Patent GB-609804-A (GB)
Title: Improvements in and relating to control systems for power-driven movable objects
IPC: F15B9/14
Filed: 1942-04-07
Abstract: 609,804. Fluid-pressure servo motor-control systems. POLSON, R. A., DANNATT, C., METROPOLITAN-VICKERS ELECTRICAL CO., Ltd., and VICKERS-ARMSTRONGS, Ltd. April 7, 1942, No. 4576. [Class 135] [Also in Group XXXVIII] In a system for positioning a power-driven object in correspondence with a controlling member, remote therefrom or otherwise, the displacement of an output element by means, e.g. an electrical selsyn system, responsive to the displacement of the object relative to the member imparts to the control means of the prime mover, e.g. a fluid-pressure motor, a movement which has components corresponding to the displacement of said output element and one or more of its time derivatives. The torque or speed of the drive thus comprises a displacement component, and one or more components dependent on the velocity and/or acceleration of the object relative to the member acting in a direction to reduce the relative velocity to prevent hunting. In the system shown in Fig. 1, the rotor 14 of a differential selsyn 15 is controlled by selsyns 10, 11 coupled to the controlling member and movable object respectively, but in a modification, Fig. 2 (not shown), the output of an ordinary selsyn receiver is connected by a rectifying arrangement (Specification 609,297, [Group XXXVIII]) to a moving coil relay which controls link 20 controlled in Fig. 1 by the differential selsyn. Fluid-pressure control and driving arrangements. The movement of link 20 is amplified by a fluid-pressure relay 22 and applied to a linkage 23 which introduces velocity and/or acceleration components into the displacement of valve gear controlling the fluid-pressure motor 1. The relay 22 comprises a doubleacting piston and cylinder 25 and control valve 30 connected to floating lever 21 operated by link 20, the movement of rod 32 being determined by restoration of valve 30 to normal. The rod 32 is connected to lever 48 which moves the upper end of floating lever 46 in accordance with the displacement of rod 32 and causes the lower end of the lever 46 to move in accordance with the velocity component due to the interposition of dashpot 51, the piston of which is biassed by spring 53. In the modification shown in Fig. 3, an acceleration component is introduced by the interposition of a rotary member 70 having considerable inertia. If the member 70 is also subjected to damping, e.g. by a magnetic or electromagnetic brake, an additional component dependent on velocity is introduced, or this component may be introduced alone by the brake if member 70 is of low inertia. The movement applied to link 44 has therefore components dependent on relative displacement and velocity and/or acceleration of the movable object and controlling member. This movement is applied to floating lever 41 controlling valve 39 of the fluid - pressure cylinder 34, the rod of which is connected to valve 4 of the motor 1 and to the upper end of the floating lever by stabilizing dashpot 43, whereby the velocity of movement of valve 4 is dependent on the movement of link 44 and the torque of the motor has the components set forth above. Other known forms of variable velocity ratio transmission gear may be used. The Provisional Specification also refers to Specification 592,208.