Jan. 14, 1947. H, |_. HULL ET Al. I 2,414,102 HANDLE CONTROL SYSTEM _ Filed July 23, 1941 F n œ. C E; 55 59 reaA/SM/rrffs 4B y „f/oro@ HH/VDL E F i ET . 4 Sheets-Sheet l Jan. 14, 1947. 2,414,102 H. L. HULL ET AL HANDLE CONTROL SYSTEM Filed July 23,> 1941 4 Sheets-Sheet 2 F' I E-„ßY TIME OF gg AMPLn-ms IIB" | , IZOI ,2g I I IZI PREDICTION POTENTIOME TER " Ñ., RATE AMPLlFlER ‘ °<_'] `H7 |09 °//--m _ (t \\ H3 OTHER \l l5 PREDICTION voLTAGEs ' INVENTURS HARVARD L. HULL WILLIAM C. HARTMAN RAYMOND C. GOERTZ aww/M“ T EIR ATTOR EY Jam 14, 1947' H. |_. HULL ETAL 2,414,102 HANDLE CONTROL»~ SYSTEM Filed July 2s, 1941 4 sheets-sheet s A.c.AMP|_|F|ER AND PHASE s IF ER 6 ò MODULATOR D’C» ‘1, AMPLIFIE ` ' -f [5.c.AMF‘LlFlL-RoJ MoDuLAToR AND A.c.AMpl_|F|ER n n 59 WAVE o MoDULATo o l / |79 ' ` ï '3 ` '57 16| INVENToRs HARVARD L. HULL WILLIAM C. HARTMAN RAYMOND C. GOERTZ „7mm/.M THE! R ATTORNEY Jan. 14, 1947. H. L. HULL Erm. 2,414,102 HANDLE CQNTROL SYSTEM Filed July 23, 1941 4 sheets-sheet 4' „V277 ' D.c.ouTPuT V 273 mveNroRs HARVARD L.HuLL WILLIAM C. HARTMAN RAYMOND c. GpeRTz BY THE l R ATTORNEY îïatented Jan. 14, 1947 2,414,102 HANDLE CONTROL SYSTEM Harvard L. Hull, Garden City, William C. Hart man, Bohemia, and Raymond C. Goertz, Hemp stead, N. Y., assignors to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a corporation of New York Application July 23, 1941, Serial No. 403,618 23 Claims. (ci. :is-49) E . The present invention relates, generally, to ñre control apparatus, and has reference, more par ticularly, to sights for gun directors, in which a> telescope sight is continuously trained on a target, thereby enabling the production and trans mitting of data to cause a gun to be aimed at the target. In previous devices of this type, control has . been obtained by means of a handwheel, whose motion had to be synchronized with motion of the telescope. Also, separate controls for azimuth and elevation were used. These devices were quite satisfactory for low tracking rates. How It is also an object o the invention to pro vide an improved control unit for precise and steady tracking control. It is a further object to provide an improved control circuit for controlling the tracking veloc ity of a sight in both azimuth and elevation by manipulation of a single control handle. It is an additional object to provide improved means for effecting velocity control or combined velocity and acceleration control of a. tracking system, at the will oi the operator. It is another object to provide an improved circuit and mechanism for compensating the gun ever, with high tracking rates, such as are nec directing data obtained by the tracking system essary in close-in aerial combat, proper syn 15 for any desired prediction data. chronization of controls and telescope becomes It is still a further object to provide an im diftlcult and it is not possible to obtain satisfactory proved modulator circuit for converting direct _ control so as to be able to readily and rapidly voltages into alternating voltages whose phase manipulate the controls to cause the telescope and magnitude correspond to the polarity and to track with the course of fast moving targets, 20 magnitude of the direct voltages, for use in track and still be steady and precise in operation so ing control. that a target once sighted may be continuously It is an additional object to provide an im followed with ease and accuracy and smooth rates proved demodulator circuit for converting alter obtained for prediction purposes. . nating voltages into direct voltages whose polarity The present invention provides a device which 25 and magnitude correspond to the phase and mag minimizes the difiiculties of prior devices. A nitude of the alternating voltages, for use in tracking control system is provided in which the tracking control. velocity of the sight is controlled by natural and Other objects and advantages of this inven instinctive movements of a `single control handle tion will become apparent as the description pro controlling both azimuth and elevation movement 30 ceeds. of the sight, and whose operation simulates di In the drawings, rect manual control of the sight. Precision and Fig. l shows in schematic perspective view the steadiness of operation are provided in the type mechanical arrangement of the tracking and pre of control unit used, in which the operator can diction control; ñrmly grasp a reference knob, which is fixed with 35 Fig. 2 shows a longitudinal cross-section of the respect to the sight, with part of his hand and signal pick-up or control unit used in the device the control handle with the rest of the same hand. of Fig. 1; This provides a steadying influence on the control Fig. 3 shows schematically the circuit diagram process, so that extremely ñne control is possible. of an alternating-current-operated control cir The control handle is made fairly stili in opera 40 cuit for the device of Fig. 1; tion, by a cantilever type mounting, making con Fig. 4 shows schematically an alternative di trol mainly by pressure rather than by deiiection. rect-current-operated control circuit for the de In addition, the present system permits complete vice of Fig. 1, including acceleration control; control with one hand, leaving the operator’s Fig. 5 shows a detailed circuit of a push-pull other hand free for other duty. 45 modulator circuit suitable for use with the circuit A further feature of the device resides in a 0f Fig. 4; and switching arrangement whereby the velocity con Fig. 6 shows the detailed circuit of a full-wave ,trol may be converted to a combined velocity phase-sensitive demodulator suitable for use with and acceleration control which, under some cir the circuit of Fig. 4. ` cumstances, will give constant velocity tracking 60 Similar characters of reference are used in all Without any action by the operator, whereby tracking on a target is maintained automatically at a fixed speed. Also, means are provided for of the above figures to indicate corresponding parts. Fig. 1 shows the mechanical arrangement of the various elements of the system. The tele compensating the data obtained from the track ing sight for any desired prediction data, and 55 scope tracking sight I is mounted for rotation in for transmittingthe compensated data to a re azimuth, as by means of vertical shaft 3, and is mote point to control the directing of a gun. Accordingly, it is an object of the present in vention to provide a new and improved tracking control system for sights and gun directors. pivoted about a horizontal axis 2 for rotation in elevation. Horizontal shaft 5 is rotatably mount ed on shaft 3 as by a, yoke 4 and is positioned t0 parallel to the horizontal axis 2 of sight l. Shaft 2,414,102 5 is linked to sight I as by a linkage 1, 8. so that sight I is -rnoved in elevation in synchronism with s rotation of shaft 5. Control unit 9, shown in de tail in Fig. 2, is fixed to shaft 5 with its control handle II parallel to sight I. Hence, the control unit 9 is relatively fixed with respect to sight I and always remains parallel to sight I, turning with sight I both in elevation and azimuth. This gives the operator the sense of actually manually 4 and/or gun in elevation and azimuth. Similar elements are given the same reference numbers, but primed. 9. Fig. 2 shows a cross-section of the control unit 'I‘his control unit 9 has four symmetric mag netic circuits disposed radially about the longitu dinal axis 42 of the unit, only two such circuits being shown in the cross-section taken. 