GB616248A - Improvements in and relating to servo systems - Google Patents

Abstract

616,248. Follow-up systems. SPERRY GYROSCOPE CO., Inc. Aug. 30, 1944, No. 16527. Convention date, Aug. 30, 1943. [Class 40 (i)] In a system in which an electric servomotor is controlled in accordance with the sense and magnitude of an error signal, the motor is a commutator motor in which the error signal controls the field excitation and variations of armature current resulting from the E.M.F. due to rotation of the armature are limited so that the torque remains proportional to the signal. As shown, Fig. 2, the error signal from coarse and fine selsyns which, owing to the presence of rectifier systems 37, 38 and 31, 32, are effective one at a time, is mixed with an anti-hunting signal derived from a tachometer generator 14 and differentiating circuit 54, 55 in a circuit involving a pair of twin triodes 42, 43 with an alternating plate supply to render the circuit phasesensitive. The resulting signal is amplified and applied to field windings 59, 60 of the servomotor. Variations of armature current are limited by a series resistor, capacitor or, as shown, inductor 62. In a modification, Fig. 3, the anti-hunting signal modulates, with the aid of a rectifier bridge 80 ... 82, a reference voltage 12 which is applied in series with the error voltage to a triode amplifier 66 feeding a push-pull amplifier 72, 73 similar to that in the system shown in Fig. 2. In another arrangement, Fig. 4 (not shown), the final amplifier is a single triode and the effect of the steady anode current is neutralized by an additional field winding carrying a direct current.