840,371. Stabilising ships. RESEARCH INTERESTS Ltd. (Steinen C. von den and Montrose-Oster, L. E. W.). May 17, 1956 [May 17, 1955; May 14, 1956], Nos. 14213/55 and 14943/56. Class 113. Control apparatus for stabilising the mast of a ship to an arbitrarily chosen reference line comprises pendulum gyroscope 24 detecting the true vertical and a pendulum detector 27 of the apparent vertical, a servo-motor 16, and a platform 5 pivoted about a longitudinal axis 11 of the ship. The platform 5 is moved in accordance with the output of the servomotor through a link 17 while movement of a link 19 provides the input to the servo-motor. The link 19 is connected to the point 20 of a lever 21 one end of which is connected by link 22 to the ring 23 of the pendulum gyroscope 24 while the other end is connected by a link 25 to a lever 26 moved in accordance with movement of the dector 27. The arm 7 of a transmitter 6 secured to the platform 5 is connected by a link 29 to the other end of detector 23 while the arm 14 of a transmitter 15 secured to the ship is connected to a lever 11 one end of which is secured to the platform while the other end is joined by link 30 to the other end of lever 26. The ratio of the input of the servomotor 16 to the output is controlled by a member 32 such that this ratio is 1 : 1 when the arm points to '1' on the scale 35 and the output is zero when the arm points to '0'. Transmitters 8 and 9 are mounted on the platform and measure the angular velocity and acceleration of movements relative to space of the platform 5. The outputs of the transmitters 7, 8, 9 and 15 are fed to a control device 31 which controls the movements of the stabilisers. In operation, assuming that the mast of the ship is in an arbitrary position and that a wave is acting on the ship, the pendulum 27 moves to indicate the angle # 2 between the mast and the apparent vertical and thus the lever 26 rotates a relative amount and through elements 30, 11, 12, 13 moves the arm 14 of transmitter 15 to produce a control output proportional to # 2 . Similarly the ring 23 of gyroscope 24 moves to indicate the angle # 1 , between the mast and the true vertical and through element 29 moves the arm 7 of transmitter 6 to produce a control output relative to # 1 . Both of these control outputs are combined in the control device and thus produce a control output relative to the angle # between the true and apparent verticals. However movement of the indicators 27, 23 also produce through elements 26, 25, 21 20 and 22, 21, 20 respectively a movement of links 19 proportional to # and, depending on the setting of the arm 32 of the servomotor, the link 17 moves an amount, which is a fixed proportion of the movement of 19, to tilt the platform 5 about its pivot 1<SP>1</SP>. Movement of the platform 5 varies the control output of transmitter 6 attached to it and also varies the control output of transmitter 15 through the movement of the end 10 of the platform and lever 11. Thus the combined result produces a control output proportional to the angle # between the true and apparent verticals, this proportion depending upon the setting of the servomotor arm 32, which determines the reference line to which the ship is to be stabilised, the control device 31 applying a correcting couple through the stabilisers. When the arm 32 points to '0' on the scale 35 there is no output from the servomotor 16 and the platform 5 is fixed. The reference line then becomes the true vertical. If the arm 32 points to '1' on the scale the output of the servo-motor is equal to the input and the reference line becomes the apparent vertical. Values on the scale between '0' and '1' thus correspond to the reference line between these two verticals. A further control output is also supplied to the device 31 through the transmitters 8, 9 which measure the angular velocity and acceleration of the platform 5 relatively to space. The transmitters 6, 15 may be combined as a single unit the ring of which is attached to the platform and the rotor of which is moved proportional to the angle between the true and apparent verticals. Alternatively, the ring may be separate from the platform and the rotor moved by the output of a servomotor or servo-motors receiving the combined input or inputs of the detector.