Патент USA US2411871код для вставки
Dec. 3, 1946. 2,411,871 G. DE; WESTFELT SERVO SYSTEM Filed Nov. 2. 1942 PHASE SENSITIVE l5 ~/ M RECTIFIER I4 INVENTOR , GERARD HIS DEWESTFELT; ATTO R N EY. Patented Dec. 3, 1946 2,411,871 UNITED STATES‘ PATENT OFFICE SERVO SYSTEM Gerard de Westfelt, New York, N. Y., assignor to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a corporation of New York . Application November 2, 1942, Serial No. 464,297 5 Claims. (Cl. 172-239) ;This invention relates to electrical servo sys tems and refers more particularly to an im proved type of control for the driving means of such systems. - A servo system operates to apply a strong driving force in response to a weak controlling force or signal. The ampli?cation of the weak signal may be‘ brought about by a variety of . 2 driven object to an element controlling the out put of the system, a servo system is adapted to cause the driven object to repeat the position of the controlling object, and the invention has particular application to positional control systems of this time because of the smooth and reliable operation obtained. Anti-hunting means may be included to overcome any tend known means, such as thermionic ‘ampli?ers. ency of the controlled object to overshoot the .While the ampli?cation ratio of a thermionic 10 'position of rest or to hunt about that position. ampli?er may be high such devices are not adapt It is one object of the invention to provide ed in their usual forms to supply a large power A. C. ampli?er means adapted to supply a rela output. ‘ tively large power output. ‘ When higher outputs were required, certain Another object is to provide a servo or posi types of rotating electrical machines have, in 15 tional control system having improved driving prior systems, been used as D. C. power ampli means control. ?ers,~either alone or in conjunction with ther A further object is to provide power ampli? mionic means. The use of these machines has cation means employing rotating machines required that commutators and brushes be in without introducing commutators into the cluded in the amplifying circuit, thereby ren amplifying circuit. dering the ampli?er subject to the known dis Other objects and advantages will become advantages of commutators, including wear, apparent from the speci?cation, taken in con sparking and variable contact resistance. nection-with the accompanying drawing where These disadvantages of commutator machines in the invention is embodied in concrete form. are highly objectionable in amplifying appa 25 In the drawing, ' ratus, which greatly magni?es any electrical Fig. 1 is a wiring diagram of one form of con disturbance. , trol system, according to the invention. To overcome the disadvantages of prior sys Fig. 2 is a wiring diagram of a complete po tems, the present invention provides servo sitional control system utilizing the improved means comprising a power ampli?er stage which 30 means of the invention. has no commutators in the. amplifying circuit Referring particularly to Fig. 1, the control and is adapted to furnish graduated and re ling object is illustrated as hanclwheel In, al versible control of rugged A. C. driving means though obviously such handwheel may be re in the form of a polyphase induction motor. placed by any positionable memberI including Such a motor, too, avoids the disadvantages of 35 the movable member of a sensitive instrument. I commutators. Handwheel i0 is connected to position primary It is known that to control polyphase motors, l2 of transformer l4, angularly, with respect for example, a two-phase motor, it is .only to secondary winding l5 of said transformer. necessary to vary or reverse one stator phase, the other phase being constantly Winding i2 is connected to a source of alter excited. 40 nating potential l6. Winding l5 therefore re According to the invention, this control of one ceives an induced alternating potential propor motor phase is exercised by the output of a tional to the angular position of winding II, single phase alternator the strength of whose this potential reversing in phase as the axis of ?eld current is governed by the weak signal or winding l2 crosses a line perpendicular to the a version thereof. To provide constant excita 45 axis of winding [5. , tion for another or other phases of the driving The variable magnitude, reversible phase motor, a second alternator is driven synchro potential induced in winding I5 is applied to nously with the control alternator (to secure a phase-sensitive recti?er l8 which derives its current'of the same frequency) and in order phase discriminating properties from a connec to provide the necessary time phase displace 50 tion to source I 6.1 Recti?er I8 supplies, as an ment between the currents of the different mo output. a continuous potential reversing in tor phases the magnetic axes of the two alter - polarity with reversal ‘of phase of the input to nators may be angularly offset, thus obviating the need tor phase shifting networks. When provided with a repeat-back from the the recti?er. Such phase-sensitive recti?ers are well known in the art, one‘form which may be adapted for use‘ with the arrangements or “ i 2,411,871 Fig. 1 being shown in Fig. 2, to be described hereinafter. The output of recti?er I8 is ap plied to the stationary ?eld winding 26 of a single phase A. C. generator 2| having a rotor constantly driven by D. C. motor 24, connected 5 chm-transformers." _Winding 59 is ‘ center tapped and has the central point thereof con ' nected to the cathode of balanced modulator tube 66 and the outer terminals thereof respectively connected to the two control grids of tube 60. Biasing means, illustrated as grid battery 62, to D. C. source 25. Likewise driven by motor 26, is a. second A. C. single phase generator Z'l having a ?eld 28 con- ' ‘tube 60 to bias the two sections or the tube to stantly excited from source 25. serve as modulators or recti?ers. The anodes or The output may be included in the grid-cathode circuit of amplitude and phaserexcites ‘stator winding 3! 