🚀 go-pugleaf

In article <GERRY.93Jan8231255@onion.cmu.edu> gerry@cmu.edu (Gerry Roston) writes:
>The
>question of using small robots versus large ones is almost a religious
>question.  The greatest failing of those proposing small robots is the
>naive assumption that using multiple, small robots increases overall
>system reliability.  This is not true because one can not assume a
>priori that the failure modes are independent.  That is, if the robots
>are identical, and one of them fails in a particulr manner, this
>implies that the others will also be prone to that particular failure
>mode.

I'm impressed with what the Ambler group has accomplished, and very
impressed with what the Erebus group accomplished in a very short
amount of time.  I think they deserve a great deal of credit, despite
the unfortunate glitch that ended the test.

That having been said, I'll have to come down on the "small rover"
side of the debate.  (I'll admit to being biased, since I spent a
summer working with the JPL microrover group.)

The failure modes may not be independent, but at least the failure
occurrences are.  Suppose there is a 10% chance that a certain failure
will render a robot immobile sometime during its lifetime.  If you
have a single large rover, you have a 10% chance of losing the rover.
If you have ten microrovers, you will probably lose one, but you only
have a 1% chance of losing all ten of them.

The other advantage of multiple rovers is the ability to obtain data
from several sites at different locations on the surface of Mars.

>From a technical viewpoint, the major drawback to small robots in
>telemetry.  To transmit a signal from Mars, you need a moderately
>large antenna and a bunch of power, if you want reasonable data rates.

How about putting a satellite in Mars orbit and using it as a relay
between the rovers and Earth?  Would that solve this problem?

It seems to me that the primary disadvantage with small rovers is
their inability to carry large scientific payloads.  My opinion is
that this disadvantage is outweighed by the advantages above, but I
suppose it depends upon one's particular interests in research and
exploration.
--
_______________________________________________________________________________

Brian Yamauchi			Case Western Reserve University
yamauchi@alpha.ces.cwru.edu	Department of Computer Engineering and Science
_______________________________________________________________________________