick centering issue when switching to loiter. Not sure if this is your issue but it may be worth a look:

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

  • John McGrath October 24, 2013 at 8:20am

    I have noticed this if you have some forward or sideways movement and switch to loiter you will always get a bump but if you slow down the forward or side movement manually and hit loiter it is smooth as silk. If you go with the parameters on the 3.0.1 guide that is if you have a 3DR it will get you close. I think there will be more fixes in the next release also but I am not a developer. I am sure Randy or someone will put there 2 cents in for you Nikhil.   FYI I have been dealing with setting up an external compass in the past few days and Randy has been a great help.

This reply was deleted.