A Bottom-Following Preview Controller for

Autonomous Underwater Vehicles

Carlos Silvestre, Rita Cunha, Nuno Paulino, and António Pascoal

By:

Ahmed El Sheikh

MSc Student, Mechatronics and Robotics, Sghool of Innovative Design, E-JUST

ahmad.elsheikh@hotmail.com

Carlos Silvestre: PhD, (IST), Lisbon,

Portugal.

Rita Cunha: PhD, (IST), Lisbon,

Portugal.

Nuno Paulino: M.Sc, (IST),

Lisbon, Portugal.

António M. Pascoal, PhD,

(IST), Lisbon, Portugal

Overview

• State of The Art

• Vehicle Dynamics

• Error Space

• Preview Problem Formulation• Preview Problem Formulation

• Discrete Time Controller Design

• Reference Path

• Implementation

• Simulation Results

State of The Art

• Solving the problem of bottom –following for AUV

• Using the echo sounders to evaluate the terrain

characteristics

• AUV linearized error dynamics for a pre-defined set of

operating regionsoperating regions

• Using the LMIs to solve the H2 state feedback control

problem

• Using the D-Methodology to implement non-linear

controller.

Vehicle Dynamics

INFANTE vehicle

Vehicle Characteristics

Length(m) 4.5

Width(m) 1.1

Height(m) 0.6

Thrusters 2 (Propellers & Nozzles)

Vehicle Dynamics(cont’)

Coordinate frames: inertial {I}, Body {B}

Serret {T}, Desired Body {C}

Error Space

The vector of control inputs is:

And the output vector is:

Assume straight line, Vr=qc=0,

Error Space(cont’)

Error linearization

Discretization

Preview Problem Formulation

Reference path—slope discontinuityTwo echo sounders are used to

measure the characteristics of the

seabed ahead of the AUV.

The linear error dynamics

The seabed signal

Preview Problem Formulation(cont’)

Discrete Time Controller Design

The Linear Matrix Inequalities

(LMIs)approach is used to

design the discrete time H2

state feedback controller

Theoretical Background

Feedback interconnection

Discrete Time Controller Design(cont’)

Preview Controller Synthesis Technique

Reference PathSensor readings &offset to obtain the data points

•Adding the elevation offset

•Output inertial frame {I} - x coordinate

•Points- straight lines

Final computed path (segments of straight lines)

Implementation Operating regions parameterized byAffine Parameter-Dependent Description of

The plant

Implementation (cont’)Implementation setup using gain scheduling and the D-methodology

D- Methodology

•Integrators (input)

•Differentiator (needed

•Stability Characteristics

•Linearization•Linearization

•Auto trimming Property

Implementation (cont’)Evolution of the preview gains f(t)

Closed-loop system’s H2 norm

Trajectories described by the vehicle

Simulation Results

The control objective is to achieve a constant 15-mbottom elevation offset.

Descending phase Climbing phase.

Error vector Xe (t)

The Papers I’ve presented

The PapersPaper 1 A SURVEY OF UNDERWATER VEHICLE

NAVIGATION: RECENT ADVANCES AND

NEW CHALLENGES

Published

Paper 2 An Adaptive Controller for Underwater Vehicle-Manipulator Systems Including

Thruster DynamicsThruster Dynamics

Published Proceedings of the 2010 International Conference on

Modeling, Identification and Control, Okayama, Japan, July 17-19,2010

Paper 3 A Bottom-Following Preview Controller for

Autonomous Underwater Vehicles

Published IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY, VOL. 17, NO. 2,

MARCH 2009

Any Questions