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Патент USA US2411750

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NOV. 26, 1946.
H_ OLKEN
FOLLOW-UP CONTROL SYSTEM
- Filed Sept. 12, 1941
311,75
‘
2 Sheets-Sheet 1
'(ROpTAag-IONn-Q)
Hyman O/ken
Nov. 26, 1946.
H, OLKEN
2,411.759
FOLLOW-UP CONTROL SYSTEM
Filed Sept. 12, 1941
2 Sheets-Sheet 2
36
2
23
24/
W
2e 62
mm
70/
756
73p,
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.32
Fo/lowing f/emem‘.
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Hyman Ol/(en
w, ju‘
Patented as. 26, rate
- 2,4113%
2,411,750
FOLLOW-UP- CONTROL SYSTEM
Hyman 0lken,.Washington, D. C.
,
Application September 12, 1941, Serial No. 410,534
12 Claims.
(Cl. 172-239)
1
2
.
This invention relates to control systems and
cator. The following unit comprises, for exam-v
more especially to regulating devices for control
ple, a mount, a turret, a director or a recorder.
The servo arrangement usually comprises a pow
systems, wherein an indicator or sending instru
ment controls the position of a following unit or
other receiving device.
erful motor, for driving the following unit, and
,
Among the objects of my invention is the pro
vision of an accurate and reliable following unit
control system which enables the maintenance
of close synchronization of movement of indi
cating and following units, which possesses 10
greater mechanical simplicity, together with
greater efllciency, than heretofore known control
a control, usually an ampli?er, to run the motor
a proper amount and in a proper direction to.
reduce to zero any deviation of the following unit
from the indicating element.
A control system of the type described, when
employed for controlling a, gun mount, enables
the automatic pointing of a gun in correspond
ence with the direction of a target, as indicated.
by a‘ dial setting of a range ?nder or by a position
systems, which is economical to construct, re
of a gun sight. Other positioning type regulators
quiring a minimum of expensive parts in its pro
duction, which is serviced readily without ‘the 15 are in use, such as those for positioning a cutting
tool of a lathe in accordance with the position
assistance of a, specially trained expert, and
of a stylus following a templet; or for position
which accordingly is adapted for a wider range
ing a recorder pen in accordance with a galva
of application in the art of following unit control.
Other objects in part will be obvious and in
part pointed out hereinafter.
nometer pointer indication. It will be understood
20 that my invention applies to all applications of
v
this'type, but for purposes of illustration, the
theory of gun mount control is stressed to some
degree.
Naturally, a heavy following unit being driven
more of the others as described herein and shown ~25 under high power has high inertia and this inertia
causes the following unit to overshoot a position
in the accompanying drawings, the scope of the
signalled by the indicating element. Upon the
application of which is indicated in the following
following unit overshooting signalled position, a
In the accompanying drawings illustrating cer
corrective action occurs wherein the following
30 unit reverses to reduce its deviation from the
tain features of my invention,
indicating element. This process of overshooting,
Figure l diagrammatically illustrates a pre
then reversing, commonly is termed “hunting.”
ferred basiccontrol circuit for the following unit
'The invention ‘accordingly consists in the com
bination of elements, features of construction and
arrangement of parts and in the severalsteps
and the relation of each of the same to one or
claims.
‘
'
Often more than one overshoot and correction
‘
‘
Figure 2 illustrates a motor-driven centralizing
take place before the following unit comes to rest
35 at proper position.
device for the control mechanism of Figure 1.
.
‘
For most all applications of control systems
Figure 3 illustrates ?rst time derivative of de
of the type defined, particularly for gun pointing, viation following unit damping mechanism in
of my invention.
it is desirable to eliminate overshooting and hunt
circuit with the apparatus of Figure 2.
Figure 4 gives a graphic comparison of the
ing .of the following unit, or at least to reduce
operation of certain control devices described 40 these factors to a tolerable minimum. It is known
hereinafter.
‘
in the art that making the following unit motor
Figure 5 illustrates velocity squared damping
speed decrease in direct proportion to deviation
mechanism applied to the apparatus of Figure 2.
greatly reduces overshooting and hunting of the
Figure 6 illustrates selector mechanism applied _
following unit. Also, it is known in the art that
to the combined damping mechanisms of Figs. 3
applying an "anticipating correction" to the fol
and 5.
As conducive to a clearer understanding of my
lowing unit motor control system proportional
invention, it should be noted .at this point that
control systems of the type described broadly
cating element and following unit, thatis, further
slowing down the driving motor in proportion
to the ?rst time derivative of the deviation, will
further reduce hunting and overshooting 0f the
following unit. Still further,- it is known that
upon the application of an additional "anticipat
55 ing correction," a second time derivative of de
comprise an indicator, as for example, a gal
vanometer, a compass. a gun sight or a range
finder, which is moved under very little power:
and a servo arrangement to effect the high power
driving of a following unit in response to dis
placement of the indicating element of the indi
to the rate of change of deviation between indi
{ii
viation reduces, even more, overshooting and
hunting of the following unit.
_
Where most re?ned control is desired, that is,
where only negligible hunting of the following
unit is permissible, it is conventional practice for
reasons noted hereinbefore, to provide av control
system wherein following unit motor speed is
decreased in direct proportion to deviation, and
wherein ?rst and second time derivatives of devi
is the provision of following unit control appa
ratus which ensures well damped asymptotic ap
proach of the following unit to indicated posi
tion, which is adapted to apply one of two follow
ing unit speed corrections to the following unit
motor depending on the degree of deviation be
tween the following unit and indicating element,
which for large deviations damps the following
unit motor by the imposition of a velocity squared
ation are applied further to damp the motor 10 speed correction and which applies a time deriva
tive of deviation correction to the motor for small
speed. To make such regulators effective, there
deviations giving re?ned control to the motor and
must be very sensitive indication of the deviation.
thus to the following unit as the following unit
Anampli?er is used in order to achieve such
sensitive indication. Ampli?cation frequently is
' approaches indicated position.
Referring now more particularly to the prac
accomplished by electrical means such as by the 15
tice of my invention, I provide a control system
use of radio tubes, or by hydraulic means, or
wherein movement of an indicator and a follow
mechanically by step-up gearing as by using a
ing unit'are so synchronized that displacement
36-speed synchro. By amplifying the deviation
of the indicator from a neutral position brings
by making speed of the following 'unit ’propor—
tional to deviation, and applying ?rst and second 20 about proportional displacement of the following
unit. In my control system, I provide means for
starting the restoring motor in proper direction
so as to reduce deviation to zero, when there is
deviation; and means for shutting off the restor
following unit. Ampli?cation, however, spreads
a small deviation into a wide operating range of 25 ing motor when deviation is reduced to zero. I
also employ the conventional practice of making
the following unit motor controlling mechanism.
the motor speed decrease proportionally as the
Therefore, ampli?cation restricts following unit
time derivative corrections to the motor control
system, reduction of deviation to zero is permit
ted with negligible hunting or overshoot of the
control to a small range of deviation, hence to
a small interval in the total operating range of
the following unit.
