US3559610A - Antiroll facilities - Google Patents

Antiroll facilities Download PDF

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US3559610A
US3559610A US787871A US3559610DA US3559610A US 3559610 A US3559610 A US 3559610A US 787871 A US787871 A US 787871A US 3559610D A US3559610D A US 3559610DA US 3559610 A US3559610 A US 3559610A
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craft
voltage
combination defined
circuit
relay
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Albert Viollet
Edmond Voillaume
Francois Bouilhol
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Association des Ouvriers en Instruments de Precision
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Association des Ouvriers en Instruments de Precision
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
    • G05D1/08—Control of attitude, i.e. control of roll, pitch, or yaw
    • G05D1/0875—Control of attitude, i.e. control of roll, pitch, or yaw specially adapted to water vehicles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B39/00—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude
    • B63B39/02—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude to decrease vessel movements by displacement of masses
    • B63B39/03—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude to decrease vessel movements by displacement of masses by transferring liquids

Definitions

  • Ross ABSTRACT A weighted rod and a coacting contact carrier frictionally entrainable by a mounting on a rolling craft generate timing signals in positions of maximum lateral excursions of craft with reference to a longitudinal axis, the rod being pivotally mounted'aboard the craft on a shaft parallel to that axis so as substantially to maintain a vertical reference position whereby two sets of contacts on these relatively movable members are alternately closed during respective half-cycles of the rolling motion.
  • the timing signals control the operation of an antiroll system, specifically two stabilizer tanks on opposite sides of the craft which are alternately filled with and drained of water and which are supplemented by a further pair of tanks whose relative water volume is altered to balance deviations of the mean attitude of the craft from an upright position as likewise determined from these timing signals.
  • Antiroll devices comprise means which produce torques opposing the roll of seagoing ships and other craft and which are controlled so that the stabilizing action anticipates the roll movement. Accordingly, the control is usually effected by appropriate means responsive to the angle of tilt of the ship, the rate of change of such angle and possibly the acceleration of the variation and the differential thereof.
  • the counter-torqueproducing means can be dynamici.e., act in accordance with the ships speed of travel-and in such cases are usually ailerons which project from either side of the craft.
  • the ailerons can be permanently extended in rough weather and adjusted by variation of their inclination or pitch angle, or they can have a fixed orientation but be retracted or extended to a variable degree; ailerons are also known whose effective length and orientation are fixed but which are brought out for varying periods of time.
  • Such stabilizing means can also be static, i.e. based on the weight of shiftable masses. It has already been suggested that moving masses of liquid be used for this purpose, to which end vessels are disposed along the edges of the ship symmetrically with reference to its axis; a mass of water is then transferred from a vessel or tank on one edge to a tank on the other edge at appropriate times.
  • the disadvantage of this solution is that the water-transfer operations require very large energies. To obviate this disadvantage, it has been suggested that the tanks be disposed below the water line and that external water he allowed to enter the tanks and be expelled therefrom in the rhythm of the rolling notions to be counteracted.
  • the tanks can be filled just by hydrostatic pressure with an increase of delivery if the filling orifices are appropriately oriented, and the power required is merely that necessary for emptying the tanks with the aid of compressed air.
  • Such stabilizers have a considerably larger time constant than systems operating with extendable and/or orientable ailerons or fins.
  • Rolling can be considered a combination of two phenomena resulting in a composite oscillatory motion: a natural oscillation of the craft about its longitudinal axis, with a periodicity which is fairly constant although dependent upon the loading of the ship and the swell of the sea, and a forced oscillation caused solely by the swell and superimposed upon the natural oscillation of the ship with, usually, a much longer periodicity.
  • Theoretical studies of these movements show that an antiroll device can be controlled in response to data relating to oscillations immediately preceding the oscillations to be damped, such as the times of occurrence of the peaks, the length of a half-period, the roll amplitude and the mean position of the ship.
  • the general object of our present invention is to provide means for obtaining some or all of these various data and using them to control antiroll stabilizers. More particularly, our invention aims at providing means for forecasting the rolling movement to be stabilized from the motion, during the immediately preceding complete roll cycle, of a vertical reference standard aboard the craft.
  • our invention provides a reference member of substantially fixed absolute orientation maintained by gravity or inertia, a cooperating member mounted on the craft for lateral angular entrainment, and coacting circuit means on these members for actuating a stabilizer-control system in timed relationship with therelative movement of the members.
  • a rocking member or plummet swivelable around at least one longitudinal axis relatively to the ship while maintaining a substantially vertical position is associated with a balanced unit movable around an axis coincident with the swivel axis of the rocking member, this unit bracketing the rocking member with play and comprising on each side thereof a contact member operated by the interengagement of the rocking member and the mobile unit.
