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Unread 28-07-2013, 07:59
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JamesTerm JamesTerm is offline
Terminator
AKA: James Killian
FRC #3481 (Bronc Botz)
Team Role: Engineer
 
Join Date: May 2011
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Location: San Antonio, Texas
Posts: 298
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Re: paper: FRC #33 The Killer Bees 2013 Software - BuzzXVIII (Buzz18)

Hi Palardy,
So I have started to integrate the Culver drive controls in our simulation and I have found some interesting findings:

When I started testing this, I found that not all circular controllers have the same diagonal intensity as the LogicTech F310. I tested the AirFlo which is also circular, but in testing, it reached full x and y intensity at the corners. I am not sure if there is a spec yet for identifying this, but it should probably be in a form that shows the full x and y intensity ratio (when diagonal), because the F310 I have tested if you normalize x and y readings and move the joystick to its full diagonal where they are equal...it is more than (sin(45) / 70.7...) it's around 80. I believe though that controllers like the AirFlo can still benefit from the Culver drive, because the faster speeds really shouldn't matter as much.

So using just the theta and magnitude and testing this with full y component magnitude. I put a UI feedback that shows what the value would have been if I just used the x component right beside the new value of (theta * r). It turns out they were equal (at first)! This means anyone can simply use halo drive code and control the wheel in the same manner to get the same effect. Now then in regards to the 80% normalized value I mentioned above... as you rotate the wheel closer to 90... the magnitude will actually exceed 1.0... to around 1.14... so as it gets closer and the magnitude increases you lose precision you would have had otherwise, but at these faster speeds it doesn't really matter.

So I have some good news though... I'd recommend you try the same tests if you can and see if you are getting the same results. If I scale the magnitude to around 0.875... this works out perfect where it starts with a magnitude of this (0.875) moving joystick to full Y with x centered... and then by the time it reaches the corner it will be around 1.01. With this you can finally achieve a greater precision for the slower speeds. The derivative of the distribution looks like a "soft" x^2 when compared testing against the x components raw value otherwise.

One other interesting note is that I tested the halo drive scenario (i.e. no Y component)... this turned out to lose more precision than otherwise, but not by much. That said, this solution cannot substitute the need to filter out the dead zone of the joystick, and it should be virtually the same amount as otherwise. This loss of precision could be a benefit for an alternate quick-turn solution. For our setup the workflow may be to use halo drive for most quick turns, and then the Culver wheel drive to fine tune the turns. On Monday I'll try to show a demo of this and these number findings on YouTube.

Last edited by JamesTerm : 28-07-2013 at 08:03.
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