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Originally Posted by fritzdejongh
I believe Ether is right. I think you can see the "extra" force as coming from the sideways forces holding the wheels together (these forces must be there, or the wheels would fly apart). This force also gets reduced to the component along the roller, which then has a forward component.
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It might be a bit more accurate to state it thus: the torque applied to the wheel creates a force along the axis of the roller. This force can be split into forward and sideways components for sake of analysis.
In the case of the 45 degree rollers mentioned in my prior post...
http://www.chiefdelphi.com/forums/sh...5&postcount=50
... the force created by the 40 in-lbf drive torque on the wheel creates a force of 10*sqrt(2) along the roller axis.
The force is 10*sqrt(2) because the wheel is constrained from moving sideways by the counter-balancing sideways force from the wheel on the other side of the bot.
This 10*sqrt(2) force can be split into forward and sideways components of 10 pounds each.
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The bottom line is, if nothing is slipping sideways, the full torque is being converted to a forward force.
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If the command is forward on all 4 wheels and the robot is not moving, yes. We haven't yet discussed the case where the robot is moving forward.
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