Robotics Reference
In-Depth Information
been told to locate. (If not, the part would be thrown back into the “sea”
and another part picked up and examined in the same way, and so on,
until the correct part was found.)
Having found the part it was looking for, the machine would then
start on its search for the next part that it needed, as determined by the
program stored in its memory. The machine would continue following
the instructions to make something, without really understanding what it
is doing. When it finished executing its program the machine would have
produced a physical duplicate of itself. But this newly-minted machine
would not yet have any program in its memory, so the “parent” machine
would copy its own program, from its own memory, into the memory
of its offspring, and then, finally, the original machine would start up
the program residing in its progeny. This whole process, as described by
von Neumann, is logically very close to the way that living organisms
reproduce themselves.
Self-Reproducing Software and Genetic Programming
Although this chapter employs the word “robot” generically to repre-
sent either hardware or software (or the combination of both), let us
briefly revert to the traditional distinction between the two, and before
we discuss self-reproducing robots (the hardware) let us first consider self-
reproducing computer programs, a subject given a detailed exposition by
John Koza.
Computer programs that can reproduce do so by combining parts
from two parents and improving their performance through evolution.
A clever example of self-reproducing programs was written by Thomas
Ray at the University of Oklahoma. Ray's 80-line program demonstrated
how it could evolve over time as a consequence of mutation. Ray wrote
his program in a special programming language (Tierra) for a virtual ma-
chine. His virtual machine was intentionally imperfect and introduced
random mutations to his original hand-written program (called the an-
cestor). Ray observed the emergence, over a period of hundreds of mil-
lions of time steps, of an impressive variety of different entities (some
self-reproducing, some parasitically self-reproducing, some symbiotically
self-reproducing, and some not self-reproducing) and a dazzling array of
biological phenomena including parasitism, defences against parasitism,
hyper-parasitism, symbiosis, and social parasitism.