  • a switchover of contacts carried by the coacting elements so that a control signal is generated to indicate the time of occurrence of such peak.
  • such a rocking member supports at least one slider movable along a track of a DC -energized potentiometer connected with the ship, the voltage thus taken from the potentiometer in certain positions being stored to furnish an analogue output representing one of the parameters of the oscillating movement. Consequently, a comparison of the extreme voltages obtained in the rocking movement enables their mean value to be ascertained, as a measure of the mean attitude or angle of heel of the ship, as well as their difference which is a function of roll amplitude.
  • roll compensation is produced by two independent torque generators respectively responsive to the natural roll of the ship and to the oscillation superimposed thereupon, only the torque generator counteracting the natural roll of the ship being controlled in dependence upon roll amplitude whereas the other torque generator is controlled only in dependence upon the mean position of the ship between two consecutive opposite peaks of the oscillation.
  • FIG. I is a diagrammatic plan view of antiroll damping equipment comprising tanks communicating with a body of liquid surrounding a craft;
  • FIG. 2 is a cross section on the line II-II of FIG. 1;
  • FIG. 3 is a cross section on the line III-III of FIG. 2;
  • FIG. 4 is a view in diagrammatic cross section of a ship having aileron-type antiroll equipment
  • FIG. 5 is a side view on the line V-V of FIG. 4;
  • FIG. 6 is a diagram showing the operating conditions of a tank-type stabilizer as illustrated in FIGS. 1-3;
  • FIG. 7 is a block-schematic view of a system for controlling a tank-type stabilizer of the kind shown in FIGS. 1-3;
  • FIG. 8 is a partly diagrammatic side elevation of a device for providing a vertical reference standard and of associated electrical circuitry
  • FIG. 9 is a side view on the line IX-IX of FIG. 8;
  • FIG. 10 is a diagrammatic view of the device shown in FIGS. 8 and 9, along with its electrical circuit connections;
  • FIG. 11 shows a circuit diagram for evaluating the data obtained from the assembly of FIGS. 8-10;
  • FIG. 12 is a graph showing variations in the operating time of a torque compensator plotted against the amplitude of the roll to be compensated
  • FIG. 13 is a circuit diagram, more detailed than FIG. 7, of a control system for a tank-type stabilizer as a shown in FIGS. 1-
  • FIG. 14 is a diagram showing how the system of FIG. 13 operates in dependence upon the real amplitude of the roll to be corrected;
  • FIG. 15 is a diagram of an installation for correcting the mean angle of heel of a ship
  • FIG. 16 is a diagram of a balanced amplifier for the circuit of FIG. 11;
  • FIG. 17 is a simplified alternative form of circuit diagram for providing a control signal after a quarter-period of the natural roll
  • FIG. 18 is a diagram serving to explain the operation of the system shown in FIG. 17.
  • FIGS. 19 and 20 are diagrams serving to explain the use of aileron-type torque correctors for counteracting rolling motion.
  • FIGS. 1-5 show conventional antiroll devices 111 which the invention may be of use.
  • a ship 1 shown in FIGS. 1-3 has tanks 2,, and 2, disposed along its port and starboard sides, the subscripts B and T standing for the French designations bsourced (port) and tribord (starboard).
  • Each tank is formed with two orifices 3, 4, the orifice 3 being open toward the front and the orifice 4 being open toward the rear of the craft. Since all these orifices are disposed below sea level 5, the tanks can be filled through the orifices 3 by both hydrostatic and dynamic pressure; when the ship is moving, emptying of the tanks is assisted by the dynamic negative pressure produced in the rear of the orifices
  • the tanks can be filled by venting their interior to atmosphere via conduits 6 and valves 7.
  • the tanks are emptied by means of compressed air supplied from a reservoir 8 by a pump 9; valves 10, ll, controllable by suitable servomechanisms, also intervene in the filling and draining of the tanks.
  • the ship has two pairs of tanks, which can be operated simultaneously, on each side. As shown hereinafter, each individual tank of these identical pairs may advantageously be controlled independently.
  • actuators 12 can extend ailerons or fins 13 of hydrofoil profile from opposite sides of the craft; with proper angular orientation, these fins can provide uplift or downthrust compensating for the rolling motion and varying as a function of the forward speed of the craft.
  • the pitch of these fins and/or their effective length L, i.e. the degree of their projection from the sides of the craft, may be controlled by conventional means.
  • Systems using stabilizing masses are operative whether the ship is stationary or moving (being more effective when the ship is in motion than when it is not), but ailerontype stabilizers are operative only when the ship is moving.
