Autopilot System Based on Color Recognition Algorithm and Internal Model Control Scheme for Controlling Approaching Maneuvers of a Small Boat

This paper designs and develops an autopilot system for guiding the trajectory of a small boat as it performs an approaching maneuver within a harbor. In the proposed approach, two canvas targets are arranged in cascade on the berth to serve as leading marks to define the leading line along which to guide the boat toward the berthing standby region. The leading marks are captured by a charge-coupled device (CCD) camera mounted on the bow of the boat, and the resulting image is processed using a color recognition scheme to identify the hue (H) and saturation (S) components. The H- and S-component images are subsequently processed using a noise filtering scheme to accurately detect the location of the two targets in the image. The centers of gravity (CGs) of the two leading marks are then calculated, and the separation distance between them is used to compute the deviated heading angle. This angle is then supplied to an internal model control (IMC) autopilot system as an error signal and is used to generate appropriate control commands to steer the boat toward the leading line. The feasibility of the autopilot system is verified by performing a series of experimental approaching maneuvers using a small boat in a real-world harbor setting.