US1853069A - Stabilizing apparatus - Google Patents

Description

April 1932- V N. MINORSKY STABILIZING' APPARATUS Filed June 15, 19:51

4 Sheets-Sheet 2 j INVENTOR.

ATTORNEY.

- Pat nted Ap 1 3 meow monsxx, or swurmrom rmsimvam S'IAZBILIZING Application m d June 15,

. This invention relates to improvements in stabilizing apparatus for. ships, submarines, airships and the like. More specifically it re lates to, and has as an object to provide, a V 5 new method and means for timing the action of the stabilizin equipment in response to the combined e ect of the deviation of the system to be stabilized from'its normal non- I disturbed position in space on the one hand, 9 and to the angular velocity, angular acceleration and still higher time derivatives charac- 'terizing the develo ment of the deviation in time, on the other and. Owing to the presence of the higher time derivatives in the stabilizing control, to wit: the first time derivative being angular velocity and 'the second, the angular acceleration, it is ossi- Ible to obtain a dead beat damping 0 free oscillations and to reduce considerably the .amplitude of forced oscillations of the body to be stabilized, whereby a very close stabilization is obtained and the securing of thesev effects is included among the objectsof this invention. V T As a preferred embodiment of this invention I show the application of this method to antirolling stabilization of the ship by means of a movin weight shifted athwartships by a source 0 external ower and exertmg a stabilizing moment about the longitudinal axis of the ship so as-to compensate for the disturbing effect of the wave slope tending to producethe rolling. It is well known that the method of shifting the weight athwartships is. due to Sir J Thornycroft who applied this means for stabilization of a yacht Uecz'le (and published his-results in the Proceedings of the Institution of Naval Architects in 1893). The Thornycroft method of timing the motion of the weight was derived from the angle of deviation of the ship from its upright position obtained by means of two pendulums of which one had the short and the otherthe long periods. The first men- .tioned pendulum wasfollowing the direction of the-apparent and the second of the true gravity. The Thornycroft uipment could quench only about one half 0 the roll owing to the inherent limitations of his equipment. To obviate the deficiency of the is of the first order assumin APPARATUS 1981. Serial No. 544,661.

Thornycroft system is among the objects of thisinvention. a

The present invention is an improvement in and differs essentially from the .Thornycroft idea in that in addition to the purely 55 positional control responsive to the angle of deviation of the ship from its upright position, it possesses, owing to the introduction of controlling means responsive to the.high-- er time derivatives ofthe'disturbin angular motion, an advance of the phase 0% the-Istabilizing action whereb a more accurate {stabilizing effect is obtained. This last mentioned part of control is designated inthe I following as dynamical and its action can be understood from the following elementary consideration: when the ship on rolling passes momentarily through its upright po sition, for example, from starboard'to port,

the angle of deviation is zero at this instant and the weight controlled from this angle, as in case 0 a purely positional control of .the gravity stabilizing equipment, is amidships and hence exerts no stabilizing efl'ect. Owing .to the kinetic energy of -,rolhng the ship swings further to port. In the present invention the presence of the angular velocity control will already have moved the weight to starboard so that when the ship reaches its upright position it has no, or only 99 small, angular velocity-whereby a dead beat stabilization is obtained. Likewise the advantage of the acceleration'al control can be appreciated, from the following: assume that initially the ship is at rest and in the vertical position and that a disturbance, such as solitary wave, for example, begins to act at a given instant. According to dynamics the angular acceleration will deve o in roportion to the instantaneous value o the ing moment since the other effects due to buoyancy and skin friction can be neglected for the conditions assumed i. e. at the very beginning of the disturbance. Boththe an le and angular velocity are small enough at this a point but the angular acceleration generally is proportional to. the disturbance and hence I a parabolic approximation about the initia instant. An

angular acceleration responsive means in this sturbcase theoretically affords a finite controlling action whereas both the angle and the angular velocity responsive means ofler actions of smaller or negligible magnitude; it of fers thus a truly anticipatory action whereby the equipment is made to respond to'the cause (i. e, disturbing moment) rather than i to the efiect," which is the developed angular motion. The accelerational control permits thus to control directly the inertial properties of'the system to be controlledship in this instance-and hence is particularly valuable in all kind of transient disturbances characterizing the actual conditions of the sea.

In general, by considering any disturbance whether periodic or not as a function of time and'expanding it in Taylors series around the given point, it can be shown that the accuracy of predetermination of the controlling action by-automatic equipment is the greater, the greater the number of terms of better understood from this expansion, that is the greater number of higher time derivative responsive means is used, for the control.

More specifically, this invention improves and has as an object to-improve the timing of motion of the weight so that for thesame weighta greater stabilizing action is produced owing to the exact predetermination of the controlling action, above mentioned,

than in case of controlling equipment of the prior art. The influence of this novel method and means for producing an adequate timing manifests itself in the damping out of the free oscillation as well as in reducing the amplitude of the forced oscillation of the ship in a steady state of rolling among harmonic waves. However, as harmonic wave motion is the exception, and non-harmonic transient wave motion is more frequently the actual condition, it will be understood that the utilization of the second and still higher time derivatives for controlling action affords true and complete anticipatory action, as shown above, not obtainable with transient conditions, from angle and angular velocity control alone. k

The above elementary explanation relative to the advance of the phase of controlling action obtained in. this invention can be still the following theoretical explanation.

'It is known that under the assumptions of the general theory of William Froude, now

universally accepted in the art, the difl'er-' ential equation for unresisted rolling among the waves is: v

a=b e sin wt 1 where 0 is the angle of the ships masts with the vertical,

9 is the maximum angle between the normal to the wave profile and the vertical.

m T where T is the apparent period of the waves.

2 l Y b A Where W is the displacement of the ship.

A is the moment of inertia of the ship about the longitudinal axis passing through its center of gravity.

his the metacentric height. v

When a stabilizing weight w is provided on the right side of this equation a term 0% is added representing the stabilizing moment of the weight where and w isthevariable distance between the center of gravity of the moving weight w and the middle line of the ship.

By providing follow up devices either on controlling instruments and on the torque producing means or only on the latter I am able to vary the lever arm a: of the weight-in accordance with the following law: a

do d o' P I I x-m0+n +p (2) where 0 is the instantaneous angle of rolling,

r x i0 J y dt is the instantaneous angular velocity of rolling, 1

is the instantaneous angular acceleration of rolling and m, n, p are suitable coefficients of proportionality characterizing the intensities of the component controls (1) by the angle 0, g

tion of a: into thedi' erential equation-of roll- It is well known from the nature of Equation (3) that in of free oscillations the coefiicient n must be orderto secure the damping negative, which means that when the angula r velocity of rolling 'is from port to starboard, for example, the weight is moved from starboard to port and vice versa. As regards the second coeflicient m there is no such definite indication; it may be either positive or negative. In the original Thornycroft equipment it was positive which means that when the angle of roll is to starboard for example the weight goes-to starboard which can be designated as a downhill control. Q

Assuming for the sake of example that m i 'is negative and designating by N,M, the

the ship;

. absolute values of m, n, one has:

in the expression for the free oscillations of Furthermore the amplitude of the forced oscillations 0 is also decreased as follows from the expression for the particular integral of Equation (3) corresponding to f the given second member.

equipment becomes where 0 .tual modification of we TTWKFnT-"a T 133 (5) is the amplitude of forced oscillations due to wave slope.

