Workplan
Task 1: Development and integration of the motions and hauling force monitoring system
This task will start by identifying motion and force measuring sensors which are already installed onboard and those which have to be installed specifically for the system and combining them in an integrated system whenever appropriate. In order to avoid large disruptions of onboard systems, those sensors that are installed by the researchers and the data acquisition will be based in previous experience gained during full-scale tests carried out onboard patrol boats and navy corvettes by Guedes Soares et al. (2002). Other onboard sensors may be used for determining the ship's drafts and the tank content and in this way characterize the ship's loading condition. Regarding the hauling force and depending on the winch system, electronic pressure sensors or electric current meters may have to be installed to allow force estimates. The set of sensors for motion and hauling force monitoring described above will be assembled and combined into a coherent system and its correct functioning tested in laboratory. A field test on board a fishing vessel is also envisaged and will be carried out in Task 5.
Task 2: Development of the software for data acquisition and processing
This task comprises the development of software which allows the acquisition of the signals from the sensors chosen in Task 1 and analyses them to obtain the vessel's loading condition, the seaway characteristics and the hauling force. Data acquisition will be based on National Instruments equipment and Labview software, technology previously employed in full scale tests regarding motions and maneuvering of fast patrols boats and navy corvettes, see Guedes Soares et al. (2002). Purpose developed code will take hydraulic pressure or electric motor current, depending on the winch system, and estimate the cable tension. This estimate, together with cable angle and haul point will be used to determine the force and moment exerted on the vessel. The cable payout will be used to determine possibility of additional payout, to improve estimates of fishing gear location, to determine if payout rates have reached limits. Signals for the vessel motions and cable forces will be acquired and processed using specially developed software in order to produce the necessary data for use in the decision support system. Since sensors have different characteristics with respect to signal outputs, the software will deal with digital and analogue data acquisition. The software may also receive signal from the draft and tank content sensors, allowing a complete characterization of the vessel's loading condition.
Task 3: Development of the decision support software for intact stability assessment
This task will use the data received from the sensors to calculate the loading condition of the ship in each time, considering also the towing or hauling force, exercised by the fishing gear, if existing. Information regarding the drafts and the tank soundings may also be received from the software developed in Task 2. The data provided by the sensors will be used to calculate the stability of the vessel in each moment and compare it with applicable stability criteria, including the effects of water on deck and hauling the net. The safety margins can then be evaluated and displayed on the screen, showing the safety level in a user-friendly way and indicating a number of measures to be taken in case the safety limits are near or even consistently exceeded. These measures may include, for example, alleviating the tension in the hauling cables, moving weights on-board the ship (changing the location of the net and of the fish from and to the deck) or taking ballast water. For these tasks, software will be further developed which calculates the stability of the ship using the pressure integration technique as presented by Santos and Guedes Soares (2001). This software will be further developed in order to be able to take into account the effects of the loading condition of the different tanks, the presence of water on deck and the magnitude of the heeling moment due to the hauling of the net. Another software module will be developed to evaluate the ship's stability against the statutory regulations, namely the established IMO criteria. The software will also incorporate a module for evaluating the effects of different operational measures to improve the vessel's stability and inform the ship's master of the best possible option taking into account various aspects related to stability, hull girder loading and seakeeping. The software will also be able to actuate a sound alarm to alert the master in case of dangerous situations and warn against overloading after a fishing trip (excessive cargo) or when leaving the harbor, indicating in this last case that the vessel has suffered changes or is carrying a too heavy fishing gear. These are well-known and relatively common ad-hoc changes to the vessel's design and operation which often lead to stability problems. It is important that the software is user-friendly, displaying the output in the screen in a graphical way, using color codes to show clearly the vessel's situation regarding stability, the safety margins and the most appropriate measures to be taken. For this purpose, the previous experience gained when developing the graphical interface for a virtual reality application which simulates ship flooding by Varela, Santos and Guedes Soares (2003) will be used.
Task 4: Development of the decision support software for evaluation of dangerous situations in heavy seas
This task will further develop existing hydrodynamic software dedicated to the analysis of such problems as synchronous rolling motion, parametric rolling motion and reduction of stability on the wave crest. These situations occur in different wave characteristics and directions under certain limits of known parameters. In this respect, the experience gained in the calculation of large amplitude rolling motion by Santos and Guedes Soares (1997) and parametrically excited roll motion by Ribeiro e Silva and Guedes Soares (2005) will be applied. The hydrodynamic software presented in these works will be further developed to take into account the effects of the fishing gear and water on deck and tailored for the purpose of being able to provide guidance to the master. This software will then be used to determine minimum allowable parameters of the vessel's stability for avoiding capsize and these limits will be compared to the minimum requirements arising from the intact stability criteria. This will allow the identification of situations where the regulatory requirements, which aim only at providing minimum levels of safety, are not satisfactory. This valuable information can then be used in the decision support system to provide better supported guidance to the vessel's master. It is anticipated that most of this analysis work will be carried out in land using the specially developed hydrodynamic software, for the vessel selected for implementation of the system. The results of the analysis will then be incorporated in the decision support system. The software will need input from the software for data acquisition developed in Task 2 regarding the ship's heading and the wave's period, predominant heading and height. It will also require data on the loading and stability condition of the vessel. The software will plot the situation of the vessel in a polar diagram and evaluate if it is currently in the dangerous zones. In this case, it will advise the master on possible changes of heading, speed, stability characteristics, in order to avoid the dangerous situations, taking in consideration the recommendations of IMO-MSC (2005a) and the results of the hydrodynamic analysis performed with the simulation software. Changes on the stability of the vessel will also have to be coordinated with the stability decision support in order not to endanger the stability of the vessel when attempting to avoid synchronous or parametrically excited roll motion. It is important that this software shows the ship's situation regarding avoiding dangerous seas in a clear way, for which purpose a suitable interface module will be developed. The appropriate measures to be taken by the master should also be clearly stated. In this respect, as in the previous task, the experience gained when developing the graphical interface for a virtual reality application which simulates ship flooding by Varela, Santos and Guedes Soares (2003) will also be used.
Task 5: Implementation and testing of the system onboard a fishing vessel
This task will first include extensive testing of the data acquisition and decision support software developed in Tasks 2, 3 and 4 using simulated sensor data to test all possible situations for the vessel, without compromising the safety of an existing fishing vessel in extreme conditions. These comprehensive tests might then include situations capable of endangering the vessel, allowing for the evaluation of the measures advised to the master by the system in various conditions. After the previous tests are completed successfully, the complete system will then be implemented on-board a fishing vessel and tested by mean of sea-trials, using the experienced reported, for example, in Guedes Soares et al. (2004), with naval vessels seakeeping full-scale trials. For this purpose, the sensors for motions and forces will be installed on-board or connected, if already existing, to the computer where the sensor data integration software is installed. A complete set of tests can then be carried out to check if the sensor data is correct and being correctly acquired and processed by the data acquisition software. Tests will then be carried out for different loading conditions (departure from port, arriving at fishing ground, departure from fishing ground, arrival at port, for example), different seaway conditions and different operating conditions regarding the fishing process. The functioning of the software modules for stability decision support and avoidance of dangerous seas will be recorded and its response to various situations also recorded. The testing of the software behavior in these real conditions cannot, evidently, endanger the fishing vessel on-board of which the tests will be carried out.
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