Patent GB-526980-A (GB)
Title: Improvements relating to automatic steering systems for craft
IPC: G05D1/02
Filed: 1939-03-30
Abstract: 526,980. Automatic control systems. SPERRY GYROSCOPE CO., Ltd., NISBET, R. H., and HARDING, W. G. (Sperry Gyroscope Co., Inc.). March 30, 1939, No. 9995. Addition to 506,379. [Class 38 (iv)] Direction.-In an automatic steering system for air or other craft there is provided, in addition to a steering control from a directional instrument for correcting for yaw or like deviation, a further control for correcting for drift, this additional control being dependent on values which express the drift displacement and the rate of changes thereof, these values being integrated with respect to time so that the drift control is composed of two parts, one proportional to the displacement and the other dependent on the time integral of said displacement. In one arrangement, the drift indication is obtained from two radio direction finder loops I, II co-operating with and tuned to a transmitting station on the required course of the craft. The loop I is set initially so that its axis lies along the required course and is maintained in this position by a reversible servo motor II controlled through contacts 12 by a directional gyroscope 16 a follow-up arrangement 8, 17, 18, 19 being provided. The outputs of loops I and II are fed through amplifiers 35, 23 to a transformer 28 which feeds the combined signal through an amplifier 29 to a servo-motor 30. When the craft has drifted, the motor 30 turns the loop II until the signal therefrom is equal and opposite to that from loop I the amount of rotation being thus proportional to the drift. The rotation of motor 30 effects rotation of shaft 48 through differential 39 which is also arranged to be driven by motor 11 so that no rotation of 48 is caused by turning or yawing of 'the craft. Shaft 48 is arranged, on energization of magnetic clutch 49 to drive shaft 53 carrying pinion 54 and thereby vary the setting of the ball-carriage 57 of the integrator 58 from its neutral position on the continuously-rotating disc 59. The roller 60 is thus turned slowly to drive the course-changing apparatus of the automatic pilot 101, the amout of rotation of the roller 60 so produced being proportional to the time-integral of the drift. The ball-carriage 57 is set additionally in accordance with rate of change of drift by rotation of shaft 69 which takes place whenever the speed of gear 66 driven from shaft 53 varies and becomes different from the speed of rotation of worm-wheel 67 which is driven by roller 68 of the differentiating device 65. In modification, Fig. 4, the course changing apparatus of the automatic pilot is driven by two reversible motors 112, 92 when rotation of shaft 48 takes place due to drift. The energization of motor 92 is controlled by a two-part rheostat 83, 84 the arm 82 of which is rotated by shaft 48 through clutch 49. The reversing fields of motor 112 are supplied through carbon piles 110, 111 rotation of shaft 48 controlling the motor 112 by controlling the relative resistances of these carbon piles through compression-apparatus 107, 108, 109. The shaft 48 is arranged to effect operation of this compression-apparatus through a slipping magnetic clutch 104 energized in accordance with the current supplied to motor 92. In another arrangement, Fig. 5, a single direction finder loop I' is stabilized in azimuth by means 120 and the signal therefrom which is approximately proportional to the drift is fed to terminals 128, 129 of a resistance bridge 123. The output from terminals 129, 131 is fed to an amplifier 132 supplying a motor 133 which operates the shaft 48 rotation of which is utilized as above described. In order to make the rotation of shaft 48 proportional to drift a voltage opposing the signal voltage is applied to terminals 131, 130 of bridge 123 under control of sliders 136, 137 on rheostats 138, 139 operated through screw-and-nut by motor 133. In the arrangements described with reference to Figs. 1 and 4, the loop I and its receiver 35 may be omitted, the arrangement being such that the angular rotation of shaft 48 then represents the angle between the required course of the craft and the line between its position at the time under consideration and the radio station. The loop II would be controlled by the motor 30 always to have its axis passing through this station. The drift angle may be read from dial 78 driven from the shaft 22 of loop II, Fig. 1, or from the shaft 99, Fig. 4, controlling the course changing arrangement of the automatic pilot 101. Specification 523,953 is referred to.