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Cooperative Autonomous Robotic Towing system

Final Report Summary - CART (Cooperative Autonomous Robotic Towing system)

Executive Summary:
The project CART, that stands for Cooperative Autonomous Robotic Towing system, proposes a new concept for salvage operations of distressed ships at sea.
Coordinated by Serena Ardito, a young woman entrepreneur, the CART project was funded by the FP7 programme Research for the benefit of SMEs in the period from November 1st 2011 to July 31st 2013.
The consortium is constituted by three SME participants:
the project coordinator, Posidonia S.r.l. an Italian SME based in Genova, providing towing and marine equipment;
PKL AS, a tugboat company from Tallinn, Estonia, providing towage and salvage services with its own fleet;
SRS Mecano Instalatie, a small company from Bucarest, Romania, moving from the field of electrical installations to the area of industrial automation;
and three RTD developers
the Institute of Studies on Intelligent Systems for Automation of the Italian National Research Council from Genova,
the Department of Control and Computer Engineering of the University of Zagreb, Croatia,
and Det Norske Veritas from Oslo, Norway, one of the world's leading classification societies.
The CART concept is based on the development of robotised unmanned marine platforms able to (semi-)automatically execute the high risk operation of linking the emergency towing system of distressed ships to towing vessels.
This will minimise the risk for human lives and increase the safeguard of the environment, helping, for instance, to prevent oil pollution at sea, during salvage operations.
The key idea consists in collecting a floating object at sea by executing a knot around it with a floating rope.
In our case, the floating object is a buoy launched by the distressed ship, while the knot is executed by an unmanned robotic vehicle towing the floating rope connected to the tugboat winch.
Two main scenarios have been considered involving harbour and open sea operations.
The first scenario considers the case where a tugboat needs to tow a burning ship, typically a tanker in an oil terminal, out of a harbour.
The CART vessel has to recover a buoy nearby the moored ship.
The second scenario considers the case where a tugboat needs to recover an emergency towing system deployed by a distressed vessel in open sea.
The CART vehicle, that is an intelligent emergency towing system, has to move away from the distressed vessel in order to be recovered by the tugboat in safe conditions.
An extension of this case considers a scenario where a ship in distress is rescued by another ship. In this case, a second CART vessel automatically executes a knot around the intelligent emergency towing system.
To demonstrate the feasibility of the CART concept a set of prototype Unmanned Semi-Submersible Vehicles have been developed.
The development and test of the first prototype focused on the validation of the rope hooking system and on the effectiveness of the knotting maneuver.
It also supported the experimental evaluation of the motor thrust needed to counteract wave effects in operating conditions.
System integration tests were carried out in Murter, Croatia, during Breaking The Surface in October 2012.
Preliminary field validation was performed in Tallinn, Estonia, in November 2012.
At first, tests demonstrated the effectiveness of the hooking system in catching a floating rope.
Then the harbor scenario was considered, where a floating buoy was deployed at sea nearby a moored ship.
The CART vehicle, remotely controlled by a human operator through a radio communication link, was able to recover the floating buoy, thus validating the effectiveness of the hooking system in numerous experiments.
Finally the system capability of recovering a floating buoy in open sea was satisfactorily verified, completing the validation of the CART concept.
In-field deployment and recovery of the vehicle from a tugboat supplied information about the target shape and weight of the robotic platform in order to make it easy to handle in operating conditions.
The last year of the project was devoted to the design, development and test of two new prototype light and manageable Unmanned Semi-Submersible Vehicles.
Moreover, robotics research focused on the design and implementation of suitable cooperative knotting maneuvers.
System integration and maneuvering validation were carried out during a test campaign in Genova Prà harbor, Italy, in May 2013.
The vehicle acting as an intelligent buoy autonomously moved in a straight line, simulating the deployment from the distressed ship.
The recovery vehicle autonomously executed a couple of circles around the intelligent buoy, on the basis of its GPS position received through a radio link.
During the final demonstration in Tallinn, Estonia, in July 2013, the CART cooperative maneuvers were validated in operating conditions in both harbor and open sea.
Harbor trials verified the effectiveness of the new designed vehicles in recovering a floating buoy being remotely operated in protected waters.
Extended tests of the autonomous knotting maneuver involving both the vehicles were carried out, even exchanging the robot roles, in view of the final demonstration.
Open sea trials were supported by two tugboats, one acting as distressed ship and the other as rescue tugboat.
The intelligent buoy, once deployed at sea, moved away from the simulated ship in distress.
Then the recovery vehicle was launched by the salvage tugboat and executed the knotting maneuver.
Once knotted together, the vehicles were recovered onboard the salvage tugboat by pulling the towing line.
The project field activities ended with training of the tugboat crew to remotely pilot the CART vehicle through its control console.
As a result the new CART robotic-based technology for the recovery of emergency towing systems has been qualified and the involved SMEs can plan follow up activities of engineering of a cheaper prototype.
Project Context and Objectives:
The CART project proposes a new concept for salvage operations of distressed ships at sea. In particular, the proposal focuses on the high risk operation of linking the emergency towing system of distressed ships to towing vessels. The proposed concept, based on the development of cooperative robotic technologies able to (semi-)automatically execute the manoeuvre of recovering the towing system, will be able to optimise the operations for safeguarding the environment, typically preventing oil pollution at sea as in the case of the tankers Erika, Haven, Exxon Valdez, while minimising the risk for human life.
Considering the issues related to the pollution induced by distressed ships, according to regulations established by the International Maritime Organization (IMO) and by the international convention for the Safety of Life at Sea (SOLAS), the whole global fleet over 500 Ton gross tonnage has to be mandatory equipped with an emergency towing device and to have set a corresponding emergency procedure. Since bulk carriers cape size or big container ships can have aboard 7.000-8.000 ton of oil as fuel, thus constituting a danger for environmental pollution comparable to a tanker, the application of these rules will be extended to all passenger and cargo ships not later than 1st January 2012.
This context, together the increasing worldwide awareness of the very high and, often, difficultly predictable costs related to marine pollution induced by oil spills, opens significant opportunities to the market of emergency towing systems (ETS), giving space for the development of any innovative technology provided that it is qualified, i.e. the limits within which it functions reliably are defined with a systematic approach. This aspect, strictly related to the assessment of insurance rates, is fundamental in the maritime field.
Existing technologies for linking a towing device of a distressed vessel to a tugboat usually involve quite complex operations and high risks for human life with corresponding high values of insurance costs. Conventional systems, such as line-throwing gun, pick-up buoy or tugboat-towed messenger stream, are based on a messenger (bullet or pick-up buoy) connected to a live-line, linked, in its turn, through a towing chain or rope to the distressed ship. This requires the towing vessel to approach the distressed ship at relatively short range, which can be very dangerous in the case of rough sea conditions. Moreover, when a vessel is grounded, it is often impossible to go close with a tugboat, because of shallow water or rocks, according to the kind of coast. Since it is not possible to know what kind of cliffs are underwater, sending a work-boat with people to deliver a messenger rope to a grounded vessel is very dangerous.
These problems can be solved by using cooperative (autonomous) robotic towing systems for the recovery of the live-line. Indeed, the introduction of the new CART concept, involving the use of an autonomous robotic semi-submersible vehicle for the recovery of the live-line eventually combined with or in alternative to a robotised pick-up buoy, able to hover at a safe range from the distressed vessel, will dramatically increase the safety of operations, opening the market to new robotic-based tools for linking the towing line.
Thus, the CART concept is based on the idea of using beyond state-of-the-art cooperative robotics technology in the field of unmanned marine vehicles to improve the safety and feasibility of salvage operations by increasing the distance between the towing tugboat, or salvage vessel, and distressed ship. This can be done by combining the use of i) a pick- up buoy named B-ART, robotized and able to manoeuvre in order to keep a safe position during the operations, deployed at sea from the distressed ship with a human operator aboard the tugboat, or with ii) an unmanned semi-submersible vehicle (USSV), named ART, remotely controlled or supervised (according to its degree of autonomy), performing the recovery task, in the case of cooperative robotic operations.
The main objective of the project is the validation of a new robotics-based concept of intervention for the linking of the emergency towing system of distressed ships to tugboats and salvage vessels of any type. Having in mind the subsequent development of an engineered CART- derived product for the market, validation means to evaluate performance, fitting for purpose and possible market price of different technological solutions with different costs and assembly complexity in order to support SME participants in focusing their follow-up exploitation of project results.
The main objectives of the project are:
1) to validate the CART concept and demonstrate its fitness for purpose;
2) to perform application-driven beyond state-of-the-art research in the field of cooperative marine robotic systems and guidance and control of small vessels in rough sea;
3) to transfer technology and know-how to the SME participant
Three operating scenarios have been considered.

