An apparatus is reported for accurate pointing of instruments on a carrier vehicle and for isolation of the instruments from the vehicle's motion disturbances. The apparatus includes two assemblies with connecting interfaces. The first assembly is attached to the carrier vehicle and consists of an azimuth gimbal and an elevation gimbal which provide coarse pointing by allowing two rotations of the instruments relative to the carrier vehicle. The second or vernier pointing assembly is made up of magnetic suspension and fine pointing actuators, roll motor segments, and an instrument mounting plase which provides appropriate magnetic circuits for the actuators and the roll motor segments. The vernier pointing assembly provides attitude fine pointing and roll positioning of the instruments as well as six degree-of-freedom isolation from carrier motion disturbances

Anderson, W. W.

Groom, N. J.

English

NASA Technical Reports Server

United States Patent 1191 
Anderson et al. 
[111 4,088,018 
WI May 9,1978 
[54] MAGNETIC SUSPENSION AND POINTING 
[75] Inventors: Willard W. Anderson, Yorktown; 
SYSTEM 
Nelson J. Groom, White Marsh, both 
of Va. 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[73] Assignee: The United States of America as 
[21] Appl. NO.: 807,703 
[22] Filed: Jun. 17, 1977 
Related U.S. Application Data 
[62] 
[51] Int. Cl.2 .............................................. GOlC 21/00 
1521 US. Cl. ..................................... 73/178 R; 308/10 
[58] Field of Search ............. 73/178 R, 178 T, 178 H, 
308/10; 244/166; 318/648,649, 653 
~561 References Cited 
Division of Ser. No. 662,182, Feb. 27, 1976. 
U.S. PATENT DOCUMENTS 
3,845,995 11/1974 Wehde ................................... 308/10 
3,875,488 4/1975 Crocker ............................... 318/648 
Primaly Examiner-Donald 0. Woodiel 
Attorney, Agent, or Firm-William H. King; John R. 
Manning; Howard J. Osborn 
Apparatus for providing accurate pointing of instru- 
ments on a carrier vehicle and for providing isolation of 
the instruments from the vehicle's motion disturbances. 
The apparatus includes two assemblies, with connecting 
interfaces, each assembly having a separate function. 
The first assembly is attached to the carrier vehicle and 
consists of an azimuth gimbal and an elevation gimbal 
which provide coarse pointing of the instruments by 
allowing two rotations of the instruments relative to the 
carrier vehicle. The second or vernier pointing assem- 
bly is made up of magnetic suspension and fine pointing 
actuators, roll motor segments, and an instrument 
mounting plate around which a continuous annular rim 
is attached which provides appropriate magnetic cir- 
cuits for the actuators and the roll motor segments. The 
vernier pointing assembly is attached to the elevation 
gimbal and provides vernier attitude fine pointing and 
roll positioning of the instruments as well as six degree- 
of-freedom isolation from carrier motion disturbances. 
[571 ABSTRACT 
6 Claims, 4 Drawing Figures 
14 
/ / / ' \A 
/ 
\ 
\ 
I 
\ 
' \ b, (;." 
\ - \  / 
https://ntrs.nasa.gov/search.jsp?R=19780019481 2020-03-20T13:38:10+00:00Z
U.S.Patent May 9,1978 4,088,018 
FIG. 1 
FIG. 3 
11’ 
FIG. 2 
48 
4,088,018 
rl 1 
MAGNETIC SUSPENSION AND POINTING 
SYSTEM 
ORIGIN OF THE INVENTION 
The invention described herein was made by employ- 
ees of the United States Government and may be manu- 
factured and used by or for the Government for govem- 
mental purposes without the payment of any royalties 
thereon or therefor. 
This is a division of application Ser. No. 662,182, filed 
Feb. 27, 1976. 
BACKGROUND OF THE INVENTION 
The invention relates generally to apparatus for 
pointing the instruments on a carrier vehicle, such as a 
spacecraft, at a selected target and more specifically 
concerns apparatus for accurately pointing the instru- 
ments on a carrier vehicle at a selected target and for 
isolation of the instruments from carrier motion disturb- 
ances. 
Prior devices for pointing the instruments onboard a 
carrier vehicle includes mechanical isolation and torque 
motor pointing. Also, prior concepts have included 
magnetic isolation and pointing but have never used a 
continuous annular rim providing roll control. The 
disadvantages of these prior concepts are that they do 
not provide complete six degree-of-freedom control 
and isolation simultaneously. 
