Patent GB-621802-A (GB)
Title: Improvements in and relating to correspondence control systems for movable members
IPC: G08C19/38
Filed: 1946-06-11
Abstract: 621,802. Automatic speed control systems; excitation of dynamo-electric machines. PESTARINI, G. M. June 11, 1946, No. 17449. [Classes 35 and 38 (iv)] [Also in Group XXXVIII] In a system for maintaining the motion of a power-driven controlled member in correspondence with that of a controlling member, the control means comprise a D.C. wound armature having a commutator co-operating with a set of brushes, and a magnetic field system, the field axis being displaceable with respect to the brush axis according to the differential displacement of the controlling and controlled members. The brushes are rotatable by the controlled member and the field by the controlling member or vice versa. A voltage developed across the brushes is dependent in sense and magnitude on the non-correspondence between the members and controls the driving means of the controlled member to restore correspondence. The armature is stationary or rotated at constant speed, according as velocity or positional correspondence control between the members is required. Fig. 1 shows a system wherein the controlling member 21 turns the rotor of transmitter 20, the multi-phase wound stator of which supplies currents rotating in phase according to the transmitter rotation to the similar stator 18 of a receiver 16 having a D.C. energized rotor 17 which turns the D.C. supplied brushes 12, 13 about the commutator of the fixedly mounted D.C. armature 8 in correspondence with the movement of the controlling member. The armature field 10 is D.C. energized and is rotated. about the armature by the drive motor 1 of the controlled member which motor field 3 is energized by metadyne 4 controlled by winding 5 energized through slip rings 25 by the D.C. voltage appearing across the brushes 12, 13. When the controlled and controlling members and consequently the field and brushes of armature 8 rotate asynchronously, a D.C. voltage is induced across brushes 12, 13 energizes the metadyne control winding 5, to excite the field winding 3 in such a direction as to alter the speed of motor 1 until the controlled and controlling members are in synchronism, when the D.C. voltage across the brushes falls to zero. The controlling member may be directly coupled to the brush holder, and a field winding 7 of the metadyne 4 may be energized at constant voltage to produce a steady motor excitation on which the control excitation is superimposed. The armature 8 may be rotated at a constant rate by motor 26 to produce a control voltage component independent of the rotation of the field 10 so that correspondence control may be obtained when the controlling and controlled members start from rest. In a modification (Fig. 2, not shown), the exciter machine is inverted. Fig. 3 shows a modification in which the transmitter 20 operated by controlling member 21 produces multi-phase currents in the stator windings 18 of the receiver 16 whose rotor 17 rotates the brushes 12, 13 about the commutator armature 8 driven at constant speed by motor 26 in the fixed D.C. field 10. Shaft 11 is driven by the controlled member in the opposite direction to the initiating movement of the controlling member so that when the controlled and controlling members move in correspondence the resultant stator field and consequently the rotor remain stationary in space, so that there is not rotation of the brushes out of the axis of field 10, and no D.C. voltage developed across the brushes to control the excitation of motor 1. Non-correspondence between the controlling and controlled members causes the field of stator 18, and therefore the rotor 17, to rotate in space, thus displacing the brushes 12 and 13 with respect to the axis of field 10 and so developing a brush voltage which controls the motor excitation to restore correspondence between the controlling and controlled members. In the modifications of Figs. 4, 5 (not shown), the rotating stator field derived from the controlling member constitutes the field of the armature, combined with the synchronous receiver, which is rotated by the shaft of the controlled member in the opposite direction to the rotation of the controlling member. The armature may be fixed to the stator, or rotated at constant speed by a motor, accordingly as velocity or positional correspondence control is required. In the modifications of Figs. 6, 7 (not shown), the polyphase currents operating the receiver are supplied by an " Amplidyne " (Registered Trade Mark) machine of the kind described in Specification 406,759, the armature or brushes of which are rotatable by the controlling member. Fig. 8 shows a modification in which the controlling member 21 rotates the polyphase transmitter rotor 40 in the field of the polyphase stator 42 energized from a constant frequency source 44 which also energizes the polyphase stator 18 of the receiver 16, which stator is rotated by the controlled member shaft 11. The output of rotor 40 is connected to polyphase rotor 17, which drives the brushes 12, 13 of armature 8, which is rotated in D.C. field 10 by constant speed motor 26. The polyphase current supplied to the rotor windings of receiver 16 is 'of frequency equal to the sum of the source frequency and that corresponding to the velocity of the controlling motion so that the resultant field in the receiver rotates in correspondence therewith. When shaft 11 rotates in correspondence with the controlling member, the resultant field is stationary in space and the rotor 17 is also stationary, but when non- correspondence exists between the members, the rotor turns the brushes 12, 13 out of the field axis of armature 8, developing a direct voltage across the brushes which controls the drive motor. In a similar modification (Fig. 9, not shown), the rotating field of the receiver stator constitutes the armature field, as in Fig. 4, the armature being fixed to the receiver, which is rotatable by the shaft of the controlled member, while the brushes are rotatable by a synchronous motor driven from the constant frequency source, non-correspondence again developing a direct voltage across the brushes which controls the drive motor. In Fig. 10 (not shown), the controlling member drives a polyphase rotor, energized from a constant frequency source, and in the field of a D.C. energized stator carried by a rotating cage member supporting the D.C. supplied brushes of the amplidyne system of Fig. 7, so that the frequency of the polyphase output currents at 72 is the sum of the source frequency and the frequency corresponding to the velocity of the controlling member. The application of the system to the control of a gun from a tracking sight is described.