Recent Publications

Stelzer, R.; Jafarmadar K. (2012): "The Robotic Sailing Boat ASV Roboat as a Maritime Research Platform" in Proceedings of 22nd International HISWA Symposium on Yacht Design and Yacht Construction, Amsterdam, The Netherlands.

Robotic sailing boats represent a rapidly emerging technology for various tasks on lakes and oceans. They offer the possibility of sampling an area of interest with high temporal and spatial resolution at low cost. This paper gives an overview about the main building blocks and maritime research missions of the ASV Roboat. The boat won several international competitions in robotic sailing in recent years and is therefore at the forefront of international excellence. The ASV Roboat has just returned from a several-day research mission in the Baltic Sea. By using a hydrophone attached to the boat’s keel, the acoustic signals of a number of whales were recorded during the survey, and valuable information was collected on the presence of these animals in the study area. To the authors’ knowledge this is the first time that an autonomous sailing boat has been successfully deployed as part of a scientific research project.

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ASV Roboat detected harbour porpoises in the Baltic Sea

Stelzer, R.; Estarriola Dalmau, D. (2012): "A Study on Potential Energy Savings by the User of a Balanced Rig on a Robotic Sailing Boat", in Proceedings of International Robotic Sailing Conference, pp. 87-94, Cardiff, Wales, UK.

The drive for the sail trim has been identified as one of the largest consumers on the autonomous sailing boat ASV Roboat. The presented work analyses the potential energy savings of a balanced rig compared to the conventional sloop rig, which is currently in use on this boat. Results of a computer simulation show that a balanced rig can save about two-thirds of the power needed for the sail trim.

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Compared rigs: sloop vs. balanced

Stelzer, R. (2012): "Autonomous Sailboat Navigation – Novel Algorithms and Experimental Demonstration", PhD Thesis, Centre for Computational Intelligence, De Montfort University, UK.

The purpose of this study was to investigate novel methods on an unmanned sailing boat, which enables it to sail fully autonomously, navigate safely, and perform long-term missions.

The author used robotic sailing boat prototypes for field experiments as his main research method. Two robotic sailing boats have been developed especially for this purpose. A compact software model of a sailing boat’s behaviour allowed for further evaluation of routing and obstacle avoidance methods in a computer simulation. The results of real-world experiments and computer simulations are validated against each other.

It has been demonstrated that autonomous boat sailing is possible by the effective combination of appropriate new and novel techniques that will allow autonomous sailing boats to create appropriate routes, to react properly on obstacles and to carry out sailing manoeuvres by controlling rudder and sails. Novel methods for weather routing, collision avoidance, and autonomous manoeuvre execution have been proposed and successfully demonstrated. The combination of these techniques in a layered hybrid subsumption architecture make robotic sailing boats a promising tool for many applications, especially in ocean observation.

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ASV Roboat on research mission

Stelzer, R.; Jafarmadar, K. (2011): "History and Recent Developments in Robotic Sailing", in Proceedings of International Robotic Sailing Conference, pp. 3-23, Lübeck, Germany.

Robotic sailing boats represent a rapidly emerging technology for various tasks on lakes and oceans. In this paper we give an overview about the main building blocks of a robotic sailing boat for controlling the rudder and the sails. History of robotic sailing includes developments in mechanical, electronic, and intelligent self-steering systems as well as automatic sail control. Furthermore advantages and disadvantages of rigid wing sails in comparison to traditional fabric sails are illuminated. Early examples of robotic sailing boats and recent developments, stimulated by robotic sailing competitions such as Microtransat Challenge, SailBot and World Robotic Sailing Championships are presented. We conclude with a brief outlook on potential applications in the field of robotic sailing.

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Early robotic sailing boats

Dabrowski, A.; Busch, S.; Stelzer, R. (2011): "A Digital Interface for Imagery and Control of a Navico/Lowrance Broadband Radar", in Proceedings of International Robotic Sailing Conference, pp. 169-181, Lübeck, Germany.

The paper describes a method to establish compatibility between an autonomous surface vessel control system and a Navico Broadband Radar BR24. The solution obtains radar imagery and control of the antenna unit over its standard Ethernet interface, making the proprietary controller unit optional. It presents devices, software and methods used for empirical protocol analysis and documents the findings. Protocol details for the following functions have been identified: Operation, zoom level, various filter settings, scan speed and keep alive. An open source implementation with basic operational functionality has been made available. It features a live network mode and a replay mode using captured network traffic. In live mode, controlling radar operation as well as zoom level is possible. In both modes the radar imagery stream is rendered and displayed.

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Radar data/photo comparison with canoeist

Langbein, J.; Stelzer, R.; Frühwirth, T. (2011): "A Rule-Based Approach to Long-Term Routing for Autonomous Sailboats", in Proceedings of International Robotic Sailing Conference, pp. 195-204, Lübeck, Germany.

We present an algorithm for long-term routing of autonomous sailboats with an application to the ASV Roboat. It is based on the A*-algorithm and incorporates changing weather conditions by dynamically adapting the underlying routing graph. We implemented our algorithm in the declarative rule-based programing language Constraint Handling Rules (CHR) [4]. A comparison with existing commercial applications yields considerably shorter computation times for our implementation. It works with real-life wind forecasts, takes individual parameters of the sailboat into account, and provides a graphical user interface.

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The GUI showing wind conditions and the calculated route

Stelzer, R.; Jafarmadar, K.; Hassler, H.; Charwot, R. (2010): "A Reactive Approach to Obstacle Avoidance in Autonomous Sailing", in Proceedings of International Robotic Sailing Conference, pp. 34-40, Kingston, Ontario, Canada.