-
deviation decreases, and of putting in, in addi
tion, a ?rst derivative correction for motor
velocity.
I apply the ?rst derivative correction over only
a very small portion of the total operating range
of my control system. A superimposed second
may be up to 360°, and possible deviation in train
derivative correction also may be present within
may vary through as 'much as 180°, it has become
the practice to maintain sensitive precise control 35 this range, even though I attain good results
In machines having extensive range of opera
tion, such as a gun mount where range of train
over the following unit or mount only for a small
without any such correction.
This range is so
small that with ?rst derivative'correction only,
range of deviation of about 21/2". Very accurate
'hu'nting, overshootingand residual deviation of
?rst and second time derivative of deviation con
the following unit are negligible.
trol, accordingly, is maintained over the follow
Beyond that range, I apply no derivative cor
ing unit when the indicator and following unit 40
rection of any kind, but a correction proportional
are close together. When deviation extends be
to the square of the velocity of the following unit.
yond this range, a relay, for example, switches
This prevents storage of energy in the following
off the sensitive control mechanism and the motor
unit on big swings in a manner linear with devia
of the following unit merely is turned full on,
tion. Consequently,‘ as the deviation becomes
in proper direction, until deviation again de
small, the following unit has very little stored
creases to 21/2", at which time the relay termi
energy and can be stopped substantially at proper
nates full-on operation'of the motor and brings
position by the ?rst derivative correction control
into play the sensitive control mechanism.
alone.
Such an over-all method of control has the
For switching over automatically from the
serious objection that the mechanism for deriv 50
?rst derivative control to velocity squared cor
ing a second time derivative of deviation and
rection, or vice versa, ‘when the deviation becomes
superimposing it properly upon the ?rst deriva
large or small as the case may be, I use a pre
tive correction, whether by electrical, mechanical
determined ratio of unbalance of restoring motor
or hydraulic means. makes for an intricate appa
control elements. These restoring motor con
ratus which is costly to manufacture, which gets
trol elements are, for example, opposed motor
out of order readily, and which requires special
?elds. or opposed hydraulic means. This meth
ized experts to understand and service it. Even
od of automatic switching makes for a positive,
more important is the fact that in machines
snap-like switch-over as distinguished from a
where swings of the indicating element, hence
deviations, are large, as in positioning an anti 60 chatter, trembling, slow transition.
My entire system of control eliminates the in
aircraft gun, there is but hit-.or-miss control of
tricacy of second derivative elements, and par
the gun over the greatest partof the range of
ticularly as applied in my preferred embodiment,
movement. When gun and indicator or sight
makes a rugged, reliable unit sufficiently com
come very close together, that is, when deviation
becomes small, there is a sudden switching and
jumping over to precise ?rst and second deriva
tive control. If the overshoot extends beyond
the ?ne control range, there is again a sudden
pact and simple to construct, install and main
tain without great expense and without requiring
the aid of high-skilled technicians.
As illustrative of the practice of my invention,
attention is directed to Fig. 1 'ofrthe drawings,
switch-over back to full-on operation of the
motor. This results not only in poor aiming of 70 wherein an embodiment of the basic, directioning
unit of my invention is illustrated diagrammati
the gun, but the sudden transitions from full-on
cally. A cathode-ray tube T is energized from
operation to sensitive control make it addition
a battery B, and the tube, in turn, energizes ?eld
ally di?'icult to provide smooth control over the
windings FI and F2 of following unit motor 21.
movement of the gun.
One object of the present. invention, therefore, 75 An instrument pointer or indicating element l2
an 1,750
5
operated in any desired-manner, is mounted piv- ’
otally at point It. Electrode l3, formed at the
lower end of indicating element I2, is adjacent
to the mid-exterior surface of cathode ray tube
T and is free to rotate about point Ill in a clock
wise or counterclockwise direction. The elec
trode I3 is connected by lead 24 ‘to negative ter
minal125 of battery B. A ?xed electrode Hi is
positioned within tube T substantially at the ion
B, is. greater than the current ?owing through .
winding F2 in circuit with plate P2. A current
differential therefore exists between the two
opposed windings Fl and F2 and motor 21 is
energized by this differential. It should be noted
at. this point that when indicating element l2
moves ‘on the right side of central position, the
distance of electrode I?! from center and the
downward deflection of beam B2 from anode plate
gitudinal midpoint of the tube and is connected 10 P2 by electrode l3, increase in direct proportion.
It is to be noted further that current ?owing
by lead l8 to negative terminal of battery B so
through ?eld winding F2, or the circuit of plate
as'to carry the same potential as electrode l3.
P2, and the distance of electrode l3 from central
Cathode l5, located within tube T between and
position, on the right side of central position,
'in- alignment with electrodes l3 and I4, is con
nected by lead 2l to the midpoint 23 of battery 15 increase in inverse order,'until, of course, all of
beam B2 is de?ected from plate P2. ‘Since elec
B and' grounded at l9. ‘
4
tron beam_Bl substantially is ‘unaffected by any
There ‘are two anode plates, PI‘ and P2 mount
movement of electrode l3 to the right, plate cur
ed respectively at opposite ends of and within tube T at-points substantially equidistant from - rent in the circuit of plate Pl and ?eld winding
(cathode- IS. A circuit is traced from midpoint 20 Fl remains substantially constant. It follows,
then, that for movement of the indicating ele
23 of 'batteryvB, lead 2l to cathode l5, across
tube T to anode. plate P2, lead 28, across motor , ment l2 on the right side of central position, the
distance of electrode l3 from central position
?eld winding F2 of the following unit and lead l1
representing the magnitude of deviation between
to'positive terminal 26 of battery B. A second.
‘circuit iswtraced from midpoint 23 of battery B,‘ 25 the indicating element and the following unit,
the unbalance of the currents in ?eld windings
lead 2| to cathode l5, across tube T to anode
- FI and F2, ‘and the velocity of motor 21 of the
plate Pl, lead it, across motor ?eld winding Fl
of the following unit and lead H to‘ positive 'ter-w _ following unit, allincrease in direct proportion.
On the other hand, when electrode l3 moves to
. minal 26 of battery B.
