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Unread 22-05-2015, 16:36
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Jared Russell Jared Russell is offline
Taking a year (mostly) off
FRC #0254 (The Cheesy Poofs), FRC #0341 (Miss Daisy)
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Re: Brownout behavior - alternative design goals

Quote:
Originally Posted by Andrew Schreiber View Post
254 probably has more data than I do because they run closer to the edge, but I can tell you that in a season like 2014, when we DIDN'T have a short in our wiring, 125 rarely went below 6V despite some very aggressive gearing in both our drivetrain and our launching system. The only times (I recall) we had serious current draw* issues were when a vastly over-inflated ball jammed in our intake, the choo-choo was loading, and we were driving aggressively.

That being said, wasn't it you who coined the term "drivetrain wars" all those years back when we first started getting CIMs? I just view this as a good way to end those. EDIT: My memory DIDN'T fail me. http://www.chiefdelphi.com/forums/sh...79&postcount=1



* This ignores that we spent the first half of the season with a short that was causing us to die on the field regularly.
I'd much rather see the drivetrain wars moderated by game design (one of the only things I liked about Recycle Rush, though 2012 and 2013 did a great job of this as well).

Failing that, I favor limiting the number of drive motors, a speed limit, wheel restriction, etc., rather than brownouts. Brownouts can be insidious to deal with (if you have any control loops), and be next to impossible to completely avoid (the dynamics of any FRC robot frame mean that instantaneously, your wheels may be loaded really unfavorably when driving around the field). An FRC robot that is designed (mechanically) to be incapable of dropping below 6.8V would be a fairly uninspiring robot to watch.

Forgive my ignorance on such things, but is there any way to default the motor brownout to 6.8V, but allow teams to do something else "if they (think) they know what they are doing"? For example, I could see doing prioritized load shedding (ex. first drive, then intake, but position-controlled elevator last) as a viable way to deal with this, but there isn't really any headroom above 6.8V with which to implement such a scheme.
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