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Unread 22-01-2015, 15:17
Ken Streeter's Avatar
Ken Streeter Ken Streeter is offline
Let the MAYHEM begin!
FRC #1519 (Mechanical Mayhem)
Team Role: Engineer
 
Join Date: Feb 2005
Rookie Year: 2005
Location: Team: Milford, NH; Me: Bedford, NH
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Re: CAN mode question

Quote:
Originally Posted by Thad House View Post
A Bang Bang Controller mode would be cool as well. I know the teams that used it in previous years, including us liked it alot. Would be cool having it just integrated into the controller.
I believe that you will get "Bang-Bang Controller" functionality from the built-in PIDF if you set Kp = infinity (just choose a really big number) and set Ki = Kd = Kf = 0. For "flywheel" applications, you'll also need to constrain the minimum output to be 0, so that when the flywheel is over the target speed, the controller doesn't "Bang" to maximum reverse.

In 2012, we used a bang-bang controller for our basketball-shooting flywheel. It worked pretty well. In 2013, we started out using a bang-bang controller for our full-court shooter -- it was pretty good, but not good enough for FCS. With experimentation during the 2013 season, we found that a PF controller (PIDF where I=D=0) worked more smoothly and more accurately. As mentioned above, PIDF with Kp=infinity and Ki = Kd = Kf = 0 degrades to bang-bang, so it's easy to test both alternatives by just varying the parameters while the robot is operating. For us in 2013, the improvements made the difference between FCS that nearly worked and actually did work. Retrofitting the improvements to our 2012 robot increased our accuracy shooting basketballs, too.

We're planning to use the Talon SRX this year with the built-in PIDF for most of our control loops. Haven't gotten them working yet, but that's been due to cabling issues, rather than problems with CAN or the Talon SRX.
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Ken Streeter - Team 1519 - Mechanical Mayhem (Milford Area Youth Homeschoolers Enriching Minds)
2015 NE District Winners with 195 & 2067, 125 & 1786, 230 & 4908, and 95 & 1307
2013 World Finalists & Archimedes Division Winners with 33 & 469
2013 & 2012 North Carolina Regional Winners with teams 435 & 4828 and 1311 & 2642
2011, 2010, 2006 Granite State Regional Winners with teams 175 & 176, 1073 & 1058, and 1276 & 133
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