In‘ the present embodiment of my invention, 30 -.the left side of central position, plate current in
thecircuit of plate P2 and ?eld winding F2 re
I apply the principle that cathode raysare re
mains substantially constant. Until all of beam
pelled or de?ected by external charges of nega
-BI is de?ected below. plate PI by electrode 13,
tive electricity. This principle is employed more
the current ?owing through Fl increases inverse
particularly in controlling the driving of motor
ly as the displacement distance of'electrode l3 to
21 of the following unit. Cathode beams or rays
the left of central position; it follows, therefore,
‘Bl, B2, passing from cathode l5 to plates Pl
_ and P2, respectively, are controlled by electrodes
l3 and H charged with ".he same high potential
negative electricity. Normally the instrument
pointer or indicating‘element l2, carrying elec
. trode
that as displacement of electrode l3 to the left
of central position increases, current unbalance
in the’ windings FI and F2 and the speed of the
40 motor 21 of the following unit both increase pro
portionately.
.
I
l3, rests at central position, at which '
position, cathode l5 and electrodes l3 and I4
' are in alignment.
Upon ‘the indicating element
. l2 being at central position, electron beams BI
and B2 come equally into focus upon plates Pl
‘ and P2, respectively.
This is understood‘more
clearly by observing that cathode I5 is connected
through lead 2| and midpoint of battery B to
ground at l9. Electron beams Bl and B2 of
equal intensity pass from cathode IE to anode
plates PI and P2. respectively. Current ?ows
. in the circuit traced from anode plate P2, through.
lead 28, ?eld winding F2 and lead l1 to positive .
terminal 26 of battery B. 'At the same time,‘ a
Movement of indicating element l 2 to the right
of central'position causes a greater current to
?ow through winding Fl than in F2. On the
other hand, de?ection of indicating element l2
to the left of central position causes a predomi
nating current to ?ow through winding F2; Ac
cordingly, it can be seen that driving motor 21
reverses when the indicating element crosses cen
tral position. The reversible driving motor is of
sumcient horsepower to position the following
unit as indicated by the signal or current differ
ential created by the de?ection of indicating ele
. ment l2.
For training large turrets, whichre
substantially equal current ?ows in the circuit
traced from plate Pl through lead l6, across‘
a ,motor ?eld winding Fl, and lead l1 to positive
terminal 26 of battery .3. Thus the opposed
windings, Fl and F2, forming the ?eld motor
quires more than several horsepower, reversible
since they are in the plate circuits of tube T,
and there is no current differential to drive fol—
ducing a speed of 'the following unit driving mo
tor proportional to the deviation. I prefer the
above embodiment, but others known in the art
motor 21 could be adapted to control a motor of
much greater power, as, for example,through a
relay system, to position the turret correctly.
The above description details one essential ele
_ 21 of the following unit, carry equal currents 60 ment of my invention and is a device for pro
lowing unit motor 21.
-
When negative electrode I3 is moved to the
may be used.
'
right of central position by counterclockwise ro 65 _In addition to the above element‘, 1 incorporate
an element which stops the following unit driving
tation of indicating element l2 about point l0,
motor, and thus the following unit, when the de
electron beam B2 is repelled by electrode l3 and
viation has reached zero. One embodiment of
part of the beam no longer strikes plate P2.
this is as follows‘: It is to be observed from Fig. 1
Current ?owing in the circuit traced from plate
P2 through lead 28, ?eld winding F2 and lead 70 that where indicating element l2 moves away
from central position, driving motor 21 is driven
"to battery Bfaccordingly, is decreased. Mean- _
while, electronvbeam Bl still is ‘focused in its
substantial entirety upon plate Pl with the result
that current ?owing through the circuit de?ned
_ by lead It, ?eld winding Fl and lead l1 to battery
by the unbalanced currents coursing through ?eld '
windings Fl and F2. Movement of the indicating
element l2 toward central position retards the
following unit motor and the motor stops when
2,411,750
7 .
8
central position is reached. In order to stop the ‘
following unit motor when the deviation between
electrode l3 from central position. Current ?ow
following unit and indicating element l2 has
reached zero, reset mechanism is provided as il
lustrated in Fig. 2. My basic following unit con
ing in the circuit de?ned by plate P2, lead 28,
winding F2 and lead H to battery B, accordingly
is decreased. Movement of electrode l3 to the
.right has little effect upon electron beam Bl
which, therefore, remains in focus fully upon an
trol circuit described with reference to Fig. 1, also
ode plate Pl. The current ?owing in the circuit
is employed in the control mechanism illustrated
de?ned by plate Pl, lead l6, winding Fl, and lead
in Fig. 2. In addition, driving motor 2'! drives a
I‘! to battery B, remains high and substantially
following element through shaft 30, gear 3| and
gear 32, at a velocity in ?xed ratio to motor ve 10 constant. A predominating current, therefore,
?ows in the circuit of plate P2, and winding Fl,
locity. A reset disc 35 to which cathode ray tube
and following unit motor 2'! starts driving in an
T is a?ixed, is driven by the motor 21 through
opposite direction as compared to the direction
shaft 29, bevelled gear 38 mounted on shaft 29,
of response of the motor to a current unbalance
bevelled gear 31 mounted on worm shaft 33, Worm
set up by, movement of electrode l3 to the left
shaft 33, worm gear 34 and gear teeth 36 or disc
of central position. At the same time, motor 21
35.
begins driving reset disc 35 and cathode ray tube
In operation, assume that indicating element l2
T in a clockwise direction and electrode l4 and
moves to a signal pos’tion on the left side of its
cathode l5 slowly approach alignment with elec
central position, thereby creating a deviation be
tween the following unit and the indicating ele 20 trode l3. The de?ecting effect of electrode l3
upon electron beam B2 slowly diminishes, and as
ment. Electron beam Bl is de?ected downward
this occurs, beam B2 rises slowly, coming more
an amount proportionate to the displacement of
and more into focus ‘upon anode plate P2. Cur
the indicating element or to the deviation of the
rent through the circuit of plate P2, including fol
following unit. Current ?owing in the plate cir
lowing unit motor ?eld winding F2, gradually in
cuit traced from anode plate Pl, through lead l6
creases and ?nallycomes into balance with cur
across winding Fl, and lead I‘! to positive termi
rent ?owing through winding Fl, in the circuit of >
nal 26 of battery B, accordingly is decreased.
