US2121054A - Apparatus and method for controlling rotation - Google Patents

Description

June 21, 1938. H. A. SATTERLEE APPARATUS AND METHOD FOR CONTRGIJLIIING RQTAT ION 3 Sheets-Sheet 1 Filed NOV. 2, 1936 I7 l6 I9 2961' 29 INVENTOR. (Inward affer/6e. v

BY I A; ATTORNEY.

June ZI, 1938.

H. A. SATTERLEE APPARATUS AND METHOD FOR CONTROLLING ROTATION Filed Nov. 2, 1 936 a Sheets-Sheet 2 1 D.C.-SUPPLY 3 0 AC. SUPPLY POTENTIAL He l 9 I 4 9 MOTOR BACK EMF INVENTOR Hon era l4. affer/ac v Z'I TO EY.

June 21, 1938. A, SATTERLEE 2,121,054

APPARATUS AND METHOD FOR CONTROLLING ROTATION Filed Nov. 2, 1936 3 Sheets-Sheet 3 AQSUPPLY Fla 6 INVENTOR.

Howard SZffcr/ec Patented June 21, 1938 UNITED STATES APPARATUS AND DIETHOD FOR CONTROL- LING ROTATION Howard A. Satterlee, Needham, Masa, assignor to Submarine Signal Company, Boston, Mall, a corporation of Maine Application November 2, 1936, Serial No. 108,852

7 Claims.

The present invention relates to an apparatus for controlling rotation and may be applied to any type of signaling system. where the position of a rotating indicator must be controlled and its indication known from a point remotely situated. This may be applied to a dial telegraphic system or to a system for controlling the positioning of rotatable valves, shafts or the like.

Heretofore where accuracy and smoothness of operation have been an essential factor, such systems have usually been Operated by hydraulic control. However, hydraulic devices are extremely expensive and a cheaper control system is very much desired. While electric motordriven arrangements have also been used, these have not been wholly satisfactory because it has not been possible to control their operation accurately and smoothly. Under certain conditions such systems, unless they have a very high power rating that is far in excess of their nor.- mal needs, often fail when low speeds are used. Furthermore, it has not been possible at reasonable cost to obtain a variable operating speed with full torque at low starting speeds or variable speed with full torque.

According to the present invention there is provided an improved electrical system' for controlling the rotation and position of such means described above. Furthermore, the present invention provides a variable speed device with full torque available at all speeds.

The present invention will best be understood from the following description with reference to the accompanying drawings in which Fig. 1 is a schematic representation of the mechanical elements of the system; Fig. 1a is a plan view of an indicator employed in the system; Fig. 2 is an elevation of an adjustable resistance device which is shown partly in section in Fig. 1 and is employed in the modification shown in Fig. 4; Fig. 3 is an elevation of the control wheel and scale; Fig. 4 is a schematic wiring diagram of one modification of the invention; Fig. 5 shows certain voltage curves illustrating the operation of the system shown in Fig. 4; Fig. 6 shows amodification of the invention; and Fig. '7 shows an elevation of an adjustable resistance device employed in the modification shown in Fig. 6.

In the schematic arrangement shown in Fig. 1 theindicator I is mounted at the end of a shaft 2 in front of a dial 3 rotated by means of the motor I through the reduction gear system 4 and 6, the larger gear 6 driving the shaft 2 at the position of the operators control. Control elements are provided which include a handwheel 8 mounted at the end of a shaft 9. A gear i0 is fixed to the shaft 8 and meshes with a gear ll fixed to the shaft l2. Also fixed to the shaft i2 is a dial [3 the front view of which is shown in Fig. 3. Also fixed to the shaft 9 is a gear I which meshes with gear I! fixed to shaft l6 which carries an inertia mass l'l to prevent too rapid a turning of the handwheel 8. At the end of shaft 9 there is fixed a gear 18 forming part of a differential system which includes also the m idler gear I! and the gear 20. The idler gear carrier is fixed to the end of shaft 2| while the gears 20 and 39 are fastened to each other, but free to revolve on the shaft 2i. At the opposite end of shaft 2| there is 15 mounted a cam 22 carrying the arms 28, 24, whose ends are provided with rollers 25 and 28, respectively, adapted to make contact with resistance windings 21 and 28 wound around an insulating ring as fixed to the support 29a.

