US2421230A - Electrohydraulic position control system - Google Patents

Description

May 27, 1947. G. AGlNs ELECTRO-HYDRAULIC POSITION CONTROL SYSTEM Filed May 12, 195s INVENTOR mm k Patented 27, 1947 OFFEC ELECTROHYDRAULIC POSITION CONTROL SYSTEM George Agins, Brooklyn, N. Y., assignor to Arma Corporation, a corporation of New York Application May 12, 1936, Serial No. 79,290

(Cl. 3l8-30) 25 Claims. l

This invention relates to electro-hydraulic position control systems and has particular reference vto electro-hydraulic systems for positioning gun mounts in accordance with movements of a remote observation instrument, although the invention is not limited to that use.

In positioning a gun in train in accordance with th'e movement of the director, it is not only necessary to provide ample power to drive the h'eavy gun mount, but it is also necessary to control the drive with the degree of accuracy required to secure accurate gun direction, and this requires compensation for errors resulting from the transmission of movements from the director to the gun mount, some of which are due to the mass, inertia and momentum of the heavy gun mount. Similar errors occur in positioning the gun in elevation and/or depression and must be compensated for.

In accordance with the present invention, a position control system, especially adapted for positioning gun mounts, is provided, in which the gun mount is driven by a variable speed hydraulic gear controlled electrically by means responsive not only to movements of the observation instrument and calculating mechanism of the remote director, but also to error-introducing movements of the director, the gun mount and the hydraulic gear. The errors, which are compensated for electrically, include hunting or oscillation of the gun mount and hydraulic gear at the end of a movement thereof, velocity and acceleration lags due to compensating means, and the like.

An electrical synchronizing diierential mechanism is also provided for automatically eiecting approximate agreement between the director and the gun mount in case of large deviation between them, so as to enable high-speed registering mechanism to assume control and position the gun mount in exact agreement with the director. Arrangements are provided for selectively switching the control mechanism from automatic to manual regulation, and also to direct manual mechanical operation of the hydraulic gear, as well as other items of regulation insuring accuracy and rapidity of response.

It will be seen that the electro-hydraulic control means of this invention is extremely sensitive and accurate in its operation, despite the large masses which are moved thereby, so that the gun mount may be positioned as rapidly and with as great accuracy as can a much lighter device with th'e control systems employed heretofore.

For a more complete understanding of the invention, reference may be had to the accompanying drawing in which Fig. 1 illustrates diagrammatically and schematically the electrical and mechanical arrangement of the electrohydraulic position control system of this invention, and Fig. 2 illustrates diagrammatically one form of converter for converting the alternating current signal into corresponding direct current.

Referring to Fig. l, numeral l0 designates an observation instrument such as a director which is adjustable zin lelevation and train while following a moving target or a target which is stationary while the vessel or other support on which the director is mounted moves. I l represents the gun mount, which is usually located at a point remote from the director I0 and is adapted to be driven automatically by the director I0 to be aimed on the selected target, suitable corrections for parallax and th'e like being introduced automatically through diierential I5 by instrument I5', having range and target bearing inputs, to compensate for the variation in the angle of fire due to displacement of the director I0 and the gun mount l I. In the following description, the control of the gun mount in train will be described, it being understood that the same or similar mechanism may be used for directing the gun in elevation and/or depression.

Automatic control Assuming that automatic control is desired,

transfer switch I2 is adjusted in such' a way that l opposite contacts of the two left-hand rows a of contacts are bridged by brushes I3 in the manner indicated by the dotted lines.

The director I0 is provided with a ring gear I4 rotating in a substantially horizonta1 plane as the director I0 is moved in train. Meshing with gear I4 are pinion I6 and gear I1, the former being operatively connected to a high speed transmitter I8 and the latter to a low speed transmitter I9. These transmitters are preferably of the three-phase self-synchronous type, although other equivalent transmission devices may be used with equal facility, and their relative angular displacement ratio is preferably thirty-six to one. The terminals of the stator of the high speed transmitter I8 are connected by wires 20 through transfer switch I2, contacts 2|, 22 and 23, to the terminals of the rotor of high speed regulator 24, which' is connected by shaft 25 and the bevel gears 26 to the drive shaft 21 of the variable speed hydraulic gear 28 actuated by constant speed motor 29 and connected through shaft 21 by bevel gears 28' to the turn table of the gun mount II.

