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Old Jan 06, 2013, 01:19 PM
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Strange gimbal movement - ideas ??

Heya folks,

After some trouble-shooting ideas regarding some funky gimbal movement im getting

basically the system is 2 axis, 2:1 belt drive on both axis, all ball bearing pivots, analog hitec hs82mg (0.12sec @ 6v) metal gear servos (new) running at 100Hz and 6V through a separate BEC, control through my naza.

there is zero mechanical slop in the system. gear backlash in the servos is minimal, but it is there.

problem is when rocking the frame from side to side, ie rolling from left to right repeatedly, im getting a lag/delay at the very moment the roll changes direction. you can see this quite clearly in the first video below.

the gain settings are otherwise spot on, the horizon stays level and controlled the rest of the time, but there is def something funny going on!

i kow the naza isnt great, but i havent heard of other people complaining of this particular problem, and im otherwise quite happy with how the naza is driving things.

so yeah.... the question is! - is this a control problem (ie naza is crap) or is it a servo problem (ie crap servos) or have i missed something altogether and theres something else i could be tweaking?

cheers
ed

latest video @ 100Hz after i tried playing with a few things to see if i could improve the lag. best demonstrates the lag issue during rocking from side to side:

Ed's IAISS Y6 - fine tuning 2 (0 min 38 sec)


and the following is my first video from earlier today @ 50Hz wheni first fine tuned the gimbal for the first time. im pretty happy with how it works in generally, just that lag during rocking motion has me stumped!

Ed's IAISS Y6 - fine tuning (0 min 32 sec)
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Last edited by ed_jza80; Jan 06, 2013 at 05:15 PM.
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Old Jan 06, 2013, 03:59 PM
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United States, UT, Cottonwood Heights
Joined Mar 2012
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It might be the buffer lag out of the gopro.
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Old Jan 06, 2013, 05:14 PM
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Joined Dec 2007
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never seen any artefact like that out of a gopro before

im 95% sure its a naza control issue, in combination with basic analog servos.

it would be nice to know if anyone has seen similar effects with naza based gimbal systems, before i go chasing new hardware for a gimbal control system
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Old Jan 07, 2013, 09:06 PM
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Philippines, NCR, Quezon City
Joined Apr 2012
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Hi! I have the same problem with my KK2.0 board with firmware 1.5. I know it's not comparable with the NAZA but i think it's not the FC's problem. I think it's the servo increments. I have already tried digital and analog servos with no luck. It is worth trying if you increase the gear ratio to 1:5. Then put some dampening on the camera plate to absorb the remaining jitter.
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Old Jan 07, 2013, 10:56 PM
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United States, NJ, Manville
Joined May 2006
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We had the same problem with Hitec servos and 5:1 ratio ...Switched over to the Photohigher gyro same ratio and still had the same lag...switched to savox servos same ratio and radian gyro and the problems went away...
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Old Jan 08, 2013, 12:23 AM
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Philippines, NCR, Quezon City
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Quote:
Originally Posted by skizziks View Post
We had the same problem with Hitec servos and 5:1 ratio ...Switched over to the Photohigher gyro same ratio and still had the same lag...switched to savox servos same ratio and radian gyro and the problems went away...
So is it the gyro or the servo? I can get a savox servo but i guess the price is over-rated. Do you think that an ALIGN DS620 will do the same?
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Old Jan 08, 2013, 03:47 AM
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whats the deadband on the various servos you guys are using? the HS82MG that im using is 0.008s which is on the slower side.

the Hitec (cheaper digital) HS5084MG servo (about equivalent to the HS82MG in size/spec)although not programmable, has a deaband of only 0.002s and is about twice as fast @ 6v

http://www.servocity.com/html/hsg-5084mg_servo.html

thoughts of giving this servo a try?
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