US2418193A - Self-synchronous motion reproducing system - Google Patents

Description

April 1, 1947. J. D. PETERSON 2,418,193

SELF-SYNCHRONOUS MOTION REPRODUCING SYSTEM Filed July 11, 1942 5 Sheets-Sheet l FECE/VER E u N [E I o v \Q 2K N o N I V W k r\ as gl INVENTOR.

Joel I ie/erson HTTURNE Y April 1947- J. D, PETERSON 3 SELF*SYNCHRONOUS MOTION REPRODUCING SYSTE Filed July 11, 1942 3 Sheets-Sheet 2 TRHNSM/TTE/i" RECEIVE? FREQUENCY DO0BLER 1N VEN TOR.

Jaelfl il ersan April 1, 1947- J. D. PETERSON 2,418,193

SELF-SYNCHRONOUS MOTION REPRODUCING SYSTEM Filed July 11, 1942 5 Sheets-Sheet 3 INPU T mvmm .hllfl Mason mrmy Patented Apr. 1, 1947 UNITED STAT SELF-SYNCHEQONOUS MOTIQN REPRODUCING SYSTEM Joel D. leterson, Ridgewood, N. .3 assignor to Bendix Aviation Corporation, Bendix, Ni 3., a

corporation of Delaware Application .liuly Ill, 19%, Serial No. 50,595

(El. ireess) lit tjiaians. 1

The present invention relates to means for reproducing motion, and more particularly to novel and improved means for reproducing angu lar motion at a remote point for indicating and/r control purposes.

One of the objects of the invention is to provide novel means for reproducing rnotion, con stituting an improvement over the means disclosed in the patent to W. A. Beichel, No. 2,269,602, dated, January 13, 1942, said patent being assigned to the same assignee as the present invention.

Another object is to provide a novel telemetric system wherein a transmitter of the self-synchronous motor type, generally known. as a "Selsyn motor, may be employed, using alternating current for energization thereof, and connected to a remote receiver of a direct current type instead of to a self-synchronous motor re ceiver.

A further object of the invention is to provide novel and improved means for reproducing motion, employing a transmitter of the type disclosed in the aforesaid patent to Reichel, No. 2,269,602, which employs a periodically varying or alternating current for energization thereoi, and electrically connected through rectifiers to a direct current type of indicator having a permanent magnet rotor, for example.

Still another object is to provide novel means for reproducing angular motion at a remote point, comprising a transmitter energized by an alternating current and electrically connected through rectifiers to a direct current type of indicator at the remote point, said indicator being additionally energized by direct current from a local D. C. source.

The foregoing and other objects and advan= tages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein thr bodiments of the invention are illustrated of example. It is to be expressly understood, however, that the drawings are for purposes illustration only and are not to be construed defining the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings:

Fig. 1 is a more or less diagrammatic illus-- tration of one embodiment of the invention wherein an alternating current transmitter oi the self-synchronous motor type is electrically connected to a remote receiver of a direct current ty e;

ig. 2 is a diagrammatic illustration of another embodiment wherein an alternating current transmitter oi a different type is connected to a direct current type receiver; and

Fig. 3 is another diagrammatic illustration of a third embodiment wherein the transmitter is lilse that of Fig. 2, but the receiver is somewhat different although still of the direct current type.

The invention consists substantially in the construction, combination, location and relative arrangement of parts and circuits for obtaining the results desired in accordance with the fore going objects, as will be more fully hereinafter set forth in the specification, as shown in the drawings by way of example, and as finally pointed. out in the claims.

Referring now to the drawings and more particularly to Fig. l, the novel apparatus embody ing the invention, comprises, in the form shown, an alternating current type of transmitter t which, in. this embodiment, is shown as a selisynchronous motor, and direct current type of receiver electrically connected to said trans mitter in a manner which will be explained more fully hereinafter.

The transmitter 4 comprises a rotor having a single phase winding 8 and a stator having three windings i, 8 and 8, one end of each being connected together at it in Y relation to term a three-phase type of winding arrangement c0nstituting the output of said transmitter.

The remote receiver 5 comprises a stator haying three direct current windings ll, l2 and i3 spaced 1% degrees apart around a rotor M which is in the form of a circular magnet having a north pole and a south pole indicated at N and S, said rotor being drivably connected in any suitable 0 manner (not shown) to a control device or, as

shown, to a pointer it of an indicator E6.

