Patent GB-931337-A (GB)
Title: Navigation apparatus
Inventor: BRITNELL CLIVE
IPC: G01S1/02
Filed: 1958-10-31
Abstract: 931,337. Electric analogue calculating. SPERRY GYROSCOPE CO. Ltd. Oct. 23, 1959 [Oct. 31, 1958; Sept. 3, 1959], Nos. 35087/58 and 30055/59. Class 37. [Also in Group XL (a)] In a navigation apparatus for determining the deviation of a craft from a ground track between a starting point A, Fig. 1, and a destination point B such that the ratio of the co-ordinates of any point on the track relative to the point B is a constant K, voltages V1 and V2 = KV1 are applied respectively across similar potentiometers 22, Fig. 2, and the sliders 21 of the potentiometers 22 are displaced respectively in accordance with the actual coordinates of the craft relative to the point B so that the amplitude of the error voltage between the sliders represents the magnitude of the displacement of the craft from the track, the error voltage being applied to an indicator or to an automatic pilot controlling the craft. As described the co-ordinates are hyperbolic coordinates # and #, Fig. 1, defined by a CW or pulse hyperbolic radio navigation system and in suitable circumstances the error voltage is proportional to the lateral displacement z of the craft from the track 12. In such a hyperbolic system the track 12 will generally be curved and the curvature may be reduced by progressively varying the value of K as the craft proceeds towards the destination. As shown in Fig. 2 the voltages V1 and V2 for the potentiometers 22 are supplied by the stators 23 of an inductive resolver 24 and the sliders 21 of the potentiometers 22 are controlled by the output shafts of respective differential gears 29. In the setting-up mode the # or # co-ordinates # A , #B and #A, #B of the points A and B on the track are set in manually to the inputs of the left-hand and right-hand differentials respectively so that the ratio of the displacements of the left-hand and right-hand sliders is and the error voltage between the sliders 21 is applied through the closed switch 28<SP>1</SP> to a servomotor 31 which automatically positions the resolver 24 to reduce the error voltage to zero thereby establishing the condition  V2/V1 = K. In the tracking mode the ganged switches 28 and 28<SP>1</SP> are operated to disconnect the servomotor 31 and to apply the actual craft coordinates #x, #x from the radio receiver 15 to the differential 29 in place of the starting-point co-ordinates # A , #A; the error voltage now represents the deviation of the craft from the track. If the starting point A is taken as the actual position of the craft at a particular instant then the co-ordinates corresponding to said position as determined by the receiver 15 may be stored during the setting-up mode and applied to the differentials 29 in place of the manual inputs # A , #A on channels 32, 33. The second Provisional Specification also describes (1) means for varying the voltages V1 and V2 to define a more linear track, Figs. 1 and 2 (not shown); (2) means for indicating the distance to the destination, Fig. 3 (not shown); (3) means for programming the apparatus to define a particular track, Figs. 4 and 5 (not shown); and (4) means for guiding an aircraft along a predetermined track at a predetermined height and at a predetermined speed, Fig. 6 (not shown); this subject matter is not included in the Complete Specification.