The first case study considers a conventional operating scenario where a tugboat needs to tow a
barge, ship or any other “towing object” to a new destination.
During these operations a tugboat, equipped with a small crew (usually 5-6 people), is connected
with a cable to the towing object, where no crew is aboard. Tugboats performing sea towages are
usually required to have a long steel wire as a main towing line. Usually tugs have 500 – 900 m
steel wire, as long and heavy wire form U-shape curve between a tug and a towing object,
absorbing shocks by stretching it underwater due to own weight and water resistance. In order to
operate such a long and heavy steel wire, a tug should have towing winch installed of its aft deck.
The other end of main towing line is connected to a towing objec
Unfortunately, mass of tug and a towing object often exceeds maximum breaking load of a towline.
In a bad weather conditions with high waves, a towline may get big shocks from two floating
objects moving in different directions on high waves connected with steel wire under tension.
Therefore any towline can be broken at a certain level. Increasing strength of a steel towline will
increase tension on the towing gear components or on a connection point onboard a towing object,
which will also result in connection loosing.
A good practice and often a hirer requires installation of emergency wire on a towing object, which
is a polypropylene wire attached with cords to a side of a towing object (or packed onboard of a
towing object) with one end freely floating in water and connected with a messenger rope to a pick-
up buoy (also in water). In case the main towing line is broken, tug has to come close to a towing
object, find the pick-up buoy, get it out of the water, get the emergency towing line onboard and
fasten it to a tug. Emergency towline has lower breaking load and shock absorbing capabilities,
however it may help keeping the towing object in safe position preventing from drifting (which may
result in grounding or another accident) or possibly to even continue towage.
Referring to the above mentioned procedures, in the case of breaking of the towing line, the main
problem is recovering the floating buoy often in harsh operational conditions.
A possible solution to the problem could be to develop an active buoy B-ART, suitably mounted aboard the towing object, able to move away
from the towing object itself.