- Equation (5) shows that the amplitude of the o rced oscillation is reduced owing to the term with N. The discussion can easily be extended in case the accelerational control isprovided. It also can be shown that the accelerationalcontrol is equivalent to a virthe moment of inertia of the performance of the still more effective both from the standpoint of increasing-the decrement of free oscillations and of the reduction of the amplitude of forced oscillations. It is seen thus that the means responsive to" the dynamical control accomplishes three important functions: .1. Introducing an energetic damping of free oscillations ofthe ship.

2. Reducing the amplitude of forced oscilthe ship whereby lations to a much terms with N and 3. Exerting an early anticipatory action in cases of transient disturbances owing to the higher time derivatives.

greater extent owing to the The stabilizing mean-s forming the subject of this invention furthermore possesses as smooth and continuous action as the primary disturbance itself, which permits of ob taining a close balancebetween the cause (i.' e. external disturbance due to the waves) and the effect e. stabilizing movement of the weight) continuously at any moment. Furthermore both the intensity and the direction of controlling actions in this invention can be varied at will to meet, on different ships, different conditions of rolling, and, for the same. ship, to meet different conditions of weather, apparent period of waves and the like.

It is an important object of theinvention, to provide a substantially electrostatic currentless control of the power circuits actuating the torque exerting plant whereby a continuous regulation of the character described is produced by small high precision delicate avoiding any possible interference with the accuracy of their performance owing to secondary effects of friction ponderomotive forces in the electromagnetic fields, and the like. The performance of the equipment under these conditions is reliable, subject to easy control, adjustment and accurate predetermination. 7

' When'the rolling is too heavy and is outside the range'of the roll quenching capacity for which the stabilizing equipment is deinstruments responsive to. angular motion,

signed, I provide, and it is an object of the invention to provide, emergency 7 means whereby the moving weight is brought to rest at the end of its stroke irrespective of the fact that the angular motion tered by the weight. In such a case thestabiliz'ing equipment functions continuously within its roll quenching range and discontinuously at the end of the stroke. Finally owing to the possibility to adjust the performance to a downhill control a partial regeneration of energy can be secured so that the power plant moving the weight needs to has not been mas supply a comparatively small amount of energy.

Itis an object of the invention to provide, in connection with a rolling weight as the stabilizing agency, a transverse guiding track of suclrprofile asvto maintain a substantially constant load on the power source and to obtain a regeneration of energy owing to the conversion of the'kinetic energy of the moving weight into potential energy of the same weight when raised at theends of itsstroke on the profile and vice versa. Furthermore the profile of the guiding track is such that no damage can occur to the ship in case the stabilizing weight becomes disconnected from its power source. In determining the profile of the guiding track it is preferred to provide a track in which a comparatively small curvature is offered to the weight in the central portion of the ship when'the monism to a car running freely upon it. Con- .ve'rsely the last mentioned property permits of attainment of the inherent safety above referred to, as well as uniformity of the load.

Other important features and objects of this invention will be apparent from the following description accompanied by the 'following drawings in which:

Fig. 1 shows the general arrangament of the stabilizing equipment,

'Fig. 2 shows a detail of Fig.1, Fig. 3 showsthe pendulum control instrument, v Fig. 4 shows a detail of Fig. 1,' Figs. 5 and 6 represent the angular velocity control instrument, I Fig. 7 represents the electrical wlrmg diagram of'the angular velocity control,

' Fig. 8 represents a modification of the stabilizingequipment shown on Fig. 1, Fig. 9 represents the angular acceleration control-circuits, s

Fig. 10 represents a modification of the arrangement shown in Fig. 9,

Fig. 11 represents diagrammatically the.

performance of the arrangement shown in Fig. 10,

. Fig. 12 represents awiring diagram of a.

modified formof the invention particularly applicable to the arrangement shown on Fi 8 L Fig. 13 represents a modification ot the instrument shownv on Fig. 3, particularly adaptable to use with the arrangement shown on Fig. 12, Y Fig. .14 represents a modification of the instrument shown on Figs. -5 and 6, particularly adaptable to use with the arrangement shown on Fig. 12, I

Fig. 15 represents an angular acceleration responsive instrument,

Fig. 16 represents a sideelevation of a cyclo'idal track supporting the moving weight, and

Fig. 17 represents a diagrammatic detail of the electrical follow up member.

Referring to Fig. 1, the moving weight 1 is shown as a block ofmetal capable of rolling athwartships along a track 2 on the wheels 3. The cable 4 (or plurality of cables) causes the displacement of the weight 1 under the influence of pressure developed in the double acting hydraulic cylinder '5 whose iston rod 7 supportson both ends suitable locks of pulleys 6 mounted to form together with pulleys 10, fixedto the ship by means of the brackets 11, multiple sheave A pairs of blocks with one end 8 of'the cable secured i with a hydraulic variable delivery pump 13 driven by a constant speed motor 14 with a fly wheel'15 to equalize the effects of the variable load durin the performance of the set.

The control mem er (sometimes designated as floating ring) 16 of the pump 13 is actedupon by regulating means forming themaili subject of this invention.

It isknown that for a definite angular positioning of the control 16 of the pump, indicated for the sake of example by the angle a, A

from its'middle-position shown on Fig. 1 there is a corresponding definite rate of discharge of the pump, and hence a definite speed of the piston and ofthe moving weight. The reversal of the control member 16 around the zero point reverses the direction of the discharge and hence the direction of motion of the weight. a

A slotted lever 17, pivoted around the point 18 engages a pin 20 concentric with pulley 6 as shown. Displacement of the piston rod 7 secures corresponding oscillations of the lever 17 about the point'18. By means of a system of levers 21 and 19 large displacements .of the piston rod 7 secures corresponding proportionally reduced parallel displacements of the lever 19 through the pivotal connection of the latter at 22 with slotted lever 17. I A lever 23 with the pivotal point at 24, has 1ts opposite end constrained by springs 25. A slotted lever 26 is slidably connected at the point- 27 to the lever 19; the lower end of lever 26 is connected to thei'lower end of lever 23 by means of link 28.

At the point 29 of lever 26 there is linked a lever 30-connected at the point 31 to floating lever 32. The upper end 33 of lever 32 is pivotally mounted on the nut 34 capable of being displaced longitudinally along the screw 35 during the rotation of the latter. The shaft 35 is fixed in driving relation to the planetary system 36 of e'picyclic gears, shown in detail on Fig. 4; the bevel gears 37 38 45", 46; from the same motors through a suitable gearin and shafting 47,48 (Fig. 1.) are actuatedt e shafts 49,50, controlling the follow-up devices on the instruments 51 and 52, res onsive to the angle and angular velocity the rolling, respectively. The instrument 52 controls the excitation .of a generator 53 driven by a motor 54; the armature of the generator 53 is connected tothe armature of the motor 43, by means of a cable 55, the excitation of the motor 43 is constant (not shown) the electric circuits relative to the control of generator 53, motor 43 by the instrument 52 are explained in connection with Fig. 7.

