New quantitative approach based on index of optimism for fuzzy judgement of online manufacturing process

Shewhart type fuzzy charts have been immensely proposed to deal with several practical problems of fuzzy data in monitoring and examining manufacturing processes. In mediating the shortcomings of indistinguishable classification conditions of a recently proposed fuzzy (x) over bar and s charts,this paper aims at developing a quantitative approach based on the index of optimism for fuzzy judgement of online manufacturing processes. By quantifying the linguistic notion `rather' that is usually mentioned as a qualitative term in previous researches, we make it numerically measured in this study; as such, our thorough evaluation conditions of a manufacturing process, including in control, rather in-control, rather out of control and out of control, are more sufficient and justified. In addition, our proposed approach with the multi-intermittent states certainly overcome the constraints of binary classifications of traditional Shewhart type control charts when fuzzy data inevitably appear in practical manufacturing processes; hence, it fulfils the current literature of control charts.