Nanopositioning equipment manufacturers can follow the latest design rules and put the best components into their mechanisms and controllers, often to no avail.
If the user does not take the time to follow best practices for mounting, figuring out a suitable supporting structure, the right cable draping, and environmental conditions, much of the intrinsic performance can be lost.
After all, any shortcomings of the structure will confer drift, vibration, and instabilities onto the application.
It may seem basic, but we’d encourage even longtime nanopositioning users to read this through. We’ve learned some important lessons alongside some very experienced users; perhaps your application might benefit from some overlooked detail.
To begin, a stable structure means rigidity, flatness, and close mechanical coupling are requirements. Let’s review each of those in turn:
Rigidity / Stiffness: The Higher the Natural Frequency, the Better
- Mounting hardware must be substantial and solid. Massiveness per se isn’t necessarily desirable, as the resonant frequency of the structure goes as sqrt (stiffness/mass), so clearly it is this stiffness-to-mass ratio that should be maximized. So a flanged, triangulated, “I-beam” or boxed supporting element would be preferable to a solid component of the same dimensions or the same mass. (On the other hand, nanopositioning devices in high-dynamic applications need a significant reactive mass to push against — you don’t want to eliminate all mass in the supporting structure.)