  • FIGS. 7-16 we shall, for convenience, limit our to a discussion of tank-type antiroll stabilizers of the kind shown in FIGS. 1-3 whose damping effect depends upon the state of tank filling, thus upon a continuously varying quantity, so that an appreciable time factor intervenes in the antiroll action, in contradistinction to the almost instantaneous compensating effect of fin-type stabilizers.
  • a sinusoidal line 14 can therefore represent the simple or natural roll having, as an undamped oscillation, a natural period T,,.
  • the corresponding side (here the port side) of the ship must be weighted to limit the restoring or straightening torque and thus to attenuate the oscillation.
  • the ship passes through its normal position before tilting to the other side at an angular velocity which is then at its maximum, it must be lightened to reduce the mass actually performing the oscillating movement. To achieve maximum damping, therefore, the tanks must be filled when the ship reaches its greatest angle of heel, whereupon the rising tanks just filled should be drained as soon as the mean position is reached.
  • the tanks on each side can start receiving liquid at the time when the angle of heel to such side is a maximum lateral excursion. Since the filling rate is considered constant, a straight line 15, can represent filling. The voiding of the same tank can start at a time t near the point T,,/4 corresponding to the passage of the sinusoidal line 14 through zero, with a straight line 16, representing drainage.
  • the volume of water used in this case for stabilization corresponds to the triangle bounded by the abscissas I and the straight lines 15,, 16, which represent the stabilizing torque on a convenient scale.
  • this correction may sometimes be excessive and, if the roll is of low amplitude, may make the ship oscillate.
  • the refilling must start at an instant, such as t,, after the time of maximum angle of heel, with'voidance still commencing at a time t near T,,/4.
  • the roll compensation provided on each side then corresponds to the hatched triangles whose sides 15,, 16 are parallel to the maximum-correction sides 15,, 16,.
  • FIG. 12 illustrates this variation of damping in graph fonn.
  • the tanks have more effect when the ship is moving than whenit is not. If the start of tank filling at maximum tilt on either side produces a damping a,, when the ship is stationary and B, when the ship is moving (the angle a, being being 2' and the angle [3,, being 3" by way of example), the damping factor AM is zero when the instant t, of incipient refill, occurring at time 116/4, coincides with the instant t of incipient voiding. It will be assumed, in close approximation to the actual facts, that a shift of the time t, between the antinodal and nodal points 0 and T,,/4 causes a variation of the damping factor AM as represented by the straight line D,.. This linear variation of damping in dependence upon t, (delay in the start of filling relative to peak time 0) is significant for the interpretation of the graph of FIG. 14 discussed hereinafter.
  • the periodically recurring corrective action of the antiroll system is out of phase with the oscillation 0 to be compensated, a factor which modifies the period of such oscillation.
  • the true oscillation period will be designated hereinafter by the reference character T.
  • rolling is a composite movement resulting from a combination of the natural roll of the ship sustained by external forces, with a superposed sway produced by the swell.
  • this complex movement is considered as a simple oscillation whose mean line is not the axis I but a curve 17 (representing an oscillatory phenomenon of amplitude 0, determined graphically by the sequence of mean ship positions relative to the horizontal (or the vertical) between two consecutive swings in opposite lateral directions.
  • Full roll correction therefore comprises at any time a correction of the ship's side-to-side movement and a correction of the ships mean position, i.e. a rebalancing relative to its longitudinal axis, so as to oppose the slow movements tending to tilt the ship to one side or the other.
  • This latter correction can be achieved by varying the state of filling of a pair of balancing tanks (28,, 2T in FIG. 7) under the control of a signal representing the mean attitude of the ship between two extreme positions on opposite sides.
  • Correction of side-to-side movement of the ship depends for each side upon a determination of the instants t, and t, which are in turn dependent upon the times t 0 when the roll reaches its maximum excursion alternately on each side, upon the half-amplitude 0,, of the roll which determines the required degree of damping and therefore the delay between the instants t, and antinodal points 0, and upon the mean tilt angle 7 0,, of the ship compared with its actual list 0 to determine the time t,, thus obviating the need for direct determination of the duration of each quarter-period after passage through the peak.
  • the installation can be realized as schematically shown in FIG. 7.
  • an electromechanical unit MI which signals the instants t marking the antinodal points for port and starboard, along with signals 0,, 0,, and 0,, 6,, and 0, which are passed to two controllers CaB (for port) and C,,T (for starboard) sharing a common section CV.
  • controllers determine the starting times t,.(B) and t,(T) for the filling of the corresponding tanks 28, and 21, by the energization of the respective electromagnetic valves EB and ET, while the common control circuit CV determines the starting time t, for the subsequent emptying by breaking the valve-energizing circuit so that the compressed air can expel the water from the tanks.
