Patent ID: 7305928
Filing Date: 2007-12-11
Classification: B63H

Abstract:
1. A method for maintaining a marine vessel in a selected position, comprising the steps of: providing a first marine propulsion device which is rotatable about a first steering axis; providing a second marine propulsion device which is rotatable about a second steering axis; determining a current global position of said marine vessel; determining a current heading of said marine vessel; receiving a signal command to maintain the current global position and the current heading of said marine vessel; storing said current global position and heading of said marine vessel as a target global position and a target heading in response to receiving said signal command; determining a subsequent global position of said marine vessel; determining a subsequent heading of said marine vessel; calculating a position error difference between said subsequent global position and said target global position; calculating a heading error difference between said subsequent heading and said target heading; determining required marine vessel movements to minimize said position error difference and said heading error difference; resolving said required marine vessel movements into a target linear thrust and a target moment about a preselected point of said marine vessel; determining a first rotational position of said first marine propulsion device about said first steering axis, a second rotational position of said second marine propulsion device about said second steering axis, a first magnitude and first direction of thrust for said first marine propulsion device, and a second magnitude and second direction of thrust for said second marine propulsion device which will result in achievement of said target linear thrust and said target moment about said preselected point of said marine vessel; rotating said first and second marine propulsion devices to said first and second rotational positions about said first and second steering axes, respectively; causing said first and second marine propulsion devices to produce said first and second magnitudes and directions of thrust, respectively; and providing a manually operable control device which is configured to provide an output signal which is representative of a desired movement of said marine vessel, said signal command receiving step being performed only upon an initial change from activity to inactivity of said manually operable control device.