GB926471A - Improvements in or relating to servo systems - Google Patents

Abstract

926,471. Automatic control. S. SMITH & SONS (ENGLAND) Ltd. Dec. 1, 1961 [Dec. 21, 1960], No. 43845/60. Addition to 856,826. Drawings to Specification. Class 38 (4). As in the parent Specification signals dependent on a common control quantity are applied to a plurality of amplifiers each of which energizes a servomotor operating a common load and the transmission characteristics of each of a number of the amplifiers is controlled in dependence on a comparison between the output of that amplifier and a common reference quantity. In the present Specification each amplifier, which may be thermionic valve, transistor or magnetic, comprises a variable gain pre-amplifier and a main amplifier in cascade, the output of one of the main amplifiers serves as the reference, and signals resulting from the comparisons vary the gains of the pre-amplifiers and are also fed back to the inputs of the preamplifiers. An elevator channel of an aircraft automatic pilot having three sub-channels of the rate/rate type, one serving as the master, is described in which the sense of the variation of pre-amplifier gain is made dependent on the sense of pre-amplifier input and the feed-back to each pre-amplifier input is applied through two parallel paths, one including an electromechanical integrator for long-term errors and the other including an attenuator and limiter for short-term errors. Control signals from rate gyros, pendulums and radio altimeters, addition of differential and integral components to the control signals, torque-limiting clutches between the servomotors and the load, and automatic substitution of another sub-channel as master if the master channel fails are referred to. Specification 901,458 also is referred to.