Damper system to be used in studies of payload isolation technology is suitable as a laboratory apparatus. It provides easily adjustable damping and acts as multichannel shaker system

Chang, C. S.

English

NASA Technical Reports Server

'October 1975	 B75-10259 
NASA TECH BRIEF S	
Langley Research Center 
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 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Two-Directional Active Damper 
.
The active damper system shown in Figure 1 is to be 
used in studies of payload isolation technology and for 
the investigation of related dynamic control problems. 
Because of weight and power consumption considera-
tions, the active damper is probably not suitable for 
full-scale applications. As a laboratory apparatus, 
however, it appears to be versatile and useful in a 
number of ways. It provides easily adjustable 
4amping and, simultaneously, acts as a multichannel 
shaker system. 
The active damper consists of a permanent magnet 
assembly, an armature with four flat planar coils, a 
relative velocity sensor, and a suspension system. The 
key element is the armature windings. The magnetic 
field between the parallel flat pole faces of the primary 
field magnet is almost uniformly distributed and has a 
distinct outline which is nearly the same as that of the 
pole faces. The flux lines are normal to the pole faces 
and are approximately straight. The armature coils 
are located partially between the pole pieces. 
The region of appreciable magnetic field for the 
armature coil assembly is as shown inside the dashed 
boundary of Figure 2. The pair of coils a and c must 
be used in unison. When electrical currents of equal 
magnitude, 'ac' pass through these two coils, equal 
and opposite forces are generated on the armature 
and on the magnet. The direction of the resultant 
force, rae, acting on the armature due to the currents 
in coils a and c is illustrated. The magnitude of this 
force is proportional to the instantaneous magnitude 
Of 'ac 
Coils b and d are used in the same way except that 
the direction of the resultant force, Fbd, generated by 
them is always perpendicular to Fac . Consequently, 
both the magnitude and the direction of the resultant
Permanent Magnet Assembly
Armature 
Armature 
Suspension
	
^_. 	 Sensor Cable
Velocity-Armature Sensor Suspension .  Magnet Flexure 
Base Frame
' Suspension
	
Payload	 Diamond Frame 
IJ6	 J6\ Payload 
	
Simulation	 and Cables 
Figure 1. Active Damper Installation System 
force (r = Fac + Fbd) can be controlled by the 
magnitude, phase, and direction of currents 'ac and 
1bd. 
In order to use the electromagnetic actuator as an 
active damper, the resultant force must be controlled 
and made proportional to the relative velocity between 
the armature and the field magnet. This is 
accomplished with the two-directional relative velocity 
sensor shown schematically in Figure 3. The 
secondary field magnet is rigidly attached to the 
primary magnet. The search coils are mounted on and 
move with the armature plate and act as a dc 
generator. The open-circuit output voltage, e, is 
proportional to the relative velocity between the 
secondary field magnet and the search coil. 
The design arrangement is such that the output ea 
of the search coil, a, is proportional to the instantane-
ous relative velocity component Va in the direction a 
.
(continued overleaf) 
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=19750000259 2020-03-19T20:15:10+00:00Z
Direction p 
Direction a 
Coil a 
Outline of
	
7Fac 
Pole Face	 ac
Coil d-	 ''	 Coil  
\T ,2Coilc 
Figure 2. Curent and Force Components in

Armature Coil Assembly 
earch coil 13 and	 Notes: shown in Figure 2. The operation of s 
the armature coils b and dis similar. The combina-
tion of the actuator and the velocity sensor makes it 
possible to generate damping forces in any direction 
Coil 3	 Coup ¶ 
1 
I	 I 
ep	 I	 I	 ep
Outline of  
Pole Face 
Front Side of Printed-wiring Board 
[	 ea	
]Coila 
r --
I	 I 
Direction LL
a	
ea	
JCoil ___] 
Back Side of Printed-wiring Board 
Figure 3. Two-Dimensional Relative-Velocity-Sensor Schematic 
in the plane of the armature plate. This system can 
provide damping for two translational modes and for 
two rocking modes (e.g., pitch and yaw modes when 
they coincide with the principal coordinates of the 
system). During tests, it has provided up to 30 percent 
damping. 
B75-10259
1. Further information is available in the following 
report: 
NASA CR-132550 (N75-14808), Study of Provid-
ing Omnidirectional Vibration Isolation to Entire 
Space Shuttle Payload Packages 
Copies may be obtained at cost from: 
North Carolina Science & Technology 
Research Center 
P. 0. Box 12235 
Research Triangle Park, North Carolina 27709 
Reference: B75-10259 
2. Specific technical questions may be directed to: 
Technology Utilization Officer 
Langley Research Center 
Mail Stop 139-A 
Hampton, Virginia 23665 
Reference: B75-10259 
Patent status: 
Inquiries concerning rights for the commercial use 
of this invention should be addressed to: 
Patent Counsel 
Langley Research Center 
Mail Stop 313 
Hampton, Virginia 23665 
Source: C. S. Chang of
New Technology, Inc.

(LAR-11815) 
Categories: 06 (Mechanics) 
03 (Physical Sciences) 
02 (Electronics Systems) 
Direction p 
ep = KvVp 
ea = KvV0
C 
.


Two-directional active damper

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