Патент USA US2406143код для вставки
Aug. 20, 1946'. s, GODET 2,406,143. FOLLOW-UP CONTROL SYSTEM Filed June 5, 1942 £7 ZZZ =%.? a 223 mil ~20“ ‘@773 v o \\\\ g440d \_ \ . “ii a?‘ I ?h‘E! o m1 J Inventor‘: Sidney Godet, H is Attorney. Patented Aug. 20, 1946 2,406,143 UNITED STATES PATENT OFFICE 2,406,143 FOLLOW-UP CONTROL SYSTEM Sidney Godet, Schenectady, N. Y., assignor to General Electric Company, a, corporation of New York Application June 5, 1942, Serial No. 445,949 3 Claims. 1 (Cl. 172-239) This invention relates to control systems, more 2 to be driven into positional agreement with a particularly to follow-up control systems for driv pilot device or director H by suitable driving ing an object into positional agreement with a means such, for example, as represented by the pilot device, and it has for an object the provision direct current motor [2 to the drive shaft of of a simple, reliable and improved control system which the object H1 is connected by means of of this character. suitable reduction gearing (not shown). Direct A further and more speci?c object of the in current is supplied to the armature of the motor vention is the provision of improved means for I2 by means of a special generator l3 having a preventing hunting or oscillation of the driven pair of short-circuited armature brushes l3a and object about the position of correspondence with 10 a'pair of load brushes | 3b to which the armature the pilot device. of the motor I2 is connected by means of con In carrying the invention into effect in one ductors M. The generator i3 is an armature re form thereof, means responsive to positional dis action excited dynamoelectric machine and is agreement of the pilot device and driven object driven at a speed, which is preferably substan are provided for producing a signal voltage cor responding to the error or positional disagree ment of the pilot device and driven object. This signal voltage is ampli?ed by suitable means such as an electric valve type ampli?er, and the ampli ?ed signal voltage is used to control the supply ~ of voltage to the follow-up motor so as to cause the motor to drive the object toward correspond ence with the pilot device. If the driven object possesses a substantial amount of inertia or if tially constant, by any suitable driving means, such, for example, as an induction motor 1 5. The axis of the magnetic ?ux which is produced by the short-circuited armature brushes I 3a is re ferred to as the short circuit axis, and the axis which is displaced 90 electrical degrees from the short circuit axis is referred ‘to as the control axis. The net ?ux along the control axis is pro duced by two opposing control ?eld windings 13c and l3d, a series compensating ?eld winding lite, the system is designed for a high degree of ac 25 and the armature reaction of the load current curacy of correspondence, violent hunting or itself. The flux along the short circuit axis of oscillation of the driven object with respect to the position of correspondence will result unless special means are provided for counteracting the tendency of the system to oscillate. For the pur 30 pose of preventing hunting, the frequency of oscillatory motion which is applied to the pilot device is not permitted to exceed a certain arbitrarily chosen value which is substantially less than the natural period of oscillation of the I system itself. In addition, connections are pro vided between the follow-up motor and the input circuit of the electric valve ampli?er and a high pass ?lter, constituting an anti-hunt network, is included in these connections. This ?lter has a cutoff frequency above the maximum frequency of oscillatory movement of the pilot device under normal conditions but below the natural fre quency of oscillation of the follow-up system itself. Thus when a tendency of instability of the system is present, the oscillating component is strongly set back into the ampli?er in such machine 13 is produced by the armature reaction of the short circuit current, and if it is desired to limit the short circuitcurrent to a low value, a portion 'of the flux along the short circuit axis may be produced by means of a shunt ?eld wind ing (not shown). This short’ circuit axis ?ux generates the voltage which appears across the load brushes 13b, and the control axis flux pro duces the voltage which appears across the short circuited brushes l3a and causes short circuit current to flow. The compensating ?eld winding IE6 is so de signed and connected that it neutralizes the armature reaction produced by the load current substantially 100 per cent. Consequently, the main control ?eld windings I30 and l3d are only required to produce the amount of flux necessary to