  • the signal 0 an analogue of the mean angle of the ship relative to the vertical, also goes to a regulator AS receiving feedback infonnation on the liquid levels in the tanks 28, and 2T whose state of filling is controlled by this regulator through respective electromagnetic valves F8 and F1.
  • the two main tanks 2B,, 2T are full.
  • the maximum restoring torque in either sense is of course produced by emptying a single main tank, i.e. the one on the side where weighthas to be reduced.
  • a similar variation restoring torque can be produced either by emptying some liquid from one of the two supplemental tanks 2B,, 2T or by introducing an equivalent quantity of liquid into the other supplemental tank.
  • FIG. shows a circuit arrangement for the regulator AS.
  • a voltage e which is an analogue of 0,, (obtained in a manner described hereinafter), is zero when the mean position of the ship is horizontal, positive for a mean angle of heel to one side, and negative for an opposite mean tilt; this voltage is fed to two windings 81 n and 81 of two polarized relays whose arma tures 82B, 82T control via intermediate relays (not shown) the electromagnetic valves FE and FT, respectively; the two armatures could also be replaced by a single contact arm.
  • windings 81 81 are supplied with voltages tapped from respective potentiometers 83,, 83 by sliders 85,, 85 under the control of level-indicating floats 84,, 84,4 in tanks 28,, 2T respectively.
  • the reference voltage is therefore zero for both tanks when the same are full; the potentiometer 83, delivers a positive voltage which increases in proportion to the drainage of tank 28,, whereas potentiometer 83 under the same condition delivers an increasing negative voltage. Consequently, if the mean angle of heel is e.g. to starboard (e negative), tank 2T continues to drain as long as the absolute value of e exceeds that of the voltage on the slider 85,, but fills in the opposite case.
  • FlGS. 8-11 show the assembly VR Ml, i.e. the means for obtaining the data t,,, 0,, 0,, and 0.
  • the vertical reference direction can be provided by a gyroscope or more simply by a pendulum or plummet 18 oscillating around a shaft 19 with negligible friction, shaft 19 being borne by the ship and extending parallel to the longitudinal axis thereof.
  • the shaft 19 can be mounted in a collar 19' journaled on a shaft 19" extending transversely of the ship.
  • a mobile unit 20 rotatable with low friction in a bearing 21 rigidly secured to the mounting 112 for the shaft 19" and centered on the pivotal axis of pendulum 18; the unit 20 is oscillations of the craft, ferrule abuts either of the points 21,, 21, and remains in contact therewith to its position of maximum tilt.
  • the ferrule 23 withdraws from the engaged contact and abuts the other one. Consequently, upon each reversal one contact opens, with closure of the other contact after a time interval which can be adjusted by means of the screw 22.
  • the times t, of maximum port and starboard tilt can be determined by means of the set of contacts 23, 21,, 21,.
  • the potentiometer tracks 30, 31 furnish analogue voltages for the values of 0,, Le. the half-amplitude of the lateral oscillation of the ship, and of 9 i.e. the position balanced around its axis and is provided, on opposite sides of the pendulum rod 18, with contact points 21,, 21, whose spacing can be adjusted by means of a screw 22 spreading their resiliently biased supporting arms.
  • the contacts 21,, 21 are adapted to cooperate with a conductive ferrule 23, mounted on the pendulum rod, energizable via a conductor 24 connected to the shaft 19.
  • the circuit is therefore closed externally either via a conductor 25, connected to contact 21, or via a cbnductor 25 connected to contact 21,.
  • Rod 18 also carries ferrules 26, 27 which are connected to conductors 28, 29 and respectively slide along potentiometer tracks 30, 31 of resistance material rigid with frame 119.
  • the ends of the arcuate tracks 30, 31 are respectively connected to ground potential (0) and to a fixed operating potential A, the polarity of the voltage drop being opposite for the two tracks.
  • the mean value e of the potentials will be
  • the mean position 0, can therefore be represented by an mean potential is analogue voltage V 0, d corresponding to the input voltage e, of FIG. 15.
  • FIG. 11 shows the basic design of the memory used to store maximum-swing potentials and to deduce the mean of the data thus stored.
  • the potentials, e. g. a and b, to be stored are transmitted via respective amplifiers Am to contacts k k from the corresponding slider 26 and/or 27 of FIG. 10.
  • the windings of relays K and K are connected, in circuits of short time constant (compared with period T or T to two normally charged capacitors G H and 6,.
  • respective contacts m m are closed, in a manner described hereinafter, under the control of the contacts 21,, 21 to complete respective discharge paths.
