Autonomous Sailing Boats -

Introduction Hardware Software Architecture Communication Control System Collision Avoidance Simulation and testing

Autonomous Sailing Boats

Christian Alt, Natalie Wittinghofer

Department of Computer Sciences - University of Salzburg

30.5.2011

Christian Alt, Natalie Wittinghofer Autonomous Sailing Boats


Overview

1 Introduction

2 Hardware

3 Software Architecture

4 Communication

5 Control System

6 Collision Avoidance

7 Simulation and testing



Introduction



Challenges of Autonomous Sailing Boats

Hardware challenges

Routeing algorithms

Energy self sufficience

Collision avoidance



Conference and Competitions

International Robotic Sailing Conference (IRSC) since 2008

World Robotic Sailing Championship (WRSC) since 2008

Microtransat 2006 - Routeing Precision

Microtransat 2007 - Short Race (3km), Endurance Race (24h)

Microtransat 2010 - Transatlantic Race (Ireland - Carribean)

Microtransat 2011 - Transatlantic Race



Applications for autonomous sail boats

Intelligend Sensor Buoys

CO2-neutral in Transportation of Goods

Reconnaissance and Surveillance

Supply Vessel

safety and comfort on sailing boats



Hardware



Hardware - Boats

In the World Robot Sailing Championship[1] boats are divided intothree classes:

Microtransat class for boats up to 4 m long

SailBot class for boats up to 2 m long

MicroMagic class (0.53 m long)







Microcontroller and Sensors



A Boat

B PDA

C Rudder Servo

D PDA

E Batteries

F Sail Servo

G Servo Controller

H Sail Servo

I GPS Module



Wind Sensor



Software Architecture



Software Architecture

Has to perform time intensive tasks

Quickly react to changing environment (weather, staticobstacles)

Architectures split the system into different layers

Top-down planner based ModelThree-layer architecture:

Sensing systemPlanning systemExecuting system

Bottom-up reactive system

Mapping from sensorial input to actions



Hybrid architecture by Stelzer [3]

Combines the top-down planner based model and thebottom-up reactive system



Strategic long term routing layer

Represents the general routingstrategy

Based on expected weather, seastate and ocean currents

Determines a optimal roughroute



Short course routing layer

Handles the next targetcoordination

Only local and present windconditions are taken intoaccount



Manoeuvre execution layer

Adjusts the rudder position

Assures that there is a flow inthe sails



Emergency relexes

Passes the setting to theactuators unchanged

In case of an emergency itoverrules the requested actions



Communication



Communication

Permanent data link between boat and shore is necessary

Communications Partners

SailboatVisualisation softwareRemote controller

Three-stage communication system by Stelzer [2]



First Stage: Wireless LAN

Antenna is mounted on theshore and on the mast top

No base or connection fee; Highbandwidth

Infrastructure; limited operationdistance



Second Stage: Data Service of Mobile Phone Provider

Equipped with a data modem

Provide UMTS and GPRS andswitch over automatically

High bandwidth

Base and connection fee can behigh; limited operation distance



Third Stage: Satellite Communication

Iridium satellite transceiver

Covers the whole earth; roughgeographic position information

Low data volume; High latency



Communication strategy

Any of these three stages usedfor communication withvisualisation

Wireless LAN and UMTS/GPRSfor the communication withremote control

Selection of stage is based onthe availability, transfer chargesand bandwidth of the specificchannels



Control System



Control System

Control of a sailboat consists of two main tasks:

governing of the ruddertrimming of the sails

Basic sailing rules about steering the sails and rudderaccording to direction of target and wind

Transformed into a fuzzy inference system

Two independent working control circles [5]:

Rudder controllerSail controller



Rudder Control Circuit

Input variables are:

Current boat direction anddesired directionangular velocity of the boatflow (turn)




Output variable:

Change of the rudder position




Fuzzy Rules :

IF desired direction IS x AND turn IS y THEN delta rudder IS z



Sail Control Circuit

Input variable:

Heeling of the boat anddirection and speed of thewind

Output variable:

Direction and amount ofnecessary adjustment of thesail winch




Fuzzy Rules :

IF heeling is too low THEN tighten sheetsIF heeling is optimal THEN keep sheetsIF heeling is too high THEN ease off the sheets



Collision Avoidance



Reactive Approach to Collision Avoidance (Stelzer et al.[4])

extendsion of the short course routeing layer

modification of the polar diagram









Obstacle Detection



Simulation and testing



Simulation

Real world testing:

expensive

time consuming

potentially dangerous

depending on the weather



Tracksail game modified for testing

Limitations:

too consistent wind

no influence of waves

idealized boat behaviour

no real world noise



Harware testing

testing Electronics

testing simple algorithms



Thank you for your attention

Thank you for your attention



World robot sailing championship, 2011.http://www.wrsc2011.org/.

Roland Stelzer and K. Jafarmadar.Communication architecture for autonomous sailboats.In Proceedings of International Robotic Sailing Conference,pages 31–36, Matosinhos, Portugal, July.

Roland Stelzer and K. Jafarmadar.A layered system architecture to control an autonomoussailboat.In Towards Autonomous Robotic Systems (TAROS 2007),Aberystwyth, UK, September 2007.

Roland Stelzer, Karim Jafarmadar, Hannes Hassler, andRaphael Charwot.A reactive approach to obstacle avoidance in autonomoussailing.


http://www.wrsc2011.org/


In Proceedings of 3rd International Robotic SailingConference, pages 34–40, Kingston, Ontario, Canada, July2010. Queen’s University.

Roland Stelzer, T. Proll, and Robert John.Fuzzy logic control system for autonomous sailboats.In FUZZ-IEEE2007, pages 97–102, London, UK., July.


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Autonomous Sailing Boats -