The instrument 51 shown in detail on Fig. 3 is a direction indicating apparatus of long period pendulum type. It may contain gyroscopes (not shown) if necessary in order to increase its period. The pendulum 56 is supported on a knife edge 57 by the arm secured to the pedestal 58 in which is fitted an arc shaped segment 59 having worm wheel teeth on its lower end' with which is engaged the worm 60 connected to the shaft of the motor 44. On the upper part of the segment 59 is.

placed an arc of insulating material 61 with two conducting segments, 62, 63, separated by a short a-rcuate gap 64 ofthe insulator,

porting a metallic trolley wheel 67. The trol-- ley 67 with two segments, 62, 63 controls in the well known manner a relay 68, closing the contacts 69 and 70, of the follow-up motor 41 as shown. The well known property of such a system is that the gap 64 seeks always to reach the trolley 67, around" which posi tion the system oscillates or huntsslightly When the ship rolls over a certain angle 0 to the starboard (for instance) the pendulum 51 remaining fixed in space-the segment 63 is displaced by, the same angle 0 until the gap 64 reaches again the position of the trolley 67. When this is accomplished the motor 44 will have turned through a number of revolutions proportional'to that angle 0 as will also the gear 38, loosely mounted on the shaft '35.

Assume that the other gear 37 is fixed'in i such a case the nut 34 will have'a displacement :1, along the screw 35 also proportional to the instantaneous angle of roll. This follow up actionwill prevail continuously throughout the ships'rolling motion.

By providing suitable means (not shown) for tilting the'frame of the instrument 51, shown on Fig. 3, about the long axis of the ship, I am able to modify the setting of the directional instrument from the upright undisturbed position, to any other predetermined position,--making a certain constant angle of deviation with the former (nondisturbed) setting. In this case the stabilizing this is utilized for the means described in this invention will stabi- ..lize. the .vessel not about its normal upright position, but about. this" redetermined in clined position. This is o importance in all caseswhere a given list must be compensated driven in opposite directions with their casings pivotally mounted within a frame 73 about two parallel axes AA, B.B, placed a'thwartships. Four cylindrical metallic tanks 74, 75, 76, 77, made of metal not at tackable by mercury, are secured to the frame 73 by means of an insulating support 78.

The circular bases of the tanks are made of a resilient material to form dia hragms. Centralizing springs may be adde if necessary in orderto ensure the horizontal position of the gyroscope. The tanks are. completely filled with mercury and have, on their upper parts, each one capillary glass tube respectively, 79, 80, 81, and 82 in communication with the tank with a deposit of a metal nonat-tackable by mercury forming a high resistance film. It is known that the filmsof this kind may have very different values of resistance per unit of theirlength varying from a few ohms up to several megohms depending on the thickness of the deposits they may servefas variable resistors during the variation of height of the mercury column. The respective brackets 83, 84, 85, and

86 are fixed to the respective casings of .the ,gyroscopes as shown and'have the thumb screws '87, 88, 89, and 90, each having a piece of insulating material respectively, 91, 92, 93,

.and 94 at their ends and permitting the adjustment of the initial pressure exerted from the gyroscopes on the .tanks. For a given adjustment and no angular velocity of roll ing the height of the mercury in the tubes 79, 80, 81 and 82, has a certain initial "valuein the-middle of the tube. When the angular velocity of the rolling occurs,the gyroscopic reactions appear simultaneously therewith being proportional to the instantaneous value of this angular velocity, one pair of tanks (76, 77, for example) is therefore compressed and the other pair (74 and-75) expanded,

which causes the rise of the mercury in the capillarytubes 81. 82, and the fall of the mercury in the tubes 7 9,80, in proportion to the instantaneous angular velocity of rolling and purpose of control shown on Fig. 7.

A constant potential difference from a battive to tubes 80 and 82., When there is nov angular velocity of roll and hence no dif :0 for, or an artificial list created as in the case 1'25 tery 95 is impressed on the tubes 79, 80, 81

ference of pressure set up by thegyroscopes in the tanks the potential of the tanks 76, 7

' connected together is the same as. of the tanks 96 rises above, and that of point 97 goes below,

' ,105 is connecte its former equal value. A resistor 98 connected across the same source of su ply 95 has its middle point 99 connected to t e common negative terminal of .the A battery (not shown) feeding the filaments of two three electrode power tubes 100', 101' and the same point 99 being connected to the negative terminal 102 of the plate su ply. The points 96, 97, on the insulated tan'fi systems are connected to the grids of thetubes 100, 101. The plate circuits of the tubes are .connected'in series with differentially wound field :windings 104 of the nerator 53, whose armature to the armature 106 of the motor 43, and whose excitation (not shown) is constant. The generator 53, has another differential field 107 ener 'zed from the, res'istor 108 through the siding contact 109 Eaconnected to the negative terminal 102 of the sup ly and displaced by'the shaft '49 (Fig. 1) mechanically connected with the armature shaft of the motor 43/ For the equal heights ofmercury in the tubes 79, 80,

81 and 82 the grid potentials of the tubes 100,

'101, are equal and themagnetomotive forces of the differential split field 104 compensate each other; 'if at the same time the contact 109 is in the middle of the resistor 108 the magnetomotive forces of the differential field 107 also compensate each other and the 82, as shown, the potential of the point 96 increases, which increases the current in the 'ancing of the differential field 104 of the gentaneous an plate circuit of the tube 100 (by a similar .reaa soning it is seen that the plate current of the tube 101 decreases). This causes the unbalerator, and starts the armature 106 'of the motor 43, which runs through anumber of revolutions corresponding to the displacement of the contact 109 sufiicient to produce an unbalancing of the field. 107 offsetting the original unbalancing of. the field 104. It is seen thus that to a given value of the instanar velocity of rolling corre spondsin a1 result a certain number ofrevolutions of the motor 43. from its zero value. This condition exists continuously hroughout the motionand holds for the intantaneous 'values of' angular velocity, It

is fulfilled .better the 'more rapid is the control. The control (afforded by the three elec trode vacuum tubes of the type disclosed affords these advantages of continuity aswell as rapidity. The last condition is readily understood from thefact that the time constant of an inductive circuit such as the field 104 is" greatly reduced owing to a very high ohmic resistance of the tube inserted in series with such a circuit. I wish'it to be understood that the use of the electron discharge tube cir V I cuits with the arrangement of the tanks disclosed is described by me as an example of a continuous, rapidly-acting control and not in a limiting, sense, since any other 'contr'ol-. ling arrangement satisfying the above stated I conditions of continuity and of the absence o of an appreciable time lag is equally good, for

this purpose. Such alternative construction isillustrated in Figs. 12, 13,14 and 15 and discussed in thedescriptionof those figures which follow'later herein. 1

Summarizing the preceding disclosure one.

can state that the described arrangement has the following properties:

a. To a definite value of the instantaneous angle 0 of rolling there is a corresponding proportional number of revolutions of the motor 44from its zero position, when the angle 0=o, i.- e.-'when the ship is upright. 1

7:. To a definite value of angular velocity of rolling there is a corresponding proportional number of revolutions of the motor 43 from its zero position, when'the angular.

velocity of rolling 4 dt 1s zero- .4

A definite instantaneous state ofmotion is therefore represented in this invention by a I proportional instantaneousdisplacement (d) of the nut 34 from its middle position of the type where the factor of proportionality m contains the ratios of transmission in the system controlled by the instrument 51 and the factor n contams the ratios in the system controlled by instrument 52. The linear combination of both terms moving weight 1 effected by means of the" lever system shown on Fig. 1. The purpose of this lever system is to produce the followthe instantaneous ,013 since the point 31 is fixed initially. A

a ing the For'ade P, by the displacement at .of the weight becomes proportional to that of the nut 34.

