Patent GB-609305-A (GB)
Title: Improvements in and relating to follow-up control systems
IPC: G05D3/14
Filed: 1941-10-01
Abstract: 609,305. Electric control systems. TUSTIN, A., MORRIS, D. G. O., and METROPOLITANVICKERS ELECTRICAL CO., Ltd. Oct. 1, 1941, No. 15437/42. Divided out of 609,296. [Class A positional control system comprising means responsive to relative displacement of a load and a control member for providingA.C.,dependent in amplitude and phase on the extent and direction of the displacement, which is rectified by a dryplate rectifier circuit and used to control the torque applied to the load, comprises also means tor advancing tne phase of the alternating components in the torque with respect to corresponding components in the output of the rectifier circuit. The phase advancing arrangements may be as described in Specification 609,304 or they may comprise a phase advancing metadyne or an electro-mechanical arrangement in co-operation with moving coil relay, controlling the torque of an electric motor. The dry plate rectifying arrangements described in Specifications 527,768 and 604,185 may be utilized. The alternating current dependent on the displacement is provided by coarse and fine selsyn systems 1, 6, the transmitters 2, 7 being controlled, for example, by hand-wheel 3 and the receivers 10, 11 being coupled by gearing 4, 8, with the load device (not shown) driven by D.C. motor 17. Voltages due to displacement are taken from windings 15, 16 and applied to a rectifying arrangement hereinafter described, the coarse system being in operation for large displacements which cause operation of relay 36, followed by relay 34 to connect winding 15 to the rectifiers. The output of the rectifiers, smoothed by condenser 39 is applied to the primary brushes of metadyne 25, operating as an amplifier, in series with a primary variator winding 38. The secondary brushes are connected to the variator winding 40 of a phase advancing metadyne 41 arranged as shown or otherwise as described in Specification 592,209 and controlling the main metadyne 18 which supplies the armature of D.C. motor 17. When the displacement is reduced, relay 34 relapses to connect the winding 16 of the fine system to the rectifiers. In a modification using mechanical means for advancing the phase, the rectified output is applied to the moving coil 100, Fig. 2, of a relay having a pot magnet energized by a D.C. winding 102. The coil is biassed to the central position by springs 103 and a disc 104 in a damping cylinder 106 to provide substantially dead beat operation of the moving coil which is connected by a phase-advancing linkage to a pressure sensitive controller 107 in circuit with the centre tapped winding 112 of, e.g. a main metadyne controlling the driving motor, the winding arm controller being energized from a D.C. source 113, 114. The phase advancing means comprise a floating lever 117 connected between rod 105 of the moving coil and rod 115 which moves the controller, the end of the lever remote from the moving coil being provided with damping 121 and mass 123 greater than the corresponding components operating on the moving coil to provide an advance in phase of the movement of controller 107 with reference to the movements of the coil 100. Rectifying arrangements. Four rectifier squares I-IV receive input from the output terminals 29, 30 of the selsyn system which output is in phase or counterphase with supply 12 in accordance with the direction of the displacement to which the system responds. The rectifier squares are supplied from 12 with A.C., across the diagonals not connected to the input, by transformer 23 having secondaries wound so that the voltage across i, iv are in counterphase with those across ii, iii. During one half-cycle of supply 12, current flows in one direction or the other depending on the phase of the input, from rectifier I over metadyne 38 returning over rectifier IV, whereas during the other half-cycle corresponding operation over rectifiers II and III occurs. The arrangement therefore provides full-wave rectification and the direction of the output depends on the phase of the input and therefore of the direction of displacement.