Patent GB-579056-A (GB)
Title: A system for the electrical transmission of correspondence control and torque
IPC: G05D3/12
Filed: 1943-06-29
Abstract: 579,056. Telecontrol systems. HODGKINS, H. W. HASTINGS-, and KINETOURS, Ltd. June 29, 1943, No. 10523. [Class 40 (i)] [Also in Groups XXXV, XXXVII and XXXIX] The receiver of a telecontrol system which operates in response to the difference between two signal frequency nal frequencies or between a sig- and the frequency of a locally generated current comprises a pair of motors fed with the respective currents and having their stators (or rotors) geared together directly so that they rotate in opposite directions at the same speed and the rotors (or stators) coupled for rotation in the same direction by a gear wheel on a shaft coupled to the object to be controlled. 'This shaft thus remains stationary when the two frequencies are the same and rotates in one or other direction when they are different at a speed depending on the difference. The system may be used for controlling guns or for operating the controls of crewless ships and pilotless aircraft, means being provided in some cases for the reflection of the load so that the operator appears to feel the resistance of the distant control surface &c. Wired system, Fig. 1. The control handle 13 operates on sliders 9, 10 to vary in opposite directions the value of resistances 7, 8 in the armature circuits, and therefore the speeds of repulsion motors 1, 3 driving three phase alternators 2, 4. At the receiver, the field systems 15, 17 of two synchronous motors necessarily rotate at the same speed but, when the received frequencies differ, the armatures 14, 16 rotate at appropriate speeds and the shaft 73 of the controlled object rotates at a speed depending on the difference. An identical receiver F at the transmitting station drives the bodies of the resistances 7, 8 to bring the speeds of the motors 1, 3 into agreement again when a movement at the receiver corresponding to the movement of the transmitter handle has taken place. Radio systems. In one system, Fig. 2 (not shown), a single control frequency is transmitted and, by means described in a separate paragraph, controls the speed of a repulsion motor and therefore the frequency of the current supplied to one of the synchronous motors of the receiver pair. The frequency of the supply to the other motor depends on the position of the controlled object which is thus driven until the locally generated frequency is the same as the received frequency. In another system, Fig. 4, described more fully below in connection with the reflection back of the load to the receiving station, the movements at the receiver are signalled back to a follow-up device at the transmitter. In other systems, Figs. 6 and 7 (not shown), receiver units for the control and tell-tale systems are used in which one or both of the motors is itself a repulsion motor controlled to run at a speed depending on the received frequency instead of a synchronous motor driven by an alternator coupled to such a repulsion motor. In another system, Fig. 9, the receiver comprises two repulsion motors, one, 76, controlled to run at a speed depending on the incoming frequency and the other, 77, run at a speed depending on the position of the controlled object. This motor also drives an inductor alternator which sends a pulse at a position in the cycle that depends on the position of the stator to control cathode beam indicator 86 at the transmitter. Modified transmitting arrangements. Instead of motor generator sets, mercury arcs can be used as generators or frequency converters. A further alternative is shown in Fig. 8 in which inductor alternators have their rotors geared together directly and driven by a motor 83 and their stators coupled via a gear wheel on the shaft of the transmitting handle. It is also pointed out that the arrangement shown in Fig. 1 is reversible since any movement of 21 causes an increased load on one of the motors 1, 3 and a reduced load on the other. Reflection back of load to transmitting station. In the arrangement shown in Fig. 1, the effect of a load is reflected by the behaviour of the motors F and this can be communicated to the operator's hand by coupling the sliders 9, 10 to the body of the control resistances by springs. In a radio system, Fig. 4, a similar effect is produced by sending back signals corresponding to the speeds of the alternators 37, 39 driving the receiver motors 40 to control a similar pair of receiver motors 71. These motors drive an H-shaped framework carrying one part of a permeability tuner the other part of which is coupled to the control handle. The frame thus follows up the handle as the distant apparatus moves and the feel of the resistance is communicated to the operator by coupling the handle to the frame by springs 50, 51 as shown. Motor-control arrangements-braking. Fig. 3 shows a circuit for keeping the speed of a repulsion motor 25 constant at a value determined by the frequency of an incoming signal. The windings of an inductor alternator 32 coupled to the motor are associated as shown with the circuit to which the control signal is applied and with a rectifier bridge 33 and a resistance 34 biassing a tube 35. When the incoming frequency and that generated by 32 are the same, the system is stable. When any difference arises, the bias on the tube 35 changes and the current through the control winding of a saturable choke 36 in the armature circuit of the repulsion motor changes correspondingly to vary the speed of the motor. In another arrangement, Fig. 5 (not shown), the armature circuit is controlled directly by a discriminator circuit in accordance with the incoming frequency. Braking may be given (a) by making the repulsion motor brushes wider peripherally than usual (b) by the provision of brake discs forming part of the magnetic circuit of a pair of stator poles and coming into action when the rotor flux is reduced by the action of the control units described above (c) by the provision of an extra pair of brushes 92 on the "reverse" side of the neutral axis of the commutator connected to a separate saturable choke 91 controlled by another tube 90 as shown in Fig. 10.