The hydraulic gear 28 may be of more or less conventional design, comprising a tilt box in end A whose angle of tilt by control shaft 38 determines the rate of speed variation at which the drive sh'aft '21 is driven by the B end as compared to the constant speed input of actuating motor 29. Tilting of the tilt box from one side of neutral vertical position to the other reverses the direction of rotation of the drive shaft 21.

The position of the rotor of the high speed regulator 24 determines the voltage across the secondary terminals 29 and 30 of the stator of the high speed regulator 24. 'Ih'e terminals 29' and 30 are connected by wires 3| to the converter 32, forming no part of the present invention, but arranged to convertan alternating voltage of varying amplitude and reversible phase into a. direct current voltage of proportional magnitude and reversible polarity. The converter 32 may be of any desired form, and by way of example, may be constructed and arranged as illustrated and described in copending application Serial No. 78,944, filled May 9, 1936, by applicant.

For convenience, the construction of the converter 32 is illustrated herein by Fig. 2, and may include the input transformer 140 connected to the wires 3| and having two secondary windings |4| and |42, a bias transformer |43 supplied from the alternating current source |03 and having two secondary windings |44 and |45, and two rectifier bridges |46 and |41 with rotating resistors |48 and connected in series with' secondary windings |4|, |44 and |42, |45, respectively. These rectiiier bridges |46 and |41 are so connected that the xed alternating current voltage in the secondary circuits of 44 and |45 is added to the signal voltage in one bridge andV subtracted from that in the other bridge, depending upon the direction of deviation between the director and the gun mount |l. The resulting proportional direct current voltages are opposed and the voltage output of the converter 32 has a magnitude and direction determined by the difference between the voltage output of th'e bridges |46 and |41 and will reverse as the phase of the input signal reverses. When the deviation is zero, the voltage output of the rectler bridges is equal and thus they nullify, so that the voltage output of the converter is zero. To the output of the converter 32 are added the voltages generated in the director generator 33 connected by pinion 34 to the spur gear I4 of direcetor I0, and the gun mount and control shaft damping generators 35 and 36. Damping generator 35 is driven by drive shaft 21 through the beveled gears 31, while damping generator 36 is driven from the control shaft 38 of variable speed hydraulic gear 28 by shafts 82 and 83 and bevel gears 84 and 85.

The director generator 33 is connected in the output terminals of converter 32 by wires 40 and 4|, and the damping generator 35 is connected by wire 42 in series with the control shaft generator 36, which is connected to an input terminal of inverter 44 by wire 43. IThe resultant total direct current voltage is applied as input to the inverter 44, which functions to change the direct current input voltage of varying magnitude and reversible polarity to an alternating current voltage of proportional amplitude and reversible phase. The construction of the inverter forms no part of the present invention and may be of the form illustrated in copending application Serial No. 73,852,1ed April 11, 1936.

The output voltage of inverter 44 is stepped up by input transformer 45 and applied to the grids of the two pairs of vacuum tube control rectiers 46 and 46', appropriate iilament transformer 41, grid bias transformer 48, and power transformer 49 arrangements being provided.'

Connected in the plate circuits of the two rectiflers 46, -46' is the hydraulic gear control motor 58. The essential portion of the control circuit of rectifiers 46 is traceable by wires 50', front contact 5|' of closed limit relay 52, wire 53, bridged contacts 54 of transfer switch I2, wire 55 and control motor 50. For the rectiflers 46 the circuit is traceable by wire 62, front contact 6| and center contact 59 of limit relay 60, wire 58, center contact 51 of limit relay 52, and wire 56 to control motor 50. This motor 50 acts through magnetic clutch 5| to properly position the control shaft 38 of the variable speed hydraulic gear 28. Magnetic clutch 5| is normally closed, the circuit of which may be traced from negative terminal of direct current supply 63, bridged transfer switch I2, contacts l64, wire 65, contact 66, wire 61, clutch 5| winding, wire 68, and the normally closed contacts of relays 69 and 10 to the other side of the line.