  • the windings K K are therefore very briefly energized at the appropriate time so that the short closure of their contacts k k alternately charges two identical capacitors H H, to the assigned potentials.
  • the latter capacitors are serially interconnected by a pair of equal resistances r,,.
  • the amplifiers A shown in FIG. 11 may be of the balanced type as shown in FIG. 16.
  • a voltage u of low value which can be either positive or negative, is applied in parallel to two transistors 87, 88 which are similar to each other, except that transistor 87 is of the NPN type and transistor 88 is of the PNP type, and which are connected as emitter followers (with col lectors at fixed potentials) by way of two resistors 89, 90 connected to zero potential.
  • One or the other of the transistors conducts according to the polarity of the input voltage 14 is also present, without amplification but developed across a low impedance, at the common output terminal 91 of the transistors.
  • these circuit arrangements are to establish a precise instant voltage measurement, the connection between the two symmetrical resistances is not permanent but is completed only momentarily to determine such instant (see FIG. 13); also, in order that the voltages collected by the storage capacitors may be independent of previous charges received thereby, the capacitors are periodically discharged before being recharged to the new voltage to be stored.
  • These circuit arrangements also use amplifiers A,, for charging the storage capacitors.
  • the voltage e (which is alternately positive and negative) departs further from zero than does the voltage e
  • the circuit arrangement Am operates satisfactorily as long as the ratio of its input and output voltages is linear at least for low values of e,,, since in the case of higher voltages e, i.e., large oscillations of the ship the system operates continuously with maximum effect and exact correspondence between input and output voltages becomes unimportant.
  • the circuit arrangement shown in FIG. 13 uses the basic systems hereinbefore described to obtain voltage analogues for 0, 0,, (for both port and starboard), and for determining the times t,(B), t,(T) and t,.
  • all relay contacts are shown in the unoperated position.
  • Connected to contacts 2 1 and 21 are the windings of respective relays M,,, M, which are therefore energized alternately, each substantially for half an oscillation period between two maximum excursions, and are then deenergized for the remainder of the cycle.
  • Each of the these relays comprises a reversing armature 35 35, and a circuit-closing armature 36,,, 36
  • Each reversing armature by changing over from its back contact m, or m to its front contact m or m,,, enables the capacitor G or G to charge through one of two like resistances r; for subsequent discharge via the relay windings K and K respectively.
  • Each armature 36 36 completes, by way of a respective front contact m or m a circuit for supplying a negative energizing voltage to the controllers C,,B and C,,T. These circuits are closed by armatures D, and P of respective relays P, and P, which are alternately energized by a reversing armature 37 of a polarized relay 39 in control circuit CV, this armature 37 moving toward one or the other of two bank contacts 38,, 38 depending upon the direction of current flow through its winding. The mode of energization of this winding will be described later.
  • the relays K, and K each comprise, in addition to their respective armatures k and k (see FIG. 11), two other armatures k k and k k respectively, through which the voltage a can be stored in respective capacitors C8,, CT and thevoltage b can be stored in respective capacitors CB CT
  • the capacitors CB CB associated with the port controller caB cooperate with a pair of equal resistances r to form a voltage divider similar to the one shown in FIG. 11.
  • a pair of equal resistances r to form a voltage divider similar to the one shown in FIG. 11.
  • the two resistors r instead of being permanently tied together, are intermittently interoonnectable by way of an armature m, of relay M cooperating with bank contacts 101 and leading to controller C B.
  • a similar circuit arrangement is operative in the case of the capacitors CT CT and an armature m of relay M engageable with bank contacts 102 and connected to controller C T. Via the controllers C,,B and C,,T, therefore, a voltage V0 which is an analogue of the maximum oscillation amplitude can be transmitted to port and starboard, respectively.
  • each controller C,,B and C,,T the input voltage V0, goes to the base of a current-amplifying transistor T in the case of the controller C,,T which is connected asan emitter follower in series with two load resistances r,,, r, controlled by a selector'switch 40 whereby one of the two voltages appearing at bank contacts 40a and 40b can be fed to a voltage divider formed by two equal and series-connected resistances r,. Consequently, the voltage at the junction 43 of the two resistances r, is the mean of the voltage picked up by selector 40 and the voltage at a point 41 representing one terminal of a capacitor C the other terminal thereof being at ground (positive) potential.
  • the voltage at point 43 is transmitted to the base 44 of a transistor Tb whose state of conductivity controls the solenoid valve ET (FIG. 7) which, as previously explained, vents tank 23, to atmosphere when energized by a pulse at time t,(T).
  • the solenoid valve ET (FIG. 7) which, as previously explained, vents tank 23, to atmosphere when energized by a pulse at time t,(T).
  • the voltage on its base 44 must reach a threshold VE (FIG. 14).