cause current to flow in the short circuit. Since the resistance of the short circuit is so low as to be almost negligible, the control ?eld windings 13c and [3d are only required to produce a very phase as to counteract the oscillation. small ?ux in order to produce a large current in For a better and more complete understanding the short circuit and a correspondingly large of the invention, reference should now be had to 50 armature flux. Furthermore, since the ?ux of the following speci?cation and to the accompany the control ?eld winding need only build up to ing drawing, the single ?gure of which is a simple, such a low value, and since the reactance of the diagrammatical illustration of an embodiment of short-circuited armature is very low, full load the invention. current in the short circuit axis will be obtained Referring now to the drawing, an object I0 is 65 in an exceptionally short time. The important 2,406,143 3 4 The stator and rotor windings are arranged in inductive relationship with each other so that the characteristics of this armature reaction excited machine is are its exceptionally high speed of alternating magnetic ?eld produced by the cur rent ?owing in the primary winding induces volt» response, and its extremely high ampli?cation factor, i, e., the ratio between the magnitude of the current ?owing in the control ?eld winding l3c or IM and the magnitude of the current which ?ows in the output circuit of the machine. ages in the elements of the secondary winding. The receiver regulator 28 is in all respects iden tical with the transmitter 21 and the terminals of electric valves l6 and H which constitute a single stage ampli?er. Although electric valves l6 and the stator Winding of the transmitter cause cur rents to ?ow in the stator winding of the receiver its stator winding are connected to the terminals The control ?eld windings I30 and [301 on the of the stator winding of the transmitter by means control axis of the armature reaction generator l3 are connected in the cathode-anode circuit of 10 of conductors 29 so that the voltages induced in 1? may be of any suitable type, they are prefer ably screen grid transmitter type quick heating tubes connected for duplex operation, and pro regulator, thereby producing a magnetic ?eld similar to the magnetic ?eld produced by the cur 15 rent flowing in the rotor winding of the trans vided with a self-biasing resistor l8. Fixed volt ages are applied to the screens and anodes of valves l5 and H by means of a transformer is having a primary winding 19a and a plurality of mitter. The rotor of the transmitter 21 is mechanically connected through suitable gearing (not shown) to the movable element of the pilot device H. secondary windings I91), I90 and I9d. As shown, 20 For the purpose of increasing the accuracy and sensitivity of the control, the ratio of this gearing the primary winding I9a is supplied from a suit between the pilot device and the rotor of the able source of alternating voltage which is indi-q transmitter can be made as large as is desired, cated in the drawing by the two supply lines 2%]. for example, the‘ratio may be as great as 72:1, The cathode-anode circuits of valves It and H are traced from the midpoint of the secondary 25 i. e., for each degree that the pilot device is ro tated, the rotor of the transmitter is rotated 72 winding of the ?lament transformer 2i through degrees. The rotor of the receiver regulator 28 the self-biasing resistor 18 and conductors 22 and is connected either to the shaft of the motor P2 23 to the junction point of the control ?eld wind or to the shaft of the driven object it by means ings E30 and Kid and thence through these two ?eld windings in parallel and the secondary wind 30 of suitable gearing (not shown) having the same ratio as the gearing between the pilot device and ings I90 and I901 of anode transformer is to the the transmitter. anodes lea and Na of valves l5 and ill. The The initial relative arrangement of the rotors cathode grid circuits of valves is and H are of the transmitter 2'? and receiver regulator 28 traced from the midpoint of the secondary wind ing of the ?lament transformer 2i through the 35 is such that when the system is in correspond ence, the axis of the rotor winding of the receiver self-biasing resistor I8, resistors 24 and 25 in par 28 is at right angles to the axis of the magnetic allel, the secondary windings 26a and 26b of grid ?elds produced by the currents flowing in the transformer 26 to the control grids ltb and Ill). stator winding so that the voltage induced in the The voltages of the grids i621 and Ill), respec rotor winding is zero. Rotation of the rotor mem tively, as a result of the inclusion of