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Solutions to the Failures and Limitations of Mamdani Fuzzy Inference in Ship Navigation

This paper proposes a methodology for overcoming Mamdani-type inference failures on a fuzzy-logic-based decision-making process applied to collision avoidance in ship navigation. The fuzzy inference failures are observed in three distinct situations: 1) intersected contradictory decision boundaries; 2) an improper transition region between the inference boundaries of nonintersected contradictory decisions; and 3) contradictory decision accumulation under multiple obstacle scenarios. The solutions for overcoming these fuzzy inference failures and their limitations are also discussed in this paper. The proposed solutions consist of insertion of smooth transition regions, determination of the proper size of the smooth transition regions, and use of multilevel decision/action formulations. Furthermore, this paper analyzes a decision-making process for ship navigation, derives input and output fuzzy membership functions (FMFs), formulates an if-then-rule-based fuzzy inference system (FIS), and presents simulation results that support recovery from rule inference failures in several contradictory decision boundary conditions.