Patent GB-1050530-A (GB)
Abstract: 1,050,530. Inertial navigation. AGA, A.B. Dec.31, 1963 [Jan.11, 1963], No.51318/63. Heading G1C. A gyro platform 31 for navigational purposes is mounted in gimbals 44, 47, for rotation about axis 5 and carries three or more symmetrically mounted identical single-axis gyros 1, 39, 40 mounted at equiangular intervals around the platform centre to swing in axial planes of the platform each gyro being acted on by a spring 8, Fig.1 (not shown) or otherwise subjected to a constant torque, seeking to rotate the gyro in the bearings 6, 7, of its single axis suspension thereby generating a constant precessional force acting in the axial direction of its suspension to impart rotation of constant angular speed w 1  to the platform 31, the gyros 1, 39, 40 in the absence of external angular accelerations maintaining the attitude of the platform 31 in space whilst themselves assuming and maintaining a position of angular equilibrium in their several single-axis suspensions. As shewn each gyro has a pick-off 9, 41, 42, supplying an amplifier and adding circuit 43 controlling a torquer 37 to-compensate frictional and other losses in the system so that the platform 31 rotates at constant speed. The output of pick-offs 9, 41, 42 are also connected to rotor windings 50 of a synchro on shaft 5 and the voltages induced in the perpendicular stator windings 52, 53, on gimbal 44 represent the magnitudes of the angular velocities W 2 , W 3 , about the axes 45, 48, respectively, generated by a torque seeking to charge the attitude of the platform. These voltages are applied via amplifiers 55, 56, to servos 57, 58, to maintain the axis 5 fixed in space regardless of the movements of the vehicle 49 carrying the system. Windings 52, 53, are also connected to stator windings 59, 60, of a sine-cosine resolver 61 whose rotor 62 can be rotated by servo 63. The voltages induced in rotor 62 are passed to a phase detector and amplifier 66 controlling servo 63 which thus rotates rotor 62 until the voltage in its winding is zero. If gimbal 44 is kept vertical and vehicle 49 is stationary relative to the surface of the earth, the platform 31 will respond to the effect of the earth's rotation W 1  acting at angle # to the axis 48 and since the voltages induced in windings 52, 53, and thus windings 59, 60 are proportional to W j  sin # and W 1  cos # respectively servo 63 rotates winding 62 until a pointer 64 on its shaft indicates angle # and thus the orientation of axis 48 relative to north. If axis 48 is parallel to the longitudinal axis of vehicle 49 then pointer 64 indicates the vehicle heading. To overcome the difficulties created by accelerations when the vehicle is moving, a system is used as in Fig. 8 (not shown). Two orthogonal pendulums 67, 68 provide outputs in windings 69, 70 which control servos 57, 58, to keep gimbal 44 vertical. Servo 63 controlling pointer 64 to give the heading, also positions resolvers 61, 73 and is itself controlled by the output of amplifier 79 fed from phase detector 72 supplied with a voltage of variable frequency from scanning member 71 sensing rotation of platform 31, and a reference frequency from the rotor winding 74 of sine-cosine resolver 73, whose perpendicular stator coils 75, 76, receive voltages in phase quadrature from a phase splitter 77 connected to a reference oscillator 78. The output of phase detector and amplifier 66 in this embodiment is smoothed in filter network 80 and controls a variable condenser to vary the frequency of the reference oscillator 78 so that when switch 81 is closed the position of north is established the compass card can be set and thereafter switch 81 opened and the pointer then indicates the heading of the vehicle. Bearing 87 is shewn as rotated in synchronism with shaft 5 to reduce friction at the bearings.