With the magnetic clutch 5|, the high speed transmitter |8 system, the director generator and their appurtenant parts energized by the adjustment of transfer switch to position a for automatic operation, exact control is maintained by the high speed transmitter I8 when the angular position of gun I in train is initiallyin approximate agreement with the horizontal deflection of the director I8. This exact control takes place when the windings of the rotor of the high speed regulator 24 are moved by gun mount into registry with the windings of the stator, so that the voltageacross its output terminals 29 and 30 is zero and there is no energization of the hydraulic gear control motor 50. However, there is a tendency of the gun mount to oscil1ate or hunt and in order to compensate for this hunting, the damping generator 35 is provided, and is geared to the drive shaft 21 of the hydraulic gear 28, so that the voltage developed across the terminals 42, 1| of the damping generator 35 is proportional tothe velocity of the gun mount I and may be applied, at proper polarity, to suppress any tendency of the gun mount to sustain an oscillation. Similarly, since the control shaft generator 36 is geared to the shaft 38 of control motor 50, the voltage developed across its terminals 42, 43 is proportional to the speed of the control motor 5|) and may be utilized, at proper polarity, to suppress any tendency to'hunt due to a lag in the response of control motor 50.

The damping generator 35 and the control shaft generator 36 are connected in series and the voltages developed by both generators are combined. The deviation voltage ofregulator 24` which is applied to the converter 32 will be zero when the gun mount is in exact positional agreement with the director l0, and the sum of the voltages appliedlto the inverter 44 must be zero for constant velocity conditions of the system. 'I'he damping generator 35 produces a voltage for damping purposes but at the same time it introduces an error to the system in the forni of a velocity lag, so that the deviation voltage across the regulator 24 terminal 29 and 30 will not be zero. In order to compensate for this velocity lag, the director generator 33 geared to the director l0 is employed, and-develops a voltage across its terminals 12, 13 which 'is proportional to the velocity of the director I8.

inasmuch as the velocities of movement of the director I0 and gun mount II are approxi-` .mately the same, a portion of this voltage, predetermined by the relative values of resistances 14 and 15, is proportional to the damping gento be described, wire 19, connected contacts 80 and 8I of transfer switch I2 and wire 1I. 'I'he magnitude of this compensating voltage is such as to compensate for the. velocity lag introduced by damping generator 35, whereby the deviation between the director III and gun mount II for constant velocity conditions is reduced to a negligible quantity. It will be observed that this compensation for velocity lag introduces no disturbing factor, for it is independent of the speed of power motor 29 of the hydraulic gear y2-8, and of any variations in the field excitation of director and damping generators 33 and 35, respectively, since any uctuations in the field voltages of these generators occur simultaneously, due to their common source 63, and have the same effect on both, so that the sum of their output voltages remains zero.

Another compensation' 'is provided. In conventional types of variable speed hydraulic gears, such as 28, the speed of the B end drive shaft 21 is proportional to the displacement ofthe A end control shaft 38 from neutral position and the direction of rotation of the drive shaft 21I depends upon the direction of displacement of the control shaft 38 from this neutral position, so that acceleration of the drive shaft 21 is proportional to the velocity of the control shaft 38. Inasrnuch as the voltage developed by the control shaft generator 36 is proportional to the speed lof the control shaft 38, to which it is directly connected by shaft 82 and 83 and bevel gears 84 and 85, and is also proportional to the acceleration of drive shaft 21, it follows that for any acceleration of drive shaft 2`I the voltage across the output terminals 29', 30 of the high speed regulator 24 cannot be zero, but must be of sufficient magnitude to cause a voltage, equal and opposite to that of the control shaft generator 36, to be developed across the output terminals 4I, 86, of converter 32. This results in an acceleration lag which, although considerably less than the velocity lag, nevertheless requires compensation for accurate control.

This compensation is introduced by means of an inductance 81 in series with the resistance 14, so that, although the voltage across the terminals of this inductance is zero for constant velocity of the director I8, because the current is constant, nevertheless, for an acceleration of the director IU an additional voltage proportional to the rate of change of the current is developed in inductance 81. Since the resistances 14 and 15 are large compared to the inductance 81, the current flowing through the inductance is sensibly proportional to the voltage developed across the terminals 12, 13 of the director generator 33 or proportional to the velocity of director I Il, so' that the voltage across the terminals of inductance 81 is proportional to the acceleration of director I0. Consequently, compensation for the acceleration lag introduced by control shaft generator 36 is provided. Also, in this way the acceleration lag due to other causes such as regulation of hydraulic gear motor 29, elasticity of the hydraulic gear 28, and thelike, is compensated for.