An elevation of this variable resistance device is shown in Fig. 2 from which it will be noted that each or the resistances 21 and 28 are circular in shape and extend over approximately ninety degrees of arc. Furthermore, it will be noted 25 that they are so arranged that the roller 25 can make contact only with resistance 21 and that roller 26 can make contact only with resistance 28, stops 30, BI and 32 being provided on the support 29a and on the arms 23 and 24 to limit the rotation of these arms. It will also be noted that the resistances are arranged so that only one of the rollers is in contact with its resistance at a time. Thus, as shown in Fig. 2, while the roller 25 is in contact with the resistance 27, the roller 28 is bearing against the insulating ring 29. This variable resistance serves to control the operation of the gaseous electron tubes 33, 3!, shown in Fig. 4, as will be described later.

Rigidly fixed to the shaft 2 is a gear 5 which meshes with the gear 15 positioned adjacent to it which is driven by the synchronous generator 36. The ratio of gear 6 to gear 35 is the same as that between gears Ill and H, respectively. The self-synchronous generator 38 drives a self-synchronous motor 31 which, through the gears 30. and 39 of a one to one ratio, rotates the arms 23 and 24.

The operation of the mechanical parts of the system just described is briefly as follows: When the handwheel 8 is turned to set the dial it to the desired bearing of the indicator l, the arms 23 and 24 are rotated to cause one of the rollers to make contact with its resistance, thereby operating one of the gaseous electron tubes 33 or 84 in a direction indicated by the setting of the dial it.

The operation of the motor I and its control will be evident from a consideration of Fig. 4. The motor 1 is of the type generally used as a direct current shunt motor. It has an armature 40 and a field winding 4i which, however, is separately excited from a source of direct current.

Its armature 40 is in series with a source of alternatlng current and with the anode-cathode circuit of either of the electron tubes I! or 34 depending upon the position of the relay 4!. The tubes 3! and 84 are three-electrode electron tubes of the gaseous type.

When the moving arm 43 of the relay connects with contact 44 as shown in Fig. 4, the armature 40 is in series with the anode of the tube 33, while when the relay coil 42 is deenergized, its moving arm 43 will be in connection with contact 45, thereby placing the armature 40 in series with the anode of tube 34. It will be noted that when 43 contacts 44. current impulses will flow through the armature 40 in one direction while when 43. contacts 45, current impulses will flow through the ondary winding 48 while the cathode of tube 34 is supplied from the secondary winding ill. The anode circuit of tube 33 is returned to its cathode by means of the conductor Ii which is connected to a center tap on the secondary winding 49. Likewise the anode circuit of the tube 34 is re turned to its cathode by means of the conductor I2 which-is connected to a center tap on the secondary winding 50.

The grid cathode circuits of the tubes 3i! and 34 are energized through the transformer 53 which is supplied from the same source of alternating cur-- rent as the anode circuits. The transformer 53 has a primary winding 54 and two secondary windings I! and 56, each of the latter being provided with a center tap. The grid cathode circuit of the tube II also contains a current-limiting resistor El and a choke 58 in series with the secondary 5!. Likewise, the grid cathode circuit of the tube 34 contains the current-limiting resistor 59 and the choke in series with the secondary winding lit. These elements together with the resistances El and 2!, which are introduced into the circuit by the operation of the arms 23 and '24, form. phase shifting networks for varying the phase oi the grid-cathode voltage with respect to the anode-- cathode voltage of each of the two tubes 33 and 34. As is known, by varying the relative phase between the grid and anode voltages, it is possible to vary the length of time in each cycie during which the discharge tube is conductive whereby the average anode current is varied.