  • Identical circuitry in controller C,,B generates an output pulse at time t,(B) to energize the solenoid valve EB of FIG. 7.
  • Capacitor C is charged through an adjustable resistor r, by negative voltage transmitted via contacts P 36 the latter closing shortly after the time of maximum excursion of the oscillation on the particular side here concerned.
  • timing condenser C i.e., the voltage at point 4lcan be represented as a function of time by a straight line 42 (FIG. 14) if the start of the exponential charging of a capacitor is considered substantially linear.
  • a Zener diode 47 accurately determines the charging voltage for such capacitor so that the potential difference thereacross varies in a manner closely corresponding to the straight line 42.
  • the switch 40 can select either a voltage V 6, on terminal 401 or a voltage V 0, on terminal 40b (see FIG. 14), both of which are analogues of 0,, and, therefore, of roll amplitude; voltage V,0,, can be used when the ship is stationary and voltage V 6, can be used when the ship is moving; since, as has been seen, the moving-craft damping effect [3,, exceeds the stationary-craft damping effect 01,, a lower analogue value can be used when the ship is moving.
  • This voltage selection is not critical, however, for if selector 40 is kept on contact 40b when the ship is stationary, all
  • V 61, and V 6 are exactly equal to 2VE for the roll amplitudes on standstill and in motion respectively corresponding to the maximum damping effect a, or ,6, of the stabilizing tanks.
  • the sloping line 50 in FIG. 14 represents the voltage drop across resistors r; in the limiting case where V 0, or V 0 equals 2VE. Consequently, when half the roll amplitude is greater than the damping angle, the voltage V at point 40 is greater than 2VE and, since the condenser voltage VC is zero at point 41 when maximum list to port is reached, the voltage V at point 43 and therefore on the base 44 of transistor Tb is greater than the threshold voltage VE.
  • Tank filling is therefore initiated at an instant close to the time t,,(B), thus at the desired moment as explained with reference to FIG. 12. If, however, half the roll amplitude is less than the clamping angle so that the amplitude-analogue voltage V at point 40 attains, say, only a value V,, at the time t,,(B), the voltage V at junction 43 will have only the value indicated by the point 51, less than VE. Only when the voltage VC of capacitor C, has reached the charging potential U,,,, as shown by a sloping line 52, will the voltage VE be attained at point 43. Filling will therefore start at a time t,,,, subsequent to the time t,,(B), the separation between these two instants increasing progressively with decreasing roll amplitude.
  • the comparison circuit CV determines start-of-emptying times by interrupting the energization of these controllers at a time when the ship is passing through its mean position
  • the analogue voltage V0, developed at e (FIG. 13) and the analogue voltage V0 picked up by the slider 26 are fed to the bases of respective transistors T,, T which are connected as emitter followers, with their emitters interconnected by way of the winding of polarized relay 39; two symmetrical networks 55, which comprise Zener and ordinary diodes and which shunt the winding of relay 39, limit the voltages applied thereto and absorb switching transients.
  • controller C,,T When the analogue voltage of angle 9 in this balanced arrangement is greater than the analogue voltage of angle 0 the armature 37 engages the contact 38
  • the list is then to starboard in relation to the mean position of the ship, and controller C,,T is energized via contacts P and 36,.
  • Controller C,,T is deenergizedi.e., the starboard tank starts to emptyas soon as the analogue voltage of 0 has decreased below its stored mean-position value, thus when the base potential of transistor T has dropped below the base potential of transistor T, and the current flow through the winding of relay 39 is reversed so that armature 37 engages the contact 38,.
  • the refilling time t is determined in either of the controllers whenever a simultaneous closure of contacts P 36 or P 36, indicates that the maximum roll excursion to one side is greater than the stored mean angle of heel (0, If this is exceptionally not the case, the antiroll system does not operate.
  • the time t corresponds to the start of filling of the tank on the corresponding side, such filling ceasing upon the start of emptying at the time t determined by the movement of the armature 37.
  • the oscillation period T may vary, e.g. because of ship loading or of the swell, but this does not impede the operation of the system. which adapts itself to the new period, for the state of charge of the storage condensers decreases substantially linearly in time so that the analogue of swing angle 0,, for each side varies with time as indicated by the sloping lines 60, 61, 62 in F IG. 14.
  • the longest period T /4 for which the system can operate is determined by a sloping line 64 and its horizontal extension 65 intersecting the charging curve 42. If the period decreases to a value T T,, the voltage given by the intersection of threshold line 60 with an ordinate V 6 corresponds to the same minimum roll angle. However, an analogue voltage V,,, for a given roll angle, represented by line 61, changes to a higher voltage V',, for the same angle upon a decrease of the period from T to T. As shown by a sloping line 66, the startof-filling time advances concurrently from t to t',,,,. Thus, any reduction in the length of the oscillatory period is compensated by a more rapid response of the roll stabilizer.
