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Unread 03-04-2002, 21:37
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kmcclary kmcclary is offline
Founder 830/1015;Mentor 66/470/1502
FRC #0470 (Alpha Omega Robotics)
Team Role: Engineer
 
Join Date: Aug 2001
Rookie Year: 1994
Location: Ann Arbor, MI
Posts: 491
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Re: Correction for arm

Quote:
Originally posted by skyfw
I've now decided to write a correction into our arm from last year, because when we drove it at parent teacher Conferences, the new kids on the team nearly destroyed the arm due to it's tendency to move quickly and have a high angular momentum. [...]
You've said a couple of different things here. (1) you wish to "write a correction" apparently to slow it down, and (2) talking about changing things from however you're doing things now to a pot feedback system.

The first is simply "slew limiting" (controlling maximum speed) to make it more controllable, but the other involves changing things to a feedback control setup (servo / PID loop).

Please describe your current control setup in more detail. Tell us how it behaves now, and exactly how you want it to behave. You said: "I know in my head, how to do it mathematically".. Feel free to spell out what you want that way (and how that differs from current behavior).

Given that, we can then discuss in more detail which solution would be best for you.

Remember the KISS principle. PIDs are cool, but you may not NEED a servo setup, and if the pot or its wiring/connector breaks (and you've left out limit switches and manual overrides), you've got bigger problems. Simply gearing things down, using a Max_Time_On counter variable, or programming a speed ramp up&down curve might be better and more reliable. Gearing down limits your top speed and gives you more power for stopping right there.

(BTW... the robot pic link doesn't work...)

- Keith
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Keith McClary - Organizer/Mentor/Sponsor - Ann Arbor MI area FIRST teams
ACTI - Automation Computer Technologies, Inc. (Sponsoring FIRST teams since 2001!)
MI Robot Club (Trainer) / GO-Tech Maker's Club / RepRap-Michigan) / SEMI CNC Club
"Certifiably Insane": Started FIVE FRC teams & many robot clubs (so far)!
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