It has been customary, however, to bring about the phase shift of grid voltage progressively in the opposite direction from that of the passage of time as determined by the anode potential, whereas in the present invention the progressive phase shift occurs in the same direction as the passage of time. 'Also, in the present arrangement the anode circuits contain the armature oi the shunt motor 1. When the armature revolves, a back E. M. F. will be developed in its windings which will oppose the applied alternating voltage during one half of the cycle and will aid it during the other half of the cycle. Furthermore, the back E. M. F. will oppose the alternating voltage during that portion of the cycle in which one of the diswe assume that the arms 23 and 24 of the variable resistance are in such a position that they both contact only the insulating ring 29, which would be in a vertical position in Fig. 4, the alternating potential applied to the grid of each tube will be degrees out of phase with the anode potential of that tube as indicated by the curve E91. 9

The anode voltage is illustrated by the curve Ep. Since in order for either tube to discharge, it is necessary that the grid voltage be above a certain minimum, which we may assume for the purpose of this discussion to be zero volts, it will be evident that neither tube can discharge under these conditions, and consequently the motor I will remain at rest.

If, now, the handwheel be turned so that one of the arms makes contact with its resistance, say, as shown in Fig. 4, so that the arm 23 makes contact with resistance 21, the contacts 48 and 41 will be closed by the cam 22 and consequently the relay coil 42 will be energized closing contacts 43 and 44 and opening the anode circuit to the tube 34. Under suitable conditions, tube 33 can then operate, while tube 34 is isolated from the circuit. The alternating potential which is now applied to the grid of tube 33 is less than 180 degrees out oi phase with the anode potential of that tube as indicated, for example, by the dotted curve Eon. Let us assume that the minimum anode potential required to effect a discharge of the tube is the value a, as indicated by the line Ep(minimum). It will now be seen that in a positive half cycle of anode voltage, as indicated by the curve Ep, when the anode voltage reaches the value a, the grid voltage EU: is still positive. .At this point, therefore, the discharge will take place and anode current will flow through the armature 40 to the end oi the positive half cycle when the anode voltage again becomes negative. In the latter condition the tube cannot, of course, conduct current since it is a uni-directional device, but in the succeeding positive half cycle, the same effect will again occur. The armature 40 will, therefore, be energized with unidirectional current impulses causing it to rotate.

As the armature gains in speed, a back E. M. I". wil be generated. Now it will be noted from Fig. 5 that at the instant the anode voltage reaches the value b, the grid voltage E92 has reached zero. Therefore, the back E. M. F. can increase until it has the value -(b-a), for if it becomes greater than this, no further current 75 impulses will be supplied to the motor armature, wherefore its speed will decrease. This is because a back E. M. F. of the value (b-a) is'sumcient to reduce the anode voltage to its minimum permissible value at the instant the grid voltage reaches, its minimum value so that no discharge of the tube occurs. If, now, the arm 23 were turned still further in a clockwise direction, the grid voltage curve Egz would be displaced still more to the right in Fig. and consequently the back E. M. F. and therefore also the speed of the motor could build up to a higher value than previously.

It should be noted that the progressive phase shift of grid voltage with respect to anode voltage in starting the motor is in the same direction as the passage of time as determined by the anode voltage, as shown in Fig. 5. This is made possible by choosing the correct polarity for the primary of transformer 53, and results in the application to the motor of maximum power. The motor consequently develops maximum torque on starting.

From the above it will be evident that the tube 33 with the phase shift control of its grid voltage in combination with the shunt motor 1 offers an arrangement for obtaining a variable motor speed with full torque at starting which obviously may be useful in a number of instances other than the example herein given. It is particularly useful where the inertia of a heavy mass must be overcome in order to set it in motion.

Referring again to Fig. 4 it will be evident that when the arm 24 makes contact with the resistance 28, the contacts 46, 41 will be opened and contacts 43, 45 closed, whereby the tube 34 becomes active to rotate the armature 40 in the reverse direction from before. The control of the potential of the grid of tube 34 is similar to that described with reference to tube 33 and the back E. M. F. generated in the armature of the motor likewise brings about an automatic limitation of the motor speed. The system as described, therefore, not only provides a motor speed control, but also: provides this control for both directions of rotation.

In the system as applied to the rotation of the shaft 2 of the remotely controlled indicator shown in Fig. 1, it will now be understood that when the handwheel has been rotated to set the dial l3 in a given position which may result, for

example, in setting the arm 23 on the resistance 21, as shown in Fig. 4, the motor 1 will operate to rotate the indicator. i into the desired direction. At the same time, however, the self-synchronous generator 36 is being rotated and is effecting a rotation of the self-synchronous motor 31, whereby the arm 23 is again moved back to its original position, making contact with the insulating ring 29, at.,which time the grid voltage of tube 33 will again be exactly 180 degrees out of phase with its anode voltage so that current can no longer flow through the motor armature which consequently will cease turning.

