From: "Tom Krajci" 
To: 
Reply-To: "Tom Krajci" 


From: Larry Sayre 

>Here are the numbers:

>Auto Cell Design (answer in a few seconds):
>P/V error = 1.56425e-05, RMS error = 2.50472e-06

>Optimized (~20 minutes of seeking solutions):
>P/V error = 1.65284e-05, RMS error = 2.49876e-06

>Not much difference in the RMS error, but the P/V error looks perhaps
>significantly different....

Looks like approximately a five percent change in P/V.  I don't think I
would call that significant.

>...Differences in the calculated triangle
>placement radii are nill, but all of the triangle dimensions differ by
a
>few mm....

That sounds promising from a 'sensitivity analysis' standpoint.  In other
words...fabrication errors of a mm or two won't really alter the ability of
the cell to support the mirror to calculated tolerances.

>I have no idea if these cell induced error results are
>significant for my design

I recommend you make sure you do a very good job of minimizing slop and
stiction (static friction) in your cell design.  That will help ensure your
cell performs as calculated.  See:
http://overton.tamu.edu/aset/krajci/scope-design.htm  at the very bottom,
and also:
http://overton.tamu.edu/aset/krajci/cell-bearing.htm  perhaps you want to
consider the use of compliant hinges?

Also, you'll need to think carefully about your radial support scheme...RTV
the mirror to the cell...edge sling?...piano wire sling?...double/crossed
piano wire sling?...etc?  Bad design or implementation here can spoil your
mirror cell efforts.

>...(as in should I be seriously considering a 36
>point or 54 point option, neither of which which seem to function in my

>version of PLOP).

David Lewis admitted that he did not finish the 36 or 54 point
capability...if I remember correctly.

Tom Krajci
Tashkent, Uzbekistan


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