'I'hese circuits have a common portion 4I formed as a operating the sight I, by manipulation of control 10 sleeve concentric with axis 42. Extending radl handle II, since the sight appears to respond to his natural movements in effecting tracking, al though actually the control handle II merely controls the sight ‘driving mechanism, as de ally from sleeve 4I are four core members, only two of whlchv(43, 45) are shown. These core members 43, 45 have bent over arms or portions 41, 49 parallel to axis 42. These arms are ter 15 minated by slanted portions.“ which are prefer scribed below. ably formed to comprise a portion of the surface The control handle II and its related parts are of a sphere having its center approximately at so shaped and formed as to provide easy and point C. The magnetic circuits are completed by natural manipulation by the operator. For this a button 5I having a spherical surface which co purpose, referring to Fig. 2, casing 55 has fas operates with the spherical-shaped ends 48 of tened to it a stabilizing or reference knob 50, arms 41, 49 to form a uniform air gap between placed concentric and adjacent to handle- I I. button 5I and each of the arms~41, 49. It is to Knob 5I) is shaped to be gripped by the thumb be understood that each of the two arms not and fore part of the hand of the operator. This shown is formed in exactly the same manner, but knob 50 is relatively short in length, so that the rear or heel portion of the hand of the operator 25 disposed in a plane perpendicular to the plane of the figure. will at the same time be able to grip the handle Button 5I is rigidly fastened to handle II as II. The control circuit described below is de by rod 53, and is resiliently fastened to case 55 signed to give full speed control for a relatively by member 51 whose end 6I is rigidly held to small displacement of control handle Il, which case 55, as by set screws 63, and which has a may be on the order of 1/8 inch for full displace reduced resilient bending section 59. The han ment. Accordingly, by this deviceLthe operator dle and button assembly is adjusted so as to be is given a fixed reference object by which to gage normally coaxial with axis 42, but may be de the pressure (or deflection) to be placed on the iiected in any radial direction by a transverse control handle, while maintaining a. firm grasp and positive control of the control handle. The 35 pressure on handle II. The button 5I is thus mounted in cantilever fashion, all bending taking effect is to enable extremely accurate and steady place approximately at the center C of the re control with a minimum of operator effort. The duced diameter bending section 59. The motion complete operation is made natural, enabling in of button 5I approximately follows the surface stinctive reaction to changing conditions needing control adjustment on the part of the operator. 40 of a sphere having its center at point C, which is at the center of bending section 59. Because Referring again to Fig. 1, also fastened to hori of this cantilever action, the deflection of the con zontal shaft 5 is a gear I3 driven by driving gear trol handle I I is closely proportional to the pres I5 which in turn is driven by drive motor I1. sure applied to it. Since the tracking velocity of Speed generator I9, whose function is described below, is also driven directly by drive motor I1. 45 sight I may also be proportional to the deflection of handle II, it will, in such case, be proportional The drive motor I1 thereby rotates shaft 5, and to applied pressure. Hence, the operator gets a controls the elevation of sight I at a speed which realistic “feel” of the operation, and can readily may be proportional to the deflection of, or pres imagine that his own effort is controlling the sure on, control handle II, as will be described sight directly. This makes it easier for the oper below. Strict proportionality need not be fol ator to accurately perform the required tracking. lowed in all cases. For example, it may be desir Placed about sleeve 4I is an energizing coi-l able to give relatively broad and insensitive con 65, which is fed from a suitable source of alter-v trol near the neutral axis of the control unit, and nating current. Around each arm, as for exam relatively sharp and sensitive control at larger ple arms 41, 49, there is wound a pick-up coil. velocities. Also connected lto shaft 5 is a differential 2I . Two such coils 61, 59 are shown. The entire device is made symmetrical about axis 42, so that connected in turn to further shafts 23 and 25. Shaft 25 is positioned by prediction motor 21 which also drives prediction potentiometer 29. equal voltages of equal phase will be induced in each pick-up coil when button 5I is coaxial Shaft 23 drives a “coarse” self-synchonous trans with axis 42. Each pair of diametrically oppo mitter 3| directly, and a “fine” self-synchronous 60 site coils is connected in series in opposing relatransmitter 33 through suitable gearing 35. The ’ non, so that, when button 5| is in its undenected outputs of these transmitters 3| and 33 may go position, coaxial with axis 42, thereby making all to control the elevation of a remotely situated gun four magnetic circuits identical, no resultant (not shown) ,which will then be directed (at least voltage is produced from each pair of pick-up 65 in elevation) toward the target being sighted by coils, since the voltage induced in any one coil telescope I. Prediction motor 21 and diñerential is opposed and cancelled by that of its diametri 2|, cause the shaft 23 to lead or lag the shaft cally opposite coil. / 5 by an angle corresponding to any corrections When handle II is deflected, for example, ver necessary to cause the gun to be directed toward tically downward, the air gaps between button the future position of the target. Such correc 70 5I and arms 41, 49 will remain of the same tions may allow for time of night of the projec length, since button 5I will pivot about its ap tile, super-elevation, wind, air density, etc. proximate center of curvature C; however, the Shaft 3 is driven in azimuth by exactly the cross-sectional varea of the gap at arm 41 will same type of system, through a coupling gear 31'. 75 decrease, increasing the reluctance of its mag thereby giving complete control of the sight 2,414,102 netic circuit, and the area. at arm t9 will increase, reducing the reluctance of its circuit. Hence j when its winding 99 is energized and its rotor is turned, will generate voltages in its two-phase winding which, when added, will be closely pro portional to the speed of rotation. Alternatively, more voltage will be induced in coil 69 than in coil B1, and there will be a net voltage output, indicating deflection along the vertical direction'. 5 this generator may take the form shown in Riggs No voltagewill appear across the other pair of Patent 2,206,920, issued July 9, 1940. Winding 89 coils. in this instance, however, since their mag Iis energized from supply line 13 through an ad netic circuits remain balanced. For deflection justable phase shifting circuit 91. The wind upward, the opposite will occur, and the output ings 9I , 93 are connected in series across a. poten voltage will be of opposite phase from that of 10 tiometer 99 whose movable tap I0| is connected the case first considered. For any other direc to the junction of the two-phase windings 9|, tion of deflection a component of voltage will 93. This tap I 0| is adjusted so that at stand appear across each pair of coils which will be still there is zero voltage output. A condenser proportional in magnitude to the component of |00 is connected across windings 9|, 93 to iilter deflection along the axis of that pair of coils, and l5 out undesired harmonics. The output of the will have a phase corresponding to the sense of the corresponding component of deflection. The unit is mounted so that one pair of coils has a speed generator I9 is connected to oppose or buck the control voltage produced in the control unit 9. Thus, the speed generator I9 and the out vertical axis perpendicular to shaft 2 and the put of control unit 9 are connected in series oppo other a horizontal axis perpendicular to shaft 3. 