the biasing ber of the transmitter causes a voltage to be in resistor l 8 in the anode-cathode circuits of valves duced in the rotor winding of the receiver owing [6 and I7 are such that both valves 56 and ii to the shift in the position of the axis of the mag normally conduct equal amounts of current. This netic ?eld of the receiver relative to the axis of condition of equal conduction in both valves l6 the coil of the rotor member, and the magni and H occurs when the follow-up system is in tude of this induced voltage depends upon the correspondence, i. e., when the driven object I!) relationship of the axis of this winding to the is in positional agreement with the pilot device axis of the magnetic ?eld, e. g. when the axes ll.v The currents conducted by the valves in and of the magnetic ?eld and of the rotor winding l‘! excite the control ?eld windings I30 and 13d of the armature reaction excited generator I3. 50 are parallel, the induced Voltage is maximum, whereas when these axes are at right angles with However, since the control ?eld windings‘ £30 and each other, the induced voltage is Zero. It will ltd act in opposition to each other, the net ex therefore be clear that rotation of the rotor of citing ?ux along the control axis of the generator the transmitter or of the receiver regulator, will l3 is zero and therefore the voltage at the load vary the magnitude of the component voltage brushes 13b is zero. supplied to the grid circuit of the electric valves In order to vary the bias voltages of the grids I5 and IT which, in turn, will result in varia It?) and ill), a component voltage of variable tion in the relationship of the current ?owing magnitude is supplied to the grid circuit substan in the anode-cathode circuits of these valves. tially in phase with the anode voltage through the transformer 26, whose secondary windings 60 The connections between the control grids l6?) and ill) are such that when the voltage applied 26a and 26b are connected in the cathode grid to one of the grids is increased, the voltage ap circuits of the valves [6 and H, as explained in the foregoing, and whose primary winding 250 is connected to the single phase alternating cur rent source 28 through rotary induction appa ratus illustrated as comprising a rotary induction device 2'! referred to as the transmitter and a similar rotary induction device 28 referred to as plied to the other grid is simultaneously de creased and consequently when the current sup» plied to one ofthe control ?eld windings of the generator I3 is increased, the current supplied to the other is correspondingly decreased. The large gear ratios between the transmitter 27 and pilot device H and between the receiver 23 and the receiver regulator. The rotary induction de vice Z'l comprises a rotor member 2111 provided 70 driven object W provide a very ?ne and a very accurate control. If the ratio is 72:1 as assumed, with a single phase primary winding (not shown) then for each ?ve degrees of rotation of the pilot and a stator member 21b provided with a dis device, the rotor of the transmitter 2'! is rotat~ tributed three-element winding (not shown‘) ed 360 degrees. However, since the axes of the which is physically similar to the polyphase winds rotor winding of the receiver 28 andthe mag ing of an ordinary wound rotor induction motor. 2,406,143 netic ?eld of the stator are parallel at two points in each complete revolution of the transmitter, i. e., at zero degrees revolution and grees revolution of the transmitter, clear that the pilot device and the lect must not be allowed to become at 180 de it will be driven ob~ more than 21/2 degrees out of correspondence with each other, while under the control of the high speed ?ne control system, because when this amount to the control grids 16b and Nb and is thereaf ter effective in controlling the valves I Band IT. For .the purpose of preventing hunting in the operation of the system, an antihunting network 35 is provided. This antihunt network is in cluded in the connecting lines between the fol low-up motor l2 and the grid or input circuit of the electric valves l6 and l‘! and. it comprises the capacitor elements 36 and 31, the resistor 10 element 38, and inductance element 39, and re sistor elements 24 and 25. The capacitor ele of positional disagreement occurs, the same re lationship exists ‘between the rotors of the trans mitter and the receiver as exists when the pilot ments 36 and 31 are connected in series in the device and driven object are in correspondence connecting lines between the armature terminals with each other. Under actual operating con of motor [2 and the input circuit of valves l6 ditions, the rotor of the transmitter often does 