Motion drive system has been developed for use with interferometers where accurate control of minuscule distance in the 1-micron range is of prime importance. The drive system is applicable to any device that requires extremely accurate positioning control

Morecroft, J. H.

English

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December 1966	 Brief 66-10695 
NASA TECH BRIEF . 
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from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Motion Drive System is Accurately Controlled in the 1-Micron Range 
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The problem: 
To develop a motion-drive system for use with 
interferometers where accurate control of minuscule 
distance in the I-micron range is of prime importance. 
The new drive system must also be adaptable for use 
with other precision devices. 
The solution: 
A motion drive system in which incremental motion 
is obtainable in varying increments of from several 
inches to a fraction of a micron. 
How it's done: 
The drive system can be implemented as a func-
tional addition to a simple, continuous-motion, lead-
screw to produce a controlled incremental motion of 
the driven element. Since the motion imparted to the 
driven element is the resultant sum of continuous 
motion and transducer movement, it is possible to 
hold the driven element motionless or move it at
speeds in excess of that of the continuous motion 
system. By alternating these two conditions, through 
appropriate electrical input to a transducer, incre-
mental motion of the driven element is realized. 
In the drive system, an electromechanical trans-
ducer (electromagnetic, electrostatic, piezoelectric or 
magnetostrictive) is interposed between the point of 
continuous motion and the element to be incremen-
tally driven. The electrical signal to the transducer 
produces motion within the transducer equal and 
opposite to that of the continuous motion within the 
total drive system. For the duration of the electrical 
signal, and within the physical limitations of the 
transducer, there is no motion at the output of the 
drive system. Repeated occurrence of this effect pro-
duces the desired incremental driving action. The 
electrical signal to the transducer can be produced 
either by a suitable generator or from a sensor as-
sociated with the mechanical action of the drive sys-
tem, resulting in a servo-type operation.
(continued overleaf) 
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Notes: 
1. The drive system is applicable to any device that 
requires extremely accurate positioning control. 
The system is generally applicable to those classes 
of instruments in which a movable element is 
used to alter the instrument's characteristics in such 
a fashion as to result in significant variations of 
an observable effect. Although described in terms 
of linear motion, the same technique is applicable 
to angular motion. Therefore, interferometers, 
refractometers, diffractometers, and scanning-type 
instruments can be utilized with the drive system.
Inquiries concerning this invention may be di-
rected to:
Technology Utilization Officer 
Jet Propulsion Laboratory 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference; B66-10695 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546.
Source: J. H. Morecroft 
(JPL-864) 
Brief 66-10695	 Category 05


Motion drive system is accurately controlled in the 1-micron range

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