Gimbal "Speed"/Reaction

AutoQuad AV/AP settings, gimbal & servo choices

Gimbal "Speed"/Reaction

Postby Johan_vV » Mon Nov 12, 2012 10:10 pm

Hi,

Im working on a frame with a gimbal now and noticed that the cam/gimbal remains very stable when there are slow movements, however, when there are faster ones then it feels like its running behind a bit and starts to under/over-correct it self and start swaying.

However, I should also say that im still testing the frame on my work-bench and it has not been in the air yet, so maybe my movements are way to aggresive (meaning that this wont be any problem when flying?).

I attached a laser pointer to a servo and the same behavoir can be seen in this vid (sorry for the cat): http://youtu.be/XOCZUwxHOnE

Is there a way to speed up the gimbal reaction time or would the result above be consireded as fast reaction time which should be sufficiant for providing stable video?

Thanks in advance!
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Re: Gimbal "Speed"/Reaction

Postby chschmid » Mon Nov 12, 2012 11:15 pm

Hi Johan

What Servo @ what voltage are you using?

Best

Christof
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Re: Gimbal "Speed"/Reaction

Postby joebar.rc » Tue Nov 13, 2012 8:40 am

Johan_vV wrote:Hi,

Im working on a frame with a gimbal now and noticed that the cam/gimbal remains very stable when there are slow movements, however, when there are faster ones then it feels like its running behind a bit and starts to under/over-correct it self and start swaying.

However, I should also say that im still testing the frame on my work-bench and it has not been in the air yet, so maybe my movements are way to aggresive (meaning that this wont be any problem when flying?).

I attached a laser pointer to a servo and the same behavoir can be seen in this vid (sorry for the cat): http://youtu.be/XOCZUwxHOnE

Is there a way to speed up the gimbal reaction time or would the result above be consireded as fast reaction time which should be sufficiant for providing stable video?
Thanks in advance!


The flightcontroller will output gimbal pwm based on the flightcontroller angle and/or disturbances.
We can create a slower response but a faster response would mean losing resolution (bigger steps).

So, on flightcontroller level, yes it could be done but with a penalty.
The pwm is obviously fed in the servo, and therefor the actual speed is very servo depended. Most servo's have two speeds, on at 4.8V and one at 6V The latter is always faster.
So, if your servo can take higher voltages you can have faster responses. If not sufficient, well then you should look for faster servo's.
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Re: Gimbal "Speed"/Reaction

Postby Max » Tue Nov 13, 2012 9:02 pm

Have you tried adjusting the Gimbal Scale Pitch/Roll settings? The defaults were a bit high (slow) for my 7v Hitec digi servos with belt-drive reduction linkage, especially on the roll axis.

-Max
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Re: Gimbal "Speed"/Reaction

Postby Johan_vV » Tue Nov 13, 2012 9:50 pm

Thanks for your suggestions.

Good point about the voltage to the servo. The Servo i was using in the vid is a 0.15 servo and i think that the voltage is a bit low (feeding it from a battery in this test).

I have faster servos on my gimbal (0.04 sec) and i am powering them with 6 volts and i am seeing the same behaviour on those.

If i understand the wiki correctly the Gimbal Scale only affects the "end-Points" so that it compensates enough for the tilt? - It has nothing to do with the speed that it travels to the desired position?
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Re: Gimbal "Speed"/Reaction

Postby Max » Tue Nov 13, 2012 10:08 pm

Which wiki are you reading? :)

http://autoquad.org/wiki/wiki/getting-s ... -settings/
Gimbal Pitch scale - Default 1/90 degrees – scale factor pitch servo = speed to reach and angle in respect to angle aircraft
Gimbal Roll scale - Default 1/70 degrees – scale factor roll servo = speed to reach and angle in respect to angle aircraft


-Max
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Re: Gimbal "Speed"/Reaction

Postby pairair » Wed Nov 14, 2012 9:44 pm

I had the same experience. I have a Cinestar gimbal, Freefly 360º servos with external potentiometers, 0.08 sec on 6V. Default scale value would make the gimbal overshoot, so lowered them some to correct angle. Very slow action. Would lowering/raising scale value make it faster without affecting the "end" angle?

/Pär
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Re: Gimbal "Speed"/Reaction

Postby Johan_vV » Thu Nov 15, 2012 9:44 am

pairair wrote:I had the same experience. I have a Cinestar gimbal, Freefly 360º servos with external potentiometers, 0.08 sec on 6V. Default scale value would make the gimbal overshoot, so lowered them some to correct angle. Very slow action. Would lowering/raising scale value make it faster without affecting the "end" angle?

/Pär



My experiance when adjusting the "Scale" parameter is the same as yours. This value makes it undercorrect/overcorrect the gimbal if i tilt the AQ. I used the Scale parameter and adjusted it so that the gimbal is leveled in different angles when i keep the AQ still.

So, if the "Scale" parameter also affects the speed that the servo moves to the correct positon, then how would i make the gimabl move as fast as possible without over/under correcting when holding the AQ still in a specific angle?

Rgrds
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Re: Gimbal "Speed"/Reaction

Postby mr_westie » Thu Nov 15, 2012 10:07 pm

Most FC have basic gimbal stablisation routines.
Their primary focus should be craft stability.

To get more than basic gimbal stabilization you have to go for a separate controller.
It does not have to be that expensive.
This is the route I took when I wanted more from my YS-X6.
http://www.rcgroups.com/forums/showthread.php?t=1710318
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Re: Gimbal "Speed"/Reaction

Postby pairair » Thu Nov 15, 2012 10:23 pm

Hello mr_westie,

I have tried the Multiwii Crius SE too ($30), and the Photohigher Skyline RSGS gimbal stabilizer ($350).
I just believe (hope...) that the AQ6 can do better than what I'm seeing at the moment.

/Pär
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