Steering system having steering angle correction function for single-propeller twin-rudder ship

A steering system having a steering angle correction function for a single-propeller twin-rudder ship, wherein:

• in a single-propeller twin-rudder ship comprising a propulsion propeller disposed at a stem of the ship, a pair of right and left high-lift rudders disposed behind the propulsion propeller, a pair of rotary vane steering gears for driving each of the high-lift rudders, respectively, a steering controller for controlling a direction of a hull motion by combining rudder angles of the two high-lift rudders, a ship speed measuring device that measures a ship speed of an own ship, a position measuring device that measures a ship position of the own ship, and an azimuth measuring device that measures a heading of the own ship,
• the steering controller has an electronic marine chart display section that displays a navigational electronic marine chart on a display device, a rudder angle specifying section that applies a specified rudder angle to each of the rotary vane steering gears, a course line setting section that sets a planned route of the own ship on the navigational electronic marine chart, and a maneuvering support section that calculates an appropriate steering angle that is necessary for navigation on the planned route and outputs the appropriate steering angle that is calculated as a specified rudder angle to the rudder angle specifying section, and
• the maneuvering support section has a digital twin computation section, a simulation computation section, a resultant force of external forces computation section, and a specified rudder angle computation section,
• wherein:
• the digital twin computation section collects in real time a ship speed of the own ship measured by the ship speed measuring device, a ship position of the own ship measured by the position measuring device, and a heading of the own ship measured by the azimuth measuring device, and reproduces, on the navigational electronic marine chart, an actual hull motion of the own ship that is realized at a current steering angle;
• the simulation computation section displays, on the navigational electronic marine chart, an assumed hull motion of the own ship determined by computation assuming that a force acting on the hull is a driving force at the current steering angle;
• the resultant force of external forces computation section calculates an acting direction and a magnitude of a resultant force of external forces acting on the hull based on a ship speed difference, a ship position difference, and a heading difference between the actual hull motion and the assumed hull motion;
• and
• the specified rudder angle computation section calculates a corrective rudder angle for resisting the resultant force of external forces, and corrects the current steering angle with the corrective rudder angle to calculate an appropriate steering angle necessary for navigating the planned route resisting the external forces.