Every ship has on board a wide range of hydraulically actuated systems and equipment. A typical example is offered by the holds' hatch covers system presented below, actuated by a hydraulic linear actuator.
In this case the cylinder has to be very large in order to manage smoothly lifting the hatch weight. This is due to the large force necessary for lifting, which is within the range of mega-newton.
The model and animations below are built using the Hydraulics Library and Dymola .
The animation speed is 10 times higher than the real.
The proportional valve controls the flow from the pump to the cylinder, actuating the hatch cover. The long line captures dynamics due to large flows, as seen at 50 seconds.
Top wheel position and hydraulic cylinder force. Note the dynamical effects at 50 seconds and the magnitude of the forces when the hatch cover is lowered.