Hello everyone,
I'm experiencing some problems with the settings of the PIDs on my hexacopter. With a carbon frame (weight 110g), Aerodrive motors Turnigy SK3 3536-1050kv and two battery packs from 11.1v - 5000mAh (about 550g each) I need to set the PIDs in this way:
- Rate Roll / Pitch P: 0.045 - I: 0.09 - D: 0,006
parameter P seems to me really very low, but if I decrease the value, the drone starts to oscillate (freq. 5-10 Hz approx.) The value of D seems too low, but not having a yardstick for me it is very difficult to assess.
The drone is close to the limit load (takes off with the throttle to 60%) but I do not think that this is a problem that leads to these annoying shakes. APM stay over moongel so is insulated by vibrations.
I await your wise counsel
thanks in advance
Pasquale
Replies
While I wouldn't suggest these settings exactly for your hex, they work for me. I use quite different PID's for my Tricopter which turns the 'copter into a really smooth but tight and responsive 'copter. I've used similar values on a quad but here they serve to show only the variance to yours. My motors are 980kv with 11x4.7 props.
For Rate roll and pitch:
P = 0.2800
I = 0.3100
D = 0.0160
I'm using 10x4.7 props.
Just an info: the I what changes bring? If i'm not in error P is the strengh of reaction when errors in angle comes, so if i increase too much that value hexa is more nervous, decreasing will be too sluggysh, right?
I and D can't understand what changes produce on attitude of my hexa
One effect of I is that it corrects balance problems and keeps the 'copter more level, it also dampens the bounce caused by a high P. P is the strength of the correction but it does little to keep the copter level, it only reacts to an input or external force.
Note that the new Autotune feature sets P and I to the same value, but I prefer I to be a bit higher.
D adds a bit of overall damping but can cause high frequency oscillations most easily seen when hovering close to the ground (in ground effect). If you hover 15-30cms (6"-12") off the ground and hear the oscillations then go a little lower on the D (and always tune D last).
Important: If your hex feels nervous then lower the Stabilize Rate Roll and Pitch to 3.0, 4.5 is way too high for the default IMO!
I set stabilize PIDs following your valuable advice (in another discussion) and now my hexacopter fly very well.
It is, however, presented a problem, before that it was less frequent but now (after changing stab/rate.roll/rate.pitch/rate.yaw PIDs) it's really annoying: sometimes the drone starts to rotate on the yaw of about 45 degrees, like a spasm, and earn half a meter or a meter of altitude while it rotates. I am absolutely sure it's a matter of the yaw PID, but what? Changing values I can't reach any valuable result!
I need your help again!
Thank's a lot
Sorry Pasquale, I don't know what would cause that. I would say it's not related to the PID's but I could be wrong. Vibrations can sometimes cause that kind of thing or a skew airframe.
Just get the PIDs to a point where the copter will fly. Then engage auto tune and let it do the job for you. It works really really well.
+1 on this.