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Unread 02-04-2008, 06:58
Jimmy Cao Jimmy Cao is offline
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Re: Swerve drive 4, 2+2?

Quote:
Originally Posted by Sgreco27 View Post
If all of your wheels are moving indepentently then you have all the capability of a 2+2 and more, using a 2+2 you have all the capability of a 4 and more. I would consider that none of these are any more complex than the others and go with each module being moved indepentently. An easy way to make this work is to vertically mount an FP motor and attach it to the wheel module and do this to all of the modules. Make sure the wheels are straight when you start a match because if they are a little off it can mess up hybrid mode. My team ran into this issue, it wasn't that bad in tele op but we had a good hybrid mode, but if the wheels weren't perfectly aligned the robot would cross one line and before it could get a second teh unstraightenedness would make it go into a wall.(it didn't help that our sonars died in eliminations)
A 2+2 system with dependent steering and drive is a lot simpler than a fully independent system. On a fully independent system, you would need to do feedback on 4 modules instead of 2. That means another 4 PIDs (2x forward 2x reverse). It also makes the precise control logic a lot more complicated.

A big challenge for us in previous years was to pack both the motor and any transmission inside the module itself, so we do not suffer efficiency loss through use of bevel gears. That, IMO, was one of the biggest challenges for us in these years. Additionally, remember it is vital to keep the wheel base as large as possible, and therefore, the modules as small as possible.
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Jimmy Cao

Team 469 2006-2010 Student/Alumni
Team 830 2011-2012 Mentor