  • the simplified system shown in FIG. 17 is designed for cases where it is not necessary to determine the ships mean position between two consecutive extreme angles of heel, its stabilizer including but one pair of tanks operating only on heavy rolling.
  • a relay winding M associated with one of the two sides of the ship (its symmetrical counterpart not being illustrated) is controlled as before by one of the contacts (21,) of the rocking assembly 18, 20 and operates a reversing armature 68 forming part of the controller for the particular side concerned; when in its solid-line position, armature 68 enables a capacitor 69 to be charged by a stabilized voltage V.
  • the capacitor circuit is closed via a tap on a voltage divider 71, 72.
  • capacitor 69 discharges into a circuit comprising, in parallel, a relay winding 73 and a resistance 74.
  • the relay winding controls, as in the preceding embodiment, the energization of the solenoid valve controlling tank filling (or the operation of equivalent antiroll means) corresponding to the particular side concerned; also, the relay 73, 79 is so designed that a drop in the voltage across its winding 73i.e. across capacitor 69below a critical value V (FIG. 18) releases the armature 79.
  • the slope 75a (FIG. 18) at the start of the charging curve for capacitor 69 is half the absolute value of the opposite slope 76a of its discharging curve 76. Consequently, since each of the contacts 21,, 21 stays closed for substantially the time T/2, charging stops after that time at the point 77 and discharging restores the voltage across the relay winding to the value V during the next time interval T/4, whereupon the voltage V is maintained across capacitor 69 by a diode in parallel therewith.
  • the relay circuit of FIG. 17 including condenser 69 acts as a delay network translating a closure of contact 21, during the interval 0 I/4 into a closure of contacts 79 in the interval T/2 3T/4.
  • This delay of corrective action by about half a cycle, measured from the timing signal given by the opening or closure of contacts 21,, 21 is the same as that between the charging of the storage condensers in FIG. 13 and the utilization of the stored charge by controllers C 8 and C T.
  • FIG. 19 relates to a case in which the stabilizing means is an aileron having either a variable inclination (e.g. pitch angle) I or a fixed inclination and a variable effective length L (FIG. 4) transverse to the craft.
  • the roll is represented as a damped sinusoidal line 78, the assumption being that the antiroll means becomes effective when the swing already has reached certain minimum amplitude.
  • the aileron-extension signal can be generated at times t,,(B) and t,,(T), under the control of the units 18 and 20, whereas the inclination I or the effective length L can be under the control of the parameter V0,, representing the peak amplitude.
  • FIG. relates to the case of ailerons of invariable efficiency (constant inclination and effective length), the control parameter being the time t, for which the aileron is extended.
  • aileron-extension time t can coincide with a quarter-cycle of the oscillation; alternatively, for still greater effectiveness, the aileron can be made operative at a variable starting time t, determined by the respective controller C B or C T shown in FIG. 13. Maximum damping prevails of course when the aileron is always extended for halfa cycle, as in the case of FIG. 19.
  • control system can be limited to the relatively movable elements 18 and 20 determining, as the only controlling parameters, the consecutive instants t,,(B), t,,(T) which are established by the alternate operation of the contacts 21, and 21, and which mark the start and the end of successive half-periods.
  • a reference member aboard the craft in the form of a weighted rod suspended from a mounting with a pivotal axis parallel to said longitudinal axis;
  • circuit means on said members for generating timing signals during predetermined relative positions thereof coinciding with maximum lateral excursions of the craft with reference to said axis
  • said circuit means including a first set of normally open contacts on said rod and on one of said arms and a second set of normally open contacts on said rod and on the other of said arms, said sets of contacts being alternately closable in symmetrical relative positions of said arms and said rod, said an'ns being provided with frictional bearing means supporting same for swinging movement about a line parallel to said longitudinal axis, the friction of said bearing means being low enough to let either of said arms come to rest against said rod upon an incipient swing of the craft to a respective side whereby the corresponding set of contacts remains closed for substantially half a rolling cycle;
  • actuating means connected to said circuit means for periodically making said stabilizer means effective in response to said timing signals.
  • actuating means comprises a delay network for translating closure of either of said sets of contacts into corrective actuation of said stabilizer means substantially half a rolling cycle later.
  • said delay network includes first relay means connected to operate in response to closure of either of said sets of contacts, condenser means chargeable by said first relay means in the operated condition thereof, and second relay means connected for operation by a discharge current from said condenser means in the unoperated condition of said first relay means.
