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Joined: Thu Dec 01, 2011 12:07 am
Posts: 151
A few have asked for help with arm control lately. I would like to suggest an approach that may seem unusual at first but will allow you to reap many benefits later in your current project and your next project as well.
Begin by giving the arm a known and easily located start position. This may be against a stop or sensor.
On your first scan or variable init phase set the encoder position to zero at this start position.
One variable in your program will be the desired position of the arm.
Use the joystick to incrementally change ONLY the desired position.
Use a simple closed loop position control to adjust the actual position to the desired position.
This also allows autonomous position setpoints and push button control to go to setpoints in lieu of only joystick motion control.
You could also write the desired and actual positions to the display to help debug.

Good luck

Wed Nov 27, 2013 1:16 pm
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Joined: Sat May 18, 2013 1:24 pm
Posts: 271
Location: Olympia, WA
Another point: Usually gravity affects arm designs a lot, which means you'll probably have to PID the position of the arm to stop it from drooping/slipping. And a velocity PID would also benefit intuitive-ness. :)

FTC Team 6424, the 'Oly Cow - Chief programmer.
FRC Team 4450, Olympia Robotics Federation (ORF).

and also quadrotors. Quadrotors!

Wed Nov 27, 2013 10:24 pm
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