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Unread 02-03-2015, 19:28
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Spoam Spoam is offline
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AKA: Pedro M.
FRC #0955 (CV Robotics)
Team Role: Programmer
 
Join Date: Feb 2014
Rookie Year: 2012
Location: Corvallis
Posts: 54
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Re: Elevator Motion Profiling / PID Ramping

Quote:
Originally Posted by AdamHeard View Post
Gear slower. It will do wonders here.
+1 for this. As a team that also uses PID for elevator control (although we mostly use it to minimize the torsional stress caused by our braking mechanism) the first thing we did to get a manageable speed was lower our gearing by a lot. That has the added benefit of providing some resistance against gravity. Worked great, as Adam suggests. It sounds like right now you are unnecessarily fast and you'll get the most out of your motors if you gear slower.

Quote:
Originally Posted by Tom Bottiglieri View Post
Off topic a bit - I saw your team was using Java this year. Have you run into issues with the timing of the JVM's Timer? We have used this construct successfully over the past two years, but on the roborio the timing is complete garbage. We have ditched using derivatives on any control loops due to massive noise.

My best theory is the squawkVM was ported manually and used VXworks timers under the hood. The standard JRE we use now probably just sleeps or something.
Hmm, I'm curious about this. We also use java, but all our mechanisms are currently running PI control. Thank you for pointing this out.
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Last edited by Spoam : 02-03-2015 at 20:14.