  • said delay network further includes a charging circuit for said condenser means and a discharge circuit for said condenser means said ca acitive means to said controller means.
  • T e combination defined m claim 5 wherein one of said members is provided with a generator of'variable voltage depending upon the heel angle of the craft with reference to the vertical, said capacitive means being connectable by said second relay means to said generator for varying said stored charge in accordance with said variable voltage, said condenser means having a discharge circuit through said second relay means with a time constant which is short compared with a rolling cycle.
  • said capacitive means comprises two pairs of identical capacitors and said generator includes two complementary voltage sources each connectable by said switch means to a respective capacitor of each pair at the end of a respective half-cycle, said controller means comprising two controllers for operating respective sections of said stabilizer means to correct listing to corresponding sides, each pair of capacitors being provided with a bridging voltage divider having two normally disconnected halves interconnectable by said switch means for transmission to a corresponding controller of the mean of the charges stored.
  • sections of said stabilizer means each comprise a main tank and an auxiliary tank, first valve means responsive to a corresponding controller for alternately filling and draining said main tank during part of a rolling cycle, and second valve means responsive to said analogue voltage for filling said auxiliary tank to an extent determined by said mean heel angle.
  • each of said controllers includes a timing condenser chargeable at a controlled rate in the presence of said activating signal and signaling means responsive to a predetermined relationship between the charge on said timing condenser and the mean charge of the associated pair of capacitors transmitted thereto by said switch means.
  • each controller further includes switchover means for modifying the' magnitude of said mean charge prior to comparison with the charge on said timing condenser.
  • said complementary voltage sources comprise a pair of arcuate potentiometer tracks rigid with the craft and a pair of contactors on said rod respectively sliding along said tracks.
  • said actuating means includes at least one amplifier with a pair of transistors of opposite conductivity types having emitters interconnected by a low-impedance circuit and having collectors connected to points of fixed potentials.

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  • Engineering & Computer Science (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Ocean & Marine Engineering (AREA)
  • Vibration Prevention Devices (AREA)
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US787871A 1967-12-29 1968-12-30 Antiroll facilities Expired - Lifetime US3559610A (en)

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FR134315 1967-12-29

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3928754A (en) * 1973-05-07 1975-12-23 Herman Allan Friedrich Edlund Device for calculating the resonant rolling period of a ship
US4694768A (en) * 1985-12-23 1987-09-22 Leonard Aloisio Emergency air system for partially submerged vessels
US5540170A (en) * 1994-08-17 1996-07-30 Purdy; Peter K. Multi-hull marine vessel with retractable outer hulls
US20140190901A1 (en) * 2011-02-16 2014-07-10 Arctia Shipping Oy Method to utilize a ship in a novel way and a multi-purpose ship
WO2018206653A1 (fr) * 2017-05-09 2018-11-15 Gremco Navire stabilisé par ballasts

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2338147A (en) * 1935-07-29 1944-01-04 Steinen Carl Von Den Stabilizing system for ships
US2618712A (en) * 1949-02-26 1952-11-18 Moledzky Sydney Contact switch for electrical contacts
US3265029A (en) * 1964-07-21 1966-08-09 Laurenti Alfred Ship stabilizer

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2338147A (en) * 1935-07-29 1944-01-04 Steinen Carl Von Den Stabilizing system for ships
US2618712A (en) * 1949-02-26 1952-11-18 Moledzky Sydney Contact switch for electrical contacts
US3265029A (en) * 1964-07-21 1966-08-09 Laurenti Alfred Ship stabilizer

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3928754A (en) * 1973-05-07 1975-12-23 Herman Allan Friedrich Edlund Device for calculating the resonant rolling period of a ship
US4694768A (en) * 1985-12-23 1987-09-22 Leonard Aloisio Emergency air system for partially submerged vessels
US5540170A (en) * 1994-08-17 1996-07-30 Purdy; Peter K. Multi-hull marine vessel with retractable outer hulls
US20140190901A1 (en) * 2011-02-16 2014-07-10 Arctia Shipping Oy Method to utilize a ship in a novel way and a multi-purpose ship
US9605398B2 (en) * 2011-02-16 2017-03-28 Arctia Shipping Oy Method to utilize a ship in a novel way and a multi-purpose ship
WO2018206653A1 (fr) * 2017-05-09 2018-11-15 Gremco Navire stabilisé par ballasts
FR3066175A1 (fr) * 2017-05-09 2018-11-16 Jean-Claude Chauveau Navire stabilise par ballasts

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Publication number Publication date
DE1815861A1 (de) 1969-07-17
FR1556388A (fr) 1969-02-07
GB1247195A (en) 1971-09-22

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