The rotor winding 6 of the transmitter 4 is arranged for energization by an alternating cur rent through leads it and it connected to the supply leads i9 and 2B. The supply lead it! is also connected to the common junction ill of the stator windings I, 8 and 9 the other ends of which are respectively connected to one input terminal of full-wave rectifiers 2i, 2 and 23 by means of leads it, 25 and 26, respectively, the other input terminal of each of said rectifiers being connected to the A. C. supply lead 20. Thus, a voltage is produced in each of the output windings i, it and 9 which is the algebraic sum of the voltage applied directly from the supply lines (9, 2G and the voltage induced in each of said windings by the rotor winding 6, the latter voltage varying in each of said windings 8 and 9 in accordance with the angular position of said rotor winding 6 with respect to the stator windings l, 8 and 9.

The resultant A. C. voltage in each of the windings 8 and 9 is then rectified by the full wave rectifiers 2|, 22 and 23, respectively, and the rectifled voltages are supplied to the D. C. stator windings |3, i2 and H, respectively, of the receiver, whereby a resultant uni-directional field is produced, the direction of which corresponds to the angular position of rotor winding 6 of the selfsynchronous transmitter motor 4. This resultant field reacts with the field of the magnet rotor ll of the receiver, whereby said rotor is caused to assume an angular position with respect to the stator windings |2, l3 and l corresponding to the angular position of said rotor windin 6 with respect to the stator windings l, 8 and 9 of the transmitter, as shown in Fig. 1, thereby actuating the pointer l of the indicator IE to indicate said position on a scale.

The rotor winding 5 of the transmitter may be actuated either manually or by a measuring device, the indications of which are to be transmitted to the remote point at which the receiver 5 is located. For simplicity, the actuating device is represented diagrammatically by the arrow 28 shown connected to the rotor 6 by the dotted line.

Referring now to Fig. 2, there is shown another embodiment of the invention, wherein the transmitter is of the type disclosed in the aforesaid patent to Reichel No. 2,269,602, but connected to a D. C. type of indicator. The transmitter is shown at 29 and the remote receiver at 30.

The transmitter 29 comprises a stator having an annular core 3| of highly permeable magnetic material such as Permalloy" or Mu-metal," for example, on which is wound a single phase primary or exciting winding 32 over the entire circumference thereof, said exciting winding 32 being connected for energization by an alternating current from supply leads |9 and 2|] by leads 33, 34 which are also connected to a frequenc doubler of any suitable type shown diagrammatically at 35, for a purpose which will be explained hereinafter. By virtue of the alternating current fiowing in the single phase exciting winding, the permeable core member 3| is periodically saturated at a frequency corresponding to the frequency of said alternating current.

Wound over said exciting winding 32 and in inductive relation therewith are three windings 36, 31 and 38 and are connected in three phase relation at the junction point 39 to form a Y-connected three phase type of winding.

Concentricaily arranged within the stator core member 3| and in magnetic relation therewith is a rotor 40 in the form of a magnetic member of marked polarity as, for example, a rotatable permanent magnet having north and south poles as indicated at N and S, providing a uni-directional magnetic field which enters the core member 3| at the north end of said rotor, divides into two paths so that part of the flux flows to the left and part to the right, as viewed in Fig. 2. These fiuxes then combine and emerge from the "core at the south end of the rotor where they enter the latter. The rotor magnet 40, in the present instance, is shown in the form of a disc, the upper half of which constitutes the north pole and the lower half the south pole thereof.

In the event that it is dcsir d to transmit the indications of a magnetic compa s to the remote point, the rotor 40 may be dispensed with, and the stator 3| placed under or above the compass in influencing relation with the compass magnet, whereby the latter then becomes the rotor of the transmitter.

Likewise, the transmitter 29 may be used as an earth inductor, in which event the rotor 40 may again be dispensed with and the stator placed in a horizontal position and arranged so as to be traversed by the earths magnetic field, the latter then traversing the core member 3| in the same manner as the uni-directional field of the rotor 40, but in that case the field obviously remains stationary and the stator is then moved angularly in azimuth.

The receiver 30 in the embodiment shown in Fig. 2 is a direct current type somewhat like that shown in Fig. l and, as shown, comprises a stator having three pairs of windings, one pair being shown at 4|, 42, the second pair at 43, H and the third pair at 45, 46, said pairs being arranged around a magnet rotor 41 and angularly spaced 120 degrees apart. The rotor 41 is drivably connected to actuate a pointer 48 over a scale of the indicator 49.

