27-12-2012, 12:23
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Passionate FIRST-er, CD donor
AKA: Gerry
 FRC #0578 (Red Raider Robotics) Team Role: Mentor
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Join Date: Jan 2012
Rookie Year: 2008
Location: Rochester, NY
Posts: 256
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Re: Questions about Encoders and PIDControllers
Quote:
Originally Posted by Ether
No, that's not how positional P-only works. With P-only, there would still need to be an output of sufficient magnitude to maintain a position against any external forces. With P-only, this output comes from the steady-state positional error.
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We actually agree on this. I said the output would go to zero if the system reaches the setpoint. With P-only, the system will never reach and hold the setpoint; it can hold a steady error.
Quote:
Originally Posted by Ether
Yes, they really are that different. If you are controlling position, then the plant is an integrating plant. If you are controlling speed, then the plant is not an integrating plant. They require different strategies.
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That assumes you are always measuring distance, whether controlling position or speed. If you measure speed for speed control, and set your P, I, and D constants accordingly, it works out to the same concept.
__________________
Cal
R3: Red Raider Robotics (FRC Team 578)
Fairport, NY, USA
www.FairportRobotics.org
2016 Finger Lakes Regional: Semifinalist on Alliance 7 (1128, 2010, 578)
2016 NYC Regional: Finalist on Alliance 3 (3419, 578, 3017), 4th seed team, Team Spirit Award
2015 Finger Lakes Regional: 8-3-0 in qualification, 7th seed, Quarterfinalist
2014 NY Tech Valley Regional: 8-4-0 in qualification, 13th seed, Semifinalist
2013 Finger Lakes Regional: 4-5-0 in qualification, 26th seed, Alliance 6, 1-2 in tournament
2012 Buckeye Regional: Gracious Professionalism Award, 7-3-0, 14th seed
2011 Finger Lakes Regional: Engineering Inspiration Award
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