A- yen displacement of the nut 34, for v example the left, causes the opening of the control member 16 of the hydraulic pump corresponding motion of the weight 1 for example to starboard is thus star'tedchecking the instantaneous roll to port; The piston 'rod during this phase ofmotion is moving to portjdisplacing also to the left'through levers 17, 19, 26, 30, the point 31 of the floating lever 32, which causes a decrease inthe angularity of this lever and also decreases the angle a Of the control member 16 decreassgeed at which the weight is moving. nite initial displacement of the nut 34 the moving weight will be moved bythe amount necessary to displace the point 31 to the left in order to bring the control member I I 16 back to its middle position which thus stops the wei ht. In reality the initial displace ment 0 the weight causes a decrease in the angular velocityof rolling, which in its turn causes the reverse rotation of the motor 43 and the motion to the; right of the nut 34. f This receding motion of the nut 34 to the right, will contribute still more to the return of the control member'16 to-its neutral position when the discharge of the pump and also the motion of the weightstop: Thus for a definite initial displacement of the nut 34 there is a corresponding proportional displacement of the. oint 31 and therefore of the weight 1, s cient to offset the initial displacement of the nut 34; and stop the disi excessive rolling the stabilizing 5 is pivoted about the point 24. hastwo stops 110 and 111, capable of reach-5 ing the lever 23 for asuflicientl lon excur char e of. the pump b bringing the control member back to its middle position.

"It may happen, however, that owing to an equlpment will not be sufiicient to quench 1t. To meet this emergency the lever 23 is gllovlded-qt 1e lever 19 sion of'the weight and hence o the ever 19.

i Assuming again the previous exam le when the weight, moves to starboard and t e'levers 17, 19 to port, the above emergency cond1- tion will occur when the stop 111.w1ll swing the lower end of the lever 23to port, helping thus tobring the oint 31 more rapidly to port than this woulll happen normally, when the point 112 is stationary. The lever 23 is therefore an emergency means and its function. is to stop the weight near to the end of the track irrespective of the fact that the an lar motion has not been mastered by the The case when the lever23 is acting constit'utes 'a rather abnormal operation of the equipment during very heavy roll. The

. cases when the lever 23 is not working, concontrol ot the inotionoi the weight, whereeight, which is manifested" by a too considerable excursion of the travelling nut 34.

stitute the normal performance ofthe stabiran e.

vention as set out in Fi' s ..1 to 11 inclusive,

I wish now to describet e normal perform- 'lizing equipmentwithin its rollq'uenching Ifaving describedvarious parts of this inance of the device as a whole omitting any intermediate explanations already given in the course of description of the various parts. Assume, for example, that at the initial instant after-a period of a quiescence the. disturbing moment of the wave slope begins'to act on the ship te'ndingto roll it to starboard. f

The gyroscopic reactions of the ,gyroscopes -71, 72,.Ino'dify the level of inercury inthe' tubes in" proportion to the-instantaneous values of angular velocity of rolling and through the vacuum tube system produce the motor 43 and also the epicyclic gear 36 from the bevel gear 37. -With aslight retard the actual deviation 0 of the ship to starboard will developto the extent sufliclent to start the pendulum motor 44 since, on account of rolling, the trolley contact is now on the strip 63 thus closing the relay 68, on the contact 70.

voltage in the generator 53 and start the 1 The pendulum motor will be started to run through a number of revolutions proportional to the angle of the instantaneous roll andthis condition will prevail continuously'throughout the subsequentperformance? If the angle to starboard is designated-as'positive, (that to port as negative), and angular velocity to starboard as positive, (that to port as negative),'this initial condition of this assumed case is therefore characterized by:

as i

and d,- are the partial displacements due'to the angle 0 control and angular velocity I 'dt controls respectively. a

.The stabilizing 1) of the ships oscillation consequently develops a kind of meeting action exaggerating the displacement of the weight as compared to what it would be if the timing were only due to the pendulum.

device during this phase The weight having been'moved very vigorously during this first meeting stage of the the pen counter torque thus decreasing the rate of angular motion to starboard; during this second period 6 is positive and increasing more and more gentlyr dt' v is still positive but decreasing.

The gyroscopic reactions being proportional to the angular velocity of rolling, decrease accordingly, which reverses the rotation of the motor-43. This is the beginning of the easing off period and the-epicyclic gear begins to work difierentially,"viz. while ulum motor 44 is still running in the old direction (since the angle 6 still increases) the angular velocity motor 43 runs in the opposite direction.

An instant later:

0 begins to decrease while still being positive (3) a regerses and gradually increases'in magnitu e.

. During thisperiod;

and the partial displacement d, approaches zero whereas d,,- is very strong and in the opposite (to its original) direction. The

epicyclic gear still works differentially butthe effect of the angular velocity control- .rectly ascertained.

I Wish it to be understood that the preceding description of the invention must not be construed in a-limiting sense since a great.

different stabilizing-, systems may be logica yincluded within the through the bevel gear 37' is far more considerable than the pendulum control throughthe bevel gear .38. v

The displacement of the control nut 34 is now: d=d,'d,- with the second term considerably in excess of the first one; the dis placement d is thus negative, that is to port, which means that the weight is moved to starboard considerably ahead of the. time when the stabilized ship during its return swing (from starboard to port) reaches the.

upright position. This easing ofif efiect manifestsitself particularly in this phase of motion. When the stabilized vessel returns again to the upright position the moving weight is already displaced considerably to starboard so that the ship reaches this uprightposition with no, or only small, angular velocit whereas in the original Thornycroft 'metho for this particular instant the weight was amidships and hence no easing off effect was prov ded.

- The introduction of angular velocity conv trol through the bevel gear 37 thus accounts forth in the above theoretical summary.

-' into the epicyclic gear.

51 is introduced through the bevel gear 38 the above formula 8 it depends on the gear ratios in the follow up and lever systems. Its choice can be best angular motion will produce on the a The pendulum control from the instrument' The coeflicient m in introduces a proportionality between the an- I I gle 0 of roll and displacement of the weight: a

indicated by considerations of statical e quilibrium: w.m== WM where W is the displacement of the-ship hence The angular velocity control is more impor-,

tant from the standpoint of; dynamic conditions, and for the purpose of. adjusting the proper value of thecoeflicient 113, or thermionic emission o f'the three elec-' trode tubes 100, 10 1, or any other regulating means in the series of controlling means be-' tween the gyroscop'es 71, 72, and thefarmature 106 of themotor43. This adjustment can be a test when the 'efiect of a best made during angular velocity on the damping can, he dielectric motor, ahydraulic pump and by draulic motor; in-this ease the weight of this machinery adds up to the roll quenching weight; the arrangement of levers can be inverted since some of the parts, such as control member. 16 becomes moving with the.

weight and some others, such as the point 20 'becomesa fixed pointbut,this reversal of functions of various members is obvious, and can easily be worked out by those skilled the art from Fig, 1.

- Instead of a hydraulic transmission a' regular electric drive can be used. For the sake of example, an arrangement of that kind is shown on Fig. 8. The moving weight 114 contains on its upper part an electric motor 115, a generator 116 driven at a constant speed from the motor 115 and an electric inotor 117 operating at a variable voltage impressed from generator 116 and driving'through a suitable gearing 118, the shaft 119 transmitting the power to two drums 120, 121 actuating the cables 122, 123 displacing the weight athwartships. In this case, the power supply for the motor'117 and for the excitation 124 of the generator must be made either by flexible conductors or by trolley contacts,

or the like. On Fig.8, 1 indicate by 125, 126, contacts establishing the connection between the generator field winding and the bus bars 127, 128, of excitation, whose voltage is controlled by'a suitable controller 129 in response to-angle and angular velocity con- 'trol exactly in the same manner as before trically as will be shown in connection with,

(i. e. lever 32, travelling nut 34, etc.) Still better results can be accomplished when the 'generators field ,is controlled directly by suitable circuits having a continuity of regulation and in which the composition of individual controlling action is produced elec- Fig. 12;

Although I have described a stabilizing system in which the stabilizing moment is produced by the displacement of the weight I wish to be understood that the invention is far more general and applicable to other means of production of stabilizing moment.