20 sition across the primary of transformer 19.. The Then the control signal output of the vertical phase adjustor 91 is used to assure that the volt pair of coils is used to control the elevation of age output of speed generator I9 is exactly in the sight I and the output of the horizontal pair phase opposition to the control voltage obtained is used to control azimuth. as will be described from control unit 9. Accordingly, it is substan below. 25 tially the arithmetic difference between these two Fig. 3 shows the circuit diagram for alternating voltages which operates the motor I1. The magnitude of the voltage input to ampli ñer 83 needed to operate motor I1 at its full torque and speed is made very small compared to of control unit 9 is energized from a source 13 30 the voltage generated either by the speed genera of alternating current by means of a current tor or the control unit. The ampliñer 83 is ad limiting resistor 15 which minimizes saturation v«justed to saturate at this small voltage; that is, eiîects. The two oppositely positioned pick-up any voltage greater than this predetermined small coils t1, 09 are connected in series opposition voltage is ineñective to increase the amplifier out and are shunted by a condenser 11 whose func 35 put voltage, which remains at the motor full speed tion is to bypass the harmonics created by satura voltage. Of course, any amplifier input voltage tion of the edges of button 5I. This condenser smaller than the saturating voltage will yield an ‘l1 may tune the output coils 61, 69 to resonance output voltage less than the motor full speed volt at line frequency. The voltage output from con age. and the motor will rotate at less than full trol unit 9 is then an alternating voltage of sup 40 speed. As an illustrative example, the full-speed ply line frequency having an amplitude propor generator output, and the full deñection control tional to the deflection of control handle II (in voltage, may be about 30 volts, while the ampli~ elevation or azimuth) and a phase corresponding fier saturating voltage may be about 0.3 volt. current control in one plane, either in azimuth or elevation, the same circuit being duplicated for the other plane'. The energizing coil 65 to the sense of the deflection. This control volt In operation, starting from a standstill, the con age is applied over coupling transformer 19 and 45 trol handle II may be partially deflected, for ex conventional phase shifter 8| to amplifier 83, which amplifies the control voltage and applies it to one winding 85 of the two phase drive motor I1, the other winding 81 being connected directly ample, to give a control voltage of 20 volts. Since at this instant the speed generator I 9 is at stand Since the control voltage will reverse phase upon at maximum rate. `Acceleration will continue un til the generator output differs from the con still, ithis control voltage is unopposed and is fully applied to the ampliñer. However, due to the 4 to the supply line 13. Phase shifter 8| assures 50 saturation effect in amplifier 83, only 0.3 volt is that the voltage `applied to winding 85 is in effective, which applies full starting torque to the quadrature with that applied to Winding 81. motor, which therefore immediately accelerates i reversal of the control handle displacement, it »will be seen that the direction of rotation of 55 trol Voltage only by sumcient- voltage diñerence L. drive motor I1 will also reverse, and will accord to maintain motor speed sufficient to yield that a ; `lngly .correspond at all times to the direction of ‘ deflection of the control handle Il. The direc- . generator output. Since the voltage difference will be less than 0.3 volt, in the example used, it tion of rotation is selected so that downward pres will be seen that the generator output voltage sureon handle II will drive the handle down 60 will be substantially equal to the control voltage, ward,- `thereby giving a realistic type of opera-and, therefore, the motor speed. which provides 1 tion.` the tracking velocity, is substantially proportion In order to assure that the speed of rotation of al to the control voltage, and hence to the pres drive motor I1 will be proportional to the deflec sure (or deflection) applied to the control handle tion of control handle II, when this condition 35 II. Rheostat |03 is used to adjust the generator is desired, speed generator I9 is directly driven voltage to the proper value, by drive motor I1. This speed generator is de The function of 'prediction motor 21 is to posi signed to have an alternating voltage output tion shaft 25 in accordance with certain predic directly proportional toits speed. In one illus tion data. whereby the signals transmitted by trative ‘embodiment this generator may take the synchro-transmitters 3 I, 33 will correspond to the form of a Barber-Colman #412 reversible alter position of the target at the future instant of im nating current motor. This motor has an ener pact by the projectile. The prediction data to be gizing winding 89 and a two-phase winding 9| , allowed for may include time of ñight of the pro 93, all iixed. The rotor 95 is of the squirrel cage jectile, super-elevation, wind velocity, air density, 'type It has been discovered that such a motor, etc. 2,414,102 The actual time of night t is determined by the range and altitude of the target. If the sight, and _therefore the gun, is tracking at an angular ve locity w, _then the angular lead necessary to com pensate the gun for time of night t will be at. Since the speed generator I9 rotates at a speed proportional to the tracking speed, its output 8 tentiometer 29 is wound linearly (that is, with constant resistance per unit length) the angle be tween point |20 and arm |2| will then be exact ly proportional to the total prediction volta ze. This angle is also the angle through which shaft 25, and hence differential 2|, has turned. Ac cordingly, the prediction voltage is thus trans formed into the required lead angle, and the posi voltage will be proportional to u. In order to ob tion transmitted by synchro-transmitters 3|, 33 tain a voltage proportional to wt, we use a poten tiometer |05 connected across the output of the 10 will be compensated for the required prediction speed generator. The full generator voltage is data. ' It is obvious that any change in-any of the assumed to correspond to maximum time of night. prediction voltages will cause an immediate and This determines the proportionality factor be corresponding change in the position of the pre tween the voltage corresponding to the lead angle and the time of night. For-any other time of 15 diction motor, so that the correct lead angle 1s night, the tap |01 ofv potentiometer |05 is adjusted always set intodinerential 2|. so that only a fraction of the vgenerator voltage, equal to the actual time of night divided by max imum time of night, is effective. In this way, a Lead ||9 may be connected directly to center point |20 of prediction potentiometer 29. instead of to center point |I9 of transformer III, as voltage proportional to wt is obtained and the 20 shown in Fig. 3, without changing the operation proportionality is maintained both for varying of the device. angular velocities of sight I and for varying times Fig. 4 shows an alternative control circuit for ' of night. This voltage across the effective por- . the device of Fig. l, using unidirectional control , tion of potentiometer |05 is connected in series and prediction voltages instead of alternating with other prediction voltages, connected to ter 25 voltages as in Fig. 3. The