Should the inertia of the parts be such that the motor will revolve the indicator beyond its desired position, the self-synchronous motor 31 will likewise rotate the arms 23, 24 beyond the insulating segment 29 so that the arm 24 makes contact with the resistance 28 and also the cam 22 will be rotated, causing the contacts 46, 41 to open and thereby deenergizing the relay 42 which permits contacts 43, 45 to close. The tube 34 is, therefore, then energized to rotate the motor in the reverse direction to bring the indicator back into the desired position.

It should be noted that the resistance 21 or 28) is varied from an infinite to a finite value at the very first turning of the handwheel from its position of rest. Upon continued turning of the handwheel, the resistance is finally gradually reduced to zero.

In many systems in which the present device is employed maximum starting torque is desired and this is obtained in the present system. Since maximum torque is developed by the motor while the resistance is near its maximum finite value, as explained above, it is highly desirable to place a limitation upon the speed with which the handwheel is turned so as to give the motor time to set the indicator into rotation while maximum torque is still available. This is the function of the inertia weight i1 shown in Fig. 1, although other suitable devices may be substituted for limiting the speed with which the handwheel can be turned particularly at starting.

0n the other hand, the resistances can be tapered or arranged in steps of any desired magnitude in order to obtain any desired speed at the various settings of the resistance control arm. It may, for example, be desired to have the motor rotate extremely slowly near the position of balance and when the handwheel is only very slightly displaced while much faster rotation is to occur when the handwheel is displaced a greater amount. For this purpose the resistance variation is made small near the position of balance and is made to reduce rapidly for greater displacements of the resistance arm.

The handwheel 8 need, of course, not be manually operated, but it can be controlled by an automatic device, such as, for example, a gyrocompass in order to keep the device I facing in a desired direction.

The system shown in Figs. 6 and 7 is in many- .ways superior to the arrangement shown in Fig.

4. The modified arrangement is considerably simpler inasmuch as one of the transformers and the chokes is eliminated. Furthermore, a very smooth control of the indicator or of speed variation'can be obtained.

In Fig. 6 the motor! is likewise of the directcurrent shunt motor type having its field winding 62 separately excited from a direct-current source. The gaseous electron tube 63 has its anode-cathode circuit supplied with alternating current and contains the armature SI of the motor 1 in series with it. A relay 65 is provided which is a double-pole, double-throw relay and serves to reverse the connections of the armature 6| of the motor I. The potential applied to the grid of the tube 53 is obtained from the direct current source through the current-limiting resistor 64 and the variable potentiometer resistances 10 or II. These resistances may be uniform or tapered or stepped as mentioned above with respect to the resistances 21 and 28 of Fi 4.

A convenient mechanical form of the latter is shown in Fig. 7. This variable resistance is mounted on the shaft 2| in Fig. 1 in place of the device there shown and described in connection WithFig. 4. The contact arm 51 normally makes contact with a conducting segment 68 mounted upon a suitable disc of insulating material 69.

-On either side of the segment 68' are the resistances l0 and 1| with which the arm 61 makes contact when it is moved to one side or the 7 other 01' segment 88. A cam 12 is also provided fixed to the shaft 2| so that it rotates with the arm 01. The cam 12 is arranged so that the contacts ll, 14 are open when the arm 61 engages the segment 88 as well as while it engages the resistance II. On the other hand, the contacts II, ll are closed while the arm 61 engages the resistance 10. When the contacts 13, ll are closed, the coil I5 of the relay 65 is energized Irom the direct current supply, thereby connecting the armature Si in the anode-cathode circuit of the tube in one direction"; but when contacts 13, H are open, the relay coil is deenergized and the armature is connected in the anode circuit in the reverse direction. Since current always flows through the anode circuit in the same direction, the motor armature will rotate in one direction or the other, depending upon whether the arm 61 is in contact with the resistance Hi or with the resistance".