15 and I7, and resistor 38 and inductance 39 are become more than 21/2 degrees out of corre connected in series with each other across the spondence with the driven object, and a coarser connecting lines. Similarly, the resistors 24 and system is therefore provided for taking over the 25 are connected in series with each other across control from the high speed ?ne control system the connecting lines. The antihunt network op before this amount of positional disagreement is erates as a high pass ?lter having a cutoff fre exceeded. This coarse system is illustrated as quency that is greater than fa which is the comprising a transmitter that is, identical highest frequency of any oscillatory component with the transmitter 27 and a receiver regulator of motion of the pilot device ll so that the out 3| that is identical with the receiver regulator put of the antihunt network is minimum in the 28. The single phase rotor winding of the trans 25 region of fa. The antihunt network is designed mitter 30 is connected to the alternating voltage to have a maximum output in the region of fb source 20, and the single phase rotor winding of which is the natural frequency of oscillation of the receiver regulator Si is connected to the ter the system. minals of the primary winding 32:; of the trans The system is designed so that ft is several former the terminalsv of the secondary wind times as great as fa- The connections from the ing 32b of which are connected to the grids it?) antihunt network to the follow-up motor l2 and and ill) through electric valves and 3%. The from the antihunt network to the input circuit midpoint of this secondary winding 32b is co‘ of' the electric valves are such that the voltage nected to the junction point of the resistors fed from the network to the input circuit is 180 and 25. The stator winding-s of the transmitt 35 degrees out of phase with any oscillation or in 30 and the receiver regulator 3| are connected to cipient oscillation of the load l0 with respect to each other by means of conductors the position of correspondence. In addition, the The rotor of the transmitter 38 is directly con~ design of the antihunt network is such as to nected to the rotatable member of the pilot de~ pass substantially zero out of phase components. vice II by means of suitable gearing having a V40 In other words, the network is not sharply tuned ratio such, for example, as 2:1, the rotor to any frequency less than it. member of the receiver regulator 35 is connect The foregoing desired characteristics of the ed through suitable gearing (not shown) having antihunt network may be obtained by designing a similar ratio, to the driven object it. Thus it the network so that the elements thereof have will be seen that the transmitter the re 45 ceiver regulator 3! constitute a low speed sys tem and provide t -e desired coarse control. The electric valves 33 and 34 may be of any the following values: (1) 300,060 03a: ML (2) c37=-——‘20%O‘/LC“ suitable type but are preferably of the two—elec~ 24--25 trode type into the envelopes of which a small 50 in Which, quantity of an inert gas such, for example, as neon is introduced. A characteristic of a valve of this L is the inductance of coil 39 in henries, character is that when a voltage of less than a predetermined value is applied to its terminals, the valve does not conduct current and that when this volt-age is exceeded, the neon gas becomes ionized and the valve becomes conducting. The transformer preferably a very high step-up ratio of the order of 56:1, so that when C36 is the capacity of capacitor 36 in microfarads, C37 is the capacity of capacitor 31 in microfarads, R24-25 is the resistance of resistors 24 and 25 in ohms, ft is the natural frequency of oscillation of the system in cycles per second, fa is the highest frequency of any oscillating the positional disagreement of the pilot device and 60 component of motion of the pilot device. driven object is less than a predetermined amount, e. g. 21/2 degrees or less, the voltage ap plied to valves 33 and 31% is less the ioniza tion or breakdown voltage of these valves, but equals or exceeds the ionization voltage when the positional disagreement equals or exceeds this predetermined amount. Thus, when the po sitional diagreement is less than this predeter mined amount, the control connections between the coarse control system and the grids of valves l6 and I‘! are interrupted and the coarse con cl system is ineiiective, and when the disagreement equals or exceeds this amount, the valves become conducting and the voltage induced in the sec ondary winding of the transformer 32 is applied The value L of inductance coil 39 may be arbi trarily chosen and the