method of operation minals |09. which represent the other factors to is quite similar. be’compensated for. These other prediction volt Defiection of, or pressure on, control handle || ages may be obtained in any suitable manner. generates alternating control voltages in pick-up Of course, each of these other prediction voltages coils 61, 69. These voltages are rectified in full is made proportional to its required lead angle 30 wave rectifiers |21, |29 and are then connected by the same proportionality factor as used for time of flight prediction. Hence, the total volt age represents, with a proportionality factor, the total lead angle necessary. Fig. 3 shows the means for positioning prediction motor 21 at this total lead angle in response to the prediction voltages. in series opposing relation. The dotted arrows near coils 61, 69 indicate the relative polarities of the voltages induced in the coils 61, 69. In place of rectiiiers |21, |29, any phase-sensitive rectiner or demodulator may be used. The coils 61, 69 are connected in series opposition to form the input of such a demodulator. A suitable de Prediction motor 21 is mechanically coupled as modulator circuit is shown in Fig. 6. by shaft 25 to prediction potentiometer 29. This The resultant direct voltage from the rectiners potentiometer 29 is connected across transformer 40 |21, |29 (or -demodulator of Fig. 6) is applied to I | I, which in turn is energized by current of line the input of D. C. amplifier I3I, wherein it is am frequency from source 13. A rate amplifier I I3, which may be of any well known type which yields an output voltage con plified. The output of D. C. amplifier |3| is con nected in series bucking relationship to the out of speed generator I9', whose function and taining time derivative components of the input 45 put operation is the same as that of speed generator voltage, of the first and/or higher orders, as well I9 in Fig. 3. However, generator I9' is a D. C. as amplified input components, has one input ter generator, either with a permanent magnet field minal ||5 connected to terminal `I0!! of the pre or a field winding, energized by direct current, as diction voltage input. The other terminal |09 is connected to one terminal |01 of the time of night 50 will be described. Of course, the voltage ouput of generator I9’ must be directly proportional to potentiometer |05, whose other terminal |06 is ' connected by lead ||0 to the center tap I I9 of the secondary of transformer III. The other input terminal ||1 of rate amplifier ||3 ls connected to the movable arm I2| o'f the prediction poten tiometer 29. .The output of the rate amplifier I I3 its speed. ‘ The combined direct control and speed gener ator voltages are applied to modulator |35, which transforms the applied direct voltage into an al ternating voltage of proportional amplitude, and of a phase corresponding to the polarity of the in put. That is, the A. C. output voltage of modu lator |35 reverses phase when the D. C. input ergized directly from the supply line 13. Rate amplifier ||3 may include any phase shifting cir 60 voltage reverses polarity. Fig. 5 shows a suitable circuit which may be used as such a modulator. cuits needed to insure phase quadrature between The operation of this circuit will be later ex the voltages supplied to windings |23, |25 of motor is connected to one winding |23 of two-phase pre diction motor 21, whose other winding |25 is en 21. ’ When arm |2| of potentiometer 29 is at its plained. Y The output of modulator |35 will be an alter` center point |20, the voltage difference between 65 nating voltage whose phase corresponds to the di rection of denection of control handle II and points |20 and ||9 is zero, and the only voltage whose amplitude is proportional to the ampli applied to the input IIS, ||1 of rate ampliner ||3 tude of the control handle denection. It will be is the total prediction voltage. This voltage, op understood that certain cases may require that erating through rate ampliner H3, will cause pre diction motor 21 and potentiometer arm |2| to 70 this proportionality be not strictly observed. Any suitable relationship may be used. This out turn until the voltage between center point |20 put is fed into an'A. C. amplifier and phase shifter and the new position of arm |2| of potentiometer 0|, 83 similar to that in Fig. 3, whose output con 29 is equal and opposite to the prediction voltage, trols drive motor I1 as described above. 'Phase whereupon the input to ampliner I|9 becomes zero and the prediction motor stops. Since po~ 75 shifter 8| insures that the energization of field 2,414,102 winding 85 of drive motor | 1 is ln quadrature with that of field winding 81. Incorporated in the input circuit of modulator preached. The only way in which the voltage drop across resistor |48 can be maintained equal to that across the effective part of potentiometer |35 is the integrating circuit |31 for eñ’ecting ve |53 is for the generator to continually increase velocity to maintain constant charging current. Hence control handle || becomes an acceleration locity plus acceleration tracking control. This circuit comprises a potentiometer |39 connected across the speed generator output and having a control in addition to a velocity control, as it is movable arm |4| connected through a resistor with the switches |43, |45, |5| in their voriginal |42 to the ñxed contact of a single-pole single position. throw switch |43. Connected across the two 10 From another point of view, the generator fixed contacts of a single-pole double-throw voltage V must be equal to the sum of the voltage switch |45 is a condenser |41. One terminal of drop across resistor |49 and condenser |41. That this condenser |41 is connected to a terminal of 1s, the speed generator |9’, while the other terminal is connected to the movable contact of switch |43. (I) ’l'he movable contact of switch |45 is connected to one output terminal of D. C. ampliñer |3| and where R is the resistance of resistor |49, c is also to a resistor |49 whose other side is con the capacitance of condenser |41 and i i's the cur nected to the input terminal |38 of modulator I 35. rent ñowing in the circuit. It is clear that V is Resistor |49 is selected to have a high value of 20 proportional to the tracking speed s. Also, the resistance, and to give a large time constant with drive motor circuit causes the drop across re condenser |41. A potentiometer |53 is connected sistor |49 to be maintained practically equal to across the output of D. C. amplifier | 3|, and a the control voltage, which is proportional to de switch |5| can selectively connect the input ter flectìon D of control handle ||. Hence, iR is pro minal |35 of modulator |35 to either the movable 25 portional to D, or i is proportional to D. Neglect arm |55 or the fixed terminal |56 of potentiometer ing proportionality constants, the above equation |53. The three switches |5i, |43, |45 are me may be transformed into chanically ganged so as to be operated simul taneously. In the switch position shown in Fig. 4, the cir cuit will operate with straight velocity tracking; ‘that is. theV drive motor velocity will be propor tional or will at least correspond to the control handle deflection, as described above. In this position, condenser |41 is charged through cur rent limiting resistor |42 to a voltage somewhat less than the generator voltage, by means of the potentiometer |35. The time constant of the charging circuit |42, |41 is made small so that 30 This last equation shows that the tracking con trol has both a velocity and an acceleration com ponent. That is, a constant deflection D will give a certain constant component of tracking velocity, as shown by the first term of _the right side of the equation, and in addition will give a constantly increasing tracking velocity compo nent due to the integrating eiîect of the second term. Hence the control handle becomes both the condenser voltage will closely follow changes 40 a velocity and an acceleration control. If the control handle |I is released, so that zero in generator voltage. The charging voltage de voltage appears across potentiometer |53, the pends on the position of arm |4| of potentiom motor will drop its speed until the generator volt eter |33’. ' i age output equals the condenser voltage. There When switches |43 and |45 are switched to after the motor will travel at constant velocity; their other positions, the voltage across condenser 45 if the velocity should change, charging or dis |41 is placed in opposition to the generator volt charging current from condenser |41 will flow age, across resistor |49. The voltage across this through resistor |49, whose voltage drop will con resistor |49 will be the generator voltage less the trol the motor to restore its speed. 