10 'plates of tube 60 are supplied with alternating potential from source I6, by way of a center-tap of generatorv 2'5, at a substantially constant on ?eld winding 55 of A. C. generator 66. Con amplitude and phase, excites stator winding 3i dens‘ers 6i, 6'?’ are bridged across the two halves of two-phase induction motor 39, having 'a of the output circuit of tube 60. respectively, to squirrel cage rotor 32. The second stator phase 33 of motor 3G is excited by the output of gen .15 \provide low impedance paths for the A. C. com--v vponents of the tube outputs. The current in erator 2i. This latter output varies in ampli coil 65, because of the high inductance of the coil, tude with variation of the excitation of ?eld is substantially continuous. winding Eli and reverses in phase with reversal The output of generator 66 is conducted by way of the direction of the current through wind of brushes and slip rings as to stator winding 33 20 ing 29. . A. C. generators 2i ‘and 2? maybe of the in l ductor type and have similar characteristics. Either the output or the input connections are made .by way of slip rings, depending upon whether the armature or. ?eld is the rotating 25 member. As here illustrated the output connec of motor 38 as in the arrangement of Fig. 1. A. C. generator ‘38, corresponding to generator 21 of Fig. 1, may be of the same design as‘ generator 86, no connection being made to the center-tap on its ?eld winding. The load driven by'motor Bil-by way of gears ‘l2, "i3 is shown in Fig. 2, by way of example, as a rotatable platform ‘85 which tion from generator 28 is by way of slip rings 23. may mount an object having substantial iner It is known that slip rings and brushes are much tia, such as a gun or Searchlight. A repeat-back more constant in operation than commutators. Since a very small change of current in ?eld it 30 connection is shown for rotating “selsyn” wind ing '59, including pinion ‘ll meshing with gear may produce a large change of generated voltage 73, and shaft ‘58 connected by gearing and shaft in a low impedance circuit, it will be seen that ing to shaft 8h. ' the device provides means for securing high am Additional ampli?cation by thermionic means pli?cation and relatively large power output with out a commutator in the amplifying cincuit. 35 may be provided and it is desirable that suitable rate taking and phase adjustment circuits be ‘in Constantly excited generator 2? being driven by cluded to insure that the system shall be stable the same motor which drives generator 2i, the and free from hunting tendencies. Such cir frequency of the inputs to motor windings 3i and cults are well known. 33 is the same regardless of the speed of the mo» In operation, displacement of handwheel it tor. The required phase displacement between an induces voltages in the three-part winding 52 ‘of the generator output voltages may be secured by ,“selsyn” transmitter 59 which are transmitted to angularly displacing the magnetic axes of. the synchro-transformer 57 to reproduce the direc ' generatorsas has been noted. For a two-phase I tion of the axis of transmitter winding 5i‘ as a motor this‘displacément is 90° and with similar generators this displacement may be obtained at; corresponding direction of vthe resultant ?eld of three-part winding 58 of receiver 5?. Winding by relatively positioning the two rotors at this ' 5Q thereby receives an induced voltage propor angle on the driving shaft. tional to its angular displacement from the nor In operation; angular displacement of hand» mal to said ?eld direction, said induced voltage wheel it or other controlling object rotates wind-= ing l2 and thereby, through described interme 50 being of reversible phase, as described in con diate means, varies the direct current in wind-' ing it of alternator 28. This current is zero or a minimum when the axis of winding'l? is per» 1lriectillm with the operation of transformer id of placementoi the axes of windings l2 and it, and ‘ the direction of this torque is reversible with re controlling the current, in winding 33 of motor 3t. ing three part winding 52, connected by three made responsive to a factor having a distinctive value at stand-by, such as rotor speed or torque. As many changes could be made in the above g. . ' Since the plate circuits of tube 3e are supplied with alternating potentials of the same ireouency pendicular to that oi‘ winding id, and a maximum ‘ when the two axes are parallel. The current in 55 as the input signal, the balanced modulator is rendered phase sensitive, as is known to those winding 36 of motor 39 being constant and the skilled in the art, and