resistance of resistor 33 may best be ‘determined empirically after the values L, C36 and C37 have been determined. The resistance of resistors 24 and 25 and the induct ance of coil 39 should be as large as is convenient in order that the capacitors 3S and 3‘! may be of reasonable size. With the foregoing understanding of .the ele ments and their organization in the completed system, the operation of the system itself will readily be understood from the following detailed description. Since the operating coil of the relay 4!] is connected across the source 20, the relay 75 picks up and its movable contacts 40d and 40b 2,406,143 engage the stationary contacts 40d and 40a, re spectively. Contacts 40a and 4001 in closing com plete an energizing circuit for the ?eld winding l2a of the follow-up motor, and contacts 401) and 40c in closing remove a short circuit about a portion of the compensating ?eld winding [36 of the armature reaction excited generator 13. Assuming that the pilot device H and the 8 Had the departure from correspondence been in the opposite direction, the operation of each of the elements would be similar but opposite to that of the operations thus far described with the re sult that the motor l2 would have driven the driven object in the reverse direction. Whenever the positional disagreement of the pilot device and driven object becomes less than the predetermined amount at which the valves 33 driven object it) are in positional agreement, the system is in its normal deenereized condition in 10 and 34 become ionized, the voltages applied to the valves 33 and 34 will become less than the ioniza which it is illustrated. As previouslyv pointed tion voltage of these valves, and the valves will accordingly become non-conducting. The result I‘! are conducting equal amounts of current so of this is to interrupt the control connections be that the opposing control ?eld win-dings I30 and l3d of generator 13 are equally excited and the 15 tween the low speed coarse control system and the input circuit of the valves 18 and ll, thereby to output voltage of the generator I3 is zero. Man out, when in this condition, both valves l6 and ual or power driven rotation of the pilot device ll effects a corresponding but multiplied rota tion of the rotor of transmitter 21, causing a rotation of the magnetic ?eld of the stator of receiver regulator 28 so that a voltage is in duced in the rotor winding of the receiver regu render the low speed coarse control system in effective and to re-transfer the control to the high speed ?ne control system. .As previously pointed out, the operation of the system as described in the foregoing is modi?ed during acceleration and deceleration by the ac tion of the antihunt network. Whenever there lator proportional to the amount of rotation of exists a tendency of the system to oscillate as the pilot device ll. This induced voltage is ap plied to the grid circuits of electric valves [6 25 usually occurs during acceleration or deceleration, an oscillating component of voltage derived from and i7 and results in increasing the current ?ow the follow-up motor 22 is very strongly fed back ing in one of the valves and decreasing the through the antihunt network 35 to theinput cir current ?owing in the other valve. Assuming cuit of the amplifier valves 16 and l"! in such a that the direction of rotation of the pilot device is such as to increase the current ?owing in the 30 phase as to counteract the oscillation. In other words, for rapid changes of velocity having an valve [6 and to decrease the current ?owing oscillating component of motion, a high feed— through the valve H, the excitation of control back exists, while for constant velocity no feed ?eld winding I30 will be increased and the ex back exists. citation of control ?eld winding 13d will be de creased. The difference in excitations of the two 35 Although in accordance with the pro-visions of the patent statutes this invention has been ex» opposing ?eld windings I30 and Kid produces a plained as being embodied in concrete form and net excitation along the control axis of the gen the principle thereof explained, together with the erator l3, and as a result, the generator l3 sup best mode in which it is now contemplated ap plies current to the armature of the follow-up motor l2 in such a direction that the motor is 40 plying that principle, it will be understood that the apparatus shown and described is merely il caused to rotate in a direction to drive the object lustrative and that the invention is not limited I0 toward correspondence with the pilot de thereto, since alterations and modifications will vice II. readily suggest themselves to persons skilled in If the driven