'I'he drive condenser voltage. This difference voltage will motor can be made to slow down only by revers be much less than the voltage across potentiom 50 ing the deflection of the control handle, which eter |53, which at the Amoment of switching was therefore acts again as an acceleration control. substantially equal to the generator voltage. In With zero control voltage, D becomes zero, so order to prevent abrupt speed change of drive mo that the iirst term of the equation disappears, tor Il due to the excess of the voltage across po leaving only the integration term. Hence, S will tentiometer |53 over the voltage across resistor be maintained constant at the value of the in |49, switch |5| is actuated simultaneously with tegrated term. switches |43 and |45, and acts to reduce the The importance of the combined velocity and effective voltage output of D. C. amplifier |3| to a acceleration control arises from the methods used value nearer the difference voltage. in tracking. When an object is sighted, it is de Since the generator output voltage is greater sirable to accelerate the sight to overtake the ob» than the charged condenser |41 voltage, the gen ject, and then keep it trained on the object. The erator i9’ will tend to further charge condenser present device permits such operation. Accelera |41, through resistor | 49. The voltage drop across tion is provided by control handle deflection, resistor |49 produced by this charging current whereby the object may be overtaken, then re must be substantially equal and opposite to the lease of the handle || will permit the sight | to voltage across the effective part of potentiometer continue tracking at constant velocity. |53; otherwise, the drive motor |1 will speed up A further advantage arises where the sight may or slow down so as to make the drop across re be tracking by itself at the proper velocity, but sistor |49 have a value equal to that across po behind the object. Then deflection of the con tentiometer |53. If control handle || is held in trol handle will apply enough additional tracking constant deflected position,~ a constant voltage velocity, by the first term of the last equation, to „ will be developed across potentiometer |53. How enable the sight to overtake the object. Then re ever, the voltage drop across resistor |49 will lease of the handle will permit the sight to re tend to decrease, since the charging current of sume practically the same tracking velocity as condenser |41 will decrease as full charge is ap 75 before, since the integration term of the equation 2,414,102 ll winding of speed generator |9' when an electro magnet field is used for that generator. In this way, since all the prediction circuit voltages are derived from the same source, namely, source 13, any iiuctuation in source voltage will have equal proportional effect on all voltages, so that the will be little affected by the brief period of in crease'i velocity. v Another useful method of operation is to use straight velocity tracking until the object is sighted. Then throwing the ganged switch of Fig. 4 to its other position will automatically continue the same tracking velocity, with the control handle at neutral. Fig. 4 also shows a D. C. operated prediction control circuit which is quite similar to the pre 10 circuit as a whole is independent of source volt age ñuctuations. This arises from the fact that the balancing voltage from potentiometer 29 varies in the same way as the prediction volt ages, upon any change in supply voltage. As in Fig. 3, potentiometer 29 is rotated until diction voltage, which is proportional to the cor .the voltage between its arm and its center point rection angle needed for time~oi-flight correc balances the total prediction voltage. This is tion, is derived as in Fig. 3 from time-of-ilight potentiometer |05 connected across the output of 16 done by connecting the total prediction voltage and the potentiometer voltage in opposition speed generator i9'. This voltage is now a direct across the input of~ device |19, which includes a voltage since the speed generator output is a direct " diction circuit of Fig. 3. The time-of-ñight pre- , D.-C. ampliller, a modulator which converts re voltage. The other- prediction voltages may be obtained from a transformer |51 whose primary |59 is en versible polarity D.-C. into reversing phase A.-C., 20 and an A.-C, amplifier. The modulator may be of the type shown in Fig. 5. Either or both the D.-C. and A.-C. amplifier may include rate cir cuits for insuring dead-beat and anti-hunting op eration of prediction motor 21. Also, the A.-C. for illustrative purposes only, as four in number. Each secondary winding |6| corresponds to_ one 25 circuits in device |19 may include proper phase shifting apparatus to cause the voltage output prediction quantity to be compensated for. It to be in quadrature with the voltage of line 13, to will be clear that as many secondary windings ergized directly lfrom the alternating supply ‘ Transformer |51 has plural similar secondary windings |6|, shown in this instance. source 13. insure proper operation of .two-phase prediction . " motor 21. The operation oi’ this circuit is the Each secondary winding |5| is shunted by a centertapped resistor |63 oi' high resistance 30 same as that of Fig. 3. and positions shaft 25 at the angle corresponding to the total prediction value, and by a potentiometer |65. The variable voltage. arm |61 of each potentiometer |65 is controlled Fig. 5 shows a push-pull modulator circuit in accordance with the value of the quantity for suitable for use in the circuits of Fig. 4 as the whichl prediction correction is required, in such modulator |35. This modulator circuit converts a fashion that .the voltage between each variable reversing polarity D.-C. into a corresponding re arm |61 and its corresponding centertap of re versing phase A.-C. The direct input voltage is sistor |63- is proportional, by the same propor applied to input terminals |90, |8| and is amtionality factor, to the prediction angle needed pliñed in conventional D.