The outer ends of the resistances and II are both connected to the positive side oi the source of direct current while the inner ends, namely those adjacent to the segment 88, are connected together and through a high resistance to the segment 58 and thence through the resistance I5 to the cathode of tube 63. The inner ends of the resistances l0 and ii are also connected to the negative side of the source of supply through the resistance 11. The grid cathode circuit of the tube thus can be traced from the grid of the tube through the resistance 64 to the arm 61. Then when the arm is in contact with segment 88, the circuit continues through resistances l1 and 16 to the cathode, and when the arm is in contact with the resistances 10 or H, the circuit continues through a portion of the respective resistance to the resistance l6 and the cathode of the tube. It will be noted that the resistances l0 and ii are each potentiometers connected across a source of direct current, their outer terminals being positive and their inner terminals negative. Thus, as the arm 61 is moved outward. away from the segment .8, along either of the resistances 10 or H, the grid of tube 63 becomes more and more positive with respect to the cathode.

As soon as the grid of tube 63 becomes positive, the tube will become conductive and unidirectional current impulses will flow in the anode circuit through the armature 6i causing it to rotate. The rotation of the armature in the direct current field produced by the winding 82 causes a back E. M. F. to be induced in the armature winding. The armature, it will be noted, is connected through the conductors T8 and 19 across the terminals of the resistance 16 which is in the grid cathode circuit as above described. The back E. M. F. is thus impressed across this resistance and is in the opposite direction to The grid cathode potential supplied through the resistance 10 or H. As the armature 6! speeds up under the influence of the anode current, the back E. M. F. builds up to a greater and greater value until it is suiiiciently high to neutr'alize the grid potential supplied through the resistances Hi and ii and thereby cause the grid potential to fall below the critical potential and consequently to cut off conduction through the tube. Thereupon the armature iii, no longer being supplied with current impulses, to slow down and the back E. M. F. conseouently decreases to a point where it is no longer cient to neutralize the applied positive grid po tential whereupon the tube again becomes com ductive. This phenomenon is repeated and results in the armature attaining a constant speed determined by the setting 0! the arm 61 along the resistance 10 or II. It will be evident that not only at starting but also at all speeds Iull torque is available, the armature being supplied with current impulses just suflicient in number to keep its speed at the value determined by the setting of the resistance 86 and the back E. M. F. developed by the armature.

As applied to the rotation of the indicating device, it has already been mentioned that the arm 81 is to be fixed to the shaft 2| of Fig. 1. Thus, when the handwheel 8 is displaced in order to change the position of the indicating device I, the arm 81 will be moved onto one or the other of the resistances 10, ii and will be moved along the resistance by an amount depending upon the amount of change of position which is desired as indicated on the dial coupled to the handwheel 8. The subsequent rotation of the motor I in turning the indicating device into the desired position also brings about the rotation of the self-synchronous generator 36 and the self-synchronous motor 31, which through gears 38 and 39 operates to return the arm 61 toward" the segment B8 which will be reached when the indicating device has been rotated into the proper position. When this position is reached, the motor stops.

Since the motor speed is dependent upon the position of the arm 61 on the resistance 10 or H as explained above, it will be understood that as the indicating device approaches the desired position and consequently as the arm 6! approaches the segment 88, the motor speed gradually reduces, so that the indicating device comes to a smooth stop. There is substantially no tendency for it to overshoot the desired position. although if it should do so, the motor will reverse at slow speed to return to the correct position. Extremely accurate settings can be made with the added advantages of high Speed for large position changes, low speed for small changes, full torque at all speeds; and at the same time the apparatus required is simple, resulting in low manufacturing and maintenance costs.

The arrangement shown in Fig. 4 employs two tuba, but it is evident that one of these may be dispensed with by replacing the relay l2 with a double-pole, double-throw relay arranged in a manner similar to that shown in Fig. 6.

While my invention has been described chiefly as applied to a system for a remote control or controlling an indicating device, the system is also applicable for obtaining variable speed drive. As such, it can readily be applied to the operation 01 machines at desired variable speeds. In this case it will be understood, or course, that the coupling between the moved device and the resistance device represented in Fig. l by the selfsynchronous machines lit and iii and the attendant gearing can be omitted. lit will also he evident that any desired uence of fast or slow operation ci'in readily he obtained by suitably proportioning the steps into which the resistance means are divided and the manner in which the ccntacting arm. is moved. over thorn.

