Patent GB-829821-A (GB)
Title: Ship stabilising apparatus
IPC: G05D1/08
Filed: 1956-06-01
Abstract: 829,821. Automatic ship-stabilizing control systems. SPERRY RAND CORPORATION. June 1, 1956 [June 20, 1955], No. 16971/56. Class 38 (4). [Also in Group XXXIII] A fin stabilizing a ship about one of its primary axes is automatically controlled by signals responsive to motion of the ship about that axis and to the speed of the ship. In Fig. 1, inductive pick-offs associated with a linear accelerometer 39, a rate gyro 40 and an angular accelerometer 42 respectively develop A.C. signals dependent on the angle of roll, rate of roll, and roll acceleration of a ship. Portions of these signals determined by the setting of manually-operated potentiometers 44, 45, 46 according to weather conditions, are combined to control the position of a shaft 50 through a magnetic amplifier 47 and a servomotor 48. Positional feedback is applied to amplifier 47 from.an inductive device 55. A signal dependent on the position of shaft 50, developed by an inductive device 37, in turn controls the position of a linkage 72 through a magnetic amplifier 35 and a servomotor 34. Positional and rate feedback from servomotor 34 are applied to amplifier 35 from inductive devices 74 and 75 respectively. Linkage 72 adjusts the delivery of an electrically-driven hydraulic pump 27 supplying an hydraulic servomotor 26, so that the latter is operated to adjust, about an axis 24, the angle of a fin 20 projecting substantially horizontally from the side of the ship. Feedback dependent on the vertical force produced by fin 20 is applied to amplifier 35 from an inductive device 78 detecting longitudinal deflection of fin shaft 77. Positional feedback dependent on fin angle is applied to amplifier 35 through a potentiometer 170 from an inductive device 130. A second fin on the opposite side of the ship is controlled in a similar manner from shaft 50 and the adjustment of the two fins in opposite directions is such as to oppose the roll. A flap 22 is so mechanically linked to fin 20 that it turns through a greater angle than the fin. Correction for list of the ship may be effected by manual operation of a knob 57 associated with linear accelerometer 39. A knob 62 permits manual adjustment of limit stops 63 associated with shaft 50 and of the feedback from inductive device 74 to suit the speed of the ship. A linkage 84 limits adjustment of pump 27 when hydraulic servomotor 26 reaches limiting positions. When a switch 133 is operated to disable the system the output of inductive device 130 is connected to the input of amplifier 35 so that the fin is driven to a central angular position in readiness for stowage. Hydraulic servomotors 29, 30 may then be operated remotely to move the fin about a substantially vertical axis into a cavity (not shown) formed in the hull of the ship. The fins are maintained in their operating or stowed position by hydraulicallyoperated spring-loaded latches (not shown). Electrical interlocks and indicators to facilitate correct stowage are described. In one modification a signal representative of the vertical force on the fin is derived from inductive pick-offs responsive to the horizontal force on a bearing provided for the stowing movement about a vertical axis. Signals representative of the vertical force on the fin may also be derived from suitably located strain gauges. The fins may alternatively project substantially vertically downward from the ship's bottom. Specification 829,822 is referred to.