Patent GB-690095-A (GB)
Title: Improvements in or relating to automatic steering systems
IPC: G05D1/02
Filed: 1949-04-04
Abstract: 690,095. Automatic control systems for aircraft. SPERRY CORPORATION. April 4, 1949 [April 8, 1948], No. 9101/49. Class 38 (iv). In an automatic system for steering a craft along a prescribed course toward a radio transmitting station, wherein a radio receiver 15 in conjunction with a gyro 37 provides two control signals for the rudder 89 varying respectively according to the deviation (α) from the prescribed course (#) (transmitter 45) and the deviation of the heading of the craft from the direction of the course (transmitter 69), means, e.g. a motor 91, is provided responsive to the deviation from the course for gradually changing the heading of the craft. This arrangement automatically introduces additional crab-wise heading into the craft so that the craft deviates only temporarily from the pre-set course in the event of cross-wind currents. As shown in Fig. 1, the loop aerial 11 of the radio receiver is automatically aimed at the transmitter by a motor 21 either over a local circuit when switch 25 in in its upper position, or when switch 25 is in its other position over a stabilizing circuit controlled by the gyro 37 and including Selsyns 33, 35, differential Selsyn 31 and amplifier 39. This stabilizing system provides a gradual azimuth correction through the Selsyn 31 for the loop 11 in response to integrated signals from the loop. When it is desired to guide the craft along a selected line to the radio station, the craft is flown to a position on this line, the compass bearing of which is indicated by the pointer 99 of the repeater 44 of the loop transmitter 41, and the course setting handle 61 is operated to set the transmitter 45 in accordance with the selected course (#). The handle 79 is then set (crab angle) in accordance with the cross-wind condition and the automatic pilot switched in at 86 to control the rudder servomotor channel 85, 87, 89. The handles 61 and 79 control the setting of the ester of a Selsyn 69, the output over the leads 83 being representative of the selected course and the crab angle ( #). The output of the Selsyn 45 as applied to a limiter amplifier 63 is representative of the changes (p) of bearing of the radio station upon departure of the craft from the present course and the arrangement is such that while on this course the rudder 89 is operated to suppress output from 69 and thereby balance the two signal outputs to the amplifier 65. Upon a departure from course, a signal (α) applied to 63 changes the rudder's position and heading to ensure arrival of the craft at the radio station but this operation alone does not facilitate rapid return of the craft to the selected course. This rapid return, however, is effected by a motor 91 which in response to signals from 45 (α) operates the setting mechanism 79 at a slow rate to introduce additional " crab " angle. In this manner the " crab " angle is adjusted automatically to that required for guidance of the craft along the originally selected flight line, rather than along an entirely different course due to cross-wind. In a modification (Fig. 3, not shown) an omnidirectional radio system is used and compass bearings are given directly by the radio receiver, the corresponding signals being applied to a Selsyn 45 which is independent of the gyro 37. The Selsyn 45, however, is set in accordance with the course as in Fig. 1, but the gyro controls a single Selsyn, the output of which is representative of both course and " crab " angle. The additional " crab " angle adjustment is provided by a motor-controlled potentiometer instead of the geared motor 91, Fig. 1, the potentiometer and output from Selsyn 45 acting in opposition to the gyro Selsyn in the rudder channel. The potentiometer is controlled by the signals from Selsyns 45, the circuit including a resistance capacity combination to provide a rate-of-change component. Specifications 523,953, 626,124 and 660,552 are referred to.