Having now described my invention, I claim:

it. idystem tor controllin the speed of motor immersed in a continuous when in motion to gcrerate a heel"; E. M. ii eluding iii tl1ree-electro gasecus electron tube having anode and grid circults, means for connecting said armature in circuit with the anode of said tube. means for applying operating alternating potentials to the grid and anode of said tube, means for varying the phase of said grid potential with respect to the anode potential in accordance with the desired speed, the variation being to make the grid potential more leading for decreased speed, means for opposing said anode potential with said back E. M. F. and means operatively connected to said grid potential control means for reversing the direction of fiow oi current through said armature.

2. System for controlling the position of a body including a motor operatively connected to said body to change the position thereof, said motor having an armature immersed in a continuous magnetic field and adapted when in motion to generate a back E. M. F., a three-electrode gaseous electron tube having anode and grid circuits, means for connecting said armature in "circuit with the anode of said tube, means for applying operating alternating potentials to the grid and anode of said tube, means for varying the phase of said grid potential with respect to the anode potential in accordance with a desired change in position of said body, the variation being to make the grid potential less leading for a greater desired change of position, means for opposing said anode potential with said back E. M. F. and means operatively connected to said body and adapted upon motion of said body to vary said grid potential in the opposite sense to its original variation.

3. System for controlling the position of a body including a. motor having an armature immersed in a continuous magnetic field, a pair of three electrode gaseous electron tubes, means for applying alternating potential to the anodes of said tubes through said armature, means for supplying alternating potential to the grids of said tubes normally in opposite phase relation to said anode potential and means for bringing the grid and anode potentials of one tube more nearly into phase with each other in such a mannerthat the in-phaserelation is approached with the grid potential leading, whereby energization of said armature to set it into rotation results.

4. System for controlling the position of a body including a motor having an armature immersed in a continuous magnetic field, a pair of three electrode gaseous electron tubes, means for applying alternating potential to the anodes 01 said tubes through said armature, means for supplying alternating potential to the grids of said tubes normally in opposite phase relation to said anode potential, means adjustable in accordance with a desired change of position of said body as: bringing the grid and anode potentials of one tube more nearly into phase with each other in such a manner that the in-phase relation is approached with the grid potential leading, whereby energization of said armature to rotate it results, and means operated by said motor for returning said adjustable means to its normal position, whereby said motor is stopped.

5. System for controlling the speed of a motor having an armature immersed in a continuous magnetic field and adapted when in motion to generate a back E. M. F. including a gaseous electron tube having anode and grid circuits,

means for connecting said armature in circuit with the anode oi said tube, means for applying operating alternating potentials to the grid and anode of said tube, means for varying the phase of said grid potential with respect to the anode potential in accordance with the desired speed, the variation being to make the grid potential more leading for decreased speed, and means for opposing said anode potential with said back 6. System for controlling the position of a body including a motor having an armature immersed in a continuous magnetic field, a pair of gaseous electron tubes, means for applying alternating potential to the anodes of said tubes through said armature. means for supplying alternating potential to the grids oi. said tubes normally in opposite phase relation to said anode potential, means adjustable in accordance with a desired change of position of said body for bringing the grid and anode potentials of one tube more nearly into phase with each other in such a manner that the in-phase relation is approached with the grid potential leading, whereby energization of said armature to rotate it results, said adjustable means being arranged to produce a greater proportion of phase variation with a large desired change of position than with a small desired change of position, and means operated by said motor for returning said adjustable means to its normal position, whereby said motor is stopped.

7. Method of operating at variable constant speed a motor of the direct current type having an armature immersed in a continuous magnetic field by means of a gaseous electron tube which comprises supplying an alternating potential to the anode of said tube through said armature in a series relation, supplying an alternating potential of the same frequency to the grid of the tube in an out-of-phase, leading relation to said anode potential, opposing the back E. M. F. of the motor against said anode potential and varying the phase of the grid potential with respect to the anode potential to make it less leading with respect to the latter for increased speed.

' HOWARD A. SATI'ERIEE.

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