Gimbal "Speed"/Reaction

AutoQuad AV/AP settings, gimbal & servo choices

Re: Gimbal "Speed"/Reaction

Postby Max » Thu Nov 15, 2012 11:50 pm

Have you seen my "extreme conditions" gimbal test video?

This is version 1 of my home-made gimbal so there are still some vibrations, the lens isn't centered perfectly, and I only adjusted the scale parameters roughly before the flight. Plus it's extremely windy... :) So I'm not saying this is a great example of stabilized video, but it does show off the capabilities of the gimbal and AQ. Check out @ around 0:20 in the video where it does some extreme corrections and keeps up rather well. Granted at 45 degrees tilt the horizon is off just a bit... but that's some extreme compensation and like I said w/out real tuning and the lens a bit off center.

-Max
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Re: Gimbal "Speed"/Reaction

Postby pairair » Fri Nov 16, 2012 4:42 pm

Looking good Max!
Could it be that the slow motion has something to do with the 5:1 belt reduction on my gimbal?
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Re: Gimbal "Speed"/Reaction

Postby Max » Sat Nov 17, 2012 3:18 am

5:1 is quite a bit... mine is 3.33 reduction on roll and 1.67 on tilt. I'm using 180* servos though, not 360 (yet)... you can get away with higher reduction rates on those, obviously, at least in terms of range of movement. I determined my ratios based on the maximum angles I wanted, and now that I look at my numbers, I only have ~27* in each direction on roll axis... so that would explain why the horizon isn't quite level in the video with the extreme tilt.

So anyway... slowly reducing the scale parameters doesn't help? You'll definitely need faster movement with 5:1 ratios! I'm not sure, but I think my Roll Scale for that flight was 0.00828570 (down from .01428571 default) and Pitch Scale was default (.01098900).

I don't have any direct experience with 360* servos and am curious about how those are set up. Do you have to do anything with the external pot in terms of adjustment or calibration?

-Max
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Re: Gimbal "Speed"/Reaction

Postby SuperDave42 » Mon Jan 28, 2013 9:25 pm

Is the AQ controller able to output Trapezoidal or S-curve or hybrid motion control to the Gimbal ? it's something I see used a lot in mechanical automation and motion systems. It is also something I feel is missing from our RC motion platforms. It basically is a way to smoothly accelerate / decelerate a load. To correct for very fast movements the system would need to react very fast and accurately.
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Re: Gimbal "Speed"/Reaction

Postby bn999 » Mon Jan 28, 2013 10:58 pm

There are two components to gimbal control. The most important is automatic leveling. Such motion profiles are really not applicable to leveling. There is no start and stop position that you would plan a smooth motion between. Instead, the idea is to follow as quickly and accurately the commands from the flight controller, which are simply the inverse of the platform's attitude, which should be smooth to begin with as it is dictated by the inertia of its mass. You don't plan a smooth motion when a sudden gust of wind pushes your machine off level.

However, if the user wants to re-aim the gimbal (the second component), smooth motion is desirable and motion planning makes sense. AQ currently uses a pseudo s-curve technique which effectively gives you this smooth motion between user's requested aiming commands. The closer the gimbal gets to the desired position, the slower it decelerates. More complex techniques could be designed.
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Re: Gimbal "Speed"/Reaction

Postby SuperDave42 » Tue Jan 29, 2013 9:49 pm

Thank you for the reply and explanation. Yes my questions was intended for manual cam control. Most everything I see has a very robotic / jerky manual control . It's good to see the AQ has the ability to smooth out user interaction.

Very cool

Dave
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