This paper presents a reactive approach to obstacle avoidance for autonomous sailboats. It is an extension to the short course routing method published by Stelzer and Pröll in 2008 which enables it to deal with obstacles in real-time. First simulation results are promising. The algorithm enables an autonomous sailboat to circumnavigate differently sized obstacles under various wind conditions successfully.

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Influence of obstacles on polar diagram

Klinck, H.; Stelzer, R.; Jafarmadar, K.; Mellinger, D.K. (2009): "AAS Endurance: An autonomous acoustic sailboat for marine mammal research", in Proceedings of International Robotic Sailing Conference, pp. 43-48, Matosinhos, Portugal.

This paper presents a joint research project of the Austrian Society for Innovative Computer Science, Austria and Oregon State University, USA which is intended to be realised within the next three years. The aim of the project is to develop an autonomous sailboat for passive acoustic monitoring of marine mammals and mitigation of human impacts on them. Performance tests of the autonomous acoustic sailboat - AAS Endurance - will include an open sea transect of at least one month duration. The work presented here discusses shortcomings of current ways of acoustic marine mammal monitoring and outlines advantages of a robotic sailboat for this task, as well as problems to be solved with this new technology.

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Comparison of the spatial and temporal coverage of ship transects (dotted line) and stationary recorders (dashed circles)

Stelzer, R.; Jafarmadar, K. (2009): "Communication Architecture for Autonomous Sailboats", in Proceedings of International Robotic Sailing Conference, pp. 31-36, Matosinhos, Portugal.

Although an autonomous sailboat can operate without human intervention a data link between boat and shore is necessary. During development a reliable connection for monitoring, debugging, and remote control in case of emergency is essential. When used for long-term observation tasks the operator on shore is keen to receive real-time measurement data. A three-stage communication system for autonomous sailboats has been designed, implemented and tested successfully. It combines wireless LAN, GPRS/UMTS and satellite communication for a reliable data link between shore and sailboat.

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Third stage - satellite communication

Stelzer, R.; Pröll, T. (2008): "Autonomous Sailboat Navigation for Short Course Racing", in Elsevier Journal of Robotics and Autonomous Systems, Vol. 56 (7), pp. 604-614.

The paper presents a compact method to calculate a suitable route for a sailboat in order to reach a specified target. The calculation is based on the optimisation of the time-derivative of the distance between boat and target and features a hysteresis condition, which is of particular importance for beating to windward. The algorithm provides an answer to the perennial question when to tack on upwind courses. Further, it immediately adapts to varying wind conditions. The resulting routes for different conditions are analysed on the basis of a simulation featuring a mathematical boat model. Experiments have been carried out using an unmanned and autonomously controlled sail boat. The navigated route agrees well with the simulation results.

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Routeing Example (compares real test run with simulation results)

Stelzer, R.; Pröll, T.; John, R.I. (2007): "Fuzzy Logic Control System for Autonomous Sailboats", in Proceedings of IEEE International Conference on Fuzzy Systems, pp. 97-102, London, UK.

Sailing experts can explain basic sailing skills by rules about how to steer sails and rudder according to direction of target and wind. This paper describes how to transform the sailor’s knowledge into Mamdani type fuzzy inference systems. The proposed system controls two actuators – rudder and sails – even during tack and jibe. In combination with an automatic weather routeing system the sailboat is able to reach any target completely autonomously. Experiments on a demonstration sailboat have shown excellent results. Detailed log data analysis shows manoeuvres carried out as expected by sailing experts.

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Tack Example
Jibe Example

Stelzer, R.; Jafarmadar, K. (2007): "A Layered System Architecture to Control an Autonomous Sailboat", in Proceedings of TAROS 2007, Aberystwyth, UK.

A four layered control architecture is presented for an autonomous sailboat combining both reactive and planner-based approaches. The system allows autonomous sailing, where routeing, navigation and carrying out the manoeuvres run automatically and directly on the boat. Various sensors observe the highly dynamic environment and provide measured data to the control system, which steers rudder and sails. The four layers are responsible for strategic long term routeing, short course routeing, manoeuvre execution, and reflexes in case of emergency. All four layers are executed in parallel. They access sensor data directly and generate prerequisites for the succeeding, subordinate layer. Experiments using a yacht model have been carried out to demonstrate feasibility and suitability of the presented approach. Detailed log data analysis from actual sailing trips show a steering behaviour as expected by sailing experts.

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Roboat System Architecture

Stelzer, R.; Jafarmadar, K. (2007): "Simple Communication Protocol for Rapid Robot Prototyping", in Proceedings of Humanoid and Service Robotics Conference", Kosice, SK.

Aim of the method presented in this paper is to provide a simple and unique communication protocol for a wide variety of sensors and actuators. All of the devices are equipped with a microcontroller in order to translate the proprietary device dependent protocol into the protocol presented here, named Simple Sensor Network (SSN). Due to the very simple commands to request data from a sensor respectively to send data to an actuator via RS232, it is an appropriate way for a novice to get in touch with robotics without the need of expert knowledge in electronics or programming. SSN makes a system easy to maintain, to adapt, and to extend.

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SSN Based Sensor and Actuator Network of the Roboat

Patent

Patent "Verfahren zur Navigation und Manövrierung eines vom Wind getriebenen Wasserfahrzeugs" ("System to navigate and to manoeuvre a wind propelled water vehicle")