Autopilot Design for Track-keeping and Berthing of a Small Boat

A real time kinematic (RTK) GPS-based track-keeping and berthing control of a small boat is discussed in this work. The internal model control (IMC) method is adopted for the autopilot design. The track-keeping mission is achieved through a sequence of course-changing maneuvers and the reference heading is computed with the proposed modified 4-quadrant line-of-sight guidance law. The dynamic allocation problem associated with the multi-thruster berthing maneuver is solved by a simple empirical method that selects the proper thrusters combination to give a nearly pure sway motion. Computer simulations are carried out to determine the feasible controller parameters, which are found readily applicable in the small boat-based field tests conducted in the small boat harbour of the National Taiwan Ocean University.