In case of a large initial deviation between the director l0 and the gun 'mount II, the low-speed transmission system is employed, which is arranged to drive the gun mount to approximate agreement with the position of the director I0, so that the high speed transmission system just described may automatically assume control. As

aforementioned, the high-low speed gear ratio is preferably thirty-six to one. The initial impulse to obtain this approximate agreement of the director and gun mount is provided by the synchronizing differential 18, the roto-r 88 of which is connected by .wires 89 to the low speed transmitter I9 driven by the director I Il through gears I4 and I1 and shaft 90. The stator 9I of synchronizing differential 18 is connected by wires 92 to low speed regulator 93, geared to the gun mount II by gears 94 and 95, shaft 25, bevel gears 26, shaft 21, and bevel gears 28', so that deviation of the rotor 88 of synchronizing differential 18 from a predetermined position will be proportional to the deviation between the gun mount I I and the director-III.

During approximate angular agreement of the gun mount I I with the director I IJ, the brush 18 carried by the shaft 96 of differential rotor 88, engages segment 11 and the high speed regulator 24 assumes and maintains control inthe manner described. During any greater deviation of the gun mount I I, brush 18 engages either l segment 91 or 98, depending upon the direction of the deviation, thus depriving high speed regulator 24 of control by opening the output circuit of converter 32 and connecting the appropriate half of potential divider 99 in the inverter circuit. The center tap of the potential divider 99, which is supplied with direct current at constant voltage, is connected by wire |08 to Wire 86 of the inverter 44 input. Accordingly, the polarity of the inverter 44 input depends upon the direction of the deviation between the director I0 and the gun mount II. Thus, when brush 18 engages j, segment 98, the polarity of input 43 is positive j,

and when it engages segment 91 it is negative. The voltage across both halves of the potential divider 99 are predetermined, so that the control motor 50 is energized by grid control rectifiers 46 or 46', depending upon the phase of the inverter 44 output voltage, to rotate in the proper direction to adjust variable speed gear 28 tc drive the gun mount II and damping generator 35 at such speed that the voltage developed by the damping generator 35 is equal and opposite in polarity to the voltage across that half of the p0- tential divider 99 which is connected in the circuit by brush 18'.

The gun mount I I is accordingly driven in a direction such as to reduce the angle of its deviation from the director I0, and, in so moving, it rotates the rotor of low speed regulator 93, the eld winding IUI of which is energized from a1- ternating current source |03 through bridged contacts |02 of transfer switch I2, so that stator 9| of synchronizing differential is energized to cause rotor 88 to rotate through a proportional angle and move brush 18' into reengagement with segment 11, thus transferring the control to high speed regulator 24 for operation in the manne!` described.

Local control If local power control is desired instead of automatic control, transfer switch I2 is adjusted sw that 4opposite contacts of the two right-hand rows tacts 11, 9198, inductance 81 and resistance 15 f are simultaneously disconnected. Bridging of the lower contacts and |06 connects one side of the alternating current supply |03 to the eld winding |01 of local power transmitter |08, the

rother side ...i which is connected directly to supply |03. Similarly, the field winding |08 of local power control generator H0, geared by gears '|22 and |23 to shaft |2| of local transmitter ||3, is

connected to direct current supply 63 throughv bridged contacts 8'6 and and wires ||2. The

vrotor ||3 of local transmitter |08 is connected through bridged contacts yIUI.y H5 and ||6 and wires to the rotor of high speed regulator 24.

, One'brush of local control generator ||0 is connected by wires ||1 and 4| inthe output of converter 32, and the other brush through switch contact |04 and 8| and wire 1| is connectedfto damping generator 35 in'series with control shafty generator 36, in turn connected by wire 43 to the y inverter 44 input.

