Patented Nov. 5, i946 2,410,599 UNITED STÀTES PATENT OFFlClï.` 2,410,599 REMOTE CONTROL SYSTEM James W. Conklin, Indianapolis, Ind., assignor to ' Radio Corporation of America, a corporation of ~ Delaware Application February 24, 1943, Serial No. 476,902 4 Claims. ( c1. 172-239) >l 2 an angular position corresponding to that to tems of the follow-up type and more particularly which it is desired to operate the driven device 3. to the prevention of operation of the control Alternating current is transmitted through .the member of such systems at a rate exceeding the cascaded synchro transformers 5 and 9 to the maximum speed capability of the driving motor. input circuit of the amplifier l.V The amplitude The usual servo system comprises a control input of the input voltage to the amplifier 1 is directly shaft, an -output shaft, means for producing con- proportional lto the difference in the angular po trol voltage related in some predetermined man sitions of the rotors of -the transformers 5 and 9. ner to the difference in the angular positions of This voltage is amplified and is applied to the 'saidshaits and a driving motor controlled by motor I, driving the output shaft, and with it the said voltage to reduce said difference to zero. device 3 to Vsuch a position that .the rotor of `the Upon rotation of the control shaft, the driving transformer 5 corresponds in angular position motor will operate the output shaft at the same with the rotor of the transformer 9. When this rate, with an angular lag depending on the con condition is attained the voltage applied to the stants of the system. In general, this lag in 15 input circuit oi the ampliiler "i is zero, and the creases with increase in speed of operation ofthe motor I is deenergized. control member. As the maximum speed capa Ordinarily, the driving motor is of the induc bility of the driving motor is approached, the lag tion or repulsion type, and hence cannot operate increases more rapidly andthe driven shaft final above a predetermined speed, corresponding to _ ly falls out of synchronism with the control shaft. ~ the synchronous speed. This speed depends upon The principal object of the present invention is construction o1' the motor and upon the frequency to provide an improved method of and means for of the A.-C. supply. As mentioned above it is un limiting the rate of operation of the control mem desirable >to operate the control shaft at a speed ber of a servo system to prevent operation of the approaching the synchronous speed of the driving control at a rate exceeding the capabilities of the 25 motor because of the resultant increase in lag, and driven device. ' the possibility that the driven shaft may fall out Another object is to provide an improved of step with the control member. Accordingly, method of and means for limiting the angle of an A.~C. motor I3 is mechanically coupled to the lag of the output shaft with respec-t to the con control shaft and electrically connected to Ithe 30 output of the synchro transformer 5. The cou trol shaft. - ~ ‘ _ A further object is to providelimproved means pling between the motor I3 and the rotor of the for controlling the speed of operation of the con control transformer 9 includes gearing I5, so de trol input shaft of a servo system in response to signed that the synchronous speed of the motor the angular displacement between the input and I3 will occur at a speed of rotation of .the control output shafts. These and other and incidental " member I I which is somewhat less than the syn objects will become apparent to those skilled in chronous speed of the driving motor I. In -the the art upon consideration of the following de normal operation of the system the output volt scription with reference to the accompanying age of the transformer 5 is of the order of1 per drawing which ls a schematic circuit diagram of ' cent of the A.-C. supply voltage. This voltage, a servo system embodying the present invention. 40 when applied to the motor I3, will produce sub-y An A,-C. motor I is mechanically connected to stantially no effect. However, when the angular the load device 3, and to the rotor of asynchro lag between the rotor of the transformer 5 and transformer 5. The rotor o1' the transformer 5 . that of the transformer 9 4approaches 90°, the is electricallir connected to an amplifier ‘I which output of the transformer 5 increases to a value is connected to the input circuit of the~ motor I. 45 of the same order of magnitude as the supply ~ "The stator winding of the transformer 5 is elec voltage. If, at the same time, the speed of ro trically connected to the stator windingof a sec tation of the motor I3, due to »the operation of ond synchro transformer S. The rotor winding the control input device I I, is substantially equal to the synchronous speed of said motor, a strong of the transformer 9 is connected to an A.-C. supply. not shown. The rotor of the transformer 50 synchronizing torque is developed which effec â is mechanically coupled to a control device tively resists any increase in speed. By the proper such as a manually operable crank -I I. selection of gear ratios, this condition can be The system as thus far described constitutes caused to occur at any preselected >speed oi' the ’I’his invention relates to electrical servo sys a conventional servo system of the follow-up type. ' In operation, the control member II is moved to 55 driving motor I. Thus the invention has been described-as an l 2,410,599 improved electrical servo system of the follow-up type, including means for preventing the opera tion of the control input member at a rate greater than a predetermined fraction of the synchronous speed of the driving motor. This is accomplished by coupling an auxiliary A.-C. motor to the input shaft, and connecting said motor to the electrical control channel ofthe system. The arrangement is such that the auxiliary motor reaches syn chronism at a lower speed of operation of the control shaft than the driving motor. At syn chronous speed of the auxiliary motor, a strong lock-in torque is developed, effectively preventing any further increase in speed. I claim as my invention: ‘ f 4 predetermined manner to the difference in the angular positions of said shafts, a motor coupled to said control shaft and connected to respond to said control signal so as to prevent operation of said control shaft at a speed exceeding the maxi mum speed of said driving motor. 3. A servo system comprising a driving motor, an output shaft coupled to said motor, a synchro transformer coupled to said output shaft, an am pli?ier connected between the rotor winding of said synchro transformer and said driving motor, a second synchro transformer with its stator vwinding connected to the stator winding of said first synchro transformer and its rotor coupled to 15 a control shaft, a source of A.-C. energy con i. A remoto control system including a driven nected to -the rotor winding of said second syn shaft, a control shaft, means for deriving an chro transformer, and -an A.-C. motor coupled to A.-C. control voltage proportional in amplitude said control shaft and connected to the rotor of to the difference in the angular positions of said said first synchro transformer. shafts, a control member ‘connected to said con 20 4. 'I'he invention as set forth in claim 3 where -trol shaft and to an A.-C. motor. and means for in said A.-C. motor is coupled to said control shaft applying said A.-C. voltage to said motor so' as in such a manner that .the rate of rotation of said .to prevent operation of said control member above A.-C. motor is a greater fraction of the synchro a predetermined speed. nous speed of said motor than the speed of said 2. In a remote control system of the follow-up driving motor is of the synchronous speed of said type. `comprising -a driving motor, a load shaft driving motor. » `connected to said motor, a control shaft and means for deriving a control signal related in a w ÀJaimes w. coNKmN.