Fuzzy expert evaluations of adverse external impacts on the marine search and rescue operations effectiveness
The paper considers using fuzzy expert evaluations of adverse external impacts upon effectiveness of various marine search and rescue operations. According to existing methodology evaluation of search and rescue operation effectiveness is cal-culated according to a mathematical model under ideal external conditions. Further it is adjusted by the probability of pairwise independent and joint events of adverse external influences for various types of activities of forces and means of a search and rescue operation, which are characterized by certain un-favorable factors with empirically determined weights (significances) decreasing the efficiency. Ab-sence of gradations for most adverse factors makes evaluation significantly rough. To overcome this fact it is proposed to abandon weights and assess the level of exposure to adverse factors using fuzzy multi-valued verbal expert evaluations. To implement such a transition, linguistic variables of adverse factors impacts are introduced. Their term-sets are determined on the basis of a person’s known abili-ties to distinguish gradations in verbal evaluations. The values of term-sets (fuzzy sets at which maxi-mum membership functions are achieved) carrier base scale are correlated with the available weights (significance) of adverse factors. The paper provides a practical example of fuzzy expert evaluation of adverse factors influence on search and rescue operation effectiveness under the assumption that the adjacent gradations of verbal evaluations by a person are equidistant and that the values on the carrier’s base scale are equal to zero in the absence of adverse factors. The use of widespread normalized triangular membership functions allows effectively evaluating and adequately adjusting the values of search and rescue operation effec-tiveness under the influence of adverse factors even with a small amount of initial data in the form of weights (significance) of adverse factors. Significant simplicity of expert choice deffuzzification im-plementation is achieved provided that the value on the base scale of the carrier can refer to no more than two adjacent terms of the linguistic variable. On the other hand, the proposed approach to use fuzzy expert evaluations can easily be adapted to detail or expand the initial data in the form of weights of adverse factors, and can also serve as the basis for further development of methods for as-sessing search and rescue operations effectiveness.