- For example the movingvehicles (ships, submarines, airships, airplanes, and the like) can derive their stab hzing torque from vanes v (not shown) suitably positioned and regu-- 'latedon the port and starboard sides of the vehicle and any regulation of these vanes (either by inclining them more or less, or ofi'ering a greater or smaller surface to the medium in which the vehicle is moving) modified the stabilizing torque in magnitude and direction: the principle of controlling the vanes or any other torque'exerti-ng member remains the same, to wit: the mechanism controlling the displacement or rotation of the vanes will either be controlled by a split field of the generator described hereinafter in-connection with Fig. 12 or be controlled by the'travelling nut '34 whose motion is .responsive to .both positional (instrument 51) and dynamical (instrument 52) elements of the angular motion to be neutralized and the actual displacement of the vanes through a system of levers introduces a follow up arrangement limiting the action of the control according to the violence of the prevailing disturbance, manifested by the magnitude of the displacement of. the nut 34.

The presence of the first time derivative (i. e. angular velocity) in the control accounts for damping of the free oscillation of the,

ship and reduces the amplitude of the forced oscillation; but it will be shown by an analysis similar to that carried out in connection with Froude equation that the presence of the second (and still higher) time derivatives (i. e. angular acceleration of rolling, rate of angular acceleration and so on) emphasizes still more these properties by the refinements it affords in the meetin and easing off effectsv in timing the action of the stabilizing agency. In cases when extreme accuracy of stabilization is needed and in all cases where the waves are not strictly harmonic (theusual transient condition) the control by angular acceleration can be added to the preceding so that d0 dO where p is a suitable coeflicient of proportion- I ality between the instantaneous displacement at of the weight (or other stabilizing means) and the angular acceleration. The described system lends itself easily to this additional refinement as shown both in Fig. 9 and in Figs. 12 and 15. On Fig. 9, the tubes 100,

101, and the differential field 104, are1the same as on Fig. 7. In series with the plate circuits are inserted the primaries of two transformers 130, 131, whose secondaries are connected on one side together, and to the common negative terminal of the filament battery (not shown), heating, the filaments of the tubes 132, 133, the grids ofthese tubes are connected to the other terminals of the secondaries of the transformers 130, 131,either directly or through a suitable amplification system. The plate circuits of tubes 132, 133,

are connected to an additional diflerential field 134 similar to the field 104'. "When the plate currents in the tubes 1.00, .101, do not vary and consequently when the angular velocity of rolling is either zero or constant, the currents of the tubes 132, 133, are equal and the resultant effect of the differential field 134 is zero also. When the angular velocity of rolling varies, that is whenthe angular acceleration dtfl v taneous value of angular acceleration of rolling. In view of the followup system afforded by the differential field 107 .this condition is equivalent to an additional term 'd e E? formabletanks, I can use carbon piles, or a resilient variation of air gaps of magnets carrying alternating current or any other ar rangement in which for a given mechanical force there is a corresponding definite value of the current or of electric potential, or any other, either electrical, mechanical quantity which can'be used for the purpose of the control of the type described.

As another illustration of acontinuously acting control responsive to the deviation and to a plurality of the higher time derivatives thereof, I refer to Fig. 12, which discloses a novel system for controlling the field of generator 116,shown on Fig. 8. The disclosed system produces a combination of controlling actions, responsive to the departure.

' of the ship fromits normal position and to the plurality of higher time derivatives of angular motion, in a purely electrical manner wafiecting one single electrical controlling sysuse of hot cathode grid controlled rectifiers tem which I describe in connection with the particularly well adapted for the purpose in view when large powers have to be controlled 7 from high. sensitivity controlling instruments.

Referring to Fig; 12, 150 is the primary of a power transformer having iron core 151 and two secondary windings 152 and 153. 154, 155, 156, 157 are shown as hot cathode grid controlled rectifiers comprising each a hot cathode; a grid and a plate conventionally illustrated, .For the sake of simplicity the heating source of energy for the cathodes is omitted from the illustration. The rectifiers 154, 155, form a two-wave system of rectification, and are connected in a -well known manner, substantially as shown, name- 1y, their respective anodes are connected to the terminals of the secondary 152, their respective cathodes are connected together, and connected to the middle point 158 of fihe load circuit which in this present case is he split field winding of a generator116 (previously described in connection with Fig. 8) comprising the fields 161 and 162. The middle point 163 of the secondary 152 is connected to the terminal of the field-coil 162. The circuitiof the field-coil 162 is thus connected in series with rectifiers 154, 155. An exactly similar arrangement is shown in connection with the secondary 153; rectifiers 156, 157, and associated field-coil 161 of the generator 116. It is apparent that according to whether the group of rectifiers 154, 155, or the group 156, 157,-conduct the major part of the current, either the field 162 or 161 has a predominant magnetomotive force which causes a change of the generated voltage across the brushes of the generator 116 both in magnitude and direction, which causes the displacement of the moving weight as has been previously explained in connection with Figs. 1 and 8. The control of the generator field in this case 'is produced by suitable well known control of rectifiers by the phase shift of the voltage impressed on theirgrids, although any other.

cathodes of the rectifiers, whereas their extremities are connected to the grids of these rectifiers substantially as shown, namely, both ends of the secondary 163'are connected to the grids of rectifiers 154, 155,-and the ends of the secondary 164 are connected to the grids of rectifiers 156, 157. The primary coils 165, 166 of the grid controllingtransformers, are connected to bridges 167 and 168 formed by inductances 170, 1-71, 172 and 173 and capacities 182, 183,184 and 185. In view of the fact that the two circuits associated with each bridge 167 and 168, are exactly the same, description will be made only in connection with one of them, although certain features relative to the interconnections will be described later herein. Each of the bridges comprises the inductances mentioned wound on the iron cores (not shown) which cores are separate for each of said inductances.

.On the same cores are wound coils 174, 175 and 176, 177, carrying.

normally a direct current from a pair of electron discharge tubes, which are illustratively disclosed as three electrode vacuum tubes, 180, 181, and which are connected with the coils as-follows: the plate circuit of the tube 180 is connected in series with the coils 174 of the 4 ready mentioned complete the bridges as indicated. The bridges are connected in parallel and across a source of A, C. voltage between the terminals 187 and 186. The scheme thus far described is known in the art and reprefiers 154, 155, is shifted in one direction, say, advanced, whereas the corresponding time phase of the voltages applied to the grids of Y rectifiers 156, 157, is shifted by a substan- 1'0 tially equal amount in the opposite direction, say, retarded, as compared to the time phase of the anode voltage im ressed on the rectifier system from the trans ormer 150.

' Under these conditions the stabilizing control forming. the subject matter of this pres- 'ent invention may be produced by the grid control of a single pair of vacuum tubes 180 and 181, as will be described now.