-C. amplifier |83, the for correction of that quantity. This may be ac complished by driving the arms of linear wound 40 amplified direct voltage appearing across center tapped resistor |85. This ampliñed voltage is potentiometers |65 from the mechanism which applied in opposition to ythe two grids |81, |89 of computes the required prediction angles, through a twin-triode tube |9| by means of a center cams which yield the required relationship, or by tapped input resistor |93 whose center-tap |95 . using direct drive and non-linear wound poten tiometers |65 which will also yield .the proper 45 is connected to cathodes |91, |99 of twin-triade |9| by means of a. cathode bias resistor 20|. Grid voltage-angle relationship. A suitable system is current-limiting resistors 203 may be used to shown. in Bond Patent 2,208,623. Any other prevent excessive grid current, should any grid means for obtaining these prediction voltages may be'used as desired. maybe used. ’ ` These prediction voltages are added by being 50 connected in series, as shown. lSince these volt ages are derived from similar plural secondary windings of the sa me transformer, their phase re lationships will all be phase coincidence or phase opposition, so that they may be added arith 55 metically to produce the required resultant pre diction voltage. The resultant is applied to the input of full-wave demodulator |69 by means of transformer |1I. The circuit'of a suitable demodulator is shown in Fig. 6. The output of this 60 swing positive. Anodes 205, 201 are connected to the outside terminals of center-tapped resistor 209 in par allel with one primary 2I| of output transformer 2|3. A source _of alternating current 223 of line frequency is connected between the center taps |95 and 2 I5 of resistors |93 and 209, respectively. Let it be assumed that, for a particular polarity of input voltage, grid |81 is positive with respect to centertap |95 and grid |09 negative. Then, on positive half cycles of the applied A.-C., anode 205 will have increased current, but anode 201 will have decreased current, compared to the cur rent with zero input voltage to grids |01, |99. tude corresponds to the amplitude of the input On negative half cycles neither anode will con alternating voltage and whose polarity corre duct. Hence, a voltage drop of a particular po sponds to the phase of the input voltage. The output direct voltage from demodulator 65 larity appears across resistor 209, and only dur ing positive half cycles of the supply voltage. |69 is connected in series with the direct time-of This voltage drop will give a half-wave output ñight prediction voltage, as in Fig. 3, to give the from transformer 2|3 of one particular phase. total prediction voltage. If the input polarity were to reverse, making grid .The prediction potentiometer 29 has a circuit |89 positive with respect to point |95, and grid exactly the same as in Fig. 3, except >that D. C. |81 negative, then, in the same way, anode 201 energization is'used. The energizing potential for would have increased current, and anode 205 potentiometer 29 is obtained for alternating decreased current. and again only on positive half supply line 13 by means of full wave -rectifier cycles of the applied A.-C. This would cause a |13 having iilter choke |15 and filter condenser |11. Choke |15 may be' replaced by the ileld 75 voltage drop to appear across resistor 209 of op demodulator |69 is a direct voltage whose ampli 2,414,102 . 14 i3 posite polarity, giving an output half-wave from transformer 2| 3 of opposite phase from that of the ñrst instance described. Thus, the phase of the output voltage is sensitive to the polarity of the input voltage. or secondary winding, or both, may be tuned to the frequency of the predominating A.-C. com 2|1. are negative. ing in series with terminal 213. Either primary ponent, which is twice the line frequency, A further by-pass condenser 211 is also used. In order to provide a full-wave output, which The input voltage to transformer 23| is of the minimizes distorting harmonics, an exactly simi same frequency as source 13, and is adjusted by lar twin-triode 2| 1 is- used, with its input con any suitable means to be cophasal (or anti-phas nected in parallel with the input to twin-triode al) with the voltage oi’ source 13. |9I. The output of tube 2|1 is connected to a l0 Let it be assumed that the phase of the input second primary 2|9 of transformer 2| 3 by a cir to transformer 23| is such that, at a particular cuit identical to that of tube |9I. The cathodes instant of time to be considered, grids 231 and of tubes |9| and 2|1 are connected together as 24-5 are positive with respect to their cathodes, by conductor 22|, and their anodes are energized while grids 239 and 243 are negative. Further from the same source. However, the anodes of 15 more, let it be supposed that at this same in tube |9| are energized in phase oppositionwith stant, anodes 249 and 253 are positive with re respect to the energization of the anodes of tube spect to their cathodes, and anodes 25| and 255 This is accomplished by supplying both ' tubes from source 13 by means-of a transformer Then anode 249 will conduct, since both it and 225 having a center-tapped secondary. The cen 20 its grid are positive. Anode 25| will not conduct, ter tap 221 is connected to the center-tap |95 of being negative. Anode 253 will not conduct, its input resistor |93, and the outer terminal of one grid 243 being negative. Anode 255 will not con` secondary section 223 is connected to the anodes duct, being negative. Accordingly, a voltage will of tube |9| by means of the center-tap 2|5 of re appear only across resistor 251, making output sistor 269, while the outer terminal of the’other terminal 21| negative with respect to terminal section 229 is connected in similar fashion to 213. the anodes of tube 2|1. In the succeeding half-cycle from the instant As a result of this connection, tube. |9| will ’ of time considered above, grids 231 and 245 will conduct on half-cycles of the applied A.-C, of one be negative, grids 239 and 243 will be positive, polarity, while tube 2|1 will conduct on the half anodes 249 and 253 will be negative and anodes cycles of opposite polarity. As described above, 25| and 255 will be positive. Hence, only anode the phase of the output voltage will reverse when 25| will conduct, the remaining anodes and/or the polarity of the input voltage reverses. 'I'he grids being negative. Again current will- be device of Fig. 5 is therefore a full-wave modula passed through resistor 251, and the same polar tor suitable for use with the circuit of Fig. 4. ity of D.-C. output will be obtained. Fig. 6 shows a full-wave demodulator suitable If the input to transformer 23| should reverse for use with the circuit of Fig. 4. The reversible phase, with respect to source 13, then, at one phase A.-C. input is applied to the primary wind instant of time grids 231 and 245 would be nega ing of transformer 23| which has a center-tapped tive, grids 239'and 243 would be positive, anodes secondary winding having two sections 233, 235. 40 249 and 253 would be positive and anodes 25| and 'I'he voltage across section 233 is applied cophas 255 would be negative. Under these conditions ally to grid 231 of twin-triode 24| and to grid only anode 253 would conduct, yielding a D.-C. 245 of tube 241. The voltage across section 235 output of opposite polarity from that of the case is applied cophasally to'grid 239 of tube 24| and considered above. to grid 243 of tube 241. Hence, the grids 231 and 45 On the succeeding half-cycle, all polarities 239 of tube 24| are energized in phase opposition would reverse, and only anode 255 would conduct. as are grids 243 and 245 of tube 241. Current Accordingly, Fig. 6 gives a phase-sensitive, full limiting resistors 203 may be used. The cath ì wave rectiñer or demodulator, suitable for use in odes of both tubes are« connected together and the circuit of Fig. 4. to the center tap of the secondary winding of In Figs. 4, 5 and 6, .tubes |21, |29, |13, |83, ISI, 50 transformer 23|. It’v desired, a fixed bias voltage 2|1, 24| and 241 have been illustrated as being may be inserted between points 234 and 240, or of the twin or duplex type. It is obvious that cathode bias resistors may be used in the cathode _two separate single tubes could equally well be circuits of the two tubes. used. Also, tubes |83, |9I, 2I1, 24| and 241 The anodes 249 and 25| of tube 24| are ener need not be of the triode type, as shown, but may gized in phase opposition from the secondary 55 be of any type of amplifier tube incorporating winding of a transformer 265 fed from the A.