a continuous current will be current in winding 33 being proportional to the supplied to one half or the other of the ?eld current in winding 2d, (but of much greater am winding $5 of A. C. generator as, dependent upon plitude) motor so exerts a torque tending to dis“ place load dd in proportion to the relative dis 60 the phase of the input to tube ?t, thus reversibly While the excitation of one phase of induction motor 35’) has been described as being substan= versal of the phase or“ the current in winding tially constant, this excitation may, within the Referring now to the arrangementoi' Fig. 2, handwheel it is shown as angularly positioning 65 scope or the invention, be reduced or even elimi nated under stand-by conditions to reduce the the single winding‘ iii of a “selsyn” transmitter power then consumed. Such reduction may be ht having a relatively stationary member mount-1 conductor transmission lines to “selsyn” reg ceiver 57 having a relatively stationary three-part winding 53 and a rotatable single winding es. Selsy‘n El is operated as a locked or positioned ro construction and many apparently widely differ ent embodiments of this invention could be made without departing from the scope thereof. it is tor device by virtue of a mechanical repeat-back intended that all matter contained in the above from the driven object. Such devices are some-' times referred to as “signal generators” or “sync 75 description or ‘shown in the accompanying draw 7 2,411,871 ing shall be interpreted as illustrative and not in a limiting sense. Having described my invention, what I claim and desire to secure by Letters Patent is: 1. In combination, a motor, a pair of alternat positional disagreement of the controlling and controlledobiect. and a repeat-back connection from the controlled object to said last means. 4. In a positional control system controlling and controlled objects, a two-phase induction motor driving the controlled object, means for ing current generators coupled thereto and driven thereby to supply outputs of the same frequency supplying current of the same frequency to the in substantially 90° phase relationships, a two ?elds of said motor in diil‘erent time phase rela phase motor having the ?elds thereof excited by tionship comprising a motor, a Pair of angularly potentials respectively derived from the outputs 10 spaced generators synchronously driven thereby of said two generators, and thermionic means and respectively connected to supply current to adapted to receive a reversible phase input and said motor ?elds, a source of direct current, one supply a. reversible polarity continuous output pro of said generators being constantly excited from portional thereto for reversibly exciting at least said source to supply substantially constant am one of said generators to control the magnitude 15 plitude current to one phase of said two-phase and direction of the torque exerted by said .two motor, means providing variable excitation for the other of said generators in proportion to the 2. In a servo system, substantially constant positional disagreement of said controlling and speed driving means, a pair of alternating cur— controlled objects, and repeat-back means from rent generators driven thereby at the same speed, 20 the controlled object to said variable excitation means constantly exciting one of said generators, > means. means furnishing a reversible phase alternating 5. In a positional control system of the Ward potential measuring the angular position of a dis Leonard type, having controlling and controlled placeable member, phase sensitive means for con ‘objects, a two-phase induction motor for driv verting said alternating potential into a reversible 25 ing the latter, a pair of continuously driven A, C. polarity continuous potential, circuit means uti generators for supplying two alternating currents lining a version of said last potential .to excite to said motor at substantially 90° out of phase, phase motor. . .the other of said generators and a two-phase mo one of which is variable in magnitude and re tor having the phases thereof excited by poten versible in phase for driving said controlled ole tials respectively derived from the outputs of said 30 ~ject at variable speed in either direction, means generators. 3. A positional control system comprising a controlling object, a controlled object, a two producing an A. 0. signal proportional in magni tude and reversible in phase with the amount and direction of relative displacement of said objects, phase induction motor driving the controlled ob and a phase sensitive recti?er connected thereto Ject, means constantly exciting one ?eld of said for supplying D. C. to the ?eld or one of said motor and variably exciting the other ?eld, both generators which varies in magnitude and direc at the same frequency, including a motor, a pair tion with the magnitude and phase sense of the of alternating current generators synchronously signal, whereby the variable field of said motor driven thereby in out of phase relationship, each of said generators supplying current to one phase 40 varies from zero in either of two opposite phases to drive said motor in a direction and speed to of said motor and means for varying the relative maintain synchronism. _ excitation of said generators in proportion to the GERARD on WESTFELT.