Morten Breivik

Line-of-Sight Path Following of Underactuated Marine Craft

Abstract A 3 degrees of freedom (surge, sway, and yaw) nonlinear controller for path following of marine craft using only two controls is derived using nonlinear control theory. Path following is achieved by a geometric assignment based on a line-of-sight projection algorithm for minimization of the cross-track error to the path. The desired speed along the path can be specified independently. The control laws in surge and yaw are derived using backstepping. This results in a dynamic feedback controller where the dynamics of the uncontrolled sway mode enters the yaw control law. UGAS is proven for the tracking error dynamics in surge and yaw while the controller dynamics is bounded. A case study involving an experiment with a model ship is included to demonstrate the performance of the controller and guidance systems.

Principles of Guidance-Based Path Following in 2D and 3D

This paper treats the subject of fundamental guidance principles related to motion behaviour in a 2D plane and a 3D space. In this context, the concept of guidance-based path following is defined and elaborated upon. Its specifies are contrasted towards the already established concept of trajectory tracking. Specifically, guidance laws are developed at an ideal, dynamics-independent level to yield generally valid laws uninfluenced by the particularities of any specific dynamics case. These laws can subsequently be tailored to actual target systems like e.g. watercraft or spacecraft, for instance in a cascaded setting. The approach renders all regular paths feasible. Possible applications and extensions to the guidance-based path following scheme are also briefly suggested.

Path following for marine surface vessels

This paper addresses the problem of path following for marine surface vessels by utilizing a novel guidance-based approach. The approach is equally applicable for land, sea and air vehicles. The main idea is to explicitly control the velocity vector of the vehicles in such a way that they converge to and follow desired geometrical paths in a natural and elegant manner. In this regard, all regular paths are feasible. A nonlinear model-based controller is designed for a fully actuated vessel to enable it to comply with the guidance commands. The vessel is exposed to a constant environmental force, hence integral action is added by means of parameter adaptation. By introducing sideslip compensation and a dynamic controller state, the results are extended to underactuated vessels

Path following of straight lines and circles for marine surface vessels

Abstract This paper addresses the problem of path following for marine surface vessels. A guidance-based approach which is equally applicable for land, sea and air vehicles is presented. The main idea is to explicitly control the velocity vector of the vehicles in such a way that they converge to and follow the desired geometrical paths in a natural and elegant manner. Specifically, straight lines and circles are considered. A nonlinear modelbased controller is designed for a fully actuated vessel to enable it to comply with the guidance commands. The vessel is exposed to a constant environmental force, so integral action is added by means of parameter adaptation. A full nonlinear vessel model is used in the design. By introducing sideslip compensation and a dynamic controller state, the results are extended to underactuated vessels.

Guidance Laws for Autonomous Underwater Vehicles

A mix between a monograph and an article collection, this PhD thesis considers the concept of guided motion control for marine vehicles, in particular focusing on underactuated marine surface vehicles. The motion control scheme is defined to involve the combination of a guidance system which issues meaningful velocity commands with a velocity control system which has been specifically designed to take vehicle maneuverability and agility constraints into account when fulfilling these commands such that a given motion control objective can be achieved in a controlled and feasible manner without driving the vehicle actuators to saturation. Furthermore, motion control scenarios are classified in a novel way according to whether they involve desired motion which has been defined a priori or not. Consequently, in addition to the classical scenarios of point stabilization, trajectory tracking, path following and maneuvering, the so-called target tracking scenario is considered. The resulting scenarios then involve target tracking, path following, path tracking and path maneuvering. In addition, it is proposed to define the control objectives associated with each scenario as work-space tasks instead of configurationspace tasks. Such a choice seems better suited for practical applications, since most vehicles operate in an underactuated configuration exposed to some kind of environmental disturbances. The thesis also proposes a novel mechanization of constant bearing guidance, which is a classical guidance principle well-known in the guided missile literature. This suggestion is motivated by a need to solve the target tracking motion control objective for marine vehicles. The proposed implementation enables explicit specification of the transient rendezvous behavior toward the target by selection of two intuitive tuning parameters. In addition, a singularity-free guidance law applicable to path following scenarios involving regularly parameterized paths which do not need to be arc-length parameterized is proposed. An extension to this guidance law is also suggested in order to enable off-path traversing of regularly parameterized paths for formation control purposes. A novel velocity control system which inherently takes maneuverability, agility and actuator constraints into account is developed for the purpose of controlling underactuated marine vehicles moving at high speed. The system is derived through a design method which involves a control-oriented modeling approach and requires a minimum of system identification tests to be carried out. The thesis also gives a novel overview of the major developments in marine control systems as seen from a Norwegian perspective. The development can be viewed as three waves of control, where the first wave concerned development of novel ship automation technology in the 1960s and 1970s, the second wave involved development of unique dynamic positioning systems in the 1970s and 1980s, while the third wave is expected to encompass the development of unmanned vehicle technology for a large number of maritime applications. A summary of the historical development, present status and future possibilities associated with unmanned surface vehicles (USVs) is also given. Current Norwegian activities are particularly emphasized. Furthermore, an overview of the main formation control concepts applicable to marine surface vehicles is given. A novel formation control functionality named coordinated target tracking is subsequently suggested within a leader-follower framework. Employing a guided motion control system using the suggested mechanization of constant bearing guidance, this functionality is then implemented for two different types of underactuated USVs such that they are able to move in formation with a leader vessel which can maneuver freely without being constrained to any predefined motion pattern. In particular, excerpts from successful full-scale formation control experiments involving a manned leader vessel and the two USVs executing coordinated target tracking at high speed are presented. This functionality currently seems to be unique on a worldwide basis, providing a convenient plug-and-play formation control capability for manned leader vessels involved in maritime survey operations.