It is therefore the primary purpose of this invention to 
provide complete six degree-of-freedom fine pointing 
and control for carrier vehicle instruments and to pro- 
vide complete six degree-of-freedom isolation of carrier 
vehicle instruments from disturbances on the vehicle to 
which the invention is attached. 
SUMMARY OF THE INVENTION 
This invention includes two assemblies with each 
having a separate function. The frrst assembly is at- 
tached to a carrier vehicle and consists of an azimuth 
gimbal and an elevation gimbal which provide coarse 
pointing of the instruments by allowing two rotations of 
the instruments relative to the carrier vehicle. The sec- 
ond, or vernier pointing assembly, is made up of mag- 
netic suspension and fine pointing actuators, roll motor 
segments, and an instrument mounting plate around 
which a continuous annular rim is attached which pro- 
vide appropriate magnetic circuits for the actuators and 
the roll motor segments. The vernier pointing assembly 
is attached to the elevation gimbal and provides vernier 
attitude fine pointing and roll positioning of the instru- 
ment as well as six degree-of-freedom isolation from 
carrier motion disturbances. In addition, the second 
assembly has a rim centering mode in which axial and 
radial rim position sensors located at each actuator 
station are used to center the rim axially and radially 
between actuator pole faces. This mode allows coarse 
gimbal slewing for re-targeting, for earth pointing or for 
backup coarse gimbal pointing. 
The vernier pointing system includes electromagnets 
working in opposed pairs axially and either singularly 
or in opposed pairs radially to provide fine pointing 
forces on the rim of the instrument mounting plate. The 
command forces originate from rim position sensors 
while in the rim centering mode or from instrument 65 
pointing error sensors for the axial actuators while in 
the vernier pointing mode. The radial actuators can be 
controlled in a manner to reduce the effects of transla- 
5 
10 
15 
20 
25 
30 
35 
40 
45 
50 
55 
60 
L 
tions of the carrier in the radial direction. Roll position- 
ing is provided by a linear non-contacting roll torque 
motor which produces forces tangential to the rim. Roll 
angle is determined from a linear sensor located along 
the periphery of the rim. Also, roll could be controlled, 
in a fine pointing mode, from signals generated by a roll 
sensor on board the experiment package. Thus, it is seen 
that the instrument mounting plate is completely iso- 
lated from the elevation gimbal (no interface connec- 
tion) and the only forces produced on it, as long as the 
electromagnet gaps are maintained, are those produced 
by the electromagnets themselves, in response to com- 
mand signals. 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a schematic diagram of the invention; 
FIG. 2 is a schematic diagram showing the invention 
mounting on a carrier vehicle; 
FIG. 3 is a schematic diagram of the annular rim 
upon which the instruments are mounted; and 
FIG. 4 is a sectional view 4-4 of FIG. 3 with a 
schematic drawing of the electrical connections made 
to the actuator. 
DETAILED DESCRIPTION OF THE 
INVENTION 
Turning now to the embodiment of the invention 
selected for illustration in the drawings, the number 11 
in FIG. 1 indicates a carrier vehicle on which the inven- 
tion is mounted. An azimuth gimbal 12 is attached to the 
carrier vehicle and an elevation gimbal 13 is mounted 
on gimbal 12. These two gimbals allow two rotations of 
an instrument package 14 relative to the vehicle and 
thereby provide coarse pointing of the instruments. 
Instrument package 14 is mounted on a mounting plate 
15 which is magnetically suspended and fine controlled 
by means of a magnetic controller 16. A roll motor 17 is 
mounted on gimbal 13 for the purpose of controlling or 
rotating instrument package 14 about the central axis 18 
of mounting plate 15. 
The apparatus shown in FIG. 1 which is designated 
by the numeral 20 in FIG. 2 is mounted on a typical 
carrier vehicle 11 as shown in FIG. 2. 
Mounting plate 15 and magnetic controller 16 shown 
in FIG. 1 can best be understood by referring to FIG. 3. 
