This is an excellent capability Erin. You and the team should get an award from SPIE/Optica for this. It’s a major step forward from the prior art in this area. - Mark

It really is.  One of the customers who was heavily involved in the development had his graduate students doing this translation to coordinate breaks by hand.  We did it for them.    

Seriously, though, the ability to automatically put the RBMs in Coordinate Breaks is ridiculously useful.  Users can exercise the tilt & decenter values to quickly explore performance in the presence of better or worse temperature changes, among other things.  I would always ask for FEA data at two temperatures, so I can assume linear relationships and take a guess at system performance versus temperature.  And plan things like the focus adjust needed in the best-case scenario versus worst-case scenario.  And where to put the focal plane at room temperature so that it is centered on-orbit, best case and worst case.  This is super-powerful stuff.

Erin,

Great work this write-up series has been very helpful.  I had a question about the calculated RBM’s…

When observing the RBMs in the Structural Data Summary, which coordinate reference are they provided in?  The global or local coordinate reference based on the component?  

I have a non-axial symmetric system with coordinate breaks, so I’m wondering if I need to do coordinate transformations if I want RBMs in reference to the global coordinate reference.  (I hope not!)

-Jeff 

Hi, Jeff.  Thanks!  I’m always glad to hear that our content is useful.

I’m pretty sure that all RBMs are reported in local surface coordinates.  We always work in local, behind the scenes.

That said, I wonder if there’s a fairly simple workaround.  The problem is that you probably have allowed motions of the part in global coordinates, right?  So…. use CBs to move a dummy to your global coordinates, and set that as the Global Coordinate Reference Surface in the System Explorer / Aperture. 

If you just need to retrieve the global part position, you can move the part locally and retrieve the global coordinates using Analysis/Reports/Prescription Data / Global Coordinates, or using GLCX|Y|Z|A|B|C in the Merit Function Editor.

If you have allowed motions for the parts in global coordinates, then you don’t know the values that are needed in the local Coordinate Breaks.  But you could optimize to find those.  If you put the desired position change into the Merit Function Editor using GLCX|Y|Z|A|B|C, and set the local coordinate break X|Y|Z|A|B|C values to be variables, you can optimize to figure out the local coordinate values that you need.  You might run into some trouble handling the Z coordinate in the thickness column with this technique.(?)  And make sure that the pickups and order flag are all set properly in your local Coordinate Break pair before you start, so that the local motion of the part is always undone correctly.