-C. a control grid. ' source 13.. The center tap of this secondary As many changes could be made in the above winding is connected to the cathodes by load resistor 251, which is by-passed by ñlter con.. 60 construction and many apparently widely dif ferent embodiments of this invention could be denser 259. Anodes 253, 255 of tube 241 are en made Without departing from the scope thereof, ergized in similar fashion from transformer 261 it is intended that all matter contained in the and have a similarly connected load resistor 26| above description or shown in the accompanying and ñlter condenser 263. Transformers 265 and shall be interpreted as illustrative and 261 are so connected that anodes 2.49 and 255, 65 drawings not in a limiting sense. ‘ Whose corresponding grids are cophasally ener Having described our invention, what we claim gized, are energized in phase opposition. Also, and desire to secure by Letters Patent is: anodes 25| and 253 are energized in phase oppo - 1. A target tracking device comprising a sight, sition. motive means for rotating said sight, generating Across load resistors 251 and 26| connected in 70 means driven by said motive means for generat series, there is connected a filter circuit 269 for ing a unidirectional voltage dependent on the filtering out all A.-C. components, leaving only speed of rotation of said sight, control means for pure rectified D.-C. at output terminals 21|, 213. generating. a. unidirectional signal voltage cor This filter includes a choking transformer 215 responding to _a desired speed of rotation of said having its terminal 21| and its secondary wind 75 sight, and means for controlling the speed of ro 2,414,102 ‘l5 tation of said motive means by the arithmetic 16 duced in said pickup coils of amplitudes depend ing on the position of said armature relative to said coils, means for balancing the voltages in duced in oppositely disposed pickup coils with said diiIerence of said voltages, whereby said sight will rotate at said desired speed. 2. A target tracking device as in claim 1, fur ther comprising means for transmitting the ori Ul armature in its neutral position, and means for connecting oppositely disposed pickup coils in entation of said sight to a remote point, means series opposition, whereby the resultant voltage connected to the output of said generator means output from each pair of pickup coils will rep for obtaining a prediction voltage corresponding resent by its phase and magnitude the sense to a desired angular correction of the orientation of said sight, and means under the control of said 10 and magnitude of the component of deflection of said handle along the transverse axis of said pair prediction voltage for compensating said orienta tion transmitting means for said angular cor of coils. rection. 3. A target tracking device comprising a sight, motive means for rotating said sight, generating means driven by said motive means for generat ing a speed voltage dependent upon the speed of rotation of said sight, control means for gen erating a signal voltage corresponding to a de tilever carried by said support, a control handle arranged on vsaid cantilever for displacement in any transverse direction relative to said sup port, the amount of displacement of said handle obtaining a voltage corresponding to said speed voltage, and means for controlling the speed of control voltages corresponding to the direction and magnitude of the pressure applied to said . 7. A control unit comprising-a support, a can- I thereby being dependent upon the magnitude of pressure applied thereto, and means respon-. sired speed of rotation of said sight, means for 20 sive to displacement of said handle for producing handle. rotation of said motive means by the algebraic 8. A control unit as in claim 7, wherein said sum of said signal voltage and the difference be tween said speed voltage and said obtained volt 25 voltage-producing means comprises a plurality of magnetic poles ñxed with respect to said casing age whereby said Ymotive means will continue to and carrying coils energized by alternating cur operate without signal voltage at a speed corre rent, and a magnetic armature member ilxed to sponding to said obtained voltage. said control handle for motion therewith. 4. A target tracking device comprising a sight, motive means for rotating said sight, generating 30 9. A target tracking device comprising a sight, motive means for moving said sight, a control handle mounted for deflection about a single point, means responsive to deflection of said han tation of said sight, control means for generating dle for moving said sight in a direction corre a signal voltage corresponding to a desired speed of rotation of said sight, means for controlling 35 sponding to the direction of deñection of said handle and at a speed corresponding to the mag the> speed of rotation of said motive means by nitude of deflection of said handle, means for the arithmetic difference of said voltages, means means driven by said motive means for generat ing a voltage dependent upon the speed of ro for transmitting orientation of said sight to a remote point, means connected to the output of transmitting the instantaneous orientation of said sight to a remote point to control the orien compensating for causing the sight to continue tracking at sub said generating means for obtaining a prediction 40 tation of a remotely situated gun, means to com pensate the transmitted orientation for predic voltage corresponding to a desired angular cor tion data whereby the gun will be oriented to- ' rection of the orientation of said sight, and means ward the future position of the target, and means under the control of said prediction voltage for said orientation transmitting means fory said angular correction. 45 stantially constant speed without deñection of said handle. 5. A target tracking device as in claim 3, in 10. A target tracking device comprising a sight, which said control means comprises a control motive means for moving said sight in azimuth, handle mounted in cantilever fashion for deflec motive means for moving said sight in elevation, tion about a single point, a magnetic armature carried by said handle. two parallel magnetic 50 a control handle mounted for deilection in all transverse directions about a ilxed point, means paths bridged at one end by a magnetic mem for controlling the velocity of said first motive ber and at the other end by said armature, means means in response to the component of deflection for applying equal alternating magnetomotive of said control handle in a predetermined direc forces to said two paths. a coil linking each path, whereby the voltage induced in each coil will 55 tion, means for controlling the velocity of said second motive means in response to the com depend upon the position of said armature, and means for connecting said coils in series opposi ponent of deiiection oi' said control handle in a different predetermined direction, and means re tion, whereby the voltage across both said series sponsive to the speed of each of said motive connected coils will reverse phase as the arma ture passes through theposition yielding` 'equal 60 means for supplying signals to said control means for operating said motive means in response to coil voltages. l an integrated value. of its corresponding com 6. A control unit comprising a casing, a con ponent of handle deflection. trol handle fixed at one end within said casing l1. A target tracking device comprising a sight. for cantilever deilection