GB784344A - Control systems - Google Patents

Abstract

784,344. Automatic steering control systems. SPERRY CORPORATION. April 29, 1955 [June 10, 1954], No. 12501/55. Class 38 (4). In a closed sequence automatic control system an electrical signal representative of the output of a servomotor is applied to means which respond to incorrect operation when the electrical signal contains a component having a frequency in excess of a predetermined value. As shown, the invention is applied to the elevator channel of an aircraft automatic pilot in which (a) an A.C. signal derived from a pitch pick-off 11 of a gyro vertical 10 is applied to an amplifier 12 controlling the excitation of a generator 29 supplying a servomotor 14 to operate the elevators; (b) a follow-up signal from an elevator pick-off 26 is fed back to the input of amplifier 12 which develops and adds a differential component of control; (c) a selector swicth 47 may be operated to apply to amplifier 12 an additional signal from either (i) an instrument landing radio receiver 39 to maintain a predetermined path; (ii) a pick-off associated with a bellows 40 to maintain a predetermined altitude; or (iii) a manually-operated device 45. For monitoring purposes the output voltage of generator 29 is applied through leads 48 to a relay winding 51 in series with a condenser 52 to eliminate components having a frequency below a predetermined value. Components having a frequency above this value which result from incorrect operation of the automatic pilot, are effective to operate relay 51 and disengage the automatic pilot by switching off a motor 31 driving generator 29. To prevent such disengagement due to a manoeuvre initiated by the radio receiver, altimeter or manual control, the signal from switch 47 is rectified at 57 and applied through leads 58 to relay 51 to oppose and cancel the voltage from generator 29. A network 59 is provided to simulate the performance of the servo system. Signals from switch 47 which have a rate of change exceeding a predetermined value develop in a differentiating circuit 66 a voltage sufficient to operate a relay 70 which opens the circuit of relay 51 and thereby prevents the monitoring circuit from disengaging the automatic pilot under these conditions. Specifications 629,104 and 663,913, [Group XXXVIII], are referred to.