plate Pl, when the tube T reaches central posi
-tion with respect to electrode l3. Since balanced
' tially full focus upon anode plate P2 and a pre
dominating current ?ows in the plate circuit 30 plate currents coursing through windings Fl and
F2 leave no differential of current to drive the
traced from P2 through lead 28, across winding
following unit motor 21, the following unit, there- '
F2 and lead I‘! to positive terminal 26 of battery
B. The unbalanced currents ?owing in the plate _ fore, comes to rest. Again it must-be observed
that currents through ?eld windings Fl and F2
circuits of'plates PI and P2 cause following unit
tend more and more to balanceas the deviation‘
motor 21 to drive'reset disc 35. As following unit
of the following unit from indicating element l2
motor 21 continues to drive, reset disc 35 and
decreases. As before, currents and ?eld windings
cathode ray tube T rotate at a decreasing rate
Fl and F2 linearly approach balanced condition
in a counterclockwise direction; thus, electrode
as deviation between indicating element and fol
l4 and cathode l5 are rotated gradually toward
lowing unit decreases. It'followsonce more that
central position, that is, to alignment with elec
motor speed decreases proportionately with the
trode l3 on indicating element l2.- The follow-.
ing unit motor also drives'the following unit so
With the reversible basic motor control circuit
as to overcome the deviation existing between
and reset mechanism described hereinbefore,-dis
the following unit and indicating element' l2. By
placement of indicating ‘element l2 from central
rotating the electron tube '1“, the effect of elec
position in 'either directiondecreases with proper
trode [3 on beam Bl gradually decreases with the
rotation of cathode ray tube T and the speed of
result that more and more of electron beam Bl
the following unit also decreases. The motor 21
falls into‘ focus upon plate Pl. Since electron
acordingly,‘is eased to a halt as cathode ray tube
beam B2remains substantially in complete focus
Meanwhile electron beam B2 remains in substan
deviation.
'
,
upon plate P2 throughout the counterclockwise '
T is rotated to central position with respect to in
rotation of reset disc 35, the current in the cir
dicating element l2.
cuit of plate P2 and winding F2 remains high and
'
As plate currents in Fl and F2 become bal
substantially constant. On the other hand, cur
rent ?owing in the circuit of plate PI and follow
ing unit motor ?eld winding Fl gradually in
creases with the rotation of reset disc 35 and the
anced, it is possible that inertia gained by the
following unit while driven to signal position, at
a velocity in ratio to motor velocity, by motor 21,
unbalance of currents ?owing through windings
yond signal position. When this occurs, tube T
is rotated beyond central position with respect
to indicating element l2. Currents in windings-_
Fl and F2 diminishes slowly until an actua1 bal
ance of currents is obtained and following unit
motor 21 comes to rest.
It can be seen, there
fore, that currents through ?eld windings Fl and
F2 tend more and more to balance as the devia
tion of the following unit from the indicating ele—
ment l2 decreases. Currents in ?eld windings Fl
will cause reset disc 35 and tube T to rotate be
60 Fl and F2, accordingly, become unbalanced by. 1
overshooting of the following unit, and the fol
lowing unit motor 21 reverses in response to the
overshooting. As a result, __the following unit
oscillates or hunts about the point. where it
‘
and F2 approach balanced condition as deviation 65 should come to rest.
In short, I have described above embodiments
between indicating element and following unit
of a speed-proportional-to deviation device, and
decreases. It follows, then, that motor velocity is
a reset device, to stop the motor at deviation zero. I
proportional to the deviation and decreases pro
Other embodiments may be used. But bothv these
portionately with the deviation.
.
After the following unit has come tov rest from 70 elements may not be enough under given operat
the last signal, assume now ‘that indicating ele
ing conditions. Therefore, I apply in’ addition,
ment l2 and electrode l3 are moved to the right
a ?rst derivative correction, one novel embodi
of central position with respect to cathode ray
ment of which is as follows:- ‘Referringnow more
particularly to Fig. 3, it will be noted that I con
tube T. Electron beam B2 is deflected downward
an amount proportionate to the displacement of 75 nect a variable resistance‘45 across-tube plates
acrimo
'
10
PI and P2 and across ?eld windings FI and F2
illustrated in Fig. 4, wherein rotation of the fol-
of the following unit motor 21. These connec:
tions are traced from plate PI acrosslead I5 up
lowing unit-is plotted in the ‘ordinate against a
- time of rotation abscissa.
'
Curve A represents
following unit‘approach to a given signal posi
tion of indicating element I2, when my- damping
current correction proportional to the rate of
P2. I connect condenser 43 across resistance 45,
change of deviation is applied to one of the fol
which connection is traced from point 41, lead 45, ~ lowing unit motor windings FI- and F2. Curve
to junction 40 of winding FI, thence over leads
42 and 45,'across variable resistance 45, lead M.
to junction 48 of winding F2 and lead' 28 to‘plate
condenser 43', selector 44 to resistance 48. '
B shows the manner in which a following unit
Now it must be noted that the distance of- in 10 control system having no correction current per
.dicating element I2 from central position and
mits hunting of the following unit about a ?xed
the differential of voltage across the circuits of ' . signal position. Curve B, therefore, represents
plates PI and P2 vary in direct proportion.
the operation of such apparatus as is disclosed
Moreover, the rate‘ at which the position of in
' in Fig. 2 where no overshooting correction is
dicating element I2 changes with respect to cen 15. applied and the speed-of the following unit motor
tral position, thus the rate of change of deviation
is proportional to the deviation between following
between the following unit and indicating ele
unit and indicating element. Curve C illustrates
ment I2, and the rate at which voltage‘ changes
following unit approach to signalled position
across the circuits‘ of plates PI and P2, all vary
when a motor control system comprising com
in direct proportion. Current through condenser 20 plicated superimposed ?rst and second derivative
43, therefore, is proportional directly to the rate
motor damping means is employed.
'
.of voltage change between the plate circuits PI
- The variable resistance element 45 permits
and P2 and therefore also is proportional to the
ready adjustment of the correction current
rate of change of‘ deviation between the follow
draining through condenser 43 and thus, my con
ing unit and the indicating element I2. _
To illustrate how the following unit motor 21
25 trol device can be regulated to ensure well
damped, asymptoticapproach of the following
is damped by the. correction current discharged
unit to signalled position under different types of
_ by condenser 43, assume that‘ indicating element
working conditions.
Now, where following .unit control mechanism
is needed for controlling a following unit respond
I2 is deflected to the left of central position.
' Electron beam BI in part is repelled from plate
PI by negative electrode I3, and current decreases
in the plate circuit of plate PI. Current in the‘
plate circuit .of plate P2 remains substantially
una?ectéd by de?ection of electron beam BI.
Therefore, more current ?ows in ?eld winding
F2 than in winding Fl and following unit motor
2‘! begins driving the following mechanism, in
ing to predominantly small signals at low veloc
it)’. particularly where friction and other factors
prevent constant, acceleration of the following
‘unit, a correction of the ?rst derivative type just
described. is adequate to produce well-damped
approach of the following unit to signalled posi
tion. When larger signals, and consequently,
proportion to the de?ection of indicating element " larger velocities 'of the following unit are ‘en
I2, that is, in proportion to the deviation of the
countered, or when the following unit is heavy,
following unit.- Reset disc 35 and tube '1‘ are 40 large amounts of energy are stored in the unit.
driven in a. counterclockwise direction by motor
Such energy must be attenuated for the follow
21 and the deviation of the following unit from
ing unit to have a well-damped approach to sig
indicating element I2 gradually decreases, as de
nal position. 0n the other hand, for, practical
scribed more fully with‘ ‘reference to Fig. 2.
purposes, friction in the controlled elements is
Meanwhile‘, current discharges from ‘the circuit . negligible at such velocities and acceleration rel
of plate P2 across condenser 43 and resistance 45,
atively is constant. I ?nd, therefore, where the
into the circuit of plate PI and the unbalance
deviations are large, that an overshoot anticl
of currents ?owing through ?eld windings FI
pation correction applied to the following unit
and F2, accordingly, decreases. It must be re
motor in proportion to the square of following
membered that the correction current ?owing 50 unit velocity gives a-more nearly asymptotic ap
across condenser 43 is high when indicating ele
proach of the following unit to signalled position.
ment I2 is ?rst moved to left position, and the
One embodiment of my invention, in accordance
following unit, reset disc 35 and tube Tare mov
with this principle, is illustrated in Fig. 5 of
ing toward signal position at high velocity. ‘The
the drawings.
'
,
applied correction current is proportional to the 55 It will be noted in Fig. 5, that my basic fol
rate of change of deviation between the following
lowing unit motor control circuit and reset
unit and the indicating element. As reset disc
mechanism described more particularly with ref
35 and tube T are driven by motor 21 to central
erence to Fig. 2, are shown in combination with
position with respect to indicating element I2, .
overshooting control apparatus. My overshoot
the speed of motor 21, as described with reference 60 ing control apparatus is provided with a shaft 50
to Fig. 2, decreases, and the correction current
across condenser 43, accordingly, decreases, but
this correction current, nevertheless remains
proportional to the deviation. It must be under
stood that discharge of condenser 43 reverses
when indicating element I2 is de?ected to the
right of central position. In any event, whether
indicating element I2 moves to the right or left
of central position, the correction current ?owing
across condenser 43 is applied in'proportion to
the rate of change of deviation in anticipation of
the following unit overshooting signalled posi
tion.
The manner in which such over-run correction
extending from following unit motor 21 which
shaft is mounted in bearing 5|. At the end of
shaft 50, remote from motor 21, is mounted a
watt-meter type magnet 52. A shaft 57 sup
ported in bearings 54 extends coaxially from shaft
50. Disc 58 is secured to the end of shaft 51
and is free to revolve in the gap of magnet 52.
Meter-type coil springs are attached to shaft 51
and to bearings 54 to retard rotation of disc 5i!v
70 in either direction. Upon driving the following
unit as described more particularly with refer
ence to Fig. 2 of the drawings, shaft 50 and mag
net 52 rotate in ratio with the following unit
motor. Magnet 52 exerts a drag upon the con
current prevents hunting of the following unit is 75 ducting disc 58, and the disc, accordingly, re
2,411,750
11
'
volves an angular distance proportional to the
velocity of following unit motor 21.
Rotary-type variable resistor 59, wound ac
cording to a square-law or current square taper,
12
velocity of the motor and thus that of the ratio
driven following element are decreased gradually
’ by a slow ‘balancing of plate currents is the cir
cuits of plates, PI and P2.
This is accomplished
has a contact arm 56 fastened to disc 58 at ‘point Cl rby the reset mechanism of which the motor and
reset disc 35 are parts. The motor stops when
65. Field windings Fl and F2 of motor 21 are
central position of the reset mechanism is
connected across variable resistor 59. One cir
reached. Throughout the period of gradual de
cuit is traced from battery 6!, over lead‘ 62, lead .
crease or increase of following unit motor veloc
l1, across ?eld winding ~Fl, lead 64, resistor 59,
contact arm 56, lead 51, variable resistor 66 and 10 ity, a correction current is applied'across resistor
59 to one of ?eld windings Fl and F2, to prevent
lead 66 back to battery 6|. Another circuit is
the following unit from overrunning signalled
traced from battery 6!, over lead 62, across ?eld
position. This correction current varies in direct
winding F2, lead 58, across variable resistor‘ 59,
proportion with the square of following unit ve
contact arm 56, lead 61, variable resistor 60 and
lead 66 back to battery 6l.
‘
15 locity, and is applied to decrease unbalance of
currents between‘ windings Fl and F2 in accord
While following unit motor 21 is at rest, con
ance with a velocity square law, until the follow
tact arm, 56 remains at position 55 on the var
ing unit motor comes to a well-damped rest, at
iable resistor 59, and equal, but opposed currents
which time there is once more a complete bal
flow from battery 6i through resistor 59 and ?eld
windings Fl and F2.
. 7
Upon indicating element l2 being deflected to
ance of currents in the ?eldywindings of the mo
tor. When indicating element I2 is moved to
the right of central position, it will, of course,
be understood that my apparatus functions in
rent‘?ows in the circuit of plate P2 and ?eld
a fashion similar to that, just outlined, except
winding F2, as described more particularly here
inbefore. Motor 21 drives at a velocity propor 25 that motor 21 reverses and the correction cur
rent is applied through resistor 59 across ?eld
tional to the displacement-0f indicating element
winding F2.
,
l2 from central position, that is, proportional to
Fig. 6 of the drawings illustrates following unit
the deviation between indicating element l2 and
control apparatus comprising a combination of
the following unit. At the same time, reset disc
35 and tube T are driven in a counterclockwise 30 the two following unit overshoot-preventing con
trol systems more speci?cally described herein
direction through gearing 36 and 34', shaft 33,
before. As the following unit motor responds to
gearing 31 and 38 and shaft 29 by following unit
large signals, I prefer to use a motor control sys
motor 21. The velocity at which the reset mech
tem of the type illustrated in Fig. 5, with which
anism is driven by motor 21 also is proportional
to following unit deviation or to the displacement 35 an overshoot anticipation correction is applied in
ratio to and directly proportional to following
of indicating element l2 from central position.
unit velocity squared. When the following unit
Consequently, as the reset mechanism is driven
motor responds to small signals, I prefer to em
toward central or neutral position, the velocity
ploy a motor control'system of the type more spe
of the following unit decreases.
vWith the initial movement of indicating ele 40 ci?cally described with reference to Fig. 3, where
in an overshoot anticipating correction current
ment l2 to left of central position, following unit
proportional to the‘ rate of change of devia‘ion
motor 21 starts driving shaft 50 and magnet 52
between the following unit and indicating ele
at a velocity in proportion to the signal. Magnet
ment I2 is applied to the following unit motor.
