Re: To turn or not to turn

[Tim Vanderhoek <vanderh@ecf.utoronto.ca>]

On Sat, Nov 13, 1999 at 03:13:20PM -0500, Joyce Poon wrote:
> 
> Non-Turning:
> 	The direction of the wheels changes in the robot (sort of like
> dry-steering in driving) and the robot just moves in the new
> direction.

Joyce is thinking from the perspective of an observer watching the
robot in a time-independent environment.

Tim is thinking from the perspective of an observer watching the robot
in a time-dependent environment.

In a time-independent environment, the only way to determine the
direction of the robot is from a non-symetrical physical feature (eg.
the front bumper of a car).  Our robot does not necessarily have
any non-symetrical physical features, save for the wheels.....  (which
are still 180degree symetrical).

In a time-dependent environment, the direction of the robot can be
determined from its past motion.  The front of the robot is the
direction it was last travelling in.  By this definition, a robot that
cannot turn can only face one of two directions (assuming its drive
motors can work in either direction).

I know you were at least partly onto the idea of non-turning robots in
a time-independent environment while we were all still together on
Friday, so don't pretend it was this brainstorm idea you had on your
own.  :-)


-- 
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