A novel spherical fuzzy QFD method and its application to the linear delta robot technology development

Extensions of ordinary fuzzy sets have been put forward one after the other in the literature. The latest extension is spherical fuzzy sets theory proposed by Kutlu Gündoğdu and Kahraman (2019a), which is based on three independent membership parameters defined on a unit sphere with a constraint related to their squared summation. This new extension presenting larger domains for each parameter is employed for production design in this paper. Quality Function Deployment (QFD) is a structured approach for defining customer needs or requirements, which translates them into the final product in order to satisfy these needs. Spherical fuzzy QFD (SF-QFD) under impreciness and vagueness involving linguistic evaluations rather than exact numerical values is proposed in this paper. The importance ratings and global weights of customer requirements (CR) and improvement directions of design requirements (DR) are successfully represented by using spherical fuzzy sets. Judgments of multi-customers/experts are aggregated by spherical fuzzy aggregation operators. A comparative analysis using SF-TOPSIS is applied for competitive firms. A linear delta robot technology design and evaluation is performed by the proposed SF-QFD and a competitive analysis is presented.