The second case study considers a conventional operating scenario where a tugboat needs to tow a
burning ship, typically a tanker in an oil terminal, out of a harbor.
State-of-the-art procedures foresee the deployment of a rope at sea by tankers during harbor
In the case of fire
aboard, or any other accident requiring the emergency towing of the vessel outside the harbor for
safety reasons, the tugboat has to recover that rope to connect the emergency towing line. Although
the execution of this task could be supported by the use of firefighting equipment aboard the
tugboat, in any case it requires the approach of the firing area with high danger for
the human beings involved in the operations.
A possible solution to this problem could be to develop a vehicle ART able to recover a generic buoy that is already at sea, as in state-of-
the-art procedures.

The third case study considers a scenario in which a ship in distress is rescued by another ship.
Examples are provided by naval vessels, where for protecting classified information the
intervention of third-parties should be avoided, and by situations in which, in presence of risk of
imminent environmental contamination, e.g. oil spills, tugboats are only available at some days of
navigation while other ships are in the area.
In these very specific situations ship-to-ship towing, where both the vessels are assumed to have
crew aboard, can be considered nevertheless the main challenge of recovering the towing line.
A combined operation of the above mentioned B-ART and ART vehicles coyuld be a solution for this problem.
Project Results:
The CART project achieved a large spectrum of S&T results, generating the corresponding foreground, according to different perspectives from the field demonstration of the concept of developing robotised unmanned marine vehicles able
to (semi-)automatically execute the high risk operation of linking the emergency towing system of
distressed ships to towing vessels
to the consolidation of hardware and software platforms for robotics and industrial applications.
A short list of the project main S&T results is given below, while detailed discussion of each of them will be reported in the next sub-sections.
CART Main S &T results/foreground
demonstration of the effectiveness of unmanned semi-submersible vehicles, equipped with a simple hooking system, for collecting emergency towing devices at sea by executing a suitable knotting manoeuvre
robotics research
design and implementation of cooperative guidance algorithms for the autonomous execution of a knotting manoeuvre
prototype robots
CART 1: first prototype vehicle for preliminary concept and technology evaluation
CART 2: couple of vehicles for concept and technology demonstration
concept robots
B-ART: intelligent autonomous buoy/vehicle
ART: remotely operated semi-submersible robot for recovery of emergency towing devices
CART: cooperative autonomous combination of ART and B-ART vehicles
procedures for CART-like technology operations
hw & sw platforms
effectiveness and reliability of GNU/Linux and PC-compatible platforms
effectiveness and reliability of PIC and MEMS based architectures

CART concept demonstration
The CART project relied on the idea that it is possible to recover a floating object connected to a floating rope at sea by executing around it a kind of knot with another floating rope towed by an unmanned vessel.
This concept was experimentally validated during the project in numerous operating conditions from harbour to open sea using three heterogeneous prototype unmanned semi-submersible vehicles, developed in the project, equipped with different hooking systems on the top.
At first, the capability of the vehicle to catch its own towed rope was demonstrated. Then, tests revealed the capability of hooking a rope link to a floating object or towed by another vehicle.

CART cooperative guidance algorithms (robotics research results)
Cooperative guidance algorithms have been designed and implemented to allow a couple of unmanned semi-submersible vehicles to autonomously execute a knotting manoeuvre. In particular, the case of a first vehicle acting as an intelligent buoy, B-ART, i.e. moving straight on away from the distressed ship and of a second vehicle, acting as an autonomous ART, i.e. executing a couple of circles around the first vehicle has been considered. It is worth noting that the execution of two circles around the first vehicle guaranteed the completion of the knot and the hooking of the floating rope with sufficient redundancy.
Assuming the position of B-ART known, since it is transmitted by a radio link to ART, the proposed cooperative guidance algorithm is an extension of well-know virtual target based path-following techniques for unmanned marine vehicles. In this case, the path to be followed in a circle centered in the B-ART position, i.e. shifting with the target robot.
After theoretical demonstration, the cooperative guidance algorithm has been validated in simulation and at field with extended experiments in different operating conditions and using different prototype vehicles developed in the project.

Prototype robots
CART 1 is the prototype unmanned semi-submersible vehicle developed during the first year of the project for preliminary concept and technology evaluation. Equipped with four motors, powered by a set of Li-ion batteries, and controlled by a PC-compatible and GNU/Linux based hardware and software platform, it demonstrated the effectiveness of the CART concept as well as of radio communications for a semi-submersible vehicle in harsh sea conditions.
After preliminary tests in Murter, Croatia, in October 2012, devoted to finalise the integration of the vehicle sub-systems and verifying its functionality, CART 1 USSV was extensively tested in both harbour and open sea scenarios in Tallinn, Estonia, in November 2012. The vehicle trials provided precise indications, in particular regarding shape and weight for improving manageability, for the design of the final CART prototype USSVs during the second year of the project.
A couple of CART 2 vehicles, weighing less than 30 Kg and with a rounded shape facilitating their recovery at sea, have been designed and developed during the last nine months of the project. Each of them was equipped with a couple of motors, and powered by a set of Li-ion batteries. The feasibility of micro-controller and MEMS sensor based technology was verified, constituing the navigation and control system of one of the two prototype robots.
System integration, from the point of view of cooperative manoeuvring, was performed in the Genova Prà harbour, Italy, in May 2013, while the project final demonstration took place in Tllinn, Estonia, in July 2013. Extensive trials demonstrated the capability of both the prototype vehicles to act as intelligent buoy, remotely controlled catching vessel and cooperative autonomous vessels.

Concept robots
The developed prototype vehicles demonstrated that the CART project developed the basic technology supporting the engineering of the conceptual robots required by the different considered operational scenarios, namely B-ART, ART and CART.
B-ART (Buoy - Autonomous Robotic Towing system) is an unmanned semi-submersible vehicle acting as an intelligent buoy able to autonomously move away from the distressed ship, or abandoned towed object, once deployed at sea. The vehicle communicates its position to a Remote Control Station through a radio link. The vehicle will be engineered in the project follow-up on the basis of the developed prototype robots. A system for automatic deployment of B-ART from the distressed vessel will be designed and developed in the CART follow-up according to basic ideas discussed in the project.
ART (Autonomous Robotic Towing system) is a remotely operated semi-submersible robot for the recovery of emergency towing devices, such as a buoy connected to a floating messenger line. The vehicle communicates with the Remote Control Station through a radio link. ART will be engineered in the project follow-up on the basis of the developed prototype robots.
CART (Cooperative Autonomous Robotic Towing system) is the combination of B-ART and ART vehicles, suitably equipped with cooperative guidance system for the autonomous execution of the knotting manoeuvre and integrated with a Remote Control Station able to supervise cooperative operations.

Procedures for CART-like technology operations
Procedures for the operations of CART-like technology have been established and the personnel of the tugboat company has been trained in piloting and operating the prototype vehicles.

Hardware and software platforms
GNU/Linux and PC-compatible hardware platforms proved their effectiveness and reliability in supporting robotic systems. Know-how has been transferred to SMEs for further applications in the field of industrial automation.

Micro-controllers and MEMS-based sensors proved their effectiveness in the development of low cost unmanned marine vehicles. Know-how has been transferred to SMEs for further applications in the project follow-up engineering activities.
Potential Impact:
The primary goal of the CART project is to develop a new safety-oriented concept and technology for salvage operations of distressed vessels at sea. This also contributes to the reduction of the dramatic environmental and socio-economic impact of oil spills (and more generally chemical pollutant spills) by enabling faster identification of possible leakage and effects they can have on environment. Namely, during the salvage operation, that is almost always the first operation that takes place close to the distressed ship, the system could measure oil (or chemical) content in the area around the ship, giving the first reliable data necessary for the estimation of possible environmental impact. Early detection is crucial in such situations because preparation of counter-measures can be significantly improved and the operation of diminishing the effects of oil (or chemical) spills on environment can start earlier. The environmental and socio-economic damages caused by oil spills in coastal areas, involving immediate and long-term effects on fragile marine ecosystems, fishing, tourism and recreation, are often quite high.
The CART project carrying out cutting-edge research, developing innovative technology, contributing to increase the eco-compatibility of sea transportation, and training young researchers and employed people, moved along the guidelines provided by “Europe 2020, a European strategy for smart, sustainable and inclusive growth”.
Indeed, CART, while developing a new technology for the emergency towing of distressed vessels, based on cooperative marine robotics, strengthened the innovation chain from cutting-edge research to technology qualification, providing the SMEs with all the instruments for engineering, manufacturing and marketing new products originated by the concept validated in the project itself. With the significant contributions provided by public research institutions and universities CART contributes to increase the impact of public research and its links with industry, strengthening the leverage effects of public support on investment by private actors.
In particular, in relation to the flagship initiatives promoted by the European Union in Europe 2020, CART contributes to:
“Innovation Union”, turning innovative ideas towards new products and services, that can open new markets creating growth and job opportunities;
"Youth on the move", facilitating the entry of young people to the labour market employing young researchers in the RTD activities in view of their involvement in the follow-up system engineering, manufacturing and commercialisation; increasing the sensitiveness and awareness of young generations with respect to research and innovation as well as environmental safeguard through the participation to targeted scientific events such as Breaking The Surface;
"Resource efficient Europe", contributing to modernise the safety equipment of the sea transport sector;
"An industrial policy for the globalisation era", supporting the development of SMEs, through the increase of their innovation capabilities, and networking with companies and academic and research institutions;
"An agenda for new skills and jobs", training employed people in order to develop their skills throughout their professional life cycle, improving, in the meantime, SMEs capability of entering new market niches and adapting to new global conditions. Contributing to reducing unemployment, these aspects will play a role in the fight against poverty too.
Moreover, with the coordination of a young woman entrepreneur and the involvement in the project of other women, CART contributed to mitigate the differences in gender participation and career opportunities still present in the maritime field.
Due to its modular design, the CART system can be released, after a follow-up engineering phase, in three separate commercial products, giving the opportunity to the participant SMEs of successfully playing in different market scenarios regarding emergency towing devices. Indeed, the B-ART intelligent robotic buoy can be seen as a high-tech upgrade of the emergency towing devices of the class currently commercialised by Posidonia srl. Automatically moving away and keeping a safe distance from the distressed vessel, the B-ART intelligent pick-up buoy facilitates the recovery of the live-line by a tugboat. On the other hand, the ART USSV, able to recover a traditional pick-up buoy, is a tool dedicated to towing and salvage companies in order to facilitate operations and reducing risks when operating with distressed ships, also in harbour operations, thus offering a technological and operational advantage with respect to companies working with traditional methods. The above mentioned benefits, in terms of both safety of operations and easiness in recovery of the pick-up buoy, are combined when the distressed ship and the tugboat are equipped with B-ART and ART sub-systems respectively. Indeed, thanks to the transportability, as well as the possibility of deployment aboard a distressed vessel by helicopter of the B-ART device, the overall CART system can be offered to towing companies as an integrated, easy transportable tool, for the salvage of distressed ships, able to give a significant technological advantage to its owners.
Moreover, in the area of industrial automation, the acquired know-how, thanks to the CART project, about GNU/Linux-based embedded real-time platforms will offer to the start-up SME SRS Mecano Instalatie the opportunity of entering new in-expansion market niches enlarging and diversifying its customer portfolio.
Among the conventional dissemination activities carried out in the project, it is worth noticing the participation to SMM (Shipbuilding, Machinery & Marine technology international trade fair) in Hamburg, Germany, in 2012, to the 9th IFAC Conference in Manoeuvring and Control of Marine Craft in Arenzano, Italy, in 2012, and to the field workshop Breaking The Surface in Murter, Croatia, in 2012 and 2013 (in this case after the conclusion of the project), where the CART system has been presented to maritime stakeholders, marine robotics and ship automation researchers, marine scientist, archaeologists and security personnel respectively.
List of Websites:
CART project public website:

Contact – Project Coordinator
Mrs. Serena Bianca Ardito
Posidonia Srl
Posidonia Srl

Head office and warehouse
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Phone +39 0143 76669 - Fax +39 0143 143 2230
Fiscal address and testing house
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