GB639537A - Improvements in and relating to follow-up electric control systems - Google Patents

Abstract

639,537. Electric control systems. BRITISH THOMSON-HOUSTON CO., Ltd. (General Electric Co.). May 1, 1946, No. 13183. [Class 40 (i)] In a follow-up control system, means responsive to positional disagreement between a driven object 10 and a pilot device 11 are provided for producing a signal voltage which causes a motor 12 to drive the object into positional agreement with the pilot device, anti-hunting means being provided which is responsive to positional disagreement above a predetermined amount for reducing the signal voltage and hence the synchronizing torque of the motor. The energization of the motor 12 from the supply 20 is controlled by valves 14, 15, the grids 14a, 15a of which may be supplied through an input transformer 26 with a signal voltage from Selsyn motors 28, 11 the latter forming the pilot device. For preventing hunting during normal follow-up operation of the system, a capacitor 31 is connected to the grids 14a, 15a in series with stabilizing resistors 25, 27 and is supplied with a voltage proportional to the speed of motor 12, i.e. from a tachometer generator 32 driven by said motor so as to modify the signal voltage in accordance with the rate of change of speed of motor 12. Should the speed of motor 12 exceed a predetermined amount, such as may occur when the system is switched on with a large positional disagreement between the object 10 and pilot device 11, further antihunting means are brought into action comprising gas containing triode valves 35, 36 having starting anodes 35b, 36b and cathodes 35a, 36a connected across the secondary windings of a transformer 37 connected in the signal-voltage circuit, and main anodes 35c, 36c which with the cathodes 35a, 36a are connected across the.capacitor 31. Thus should the signal voltage and the voltage supplied by the tachometer generator exceed a predetermined value sufficient to cause conduction between the cathode and main anode of one of the valves 35, 36 (depending upon the direction of operation of the system), the capacitor 31 is byepassed and the signal voltage modified to reduce the synchronizing torque.