The control motor 50 is reconnectedin the circuitv by bridging of switch contacts ||8. Control is accordingly transferred to handwheels ||9 connected' byvbevel gears |20 andr shaftv |2| to the rotor ||3 of local transmitter |08, the displace` ment of which causes a phase displacement in high speed regulator 24, resulting in venergization of control motor 50 for adjustment of the control shaft 38 of variable speed gear 28, so that gun mount lis driven through a proportionate angle determined by the consequent angular agreement o f the high speed regulator 24 with the local transmitter |08, so that current no longer ows in the amplifier circuit. With this follow-up arrangement, the reaction of the variable speed hydraulic gear 28 control shaft 38 on the handwheels ||9 is eliminated, and there is no velocity lag, both items resulting in greater ease of control.

Direct manual control lof the switch I2 by means of links |25, or the like, is a friction clutch |26, one side of which is connected to shaft 2'5 and the other side thereof is connected by pinion |21 to gear |22 in shaft |2| controlled by handwheels ||9 and connected to local transmitter |08. The clutch |26 is disengaged during automatic or local control, but when the handle of switch |2 is shifted to the position for direct manual control, links are actuated to engage clutch. |26. Inasmuch as disconnection of transfer switch contacts 66 and or 64, by shifting the switch 2 to the direct manual control position b disengages magnetic clutch 5|. the handwheels ||9 are directly connected to the control shaft 38 of variable speed gear 28 by bevel gears |20, shaft |2|, gears |22 and |21, clutch |26, shaft 25, differential |28, shaft |29, and bevel gears |38. Rotation of the handwheels I9 in one direction accordingly adjusts the variable speed gear 28 to drive gun mount in the appropriate direction, the back drive through shaft 21 bevel gears 26, differential |28 and shaft 8 |29 gradually restoring control 'shaft 38 yto its inl-v tial position when the gun mount has been moved vthrough the angle designated by the operator in rotating handwheels IIS.

In order to prevent interference between the y gun mount and other adjacent objects which may limit train of the mount in either direction. linut stop mechanism |3| is provided. This mechanism includes a screw |32 rotated by bevel gears |33 driven by shaft 25, vso that'stuewr |32 turns through an angle proportional to the angle of train of the gun mount and to the deflection of the control shaft 38. Inasmuch as the motion of control shaft 38 is small compared to the train of ythegun mount the position of the nut |34 is approximately equivalent to the gun position. When the gun mount nears the limit of its permissible movement in one direction. nut |34 engages and opensr either limit contact |35 orv |38, deenergizing the holding circuits of corresponding limit relays 60 or 52, respectively, which, by means of respective open contacts 5| or 5|?, break the plate circuits of grid control rectifiers 48, thus stopping control motor v50 and, consequently, f

' 52 or 60, respectively, deenergizes the corresponding winding of clutch relay 10, vwhich in turn releases its armature 31 to 'deenergize magnetic clutch 5 I, mechanically'disconnecting control mov tor 50 from hydraulic gear 28 control shaft 38. The other of the two limit relays 52 or 50 remains energized and 'the' corresponding winding of relay 10 is placed in series with the armature of control motor 50, so that when the rectiers 46' are energized, tending to drive the control motor 50 in the opposite direction, the armature current through the said winding of relay 10 will close its armature |31 to reenergize magnetic clutch 5| and reconnect the control motor 50 to the control shaft 38, so as to permit the gun mount to be driven back from its stop.

Immediately after opening either contact |35 or |36. nut |34 engaged and was stopped by abutment |38 or |39, respectively, and screw |3| was locked against further rotation, so that control shaft 38 is moved through differential |28 by the drive shaft 21 in a direction such as to bring the gun mount to rest. This operation of the limit stop mechanism is the same for both automatic and local power control, and for the direct manual control,v its operation is mechanical.

I claim:

l. In a system for positioning a controlled member in accordance with the movement of a. controlling member, the combination of motive means for actuating the controlled member, electrical means responsive to positional disagreement between the members for controlling said motive means, and electrical means jointly responsive to the algebraic sum of the positional disagreements of both members and the rate of change thereof for regulating said first electrical means.

2. In a system for positioning a controlled member in accordance with the movement of a controlling member, the combination of motive means for actuating the controlled member, electrical means responsive to positional disagreement between the members for controlling said motive means, and electrical means jointly responsive to the positional disagreement and a change in the rate of lspeed of movement of both of said members for regulating said rst electrical means.