52 exerts a drag upon disc 58, and the disc along
For detailed operation of the respective mech
with shaft 51 and contact arm 56 rotate in pro
the left of central position, a predominating cur
portion to magnet speed.
Contact arm 56 is dis-'
placed, in the proper direction; from its neutral
position 55 to vary the resistance across resistor
59.. Resistance to the current flowing from bat
'tery ‘6|, across ?eld winding Fl, accordingly, is ;
decreased. The potential of plates PI and P2
across windings Fl and F2, therefore, decreases j
and this results in a decrease
current driving
following unit motor 21.
anisms, reference is made more particularly to
the previous description herein of Figs. 3 and 5.
In accordance with the present embodiment of
my invention, I connect an electrical quotient me
ter 10 across plates PI and P2 of a cathode ray
tube of the type described her‘einbefore. The
electrical quotient meter 10 operates on the ratio
of the two plate currents of plates PI and P2. A
spring-restrained indicator shaft 15 driven by me
It must be recalled that velocity of following ~ ter 10 carries switch elements ‘I8 and 19. When
following unit motor 21 is not operating, or when
‘unit motor 21 and thus the velocity of the motor
a small potential exists across ?eld windings FI
and F2 of this motor, switch element 19 closes the
circuitacross contacts ‘I6, l1 and a motor over
driven in a counterclockwise direction toward
central position with respect to indicating ele 60 shoot anticipating system'of the type described
with reference to Fig. 3, is brought into opera
ment ‘[2. As following unit motor velocity is
tion. Therefore when the motor is operated by
decreased by the reset ‘mechanism, the energy
a small current differential, a correction current,
correction current coursing from battery 6| across
driven following element are reduced primarily
by reset disc 35 and‘ cathode ray tube T being
variable resistor 59 and ?eld winding Fl also de
proportional to the rate of change of deviation '
This decrease of correction current oc 65 between the following unit and indicating ele
ment [2, therefore, is applied to one of the ?eld _
curs because the resistance across resistor 59 in
creases.
creases in direct proportion with decreasing fol
windings Fl, F2 of following unit motor 21.
Assume, now, that indicating element I2 is
lowing unit motor velocity. -' Since resistor 59 has
moved from central or neutral position so as to
a square law current taper, the current ?owing
across it to ?eld winding Fl varies‘ in direct pro 70 produce a predetermined degree of unbalance in
the circuits of plates PI and P2. Assume, fur¢
portionv to the square of the velocity of the fol
ther, that the ratio of unbalanced plate currents,
lowing unit motor. The ratio of current to ve
locity ‘is varied'by adjustment‘ of variable re
I or the power ratio of these currents, exceeds a
predetermined amount, requiring that the fol
It is to be understood clearly, therefore; that 75 lowing unit be driven more than 21/2", forexam
sistor 60.
'
'
‘
13
2,411,750
pie, by the following unit motor to reduce fol-'
lowing unit deviation to zero. Meter 10 turns
i4
'
'
‘ J
good results under certain circumstances. More-s
over, a following unit motor overshoot preventing
spring-restrained shaft 15 in one direction or the
system comprising a ?rst time derivative of de-..-. '
other, depending upon which plate circuit of
plates PI and P2 carries the lowest current.
viation control means and a velocity square con- ‘
Switch element 18 closes either a circuit across
contacts ‘H, 12 or a circuit across contacts 13, 14
to bring into operation following unit overshoot
preventing apparatus of the velocity-squared type
trol means for applying corrections to the follow
ing unit motor, with means for switching auto
matically from one of these controls to the other,
has a wide range of application in the'remote'
control art. With the latter combination, over
described more particularly with reference to Fig.
5. At the same time, switch element 19 is rotated
away from contacts 18 and ‘I1, cutting out the fol
shooting of signalled position by the following
?eld windings Fl, F2 of motor 21. As reset mech~ .
or hydraulic means,» for example, may be em- ‘
unit is prevented whether the following unit is
heavy or light, or whether the velocity of the
following unit is high or low.
lowing unit overshoot preventing system which
It is to be understood quite clearly that my
applies a correction current proportional to the I
basic control or intermediate control system is
rate of change of deviation between the follow
not limited‘to an electrical device. Mechanical,
ing unit and indicating element-12,.to one of the
ployed to control following unit motor speed in
anism_ and the following unit of the type de
proportion to the deviation existing between the
scribed in Figs. 2 and 5 are driven toward central
position or signalled position, it will be noted, ‘by 20 following unit and the indicating element. More-_
over, other mechanism, including mechanical or
particular-reference to the description of Figs. 2
hydraulic means,'for example, maybe employed
and 5, that velocity of the following unit motor
to apply the ?rst derivative of deviation correc
21, and the velocity of the following element
tion, or .the velocity-square correction to the fol
which is in ratio to motor velocity, accordingly,
decrease in direct proportion to the magnitude of 25 lowing unit in order to maintain overshooting
and hunting at a minimum. Where the ?rst
the deviation. A damping current, however, is
time derivative of deviation correction and the
applied to reduce motor ?eld current ‘unbalance
velocity-square correction are applied in se
in proportion to the square of the motor or fol
' lowing unit velocity, as described more particu
quence, automatic switchover from one correc
larly with reference to Fig. 5. When signal cur 30 tion to the other may be accomplished by appa-_
ratus which responds to a particular power limit
rent differential of the plates PI and P2 decreases
to the predetermined amount or ratio, as, for ex
or to a particular ratio or unbalance of power
driving the following unit. The switchover ap
paratus 'may be of mechanical, electrical or hy
loaded shaft 15 overcomes the torque exerted by 35 draulic type, for example, without departing from
the spirit of my invention.
‘
meter 10 and switch element 18 rotates away from
My invention has valuable application also to
contacts ll, 12 or contacts ‘I3, 14, as the case may
control systems for controlling process conditions,
be, cutting out the motor overshoot preventing
such as temperature, salinity and the like. For
system of the velocity-squared type. Meanwhile,
switch element ‘19 closes a circuit across contacts 40 these applications, a pyrcmeter pointer, salinity
ample, when following unit deviation is reduced
to the predetermined deviationof 21/_>°, spring
‘l6, ‘l1 and the overshoot preventing system de
scribed more particularly with reference to Fig. 3,
functioning ‘in direct‘ proportion to the rate of
change of following unit deviation comes into
operation. Therefore, a re?ned correction cur
rent proportional to the rate of change of devia
tion is applied to one of the ?eld windings FI
and F2, until following unit motor 21 and the fol
lowing unit are brought to a well-damped stop
meter pointer or the like serves as the indicating
element. ‘Thefollowing unit is a recorder motor
or just a motor alone, made powerful enough to
drive a low-inertia valvefor' controlling the flow
of medium to restore a desired process condition.
