GB609808A - Improvements in and relating to control systems for power-driven movable objects - Google Patents

Abstract

609,808. Fluid-pressure servomotor-control systems. RYDER, C., and METROPOLITANVICKERS ELECTRICAL CO., Ltd. Sept. 11, 1944, No. 17348. [Class 135] A control system for maintaining a poweroperated object in correspondence with a control member without hunting and including means responsive to the relative displacements of the object and the member for regulating the supply of pressure liquid to a hydraulic engine operating the object is provided with a liquid stabilizing system for imposing on the output element of the displacement responsive means a movement opposite to that effected by the displacement and corresponding to the second and third derivatives and also, if desired, the first derivative of said displacement. The control system may comprise means 19, e.g. of the selsyn-operated type described in Specifications 592,208 and 609,804, responsive to the misalignment between the control member and the object and having an output element 20 attached to a floating lever 21 connected by a link 22 to the liquid control valve 17 of a servomotor, the piston 13 of which operates a valve 8 regulating the flow of pressure liquid from a duct 9 connected to a constant pressure, variable delivery pump to a rotary engine 1 which operates the object, the lower end of the lever 21 being centralised by a spring 23 and connected by a link 24 to the piston 36 of a liquid stabilizing system. The stabilizing system includes a cylinder 35 having a vent to a vessel 39, a piston 37 connected to the servomotor piston and a duct 34 communicating with a cylinder 31 having a piston 30 carried by the rod 29 of a piston 28 subject to the pressure difference across the engine. Movement of the element 20 results in the opening of the valve 17 and operation of the servomotor which opens the valve 8, thus permitting the flow of pressure liquid to the engine 1. The pressure difference across the engine effects the displacement of the piston 30, which is a measure of the acceleration of the movable object, and thus of the piston 36 by which a restoring movement is applied to the floating lever 21. The displacement of the piston 36 is modified by that of the piston 37 which is dependent on the rate of supply of liquid to and, therefore, of the velocity of, the piston 30 which depends on the rate of acceleration of the object. The means 19 will usually include a response dependent on the velocity of the object. In a modification, in which the piston 37 is omitted, the servomotor actuates an arm which varies the inclination of the swash-plate of a variable delivery pump supplying liquid to the engine 1.