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@ct 35, 11945“
G. 5. BROWN ET AL
2,409,1§0
REMOTE CONTROL SYSTEM
Filed Sept. 20, 1941
$95.2 é:
3 Sheets-Sheet 1
5
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INVENTORS
GORDON 8-. BROWN
JAY W. FORRESTER
Oct. 15, 1946.
I
I
G. 5. BROWN ETAL
REMOTE
CONTROL
' 2,409,190
SYSTEM
FilecI Sept. 20, 1941
3 Sheets-Sheet 2
VARIABLE
STROKE
i HYDRAULIC
VARIABLE
.
HYDRAULIC
STROKE
PUMP
86
INVENTORS
DON 5. BROWN
AY W.FORRESTER
70-’
'
la.
THEIR AT'TORNEY
- 6% 15, 1945-
- G. 5. BROWN- EI'AL
2,409,190
REMOTE CONTROL SYS TEM
Filed Sept- 20, 1941
v
3 Sheets-Sheet
VARIABLE.’
SPEED
_ so
DRIVE
5'
E?“ .
7o
'
I
96
5
98
7|
@I
(I1)
,
AMPLIFIER
RECTIFIER
l
INVENTORS
GORDON S. BROWN
JAY W._FORRESTER
7/ 70
I
_
THEIR
ATTORNE‘?
Patentecl Oct. 15, 1946
2,409,190
UNITED STATES ‘PATENT OFFICE
2,409,190
REMOTE CONTROL SYSTEM
Gordon S. Brown, Wellesley Hills, Mass, and Jay
W. Forrester, Anselmo, Nebr., assignors, by
mesne assignments, to Sperry Gyroscope Com
pany, Inc., North Hempstead, N. Y., a corpo
ration of New York
Application September 20, 1941, Serial No. 411,670
10 Claims. (Cl. 60—-53)
2
1
This invention relates to systems for remotely
controlling positionable objects, especially objects
having considerable inertia such as rotatably
mounted searchlights, guns and the like, to cause
the controlled object to move in correspondence
with a controlling object, and it refers, more
particularly, to systems of the above character
in which means are provided to compensate for
the normal tendency of the controlled object,
when following at the speed of the controlling 10
the present invention is principally concerned,
the speed of velocity of the driving means and
hence of the controlled object is primarily al
though not uniquely determined by the position
or setting of the motor controlling element. To
be able to use such a velocity signal or term to
object, to lag behind the position of the latter
eliminate lag we provide ?rst, as has been noted,
a system which is stable, that is, one without
hunting tendencies and second, means for pro
ducing a lag in the response of the controlled.
object to the velocity term as will be further
object.
pointed out.
Because of the means adopted, not only is it
One of the difficulties encountered in attempt
possible to control the amount of, or entirely
ing to provide a system, free from lag, for mov
eliminate, controlled object lag in our improved
ing a heavy object in correspondence with a
system, but it is further possible to cause the con
remote object is the tendency of such a system
trolled cbject to follow at a constant velocity in
to become unstable as the error in following is
a position in advance of the controlling object,
reduced, with resulting hunting or oscillation
that is, a lead of adjustable amount may be in
of the controlled object. Various types of anti
hunting control have been proposed but these ar 20 troduced. This is a feature particularly appli
cable to many types of gun positioning systems,
rangements have been for the most part, incon
for example, systems where the controlling object
sistent with the elimination of lag. The present
is a telescope or sight by means of which a moving
invention, on the other hand, provides an in
target is tracked and it is required that the gun
herently stable system to which complete error
compensation or controllable under or over com 25 be advanced ahead of the position of the sight to
compensate for target movement during the time
pensation may be applied without causing a tend
of flight of the projectile or to introduce other
ency to hunt.
corrections needed in such systems. ,
When the controlling and controlled objects
In addition to eliminating positional disagree
are moving at the same constant velocity, in a
system which employs a control term propor 30 ment or lag as a function of the velocity of the
tional only to positional disagreement as has
controlled object, it is possible by the control
means of the improved system to eliminate posi
heretofore been customary, the lag error may be
tional disagreement or lag due to variations in
taken to be proportional to this velocity if the
torque which the controlled object may impose
effect of the operating condition of the system is
disregarded. In this effect are included the re 35 on its driving means. That such a lag can exist
even under zero-velocity conditions is evident
sults of lost motion, leaks in hydraulic transmis
from the fact that the driving motor may re
sion systems and resistance to motion of the con
quired the maintenance of a certain rate of sup
trolled object. The effect of the operating con
ply of motivating medium merely to hold the con
dit-ion of the system, however, in practice is not
negligible and therefore to provide controllable
compensation for lag according to the present
trolled object in the desired position against a
counter torque or load. This torque~correction
invention, we make use of an auxiliary control
term or signal, in addition to and in combination
feature, like the elimination of velocity lag, is im
portant in gun positioning systems, where it is
necessary to hold the gun trained on the target
corresponds to a variable factor so proportioned 45 under varying conditions, such as where the gun
is exposed to a heavy cross wind, or where the
as to eliminate lag due to all of the above-men
gun base is not horizontal, so that a non-uniform
tioned causes. The value of this correction signal,
load may be imposed on the gun driving means.
according to the invention, is preferably deter
In the embodiments of the invention illustrated
mined by the position of a member which con
trols the output of the driving motor or other 50 in the drawings, certain elements are shown in
with the positional disagreement signal, which
means for moving the controlled object.