The deviation of the motor from desired process
condition, accordingly, is reduced automatically
to zero. The motor provided is so powerful that
its inertia is the predominant characteristic to .
by the reset mechanism and basic control circuit, 50 be controlled rather than the negligible inertia
of the valve. By applying my principle of ?rst
more particularly described with reference to
time
derivative of deviation motor control and
Figs. 1 and 2:
switching automatically, to velocity squared cor
I ?nd that thebasic control system of my in
rection on large deviations, a desired process con
vention, one embodiment of which is illustrated ,
in Fig. 2 of the drawings, is mechanically simple 55 dition will be approached asymptotically, as in
controlling amount, without overshoot or hunt
and economical to construct. The system is high
ing. This is particularly valuable in processes
ly sensitive to movement of the signalling or indi
where large batches of material are. dumped into
cating element giving a signal which varies ac
the process suddenly. Say, for example, a batch
curately in direct proportion to the deviation of
the following unit from the indicating element. 60 of cold milk is dumped into a pasteurizing tank.
A sudden ?uctuation in controlled temperature
It is to be understood quite clearly that the un
condition occurs, and the regulator, when coupled
balanced currents ?owing across my cathode ray
with a pasteurizing tank thermometer and. a
tube system may be applied in numerous ways to
steam heat supply valve of' ‘the tank, gives an
drive the following unit motor, the opposed mo
asymptotic restoration of tank temperature to
tor‘ ?elds described herein being one illustration.
desired value.
Similarly, good ' results are
Instead of driving the following unit motor di
achieved when, my control system is employed
rectly, it is to be further understood that the un
for controlling conditions such as humidity, pres
balanced plate currents may be used to operate a
sure, liquid, level, rate of flow of ?uids or elec
relay system for controlling larger currents or a
70 tricity, voltage, frequency ‘and the like.
larger motor.
As many possible embodiments may be made '
Either my following unit control system which
operates in proportion to the rate of change of ' of my invention and as many changes may be
made-in the embodiment hereinbefore set forth,
following unit deviation, or my system which
it is to be understoodthat all matter described
operates in proportion tothe square of the fol-_
lowing unit velocity, may be used separately with 75 herein or shown in the accompanying drawings,
2,411,7oo
18
is to be interpreted as illustrative and not in a
time derivative of deviation correction to the driv
'limiting sense.
ing motor to reduce the motor velocity,when said
I claim:
deviation decreases to a small amount, and auto
matic switching means associated with said op
1. A control system of the class described, com
prising, in combination, an indicating element l1 posed energizing means to switch out one of the
adapted to be moved to produce a deviation be
correction applying means and to switch on the
other thereof.
"
tween it and a following unit, the latter having as
an element thereof a driving motor for reducing
5. A control system of the type described, com
deviation of said unit from said indicating ele
prising, in combination, an indicating element
ment, means for energizing said driving motor, 10 adapted to be moved to produce a deviation be
means for maintaining the velocity of said driv
tween it and a following unit, the latter having as
ing motor proportional to the magnitude ofthe
an element thereof a driving motor for reducing
deviation between the following unit and said
deviation of said unit from ‘said indicating ele
indicator, means for applying a correction to the
ment, two opposed motor ?elds for the driving
driving motor proportional to motor velocity
motor, means for producing a degree of unbalance
between said motor ?elds proportional to the mag
nitude of the deviation, means driven by said driv
viation correction to the driving motor to reduce
ing motor for stopping the motor at zero devia
the energy of the motor-when said deviation de
tion,‘means for applying a correction to the driv
creases to a small amount.
'
.20 ing motor proportional to motor velocity squared
2. A control system of the class described, com
to reduce following unit energy; means for ap4
prising, in combination, an indicating element
plying a ?rst time derivative of deviation correc
- squared to reduce following unit energy and
means for applying a ?rsttime derivative of de
adapted to be moved to produce a deviation be
tween it anda following unit, the latter having as
an element thereof a driving motor for reducing
_ tion to the driving motor to reduce the motor ve
locity when said deviation‘decreases to a small
amount, and automatic switching means asso'»
deviation of said unit from said indicating ele
ciated with said unbalance prcdr; ing means to
ment, means for energizing said driving motor, _ '
means for maintaining the velocity of the driving
and
switch
to switch
out one
onof
the
the
other
correction
thereof. applying
‘
motor proportional to the magnitude of the de
viation of the following unit from said indicator, ;.
6, A control system of the class described, com
prising, in combination, an indicating element
adapted to be moved to produce a deviation be
means for applying a correction to the driving
motor proportional to motor velocity-squared to
ing a ?rst time derivative of deviation correc
tween it and a following unit, the latter having as
an element thereof a driving motor for reducing
at a decreasing rate deviation of said unit from
.‘I"'on to the driving motor to reduce the velocity
or‘ the motor when said deviation decreases to a
small amount, aid automatic means for switch
ing from one correction applying means to the
for driving the motor, means for maintaining a
degree of unbalance of currents across said motor
?elds proportional to the magnitude of the devia
reduce following unit velocity, means for apply
other.
said indicating element, two opposed motor ?elds
tion, means driven by said driving motor for stop
I
3. A control system of the class described, com
40 ping the motor, means connected across said un
prising, in combination, an indicating element
adapted to be moved to produce a deviation be
tween it and a following unit, the latter having as
balanced motor ?elds for supplying an anticipat
ing correction current to the driving motor in
proportion to the rate of change of deviation;
means associated with said motor ?elds for sup
an element thereof a reversible driving motor for -
‘ reducing deviation of said unit from said indicat
45 plying a correction current to the driving motor
ing element, means for energizing said driving
motor, unbalanced power means for maintaining
the velocity of the driving motor proportional to
the magnitude of the deviation of the following
proportional to the square of driving motor ve
locity, switch means associated with each of said
correction current supplying means, and a cur
rent ratio meter‘ operatingon the ratio of unbal
. unit from said indicatonmeans for applying a. 50 anced motor ?eld currents for so actuating said
correction to the driving motor proportional to
motor velocity squared to reduce following unit
switch means that one of said correction current
supplying means is switched on and ‘the other
energy, means for applying a ?rst time derivative
of deviation correction to the driving motor to re
switched off upon the departure of unbalanced
' duce the velocity of the motor when said deviation .
decreases to a small amount, and‘ automatic
switching .means operated by said unbalanced
power means to switch out one of said correction
applying means and to switch on the other there
of,
v
currents from apredetermined ratio.
