Feedback control servosystems

Abstract

Abstract 814,093. Automatic control systems. FAIREY AVIATION CO. Ltd. Feb. 12, 1957 [Feb. 14, 1956], No. 4662/56. Class 38 (4). In a servo control system having a feedback loop, means responsive to increased gain round the loop at a frequency outside the range of working frequencies reduces the gain of an element in the feedback loop. In Fig. 3 an aircraft radio receiver (not shown) produces an electrical signal, representative of displacement of the aircraft from a radio beam or a turn control signal from a remote radio operator, which is applied at 10 through a low-pass filter 11 and an adding unit 13 to an amplifier 17 energizing an electrically operated valve 19 controlling a fluid-actuated rudder 22 of the aircraft 24. The consequent lateral acceleration of the aircraft is made proportional to the control signal by an electrical signal derived from an accelerometer 30 which is applied through an amplifier 34 to an adding unit 13. A signal is also applied to adding unit 13 from an oscillator 81 having a frequency close to the self-oscillation frequency of the feedback loop. After passing through amplifier 34 this signal is separated from the feedback signal by a band-pass filter 83, rectified, and compared with the rectified output of oscillator 81 in a circuit 94. Circuit 94 is arranged so that if the gain of the feedback loop exceeds, say, 0.7 the consequent output from circuit 94, after smoothing at 95, reduces the gain of feedback amplifier 34. An alternative arrangement in which the gain of the forward part of the feedback loop is controlled, is referred to. A control signal limiter may be associated with the input to adding unit 13. In a modification oscillator 81 is dispensed with and self-oscillation is arranged to limit itself by controlling the gain of the feedback amplifier. Amplifier 34 may alternatively be controlled by a signal which is an integral function of oscillation amplitude. Suitable forms of filter and feedback valve amplifier are described and component values given.

Inventors

• 👤 Surtees Howard

Bibliographic Details