This
electrical, mechanical and hydraulic form and
are so described. It will be apparent to those
skilled in the art however,.that a wide choice is
presented as to the elements which can be used
vsince, ‘for-the type of drivingmeans with which 55 to perform the described functions and that sys
component of control, derived from the position
of the motor controlling element, is usually re,
ferred to hereinafter'as a velocity term or signal,
2,409, 1 9o
4
3
terns within the scope of the invention may uti
lize equivalents of widely diiTerent types.
One object of the invention is to provide'an
error-free remote control system for objects pos
sessing substantial inertia.
Another object is to provide an inherently
stable system for causing a controlled object to
follow the motion of a remote controlling object
and one which may be made error-free Without
thereby becoming subject to oscillation or hunt
ing.
Another object is to provide a system of the
above character in which the driving means for
the controlled object is actuated jointly in ac
cordance with the positional disagreement of the
controlling and controlled objects and in accord
ance with the position or setting of the speed
control for said means.
,
gun i8’. It will be obvious that any other heavy
object may be similarly arranged for controlled
movement.
“Selsyn” transmitter 4 and receiver H‘; are simi
lar to instruments commonly used in position
reproducing systems but are here used to generate
electrical signals proportional to the relative
position of their respective rotors. Electrical
differentials, such as differential 9, having a con
10 struction similar to “Selsyn” instruments are well
known in the art and need not be described here.
In'the operation of such devices the rotor tends to
align the magnetic axis of its ?eld with that of
the magnetic axis of the ?eld of the stator and in
consequence is adapted to exert a torque propor
tional to any misalignment of the directions of
the two ?elds, which in the present system repre
sent the positions of the controlling and con
trolled objects respectively, by virtue of the sig
A further object is to provide a system of the
above character in which the actuation of the 20 nals generated by “Selsyns” 13 and I4. Rotation
of rotor 3 is opposed by a counter torque applied
controlled object driving means in accordance
by springs II and H’ about pivot point 22 as
with said control setting is controllably delayed
to adjust the relative phase of the positional and
speed control terms.
will now be described.
small.
a housing 25 having a cylindrical bore in which
sleeve 25 is slidable, and within the sleeve a piston
Springs H and H’ resiliently connect levers I9
Another object is to provide a control system 25 and 223. Lever I9 is pivoted to datum at 2| while
lever 28 is connected to and rotates with diifer
which permits driving the controlled object se
ential rotor 8 about pivot point 22. Springs H
lectively in positional agreement with or lagging
or leading the controlling object by an adjustable
and l i’ being on opposite sides of the pivot point
are adapted to oppose rotation of lever 20 in
amount.
Another object is to provide a control system 30 either direction and thereby to supply a torque to
balance any torque developed magnetically be
in which the controlled object position is main—
tained in synchronism with or leading or lagging
tween rotor 8 and stator Iii. Lever 29 is pivotally
the controlling object position by an adjustable
connected at one end to piston rod 23 of pilot valve
Eli whose displacement furnishes the input to a
amount for any torque exerted upon the con~
trolled object, whether such torque be great or 35 hydraulic amplifying system. Valve 2s comprises
Still another object is to provide a system of
the above character in which a plurality of con
trolled objects may be positioned by a single
assembly, comprising pistons 21, 28, 25 and 3%]
formed on rod 23, is slidable.
Pistons 28 and
controlling object substantially without reaction 40 2e cooperate with and govern the effective open
one upon the other or upon the controlling
ings of ports 3! and 32, respectively, in sleeve
object.
Other objects and advantages of this invention
will become apparent as the description proceeds.
In the drawings:
Fig. l is a diagram of a control system in
accordance with our invention in which certain
26 while pistons 2'! and 39 close the bore of sleeve
28 to prevent loss of ?uid.
A motor 33 drives pressure pump 34 which sup
plies fluid, preferably oil, from sump 35 through
check valve 35 to valve 253 by way of intake pipe
38, the return ?uid flow from the valve to the
sump being by way of tail pipe 3?.
members are shown in section.
Figs. 2 and 3 are diagrams illustrating modifica-_
Pipe 38 communicates by way of port 39 in
sleeve 2%‘ with the bore of sleeve 28 to supply ?uid
tions of the system of Fig. 1.
