We’ve been working on tuning a quadcopter and are running into instability when the vehicle is braking in loiter mode.
When braking from high speeds the vehicle will rock back and forth several times before settling down, particularly when flying diagonally into the wind. Looking in the logs, the roll overshoots the desired roll (and pitch overshoots desired pitch) significantly (some flights upwards of 15 degrees).
PosHold doesn’t exhibit this rocking behavior, but skids/slides a lot more than desired.
We’ve done an initial tune, added a harmonic notch filter and a couple autotunes and have been playing with these loiter/loiter brake parameters (I included what they were set to in the atttached bin file):
LOIT_ACC_MAX 450 cm/s/s
LOIT_ANG_MAX 25 deg
LOIT_BRK_ACCEL 250 cm/s/s
LOIT_BRK_DELAY 0.3 s
LOIT_BRK_JERK 50 cm/s/s/s
Unfortunately we haven’t found a combination that gives us good braking behavior. Any advice on which parameters you would tweak to fix this behavior? Does this look like a loiter parameter issue, a general tuning error or something else?
Your INS_HNTCH_REF,0.2974782 (the starting point for filtering) is higher than you hover thrust MOT_THST_HOVER,0.2554461 so harmonic notch filtering will not happen until thrust increases to 0.297 or more.
Set INS_HNTCH_REF to 0.2 and rerun Autotune
Try these Loiter params too
LOIT_ACC_MAX,600
LOIT_BRK_ACCEL,300
LOIT_BRK_DELAY,0.3
LOIT_BRK_JERK,300
Generally instability in Loiter is poor tuning elsewhere (attitude control).
So there’s no 1 simple fix, especially without a log file to check.
Also see if you can better describe what you see, and share a link to a .bin log file where this is happening.
Hi i have a simmular problem with a 30inch coter a try to tune.
copter is responding good and auto tune looks okay.
but when flying in loiter, when copter gows in to braking its get verry unstable.
can somboddy give me some advise.
yes a redused the speed to 5m/s
and max_angle to 15deg for al flight modes but whith a simmeler copter a can go way higher then this.
when a fly in althold same problem ocurse but not so vailend
Ben none of the “change reason” was touched. I can not understand most of the decisions you made while configuring the vehicle. For instance the GNSS configuration is very strange. But it might be correct under special circumstances. But I do not know your circumstances because no “reason changed”.
my opinion is that the body chell off the drone is creating a hi presure bubbel onder the top body when braking and causes the drone to reduse the motors so match that it becoms unstable.
