Abstract-In this paper, we consider the development of a control strategy for path following of underactuated marine surface vessels in the presence of ocean currents. The proposed control strategy is based on a modified Line-of-Sight (LOS) guidance law with integral action and a pair of adaptive feedback controllers. Traditional LOS guidance has several nice properties and is widely used in practice for path following of marine vehicles. However, it has the drawback of being susceptible to environmental disturbances. In this work, we propose a modified LOS guidance law with integral action for counteracting environmental disturbances. Paired with a set of adaptive feedback controllers, we show that this approach guarantees global asymptotic path following of straight-line paths in the presence constant and irrotational ocean currents.

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In this paper we consider the problem of straight line path following for formations of underactuated underwater vehicles. The proposed decentralized controller makes the vehicles exponentially constitute a desired formation that follows a given straight line path with a given forward speed profile. This work builds on previous work [1] and [2] for 2D motion of 3DOF underactuated surface vessels and extends the ideas of [2] to 3D motion of 5DOF underactuated underwater vehicles. Motivated by [2], simplifying assumptions from previous works on this subject are avoided and a complete stability analysis is provided. Graph theory is used to model the inter-vehicle communication, and the proposed coordination controller respects the topological constraints of the communication network.

Summary. The problem of 3D cross-track control for underactuated 5-degrees-of-freedom (5-DOF) autonomous underwater vehicles (AUV) is considered. The proposed decentralized controllers make the AUVs asymptotically constitute a desired formation that follows a given straight-line path with a given forward speed profile. The proposed controllers consist of two blocks. The first block, which is based on a Line of Sight guidance law, makes every AUV asymptotically follow straight line paths corresponding to the desired formation motion. The second block manipulates the forward speed of every AUV in such a way that they asymptotically converge to the desired formation and move with a desired forward speed profile. The results are illustrated with simulations. IntroductionFormationc ontrol of marine vessels is an enabling technology foranumber of interesting applications. Afl eet of multiple autonomous underwaterv ehicles (AUVs) moving together in ap rescribed patternc an form an efficientd ataa cquisitionn etwork forsurveying at depths where neither diversnor tethered vehiclescan be used, andinenvironments toorisky formanned vehicles. Thisincludes forinstance oceanographic surveying at deeps ea,o perationsu nder icef or explorationo fA rctic areas ande fficientm onitoring sub-seao il installations.In this paperwestudythe problem of 3D cross-trackformation controlfor underactuated 5-DOF AUVs that arei ndependently controlledi ns urge,p itch andy aw. Roughly speaking,t his problemc an be formulateda sf ollows: givenastraight line path, ad esired formationp attern, andadesireds peed profile, c ontrol the AUVs such thata symptotically they constitute the desiredf ormationw hicht hen moves alongthe givenp athw ith thed esired speed. Ther elevance of such af ormation control problemi sj ustified by thef actt hatadesired path fora utonomousv ehicles is usually givenb ys traightlinesi nterconnecting way-points,see, e.g., [ 9].A tt he same time, thes peed profile of an autonomous vehicle is often specified independently of the desired path. This makesi tp ossible to decouple them issionp lanning into two stages:ageometricp athp lannings tage andadynamics peed assignments tage.

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This paper considers 3-dimensional cross-track control for a class of underactuated autonomous vehicles. A control strategy is presented that guarantees global κ-exponential stability of the cross-track error to straight line trajectories in three dimensional space. The results are based on a Line-of-Sight guidance algorithm and stability results are proven using nonlinear cascaded systems theory. Globally κ-exponentially stabilizing controllers are synthesized using the technique of sliding mode with eigenvalue decomposition, and the performance of the proposed control strategy is evaluated by a case study with an AUV.

Abstract-The problem of path following and formation control for underactuated 3-degrees-of-freedom surface vessels in the presence of unknown ocean currents is considered. The proposed controllers make the vessels asymptotically constitute a desired formation that follows a given straight-line path with a desired speed profile. This control goal is achieved in the presence of currents of unknown direction and magnitude. The proposed controller consists of an adaptive yaw controller, which makes every vessel converge to its desired path, and a surge controller, which guarantees formation assembly along the path with the desired forward speed. The results are illustrated by simulations.