GUIDANCE AND CONTROL SYSTEM FOR UNDER-ACTUATED MARINE SURFACE SHIPS AND OTHER AUTOMOMOUS PLATFORMS

摘要

A computer implemented method for guiding an under-actuated marine surface vessel in tracking a desired trajectory comprises expressing a predetermined vessel trajectory as a set of straight line segments, determining a desired current line segment, and determining the vessel's current position. A cross-track error and the derivative of the cross-track error are then determined. Next, a radius R of the line-of-sight (LOS) circle using a newly introduced exponential function is determined. Intersection points M and N between the LOS circle and the current desired line segment are determined. A desired heading angle is determined as the angle between the line of sight and a predetermined fixed reference line. A drift detection algorithm is built into the proposed guidance scheme to detect situations whereby the ship moves parallel to its desired trajectory for an extended period of time without being able to correct for the cross track error. The drift algorithm continuously monitors the ship motion relative to the desired trajectory and, upon drift detection, modifies the desired heading angle to enable the controller to compensate for the ship drift. This allows the ship to accurately track its desired trajectory.