Fig. 4 is a schematic diagram for purposes of
which normally exerts equal pressure in opposite
explanation.
directions on pistons 28 and 29.. In their equi
librium positions these pistons completely cover
Fig. 5 is an enlarged sectional view of a lag
controlling device.
and slightly overlap ports 3! and 32 in sleeve 26,
Fig. 6 is a schematic diagram showing a modi 55 respectively, which communicate with annular
?cation in the electrical positional control system.
grooves at and M on sleeve 26, respectively, which
In Fig. 1, reference numeral i is applied to a
in turn communicate with pressure pipes 42 and
[1.13, respectively, conecting with cylinder 44 on op
controlling object Whose motion is to be repro
posite sides of piston 155. The return ?uid from
duced at a remote point, which object is here
illustrated simply as a handwheel but may be a 60 the valve and cylinder ?nds its Way back to tail
tracking telescope or other movable member.
pipe 31 by way of ports 43 and 41, communicat
ing with annular passage-ways in housing 25 lead
Controllin?r object I rotates shaft 2 which mounts
the three-winding rotor 3 of “Selsyn” transmitter
ing to the tail pipe.
Piston £55 is mounted on piston rod 48 and the
it having a stator winding 5 excited from an alter
nating current source 6. The windings of rotor 65 motion of this piston, communicated by rod 48,
tilts cylinder block 49 of multi-cylinder, vari
3 are connected by three conductor transmission
able stroke pump 50 through yoke 49' which
line ‘I to similar windings of the movable or rotor
mounts the outer bearing in which the block
member 8 of electrical di?erential 9 also having
Pump 59) forms one unit of a variable
a similarly wound stator member iii. The wind
. turns.
ings of stator i9 are connected by three conductor 70 speed hydraulic drive in which the pump oper
ates hydraulic motor 5! at a speed dependent on
transmission line l2 to the windings of rotor E3
the stroke of its pistons which in turn is propor
of “Selsyn” receiver l4 having a stator l5 excited
tional to the angle of tilt of the cylinder block.
from source 6. Rotor I3 is mounted on shaft 16
This combination of pump and motor is well
connected by gearing ii to the controlled object,
here illustrated as rotatable platform I 8 mounting 75 known in the art under the name of the “Vickers”
2,409,190v
5
.
motion of the system ‘Ill, 12, 13 to a displace
variable speed drive and will not be described in
detail. Cylinder block 49 of the pump, constantly
driven by motor 55' and housing cylinders 52 in
which pistons 53 slide when the block is rotated
ment of bracket 69. A preferred construction of
said restriction is shownin Fig. 5 which illus
trates the use of a plurality of spaced thin discs
15 each closing conduit 14 except for a small ori
about an axis at an angle with the shaft of driv
ing motor 55’, is pivoted by yoke 49' about hol
low trunnions 54 and is angularly adjustable
about said trunnions in accordance with the posi
tion of piston rod 48. Fluid displaced by the
pump pistons is circulated to hydraulic motor 5| 10
?ce 15’. The several ori?ces 15' are in staggered
relation so that the damping fluid is forced by a
tortuous path through the conduit and passes
through a multiplicity of" ori?ces.
As an ex
by way of trunnions 54 throughlines 55 and 56
and motor 5| is connected to drive platform I8
by way of shaft 51 and shaft it connected to shaft
ample of the dimensions of a practical device,
%" diameter discs .002" thick have been used
having ori?ces .035" in diameter. Thin-edged
ori?ces of this type allow ori?ce ?ow which is
right end of the lever.
troducing a friction factor of predetermined mag
substantially independent of temperature. The
51 by gearing H’.
Piston rod 48 extends through cylinder 54 at 15 friction introduced by such an arrangement is
variable by varying the number of discs, the size
both ends and at the lower end is articulated
of the ori?ces and to some extent the staggering
through link 58 to rotate lever 59, pivoted at ‘65
and spacing. Means are thus provided for in
to arm 6|, through a pivot connection at the
At its left end lever 59
is pivotally connected to valve sleeve operating 20
rod 62 which axially displaces sleeve 26 within
nitude.
housing 25 to effect a change of registry between
ports 3| and 32 in said sleeve and pistons. 28
end of lever 16, rotatable about adjustable pivot
point 11, and the opposite end of lever 16 is piv
_
Piston rod 13' is pivotally connected to one
otally connected to one end of arm 18, which in
,
'
Arm Si is not ?xed to datum but is given a 25 turn is pivotally connected at its other end to
and 29 on rod 23.
lever ill at pivot point ‘I9.
In operation, angular displacement of hand
small longitudinal oscillation by "dither” motor
63 slidably mounted on base 64 and adjustable
along this base by means of adjustment screw 65.
wheel 1, by creating a disagreement between the
positions of “selsyn” rotors 3 and i3 at the two
which cooperates with slotted. link 61, pivoted to 30 ends of the system, relatively displaces the direc
tions of the resultant ?elds of rotor 8 and stator
datum at 68, to oscillate arm 51, the amplitude
it) of ‘fselsyn’P differential 9 and thereby causes
of this oscillation or dither being determined by
rotor 3 to exert a torque tending to tilt lever as‘
the position of eccentric 66 relative to pivot $8.
about pivot point 22. This torque is resisted by
The oscillation imparted to arm 5i is transmitted
the counter-torque exerted by springs H and I i’
to sleeve 26 through lever 59 and rod 52, piston as
about pivot point 22, the result being a limited
being substantially held against direct oscillation
rotation of lever 28, the magnitude of which is
by ?uid pressure.
determined by the ratio of the spring torque
The dither introduced by motor 63 preferably
(i. e., the strength of the springs times their lever
has a frequency in the neighborhood of about 30
to 60 cycles per second and an amplitude of a 40 arm) to the torque exerted by electrical differ
Motor 63 mounts on its shaft an eccentric 66
ential 9. Rotation of lever 2!] moves piston rod
23 and displaces pistons 2E and 29 to uncover ports
few thousandths of an, inch. With dither eccen
tric 66 stationary, pistons 28 and 29 normally
overlap ports 3! and 32, respectively, by a few,
3! and 32, respectively, and thereby differentially
change the fluid pressure on opposite sides of
thousandths of an inch. The actual magnitude of
the dither should be such that sleeve 26 oscillates 45 piston 45, causing said piston to move Within
cylinder 134 and, through piston rod 48, change
along its axis by an amount slightly greater
the angle of tilt of cylinder block 49. The result
than the port overlap so that ports 3! and 32 in
ing change in operating speed of hydraulic motor
sleeve 25 are opened at each extremity of the
5| is in aysense which tends to restore the posi
oscillation just sufficiently to admit ?uid cycli
cally to the piston 45 in quantities suitable to 50 tional agreement between the controlling and
controlled objects and hence to wipe out the sig
dither piston 45. The purpose of this dither
nal generated by the positional disagreement be
feature is to break seizures of relatively movable
tween rotors 3 and IS’.
contacting surfaces due to static friction and
to remove dead zones in the system from valve
piston rod 23 as far back as the output shaft H? 55
of the hydraulic transmission. In other words,
suf?cient tremor is imparted to piston 5.5 to im
part some (although a lesser) tremor to pump
and also to transmit su?cient tremor through
to motor 5i to take up any lost motion in gear
ing I‘! and H’, in addition to overcoming static
friction throughout the system. Therefore by
imparting the correct amount of tremor to the
system, we materially improve its response char
The motion of piston 45, transmitted by rod
link 58, lever 59 and rod 52 to sleeve 26, so
positions the sleeve that ports 3! and 32 are re
turned toitheir normal relationship with respect
to pistons 28 and 29. The connection between
piston 45 and sleeve 26 therefore constitutes the
60 repeat-back which wipes out the input to the
hydraulic amplifying system applied by way of
rod 23.
'At the same time that the motion of piston
45 is transmitted to sleeve 23 it changes the ex
acteristics, and eliminate errors due to lost mo 65 tension of spring 12 and thereby exerts a torque
on lever 18 about pivot point 1'! which, if unop
tion.
posed would cause link 18 to exert a correspond
Piston rod 48 at its lower end mounts a bracket
ing torque on lever l9 about pivot point 2|. How
69 connected by spring 12 and piston rod 13 to
ever, dash-pot ‘I! being ?lled with viscous ?uid
piston 70 moving in dash-pot 1!, spring 12 be
ing of a type adapted to sustain either tension or 70 which, to allow movement of piston 15, must be
pumped through ori?ces 15’ in conduit 14, move
compression. Dash-pot ‘H is ?lled with viscous
ment of piston 15 is initially retarded and is com
fluid which is pumped back and forth between
pleted only after a certain adjustable time inter
the opposite ends through a conduit 14 having a
val- Change of displacement of piston 45 is thus
restriction to introduce a friction factor and
thereby regulate the speed of response of the 75 transmitted after a delay to lever 19, where, by
2,409,190‘;
8
the coupling of springs H and H’, the resulting
torque is effectively combined with the torque
exerted by rotor 8 on lever 23. Since displacement of piston 45 is proportional to the angle of
tilt of cylinder block 49 and hence, for a given
operating condition, to the speed at which hy—
draulic motor 5! drives platform Hi, the system
springs I I" and 12' to pivot point 82 are 15 and la,
respectively. The damping‘ coe?icient of the re
sistance to motion of piston ‘H1 in dash-pot 1| is
f1. . schematically, motion of the piston 45 which‘
directly affects speed control rod 48 is shown as
being also transmitted to one end of lever 59’
(corresponding to lever 59) the other end of which
reciprocates sleeve 26, thus illustrating an ar
comprises means for combining with a signal pro
rangement adapted to provide a ratio between
portional to the positional disagreement of .a con
trolling and a controlled object a signal primarily 10 the movement of the piston and sleeve.
For purposes of analysis two ratios will now be
proportional to the velocity of the controlled ob
de?ned:
ject, the combination occurring in an adjustable
phase relationship. The sense in which the two
If 12 i]: assumed to have a length equal to unity, then
component signals are combined is signi?cant.
kg’: 3.
The so-called velocity term as de?ned herein is 15
here applied in a regenerative sense‘which causes
_displacement of piston rod 48
it to take over, Wholly or in part, the function of
the displacement or positional disagreement term
in supplying a control signal to keep the driving
means operating at constant velocity. Thus the
system may be caused to operate at constant
velocity with decreased lag or without any dis
agreement of the two objects, if so desired, or, by
increasing the magnitude of the velocity term, to
b_ displacement of valve rod 23
operate with the controlled object leading the 25
(assuming pivot point 8| to be at the center of
lever 20’), and
For zero error the relationship of the system
constants must be‘ such that
controlling object.
It should be noted that the extent to which the
displacement of piston 45 is not proportional to
the speed of the hydraulic motor (because of any
torque applied to and resisting motion of plat
form if; or because of oil leakage in the pump
and motor system of the Viclzers transmission) in.
no way prevents the controlled object from fol
lowing the controlling object in the manner de
sired. This is readily seen by noting that, should
a particular operating condition call for addi
The derivation of this expression is as follows:
If a: be a displacement of the pilot valve rod 23,
then be: is the corresponding displacement of
lever 76' at distance 15 from the pivot, and dy
will then represent the displacement of lever
'56’ at a distance Z3 from the pivot 82. The forces
acting on lever 16' may be equated as follows:
tional displacement of piston 45, the additional
displacement is supplied by an additional dis
placement of arm
initially by virtue of error
between selsyns 1% and ill, but eventually by dis
placement of arm l9 resulting from displacement
Since the derivation is concerned with equi
librium conditions under constant velocity op
eration, the effect of the dashpot may be disre~
garded.
Dividing (2) by 13 and separating terms in a:
of piston 125. Thus again, a displacement of lever
and y
l9 resulting from displacement of piston 45 has
taken over, wholly or inpar‘w-whichever is de
sired-the function of the displacement or posi- .1
tional disagreement term in systems of the usual
type so that the system of the present invention
operates at constant velocity or at rest in the
presence of different load torques without dis
k
and
(3)
k5b+ 7%
11:1 —d+
k2 lad
agreement of the two objects, or with the con- ,
trolled object leading or lagging the controlling
object by a predetermined amount, as desired.
Fig. 4 is a purely schematic simpli?ed diagram
I
:c(k5b+ {1) =3; {3+ lad)
The forces which act on lever 20' may be ex
pressed as
of the system of Fig. 1 on which are designated
(5)
the constants whose relationships determine the
Where
e=angle
of
misalignment
of
magnetic
stability of the system and the error or absence
axes of synchro differential due to an error be
of error in the following of the controlled object.
tween controlled and controlling object.
Rotor 8 and stator ll} of di?erential 9 are shown
Substituting (4) in (5),
connected by a virtual spring 9', having a stiffness
k3 representing the torque exerted per degree of
misalignment of the stator and rotor ?elds.
(6)
Lever 28' corresponding to lever 26 of Fig. 1 is
rotated about pivot point 8! by rotation of rotor
If e is to equal zero for all cases of constant ve
S. The equivalent stiffness of the virtual spring
9’,
manifested at the end of lever 28’, may be 65 locity operation, then
taken as ks’ where
tamefrewso
is
If 12 is assumed to have a length equal to unity, 70
then ks'zks. Spring H", having a stiffness R2,
represents a combination of springs H and Ill’
while 705 is the sti?ness of spring "l2. Lever l6"
pivoted to datum at 82 replaces levers ‘wand £9.
The distances from the connection points of 75
(7)
which may be solved explicity for b, as in (1)
above.
,
v
In order that the controlled object may follow
the controlling object at a constant velocity but
at an angle of lead: the value of b should be
greater than that for zero error as de?ned above
2,409,190;
9 .
10
less.
Stability in our improved system is best
the variation thus introduced causing a misalign
ment of the ?eldsof “selsyn's” 4 and M at the
sending and receiving ends, respectively, and
achieved by ?rst making the response of that part
of the system which comprises valve 24 and piston
of differential 9. An additional torque
and conversely for an angle of lag it should be
65 so rapid that it can faithfully follow incipient
oscillations in that part of the system which com
prises the selsyn instruments and the connected
load, second by choosing spring constant k2 so
thereby a misalignment of rotor and stator ?elds
thus
exerted on levers l9 nd 29 in a manner generally
similar to the additional torque ‘exerted upon
these levers by arm ‘E8 of Fig. 1.
While the velocity'term is shown as being in
troduced
through the rotation of one of the mem
10
that its relation to the spring constant 103, the
bers of selsyn 14, it will be apparent that the
characteristics of the hydraulic transmission,
same effect may be produced by the rotation of
and other constants of the system, provides a
one of the pair of relatively movable members
stable system having rapid response and third
of
either “selsyn” 1?. or differential 9, the result
by applying the so-called velocity signal in
proper phase by adjustment of the dapming in 15 in any case being the misalignment of two mag
netic ?elds of a' device which directly or in
troduced by motion of piston 10. When the con
directly causes an input signal to be supplied to
stants of the system ful?ll the above conditions
valve 25 with a resultant change in the output
no oscillation can build up and we are free to
of the hydraulic motor.
make the system errorless for constant velocity
Fig. 6 illustrates in the schematic form of Fig.
following. Previously proposed systems have not
provided this rapid response in combination with
the proper phasing of a velocity control and
hence could not effectively neutralize incipient
oscillations and prevent their building up.
4 a modi?cation of the invention in which. the
input to the hydraulic drive proportional to the
positional disagreement of thev controlling and
controlled objects is supplied by a special torque
motor actuated by a signal‘generated by the re
The modi?cation of Fig. 2 illustrates a system 25 ceiving end “selsyn,” the signal being preferably
generally similar to that shown in Fig. 1 except ' ampli?ed and recti?ed, for example, in an elec
that dash-pot ‘H is connected directly to lever
19 instead of through the spring '62 and the link
age shown in Fig. 1. This is a simpli?cation
which permits the construction of a stable sys
tem in which, while all error cannot be elim
tron tube ampli?er. “Selsyn” A is excited from
source 6 as in the previously described arrange
ments but the windings of its rotor 3 are directly
connected by three conductor transmission line
IE’ to the rotor windings of the remote “selsyn”
inated, the controlled object is capable of oper
it instead of to an intermediate electrical differ
ating at a very small angle of lag which may be
ential. _The rotor l3 of “selsyn” it; being driven
satisfactory for many purposes. Speci?cally this
in positional agreement with the controlled ob
modi?cation of the invention provides a system 35 ject, the stator l5 receives a reversible phase
in which the lag, or error in following, which ex
E. M. F. proportional in magnitude to the posi
ists when arm I9 is stationary in its central po
tional disagreement of the two objects, as is well
sition, is reduced by an amount given by the
known in the art of positional control systems,
ratio
'
40 vwhich signal is applied to the input of a balanced
ampli?er-recti?er 90 whose D. C. output excites
103+ k2
torque motor 9|. Ampli?er ?ll is preferably of a
known type‘having a split vor push-pull output
since 762 may readily be made at least four times
circuit, such as is shown, for example, in the
as great as 703 it follows that the lag, or error in
pending application of C. Frische et al., for Elec
following (at constant velocity) may be reduced 45 tro-hydraulic control system, Ser. No. 284,642,
by the arrangement of Fig. 2 by at least 80 per
?led'July 15, 1939., ‘
.
cent. As a further simpli?cation conduit 1!! may
Motor 9| comprises pole pieces 92 of a magnet
be eliminated and piston 10' corresponding to
assembly supplying flux toa gap in which arma
piston 10 Fig. 1, provided with a plurality of pas
93 is located. Armature 93 carries split coil
sageways at through which ?uid is pumped from 50 ture
96 (or its equivalent, two connected coils) having
one end of the cylinder to the other. These pas
sageways may be of desired area to give a pre
two'extern'al‘ terminals and a center tap all con
determined value to the frictional constant ii.
In the operation of the modi?cation of Fig. 2,
the two halves of the coil being respectively con
nected to the split output circuit of ampli?er 94,
nected to the two halves of the output circuit.
when rotor 8 exerts a torque on lever 26 due to . ‘
Armature 93 is mounted on shaft 85 by means of
misalignment of its ?eld‘ with the ?eld of stator
which it is capable of exerting a torque on lever
l0, piston 84 initially resists tilting of lever l9
20' in. the manner of rotor 8 of differential 9.
and so causes springs I I and II’ to exert a strong
counter torque which is eased as piston 84 moves
against friction to permit further tilting at lever
20.
No velocity signal is used in this modi?
cation.
7
»
. In the modi?cation of Fig. 3, a control signal
proportional primary to the velocity of the con
trolled object is introduced into the system elec- .
tro-mechanically instead of my mechanical
means only as in the arrangement of Fig. 1. In
Fig. 3 piston 10’ is driven from piston rod 48
through adjustable ratio lever 69 and spring 12
and its displacement is communicated to rotat
able member l5’ of selsyn l4 (which takes the '
place of previously described stator l5) by way
of rack and pinion 85 and gearing 86 and 81.
In this arrangement member I5’, is rotated to
vary the angular position of its magnetic ?eld,
In operation, potential disagreement of the
two objects creates an A. C‘. signal voltage in
stator winding [5 proportional to the disagree
merit and phased according to its ‘sign, i. e., ac
cording to whether a lag or lead in following
exists. When’ no signal is applied to‘ the input
of ampli?er 90 substantially equal recti?ed cur
rents ?ow in the two halves of winding 94, the
effects of which, due to the coil connections,
neutralize one another (or the ampli?er may be
operated so that normally no current flows in
either half of the coil). Upon the application
of an input voltage to ampli?er 98 a differential
change of current occurs in the two halves of
coil 95 and a torque is created by the interaction
of the permanent ?eld due to the pole pieces and
the unbalanced armature ?eld thus created
5,405, 1 9o
.
