OCCRA
Go to Post Bottom line: if it confuses my mom, it is bad for FIRST. - Joe Johnson [more]
Home
Go Back   Chief Delphi > Technical > Programming
CD-Events   CD-Media   CD-Spy   FRC-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Closed Thread
Thread Tools Rate Thread Display Modes
  #1   Spotlight this post!  
Unread 03-20-2012, 07:51 PM
IndySam's Avatar
IndySam IndySam is offline
Registered User
FRC #0829 (Digital Goats)
Team Role: Mentor
 
Join Date: Nov 2005
Rookie Year: 2004
Location: Indy
Posts: 3,049
IndySam has a reputation beyond reputeIndySam has a reputation beyond reputeIndySam has a reputation beyond reputeIndySam has a reputation beyond reputeIndySam has a reputation beyond reputeIndySam has a reputation beyond reputeIndySam has a reputation beyond reputeIndySam has a reputation beyond reputeIndySam has a reputation beyond reputeIndySam has a reputation beyond reputeIndySam has a reputation beyond repute
Something other than PID

We use a shooter that is different than most of the robot out there. We call it a fling-a-pult. It is extremely accurate but looses force as battery voltage is reduced causing us to be short sometimes.

Unlike the standard wheeled shooters our two fisher price motors only run for a fraction of a second so PID really doesn't work. What we need is a good way to simply adjust the voltage applied to the shooter motors in accordance with the reduction in battery voltage.

We are using java, any good ideas.
__________________
"Champions are champions not because they do anything extraordinary but because they do the ordinary things better than anyone else." óChuck Knoll


2012 Boilermaker Engineering Excellence Award
2010 Boilermaker Rockwell Innovation in Control Award.
2009 Buckeye J&J Gracious Professionalism Award
2009 Boilermaker J&J Gracious Professionalism Award
2008 Boilermaker J&J Gracious Professionalism Award
2007 St Louis Regional Winners
  #2   Spotlight this post!  
Unread 03-20-2012, 07:57 PM
Tom Bottiglieri Tom Bottiglieri is offline
Custom User Title
FRC #0254 (The Cheesy Poofs)
Team Role: Engineer
 
Join Date: Jan 2004
Rookie Year: 2003
Location: San Francisco, CA
Posts: 3,013
Tom Bottiglieri has a reputation beyond reputeTom Bottiglieri has a reputation beyond reputeTom Bottiglieri has a reputation beyond reputeTom Bottiglieri has a reputation beyond reputeTom Bottiglieri has a reputation beyond reputeTom Bottiglieri has a reputation beyond reputeTom Bottiglieri has a reputation beyond reputeTom Bottiglieri has a reputation beyond reputeTom Bottiglieri has a reputation beyond reputeTom Bottiglieri has a reputation beyond reputeTom Bottiglieri has a reputation beyond repute
Send a message via AIM to Tom Bottiglieri
Re: Something other than PID

Run a few batteries down to varying levels of charge.
Find the right speed control value that will do the trick for that voltage and interpolate in between.

GetBatteryVoltage() lives in the DriverStation class.
  #3   Spotlight this post!  
Unread 03-20-2012, 08:00 PM
jspatz1's Avatar
jspatz1 jspatz1 is offline
Registered User
AKA: Jeff
FRC #1986 (Team Titanium)
Team Role: Mentor
 
Join Date: Jan 2008
Rookie Year: 2007
Location: Lee's Summit, MO
Posts: 765
jspatz1 has a reputation beyond reputejspatz1 has a reputation beyond reputejspatz1 has a reputation beyond reputejspatz1 has a reputation beyond reputejspatz1 has a reputation beyond reputejspatz1 has a reputation beyond reputejspatz1 has a reputation beyond reputejspatz1 has a reputation beyond reputejspatz1 has a reputation beyond reputejspatz1 has a reputation beyond reputejspatz1 has a reputation beyond repute
Send a message via AIM to jspatz1 Send a message via Skype™ to jspatz1
Re: Something other than PID

Your battery voltage reading is available in software, and can be used to inversely adjust the power to your shooter. See this post: http://www.chiefdelphi.com/forums/sh...69#post1137469
__________________
  #4   Spotlight this post!  
Unread 03-20-2012, 08:03 PM
DjMaddius's Avatar
DjMaddius DjMaddius is offline
Registered User
AKA: Matt Smith
FRC #2620 (Southgate Titans)
Team Role: Programmer
 
Join Date: Jan 2010
Rookie Year: 2009
Location: Southgate, Mi
Posts: 161
DjMaddius is an unknown quantity at this point
Re: Something other than PID

From what it sounds, you'll need to create a ratio of motor speed to battery voltage then apply this to what speed you really want. Obviously, the easiest way would be to add an encoder and use that to adjust motor speed but in some circumstances it is very difficult to mechanically get one on where you need it.
  #5   Spotlight this post!  
Unread 03-20-2012, 10:02 PM
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 6,031
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: Something other than PID

Quote:
Originally Posted by IndySam View Post
We use a shooter that is different than most of the robot out there. We call it a fling-a-pult. It is extremely accurate but looses force as battery voltage is reduced causing us to be short sometimes.

Unlike the standard wheeled shooters our two fisher price motors only run for a fraction of a second so PID really doesn't work. What we need is a good way to simply adjust the voltage applied to the shooter motors in accordance with the reduction in battery voltage.

We are using java, any good ideas.
If you are using Jag controllers via CAN, there is a voltage command mode.

You command the desired voltage, and the Jag automatically adjusts the output PWM duty cycle to give you that desired voltage, regardless of the supply voltage. Unless, of course, the supply voltage is less than the commanded voltage.


Closed Thread


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 02:08 AM.

The Chief Delphi Forums are sponsored by Innovation First International, Inc.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi