Patent GB-611020-A (GB)
Title: Improvements in or relating to automatic electric-motor control systems
IPC: B64D45/00
Filed: 1943-10-18
Abstract: 611,020. Automatic control systems. SMITH & SONS (ENGLAND), Ltd., S., (formerly SMITH & SONS (MOTOR ACCESSORIES), Ltd., S.), and MEREDITH, F. W. Oct. 18, 1943, No. 17137. [Classes 35 and 38 (iv)] Attitude.-A hysteresis motor, on account of the linear relation existing between the input voltage and output torque thereof, is utilized to stabilize the variable in an automatic control system of the kind wherein deviation of a variable from its datum position or value is corrected by reversible electric motor energized by an alternating voltage of amplitude and phase dependent upon the magnitude and direction of the deviation. The variable stabilized may be the relative position of a body, its temperature, its linear or angular speed, or the pressure in a fluid in relation to a datum pressure. As shown n Fig. 1, a turntable 12 pivoted to a fixed part 11 of an aircraft is stabilized in azimuth by a generator 13 mounted on the turntable and electrically connected to one phase of a twophase hysteresis motor 15 carried by the part 11 and connected to the turntable by a reduction gearing 16. Generator 13 provides an alternating control voltage proportional to the rate of turn of the turntable and in quadrature with a constant amplitude voltage of the same frequency which energizes the second phase of the motor, the direction of rotation of the turntable determining whether the control voltage leads or lags the constant amplitude voltage and, consequently, the direction of rotation of motor 15 which is so connected that it rotates the turntable in the opposite direction. The generator may be of the form described in Specification 611,005, [Group XXXVIII]. Fig. 2 shows a similar system in which the turntable is stabilized by a generator 133 producing an alternating voltage of magnitude proportional to the angle of turn of the turntable and of phase sign dependent on the direction of turn, as well as a constant amplitude voltage of the same frequency, which latter voltage excites, via circuits 22, 25, one phase of each of a hysteresis motor 15 and a hysteresis dynamo 21 driven thereby. The variable voltage is fed, via circuit 18, in opposition to the dynamo voltage to a resistance network 19, the voltage difference being fed through circuit 24 to the other phase of the motor, which thus rotates the turntable backwards at a speed proportional to the angle of deviation. A monitor compass 17 of the kind described in Specification 578,303, [Group XXXVI], may correct for any remaining deviation. A hysteresis motor for use in the system of Fig. 1 may comprise a rotor 12, Figs. 3 and 4, in the form of a sleeve of ferromagnetic material of high coercivity and a high permeability stator built up of annular stampings 16 surrounding toothed stampings 14 which receive the polyphase windings and are apertured to accommodate the rotor. The hysteresis motor generator utilized in the system of Fig. 2 may consist of two spaced axially aligned stators having a common tubular rotor. Specifications 576,248, 611,016 and 611,019 also are referred to.