Exploitable results
Modern ship types are developing rapidly. Consequently, the experience gained by a crew on a certain ship does not necessarily apply to another vessel, even to vessels of the same ship type.
Situations have been reported where vessels have entered dangerous situations without any warning. With today's modern ship types, the captain and his crew can be faced with 'new' phenomena like parametric excitation and pure loss of stability. Generally, guidance on how to identify such problems and resonance is not available or appropriate, mainly due to the highly non-linear roll motion and lack of development (i.e. the means to use the theoretical knowledge for practical application). Also phenomena like slamming and excessive vertical accelerations at the bow are not simple to detect on large modern ships.
Recent data proves that commercial losses and loss of life can potentially be reduced by introducing this kind of decision support system. Losses pertinent to the motion of ships in heavy seas recorded from April 2005 until March 2006 are 43 lives and an estimated EUR 100 million.
ADOPT has provided a process of DSS creation with the three major process elements:
mode 3 - design;
mode 2 - training;
mode 1 - operation.
Decision support for mode 1 starts in mode 3. Mode 2 is required to convey the information generated in mode 3 to mode 1. Operation of a ship in mode 1 will be improved by mode 2 even without a specific computerised mode 1 DSS. A computerised mode 1 DSS will further improve the operation in mode 1 by given real time support that might capture scenarios beyond the experience or capabilities of the crew.
It has been reflected in Mode 3 - Design that DSS shall be modular, risk-based, ship-specific, reliable, shall take into account the relevant uncertainties from all sources, shall provide quality control regarding the reliability of the displayed information, shall display information of limitations in the displayed content, shall be able to perform a self-assessment and shall resolve internal contradictions and provide consistent decisions support.
The general approach in the Mode 2 - Training is not only the familiarisation with the system itself but also to give advise on the background of phenomena (like parametric rolling), as the purpose of the DSS only can be captured when the theoretical foundation is available. By this approach, the training does not only customise the user on the system but also contributes to an improved situational awareness of the risks in specific sea states.
The training concept consists of two modules with two sessions each, starting with general ship theory. Since the ADOPT-DSS is ship specific, the theory will afterwards be consolidated by exercises in the simulator demonstrating the vulnerability of the specific ship in particular seas. In the next session, the crew will be familiarised with using the DSS. This again starts with the theoretical description how the DSS works, which are its limitations, which are its modules, and in which situations it can help. Afterwards, in the final module, the user will be customised in a simulator environment to get experience in using the system and improve his behaviour in critical situations.
Mode 1 - Operation has satisfied the following requirements for DSS: to be modular; to support real-time decision making; supported by a DSS, the master shall improve his decision making under uncertainty; decision support shall have a time range of about one watch; to operate on a ship while sailing; to be operated and used by a ship's crew; to take into account extreme environmental conditions; to take into account multiple wave systems; to avoid misinterpretation of displayed information; to avoid display of wrong information; to be robust; to display information of limitations in the displayed content; to warn the user if risks arising from the identified hazards are beyond negligible; be able to perform a self-assessment; to be ship-specific; to resolve internal contradictions and provide consistent decisions support.
Technical implications of results
A risk-based, ship specific decision support system regarding the assessment of ship responses is by today's knowledge feasible. The feasibility of such DSS depends however on:
- wave sensors able to identify multi-peak seaways, e.g. swell and wind-sea;
- a calibrated database of ship data;
- a calibrated set of limit states and respective threshold values;
- advanced state-of-the-art motion modelling tools onboard, and
- a human-machine interface (HMI) embedded in typical bridge equipment as the conning display and designed from experts for users, not from experts for experts.
Independently, the DSS needs to be embedded within a rational procedure that:
- makes the implementation ship specific;
- ensures correctness of numerical models;
- limits uncertainties or at least quantifies them;
- strictly distinguishes between safety risks and economic risks;
- accounts for the identified requirements, and
- unambiguously identifies the limits of the support that can be expected.
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