3 degrees of freedom trivial

[Avery Andrews 930119.0100]
  re recent Chris Malcom & Bill Powers

When Chris Malcom said that three degrees of freedom were trivial to deal with
(for arms), I understood him to be talking about the kinematics, not the
dynamics. Inverse kinematics for arbitrary multi-joint arms does give
me the impression of being pretty hard, especially if you want to be
sure you understoand how the thing will actually behave. But I'm still
suspecting that the built-in assymetries in the human arm & wiring
make it effectively much more like the arm demo. Consider for example
somebody presented for the first time with a typewriter: Confronted
with a choice of five fingers to use to press the keys, (almost ?)
everybody picks the same one.

  Open Loop Roaches

The 1985 Camhi article also provides a hint as to where Beer got his
open-loop escape claim from: Camhi cites some earlier work showing that
the direction of the turn is computed `open loop', that is, the roach
doesn't turn in one direction, see if it's suitable, if not, turn in
the other. Academic Circumscription strikes again!

Avery.Andrews@anu.edu.au