Patent GB-797929-A (GB)
Abstract: 797,929. Electric correspondence control. SPERRY RAND CORPORATION. Feb. 2, 1956 [Feb. 8, 1955], No. 3330/56. Class 40 (1). A gyroscopic apparatus comprises a member 2 pivotally mounted in a, supporting frame about an axis, a gyroscope associated with the member 2 for stabilizing the member 2 against angular rotation about said axis, a torque motor associated with the gyroscope mounted so as to be capable when energized of applying a torque to the gyroscope, to cause the gyroscope to process about an axis normally parallel to the first axis, the arrangement being such that when the gyroscope precesses in response to an applied torque the member is caused to follow it about its axis, a reference device for defining a direction with which the member is to be kept aligned. about its axis and For controlling the energization of the torque motor associated with the gyroscope to cause precession of the gyroscope in dependence on misalignment between the reference direction and the member, a second torque motor so mounted as to be capable on energization of applying a torque between the member 2 and its supporting frame about the axis of the member and means for quickly bringing the member 2 into alignment with the direction defined by the reference device including means for temporarily causing the reference device to control the energization of the second torque motor. As shown the member 2 is a platform which is rotatably mounted about a normally vertical axis by means of a shaft 4 journalled in bearings 6 of a ring 8. The ring 8 in turn is journalled for rotation about a normally horizontal axis 10 in a ring 12 and the ring 12 is journalled for rotation about a second normally horizontal axis 14 in a ring 18 which in turn is mounted for rotation about a horizontal axis 20 in main supports 22. The axis 10 is in line with the axis 20. Three gyroscopes 34, 46, 60 are mounted on the member 2. The gyroscope 34 has its rotor 36 mounted in a vertical ring 41 for spinning about a horizontal axis 38 parallel to the axis 14 and the ring 41 can rotate about a vertical axis 40 in a supporting frame .42, the rotation being limited by stop pins 43 in the path of an arm 82 secured to the ring 41. The gyroscope 46 is identical with the gyroscope 34, but its axis is arranged parallel with the axis 10. The gyroscope 60 is similar but the ring supporting the gyroscope rotor is mounted for rotation about a horizontal axis 64. Precession of the gyroscope 34 about the axis 40 is controlled by a liquid level reference device 48 which is mounted on the platform member 2 and the precession of the gyroscope 46 is similarly controlled by a liquid level reference device 50. The reference device 48 is responsive to tilt of the platform member about the horizontal axis 10 and the reference device 50 is responsive to tilt of the platform member about the horizontal axis 14. The precession of the gyroscope 64 about its axis 64 is controlled by a compass reference device 62 which is in the form of a flux valve. The reference device 48 is arranged in a bridge circuit and the output of the bridge is connected through an amplifier 51 to a torque motor 52 which precesses the gyroscope 34 about its axis 40 so that the platform member is tiled about the axis 10 in a direction opposite to the original tilt so as to maintain the platform member level. Due to friction some precession of the gyroscope 34 about its vertical axis in the direction of the applied torque will occur and this is detected by a pick-off 54 and used to control a torque motor 28 which acts between the ring 12 and the member 2 on the axis 10 and assists the gyroscope 34 in keeping the platform member level. The liquid level reference device 50 similarly controls a torque motor 53 on the gyroscope 46 to keep the platform level about the axis 14 and the gyroscope 46 similarly has a pick-off 56 which controls a torque motor 30 which acts between the rings 12 and 18 to assist the gyroscope 46. Since the platform member 2 is maintained fixed in azimuth by the gyroscope 60 and hence is rotatable with respect to the axis 20 of the ring 18 which is fixed on the aircraft or ship, a resolver 58 is necessary between the torque motors 28 and 30 and one part 57 of this is mounted for turning about the vertical axis 4 of the platform member and the other part 59 is fixed to the ring 8. The resolver receives its input from amplifiers 78 and 80 respectively connected to the pickoffs 54 and 56 and its outputs are fed to the torque motors 28 and 30 through amplifiers 90, 90<SP>1</SP>. The flux valve 62 which controls the gyroscope 60 for maintaining the member 2 in azimuth is connected to a selsyn generator 63 which is geared to the vertical shaft 4. When the member 2 deviates from its proper position in azimuth a signal is generated in the winding 65 which after amplification in amplifier 51<SP>11</SP> controls a torque motor 67 which causes the gyroscope 60 to precess in azimuth carrying with it the platform member. Similarly to the other gyroscopes the gyroscope 60 has a pick-off 66, the output of which is applied through amplifiers 79 and 90<SP>11</SP> to a torque motor 32 which acts between the ring 8 and the shaft 4 to assist the gyroscope 60 in maintaining the member 2 in azimuth. The outer ring 18 is stabilized about its axis 20 by a torque motor 24 which is controlled by a pick-off 26 mounted on ring 12 and responsive to relative tilt of the ring 8 within ring 12. Each gyroscope control circuit is provided with a switch 70, 72, 74; in the case of the reference device 48 the switch 70 disconnects the output of the amplifier 51 from the torque motor 52 and instead connects it to the amplifier 78 so that the reference device 48 controls the torque motor 28 directly; similarly the reference device 50 is disconnected from the torque motor 53 and instead is connected directly to the torque motor 30; the flux valve 62 is similarly connected by the switch 74 so that it controls the torque motor 32 directly. The switches 70, 72 and 74 are operated from a single button and enable the platform member 2 to be quickly levelled and brought into azimuth when starting up. In a modification the switches are arranged to connect the inputs of the amplifiers 78, 80 and 79 in parallel with the torque motors 52, 53 and 67 respectively since the torque exerted by the motors is small and does not effect the quick erection of the member 2. During the quick erection of the apparatus the torques initially exerted by the motors 28, 30 and 32 will cause the gyroscopes to bring their arms 82 against the fixed stop pins 43 and as soon as this happens the gyroscopic resistance will be removed so that the erection can proceed quickly and to prevent oscillation of the platform member the outputs of the pick-offs 54, 56 and 66 remain connected to the amplifiers 78, 80 and 79 respectively; these outputs oppose the outputs of the reference devices so as to damp the oscillation of the platform member. In addition centralizing compression springs 44, 45 are provided on the stop pins and these are engaged by the arms 82 before the stop pins 43 are engaged. A clearance is provided between the ends of the compression springs and the end of each arm 82 so that the precession of each gyroscope is unrestrained during normal operation. The switches 70, 72 and 74 are operated by the push-button through a solenoid and are released by a timing mechanism 84 after a predetermined delay period. In a modification, Fig. 4 (not shown), the ring 8 is contained in a spherical case and one of the liquid level reference devices is on the bottom of the case secured to the ring 8 and the other is on a bail secured to the ring 12. When mounted in this manner the devices are responsive to tangential accelerations due to the angular acceleration of the platform member about its axis as it is being erected and the tangential acceleration tends to oppose the acceleration of gravity on the liquid level devices to give an inertia damping effect. Specification 608,851, [Group XXXV], and U.S.A. Specification 2,519,697 are referred to.