with respect to said cas ing, four pickup coils having their axesv parallel 65 motive means for orienting said sight, a control handle mounted for deflection, means for pro to the neutral undeñected axis of said handle ducing a control voltage in response to deflection and mounted equidìstant from said neutral axis both radially and angularly, an energizing coil mounted coaxial with said neutral axis, open magnetic circuit means connecting said pickup of said handle, means for integrating said voltage over a period of time, and means for controlling said motive means both by said integrated volt age and by said control voltage. coils with said energizing coil, a magnetic arma 12. A target tracking device comprising a sight. ture carried by said handle and positioned to complete said magnetic circuits, means for en a control handle, a cantilever securing said han ergizing said energizing coil from a 'source of dle on said sight permitting relative displacement alternating current, whereby voltages will be in 75 in any transverse direction, the amount o! dis 2,414,102 i7 placement being dependent upon the magnitude of pressure applied thereto, and means responsive to pressure applied to said handle for moving said sight in a direction corresponding to the direc tion of said pressure and at a velocity correspond _ing to the magnitude of said pressure. 13. A control unit comprising a casing, a eon~ 18 prising motive means for moving said object, gen erating means ‘operated by said motive means for generating a iirst speed signal dependent upon the speed of said object, means connected to said generating means for producing a second speed signal opposing said ñrst speed signal, control means for producing a control signal, and means for controlling the speed of said motive means according to the algebraic sum of said control trol handle mounted in cantilever fashion with respect to said casing for deñection in any radial direction with respect to the axis of its unde 10 signal and the difference between said speed ' flected position, a stabilizing reference surface signals. ' rigidly mounted on said casing and adjacent to 19. A control system for a movable object com said handle ina position yto be used by an oper prising motive means for moving said object, gen ator as a reference with respect to which said erating means operated by said motive means for handle may be deflected, said surface and said 15 generating a ñrst speed signal dependent upon handle being formed to conform to the contour the speed of Ysaid object, means connected to said of the hand of the operator whereby precise and generating means for producing a second speed steady neñection of said handle may be obtained, signal opposing said ñrst speed signal, a com and means responsive to arbitrary deflection of bining circuit connected to said generating means said handle for producing voltages each corre and said last-named means for combining said sponding in polarity and magnitude to the sense speed signals in opposition, control means for and magnitude of a component of said deñection producing a control signal, and means connected in a predetermined direction. to said combining circuit and said control means 14. A control system for a movable object com for controlling the speed of said motive means. prising motive means for moving said object, 20. A control system for a movable object com generating means for generating a speed signal prising motive means for moving said object, dependent upon the speed of said object, control generating means operated by said motive means means for producing a control signal, and means for generating a ñrst speed signal dependent upon for controlling the speed of said motive means the speed of said object, a condenser connected according to the diiïerence between said control to said generating means for producing a second signal and the time derivative of said speed speed signal in opposition to the signal from said signal. generating means, control means for producing a 15. A control system for a movable object com control signal, and means for controlling the prising motive means for i moving said object, speed 0f said motive means according to the alge generating means for generating a speed signal ' braic sum of said control signal and the diner dependent upon the speed of said object, a dif ence between said speed signals. _ a ferentiating‘network connected to said generat 21. A control system for a movable object com ing means for obtaining the time derivative prising a motor fdr moving said object. a gen thereof, control means for producing a control erator driven by said motor for producing a ñrst signal, and means connected to said differentiat 40 speed signal dependent upon the speed of said ing network and said control means for control object, a condenser connected in series with said ling the speed of said motive means according generator, an impedance connected in parallel to the difference between said control signal and with said series circuit. control means for pro said time derivative signal. ducing a control voltage, and means for control 16. A control system for a movable object com 45 ling the speed of said motor according to the alge prising a motor for moving said object, a gener braic sum of said control voltage andthe voltage ator driven by said motor for generating a speed across said impedance. signal dependent upon the speed of said object, 22. Tracking apparatus comprising a sight, a a condenser and resistance network connected to motor for turning said sight, a generator driven said generator for differentiating said speed sig 50 by said motor for producing a ñrst speed voltage nal, „a control device for producing a control dependent upon the speed of said sight, means signal, and _means for controlling the speed of connected to said generator for producing a sec- _ said motor according to the difference between ond speed voltage in opposition to said first speed said control signal and said differentiated signal voltage, control means for producing a control » 17. A target tracking device comprising a sight, voltage, and means for controlling the speed of motive means for rotating said sight, generating said motor according to the algebraic sum of said means driven by said'motive means for generat control voltage and the difference between said ing a voltage dependent upon the speed of rota speed voltages. tion of said sight, control means for generating 23. A tracking control comprising a controller a signal voltage corresponding to a desired speed of rotation of said sight, means for controlling the speed of rotation of said motive means by the arithmetic difference between said voltages, means for transmitting the orientation of said sight to’a remote point, means connected to said generating means for obtaining a prediction volt age corresponding to a desired correction of the orientation of said sight, and means controlled by said prediction voltage for oiïsetting said ori and a driven object, motive means for rotating the latter. a generator driven by said means pro ducing a voltage proportional to the rotary speed of said object, means at the controller produc ing a voltage proportional to a desired speed of said object, other means deriving a voltage cor responding to said generator voltage, and means for opposing said generator voltage by said de rived voltage whereby said motive means will maintain its speed for a time without a controller entation> transmitting means relative to said 70 voltage. sight in accordance with said correction whereby the desired corrected orientation is transmitted by said transmitting means. » 18. A control system for a movable object com HARVARD L. HULL. WILLIAM C. HARTMAN. RAYMOND C. GOERTZ.