Patent GB-611046-A (GB)
Title: Improvements in and relating to control systems of the correspondence kind for movable members
IPC: G05D3/12
Filed: 1945-06-07
Abstract: 611,046. Electric control systems. BELSEY, F. H., BROADBENT, D. T., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. June 7, 1945, No. 14451. [Class 40 (i)] [Also in Group XXXV] In a system for automatically maintaining positional correspondence between a motordriven movable member and a control member by controlling the motor in accordance with deviation of the movable member from correspondence, a component of control for the motor is dependent on relative velocity between the motor and the movable member resulting from resilience or backlash in the drive. The Figure shows a modification of the system, described in Specification 610,029, for automatically maintaining without instability due to drive resilience or backlash, a movable body 2, driven by a D.C. motor 3, in positional correspondence with the setting of a handwheel 1. As in the above-mentioned Specification a transmitter selsyn 13<SP>1</SP>, the rotor of which is supplied from an A.C. source and driven by hand-wheel 1, is interconnected with reset selsyns 16<SP>1</SP> and 26<SP>1</SP>, the rotors of which are driven by motor 3 and movable body 2, respectively, and supply to a thermionic valve amplifier 8, through conductors 9 and 10, an A.C. input signal which thus contains components dependent on misalignment between motor 3 and hand-wheel 1 and between movable body 2 and hand-wheel 1. The relative magnitude of these components is preset by potentiometers 35 and 36<SP>1</SP> for optimum stable operation. Amplifier 8 controls the field excitation of a metadyne generator 6 supplying motor 3 which operates to correct misalignment. The modification is the introduction of D.C. tachometer generators 15, 16, 17 coupled to a hand-wheel 1, motor 3, and movable body 2, respectively, to introduce, through conductors 11, 12, velocity components into the input of amplifier 8. Fractions of the voltages of generators 16 and 17, predetermined by the setting of potentiometers 18 and 19 are additive and oppose the voltage of generator 15 when the velocities of hand-wheel, motor and movable body are in the same sense, and when the three velocities are equal, the arrangement is such that the resultant D.C. voltage applied to amplifier 8 is zero. Potentiometers 18 and 19, which may be ganged like potentiometers 35<SP>1</SP> and 361 are set for optimum stable operation. The first stage of amplifier 8 is constituted by a pair of triode valves 30, 31, provided with cathode bias 36<SP>1</SP> to the grid circuits of which the A.C. misalignment signal is applied through a transformer having a primary 33 and secondaries 32, 32a, while the D.C. velocity components are introduced through a centre-tapped potentiometer 35. The valve anodes are supplied on phase opposition from the A.C. source through transformers 37 and 38 and the remaining amplifier stages are responsive to the difference of the two anode currents. In a modification, Fig. 2 (not shown), the position of a platform is stabilised about a single axis by a gyro and selsyn system as in Specification 610,029 with the addition of three D.C. tachometer generators introducing velocity components. The voltage of one of these generators, driven by the motor adjusting the platform position opposes that of a second, driven by the platform, and a fraction of the resultant voltage, pre-selected by a potentiometer, is combined with the voltage of the third generator, which is differentially driven from the gyro output shaft and the platform or motor, to constitute the velocity component of the amplifier input. The Specification refers to systems in which the velocity component is the only component of control. An electro-magnetically-controlled hydraulic motor may replace the electric motor in the arrangement described. Specification 592,208 also is referred to.