Station keeping methods

A method for maintaining orientation of a marine vessel in a body of water, the vessel being propelled by first and second marine propulsion devices powered by first and second engines, respectively, the method comprising:

• accepting a command to maintain the vessel at an initial selected heading;
• utilizing heading feedback control to determine initial steering angles, initial gear positions, and initial engine speeds for the first and second propulsion devices, respectively, which result in the first and second propulsion devices together producing a resultant moment about a preselected point on the vessel that counteracts a net external moment on the vessel and maintains the vessel at the initial selected heading;
• rotating the vessel to a new selected heading;
• accepting a command to maintain the vessel at the new selected heading;
• utilizing information related to one of the heading feedback control and the resultant moment to predict control parameters required to maintain the vessel at the new selected heading;
• and
• controlling the first and second propulsion devices according to the predicted control parameters to maintain the vessel at the new selected heading.

A method for maintaining position and orientation of a marine vessel in a body of water, the marine vessel being propelled by first and second marine propulsion devices powered by first and second engines, respectively, the method comprising:

• determining initial steering angles, initial gear positions, and initial engine speeds for the first and second propulsion devices, respectively, which result in the first and second propulsion devices together producing a resultant linear thrust vector that counteracts a net external force on the vessel and maintains the vessel in an initial selected position, and which result in the first and second propulsion devices together producing a resultant moment about a preselected point on the vessel that counteracts a net external moment on the vessel and maintains the vessel at an initial selected heading;
• propelling the vessel to a new selected position;
• rotating the vessel to a new selected heading;
• accepting a command to maintain the vessel at the new selected position and at the new selected heading;
• calculating new steering angles, new gear positions, and new engine speeds for the first and second propulsion devices, respectively, that will result in the first and second propulsion devices together creating the same resultant linear thrust vector that was required to counteract the net external force on the vessel at the initial selected position and the same resultant moment that was required to counteract the net external moment on the vessel at the initial selected heading;
• and
• rotating the first and second propulsion devices to the new steering angles, respectively, placing the first and second propulsion devices in the new gear positions, respectively, and causing the first and second engines to rotate at the new engine speeds, respectively, to produce the same resultant linear thrust vector and the same resultant moment and maintain the vessel at the new selected position and the new selected heading.