Upon energization of the exciting winding 32 of the transmitter 29 by the alternating current, voltages are generated in the three output windings 3S, 3'! and 38 due to the periodic reversal of the flux produced in the core 3| by said energizing current, because of the fact that during one halfcycle of said current the periodically reversing flux opposes the uni-directional flux of the magnet rotor 4|! in one half of said core 3| and. at the same time, aids said uni-directional flux in the other half of said core, while during the other half-cycle of said exciting current said periodically reversing flux aids the uni-directional fiux of the magnet rotor 40 in the one half of said core 3| and, at the same time, opposes said uni-directional fiux in the other half of said core, as fully explained in the aforesaid patent to Reichel, No. 2.269,602. The voltages thus generated in the output windings 36, 31 and 38 by the flux variations in core 3| are even harmonics, mostly second harmonics. of the fundamental frequency of the exciting current. These second harmonic voltages are in phase and vary only in magnitude with the position of the magnet rotor 40 with respect to the three windings 36. 3! and 38 which are angularly spaced 120 degrees apart around said core 3| and, hence, with respect to the rotor 40.

Means are now provided for dividing the output voltage from each of the windings 36, 31 and 38 into two portions, combining each of the two portions with a reference voltage in a pair of rectifiers in such a manner that one rectified portion aids the rectified reference voltage and the other rectified portion opposes the rectified reference voltage so that the output voltage from one rectifier is the sum of one of the portions and the referenee voltage, and the output voltage from the other rectifier is the difference between the other portion and the reference voltage. To this end the output coil 36 is connected by means of a lead 50 to a common lead 5| connecting one side of the input of a pair of rectifiers 52 and 53, and the output coil 3'! is connected by means of a lead 54 to a common lead 55 connecting one side of the input of another pair of r-"etilicrs 56 and 51, while the output coil 38 is likewise connected by means of a lead 58 to a common lead 59 connecting one side of the input of a third pair of rectifiers 60 and 6!.

The other sides of the inputs of rcctifiers 52. 56

and iii are connected by a common lead 2 to one output terminal of the frequency doubler 35 which supplies the reference voltage, and other sides of the inputs of rectifier- 53, 51 Elli are connected by means of a common lead 83 to the other output terminal of the frequency doubler Since the output voltages from coils 36, 3? and 38 are second harmonics of the fundamental frequency of the exciting current flowing in the input coil 32 of the transmitter 29, the reference Voltage must be of the same frequency as the output voltages, For this reason the frequency doubler is employed in order to double the frequency of the alternating current from the same sourc from which the exciting; winding 32 is energized.

The resultant rectified voltages are now used to energize the respective pairs of stator windings -42, 43-44 and Fl-45 of the receiver. Accordingly, the output of rectifier 52 of the pair of rectifiers is connected to stator coil Toy means of leads 64, [it whil the output of rectifier 53 of the same pair of rectifiers is connected to stator coil 44 by means oi. leads 8%, 8?, said coils 3, 65 being in inductive relation with each other and, as previously pointed out, constitute one pair oi the three pairs of stator coils angularly spaced 120 degrees apart around the magnet rotor ll of the receiver.

Likewise, the outputs of the second pair of rectifiers 56, iii are respectively connected to the second pair of stator coils H, 42 by means of leads 68, 59 and "in, ii and the outputs of the third pair of rectifiers to, El are respectively connected to the third pair of stator coils 45, to by means oi loads l2, l3 and M, HE.

Now, by virtue of the arrangement of each of the pairs of rectifiers 52-53, 56-El and lit-hi, the one rectified portion oi each of the output voltages from coils 36, 3?, 38 opposes the rectified reference voltage as shown by the two arrows pointing in opposite directions in rectifiers 5%, 56 and 6!, while the other rectified portion oi each of the output voltages from coils 35, 31, 38 aids the rectified voltage as shown by the arrows pointing in the same direction in rectifiers i3, 51 and 66.

Thus, the direct current in each of the stator coils H, 43 and 4-5 of each cooperating pair of coils is the difference between the rectified voltage from each of the output coils 36, 31, 38 and the reference voltage, While the direct current in each of the stator coils 42, N and 56 of each cooperating pair is the sum of the rectified volt age from each of said output coils 36, El, 38 and the reference voltage. The resultant uni-direc tional magnetic field produced at the receiver til by the direct currents flowing in the three pairs of coils ii-42, i3-44 and 45-46 will now have a direction such that when it reacts with the uni-directional field ofthe receiver ill, the latter will be caused to rotat angular position corresponding to the position of the transmitter magnet rotor id, thereby actuating the pointer 43 to indicate said position. Thus, rotation of the transmitter rotor is transmitted to the receiver to cause corresponding rotation of the receiver rotor, and then the latter rotation may be used for indicating purposes as shown, Or the receiver rotor all may be connected to actuate a control element oi an automatic control system such as an aircraft automatic pilot, for example, when the transmitter is arranged to transmit a compass indication of the course on which the aircraft is to he maintained by the automatic pilot.

