Patent GB-755326-A (GB)
Abstract: 755,326. Gyroscopic apparatus. NAAMLOOZE VENNOOTSCHAP HOLLANDSE SIGNAALAPPARATEN. Nov. 5, 1953 [Nov. 7, 1952], No. 30635/53. Class 97 (3). Erecting means for a gyro-vertical includes a device which integrates with respect to time a physical quantity comprising two terms, one term being substantially proportional to the horizontal acceleration of the apparatus perpendicular to an adjusting axis of the gyroscope, and the other term being determined in sign, and in magnitude if required, by the deviation of the gyroscope from the true vertical, the output of the integrating device being used to control in direction, and in magnitude if required, the correcting torque applied by a motor. A third term may be added to the quantity to be integrated, this term having such a sign that, the other two terms being zero and other influences being absent, it brings the integrating device into such a condition that the torque motor is switched off. The value of this third term preferably changes little or not at all with the value of the integration result and the positions of the gyroscope and a gravity responsive device. As shown, in Fig. 2, a closed electrically-insulating tube 201 mounted on the gyroscope housing contains a long electrode 204 and two other electrodes 205, 206. A drop of mercury 203 rests on electrode 204 and has a position in which it touches neither of the electrodes 205, 206. On either side of this position the drop connects electrode 204 to one of the other electrodes, completing a circuit to drive a torque motor one way or the other. Preferably, the tube is filled with an insulating damping liquid. The dimensions of the tube and drop 203 are such that when the gyroscope is unfilled and the tube is accelerated lengthwise, the drop moves with a velocity proportional to the acceleration. The displacement of the drop thus represents the time integral of the acceleration, i.e. the first term. The increase in velocity of displacement of the drop when the gyroscope is tilted represents the second term. During an oscillatory motion, e.g. the rolling of a ship, the integral of the acceleration for a complete period is zero, even if the motion is unsymmetrical, and the drop returns to its neutral position after the torque motor has been energized equally in opposite directions; unless the gyroscope has left true vertical, in which case the torque motor is energized to a greater extent in a direction setting up an erecting precession. The tube may be straight and, in its neutral position, horizontal; but the consequent unstable equilibrium of the drop may lead to hunting, so it is preferred to make the arms of the tube at a small angle #. The resulting tendency of the drop to seek a central position represents the third term. Several modifications are described. The drop may be insulating and the damping liquid conductive; it may in its neutral position touch both electrodes 205, 206 instead of neither; it may be lighter than the damping liquid, in which case it may consist of a gas bubble and the tube is bent upwards; and there may be a number of electrodes distributed along the tube. In a gyro-vertical two tubes are mounted on the casing at rightangles, but in some applications only one tube may be required. When the craft carrying the gyroscope turns, the centrifugal acceleration would be integrated, giving a spurious correction. This may be avoided by mounting the tube by means of a pendulum normally rigid with the gyro housing. Turning movement of the craft is detected as by a gyroscope which frees the pendulum. In another embodiment, Fig. 4, a gyro-vertical 401 is suspended in a gimbal-ring 402 to rotate about axes 403, 408. In order to keep the gyro axis vertical, its position is compared with the position of a pendulum 409 pivoted about an axis parallel to axis 408, and with a similar pendulum (not shown), pivoted about an axis parallel to axis 403. Signals from an electrical transmitter 410 connected to the pendulum are fed to a differential transmitter 407 connected to axis 408. The output from transmitter 407, which is proportional to the difference between the positions of the pendulum and of the gyro axis with respect to axis 408, is applied to a receiver 411, connected with a servo amplifier and phase-discriminator 412 and a follow-up motor 413 so that shaft 414 rotates by an amount equal to the difference between the movements of pendulum 409 and shaft 408. This difference has a component due to horizontal acceleration corresponding to the first term, and a component due to the deviation of the gyro axis from the true vertical corresponding to the second term. Shaft 414 is connected by a spring 416 to a shaft 417 geared to a damping device 418, which converts the movement into a torque and also has an integrating effect with.respect to time. Shaft 417 operates a switch 419 energizing a torque motor 404 acting on the gyroscope about axis 403 and so producing a precession about axis 408 to restore the gyro axis to the true vertical. A torque motor 406, similarly controlled, effects precession about axis 403. When the craft containing the apparatus turns, a gyroscope (not shown) mounted as a rate-of-turn indicator operates contacts to energize an electromagnet 420. This rocks an armature 421 about an axis, breaking contacts 425 in the operating circuit of the torque motor 404 and engaging a gear wheel 424 by a tooth 423 to hold shaft 417 still until the turn is complete. In a further embodiment, Fig. 7, coils 707, 708 are rotatable about a common axis, the rotations being controlled by a pendulum and by the gyroscope housing respectively. When the pendulum and the gyro axis are parallel, the coils are at right angles, and consequently the current in coil 707, which is fed by an A.C. source, induces no voltage in coil 708. Relative displacement of the pendulum and gyro axis, and hence of the coils, results in a voltage induced in coil 708 which is applied to a phase discriminator and amplifier 710, the D.C. output of which corresponds in amplitude and direction to the displacement of the gyro axis with respect to the pendulum and is applied across resistors 711, 712. The voltage across the resistors is integrated by a circuit comprising resistor 713, and a condenser 716. Condenser 716 may be bridged by a resistance 718 to provide the third term for integration. Resistors 713, 718 may each be replaced by a pentode, or two pentodes connected oppositely in parallel. The output of the integrating circuit is used to energize a torque motor 720.