object IQ can not follow the the art without departing~ from the true spirit of rapid movement of the pilot device ll so that this invention or from the scope of the annexed the positional disagreement of the driven object claims. and pilot device equals or exceeds the prede What I claim as new and desire to secure by termined amount, the voltage induced in the Letters Patent of the United States is: secondary winding of the transformer 32 becomes 1. A follow-up control system comprising in so great that the voltages across electric valves _ combination, a pilot device, a driven object, an 33 and 34 exceed the ionization voltages of these valves and cause them to become conducting. Voltages continue to be induced in the second ary windings 26a and 26b of the transformer 25 after the electric valves 33 and 34 have be- ; come conducting, but owing to the high resist ance of resistors 4| and 42, the voltages induced in the secondary windings 26a and 261) are no electric motor for driving said object, means re sponsive to disagreement of said pilot device and driven object for producing a signal voltage cor responding to said positional disagreement, am pli?er means responsive to said signal voltage for supplying a voltage to said motor to cause said motor to drive said object toward correspondence with said pilot device, an antihunt means com longer effective and the electric valves I6 and H are controlled solely by the voltage induced in (30 prising a high pass ?lter having a cutoff frequency substantially lower than the frequency of the the secondary Winding 32b of transformer 32. natural period of oscillation of said system and Thus when the electric valves 33 and 34 become connected between the armature terminals of said conducting, the control connections between the motor and the input to said ampli?er. low speed coarse control system and the electric 2. A remote follow-up control system for a pilot valves 16 and I’! are completed and the control device and driven object in which the frequency of the follow-up system is effectively transferred of oscillatory movement of the pilot device is sub— from the high speed ?ne control system to the stantially less than the natural frequency of oscil low speed coarse control system. As a result, a lation of said system comprising in combination, voltage is applied to the input circuit of electric valves [6 and ll of such magnitude that the cur 70 an electric motor for driving said object, an elec tric valve type ampli?er provided with an input rent supplied by armature reaction excited gen ircuit and with an output circuit operatively as erator l3 to the follow-up motor i2 causes the sociated with said motor, means responsive to po latter to drive the driven object ill at maximum sitional disagreement of said pilot device and speed in the same direction as that in which the 75 driven object for supplying a signal voltage to said pilot device H is moving, 2,406,143 input circuit corresponding to said positional dis agreement thereby to control the Voltage sup plied to said motor to cause said motor to drive said object toward correspondence with said pilot device, and antihunt means responsive to the terminal voltage of said motor for supplying a feedback voltage to said input circuit comprising a high pass ?lter having a cutoff frequency inter mediate said frequency of movement of said pilot device and said natural frequency of said system. 3. In a follow-up control system for causing a driven object to follow the movements of a pilot device and in which the frequency of oscillatory movement of said pilot device is substantially less than the natural period of oscillation fb of said system, an electric motor for driving said object, an electric valve type ampli?er provided with an output circuit operatively connected to said motor and with an input circuit, means responsive to positional disagreement of said pilot device and 20 driven object for supplying a signal voltage to said input circuit corresponding to said positional dis 10 agreement thereby to control the voltage supplied to said motor, and antihunt means comprising means for deriving a voltage from said motor, and a high pass ?lter connected between said voltage deriving means and said input circuit and com prising a connecting line having lumped resist ance R1 and lumped impedance L connected in se ries with each other and in shunt across said line, and a ?rst lumped capacitance C1 in series with said connecting line substantially equal to $0,000 1100292 and a second lumped resistance R2 in shunt across said connecting line and a second lumped capaci tance C2 in series with said connecting line and equal substantially to zoom/f6? R2 SIDNEY GODET.