In FIG. 3 there is shown an annular rim 30 that sur- 
rounds the mounting plate 15, not shown. Annular rim 
30 is made from a magnetic material such as iron or a 
composite material including ferrite pieces to provide 
magnetic circuits for the actuators. In this embodiment 
of the invention the magnetic controller 16 includes 
four magnetic actuators 31. However, it is to be under- 
stood that three or more of these actuators can be used 
without departing from the invention. To better de- 
scribe the actuators, a cross section 4-4 of FIG. 3 is 
shown in FIG. 4 along with the electrical circuitry 
connected to the actuators. 
Each of the actuators 31 includes an electromagnet 
40, an electromagnet 41 and an electromagnet 42. For 
the described embodiment of the invention the electro- 
magnets do not use permanent magnets; however, they 
could be used for flux biasing. Electromagnets 40 and 41 
which apply forces to opposite sides of rim 30 are con- 
nected to an amplifier driver 43 which applies a signal 
to each of the electromagnets. The signal is applied to 
electromagnet 40 if the rim is displaced in the direction 
of electromagnet 41 and vice versa. A transducer 44 is 
included with each actuator 31 to produce a signal that 
4,088,018 
3 4 
is proportional to the distance form transducer 44 to the 
annular rim 30. This signal is applied to the amplifier 
driver 43 which applies a signal to electromagnets 40 
and 41 to maintain annular rim 30 in a fmed neutral 
position. A signal can be applied to a terminal 45 which 5 
is added to the signal from transducer 44 by means of an 
adder 46 to control the position of annular rim 31 rela- 
tive to its neutral position. Hence, each actuator 31 suppOrthg said instrument package and mounted on said second gimbal for magnetically includes a magnetic means for magnetically suspending 
controlling the pointing of said instrument package and for providing a fine control in that direction. whereby fine and coarse control of the pointing of 
said instrument package is provided the coarse A transducer 47 is located opposite the end of annular 
control being provided by said first and second rim 30 that produces a signal proportional to the dis- 
gimbals. tance from transducer 47 to annular rim 30. This signal 
is applied to an amplifier driver 48 which applies a 15 wherein said first 
signal to electromagnet 42 to maintain the annular rim gimbal is an azimuth gimbal and said second gimbal is 
in a neutral position. A signal can be applied to a termi- an elevation *bale 
nal49 which is added to the signal produced by trans- 
ducer 47 by rneam of an adder 50 to Control the annular 2o for magnetically suspending and fine controlling the 
rim 30 relative to its neutral position. Hence, each actu- pointing of said instrument package comprises: 
ator 31 includes a magnetic means for magnetically an annular rim made from a magnetic material for 
suspending the rim in a direction perpendicular to axis supporting said instrument package; 
18 (radial direction) and for providing a fine control in several actuator stations located around the periph- 
that direction. It should be noted that if an even number 25 ery of said rim; 
of actuators 31 are used then opposing electromagnets each of said actuator stations comprising: means for 
42 can be connected together electrically. If two of the magnetically suspending said rim at the actuator 
electromagnets 42 are connected together electrically, station in the direction parallel to the central axis of 
then one transducer 47 can be used to control both said rim and for providing fine control in that di- 
electromagnets or two can be used with the average 3o rection; and 
output of the two used to control both eletromagnets. In means for magnetically suspending said rim at the 
either case, a signal is applied to one electromagnet 42 if actuator station in the direction perpendicular to 
the rim is displaced in the direction of the other and vice the central axis of said rim and for providing a fine 
control in that direction whereby the combined versa. 
actuator stations provide a fine control of said in- 
pointing first involves coarse gimbal pointing using strument package in five degrees-of-freedom. 
coarse sensors on board the carrier vehicle and relative 
gimbal angle The rim for turning said rim about said central axis to a selected 
vated during gimbal slewing. After alinement, position whereby fine control of said instrument pack- 
5. Apparatus according to claim 3 wherein said means roll motor and a relative roll sensor located on the rim for magnetically suspending said rim in a direction par- together with a carrier sensor. allel to the central axis of said rim includes first and 
second electromagnets located opposite each other on After coarse attitude alinement, vernier fine pointing 
two sides of said rim; a transducer on one side of said is initiated. For this mode, errors from fine attitude sensors located on the vehicle are nulled by small mag- 45 rim for producing an electrical proportional to its netic suspension and fine pointing actuator torques ap- distance from said rim; amplifier means receiving said plied to the annular rim. Also, translational rim control electrical signal for applying the amplified electrical 
signal to said first and second electromagnets to main- is accomplished for this mode. 
Nominal operation of this invention for earth point- tab rim in a neutral position in said direction paral- 
elevation, and roll attitude and attitude rates (slewing) a control to said electrical whereby a fine 
using the rim centering mode. After appropriate smooth control can be maintained by said control in said 
instrument slewing is established, vernier pointing, simi- direction parallel to the central axis of said rim. 
lar t0 that described for S o h  and Stellar pointing, is 
accomplished. % 55 for magnetically suspending said rim in a direction per- 
Upon Completion Of a pointing task, the COrreCtiOn Of pendicular to the central axis of said rim includes an 
appropriate i n t e r f ~ ~ s  between the Payload mounting electromagnet located opposite the edge of said rim; a 
surface and the assembly takes Place. These inter- transducer located opposite the edge of the rim for 
faces Can be maintained during a Pointing task if the producing an electrical signal proportional to the dis- 
pointing degradation caused by the interface connec- 60 tance of the transducer from the rim; amplifier means 
tion is tolerable. for amplifying said electrical signal and applying it to 
The advantages of this invention are that it provides said electromagnet to maintain said rim in a neutral 
complete six degree-of-freedom fine pointing and con- position in a direction perpendicular to said central axis 
trol for carrier vehicle instruments and it provides com- of said rim; and means for adding a control signal to said 
plete six degree-of-freedom isolation of carrier vehicle 65 electricd signal whereby a frne control can be main- 
instruments from disturbances on the vehicle to which tained by said control signal in said direction perpendic- 
the invention is attached. ular to the central axis of said rim. 
What is claimed is: * * * * *  
1. Apparatus for providing accurate Pointing for 
carrier vehicle instruments and for providing isolation 
from the vehicle comprising: 
a first gimbal attached to and supported by said car- 
a second gimbal mounted on said first gimbal; 
an instrument package; and 
rier vehicle; 
the rim in a direction parallel to a i s  18 (axial direction) 10 said instrument Package and for fine 
2, Apparatus according to 
3. Apparatus according to claim 1 wherein said means 
Nominal operation of the invention for solar or stellar 35 
4. Apparatus according to 
is 
corne roll positioning is accomplished using the rim 4o age is provided in s' degrees-of-freedom* 
ing initially involves establishing the Correct azimuth, 50 lel to the central axis of said rim; and means for adding 
6. Apparatus according to 3 said 


Magnetic suspension and pointing system

Apparatus for providing accurate pointing of instruments on a carrier vehicle and for providing isolation of the instruments from the vehicle's motion disturbances is presented. The apparatus includes two assemblies, with connecting interfaces, each assembly having a separate function. The first assembly is attached to the carrier vehicle and consists of an azimuth gimbal and an elevation gimbal which provide coarse pointing of the instruments by allowing two rotations of the instruments relative to the carrier vehicle. The second or vernier pointing assembly is made up of magnetic suspension and fine pointing actuators, roll motor segments, and an instrument mounting plate around which a continuous annular rim is attached which provides appropriate magnetic circuits for the actuators and the roll motor segments. The vernier pointing assembly provides six degree-of-freedom isolation from carrier motion disturbances

United States Patent 1191 r113 4,156,548 
Anderson et al. [45] May 29, 1979 
[54] MAGNETIC SUSPENSION AND POINTING 3,986,092 10/1976 Tijsma .................................. 318/649 . .  
SYSTEM 
[75] Inventors: 
[73] Assignee: 
[21] Appl. No.: 
[22] Piled: 
Willard W. Anderson, Yorktown; 
Nelson J. Groom, White Marsh, both 
of Va. 
The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
662,182 
Feb. 27, 1976 
[51] Int. c1.2 .............................................. F16C 39/00 
[52] U.S. c1. .................................... 308/10; 73/178 R 
[58] Field of Search .......................... 308/10; 244/166; 
73/178; 318/648, 649, 653 
[561 References Cited 
U.S. PATENT DOCUMENTS 
3,234,444 
3,358,945 
3,480,811 
3,702,208 
3,845,995 
3,875,488 
3,902,374 
3,984,748 
2/1966 
12/1967 
11/1969 
11/1972 
11/1974 
4/1975 
9/1975 
10/1976 
Burmeister ........................... 3 18/649 
Blount .................................... 308/10 
Grosbard ............................... 308/10 
Habermann ............................ 308/10 
Wehde ................................... 308/10 
Crocker ............................... 318/648 
Hoffman ................................ 308/10 
Sullivan ............................... 3 18/648 
Primary Examiner-R. Skudy 
Attorney, Agent, or Firm-William H. King; John R. 
Manning; Howard J. Osborn 
1571 ABSTRACT 
Apparatus for providing accurate pointing of instru- 
ments on a carriet vehicle and for providing isolation of 
the instruments from the vehicle’s motion disturbances. 
The apparatus includes two assemblies, with connecting 
interfaces, each assembly having a separate function. 
The first assembly is attached to the carrier vehicle and 
consists of an azimuth gimbal and an elevation gimbal 
which provide coarse pointing of the instruments by 
allowing two rotations of the instruments relative to the 
carrier vehicle. The second or vernier pointing assem- 
bly is made up of magnetic suspension and fine pointing 
actuators, roll motor segments, and an instrument 
mounting plate around which a continuous annular rim 
is attached which provides appropriate magnetic cir- 
cuits for the actuators and the roll motor segments. The 
vernier pointing assembly is attached to the elevation 
gimbal and provides vernier attitude fine pointing and 
roll positioning of the instruments as well as six degree- 
of-freedom isolation from carrier motion disturbances. 
4 Claims, 4 Drawing Figures 
I _ -  
r 
d,, 
I 43 I 
I I 
AM PLI F E R  
DRIVER 4 
https://ntrs.nasa.gov/search.jsp?R=19790018201 2020-03-20T19:17:07+00:00Z
U.S. Patent May 29, 1979 4,156,548 
FIG. 3 
FIG. 2 
2 
4,156,548 
1 -
motor which produces forces tangential to the rim. Roll 
angle is determined from a linear sensor located along 
the periphery of the rim. Also, roll could be controlled, 
in a fine pointing mode, from signals generated by a roll 
5 sensor on board the experiment package. Thus, it is seen 
that the instrument mounting plate is completely iso- 
lated from the elevation gimbal (no interface connec- 
tion) and the only forces produced on it, as long as the 
electromagnet gaps are maintained, are those produced 
10 by the electromagnets themselves, in response to com- 
mand signals. 
MAGNETIC SUSPENSION AND POINTING 
SYSTEM 
ORIGIN OF THE INVENTION 
The invention described herein was made by employ- 
ees of the United States Government and may be manu- 
factured and used by or for the Government for govern- 
mental purposes without the payment of any royalties 
thereon or therefor. 
BACKGROUND OF THE INVENTION 
The invention relates generally to apparatus for BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a schematic diagram of the invention; 
FIG. 2 is a schematic diagram showing the invention 
mounting on a carrier vehicle; 
FIG. 3 is a schematic diagram of the annular rim 
upon which the instruments are mounted; and 
FIG. 4 is a sectional view 4-4 of FIG. 3 with a 
schematic drawing of the electrical connections made 
to the actuator. 
pointing the instruments on a carrier vehicle, such as a 
spacecraft, at a selected target and more specifically 15 
concerns apparatus for accurately pointing the instru- 
ments on a carrier vehicle at a selected target and for 
isolation of the instruments from carrier motion disturb- 
ances. 
Prior devices for pointing the instruments onboard a 20 
carrier vehicle includes mechanical isolation and torque 
motor pointing. Also, prior concepts have included 
magnetic isolation and pointing but have never used a DETAILED DESCRIPTION OF THE 
continuous annular rim providing roll control. The INVENTION 
disadvantages of these prior concepts are that they do 25 Turning now to the embodiment of the invention 
not provide complete six degree-of-freedom control selected for illustration in the drawings, the number 11 
and isolation simultaneously. in FIG. 1 indicates a carrier vehicle on which the inven- 
It is therefore the primary purpose of this invention to tion is mounted. An azimuth gimbal 12 is attached to the 
provide complete six degree-of-freedom fine pointing carrier vehicle and an elevation gimbal 13 is mounted 
and control for carrier vehicle instruments and to pro- 30 on gimbal 12. These two gimbals allow two rotations of 
vide complete six degree-of-freedom isolation of carrier an instrument package 14 relative to the vehicle and 
vehicle instruments from disturbances on the vehicle to thereby provide coarse pointing of the instruments. 
which the invention is attached. Instrument package 14 is mounted on a mounting plate 
15 which is magnetically suspended and fine controlled 
35 by means of a magnetic controller 16. A roll motor 17 is SUMMARY OF THE INVENTION 
This invention includes two assemblies with each mounted on gimbal 13 for the purpose of controlling or 
having a separate function. The first assembly is at- rotating instrument package 14 about the central axis 18 
tached to a carrier vehicle and consists of an azimuth of mounting plate 15. 
gimbal and an elevation gimbal which provide coarse The apparatus shown in FIG. 1 which is designated 
pointing of the instruments by allowing two rotations of 40 by the numeral 20 in FIG. 2 is mounted on a typical 
the instruments relative to the carrier vehicle. The sec- carrier vehicle 11 as shown in FIG. 2. 
ond, or vernier pointing assembly, is made up of mag- Mounting plate 15 and magnetic controller 16 shown 
netic suspension and fine pointing actuators, roll motor in FIG. 1 can best be understood by referring to FIG. 3. 
segments, and an instrument mounting plate around In FIG. 3 there is shown an annular rim 30 that sur- 
which a continuous annular rim is attached which pro- 45 rounds the mounting plate 15, not shown. Annular rim 
vide appropriate magnetic circuits for the actuators and 30 is made from a magnetic material such as iron or a 
the roll motor segments. The vernier pointing assembly composite material including ferrite pieces to provide 
is attached to the elevation gimbal and provides vernier magnetic circuits for the actuators. In this embodiment 
attitude fine pointing and roll positioning of the instru- of the invention the magnetic controller 16 includes 
ment as well as six degree-of-freedom isolation from 50 four magnetic actuators 31. However, it is to be under- 
carrier motion disturbances. In addition, the second stood that three or more of these actuators can be used 
assembly has a rim centering mode in which axial and without departing from the invention. To better de- 
radial rim p i t i o n  sensors located at each actuator scribe the actuators, a cross section 4-4 of FIG. 3 is 
station are used to center the rim axially and radially shown in FIG. 4 along with the electrical circuitry 
between actuator pole faces. This mode allows coarse 55 connected to the actuators. 
gimbal slewing for re-targeting, for earth pointing or for Each of the actuators 31 includes an electromagnet 
backup coarse gimbal pointing. 40, an electromagnet 41 and an electromagnet 42. For 
The vernier pointing system includes electromagnets the described embodiment of the invention the electro- 
working in opposed pairs axially and either singularly magnets do not use permanent magnets; however, they 
or in opposed pairs radially to provide fine pointing 60 could be used for flux biasing. Electromagnets 40 and 41 
forces on the rim of the instrument mounting plate. The which apply forces to opposite sides of rim 30 are con- 
command forces originate from rim position sensors nected to an amplifier driver 43 which applies a signal 
while in the rim centering mode or from instrument to each of the electromagnets. The signal is applied to 
pointing error sensors for the axial actuators while in electromagnet 40 if the rim is displaced in the direction 
the vernier pointing mode. The radial actuators can be 65 of electromagnet 41 and vice versa. A transducer 44 is 
controlled in a manner to reduce the effects of transla- included with each actuator 31 to produce a signal that 
tions ofthe carrier in the radial direction. Roll position- is proportional to the distance from transducer 44 to the 
ing is provided by a linear non-contracting roll torque annular rim 30. This signal is applied to the amplifier 
4,156,548 
3 
driver 43 which applies a signal to electromagnets 40 
and 41 to maintain annular rim 30 in a fixed neutral 
position. A signal can be applied to a terminal 45 which 
is added to the signal from transducer 44 by means of an 
adder 46 to control the position of annular rim 30 rela- 
tive to its neutral position. Hence, each actuator 31 
includes a magnetic means for magnetically suspending 
the rim in a direction parallel to axis 18 (axial direction) 
and for providing a fine control in that direction. 
A transducer 47 is located opposite the end of annular 
rim 30 that produces a signal proportional to the dis- 
tance from transducer 47 to annular rim 30. This signal 
is applied to an amplifier driver 48 which applies a 
signal to electromagnet 42 to maintain the annular rim 
in a neutral position. A signal can be applied to a termi- 
nal 49 which is added to the signal produced by trans- 
ducer 47 by means of an adder 50 to control the annular 
rim 30 relative to its neutral position. Hence, each actu- 
ator 31 includes a magnetic means for magnetically 
suspending the rim in a direction perpendicular to axis 
18 (radial direction) and for providing a fine control in 
that direction. It should be noted that if an even number 
of actuators 31 are used then opposing electromagnets 
42 can be connected together electrically. If two of the 
electromagnets 42 are connected together electrically, 
then one transducer 47 can be used to control both 
electromagnets or two can be used with the average 
output of the two used to control both electromagnets. 
In either case, a signal is applied to one electromagnet 
42 if the rim is displaced in the direction of the other and 
vice versa. 
Nominal operation of the invention for solar or stellar 
pointing first involves coarse gimbal pointing using 
coarse sensors on board the carrier vehicle and relative 
gimbal angle information. The rim centering is acti- 
vated during gimbal slewing. After coarse alinement, 
coarse roll positioning is accomplished using the rim 
roll motor and a relative roll sensor located on the rim 
5 
10 
15 
20 
25 
30 
35 
together with a carrier sensor. 40 
After coarse attitude alinement, vernier fine pointing 
is initiated. For this mode, errors from fine attitude 
sensors located on the vehicle are nulled by small mag- 
netic suspension and fine pointing actuator torques ap- 
plied to the annular rim. Also, translational rim control 45 
is accomplished for this mode. 
Nominal operation of this invention for earth point- 
ing initially involves establishing the correct azimuth, 
elevation, and roll attitude and attitude rates (slewing) 
using the rim centering mode. After appropriate smooth 50 
instrument slewing is established, vernier pointing, simi- 
lar to that described for solar and stellar pointing, is 
accomplished. 
Upon completion of a pointing task, the correction of 
appropriate interfaces between the payload mounting 55 
surface and the first assembly takes place. These inter- 
faces can be maintained during a pointing task if the 
pointing degradation caused by the interface connec- 
tion is tolerable. 
60 
4 
The advantages of this invention are that it provides 
complete six degree-of-freedom fine pointing and con- 
trol for carrier vehicle instruments and it provides com- 
plete six degree-of-freedom isolation of carrier vehicle 
instruments from disturbances on the vehicle to which 
the invention is attached. 
What is claimed is: 
1. Apparatus for providing accurate pointing for 
carrier vehicle instruments and for providing isolation 
from the vehicle comprising: 
a nonspinning annular rim made from a magnetic 
material for supporting said carrier vehicle instru- 
ments; 
several actuator stations located around the periph- 
ery of said rim; 
each of said actuator stations comprising: means for 
magnetically suspending said rim at the actuator 
station in the direction parallel to the central axis of 
said rim and for providing fine control in that di- 
rection; and 
means for magnetically suspending said rim at the 
actuator station in the direction perpendicular to 
the central axis of said rim and for providing a fine 
control in that direction whereby the combined 
actuator stations provided a fine control of said 
spacecraft instruments in five degrees-of-freedom. 
2. Apparatus according to claim 1 including means 
for turning said rim about said central axis to a selected 
position whereby fine control of said carrier vehicle 
instruments is provided in six degrees-of-freedom. 
3. Apparatus according to claim 1 wherein said means 
for magnetically suspending said rim in a direction par- 
allel to the central axis of said rim includes first and 
second electromagnets located opposite each other on 
two sides of said rim; a transducer on one side of said 
rim for producing an electrical signal proportional to its 
distance from said rim; amplifier means receiving said 
electrical signal for applying the amplified electrical 
signal to said first and second electromagnets to main- 
tain said rim in a neutral position in said direction paral- 
lel to the central axis of said rim; and means for adding 
a control signal to said electrical signal whereby a fine 
control can be maintained by said control signal in said 
direction parallel to the central axis of said rim. 
4. Apparatus according to claim 1 wherein said means 
for magnetically suspending said rim in a direction per- 
pendicular to the central axis of said rim includes an 
electromagnet located opposite the edge of said rim; a 
transducer located opposite the edge of the rim for 
producing an electrical signal proportional to the dis- 
tance of the transducer from the rim; amplifier means 
for amplifying said electrical signal and applying it to 
said electromagnet to maintain said rim in a neutral 
position in a direction perpendicular to said central axis 
of said rim; and means for adding a control signal to said 
electrical signal whereby a fine control can be main- 
tained by said control signal in said direction perpendic- 
ular to the central axis of said rim. * * * * *  
65 


Magnetic suspension and pointing system

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server

NASA Technical Reports Server