Patent GB-1064219-A (GB)
Title: Gyroscopically stabilised platforms
Inventor: CAHOON DICK BINGHAM
IPC: G01C21/18
Filed: 1965-08-27
Abstract: 1,064,219. Gyroscopic apparatus. NORTH AMERICAN AVIATION Inc. Aug. 27, 1965, No. 36987/65. Heading G1C. Single degree-of-freedom gyroscopes which are used to stabilize the attitude of an inertial guidance platform are monitored by the provision on the platform of an additional single degree-offreedom gyroscope comprising a gimbal mounting to enable the input axis of the additional gyroscope to be aligned with the input axis of the gyroscope under test in the two possible 180 degrees displaced positions, the additional gyroscope being controlled by a servo-loop comprising a computer in the period when the gimbal is being rotated between the two 180 degrees displaced positions the control signals from the computer allowing for drift of the additional gyroscope, and also providing a correcting signal to the gyroscope under test if the two positions of alignment between the input axes of the additional gyroscope and gyroscope under test are not exactly 180 degrees apart. In the described embodiment the platform is stabilized by three single-axis gyros arranged with their spin axes orthogonal. Two of these axes are preferably cardinal axes. The additional gyroscope, shown in Fig. 3, can be used to monitor two of the stabilizing gyroscopes, and a further additional gyroscope may be provided too so that all three stabilizing gyroscopes may be monitored. The gyro rotor is electrically spun and is mounted in a float 23 rotatable in bearings 15, 25 in a case 18 the case containing a viscous flotation fluid. The case 18 is mounted in a gimbal 17 rotatable about an axis Z parallel with the Z-co-ordinate axis of the reference co-ordinate system defined by the platform stabilizing gyros. The output axis 10 of the additional gyro is arranged at an angle and to the axis Z and not at right angles thereto, to limit the applied torques and thus prevent damage to the gyroscope. The float member 23 is coupled to the case 18 by the viscous fluid and movement of the float member 23 is monitored by an E-core pickoff 34, whose output is fed through an amplifier 47 direct to a torquer 27 when switch 44 is in position 2 or, with switch 44 in position 1 via a computer 45 which additionally corrects the float member for known gyro-drift. In operation the input axis 22 of the additional gyro is aligned with that of the platform stabilizing gyro under test by supplying the correct voltage phase to terminals S 1  to S 4 of a resolver 14. The angular difference between the position of the gimbal 17 and the required direction of the axis 22 produces an output on terminals R 2 , R 4  which is fed to a summing point where it is combined with a signal from the pickoff 34 and fed to a torque rotor 39 to rotate the gimbal 17. During this operation the switch 44 is in position 2. It is now moved to position 1 so that the computer 45 controls the additional gyroscope and the resolver 14 is fed with further signals to rotate the gimbal through 180‹ to align the axis 22 with the input axis of the gyro under test in the 180 degrees displaced position, the switch 44 being moved to position 2 during the alignment as before. The computer 45 compares the alignment of the gyro under test with the axis 22 at the two 180 degrees displaced positions and generates a torque to correct for drift of the gyro under test. A further computer (not shown) may be used to sequentially alter the signals fed to the resolver 14 to monitor the platform stabilizing gyroscopes in turn.