12
ii
The sense 'of the differential change of output and
hence of the torque exerted by the rotor is de
termined by the phase of the ampli?er input,
which in turn depends on whether a lag or lead
exists, and thus the torque exerted on lever 2'5’
by rotor Q3 can be made to apply an input to
Having described our invention, what we claim
and desire to secure by Letters Patent is: I
1. A positional control system comprising a
controlling object, a controlled object, a variable
speed drive for actuating the controlled object,
error-measuring means responsive to differences
in position between controlled and controlling ob
the hydraulic transmission of the proper sign to
restore positional agreement between the two
jects for generating an error signal as a function
objects. By proper design, also, the torque ex
of said disagreement, an ampli?er having its out
erted by motor 91 can be made closely propor
put in control of the variable speed drive and
tional to the di?erence of the currents in the
having its input connected to the error-measur
two halves of its armature winding, which in turn
ing means, and a regenerative feedback connec
is readily made proportional to the signal input to
tion from the ampli?er output to the ampli?er
ampli?er $33. Other means including A. C. ex
input, said feedback connection including means
cited torque exerting devices may be employed 15 for delaying transmission to the input of the ef
to supply a torque proportional to error in fol
fect of changes in the output.
lowing.
2. A positional control system comprising a
' One of the important advantages of the ar
controlling object, a controlled object, a variable
rangement of Fig. 6 over the arrangements pre
speed drive for actuating the controlled object,
viously described is that very little power is re
a speed control for said drive, error-measuring
quired as an input to ampli?er 9B in comparison
means responsive to differences in position be
with the power which must be delivered to differ
tween controlled and controlling objects for gen
ential Q, for example, to cause it to exert the re
erating an error signal as a function of said dis
quired torque on lever 26. This considerablyim
agreement, an ampli?er having its output con
proves the operation of the system and permits
25 nected to the speed control of the variable speed
the control of a number of separate objects from
drive and having its input connected to the error
a single controlling object without the behavior
measuring means, and a regenerative feedback
or position of one controlled object seriously af
connection from the speed control to the ampli
fecting the behavior or position of any of the
fier input, said feedback connection including
other objects or causing substantial reaction on
means for delaying the effect at the ampli?er in
the controlling object. An important applica
put of changes in the speed control.
tion of our invention resulting from this feature
3. A positional control system comprising a
is the control of a battery of guns, or other mov
controlling object, a controlled object, a variable
able objects of substantial inertia, by -a single
speed drive for actuating the controlled object,
controlling element, such as a sighting telescope. 35 error-measuring means responsive to differences
In Fig. 6 there is shown a three-conductor
in position between controlled and controlling ob
transmission line $6 branching off from line [2’.
jects for generating an error signal as a func
This-branch line is adapted to be connected to
tion of said disagreement, an ampli?er having
the rotor winding of a second “Selsyn” signal
its output in control of the variable speed drive,
generator similar to “selsyn” l4 and if the rotor
a regenerative feedback connection from the am
of this second “selsyn” be rotated in correspond- .
pli?er output for supplying a signal related to
ence with a second controlled object. a system
the speed of the controlled object, means for
similar in all respects to the one shown and
combining the error and the regenerative feed
described in detail, including the driving and
other associated means, may be added, the con
trolling object and transmitter being common to
the two systems. To simplify'the ?gure only the
transmission line to the receiving “selsyn” of the
second system is indicated.
.
back_ signals and for supplying the combined sig
nal to the amplifier input, and means associated
with the feedback connection for delaying the ef
fect at the ampli?er input of changes in ampli?er
output.
‘4. A positional control system comprising a
Since the signal taken from this receiving or 50 controlling object, ‘a controlled object, a variable
controlled object “selsyn” oi‘ the second system
speed drive for actuating the controlled object, a
will preferably be applied through an ampli?er
movable control element in control of said drive
similar to ampli?er 9D and since only a very small
to vary the speed thereof, error-measuring means
amount of power is transmitted over the common
responsive to differences in position between con
line to supply the inputs to the ampli?ers there 55 trolled and controlling objects for ‘generating an
will be relatively little coupling between the sepa
error signal as a function of said positional dif
rate systems. To further reduce interaction be
ferences, an amplifier having its input responsive
tween the receiver “selsyn,” resistances 9‘! and 98
to the error signal and its output connected to the
may be inserted in the lines respectively feeding
movable control element of the variable speed
these “selsyns” after the point at which the lines 60 drive, and a regenerative ‘feedback connection
branch from the common circuit. A considerable
between the movable speed control element and
number of receiving “selsyns” may be intercon
the ampli?er input for supplying to said input a
signal based on the position of the speed control
nected in the described manner without reaction
and employed as signal generators in a corre
element, said feedback connection including
sponding number of systems according to our 65 means for delaying transmission to the ampli?er
input of changes in position of the speed control.
invention.
