Patent GB-1137691-A (GB)
Title: Automatic control of ship propulsion units
IPC: B63H21/22
Filed: 1966-10-05
Abstract: 1,137,691. Automatic control for ship propulsion. GENERAL ELECTRIC CO. Oct. 5, 1966 [Oct.6, 1965], No.44461/66. Heading G3R. A ship is provided with steam turbine 93 coupled to propeller 131, a throttle lever 23 on the bridge generating a reference signal for setting the magnitude and sense of the turbine power output. A response signal representing the actual power output is compared with the reference signal, the steam valves being controlled to reduce any error. The power response may be detected by measuring the actual position of the steam valve or the propeller speed. The throttle lever 23 is connected to potentiometer 73 applying a linear signal to function generator 79 whose output is a cubic function of the original reference signal. A summing amplifier 81 receives the signal from generator 79 and controls pilot motor 87 which actuates the ahead steam valve 89. Potentiometer 85 senses the position of the valve and feeds back a signal to amplifier 81, the valve motor being stopped when the feedback and reference signals cancel each other. The rate of adjustment is fixed by circuit 95 which determines the maximum current fed to motor 87. An engine room throttle potentiometer produces a corresponding reference signal to control the turbine in a similar manner. The astern steam valve is likewise regulated when the reference signal from potentiometer 71 or 73 changes sign. The propeller speed may be used as a feedback by closing selector switch 135 when the throttle lever is moved to the stop or astern position from the ahead position. The reference signal is reduced to zero, the signal from tachometer 127 indicating that the propeller is still rotating due to inertia. The astern steam valve is opened and closed at short intervals until the ship's momentum is reduced so that the propeller no longer rotates due to drag. The sensitivity of the speed feedback amplifier 129 or 130 is increased when the throttle lever is moved to the stop position. Throttle control is transferred between bridge and engine room by actuating contacts 75, 77. If the pressure in the turbine falls below a safe level, amplifier 143 over-rides the other signals to close the steam valves. The transfer from engine room to bridge cannot take place unless the throttle positions are matched by a bridge circuit comprising potentiometers actuated by the respective levers and associated with relays which prevent the transfer unless the bridge circuit is balanced. With the engine room in control of the turbine, the bridge throttle lever should be in the "off" position. If it is moved from this position, an alarm bell is energized. If the propeller shaft is rotated at less than one revolution per minute, an indicating lamp is energized and an alarm bell sounded. When the shaft is above this speed, pulses from a proximity switch which detects the passage of the propeller-blade will reset a counter, and thus counter-act pulses from contacts driven by a timer motor, so preventing the alarm relays from picking-up. The operational characteristic of the function generator is such that its output is in linear relationship with an input signal when the throttle lever is moved slightly from a neutral position, thus establishing a first slope of the characteristic. As the reference voltage increases to provide a first change-over point a second path is automatically introduced into the input circuit comprising a rheostat in series with a diode which is connected to one of a number of potentiometers fed with constant current through a transistor Zener diode network. The number of parallel paths is increased as the input signal increases, the slope changing with each change-over point. In another arrangement, the power response is measured in accordance with torque, from a thrust meter, from electrical energy on an electrical drive, or from a log measurement. The first stage turbine pressure may also be used for this purpose. If the ship is driven by a diesel engine, the fuel rack position affords an indication of the power response.