It is to be noted that neither the voltages irom the output coils 36, 31 and reference voltage from the frequency doubler acting alone, will produce a resultant held at the receiver, because in either case the fields oi the coils of each pair of stator coils will be equal and in opposite directions, but when the voltages from the output coils 36, $1, 38 and the reference citage act together, as described hereinbefore, the resultant held at the receiver will be in such a direction as to rotate the receiver rotor t! to an angular position corresponding to the angular position of the transmitter rotor lii.

A third embodiment of the invention is shown in Fig. 3 wherein the transmitter substantially the same as that shown in Fig. 2, except that the output coils 38, 3'! and 38 are not f-connected out each has two separate output terminals. Nevertheless, the output voltages from said out put coils 35, 3? and 33 are second harmonics oi the fundamental frequency of the alternating: current flowing in the exciting input Winding i2 and, therefore, the frequenc doubler is again used in order to provide reference voltage hav ing' the same frequency as the voltages from out put coils at, s tes. The receiver, shown at "E6, is also of the direct current type but is different from the receivers shown in Figs. Ii and 2 and, as illustrated, comprises a stator having three windings it, is and it connected at the junction to to icrm a Y-connected three-phase type of rotor, said windings being singularly spaced 120 degrees apart in the same manner as in the receivers of Figs. 1 and 2, and cooperate with a magnet rotor El drivably connected to a pointer an indicator 8t.

in Fig. 2, the second harmonic voltage of each of the output coils lit, 3'5, 38 is combined with reference voltage of the frequency, but by means of a special coupling transformer instead or in the rectifiers, and only three recti fiers are used instead of sin. The special coupling transformer, as shown, has four windings 85, i5, 86 and cl wound in inductive relation on a common core (not shown) the reference voltage being introduced in the wii; ti which is connected to the frequency do 4 er by means of leads t8 and as. This reference voltage is then induced into the windings M, 353 and $6 in which the second harmonic voltages are also present by virtue of the fact that one end of each oi the output coils 38, 31 and 38 is connected to one end of each of the windings BE, 84 and 85, respec-- tively, by means of leads so, 9% and B2, respectively. The other end oi each of said output coils 36, El and 38 is connected to a corresponding input terminal of iull wave rectiilers 93, iii and resmctively, by means of leads $6, 9? and 98, while the other input terminal of each of said rectifiers is connected to the other ends or said output coils 36, 3'? and 3% by means of leads at, will and not, respectively.

Thus, it will be seen that the voltage rectified by each of the rectifiers 93, Si and, 95 is the alge braic sum of the reference voltage and the second harmonic voltage of the corresponding one of said output coils 3S, 3'! and 38. These rectified voltages are then supplied to the receiver stator Wlldlngs ll, "i8 and 18, respectively. To this end, the output terminals of rectifier 93 are con-- nected to winding "ill by means of leads $52, M3, resistor iii i and a common lead Hi5 which is con nected to the junction point 8% of all of said 38 acting alone, nor the H2, H3 through resistors H4, H5, H6 and leads H1, H8 and H9, respectively, said direct current voltage bein adjusted to such a value in each of said stator windings as to be equal and opposite to the D. 0. component of the rectified voltage from the corresponding rectifier which results from the rectification of the reference voltage from the frequency doubler 35. This is accomplished by disconnectin the transmitter output coils 36, 31, 38 from the coupling transformer windings 86, 84, 85 so that only the reference voltage is supplied to the rectifiers 93, 94, 95, and adjusting the D. C. voltage until there is no current flow in the receiver stator winding ll, 78, 79. Then the transmitter output coils 38, 37, 38 are re-connected again to the coupling transformer windings 86, 84, 85, thereby causing rectification of the second harmonic voltages from said output coils 36, 31, 38 together with the reference voltage from the frequency doubler 35 to produce a resultant D. C. voltage in each of the receiver stator windings 77, 18, 19 which is a function of the second harmonic voltage of the corresponding one of the output coils 38, 37, 38, respectively. These D. C. voltages then produce a resultant uni-directional field having such an angular direction that when it reacts with the field of the magnet rotor 8!, the latter is rotated to an angular position corresponding to the angular position of the transmitter magnet rotor 4G to actuate the pointer 32 of indicator 83 which then indicates said position.

