Patent GB-683883-A (GB)
Title: Radio navigation system
IPC: G05D1/02
Filed: 1948-09-10
Abstract: 683,883. Radio navigation. BENDIX AVIATION CORPORATION. Sept. 10, 1948 [Oct. 23, 1947], No. 23870/48. Class 40 (vii). [Also in Group XXXV] A system for automatically maintaining a craft on a predetermined radial course towards a radio transmitter B comprises a radio compass and a magnetic compass producing signals respectively proportional to the relative bearing # of the transmitter from the craft and the magnetic heading # of the craft, and means for setting in the magnetic bearing # of the course to produce an error signal α proportional to the difference between the magnetic bearing # of the course line and the magnetic bearing (# + #) of the transmitter from the craft, the error signal being applied to an automatic pilot. As shown in Fig. 1, the radio compass comprises loop and open aerials 12 and 11, the output from the receiver 13 being applied to a D.C. motor 17 which automatically orientates the loop perpendicular to the direction of propagation of the received radio waves so that the angular position of shaft 14 is equal to the relative bearing # and this angle is transmitted by a Selsyn 21, 22 to a differential Selsyn 39, 41 whose rotor 41 is manually set by a knob 43 at an angle # equal to the magnetic bearing of the desired course. The rotor 41 is electrically coupled to the stator 54 of a Selsyn control transformer 55 so that the angular position of the resultant field in stator 54 is equal to (# - #). The magnetic compass comprises a gyro-stabilized earth inductor compass 23 of the type described in Specification 662,831, [Group XXXV], which produces in the 3-phase stator 24 a resultant field of angular position # and the shaft 28 is rotated through a corresponding angle by a servo comprising rotor 27, amplifier 30 and 2-phase motor 32, the resultant rotation being transmitted to rotor 53 of the Selsyn control transformer 55 by a Selsyn transmitter 35, Selsyn control transformer 46 and a 2-phase servomotor 52 so that an A.C. error signal is produced in rotor 53 representing in phase and magnitude the sense and magnitude of the angle α. The error signal may be applied directly to an automatic pilot to bring the craft to the selected course but this would produce overshoots which are avoided by rectifying the error signal at 60 and applying it to a computer unit 58 of the type described in Specification 675,751 which produces a control signal proportional to the time that the craft is away from the desired course and this control signal is mixed with a signal proportional to the magnetic heading # developed by a signal transmitter 63 and applied to a servo-amplifier 62 of an automatic pilot of the type described in Specification 662,831, [Group XXXV], to be mixed with a rate-of-turn signal developed by a signal pick-off 64 and a follow-up signal developed by an inductor device 65, the output of amplifier 62 energizing a driving motor 66 for operating the rudder. If, when the craft has been brought to the correct course, its heading is not parallel to the course, instability may result which may be prevented by an automatic orientator unit 67 as described in Specification 675,758, which engages the magnetic compass into the computer by means of a clutch 70 when the difference between the heading of the craft and the bearing of the course is less than some predetermined angle.