Device Concept

A kinetic coefficient of friction is always lower than the static one.  This difference may be utilized to provide motion of one bearing mounted (rotating or sliding) component in relation to a moving prawl which pushes when moved slowly (in static mode) or slips when pulled rapidly (in kinetic mode).  The resulting motion can be made fine in resolution, down to some tens of nanometers per stroke, at the contact surface.  The motion can be realized in either direction by reversing the direction of the high speed vs. the low speed stroke.  The motion, although finely resolved, is not true "step" motion, and is only repeatable in a stochastic sense. This type of prime mover offers much in cryogenic applications, where greases and oils freeze.  Bearing surfaces of engineering plastics such as Vespel (TM) perform well in this application, and are wholly suitable for the friction prawl on this type of drive.

The Inventors and Developers

Concept & Design: Robert Chave & Chris Lindensmith
Motor Development: Jason Graetz, JPL / Caltech
HTSC Coil Development John Voccio, America Superconductor


NASA Tech Brief & New Technology Award
NASA New Technology Award, NPO-20275: "Filter Wheel for Use at Cryogenic Temperatures from 4 K to 77 K and at Room Temperature with High Resolution and Simple, Low-heat Load, Magnetostrictive Actuation Systems with Polycrystalline Actuator." 1998

Patent Claims
United States Patent entitled " Magnetostrictive Actuation", Serial Number 09/183,387, R. Chave, C. Lindensmith, J. Dooley, B. Fultz, and M. Birsan, Application filed, Oct. 29, 1998 claiming the benefit of U.S. Provisional Application No. 60/063, 991, filed Oct.  29, 1997

The photo above shows a rotary motor running at the
bottom of a dewar of liquid helium.  The cylinder is an
Etrema Corporation linear actuator casing designed for
room temperature use, employing low temperature TbDy
actuator materials. The small disk in the center is the
driven component.

Photo Robert Chave