Novel means are thus provided for transmitting motion from one point to another and remote point, and particularly for transmitting angular motion for indicating and or control purposes, whereby an alternating current type of transmitter may be readily used with adi:ect current type of receiver.

Although three embodiments of' the invention have been specifically illustrated and described, various changes and modifications in the form, construction and relative arrangement of parts and circuits, which will now become apparent to those skilled in the art, may be made without departing from the scope of the invention. Reference is therefore to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In combination, a transmitter of the alter natingcurrent type having an annular core of magnetically permeable material arranged to be traversed by a uni-directional magnetic field for inducing a magnetic flux therein, said core and uni-directional field being relatively angularly movable, an alternating current input winding wound on said core around its circumference, a plurality of equally angularly spaced alternating current output windings wound on said core in inductive relation with said input winding, an alternating current source connected to energize said input winding for periodicall varying the magnetic flux in said core, whereby an alternating voltage is induced in each of said output windings which is an even harmonic of the fundamental frequency of said energizin current and the magnitude of which is a function of the relative angular relation between said core and the unidirectional field, means for combining with each of the vcltages from said output windings a reference alternating voltage having the same frequency as said output voltages, a plurality of rectifying-means for rectifying the combined reference voltage and output voltage from each of said output windings separately, and a direct current type of receiver comprising a stator having a plurality of equally angularly, spaced direct current windings respectively connected to the outputs of saidplurality of rectifying means to produce a resultant uni-directional magnetic field having an angular direction corresponding to the direction of the uni-directional field at the transmitter with respect to the annular core thereof, and a rofir actuated by the resultant field of said receiver stator windings to an angular position corresponding to the angular direction of the unidirectional field at the transmitter.

2. In combination, a transmitter of the alternating current type having an annular core of magnetically permeable material arranged to be traversed by a uni-directional magnetic field for inducing a magnetic flux therein, said core and uni-directional field being relatively angularly movable, an alternating current input winding wound on said cor around its circumference, a plurality of equally angularly spaced alternating current output windings wound on said core in inductive relation with said input winding, an

alternating current source connected to energize said input winding for periodically varying the magnetic flux in said core, whereby an alternating voltage is induced in each or said output windings which is an even harmonic of the fundamental frequency of said energizing current and the magnitude of which is a function of the relative angular relation between said core and the uni-directional field, means for combining with each of the voltages from said output windings a reference alternating voltage having the same frequency as said output voltages, a plurality of rectifying means for rectifying the combined reference voltage and output voltage from each of said output windings separately, and a. direct current type of receiver comprising a stator having a plurality of equall angularly spaced direct current windings respectively connected to the outputs of said plurality of rectifying means to produce a resultant uni-directional magnetic field having an angular direction corresponding to the direction of the uni-directional field at the transmitter with respect to the annular core thereof, a rotor actuated by the resultant field of said receiver stator windings to an angular position corresponding to the angular direction of the uni-directional field at the transmitter, and means actuated by said receiver rotor.

3. In combination, a transmitter of the alternatin current type having an annular core of magnetically permeable material arranged to be traversed by a uni-directional magnetic field for inducing a magnetic flux therein, said core and uni-directional field being relatively angularly movable, an alternating current input winding wound on said core around its circumference, a plurality of equally angularly spaced alternatmg current output windings wound on said core in inductive relation with said input winding, an alternating current source connected to energlee said input winding for periodically varying the magnetic flux in said core. whereby alternatinr; voltage is induced in each of said output windings which is an even harmonic of the fun damental frequency of said energizing current and the magnitude of which is a function of the relative angular relation between said core and the uni-directional field, means for combining with, each of the voltages from said output windlogs releience alternating voltage having the same frequency as said output voltages, a plu rality rectifying means for rectifying the corn cined reference voltage and output voltage from each of said output windings separately, and a direct current type of receiver comprising a sta tor having a plurality of equally angularly spaced direct current windings respectively-connected to the outputs of said plurality of rectifying means to produce a resultant uni-directional magnetic an angular direction cor'esponding ction of the unidirectional field the transmitter. with respect to the annular core thereof, and a rotor providing a unidirectional etic field which reacts with the resultant said rotor to an angular position conr ding to the direction of the uni directional d at the transmitter.

