Concept permits measurement of the acceleration of continuously rotating shafts without use of slip rings or telemetry and with little additional inertial load. Concept has application in servomotor control circuits and easy-to-fly airplane controls

Smetana, F. O.

English

NASA Technical Reports Server

Voltage 
Proportional Smoothing 
atof	 To Shaft 
Acceleration 
Reset
Flip 
Set	 Flop
March 1973	 B73-10119 
NASA TECH BRIEF 
Langley Research Center 	
-4 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
New Motor Shaft Angular Accelerometer Concept 
Magnetic 
Poles
Disc Attached 
To Shaft By 
Disc Attached 
Rigidly To Shaft 	
1aTorsjonal Spring 
Accelerometer 
Shaft 
Pick Up 
Coils
A new concept permits the measurement of the 
acceleration of continuously rotating shafts without 
the use of slip rings or telemetry and with little 
additional inertia load imposed on the motor. This 
concept has application in servomotor control circuits 
and is being considered for use in easy-to-fly airplane 
controls. 
The design of this accelerometer involves mounting 
two equal diameter cylindrically shaped masses (discs), 
one fixed and one free, side-by-side on the motor shaft. 
Permanent magnet poles are mounted on the outer 
surface of each mass. Pickup coils, opposite the masses, 
are mounted in the instrument case. When the shaft 
turns, the magnets induce a voltage pulse into the coils. 
The induced voltages are fed into control circuitry to 
obtain a steady voltage proportional to shaft accelera-
tion. 
The device is shown schematically in the illustration. 
The accelerometer shaft is rigidly connected to the 
motor shaft. A disc is securely mounted on the acceler-
ometer shaft and contains one or more permanent 
magnets. A second disc is freely mounted on the 
accelerometer shaft adjacent to the first disc and is
connected by a torsional spring of known spring 
constant. This second disc is the same diameter as the 
first and mounts the same number of magnets. 
A case is fixed around the shaft and discs. This case 
contains one or more pickup coils mounted opposite 
each disc. A voltage pulse is induced into these coils 
whenever the motor shaft turns and the magnets pass 
under the coils. The signals from the coil adjacent to 
the fixed disc are fed into the set terminal, and the 
signals from the coil adjacent to the spring-restrained 
disc are fed into the reset terminal of a flip-flop circuit. 
The ON time of the flip-flop is proportional to the 
acceleration. By smoothing the flip-flop output signal 
through an integrator, a steady voltage is obtained which 
is proportional to the acceleration of the motor shaft. 
The relative displacement between the fixed disc and 
the spring-restrained disc is dependent upon spring 
constant, disc inertia, and acceleration of the shaft. 
Since spring constant and disc inertia are known con-
struction parameters, shaft acceleration can be de-
termined by sensing the displacement between the two 
discs.
(continued overleaf) 
This documentwas 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=19730000119 2020-03-17T06:45:45+00:00Z
Note: 
No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Langley Research Center 
Mail Stop 139A 
Hampton, Virginia 23665 
Reference B73-10119
Patent status: 
NASA has decided not to apply for a patent. 
Source: F. 0. Smetana of

North Carolina University

under contract to
Langley Research Center

(LAR-1 1030)
. 
B73-10119
	
Category 02, 06


New motor shaft angular accelerometer concept

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