3. In a system for positioning a controlled me ber in accordance with the movement of a controlling member, the combination of motive means for actuating the controlled' member, electrical means responsive to positional disagreement between the members for controlling said motive means, electrical means responsive to the velocity of movement of either of said members for' regulating said ilrst electrical vmeans, and electrical means jointly responsive to the positional disagreement and a change in the rate of movement of both of said members for modifying the regulation of said ilrst electrical means by said second electrical means.

4. In a system for positioning a controlled member in accordance with the movement of a controlling member, the combination of motive means for actuating the controlled member, electrical means responsive to positional disagreement between the members for controlling, said motive means, electrical means responsive to the velocity of movement of said controlling member for regulating said first electrical means, and electrical means jointly responsive to thel positional disagreement and a change in the rate of movement of both ofsaid members for modifying the regulation of said ilrst electrical means by said second electrical means.

5. In asystem for positioning a controlled member in accordance with the movement-of a con. trolling member, the combination of driving power means for the controlled member, electrical means responsive to positional disagreement between the members, a control motor for said power means energized by said electrical means for causing `said power means Yto drive the controlled member in accordance with the movement of the controlling member, and a generator actuated by said control motor for modifying the output of said electrical means to effect a damping of the movement o said controlled member.

6. In a system for positioning a controlled member in accordance with the movement of a controlling member, the combination of driving power means for the controlled member, electrical means responsive to positional disagreement betweenthe members, a control' motor for said power means.

modifying the output of said electrical means to,7

effect a damping of the movement of said controlled member.

7. In a system for positioning a controlled mem-y ber in accordance with the movement of a controlling member, the combination of driving power means for the controlled member, electrical means responsive to positional disagreement between the -members, a control motor for said power means energized by said electrical means for causing said power means to drive the controlled member in accordance with the movement of the controlling member, and electrical means responsive to the algebraic sum of the movements of both of saidA members Yfor modifying the output of said electricallmeans to eilect a damping of themovement oisaid controlled member. l

In a'system for positioning-a controlled member accordance with the movement of a controlling member, the combination of driving power mean's for the controlled member, electrical means responsive to positional disagreement between the energized by said electrical means for causing said power means to drive the controlled'member in accordance with the movement of the controlling member, a generator actuated by said controlling member, a generator actuated by said controlled member, and means for modifying the output of said electrical means with the Joint out"i puts of said generators to effect a damping of the movement of said controlled member.

9. In a system for positioning a controlled member in accordance with the movement of a controlling member, the combination of driving power means for the controlled member, electrical means responsive to positional disagreement between the members, a control motor for said power means energized by said electrical means for causing saidpower means to drive the controlled member in accordance with the movement of the controlling member, a generator actuated by said controlled member, a generator actuated by said control motor, and means for modifying the output of said electrical means with the joint output of said generators to effect a damping of the movement of said controlled member.

10. In a system for positioning a controlled member in accordance with a controlling member, the combination of driving power means for the controlled member, a control motor therefor, means responsive to a predetermined positional disagreement between said members for inducing a signal voltage corresponding in magnitude and direction to the magnitude and direction of such positional disagreement, a plurality of thermionic relays having plate circuits selectively controlling said control motor, one'of said relays being responsive to voltage in one direction and the other relay being responsive to voltage in the opposite direction, and means for impressing said signal voltage jointly on said relays for energizing the control motor to cause said power means to drive the controlled member into positional agreement with the controlling member.

11. In a system for positioning a controlled member in accordance with a controlling member, the combination of driving power means for the controlled member, a control motor therefor, means responsive to a predetermined positional disagreement between said members for inducing a signal voltage corresponding in magnitude and direction to the magnitude and direction of such positional disagreement, a plurality of thermionic relays having plate circuits selectively controlling said control motor, one of said relays being responsive to voltage in one direction and the other relay being responsive to voltage in the opposite direction, means for impressing said signal voltage jointly on said relays for energizing the control motor to cause said power means to drive the controlled member into positional agreement with the controlling member, and means.

responsive to a positional disagreement between said members in excess of the said predetermined positional disagreement for impressing additional voltage on said relays to energize said control motor to cause said power means to move the controlled member to said predetermined positional disagreement for assumption of control by said rst responsive means.

