[Vardamellon]

Hello,

I am using Librepilot 16.09 RC1
on a 4s battery with 250 class quad with F1 CC3D, Storm 30A ESC with oneshot and active breaking.

I fly in acro+ for all 3 axis at 70

PID has tuned to be my liking. 

both roll and pitch flies really well, doing what I am expected to be. yaw is pretty good too, except when I do sudden strong yaw stick movement the quad shoots up for a second. it shoots up further if I do full yaw sticks (with acro+ 70)

I tried to reduced my P to 2 and up to 15 just to see what happens, they all do the same thing, just not as intense when P was at 2.

I even tried my rate to as low as 360 and as high as 900, same issue.

I am not sure if i am missing anything or if its a bug?

I dont have a video cuz I usually fly by myself and the last time I tried to do it with one hand I crashed lol

thanks!

[f5soh]

Hi,

First you need to understand how Acro+ works, from wiki :

Code: [Select]

Acro+ is a flight mode that mixes Rate with manual actuator outputs. It allows the pilot to go from very modest rates to full on madness. It does this by bypassing the gyro for rotation during stronger stick deflections and applies manual output signals to the ESCs.
When switch to Manual the gyro readings are skipped so no angular speed limitation using Acro+.
This mean also when you do full Yaw two motors go full throttle, for example 1 and 3 in diagonal, the two others (2, 4) are stopped.
What happens in this case ? How powerful is your Quad ?

[Vardamellon]

i am running skitzo 2004 2500 motors with 5040 tri-blades

when I do acro+ for yaw:
when I do full yaw sticks, it spins with moderate altitude gain, then when I let go and release the stick, thats when it shoots up and gain a lot of altitude for about a second, then it stablized

when I do rate only for yaw:
same situation.

it seems to me the 2 motors that were idle during full stick yaw starts spinning and the quad shoots up and then it stablized itself when I release the stick.

hope this make sense.  maybe this is normal behavior?

[f5soh]

Not sure if resolve your issue but maybe try to reduce the I term limitation (ILimit = 0.3 default) for Bank used, in UAVOBrowser:

[Vardamellon]

what is i term limiation?

I will give it a try tomorrow.

thanks!

[Vardamellon]

I tried it and its not really helping.

I only focus on yaw:
ilimit = 0    quad starts to drift on yaw axis no matter what
ilimit = 100       same issue as 0.3

I cant set negative values for I on the phone app.   

I guess I will just accept this is the limitation of the F1 CC3D and librepilot and use rate for yaw and set the value at around 500 deg/s so I don't get crazy shoot up.

thanks for the help tho

[f5soh]

ILimit is a I term limitation.

Set to 0 do not make sense, is equal to remove the I term so drift is normal.
Set to 100 mean no limits.

Try maybe 0.15 and look if behavior is the same.

set the value at around 500 deg/s so I don't get crazy shoot up.

500deg/s is already a very good rate for Yaw, what rate do you expect ?

Using Acro+ you should set the Yaw rate to something slow because you still get manual control at full stick.
Setting high rate + Acro+ is not needed, you should keep all default rate settings using Acro+

[Vardamellon]

sorry for not been clear, I also did set the limit to = 0.1 as well. ever so slightly improvement.
I will try 0.05 and see what happens.

I guess I am just trying to follow those guys who use betaflight who uses high rates and try to imitate their set up with librepilot. I want snappier control and I guess F1 controller can only do so much

[f5soh]

Ok.

High rates are not needed if you set Acro+, you should keep all defaults rates
Nothing related to F1, F3 Cpu.

Anyways, if you want to do like Betaflight guys why not simply use Betaflight ?

[Vardamellon]

dont get me wrong. I am happy with librepilot and what it offers.

I only started playing race quad about 6 months ago and just trying to see how much I could do with tuning thats all.

I dont know how much better it will get when I go with F3 or F4 boards because I haven't try it yet.

when I have the budget I will build a new quad with F4 raceflight and play with it.  I intend to keep my current quad with librepilot.

thanks for your help

[paulj]

I would be very surprised if an F3 or F4 board will make any difference. One of the issues which may be influencing the behaviour of the quad is simple physics. The algorithms used for determining the target motor settings are based on symmetrical behaviour of the motors. If you have a high powered quad and you command maximum yaw, two of the motors spool up to maximum, and the others are commanded to go to minimum. If the acceleration of the motors going to maximum is quicker than the deceleration of the motors going to minimum, then you will have a net increase in lift until the motors reach their target speed. Do you have braking set in your speed controllers? Maybe you need to look at optimising the speed controller settings (using SimonK or BLHeli?). I would be very interested to see if using Betaflight with the current quad setup makes any difference to this behaviour. When you watch others, you can't assume the behaviour of the quad is entirely controlled by the flight controller - the pilots who achieve what you want to do may be reducing the throttle momentarily with the yaw command, because they have learned what their quad does under these circumstances.

[Vardamellon]

noted. thanks!

[TheOtherCliff]

In case someone else has this problem...

A common cause for this is that active braking / light damping / comp pwm is not actually enabled in the ESC.  This makes the motor spin up quickly, but without braking it does not slow down quickly.  When the motor speeds are quickly commanded to say +-20%, it gets up to +20 quickly, but it never gets down to -20%, so the average is say +10% when it should be 0%.

[Vardamellon]

very good to know! Thanks TheOtherCliff!

I actually updated my ESCs to 14.8 from 14.0.  active braking/light damp are on for sure.

my demag compensation is low, so I should change it to high and see if it improves my issues?

[TheOtherCliff]

I also have this a little bit and just live with it.

Reducing the max rate and manual rate for yaw will reduce it the same way avoiding full stick will reduce it.

To be honest, I don't mess with the ESC settings other than Light Damping / COMP_PWM on.