Quote:
Originally Posted by Tom Line
One item to consider with the nonadrive is that even on flat ground you will VERY likely want your center wheel to still be actuated by a pneumatic cylinder.
There is a reason stools usually have 3 legs. Having a 4 legged stool is more difficult. From experience (we attempted a solid 6 wheel rectangular drivetrain in '08 with all omnis), having your corner wheels and the middle wheel all touch if they are fixed is nearly impossible. This is why you must have pneumatics - if you rock on the center sideways drive wheel you will end up going in circles. It needs to push against the floor, but not with enough force to actually support the robot. That means some sort of suspension is required...
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This gave us major steering problems back in Overdrive as well. (In Lunacy we
went with it.) That whole "3 [noncollinear] points define a plane" thing means extra contact points need to be somewhat forgiving. As pointed out, life isn't perfect even if your chassis somehow is. How you address that is up to you, whether suspension or actuation (or even somehow in driving), etc, but I would recommend addressing it. Not that this would necessarily add an unacceptable (or even particularly significant) level of complexity.