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Posted by Joe Johnson.   [PICTURE: SAME | NEW | HELP]


Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.

Posted on 2/29/2000 5:10 AM MST


In Reply to: Excuse me?? posted by Keith Liadis on 2/28/2000 6:40 PM MST:



As a rigid object travels through space, it always has an 'instant center,' a theoretical point about which it is rotating.

For instance, if a machine is traveling straight ahead, its instance center is at infinity to the left (or right -- same point in instant center math).

Another example, if a machine is traveling in a curved path to the right, then the instant center is somewhere to the right of the machine.

Yet another example, if a machine is spinning about its center, then the instant center is in the center of the machine.

The important thing for this discussion is that if a machine has two non-steerable wheels whose axles are in a straight line and the tires do not slip with respect to the ground, then the instant center of a machine is always on the line passing through the two wheels.

This is what I will call 'non-arbitrary' instant center positioning, in that the instant center can ONLY be on the line described by the two wheels.

What if, for example, a machine wanted to pivot about a point 5 feet in front if the machine? Not possible with 2 wheels with parallel axles.

But... suppose the wheels were independently steerable. In this case, the wheels could be adjusted so that the lines through the axles of the wheels intersect anywhere on the playing field, for instance, 5 feet in front of the robot. This intersection point is the instant center for the robot.

This is what I will call 'arbitrary instant center positioning.'

Anyway, with such a drive/steering system, improved mobility should result.

Joe J.