For the sake of simplicity, the controlling elements are diagrammatically illustrated .at the bottom of Fig. 12. Their complete description in connection with the instruments producing them, is given below in connection with Figs. 13, 14 and 15. Referring to Fig. 12, 190 represents a. directional control element, whose lateral displacement (along. Y axis) from a central initialcposition XX, is proportional to the angular deviationfl of the ship from its nondisturbed position. In a similar manner an angular deviation of the angular velocity responsive rod 192 about the center 191, from its initial-position along line X X in the plane of the drawings, is proportional to the instantaneous angular velocity of rolling, for this purpose coils 210 and 211 mounted on rod 192, are'placed within alternating magnetic fields 204 and 205 respectively, perpendicular to the plane of the drawings-and acting within the areas indicated by dotted lines. Likewise an angular deviation of the angular acceleration responsive rod 193 with associated coils 212, 213 relative to the magnetic fields similarly shownby projections 206 and .207, about the center 194 from its'initial position parallel'to direction X X is also proportional to. the instantaneous value of angular acceleration of rolling. Finally 199 represents a control element responsive to the magnitude of the stabilizing moment whose lateral displacement along Y-Y axis, from its central position X X is proportional to the displacement of the n Weight or other torque producing mechanism from its central position when the torque is zero.

The controlling elements 190, 199. (see Fig. 12) consist of rectangular plates, made preferably of nonmagnetic and nonconducting material, such as phenolic condensation products,.wood, and the like. Two flat coils 195, 196, shown on the element 190, cbntain a suitable number of turns of preferably thin wire, and are placed within alternating'magnetic fields perpendicular to the plane of the drawing and limited to the dotted areas 197,

198. The magnets producing these fields are not shown on Fig. 12, but are shown on Fi 13. A substantially similar arrangement is shown in connection with the element 199, namely, coils 200, 201, and zones of perpendicular magnetic alternating fields shown by dotted lines 202, 203. All magnetic fields indicated on Fig. 12 diagrammatically, by areas within which they oscillate perpendicularly to the plane of the drawing, are excited from the common source of alternating'current (not shown) and hence they are all in phase with each other. It follows therefore that electromotive forces (E. M. F.) induced in various coils 195, 196, 200, 201, 210, 211, 212, 213 are all in time phase with each other. Their amplitude changes, however, as'a result of the displacements above referred to relatively to the corresponding fields. For

example: when the element 190 moves to the right from its shown position, the amplitude of the electromotive force induced in the coil 195 decreases and that of the coil 196 increases, in view of the fact that the number of the flux linkages through the coil 195 decreases on account of its outward motion with respect to thefield 197, while the inward motion of the coil 196 relatively to the field 198 increases the amplitude of the voltage induced in that coil as the number ofcflux linkages is increased accordingly. Similar relations exist, with respect to the coils 200 and 201 on the element 199 constituting an electrical follow up element equivalent in its action to the lever 30 of Fig. 1, also in the angular velocity responsive coils 210, 211,

and in the angular acceleration responsive coils 212,213, with respect to their associated alternating magnetic fields indicated by areas 204, 205, and 206, 207 respectively, within which the fields are oscillating perpendicularly to the plane of the drawing. One half of the coils'on all four controlling elements are connected in series substantially as shown, for example: Coil 195 of the element 190, is connected with the coil 210 of the angular velocity responsive element, which in its turn is connected to the coil 212 of the angular acceleration responsive element, which is connected to the coil 200 of the follow up control element 199. The circuit of these four coils 195, 210, 212, 200, is connected between the cathode and the grid of the tube 180, and a suitable biasing battery 215 brings the potential of the grid of tube 180 to the desirable point of performance.

A platebattery 216 or other source of poten- 'tial'is connected between the filaments andpma'nner analogous to the coils controlling be interconnected in a similar manner so as p. As regards the follow up (control element, Fig. 3. The performance of the pendulum is its connection (e. g. coil 200). must be so conapparent from the preceding description. In nectedwith the remaining ;three coils 195, fact to an angle pf roll 0 corresponds a rela- 210, 212, that it will continuously reduce the tiv displacement between the pendulum 220 initial electromotive force, which gave rise to and the electromagnets 197, 198 fixed to the themovement of the weight or other stabilizship in the same manner in which in the case ing means. What is said in respect to the of Fig. 3 there appears a relative displacecoils 195, 210, 212, 200, is .equally applicable ment between the to the coils 196, 211, 213, 201, which have to. frame 58.

The angular velocity control described in to control the grid of the tube 181 in a manconnection with member 192 of Fig. 12 is ner similar to that shown in connection with shown on Fig. 14, two gyroscopes supported tube 180. For the sake of clarity this seoinside the casings 230, 231 are mounted on 0nd set of coils 196, 211, 213, 201, controlling trunnions 232, 233, 234, 235 inside the frame the tube 181, is shown to be connected in a 236 ub t nti lly as h n, I r

The instrument is secured to the ship so the grid of the tube 180. Condensers 218, that the plane containing both pivotal axes 217 are shunted across the output of the tubes 232, 23 3, d 234, 235 t be ndi ular 180,181 to eliminate the alternating componvt th l it di al a i of the shi The cut of the plate current of these tubes workgyroscopes are constrained to remain in theing as rectifiers.

I position shown by means of springs not in- The instruments actuating the C-OlltIOlllIlg on 4 On the asings of gyromembers 190, and 199 I'BS POIISlVG tO copes at angles to the trunnions are the angle of deviation 0, angular veloclty ou t d links 238, 239 connected pivotally pendulum 56 and the The directional control corresponding to the element 190 of Fig. 12.is shown on Fig. 13 where 220 designates a pendulum which may 'contain in general gyroscopes (not shown) for the purpose of increasing its a period in the well known manner.

,The pendillumis shown to be supported by the knife edge 221 arranged for oscillation about the longitudinal axis of the ship incase of anti-rolling control. The counterto the casings on one end substantially; as

shown and on the other connected also pivotally to the lever 192 supporting the flat coils 210, 211 already described in connection with-Fig. 12. The areas within which alternating magnetic fluxes act are indicated by dottedlines 204 and 205. The arrangement of the electromagnets producing these fluxes is not shown on Fig. 14 since it is substantially the same as'shown on Fig. 13 and is produced by analogous means. The performance of the angular velocity responsive apparatus shown on Fig. 14 is the same as that of the corresponding instrument shown on Fig.5. The gyroscopes are arranged to spin in opposite directions and react on angular velocity of rolling by opposite tilts about their trunnion axes transmitting to the lever 192 a rotation-about a center 191 located bependulousness of the pendulum.

member 190 substantially as shown.

weights 222 and 223 permit of adjusting the tween the points 240and 241 where the links On the 238, 239 are connected to the lever 192. This lower part of the pendulum is fixed an arc modifies the number of linkages between the shaped member 190 made preferably of noncoils and the magnetic fluxes, Thus for exmagnetic and non-conducting material such ample when the link 238sis moved to the right as phenolic condensation material, fiber; and the link 239 to the left the lever 192 wood and the like. Two flat coils 195 and moves clockwiseand, the alternating electro- 196 shown alsov on Fig. 12, are fixed to th motive force induced in the coil 210 increases and that of the coil 211 decreases substan- Alternating magnetic fields indicated in tially in;.proportion to the amount of the Fig. 12 by projected areas 197, 198 are shown displacement and hence in proportion to the on Fig. 13 as produced by corresponding elecinstantaneous angular velocity of rolling. tromagnets excited by the .coils 224, 225 car- Instead of deriving the angular acceleraryi'ng alternating currents whose connections tion control from the angular velocity conare not shown. Theconnections of the coils trol as shown on Fig. 9, I can obtain it directto the outer circuit is produced by means of ly by means responsive to the angular inertia flexible conductors 226, 227 brought out near of an inertial system. The arrangement of the axis of oscillation of the pendulum so this type corresponding to the member 193 as not to impair its freedom about the axis with the associated coils 212,213 and magnets of oscillation. The pendulum 220 must be 206 and 207 shown on Fig. 12 is disclosed on placed preferably in the tranquil point of the Fig. 15. I ship as was mentioned in connection with Referring to Fig. 15, 250 represents the,