5. A positional control system comprising a con
As many vchanges could be made in the above
trolled
object, a controlling object, a variable
constructionand many apparently widely di?er
speed drive for actuating the controlled object, a
ent embodiments of this invention could be made
speed control for said drive, error-measuring
without departing from the scope thereof, it is 70 means
responsive to differences in position be
intended that all matter contained'in the above
tween confrolled and controlling objects for gen
description or shown in the accompanying draw
erating an error signal as a function of said dis
ings shall be interpreted as illustrative and not in
agreement. an ampli?er having a power output
a limiting sense.
75 member connected to the speed control for the
2,409,190
I
13
variable speed drive and an input member con
nected to the error-measuring means, and a re
silient regeneratively-connected feedback con
nection between the power output member of the
ampli?er and the input member, said feedback
connection including means for delaying the re
sponse of the input member to changes in posi
tion of the speed control.
6. A positional control system comprising a
controlled object, a controlling object, a variable
speed drive for actuating the controlled object,
a speed control for said drive, error-measuring
means responsive to differences in position be
tween controlled and controlling objects for gen
14
trol, resilient centralizing means connected to the
ampli?er input device, said centralizing means
being adjustable, and a regenerative feedback
connection from the ampli?er output for adjust
ing the centralizing means in accordance with the
position of the speed control, said connection in
cluding a damped resilient connection between the
centralizing means and the ampli?er output for
delaying the response of the centralizing means to
changes in the setting of the speed control.
9. A positional control system comprising a
controlled object, a variable speed drive for actu
ating the controlled object, a movable speed con
trol element in control of said drive, error
erating an error signal as a function of said dis lo measuring means responsive to differences in po
sition between controlled and controlling objects
agreement, an ampli?er having a power output
for generating an error signal as a function of
member connected to the speed control for the
said positional disagreement, means including a
variable speed drive and an input member con
hydraulic ampli?er for actuating the movable
nected to the error-measuring means, and a re
generatively-connected feedback connection be 20 control element of the variable speed drive, said
ampli?er comprising a pilot piston connected to
tween the speed control member and the ampli
the error-measuring means, a power piston con
?er input, said connection including a movable
nected to the movable element in control of the
member, damping means therefor, and resilient
variable speed drive, a pilot piston sleeve, a re
connections between the movable member and the
speed control and between the movable member 25 peat-back connection from the power piston to
the pilot piston sleeve, and a regenerative feed
and the ampli?er input.
back connection from the power piston for sup
7. A positional control system comprising a
plying a. signal based on displacement of the speed
controlled object, a controlling object, a variable
control element, said feedback connection includ
speed drive, for actuating the controlled object,
a speed control for said drive, error-measuring 30 ing spring and dashpot means for delaying trans
mission of said displacement signal, and means
means responsive to differences in position be
for combining said error and displacement signals
tween controlled and controlling objects for gen
and for actuating the pilot piston in accordance
erating an error signal as a function of said dis
with the combined signals.
agreement, an ampli?er having displaceable input
10. A positional control system comprising a
and power output devices connected respectively 35
controlled object, a controlling object, a variable
to the error-measuring means and to the speed
speed drive for actuating the controlled object,
control, resilient means cooperating with the
a movable speed control element in control of
error-measuring means and the ampli?er input
said drive, error-measuring means responsive to
device for controlling the response of the latter
to an error signal, and a regenerative feedback 40 differences in position between controlled and
connection from the ampli?er output to the re
silient means for modifying the control action
thereof on the ampli?er input device in accord
ance with the setting of the speed control of the
controlling objects for generating an error signal
as a function of said positional disagreement,
means including a hydraulic ampli?er for actuat
ing the movable control element of the variable
variable speed drive, said feedback connection 45 speed drive, said amplifier comprising a pilot
piston connected to the error-measuring means,
including means for delaying the effect at the >
a power piston connected to the movable element
in control of the variable speed drive, a pilot
control.
'
piston sleeve, a repeat-back connection from the
8. A positional control system comprising a
controlled object, a controlling object, a variable 50 power piston to the pilot piston sleeve, and a re
generative feed-back connection from the power
speed drive for actuating the controlled object, a
piston to the pilot piston, said feedback connec
speed control for said drive, error-measuring
tion
including a movable member, damping means
means responsive to differences in position be
therefor, and resilient connections between the
tween controlled and controlling objects for de
veloping a force as a function of said disagree 55 member and the power piston and between the
member and the pilot piston.
ment, an ampli?er having displaceable input and
GORDON S. BROWN.
power output devices connected respectively to
JAY W. FORRESTER.
the error-measuring means and to the speed con
resilient means of changes in setting of the speed
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