Method for controlling heading of a marine vessel

A method for controlling heading of a marine vessel having a steerable component coupled thereto, the steerable component having a propeller configured to rotate to produce thrust and being rotatable about a steering axis to affect a direction of the thrust and a direction of movement of the vessel caused by the thrust, the method being carried out by a control module and comprising:

• accepting a command to initiate a control mode in which the vessel is to be maintained at a desired heading;
• determining if the marine vessel is on-plane or off-plane;
• receiving a current heading of the marine vessel;
• determining a heading error between the current heading and the desired heading;
• in response to determining that the marine vessel is off-plane:
• (1) during a first single iteration of control, controlling the steerable component to rotate by a predetermined correction amount plus an accumulated offset amount away from a starting position in a direction that will cause the marine vessel to rotate to reduce the heading error, and subsequently to rotate back to the starting position plus the accumulated offset amount despite the heading error having been determined to be non-zero;
• (2) receiving the current heading of the marine vessel and redetermining the heading error between the current heading and the desired heading;
• (3) recalculating the accumulated offset amount as the accumulated offset amount from the previous iteration of control plus the heading error from step (2) multiplied by a gain and a time constant;
• and
• (4) during a subsequent single iteration of control, controlling the steerable component to rotate from the starting position plus the accumulated offset amount from step (1) by the predetermined correction amount plus the accumulated offset amount from step (3) in a direction that will cause the marine vessel to rotate to reduce the heading error, and subsequently controlling the steerable component to rotate back to the starting position plus the accumulated offset amount from step (3);
• (5) for as long as the marine vessel remains off-plane, subsequently repeating steps (2) through (4) until a magnitude of the heading error is less than a predetermined heading error threshold;
• and
• in response to determining that the marine vessel is on-plane, controlling a position of the steerable component using proportional, integral, derivative (PID) feedback control so as to minimize the heading error.