in. combination, a transmitter of alter ing current type comprising a stator having annular of ilnagnetically permeable inaterial provided with an alternating current in tit winding around its circumference and a plu of equally angularly spaced alternating cut output windings in inductive relation with input Winding, a rotor comprising a rotatin magnetic relation with said core and windings for inducing a uni-direetional nus said core, a source of alternating current connected to said input winding for periodically Varyg the unidirectional fiux in said core, whereby an alternating voltage is induced in each of it output windings which is an even harmonic of the frequency of said energizing current and the magnitude of which is a function of the angular position of said magnet rotor with respect to core, means for combining witn each the volt ages from said output windings a ref erence alternating voltage having the same ire" ue cy as output voltages, a plurality of rectifying means for rectifying the combined rci"- erence voltage and output voltage from. each of said output windings separately, and adirect current type of receiver comprising a stator haying plurality of equally angularly spaced direct current windings respectively connected to the outputs of said plurality of rectifying means to produce a resultant uni-directional magnetic field having an angular direction corresponding to the angular position of the transmitter magnet rotor and a receiver rotor actuated by the resultant field of said receiver stator windings to an angular position corresponding to the angular position oi" s ld transmit or rotor.

n combination, a transmitter of the altercurrent type comprising a stator having annular core magnetically permeable maal with an alternating current input winding around its circumference and a plurality of equally angularly spaced alternating current output windings in inductive relation with said input winding, a rotor comprising a rotatable magnet in magnetic relation with said core and windings for inducing a unidirectional flux in core, a source of alternating current con l produced by said receiver stator winding A nected to said input winding for periodically vary ing the uni-directional flux in said core, whereby an alternating voltage is induced in each of said output windings which is an even harmonic of the frequency of said energizing current and the magnitude of which is a function of the angular position of said magnet rotor with respect to said core, means for combining with each of the voltages from said output windings a reference alternating voltage having the same frequency said output voltages, a plurality of rectifying means for rectifying the combined reference volt: age and output voltage from each of said output windings separately, and a direct current type of receiver comprising a stator having a plurality of equally angularly spaced direct current wind ings respectively connected to the outputs of said plurality of rectifying means to produce a resultant uni-directional magnetic field having angular direction corresponding to the angu- Tar position of the transmitter magnet rotor, and a receiver rotor providing a uni-directional netic field which react with the resultant f ld of receiver stator windings to actuate rotor to an angular position co spc ing to the angular position of said ti rotor.

6. In combination, a. transmitter of the alter hating current type comprising a stator having an'annular core of magnetically permeable ma terial provided with an alternating current in,- put winding around its circumference and a plurality of equally angular-1y spaced alternating current output windings in inductive relation with said input winding, a rotor comprising a rotat-= able magnet in magnetic relation with said core and windings for inducing a uni-directional flux"; in said core, a source of alternating current connected to said input winding for periodically vary ing the uni-directional flux in said core. whereby an alternating voltage is induced in each said output windings which is an even harmonic of the frequency of said energizing current and the magnitude of which is a function of the angular position of said magnet rotor with respect to said core, means for combining with each of the voltages from said output windingsa reference al ternating voltage having the same frequency as said output voltages, a plurality of rectifying means for rectifying the combined reference voltage and output voltage from each o1 said output windings separately, and a direct cur rent type of receiver comprising a stator having a plurality oi equally angular-1y spaced direct current windings respectively connected to the outputs of said plurality of rectifying means to pro duce a resultant uni-directional magnetic field having an angular direction corresponding to the angular position of the transmitter magnet rotor, a receiver rotor actuated by the resul" field of said receiver stator windings to an alignlar position corresponding to the angula position of said transn tter rotor, and means actioated by said receiver rotor '7. in combination, a transmitter or the nating current an magnetically permeable material arr? aged travers d by a uni-directional magi field for inducing a magnetic liar: ti'ieit 1 core and uni-directional field being rel larly movable, an alternating current ing wound on said core around its circ l a plurality or equally angularly spac ing current output windings wound on c .l

in inductive relation with inpu 11 an alternating current source connected to energize said input winding for periodically varying the magnetic flux in aid core. whereby an alternating voltage is induced in each of said output windings which is an even harmonic of the fundamental frequency of said energizing current and the magnitude of which is a function of the relative angular relation between said core and the uni-directional field, means for combining with each of the voltages from said output windings a reference alternating voltage having the same frequency as said output voltages, a plurality of rectifying means for rectifying the combined reference voltage and output voltage from each of said output windings separately, and a direct current type of receiver comprising a stator having a plurality of equally angularly spaced direct current windings respectively connected to the outputs of said plurality of rectifying means, a source of direct current connected to energize each of said direct current receiver windings for impressing on each of said windings a direct current voltage which is equal and opposite to the rectified reference voltage in each of said windings whereby only the rectified voltages from the output coils of the transmitter are effective to produce a resultant uni-directional magnetic field having an angular direction corresponding to the direction of the uni-directional field at the transmitter with respect to the annular core thereof, and a rotor actuated by the resultant field of said receiver stator windings to an angular position corresponding to the angular direction of the uni-directional field at the transmitter.