-1ievin g the pressure from the bearing and for rim of a "flywheel rotatably mounted in a ,bearing 194 about an axis parallel to the longitudinal axis of the ship. The frame 252 supports the wheel by means of a bracket 253 on which the ball bearing or other. pivotal member is mounted. For the purpose 'of rethe centrallization of the instrument as will be apparent I provide two springs 254, 255, supported by the upper part of the frame and fastened on their lower parts to two studs,

. 256 and 257 fastenedto the bar 193, which is keyed orsplined to the wheel 250. The tension of the springs 254 and 255 is so adjustedas to exert an upward pullon the wheel substantially equal to its weight which relieves the pressure from the bearing 194, thus reducing the friction to a minimum and rendering the manifestation of the inertia phenomena more distinct. Attached to the bar 193 are two coils 212 and 213, shown also on Fig. 12. as already described. The stops 260 and 261 are fixed to the frame 252, nor mally evenly spaced from the upstanding radial lug 263 mounted on the rim 250, and

form limiting abutments for the oscillation of the wheel and therefore of the bar 193.

.The dash pots 270 and 2'11 are fixed to the torque-of inertia which the springs apply to the wheel is equal to the moment of inertia of the'wheel times its angular acceleration, hence the extension of the springs from their middle position can be used as a measure of the latter and in view of the connections be-' tween the wheel and the coils is manifested electrically by variations of amplitudes of electromotive force induced in coils 212 and 213. as was previously explained.

The dash potspermit of elimination of any residual relative motion between the wheel and the train," and the limiting system fixes the performance at the desired point of mutual position between the coils and the electromagnets.

In Fig..1,'no mention was made 'as toflthe. nature of the 't'rack,lwhich may-within the scope of the invention", be rectilinear. but it is preferred to utilize a curvilinear track for-thev sakeof numerous advantages which will be 'pointed out.

In the first place for a steady rolling among waves the power consumption in case of a curvilinear track is considerably smaller. In fact in its extreme position the weight possesses a' certain amountzof potential energy due to the fact that it hasbeen-raised to a certain height on account of the curvature of the track, assuming of course that the residual quenched rolling is small enough.

The acceleration of the Weight during its downhill phase of motion in this case is due mainly to the gravity component along the tangent to the track. During the decel eration the uphill motion of-the weight on the track ofi'ers again an advantage of absorbing the kinetic energy in the form of potential energyavailable for the next swing in stead of absorbing it-by the brakes or similar irreversible devices.

. In addition to this advantage a curvilinear track offers a considerably greater safety than the rectilinear one. If the curvature of the track is adequately chosen, the weight even being quite free on the track does not offer any danger to the ship; this happens when the proper period of the weight on thetrack is smaller than the period of the ship. Under those conditions the weight will follow the rolling and the dangerous synchronous motion of the weight can never develo Among the various possible profiles of the track, it appears that. a cycloidal profile has definite advantages:

1. The cycloid has a comparatively small curvature at its "apex (where the motion of the weight is the fastest) and this curvature increases toward the end of the track.

2. The weight, if let free to roll on a fixed cycloidal track, represents a cycloidal pendulum having a remarkable property of isochronism (i. e. the period of theweight left free is independentof the amplitude) matching up a similar property of the ship within certain limits of rolling.

3. The period of a cycloidal pendulum'is where a is the rolling radius of the cycloid g is the acceleration of gravity.

For the above. reasons a cycloidal profile of the track is particularly well suited fora transverse shift of r the weight during the steady rolling among waves and only requires greater power when a transient wave condition is encountered.

The choice of the ratio g 'rolling radius of the profile B beam is of-importance. Clearly the limit of this ratio is when the complete cycloidal curvefits within the ships width. Such profile however correspond to a= 15 ft.

would betoo stifi and would require-too much power for the operation of the weight in transient conditions although in a steady state of stabilization amo ng waves this last mentionedcircumstance is of no special importance.

Fig. .16 shows a cycloidal profile generated by a rolling'radiuscorresponding to the ratio t; .12.

Thus for instance in case B -50 ft. this will Referring to Fig. 16, the rolling weight 1 is supported by the track 280, of the profile specified. The track is suitably supported on the frame of the vessel 281. The disclosed arrangement indicates that the driving power plant 282 is stationary in contrast with the movable power plant disclosed in Fig. 8, although either type may be used. The power plant comprises a motor 283, a brake 284, drum 285 on which is fastened the cable 286,

: ora plurality of such cables connected in parallel, with a suitable means equalizing the tensio between the cables, (not shown). The ciible ispassed around pulleys 287, 288,

. and idler pulley 289, and is secured to the weight 1, by means of suitable yielding connections (not shown). A buffer 290 is suit ably arranged at the endof the track. It is shown at but one end, but will be understood to be at both ends of the track. Weighted pulleys 291, 292 suitably supported from the ceiling of the compartment of the stabilizing .weight have for their purpose to take up any slack in the cables that may occur. Theidler pulley 289 has a coaxial pulley 294 of smaller radius, and the latter is in driving relation to a fixed pulley 295 through a cable 296. The fixed pulley 295 has a coaxial pulley 297 of small radius which latter is connected by cable 298, passing over pulleys 300 and 301,

to sliding member 199 shown in the lower; right hand corner of Fig. 12. The point of the double reduction of the linear displace- 'ment of the cable 286, by means of the pulleys and cables just described, is so that for a given displacement of the weight there is" a corresponding proportional displacement, on a reduced scale, of the member 199, within its supporting system 302, whereby the follow up action is produced in. the manner already describedf Y I The armature of the motor 285 is connected to the armature of the generator 116 so as to constitutea variable voltage drive in which the speed of the motor 285, displacing the Zveight, varies substantially in proportion to he voltage across the terminals of the generator 116, both inmagnitude and direction.

The structure of-thepreceding description made in connection with Figs. 12to '17 inclusive, affords substantially similar stabilizing control as that afforded by the other figures previously described. It possesses however means of mechanical elements such asepicyclic gear, lever system, shown on Fig. 1, andthe like, it combines these individual controlthe difference that instead of combining individual controlling actions into the resultant action controlling the stabilizing moment by ling actions electrically by superposition of electromotive forces of the same phase but varying amplitudes and impresses the result-, ant electromotive force thus produced inresponse to the instantaneous conditionsof angular motion on an electrical circuitcontrol ling thetorque producing plant in response to this resultant condition. An important practical feature of this last mentioned system lies inthat itispossible to incorporateall high precision instruments such as those shown onFigs. 13, 14, 15 and 17, which may be inherently delicate, into one unit of relatively small dimensions having no contacts or other weak points which might otherwise interfere with the reliability of its performance. This unit obviates the multiplicity'of amplifying units necessary with the system" disclosed ln'Figs. 1 to 11 inclusive, and affords easier adjustment of the performance. to meet any particular condition of sea. For i f instance referring to Fig. 13, the controlli'ngaction derived 'from the pendulum can be modified by sliding or displacing the electro magnets 197 and 198 perpendicularly to the plane of the paper by means of a 'set screw .(not shown), which modified the linkages with the flux for all positions of thependu :by a parabolic transient within a sufficiently small time interval. During this initial instantangular acceleration will develop in proportion to the instantaneousvalue of the disturbing torque and this will cause the displacement of the angular a'cceleration responsive member 193 in proportion to the magni* tude and direction of this acceleration. The electromotive force induced in the coil 2l2 will increase in View of the fact that this coil will be moved into the field 206. As a result of this acceleration angularyelocity, being time-integral of acceleration will develop in the course of time and the gyroscopes shown on Fig. 14 will incline the angular'velocity responsive element192, so that the coil 210 will be moved into the field 204 whereby the amplitude ofthe induced electromotive force Will be increased. As a result of angular moin Y tion: theinitial departure of the vessel from 1ts upright position will develop beng timei integral of angular velocity. Assume fur- I their symmetrical position shown on' Fig. 12.

