US 2013/0173096 A1 · GUIDANCE AND CONTROL SYSTEM FOR UNDER-ACTUATED MARINE SURFACE SHIPS AND OTHER AUTONOMOUS PLATFORMS

Abstract

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.

Claims16

Dependent claims

A computer implemented method for guiding and controlling a trajectory of an under-actuated vessel, the method comprising:

a) expressing a predetermined vessel trajectory as a set of straight line segments;
b) determining a desired current line segment [Ai, Ai+1];
c) determining the vessel's current position;
d) determining a cross-track error d and the time derivative of the cross-track error;
e) calculating the radius R of the line-of-sight (LOS) circle using formulae:
R=d+√2R′mine−bx′B (1a)
R′min=2−−0.5Rmine2−0.5bRmin (1b)
x′B−b−1[lambertw(bR′mine−(0.5√2bd))+0.5√2bd] (1 c)
wherein lambertw is the inverse of f(x)=xex;
and
Rmin is the minimum radius;
f) determining intersection points M and N between the LOS circle and the current desired line segment [Ai, Ai+1], the intersection points M, N defining a line segment [M, N] having the same sense as the [Ai, Ai+1] wherein N is the forward looking point;
g) determining a desired heading angle to be the angle between line ON and a fixed reference line;
and
h) inputting the desired heading angle to a vessel's heading controller.

12 more elements

A system comprising a computer processor, memory, and digital storage devices, the computer processor executing a method comprising:

a) expressing a predetermined vessel trajectory as a set of straight line segments;
b) determining a desired current line segment [Ai, Ai+1];
c) determining the vessel's current position;
d) determining a cross-track error d and the time derivative of the cross-track error;
e) calculating the radius R of the line-of-sight (LOS) circle using formulae:
R=d+√2R′mine−bx′B (1a)
R′min=2−−0.5Rmine2−0.5bRmin (1b)
x′B−b−1[lambertw(bR′mine−(0.5√2bd))+0.5√2bd] (1 c)
wherein lambertw is the inverse of f(x)=xex;
Rmin is the minimum radius;
and
b is a parameter controlling the decay rate of the exponential term;
f) determining intersection points M and N between the LOS circle and the current desired line segment [Ai, Ai+1], the intersection points M, N defining a line segment [M, N] having the same sense as the [Ai, Ai+1] wherein N is the forward looking point;
g) determining a desired heading angle to be the angle between line ON and a fixed reference line;
and
h) inputting the desired heading angle to a vessel's heading controller.

13 more elements

Dependencies are inferred from the claim text.

Guidance and control system for under-actuated marine surface ships and other autonomous platforms

Life of this patent

Guidance and control system for under-actuated marine surface ships and other autonomous platforms

Life of this patent

Abstract

Claims16