12. In a system for positioning a controlled member in accordance with a controlling mem- A ber, the combination of drivingpower means for the controlled member, a. control motor therefor, means responsive to a predetermined positional disagreement between said members'for inducmembers, a control motor for said power means `'(5 lng a signal voltage corresponding in magnitude and direction to the magnitude and direction of` such positional disagreement, a plurality ot thermionic relays having plate circuits selectively controlling said control motor, one of said relays being responsive to voltage in one direction and the other relay being responsive to voltage in the opposite direction, means for impressing said signal voltage jointly on said relays for energiztrolled member to said predetermined positionalv disagreement for assumption of control by said rst responsive means, and means responsive to the speed of said control motor for varying said signal voltage to effect damping of the movement of the controlled member.

13. In a system for positioning a controlled member in accordance with a controlling member, the combination of driving power means for the controlled member, a control motor therefor, means responsive to a predetermined positional disagreement between said members for inducing a signal voltage corresponding in magnitude and direction to the magnitude and direction of such positional disagreement, a plurality of thermionic relays having plate circuits for controlling said control motor, one of said relays being responsive Y to voltage in one direction and the other relay being responsive to voltage in the opposite direction, means for impressing said signal voltage on said relays for energizing the control motor to cause said motive means to drive the controlled member into positional agreement with the controlllngmember, second means responsive to a positional disagreement between said members in excess of the said predetermined disagreement for selecting a source of additional voltage of a polarity depending on the direction of said excessive positional disagreement, and means for impressing the voltage of said second responsive means on said relays for energizing the control motor to cause said power means to drive the controlled member to said predetermined positional disagreement for assumption oi.' control by said ilrst responsive means.

14. In a system for positioning a controlled member in accordance with a controlling member, the combination of a driving power means for the controlled member, a control motor therefor, an electrical diil'erential operatively connected to said members and responsive to a predetermined positional variation between them, a seoond electrical diierential operatively connected to said members and responsive to a positional variation between them in excess of the said predetermined variation, an electrical controller energized by said rst differential for energizing said control motor to cause said power means to position said controlled member in accordance with the movement of the controlling member, and switching means actuated by said second differential for impressing a selected voltage on said controller to additionally energize said control motor to cause said power means to drive said controlled member to said predetermined positional variation for assumption of control by said ilrst electrical differential.

15. In a system for positioning a controlled member in accordance with a controlling memfber, the combination of a driving power means i'or the controlled member, a control motor therefor, an electrical diil'erential operatively connected to said members and responsive to a predetermined positional variation between them, a second electrical differential operatively connected to-said members and responsive to a positional variation between them in excess of the said predetermined variation, a plurality of thermionic relays having plate circuits controlling said power motor, one of said relays being responsive to voltage in one direction and the other relay being responsive to voltage in the opposite direction, means for impressing the output of said first diiferential on said relays to drive the controlle'd member into positional agreement with the controlled member, and means actuated by said second differential for applying additional voltage to said relays of a polarity depending upon the direction of said excessive positional variation to drive the controlled member to said predetermined positional variation for assumption of control |by said ilrst differential.

16. In a system for positioning a controlled member in accordance with a controlling member, the combination oi.' a variable speed power device for driving said controlled member, a reversible electric motor for positioning the variable element of said device, an electrical difierential responsive to the degree and direction of a predetermined positional variation between said members for developing a signal voltage of proportional magnitude and direction, means for applying said signal voltage to said control motor for rotating it through an angle in a direction corresponding to the magnitude and direction of said secod voltage to cause said power device to drive said controlled member in accordance with the movement of said controlling member, a source of direct current potential, a polarity selector switch linterposed between said source and said voltage-applying means, a second electrical diiferential responsive to the direction of a positional variation between said members in excess of the said predetermined positional variation for actuating said switch to impress a voltage on said voltage-applying means of a polarity corresponding to the direction of said excessive positional variation for positioning the variable element of said device to drive the controlled member to said predetermined positional variation for assumption of control |by said rst responsive means.

