Line-of-Sight Path Following for Dubins Paths With Adaptive Sideslip Compensation of Drift Forces

Abstract

Abstract-We present a nonlinear adaptive path-following controller that compensates for drift forces through vehicle sideslip. Vehicle sideslip arises during path following when the vehicle is subject to drift forces caused by ocean currents, wind and waves. The proposed algorithm is motivated by a lineof-sight (LOS) guidance principle used by ancient navigators, which is here extended to path following of Dubins paths. The unknown sideslip angle is treated as a constant parameter, which is estimated using an adaptation law. The equilibrium points of the cross-track and parameter estimation errors are proven to be uniformly semiglobally exponentially stable (USGES). This guarantees that the estimated sideslip angle converges to its true value exponentially. The adaptive control law is in fact an integral LOS controller for path following since the parameter adaptation law provides integral action. The proposed guidance law is intended for maneuvering in the horizontal-plane at given speeds and typical applications are marine craft, autonomous underwater vehicles (AUVs), unmanned aerial vehicles (UAVs) as well as other vehicles and craft where the goal is to follow a predefined parametrized curve without time constraints. Two vehicle cases studies are included to verify the theoretical results.

Predictor-based LOS guidance law for path following of underactuated marine surface vehicles with sideslip compensation

“…In this subsection, we derive a predictor-based adaptive law to estimate sideslip angle by treating it as an unknown constant parameter as in Fossen et al (2014). The update law for β based on the prediction errors is designed as follows…”

“…The LOS guidance principle has been widely used in path following and its properties have been thoroughly studied in the literature (Lee et al, 2010;Oh and Sun, 2010;Bϕhaug et al, 2008;Lekkas and Fossen, 2014;Fossen et al, 2014). The main idea of LOS guidance is to mimic the actions of a helmsman, which steer the vehicle towards a lookahead distance ahead of the projection point of the vehicle along the path.…”

“…To tackle the sideslip angle issue and compensate for its influence, some efforts have been made by researchers (Hac and Simpson, 2000;Bϕhaug et al, 2008;Lekkas and Fossen, 2014;Fossen et al, 2014). The straightforward solution to solve this problem is to measure the sideslip angle.…”

“…The third method is the adaptive LOS (ALOS) guidance, which treats the sideslip angle as an unknown constant parameter to be estimated. In Fossen et al (2014), an ALOS guidance law is proposed and the sideslip angle can be identified by an adaptive term on line. However, the ALOS guidance law may inherit the weaknesses of the standard adaptive control method; which can be stated as follows.…”

Path Following Control of the Underactuated USV Based On the Improved Line-of-Sight Guidance Algorithm

“…An optimal controller is proposed for the integrated path following and roll motion control problem in [13], where the line-ofsight (LOS) technique is used to extend straight-line path following to arbitrary path following. A nonlinear adaptive path following controller which can compensate drift forces through vehicle sideslip is presented in [14]. In that paper the proposed algorithm, motivated by the LOS guidance principle used by ancient navigators, is extended to Dubins path following.…”