8. In combination, a transmitter of the alternating current type having an annular core of magnetically permeable material arranged to be traversed by a uni-directional magnetic field for inducing a magnetic flux therein, said core and unl-directional field being relatively angularly movable, an alternating current input winding wound on said core around its circumference, a plurality of equally angularly spaced alternating current output windings wound on said core in inductive relation with said input winding, an alternating current source connected to energize said input winding for periodically varying the magnetic flux in said core, whereby an alternating voltage is induced in each of said output windings which is an even harmonic of the fundamental frequency of said energizing current and the magnitude of which is a function of the relative angular relation between said core and the uni-directional field, means for combining with each of the voltages from said output windings a reference alternating voltage having the same frequency as said output voltages, a plurality of rectifying means for rectifying the combined reference voltage and output voltage from each of said output windings separately, and a direct current type of receiver comprising a stator ha ing a plurality of equally angularly spaced direct current windings respectively connected to the outputs of said plurality of rectifying means, a source of direct current connected to energize each of said direct current receiver windings for impressing on each of said windings a direct current voltage which is equal and opposite to the rectified reference voltage in each of said windings whereby only the rectified voltages from the output coils of the transmitter are effective to produce a resultant uni-directional magnetic field having an angular direction corresponding to the direction of the uni-directional field at the transmitter with respect to the annular core thereof, a rotor actuated by the resultant field of said receiver stator windings to an angular position corresponding to the angular direction of the uni-directional field at the transmitter, and means actuated by said receiver rotor.

9. In combination, a transmitter of the alterhating current type comprising a stator having an annular core of magnetically permeable material provided with an alternating current input winding around its circumference and a plurality of equally angularly spaced alternating current output windings in inductive relation with said input winding, a rotor comprising a rotatable magnet in magnetic relation with said core and windings for inducing a uni-directional flux in said core, a source of alternating current connected to said input winding for periodically varying the uni-directional flux in said core, whereby an alternating voltage is induced in each of said output windings which is an even harmonic of the frequency of said energizing current and the magnitude of which is a function of the angular position of said magnet rotor with respect to said core, means for combining with each of the voltages from said output windings a reference alternating voltage having the same frequency as said output voltages, a plu ality of rectifying means for rectifying the combined reference voltage and output voltage from each of said output windings separately, and a direct current type of receiver comprising a stator having a plurality of equally angularly spaced direct current windings respectively connected to the outputs of said plurality of rectifying 'means for energization by said rectified voltages, and a source of direct current for additionally energizing said direct current receiver stator windings for impressing on each of said windings a direct current voltage which is equal and opposite to the rectified reference voltage component in each of said windings, whereby only the rectified voltages from the output windings of said transmitter are efl'ective to produce a resultant uni-directional magnetic field having an angular direction corresponding to the angular position of the transmitter rotor, and a receiver rotor actuated by the resultant field of said receiver stator windings to an angular position corresponding to the angular position of said transmitter rotor.

10. In combination, a transmitter of the alterhatin current type comprisin a stator having an annular core of magnetically permeable material provided with an alternating current input winding around its circumference and a plurality of equally angularly spaced alternating current output windings in inductive relation with said input winding, a rotor comprising a rotatable magnet in magnetic relation with said core and windings for inducin a uni-directional flux in said core, a source of alternating current connected to said input winding for periodically varyin the uni-directional flux in said core, whereby an alternating voltage is induced in each of said output windings which is an even harmonic of the frequency of said energizing current and the magnitude of which is a function of the angular position of said magnet rotor with respect to said core, means for combining with each of the voltages from said output windings a reference alternating voltage having the same frequency as said output voltages, a plurality of rectifying means for rectifying the combined reference voltage and output voltage from each of said output windings separately, and a direct ourrent type oi receiver comprising a stator having a plurality of equally angularly spaced direct current windings respectively connected to the outputs of said plurality of rectifying means for energization by said rectified voltages, and a source of direct current for additionally energizing said direct current receiver stator windings for impressing on each of said windings a direct current voltage which is equal and opposite to the rectified reference voltage component in each of said windings, whereby only the rectified voltages from the output windings of said transmitter are effective to produce a resultant uni-directional magnetic field having an angular direction corresponding to the angular position of the transmitter rotor, and a. receiver rotor providing a unidirectional magneticfield which reacts with the resultant field of said receiver stator windings to actuate said receiver rotor to an angular position corresponding to the angular position of said transmitter rotor.

