Patent GB-905440-A (GB)
Title: Improvements in or relating to position control arrangements and aerial systems including such arrangements
IPC: H01Q3/12
Filed: 1957-12-18
Abstract: 905,440. Automatic platform stabilization. GENERAL ELECTRIC CO. Ltd., FULLER, H. D., and SEWELL, A. D. Dec. 28, 1958 [Dec. 18, 1957], No. 39415/57. Class 38 (4). [Also in Group XL (c)] An arrangement for mounting an aerial system on an aircraft so that the direction of the transmitted beam is substantially independent of motions, in particular pitch and yaw, of the aircraft comprises, Fig. 2, a plane aerial reflector 4 mounted for rotation about two mutually perpendicular axes 4a, 4b, this reflector being mechanically coupled (as described with reference to Fig. 3) to a gyro-carrying platform 24, the coupling being such that for any given tilting of the reflector about the axes 4a, 4b the platform is tilted in the same manner but through twice the angular extent as the reflector. This 1 : 2 ratio is required because for any given tilting of the reflector the transmitted beam 22 is deflected through twice the amount and it is necessary for the normal 28 to the platform 24 to be maintained parallel to the beam. The platform is movable about an axis 24c in a frame 26 movable about an axis 24b, the axis 24b being carried by a frame 25 movable about an axis 24a. Tilting of the frame 21 about axis 4a through an angle # causes tilting of the frame 25 about axis 24a through an angle # and also tilting of the platform 24 relatively to the frame 26 about axis 24c through an angle #. Tilting of the reflector 4 about axis 4b through an angle # relatively to the frame 21 causes tilting of the frame 26 about axis 24b through an angle 2 # relatively to the frame 25. Two rate gyros (not shown in Fig. 2) on the platform 24 measure the angular velocities of the platform about two mutually perpendicular axes which are also parallel to the axes 24b, 24c, the axes also being perpendicular to the transmitted beam 22 since they lie in the plane of the platform. Electric signals from the gyros control servo valves in turn controlling hydraulic jacks which act on the mechanical coupling between the reflector 4 and platform 24 whereby the reflector is moved to compensate for any angular motion in space of the aircraft. Aerial construction.-A horn 1, Fig. 1, radiates waves 11 which are reflected by a fixed paraboloidal surface 3 comprising wires 5 embedded in dielectric material 6. The horn is situated at the focus of the surface 3 and the plane of polarization of the radiated waves is parallel to the wires 5, the distance between the wires being slightly less than half the wave length. The plane reflector 4, which receives the waves 12 reflected by surface 3, comprises a number of metal rectangular channel-shaped members 7 having side-walls 8, the distance between the walls of each channel being slightly less than half the wavelength. The walls 8 are at an angle of 45 degrees to the wires 5 and the depth of the walls in the direction of the axis 10 is an odd multiple of a quarter of the wavelength, these dimensions causing the plane of polarization of the waves 13 reflected by the reflector 4 to the perpendicular to the incident waves 12 whereby the reflected waves 13 pass between the wires 5 and are unaffected by the member 3. Construction of mechanical coupling between reflector 4 and gyro-carrying platform 58, Fig. 3. The reflector is mounted for rotation about axes 4a, 4b by trunnion members 32, 30, the frame member 31 corresponding to member 21 of Fig. 2, and being mounted by the trunnions 32 on a member 33 secured to a framework 34 fixed to the aircraft. A frame 43 mounted for rotation on the framework 34 about the axis 24a has a gear 42 secured thereto, which gear may be driven by gears 40, 41 connected, respectively, to hydraulic cylinders 35, 36. The cylinders tend to rotate the gear 42 in opposite directions and thus normally the gear is stationary; however, a pressure difference in the cylinders resulting from a signal from a gyroscope 61 mounted about an axis 24c produces a correcting movement of the frame 43 about axis 24a. A shaft 47 in a housing 48 attached to the frame 43 carries a boss 50 to which arms 51, 52 are fixed, the'arms being connected through universal joints 75, 76, rods 73, 74 and universal joints 77, 78 to the reflector 4, whereby movement of the frame about axis 24a produces a similar and equal movement of the reflector 4 about axis 4a. A rod 66 having a rack gear 66a is axially movable within the shaft 47 and boss 50 and transmits its motion directly to an axially movable and relatively rotatable rod 64 having a rack gear 64a meshing with a gear 63 secured to a shaft 60. The shaft 60 is carried by the platform 58 and has secured thereto the gyros 61, 62. A tube 65 journalled within the shaft 47 and slidably receiving the rod 66 carries a member 67 connected to a link 70 having a gear sector 68 meshing with the rack gear 66a. The link 70 is connected to links 71, 72 pivoted to the framework 34 at points 34b (only one point shown), the arrangement functioning as a parallelogram linkage so that on rotation of the frame 43 about axis 24a the gear sector 68 causes movement of the rack gear 66a, and the rack gear 64a rotates the shaft 60 about axis 24c by an amount equal to the displacement of the frame 43 about axis 24a. A gear 46 secured to the shaft 47, which is co-linear with the axis 24b, tends to be driven in opposite directions by gear sectors 44, 45 mounted on shafts 53 (only one shown). The gears 44, 45 are driven respectively, by hydraulic cylinders 37, 38 and the gear 46 is rotated when the pressure in the cylinders is different due to a signal received from the gyroscope 62 whereby the arms 51, 52 rotate the reflector 4 about the axis 4b. A pair of gear sectors 54 (only one shown) secured, respectively, to the shaft 53 mesh with a gear 55 secured to a shaft 56 rigid with the platform 58 and the gear ratios are such that the gear 55 rotates through twice the angular extent of the gear 46 whereby the platform 58 is rotated about the axis 24b by an amount equal to twice that of the reflector 4 about axis 4b.