GB1299822A - Self-calibrating system for navigational instruments - Google Patents

Abstract

1299822 Gyroscopic apparatus SINGER CO 1 Feb 1971 3586/71 Heading G1C To determine the drift coefficients of vertical and azimuth gyros 10, 10a of a navigation system for an airborne or space vehicle, wherein each gyro has two input axes and an outer casing 12 rotatable about an axis parallel to or coincident with its spin axis SA, and the gyros being positioned with their spin axes at an angle to each other, a precession torque is applied to the gyros to maintain their spin axes in a predetermined spatial position, and the casing 12 is rotated to predetermined angular positions, the drift coefficients about the various reference axes being computed from the precession torques for the different gyro casing angles. In Fig.2, the gyros 10, 10a are mounted on a platform 80 with their spin axes at right angles to one another. The platform 80 also carries accelerometers 82 and is supported by a vertical shaft 86 and gimbal rings 88, 90 provided with synchros 92, torque motors 94, and a resolver 96. Measurements are taken with the vertical gyro casing in three different angular positions spaced 90 degrees apart Figs.4-6 (not shown), the azimuth gyro casing remaining fixed. Finally the azimuth gyro casing is rotated through a right angle Fig. 7 (not shown). The drift coefficients are derived from the torque precession rates applied by the gyro torquers 30, said rates being the appropriate torque scale factor multiplied by the average value over 20 to 100 seconds of the torquer current, the values of which may be computor stored. Each gyro comprises a cup-shaped rotor 14 connected by a necked flexure member 24 to the shaft 18 of an electric motor 16. A permanent magnet 26 mounted on the shaft 18 balances the spring torque applied by the flexure member 24. Two pairs each of torquers 30 and pick-offs 32 are provided for the rotor. The motor 16 and casing 12 of the gyro are mounted on a turntable 40 which can be rotated in 90 degree steps by a motor 50 which is constantly energized. Rods 58, 62 projecting at 90 degree intervals round the turntable 40 periphery are engageable with a flexible stop arm 66 on the base 44, the arm being momentarily pulled down by a solenoid 68 to release the turntable for a 90 degree step.