GB934058A - Improvements in or relating to electrical apparatus for supplying electric signals which provide a measure of the angular position of a vector - Google Patents

Abstract

934,058. Electric analog calculating. GENERAL ELECTRIC CO. Ltd. Sept. 27, 1961 [June 29, 1960], No. 22846/60. Class 37. [Also in Groups XXXVIII and XL (c)] The invention relates to electric analogue apparatus for computing from signals dependent on the orientation of a vector relative to a first set of axes its orientation relative to a second set, where the angular position of the first set relative to the second varies with, and at twice the rate of, variation of the angular position of the vector about two mutually inclined axes of rotation, and is described as applied either to providing a radar indication of the direction of a beam reflected from an aerial member or to controlling the direction of such a beam either manually or during scanning. The aerial member is a plane reflector 5, Figs. 1 and 2 (of an aerial system of a type disclosed in Specification 884,313) on which a collimated beam is incident in a direction parallel to the longitudinal axis 10 of the aerial system to provide a reflected beam whose direction may be varied by rotation of the reflector about an axis 9 which itself is rotatable about a further axis 8. The rotation is by hydraulic means actuated by a mechanical control unit 14 in response to electrical signals supplied to it via leads 18 and 19. The unit 14, which may be of a type disclosed in Specification 905,440, provides two further mechanical outputs in the form of a shaft 21 which rotates from a datum position through an angle equal to the angular displacement (# say) of the reflector 5 (and the axis 9) about the axis 8, and a second shaft 22 which rotates from a datum position through an angle equal to twice that of the angular displacement (# say) of the reflector about the axis 9. These shafts are coupled to the rotors of three synchro resolvers connected in a chain 20 as described below. The beam incident upon the reflector 5 originates from a horn 3 at the focus of a paraboloidal reflector 4 and the horn may nutate about the axis 10 to cause the beam reflected from the reflector 5 to execute a corresponding conical scanning movement. When the beam is reflected along its incident path parallel to the axis 10, Fig. 4, this and the axes 8 and 9 are mutually perpendicular and they then define the directions of a fixed set of reference axes X 3 Y 3 Z 3 . When the reflector is rotated through the angle # about the axis 9 and through an angle 0 about the axis 8, the reflected beam direction, or the axis of beam nutation, rotates through twice these angles to assume a direction 45 which defines another set of reference axes X 0 Y 0 Z 0 . To provide signals which are a measure of the orientation of the beam relative to the fixed set of reference axes X 3 Y 3 Z 3 (which signals may be used for an indication of the beam orientation on a radar display) A.C. signals representative of the direction cosines of the beam directions relative to the axes X 0 Y 0 Z 0 are supplied from a source 29 to the first of a chain 20 of three synchro resolvers. The rotor of this first resolver 30, Fig. 3, and that of the third 32 are connected to the shaft 21 so that each is rotated through an angle - #, whilst that of the second 31 is rotated through an angle - 2# by the shaft 22. As indicated in Fig. 3, the chain successively computes from the supplied direction cosine signals l 0 , m 0 , n 0 , those corresponding to the sets of axes shown in Fig. 4, so that the output signals over leads 26, 27, 28 are representative of the direction cosines of the beam relative to the fixed axes X 3 Y 3 Z 3 . Tocontrol the beam direction, it is initially defined with reference to the fixed axes X 3 Y 3 Z 3 by supplying the resolver chain with signals representative of the direction cosines of the desired direction with reference to these axes X 3 Y 3 Z 3 . These signals may be set either manually, Fig. 5 (not shown), to direct the beam, or cyclically by automatic means to provide a scanning motion. In this case the shafts 21 and 22 are rotated respectively through angles +# and + 2# so that the chain output signals represent the direction cosines l 0 , m 0 , n 0 of the desired direction of the beam relative to to the axes X 0 Y 0 Z 0 . Since, however, the beam should be parallel to the X 0 axis (by definition of this axis) the signals should have the respective values of 1, 0, 0, and any departure of the values of m 0 and no from zero therefore represent the departure of the beam from the desired direction. These two output signals form error signals applied to the leads 18 and 19 to retroactively energize the mechanical control unit 14. Alternatively, the direction cosines relative to the axes X 0 Y 0 Z 0 may be derived by rotating the shafts 21 and 22 through angles - # and - 2# and passing signals in the opposite direction through the resolver chain 20, i.e., by using the leads 26, 27 and 28 as input leads and the leads 23, 24 and 25 as output leads. Specification 934,057 also is referred to. Reference has been directed by the Comptroller to Specification 884,313.