17. In a system for positioning 'a controlled member in accordance with a controlling member, the combination of a variable speed power device for driving said controlled member, a reversible electric motor for positioning the variable element of said device, an electrical differential responsive to the degree and direction of a predetermined positional variation between said members for developing a, signal voltage of proportional magnitude and direction, means for applying said signal voltage to said control motor for rotating it through an angle in a direction corresponding to the magnitude and direction of said second voltage to cause said power device to drive said controlled member in accordance with the movement of said controlling member, a second electrical diierential responsive to the direction of a positional variation between said members in excess of said predetermined positional variation, a commutator switch actuated by said second differential in a direction corresponding to the direction of said excessive positional variation, a normally-closed contact for said switch interposed between said rst electrical dierential and said voltage-applying means, and two normally open contacts for said switch, each interposed between an independent source of voltage and said voltage-applying means, whereby said rst differential is disconnected from said voltage-applying means and one or the other of said independent voltage sources connected thereto by said second diierentlal upon excessive positional variation and depending upon the direction of said excessive variation for causing said motor -to control said variable speed power device to drive the controlled member to said predetermined positional variation for assumption of control by said first responsive means.

18. In a system for positioning a controlled member in accordance with a controlling member, the combination of a variable speed power device for driving said controlled member and having a movable control element, a reversible electric motor for positioning said element, an electrical diierential responsive to the degree and direction of a predetermined positional variation between said members for developing a voltage of corresponding magnitude and direction. a pair of thermionic relays having independent plate circuits -for controlling'thedirection of rotation of said'motor, one of said relays being responsive to' voltage in' one direction and the other relay. being responsive to voltage in the opposite direction, means for applying said signal voltage to said relays, for'energiz'ing saidmotor to` position the control element of vsaid vgear to drive the controlled element the corresponding angle and direction linto positional agreement with said controlling member, a second velectrical differential responsive to the direction of a positional variation between said membersl in excess of said predetermined positional variation, a switch actuated by said second differential in a direction corresponding to the direction of said excessive positional variation, a normally closed contact for said switch interposed between said first electrical differential and said voltage-applying means, and two normally open contacts for said switch each interposed between one of said thermionic relays and a, source of voltage of corresponding polarity. whereby said rst differential is disconnected from .said voltage-applying means and one of said voltage sourcesV is con nected thereto by operation of said switch by said second differential upon excessive positional variation between said members and dependingl upon the direction of said excessive variation for energizing said motor to rotate in the corresponding direction for positioning the control element to cause said power device to drive the controlled member to said predetermined positional variation for assumption of control by said first responsive means.

19. In a position control system, a controlling object. a controlled object and means for moving said controlled object substantially in positional agreement with said controlling object comprising means for driving said controlled object and means for controlling said driving means in accordance with the positional disagreement of said controlled and controlling objects and with the first and a higher time derivative of the motion of said controlling object.

20. In a position control system, a controlling object, a controlled object, electrical means for driving said controlled object, means for generating a signal E. M F. having components proportional to the positional disagreement of said controlling and controlled objects and to the rst and a higher time derivative of the motion of said controlling object, and means for controlling said driving means in accordance with said signal E. M. F.

21. In a position control system, a controlling object, a controlled object, means for driving said controlled object, means for generating a signal E. M. F. proportional to the positional disagreement of said controlling and controlled objects, means for generating signal E. M. F.s proportional to a series of time derivatives of the motion of said controlling object, means for combining said signal E. M. F.s, and means for controlling said driving means in accordance with said combined signal E M. F.

22. In an electrical position control, a controlling object, a controlled object and means for moving said controlled object substantially in positional agreement with said controlling object, comprising means for driving said controlled object, means for generating a signal E. M. F. having components proportional to the positional disagreement of said controlled and controlling objects and to the rst'and second time derivatives of the motion of said controlling object and means for controlling said driving means in Vaccordance with said combined signal E M. F.

'23. In a remote position control system for controlling the setting of one element to bea-r a predetermined relationv to another element, a sending element, a responding element, means fory driving said responding element and control means for controlling said driving means in accordance with the lag in the following, and in accordance with the velocity and acceleration of said sending element.

24. In ar remote position control system for controlling the setting of one element to bear a predetermined relation to another element, a sending element, a responding element, means for driving said responding element and control means for controlling said driving means in accordance with the lag in the following, and in accordance with the acceleration of said sending element;

25. In a remote position control system ,for con-- trolling the setting of one element to bear a predetermined relation to another element a sendving element, a responding element. means for vdriving, lsaid. responding element an'd control means for controlling said driving means in accordance with the lag 'in the following, and in accordance' with the velocity and a higher derivative ofthe velocity of said sending element.

GEORGE AGINS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS

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