View Single Post
  #52   Spotlight this post!  
Unread 03-06-2010, 22:22
apalrd's Avatar
apalrd apalrd is offline
More Torque!
AKA: Andrew Palardy (Most people call me Palardy)
VRC #3333
Team Role: College Student
 
Join Date: Mar 2009
Rookie Year: 2009
Location: Auburn Hills, MI
Posts: 1,347
apalrd has a reputation beyond reputeapalrd has a reputation beyond reputeapalrd has a reputation beyond reputeapalrd has a reputation beyond reputeapalrd has a reputation beyond reputeapalrd has a reputation beyond reputeapalrd has a reputation beyond reputeapalrd has a reputation beyond reputeapalrd has a reputation beyond reputeapalrd has a reputation beyond reputeapalrd has a reputation beyond repute
Re: Most Powerful FIRST Team created T-Shirt Cannon

Why not just have feedback through whatever processor is already on the robot?

Mount the pot and motor (or a sprocket chained to the motor) on the shaft of the cannon. If there is no place for the pot it can be on a sprocket on the motor chain as well. If the shaft is hollow, you can put in a plastic (HDPE, Delrin, etc.) plug with a set-screw for the pot, and mount the pot with a piece of folded sheet metal.

Then, wire the pot to an analog input, and the motor, through a speed controller, to a PWM output.

You can then have fun writing and tuning PID code. If it dosen't have a whole lot of mass to it then P would work fine, if it can't get to the setpoint without overshooting you can add a little bit of I to help it along, and if it has a giant amount of mass (e.g. a big steel pipe) you can add D to help with momentum.
__________________
Kettering University - Computer Engineering
Kettering Motorsports
Williams International - Commercial Engines - Controls and Accessories
FRC 33 - The Killer Bees - 2009-2012 Student, 2013-2014 Advisor
VEX IQ 3333 - The Bumble Bees - 2014+ Mentor

"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack