Apparatus for simulating varying levels of friction in the bearings of a free rolling tail afterbody on a canard-controlled missile to determine friction effects on aerodynamic control characteristics is described. A ring located between the missile body and the afterbody is utilized in a servo system to create varying levels of friction between the missile body and the afterbody to simulate bearing friction

Davis, W. T.

English

NASA Technical Reports Server

United States Patent 1191 11 11 4,425,785 
Davis [45] Jan. 17, 1984 
[54] MISSILE ROLLING TAIL BRAKE TORQUE 
SYSTEM 
[75] Inventor: William T. Davis, Yorktown, Va. 
[73] Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 338,386 
[22] Filed: Jan. 11,1982 
[51] 
[52] US. Cl. ........................................... 
Int. Cl.3 ..................... GOlN 19/02; GOlM 19/00 
73/9; 73/167; 
73/432 R 
[58] Field of Search .................... 73/9, 862.33, 862.34, 
73/862.08, 167, 432 J, 7; 308/10 
1561 References Cited 
U.S. PATENT DOCUMENTS 
4,154,489 VI979 Lyman .................................. 308/10 
4,169,367 10/1979 Wunder et al. ....................... 73/9 X 
4,235,092 11/1980 Spa11 .......................................... 73/9 
4,308,490 12/1981 Habermann et al. ............. 308/10 X 
Primary Examiner-Gerald Goldberg 
Assistant Examiner-E. Harding 
Attorney, Agent, or Firm-Howard J. Osborn; John R. 
Manning; William H. King 
1571 ABSTRACT 
Apparatus for simulating varying levels of friction in 
the bearings 13 of a free rolling tail afterbody 11 on a 
canard-controlled missile 12 to determine friction ef- 
fects on aerodynamic control characteristics. A ring 16 
located between the missile body and the afterbody is 
utilized in a servo system to create varying levels of 
friction between the missile body and the afterbody to 
simulate bearing friction. 
9 Claims, 6 Drawing Figures 
33 
12 24 
t L. I t- . 
i l -  
\ I  t \ I 
TORQUE 
BALANCE 
I I 
ELECTRO 
MAGNET 
LL 
https://ntrs.nasa.gov/search.jsp?R=19840008163 2020-03-22T08:12:35+00:00Z
U.S. Patent Jan. 17, 1984 Sheet 1 of 3 4,425,785 
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U.S. Patent Jan. 17, 1984 Sheet 2 of 3 4,425,785 
18 
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18 
40 
SPEED 
READOUT - 
CIRCUIT 
20 
I8 ' 
FIG. 3 
20 
FIG. 4 
19 
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21) 
- 42 
FIG. 6 
COUNTER 
TO COMPUTER 
U.S. Patent Jan. 17, 1984 Sheet 3 of 3 4,425,785 
4,425,785 
1 2 
produces an electrical signal proportional to the friction 
between the ring and the missile body. A servo system 
including the electromagnet and the torque balance is 
utilized to apply calibrated signals to the coil of the 
5 electromagnet to produce different levels of friction 
between the ring and afterbody which simulates the 
friction in the bearings- 
MISSILE ROLLING TAIL BRAKE TORQUE 
SYSTEM 
ORIGIN OF THE INVENTION 
ployee of the U.S. Government and mav be manufac- 
The invention described herein was made by an em- 
iurdd and used by or for the Government for govern- 
mental purposes without the payment of any royalties 
thereon or therefor. 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a schematic drawing of the embodiment of 10 
the invention selected for illust&tion in the drawings; 
components of the invention; 
FIG. 2 is a cross-sectional view of the mechanical 
FIG. 3 is an end view of the afterbody in FIG. 2; 
FIG. 4 is an end view of the ring in FIG. 2; 
FIG. 5 is a block diagram of the electrical compo- 
FIG. 6 is a block diagram of the electrical compo- 
nents of the invention; and 
nents for counting the revolutions of the afterbody. 
DETAILED DESCRIPTION OF THE 
INVENTION 
BACKGROUND OF THE INVENTION 
This invention relates generally to missiles and more 
particularly concerns the remote control of canard-con- 
trolled missiles. 15 
It is well known that missile configurations utilizing 
forward surfaces to provide control (canard-controlled) 
experience the problem of induced rolling moments at 
supersonic Mach numbers. For these forward con- 
trolled configurations the need is either that of reducing 20 
or eliminating the induced rolling moments or of pro- 
viding an efficient system for their control. 
One suggested approach is to use a free rolling tail Turning now to the embodiment of the invention 
concept to reduce the adverse moments On a selected for illustration (see FIG. 1) the numeral 11 
canard-controlled missile. A free rolling tail reduces the 25 designates a tail afterbody mounted for free rolling on a 
rolling moments by uncoupling the tail from the missile canard-controlled missile body 12 by of low 
airframe and also allows canard roll control at low fiction ball beadngs 13. A lock Screw 14 is provided to 
canard-controlled missiles more simplicity and modular rolling tail torque brake system 15 is provided for sirnu- flexibility by having a single cruciform canard-control 30 lating varying levels of friction in the bearings of the 
free rolling tail afterbody 11. The details of the brake system that provides pitch, yaw and roll control. 
system 15 are further illustrated in FIGS. 2, 3 and 4. A free rolling tail-fin afterbody on a canard-con- trolled missile has bearings which have varying levels 
of friction. These varying levels of friction produce Slideably attached to afterbody 11 is a metal ring 16 
Of attack. The free 'Once@ gives inhibit the free rolling of afterbody 11 when desired. A 
effects on the aerodynamic control characteristics, 35 (See 2)* An end view Of afterbody 11, as shown in 
the past the arerodynamic control characteristics FIG. 3, and an end view of ring 16, as shown in FIG. 4, 
of a canard-controlled missile could only be determined show how afterbody l1 and ring l6 are slideably at- 
figuration. The effects of varying levels of friction in the around its periphery which mesh with grooves 2o and 
namic control characteristics could not be determined. 19 extends to the ends of fingers 17. Consequently, ring 
Therefore, the primary object of this invention is to 16 is forced by the fingers and grooves to move rota- 
provide apparatus for determining friction effects On tionally with the afterbody 11, but can slideably move 
the aerodynamic control characteristics of a canard- 1ongitudinallY relative to afterbody 11. 
controlled missile by simulating varying levels of fric- 45 A reflecting ring 22 is fnounted on the inside surface 
tion in the bearings of a free rolling tail afterbody. of ring 16 closest to the missile body 12. The reflecting 
Other objects and advantages of this invention will ring 22 has alternate black and white segments to Pro- 
become apparent hereinafter in the specification and vide a Pulse output from a Photospeed t r a n x h ~ r  23 as 
drawings. ring 16 rotates with afterbody 11 relative to missile 
SUMMARY OF THE INVENTION A strain gage torque balance 24 is mounted on missile 
The above object is achieved by an apparatus for body 12 and Produces an output voltage which is a 
simulating varying levels of friction in the bearings measure of the torque on the missile body caused by the 
between a free rolling tail afterbody and a canard-con- rotation of afterbody 11 and the friction between ring 
trolled missile body. A ring is located between the mis- 55 16 and missile body 12. An electromagnet 25 which 
sile body and the tail afterbody. The ring is attached to includes a coil 26, is mounted on the torque balance 24. 
the afterbody by fingers and grooves on both such that When a Signal is applied to Coil 26, a magnetic force is 
the ring rotates with the afterbody and is slideable lon- applied to ring 16 which tends to slide ring 16 toward 
gitudinally in the direction of the missile body until the electromagnet 25, thereby closing the gap between 
contact is made with the missile body. An electromag- 60 the ring 16 and the electromagnet 25. The amplitude of 
net is mounted on the missile body such that the ring is the signal applied to coil 26 determines the rotational 
part of the magnetic circuit. Consequently, when a force applied from the rotating afterbody 11 through 
voltage is applied to the coil of the electromagnet, the ring 16 to missile body 12. This rotational force is pro- 
ring will slide against the body. A torque balance is portional to the signal produced by torque balance 24. 
attached to the missile body so that when the ring is in 65 The friction between ring 16 and electromagnet 25, 
frictional contact with the missile body, the torque when the two are forced together, produces the desired 
transmitted from the afterbody to the missile body is torque. A hard surface coating is flame sprayed onto the 
detected by the torque balance. The torque balance sliding surfaces to reduce wear. This coating is non- 
with a fixed tail configuration or a free rolling tail con- tached- Afterbody l1 includes fingers l 7  and grooves l8 
bearings of a free rolling tail afterbody on the aerody- 41) fingers 21 around the periphery of ring 16. A cylinder 
50 body 12. 
3 
4,425,78 5 
4 
magnetic and creates a magnetic gap which removes 
the problem of residual magnetism which would other- 
wise produce a large torque after a current is applied 
and removed. 
applied from a calibrated voltage source 30 to a sum- 
ming amplifier 31. The output of amplifier 31 is applied 
its closed position, to electromagnet coil 26. As a result, 
the magnetic force created by coil 26 slides ring 16 into 
contact with electromagnet 25. The friction between 
ring 16 and electromagnet 25 transmits a rotational 
force from afterbody 11 to torque balance 24. The out- 
34, a notch filter 35 and a full wave rectifier 36 to sum- 
ming amplifier 31 to subtract from the selected positive 
voltage from source 30. The friction between ring 16 
and electromagnet 25 is proportional to the voltage 3. Apparatus as in claim 1 wherein said means for 
selected at source 30 and is a simulation of friction in the 20 moving said ring in the direction of said nonrotating 
bearings 13 between afterbody 11 and missile body 12. body includes an electromagnet attached to said nonro- 
The purpose of notch filter 35 is to dampen vibrations in tating body such that the magnetic path of the magnet is 
the torque balance 24. Since afterbody 11 can rotate in completed through said ring. 
either direction, it will produce a feedback signal of 4. Amaratus as in claim 3 wherein said means for 
What is claimed as new and desired to be secured by 
Letters Patent of the United States is: 
1. Apparatus for simulating varying levels of friction 
between a rotating body and a nonrotating body com- 
a ring between said rotating body and said nonrotat- 
Referring to FIG. 5, a selected positive voltage is 5 Prising: 
ing body; 
such that said ring rotates with said rotating body 
and is movable relative to said rotating body in the 
direction of said nonrotating body; and 
for moving said ring in the direction of said 
nonrotating body to make frictional contact with 
said nonrotating body. 
though a power amplifier 32 and a switch 33, shown in for attaching said ring to said rotating body 
10 
put of torque balance 24 's applied through an amplifier 15 2. Apparatus as in claim 1 wherein said means for 
attaching said ring to said rotating body includes fingers 
and grooves on each of said ring and said rotating body 
that mesh. 
either plus (+) or minus (-) polarity. Full wave recti- 
fier 36 is used to ensure that the signal applied to sum- 
ming amplifier 31 will be of the correct polarity. A 
torque limit circuit 37, which has its two inputs con- 
nected to the output of rectifier 36 and to a negative 
limit voltage supplied from voltage source 38 and its 
output connected to summing amplifier 31, limits the 
torque to any preset value of source 38, and thereby 
prevents damage to torque balance 24 should the torque 
command (source 30) be set too high. The output torque 
can be read out by a voltmeter 39 or the voltage at the 
output of notch filter 35 can be connected to a computer 
for processing. 
A device for measuring the speed of rotation of after- 
body 11 is shown in FIG. 6. A speed readout circuit 40 
supplies voltage to a photo diode 41. The resulting light 
is focused onto reflecting ring 22. Each time a black 
segment passes, a pulse is produced at the output of 
circuit 40. These pulses are counted by a counter 43 and 
the count is connected to a computer for processing. 
The count on counter 43 is proportional to the speed of 
rotation of afterbody 11. 
The advantage of this invention is that it will allow 
in-depth studies of the effects of tail-fin spin rates on 
canard pitch, yaw and roll control characteristics. 
1 1  
25 moving said ring further includes a torque balance that 
produces an electrical signal proportional to the torque 
applied to it, attached to said nonrotating body such 
that when said electromagnet causes said ring to make 
contact with said nonrotating body the friction between 
30 said ring and said nonrotating body applies a torque to 
said torque balance. 
5. Apparatus as in claim 4 wherein said means for 
moving said ring comprises a servo system, including 
said electromagnet and said torque balance, in which a 
35 feedback signal is subtracted from a calibrated signal 
and the difference signal is applied to the coil of said 
electromagnet and the resulting signal produced by said 
torque balance is the feedback signal. 
6. Apparatus as in claim 5 wherein said feedback 
40 signal is passed through a notch filter to dampen vibra- 
tions in the torque balance. 
7. Apparatus as in claim 6 wherein said feedback 
signal is passed through a full wave rectifier to ensure 
that the feedback signal is the right polarity. 
8. Apparatus as in claim 7 including means for mea- 
suring said feedback signal to indicate the friction be- 
tween said nonrotating body and said ring. 
9. Apparatus as in claim 7 including means for mea- 
suring the speed of rotation of said rotating body. 
45 
* * * * *  50 
55 
60 
65 


Missile rolling tail brake torque system

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