11. In combination, a transmitter of the alternating current type comprising a stator having an annular core of magnetically permeable material provided with an alternating current input winding around its circumference and a plurality of equally angularly spaced alternating current output windings in inductive relation with said input winding, a rotor comprising a rotatab e magnet in magnetic relation with said core and windings for inducing a uni-directional flux in said core, a source of alternating current connected to said input winding for periodically varying the unidirectional flux in said core, whereby an alternating voltage is induced in each of said output windings which is an even harmonic of the frequency of said energizing current and the magnitude of which is a function of the angular position of said magnet rotor with respect to said core. a plurality of pairs of rectifiers, the number ofpairs of rectifiers corresponding to the number of output windings, means for COmbinlng in each pair of rectifiers each of the voltages from said output windings with a reference alternating voltage having the same frequency as said output voltages, whereby the rectified output voltage from one of each pair of said rectifiers is the sum of the rectified reference voltage and the rectified output voltage, and the rectified output voltage of the other of each pair of rectifiers is the difference between the rectified reference voltage and the rectified output voltage, and a direct current type of receiver having a plurality of pairs of direct current stator windings, the number 01' pairs of said windings corresponding to the number of pairs of rectifiers, and said pairs of windings being equally angularly spaced, means connecting one of each pair of said stator windings to the output of a corresponding one of said pairs of rectifiers, means connecting the other of each of said pairs of windings to the output of the corresponding other one of said pairs of rectiflers, whereby said pairs of stator windings produce a resultant uni-directional magnetic field having an angular direction corresponding to the angular position of a transmitter rotor, and a receiver rotor actuated by the resultant field of said receiver stator windings to an angular position corresponding to the angular position 01' said transmitter rotor.

12. In combination, a transmitter of the alternating current type comprising a stator having an annular core of magnetically permeable material provided with an alternating current input winding around its circumference and a plurality of equally angulariy spaced alternating current output windings in inductive relation with said input winding, a rotor comprising a rotatable magnet in magnetic relation with said core and 5 windings for inducing a uni-directional flux in said core, a source of alternating current connected to said input winding for periodically varying the uni-directional flux in said core, whereby an alternating voltage is induced in each of said output windings which is an even harmonic of the frequency of said energizing current and the magnitude of which is a function of the angular position of said magnet rotor with respect to said core, a plurality of pairs of rectifiers, the numher of pairs of rectifiers corresponding to the number of output windings, means for combining in each pair of rectifiers each of the voltages from said output windings with a reference alter nating voltage having the samefrequency as said output voltages, whereby the rectified output voltage from one of each pair of said rectifiers is the sum of the rectified reference voltage and the rectified output voltage, and the rectified output voltage of the other of each pair of rectifiers is the difference between the rectified reference voltage and the rectified output voltage, and a direct current type of receiver having a plurality of pairs of direct current stator windings, the number of pairs of said windings corresponding to the 0 number of pairs of rectifiers, andsaid pairs of windings being equally angularly spaced, means connecting one of each pair of said stator windings to the output of a corresponding one of said pairs of rectifiers, means connecting the other of each of said pairs of windings to the output of the corresponding other one of said pairs of rectiflers, whereby said pairs of stator windings produce a resultant uni-directional magnetic field having an angular direction corresponding to the angular position of a transmitter rotor, a receiver rotor actuated by th resultant field of said ducing a magnetic flux therein, said core means and uni-directional magnetic field being relatively angularly movable, coil means wound on said core means and having single circuit input connections and a plurality of equally angularly 5 spaced output connections about said core means,

a source of periodically varying current connected to energize the input of said coil means for periodically varyin the magnetic flux in said core means, whereby an alternating Voltage is induced O'in each of the outputs of said coil means, having a magnitude which is a function of the relative angular relation between said core means and the uni-directional magnetic field, means for combining with each 0! said output voltages a periodically varying reference voltage having the same frequency of variation as said output voltages, a plurality of rectifying means for rectifying the combined reference voltage and output voltage from each of said outputs separately, and a direct current type of receiver comprising a stator having a plurality of equally angularly spaced direct current windings respectively connected to the outputs of said plurality of rectifying means to produce a resultant uni-directional magnetic field having an angular direction corresponding to the direction oi the uni-directional magnetic field at the transmitter with respect to the core means thereof, and a receiver rotor actuated by the resultant magnetic field of said receiver stator windings to an angular position. corresponding to the direction of the uni-directional field at the transmitter.

JOEL D. PETERSON.

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