Guidance laws for planar motion control

This paper gives an overview of guidance laws that can be applied for planar motion control purposes. Considered scenarios include target tracking, where only instantaneous information about the target motion is available, as well as path scenarios, where spatial information is available a priori. For target-tracking purposes, classical guidance laws from the missile literature are reviewed. These laws encompass guidance principles such as line of sight, pure pursuit, and constant bearing. For the path scenarios, enclosure-based and look-ahead-based guidance laws are presented. Considered paths include straight lines (zero curvature), circles (constant curvature), as well as general, regularly parameterized paths (variable curvature). Also, relations between the guidance laws are discussed, as well as interpretations toward saturated control.

Guidance-based path following for autonomous underwater vehicles

This paper addresses the problem of path following for autonomous underwater vehicles (AUVs) by utilizing a novel guidance-based approach. Termed guidance-based path following, the proposed approach is equally applicable for sea, land and air vehicles. This relates to the fact that the core guidance laws are developed at an ideal, dynamics-independent level, entailing generally valid laws uninfluenced by the particularities of any specific dynamics case. The laws can subsequently be tailored to specific target systems like AUVs. A nonlinear, model-based velocity and attitude controller, which depends fully on the guidance system reference signals in order to fulfil the guidance-based path following task objectives, is proposed for the purpose of controlling both fully actuated and underactuated AUVs. The resulting guidance and control scheme renders all regular paths feasible, and simulation results successfully demonstrate its capability.

Ship Formation Control: A Guided Leader-Follower Approach

Abstract This paper considers the topic of formation control for fully actuated ships. Within a leader-follower framework, a so-called guided formation control scheme is developed by means of a modular design procedure inspired by concepts from integrator backstepping and cascade theory. Control, guidance, and synchronization laws ensure that each individual formation member is able to converge to and maintain its assigned formation position such that the overall formation is able to assemble and maintain itself while traversing an arbitrary, regularly parameterized path that is chosen by a formation control designer. A key novelty of the approach is the derivation of guidance laws that are applicable to off-path traversing of curved paths. The helmsman-like transient motion behavior associated with the scheme is illustrated through a computer simulation involving three fully actuated ships.

A unified control concept for autonomous underwater vehicles

This paper addresses the problem of creating a controller structure for the automatic control of autonomous underwater vehicles (AUVs) through their entire non-zero speed regimes, without resorting to switching between structurally different controllers. A single controller structure is proposed for the purpose, whose core is a nonlinear, model-based velocity and attitude controller that relies on a key guidance-based path following concept necessary to ensure geometric path convergence. The scheme renders all regular paths feasible, and ensures that an AUV which is fully actuated at low speeds, but becomes underactuated at high speeds, is able to converge to and follow a desired geometric path independent of the current vehicle speed

APPLYING MISSILE GUIDANCE CONCEPTS TO MOTION CONTROL OF MARINE CRAFT

Abstract This paper considers employing missile guidance concepts to design motion control systems for marine craft. Initially, classical concepts such as line of sight (LOS), pure pursuit (PP), and constant bearing (CB) are reviewed. Subsequently, the relationship of these concepts to motion camouflage strategies in nature is pointed out, as well as their application to robot manipulators. Ultimately, the CB guidance scheme is used to design a motion control system for fully actuated marine surface craft. For this purpose, the notion of asymptotic interception becomes fundamental, as the motion control goal is not to hit a physical target in finite time, but to hit a virtual target asymptotically. A modular control design inspired by backstepping and cascade theory results in a classical inner-outer loop guidance and control structure.