Detector flake located parallel to a slotted mask mechanical differentiator, senses the rotation of a gimballed reaction wheel mounting. As the gimbal moves light passes through the mask and strikes a section of the detector, the electrical output of which has been calibrated in terms of degrees of rotation

Zaremba, J. G.

English

NASA Technical Reports Server

August 1968	 Brief 68-10315 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Gimbal Angle Sensor 
fl
Sensors for detecting the angular movement of rota-
tion elements are usually very long (if detection is 
linear) or expensively shaped (if detection is to be 
angular). In the development of a gimbaled reaction 
wheel mounting, limitations on space and weight pre-
cluded using state-of-the-art methods for sensing gim-
bal rotation. Instead, a mechanical differentiator is 
slotted so that the first derivative of the radius vector 
with respect to the rotation angle is a constant. Thus, 
as light passing through the slot strikes the detector, 
the relative position of the spot on the surface of the 
detector is a direct measure of angular displacement. 
The system incorporates a standard light source 
and a commercially available photoresistive element. 
Rather than using optical collimation, the innovator 
designed a rectangular light channel that is lighter and 
more effective. The mechanical differentiator is a 
slotted mask contoured to produce the constant noted 
above. It is mounted about the axis of rotation of the 
gimbal. The detector flake is located parallel to the 
mask (about three inches from the center of rotation) 
with its active surface aligned along a radius vector 
originating at the center of rotation. Most angular 
motion detectors are mounted perpendicular to the 
radius vectors
As the gimbal moves, light passes through the mask 
and strikes a section of the detector, the electrical out-
put of which has been calibrated in terms of degrees 
of rotation. The system has a coarse range of from 
zero to ± 27° and a fine range of from zero to ±7° 
with accuracies to ± 0.6°. Also, the need for logic 
circuitry in the electronics portion of the system is 
reduced considerably. 
Note: 
Inquiries concerning this innovation may be 
directed to:
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland 20771 
Reference: B68-10315 
Patent status: 
No patent action is contemplated by NASA. 
Source: J. George Zaremba 
of TRW Systems Group, TRW, Inc. 
under contract to 
Goddard Space Flight Center 
(GSC-10305) 
Category 01 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of -the United States 	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19680000315 2020-03-12T06:13:42+00:00Z


Gimbal angle sensor

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