Patent GB-639803-A (GB)
Title: Improvements in or relating to gyroscopic apparatus for defining the vertical
Inventor: BARNES JEFFERY WALTON
IPC: G01C19/44
Filed: 1947-09-20
Abstract: 639,803. Gyroscopes. MINISTER OF SUPPLY. Sept. 20, 1947, No. 25649. [Class 97 (iii)] [Also in Group XXXVIII] In gyroscopic apparatus for defining the vertical, having pendulous or like erecting means which introduce errors due to centrifugal displacement of the apparent direction of gravity during turns of the vehicle in which the apparatus is mounted, such " turn errors " are compensated by the application to the gyroscope of a precessing torque controlled by a discharging circuit to which a condenser is cyclically connected at a frequency corresponding to the rate of turn of the vehicle, after being charged from a supply voltage dependent on the vehicle forward speed. When the gyroscope turns in azimuth with the carrying vehicle, a motor applying correcting torque for " turn error " to the gyro axis has its centre tapped control winding 11 (Fig. 1) energized in the appropriate direction from a condenser 22. The condenser is first charged from a D.C. fed potentiometer 13 through brush 17 and conducting segment 21 of the commutator 20, and then discharged through brush 18 or brush 19 and one or other half of the winding 11 depending on the direction of rotation of the commutator which is driven from the 'repeater motor of an azimuth gyroscope or compass so as to rotate relatively to the brushes at a speed and in a direction dependent on the rate and sense of turn of the vehicle, and the slider of potentiometer 13 is adjusted in accordance with an airspeed indicator, so that the " turn error " compensating torque applied to' the gyroscope axis is a function of the forward speed of the vehicle and its rate and sense of turn. When the gyroscope to be corrected is stabilized in azimuth, two correcting torques are applied about two horizontal perpendicular axes fixed in relation to the gyroscope, and are derived from two voltages varying with the forward speed, and respectively with the sine . and cosine of the heading angle of the vehicle. In Fig. 2, two torque motor control windings 11a, 11b each have condenser and commutator arrangements as shown in Fig. 1. The commutators are driven, as before, in accordance with the rate of turn of the vehicle, while the voltages supplied to the commutators -are respectively derived from brushes 29a, 29b, moved by perpendicular arms 28a, 28b over a D.C. fed wire-wound resistance 24. The arms are fast about axis 27 with an azimuth stabilized member (not shown), the resistance is fast with the vehicle,-and the brushes are movable along their arms in accordance with the forward speed of the vehicle so that the torques applied about two horizontal perpendicular axes fixed relatively to the vertical defining gyroscope are functions of the forward speed and respectively of the sine and cosine of the heading angle. Fig. 3 shows a vertical defining gyroscope having a rotor 31 mounted in gimbals 32, 34 in a frame 36. If the latter is fast within the vehicle and the gyroscope is processed in azimuth to turn with the frame 36 so that the axis of gimbal 34 is fore-and-aft, the compensating torque is applied about the axis of gimbal 33 by a torque motor controlled by the arrangement of Fig. 1. If the frame 36 is stabilized in azimuth about the vertical axis 38 two torque motors controlled by the arrangement of Fig. 2 apply compensating torques about the axes of gimbals 32 and 34 which are dependent on the forward speed and on the sine and cosine of the heading angle, respectively. In a modification (Figs. 4 and 5, not shown),-for applying " turn error " correction to an azimuth stabilized vertical defining gyroscope, each torque motor has a separate untapped control winding and chargedischarge condenser, and the latter are alternately switched into the charge and discharge positions by a reversing spring set operated through lost motion gearing from a toothed wheel fast on the azimuth stabilized frame member of a vertical defining gyroscope, at a frequency dependent on the rate of turn of the vehicle. The toothed wheel also operates a switch through a friction drive to reverse the D.C. supply to the wire-wound resistor in accordance with the direction of turn, and the brushes are displaced in mutually perpendicular directions through gearing from a speedresponsive device, so that the charging voltages are varied in accordance with the forward speed of the vehicle. Specification 630,657 is referred to.