کم کردن انعطاف پذیری در سیستم های پیشرفته تولید با استفاده از مفهوم فازی

Unlike classical logic which requires a deep understanding of a system, exact equations, and precise numeric values, fuzzy logic incorporates an alternative way of thinking, which allows modeling complex systems using a higher level of abstraction originating from our knowledge and experience. To obtain a sensible result in quantifying the manufacturing flexibility, this paper proposes some fuzzy models based on fuzzy present worth and fuzzy mathematical programming. The fuzzy models based on present worth are basically engineering economics decision models in which the uncertain cash flows and discount rates are specified as triangular fuzzy numbers. Fuzzy present worth formulae of the manufacturing flexibility elements are formed. Using these formulae, more reliable results can be obtained especially for such a concept like flexibility that is described in many intangible dimensions. The fuzzy models based on fuzzy mathematical programming allow decision-makers use upper and lower bounds for the attainment of the objectives and soft constraints. These models allow experts’ linguistic predicates about advanced manufacturing systems.

The term “advanced manufacturing systems” (AMS) is broadly defined to include any automated (usually computer oriented) technology used in design, manufacturing/service, and decision support. Components of AMS include computer-aided engineering, factory management and control systems, computer-integrated manufacturing processes, and information integration (Canada and Sullivan, 1989). Many factories have reached an intermediate stage, often called flexible manufacturing system (FMS). At this stage some machine tools, material-handling equipment, and other programmable devices are under the integrated control of a computer. FMSs can manufacture a wide range of products in batch sizes from one to thousands. They provide many important benefits such as greater manufacturing flexibility, reduced inventory, reduced floor space, faster response to shifts in market demand, lower lead times, and a longer useful life of equipment over successive generations of products.

Manufacturing flexibility is an inherently fuzzy notion which can be measured by the synthesis of its constituents. The uncertainty in expressions such as “low flexibility” or “high utilization”, which are frequently encountered in the flexibility literature, is fuzziness. This is the reason of our attempt to express the human-like way of thinking in the evaluation of manufacturing flexibility. The flexibility modeling using fuzzy concept allows experts’ linguistic predicate about automated manufacturing systems. In this paper, fuzzy present worth and fuzzy mathematical programming formulae of the flexibility elements were obtained in monetary terms. Hence, the possibility of occurrence of any flexibility value for an advance manufacturing system can be calculated easily. Such possibilistic approaches are more advantageous than the probabilistic ones, since making a probabilistic estimate requires too many observations in the strict time constraints of rapidly evolving nature of advanced manufacturing systems. For further research, continuous compounding may be used for the calculation of the fuzzy present worth of manufacturing flexibility.