' I
-
7. A control system of the type described, co -
prising, in combination, an indicating element
adapted to be moved to produce a deviation be
tween it and a following unit, the latter'having as
an element thereof ‘a driving motor for reducing
deviation of said following unit from said‘dis
4. .A control system of the class described, com
placeable indicating element; ?eld windings for
prising, in combination, an indicating element
said driving motor; an electrontube having two
adapted to be moved to produce a deviation be
anode plates connected across said driving motor
tween it and a following unit, the latter having as
?eld windings; a cathode disposed adjacent to
an element thereof a driving motor for reducing 65
said electron tube anode plates; a source of energy
deviation of said unit from said indicating ele
so connected to the anode plates andv'tube cathode
; ment, opposed energizing ‘means which when un
that an electron beam, flows between said cathode
balanced drives said motor, means for producing a
and each of ‘the anode plates; said displaceable
degree of unbalance between said opposed ener
indicating element 'being so connected _ to the
gizing means proportional'to the magnitude of the
source of energy and so disposed adjacent to said
. deviation, means driven by said driving motor for
tube cathode that upon displacement, the indi
__,stop'ping the motor at zero deviation, means for
cating element de?ects one of the electron beams
applying a correction to the driving motor pro
causing a motor energizing plate current di?er
portional to motor velocity squared to reduce fol
lowingunit energy; means for applying a, first 75 ential across said, driving motor» ?eld windings
' 2,411,750
17
18
‘between the following unit and indicating ,ele
ment across said driving motor ?eld windings
proportional to the deviation between the follow
ing unit and indicating element.
\
v 8. A control system of the type described, com
whereby the driving motor is energized in pro
portion to said deviation; and a square law vari
prising, in combination, an indicating element
adapted to be- movedto produce a deviation be
tween it and a following unit, the latter having
- able resistance circuit connected across said tube
anode plates for decreasing following unit energy
when plate current differential exceeds a pre
as an element thereof a driving motor for reduc
>ing deviation of said following unit from said _
determined amount.
-
11. A control system of the type described com
displaceable indicating element; ?eld- windings
for said driving motor; a rotatably mounted elec 10 prising‘ an indicating element adapted to be moved "
to produce a deviation between it and a follow
tron tube connected ‘in driven relationship with
ing unit, the latter'having as, an element thereof
the driving motor and having two anode plates
. a drivingmotor for reducing deviation of said
connected across said driving motor ?eld wind
unit from said displaceable indicating element,
ings, a cathode disposed adjacent to said electron
tube anode plates, at source of energy so connected 15 ?eld windings for said driving motor, a control‘
‘circuit for supplying balanced currents across
to the anode plates and tube cathode that~ an
said driving motor ?eld windings, a displaceable
electron beam-?ows between said cathode and
indicating element for unbalancing in propor
each of the anode plates, said displaceable indi
tion to the deviation, between the following unit
cating element being so connected to the source,
of energy and so disposed adjacent to said tube 20 and the‘ indicating element the currents ?owing
through said driving motor ?eld windings there
cathode that upon displacement the indicating
by‘ causing energization of said driving motor
element de?ects one of the electron beamscaus- in direct proportion to deviation between the fol
ing a motor energizing plate current di?erential
lowing unit and said indicating element, ale‘ak
across said driving motor ?eld windings propor
tional to the deviation between the following 25 age circuit connected across said driving motor
?eld windingsfor decreasing the unbalance of
unit and indicating element.
'
‘
?eld currents in proportion to the rate of change
of deviation of the following unit, a ‘square law
9. A control system of the type described, com
prising, in combination, an indicating element
adapted to be moved to produce a deviation be
tween it and a following unit, the latter having as 30
variable current resistance circuit4 connected
across said driving motor ?eld windings for de
creasing the unbalance of ?eld currents in pro
portion to the square of following unit velocity,
an element thereof a driving motor for reducing
deviation of said unit from said displaceable indi
cating element, ?eld windings for said driving
motor, an electron tubehaving two anode plates‘
' switchwmeans in each of. said current unbalance
decreasing circuits, and selector means for open
ing one of said switches and closing the other, _.
12. A control system of the type described, com
connected across said driving motor ?eld wind- "
ings, a cathode disposed adjacent tosaid electron
tube anode plates, a source of energy so con
' prising, in ‘combination, an indicating element
~adapted to be moved. to produce a deviation be
tween it and a following unit, the latter having,
nected to the anode plates and tube cathode that
i‘ an electron ‘beam ?ows between said cathode and
each of the anode plates, said indicating element
40 as an element thereof a driving motor for reduc
disposed adjacent to said tube cathode that upon
ing-deviation of said unit from said displaceable
‘indicating element, ?eld windings for said driving
displacement the indicating element de?ects one
‘of the electron beamscau'sing a motor energiz
connected ‘across said driving motor ?eld wind
being connected to the source of energy and so
motor, an electron tube having two anode plates
ing plate current differential across said motor 45 ings, a cathode disposed between said electron
tube anode plates, a source of energy so con- 4
?eld windings proportional to the deviation be- nected to the anode plates and tube cathode that
tween the following unit and indicating element;
an electron beam ?ows between-said cathode and
and a condenser leakage circuit connected across
said tube anodeplates for decreasing the plate . each of the anode plates, a displaceable indicat
_ current differential in proportion to the rate of 50 ing element ' connected .to the source of energy
change of said deviation.
'
-
10. A control system of the type described, com
prising, in combination, an indicating element
adapted to be moved to produce a deviation be-,
tween it and a following unit, the latter having
as an element thereof a driving motor for reduc
ing deviation of said unit from said displaceable
indicating element; ?eld windings for said driving
motor; an electron tube having two anode plates
connected across said driving motor ?eld wind
ings, a cathode disposed adjacent to said electron
tube anode plates, 9, source of energy so con
and so disposed adj acent to said- tube cathode that
upon displacement said indicating element de
?ects one of the electron beams causing a motor
energizing plate‘ current differential proportional
to the deviation between the following unit and
indicating - element- across said driving motor
?eld windings, proportional to deviation be
tween the following unit and said indicating
element, a leakage circuit connected across
said tube anode plates for decreasing the unbal
ance of plate currents in proportion _to the
rate of change of deviation of the following unit,
a square law variable current resistance circuit
connected across said tube anode plates for de
an electron beam ?ows between said cathode and
each of the anode plates, a displaceable indicat 65 creasing the unbalance of plate currents in' pro
. portion to the square of following unit velocity
ing element connected to the source of energy
and switch means in each of said current unbal- '
and so disposed adjacent to said tube cathode that
nected to the anode plates and tube cathode that
upon displacement said indicating element de
?ects one of the electron beams causinga plate
current differential proportional to the deviation '79
ance decreasing, circuits and selector means for
._ opening one of said switchesad closing the other'
"
9
r
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