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Unread 22-10-2003, 19:32
Unsung FIRST Hero
Al Skierkiewicz Al Skierkiewicz is offline
Broadcast Eng/Chief Robot Inspector
AKA: Big Al WFFA 2005
FRC #0111 (WildStang)
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 1996
Location: Wheeling, IL
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Re: rotation of body of crab drive robots

Quote:
Originally posted by michael_obrien
I'm confused as to how a crab style robot rotates itself entirely (not just wheel modules), I see on the wildstang video page that they have a little foot that comes down to pivot on,
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Basically what I'm asking is how crabs turn and how well it works.
Michael,
A crab drive system does not need to steer to drive. You just point the wheels in the direction you want to go and apply power. Wildstang used the foot this year so as to provide an easy way to reorient the robot to pick up bins or to align with the ramp. There are actually two feet, used one at a time, to achieve the desired effect. The foot raised two wheels off the ground while driving the remaining two in opposite directions. This is not an efficient method but it works when needed. We have used steering in past years that allowed for a different turning radius on one side of the robot than the other. This would give an arc to the robot motion and hence a turn. Max power is still when all the wheels meet the road.
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Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
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Storming the Tower since 1996.