.. magnetic cores of induot'an ces 170 and 173 I This initial moment will be characterized v a analytically by the condition 1 180 and will produce a corresponding large .plate current in this tube and also in coils 174 and 177 increasing the saturation in the and hence decreasing themagnitude of these 'inductances.

Opposite effects will occur in the coils 195,

p 211, 213 in which the-electro motive. forces will j .be reduced as a result of their being displaced from corresponding magnetic fields 198, 205, 207. The resultant voltage impressed 'on the gridof tube 181 will be'thus reduced as well as will the corresponding plate current of this tube which will reduce the ,magnetomotive forces of coils 17 5, 176 pro-' ducing magnetic saturation of the cores and willthus contribute to an increase of inductance of the inductive parts 171 and 172 of the bridges 167 and 168, which will be If thus unbalanced in opposite directions as far as the phase of the voltage mpressed on thetheicondition primaries 165 and 166 is concerned. The opposite variation of the time phase ofithe I voltage impressed on the grids of the rectifiers 154 and 155 from the secondary 163 on one hand and of'the corresponding voltage impressed on the grids of rectifier- 156, 157 from the secondary 164 on .the other hand produces opposite variation of the average rectified currents flowing from rectifiers 154, 155 and 156, 157 respectively. As is known this variation of outputs 'flowing through middle points of the secondaries 152 and 153 through the fields 161, 162 of generator 116.is

in general a certain function of the phase displacement of the-bridgevoltages impressed n the primaries 165 and ,166 respectively, and by a suitable design can be made sub- 5 stantially' proportional to this phase displacement. But the latter can be also made substantially proportional to the resultant ampli- .function of a substantially linear function of' thetype: I

a do (Z 0 rnB+nZ +P where the coefficients m, n, p depend on the parameters of the individual circuits con trolled by the pendulum shown on Fig. 13, by the angular velocity responsive instrument shown on Fig. 14, and by the angular acceleration responsive-instrument shown on Fig. 15 respectively.

Thus initially a substantially high voltage generated in generator116 Will start the moving weight with a comparatively high acceleration characterizing thusthe beginning of a very energetic meeting action employing the expression used in steering practice. This intense initial action willbe reducedin the course of'time for two reasons:

First on account of the follow up member 199 actuated from the displacement of the weight as was explained in connection with Fig. 17 in such manner that the initial cause i. e.displacement of the'-coils195,210, 212 acquiring greater linkages" with the corresponding fields will cause, through the instrumentality of the weights displacement a corresponding removal of the voltage impressed on the grid of tube 180 will be somewhat reduced;

Secondly on account of the energetic initial displacement of the Weight to port the angular acceleration to starboard maybe not only reduced but completely checked although the angular velocity may still continue in its former direction, i. e. to starboard.

This phase of motion is characterized by which indicates the beginning of the easing off action as far as the accelerational control is concerned. A moment later the condition s angular velocity responsive element 192 is symmetrical with respect to the poles 204, 205

which still further reduces the voltage impressed on the grid of the tube 180 as com pared to the meeting phase'of itsaction and by. operative association of bridges 167, 168

and rectifiers 154, 155, 156, 157 still more.

reduces the initial unbalance of the generator field and thus contributes to a still further decrease of motion of the weight to port. .The easing off-period is very strong at this point. It is apparent that opposite phases of control occur in the coils 196, 211,213, 201 and the tube 181 controlled by thevoltages induced in these coils.

At a still later instant the dynamical condition' will be I The ship reaches the verticality at this instant but the weight has been already displaced considerably to port by angular velocity and accelerational controls which have been already reversed in earlier phases of the motion as studied here.

In case the ship rolls among regular waves the stationary condition as is known is characterized by 180 difference in phase between the angle and the acceleration controlling ac-- tion, while the phase of the velocity controlling action is at to them both.

Strictly harmonic conditions never exist at sea where complicated transients due to the irregularity of the waves encountered (vairiable periods, variable lengths, .irregular shapes) account fora somewhat erratic and, generally, not strictly periodic rolling. From the preceding it follows that the above analyzed conditions of stabilization hold in any case as long as functions under study are continuous, which clearly is always the case. Furthermore the disclosed arrangement owing to its continuity permits in addition to the above mentioned anticipatory features, to keep a close equilibrium between the cause i. e. disturbing wave slope) andthe eflfect 'i. e thestabillzing moment) continuously throughout the motion, whether harmonic or not, whereby for the given roll quenching action a minimum weight is required as compared to devices of the prior art in which discontinuous controlling means, such as contacts, contactors and the like, were proposed.

For example, in case of the vessel of 10,000 tons having metacentric height about 2 feet, period of free oscillation 16 seconds and placed in a seaway of the maximum effective wave slope of 3, the maximum variation of the, disturbing'moment per second is about 350,000 ft. lbs. A contact'or a similar dis- I continuous controlling arrangement which operates from time to time, say every few secabove specified, by a very considerable amount especially when irregular conditions are met whence a comparatlvely poor efficiency of such devices in comparison with the above described method based on the principle of a continuous anticipatory action.

Although I have shown controlling means responsive to the first and second time deriva tives of angular motion, it will be clear that' still higher time derivative responsive means can easily be incorporated in the circuits controlling the grids of the tubes 180 and 181, as is apparent from the disclosure of Fig. 12.- As regards attainment of still higher time derivatives it can be readily seen that, for example, a third time derivative responsive means can be produced from the second time derlvatlve responsibe means, in a substantially similar manner in which the second time derivative responsive means is produced from the first, as shown on Fig. 9,

and this procedure can be continued still further.

In addition to the features disclosed the cir-.

cuits between the filaments and grids of tubes 180, 181 shown on Fig. 12- may have additional functions such as limitingaction by means of additional coils not shown operated from limit stops whereby a limiting'action -sim1lar to that produced by the lever 23 on Fig. 1 can be produced electrically.

The preceding description relates to continuously acting controlling means adequate to neutralize the disturbing moment of the waves or other mechanical disturbance which acts also in a continuous manner. In this manner the disturbance is neutralized at any moment. However, in certain cases for the sake'of simplification some component parts of the control may be arranged to function in a rather discontinuous manner without any departure from the spirit and scope of this invention. The regulation thus produced is generally represented in time by a rectangularcurve instead of a continuous curve (e. g. of a sinusoidal shape). It is known, however,

that any periodical discontinuous curve can. be developed Into Fourrier series of which- (angle, angular velocity, angular accelera tion of rolling) which are continuous, it is my mtent on to cover also the discontinuous con-

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