Quality Function Deployment System Modeling And Application

Quality function deployment(QFD) is a customer-driven quality improvement method that aims to meet customer needs in a better way and enhance organizational capabilities.Typically,a QFD system can be broken down into four inter-linked phases to fully deploy the customer needs phase by phase,from customer needs into design requirements,which are also known as engineering characteristics and subsequently into parts characteristics,process plans and production requirements.Each translation uses a chart,called "House of Quality"(HoQ).From the view of system,QFD is a complex system with input,process and output and thus an important application of system engineering in product design.QFD includes the establishment of HoQ and decision making with HoQ.On the basis of the fundamental theory of QFD,to solve the intrinsic infinity that brought by infinite input information and subjective evaluation in the early stage of product design, deep and systematic research is done on QFD with infinity method of system theory.The main contents are summarized as follows:To obtain the final importance ratings of the customer requirements in quality function deployment(QFD),a method based on two-tuple linguistic was proposed.Due to the imprecision and vagueness of people's perception,the two-tuple linguistic model was introduced in QFD to represent linguistic information.And a convenient method was given to transform different granularity linguistic information.Two-tuple linguistic operators were used to aggregate the information and further determine importance ratings of customer requirements.Moreover,market competitive assessment and competitive target were considered to correct the fundamental importance ratings,and the final importance ratings of the customer requirements were determined based on the combination of the fundamental importance ratings and the correct factors.A fuzzy linear programming(FLP) model is proposed.The input variables are treated as linguistic variable,and then fuzzy linguistic term sets and corresponding fuzzy numbers are established to represent the variables.With respect to all the relationships between the customer needs and engineering characteristics and correlations among the engineering characteristics,A FLP model is established aiming to find the optimal target values of the engineering characteristic to maximize the customer satisfaction.With the fuzzy modeling of QFD,the target values of engineering characteristics can be optimized.A new method to rate the engineering characteristics in house of quality of product planning is proposed based on fuzzy,data envelopment analysis.With respect to the environment and cost,the house of quality is established.At the same time,triangular fuzzy numbers are used to represent all the factors in HoQ.Then,a new method based on fuzzy DEA is used to rate the engineering characteristics,in which,each engineering characteristic is considered to be a decision making unit,the relationships between the engineering characteristic and all the customer needs are regarded as output factors,while effect on the environment and cost are regarded as input factors.The importance of the engineering characteristic is determined by the efficiency score.In the establishing of HoQ,it is an objective method to determine the functional relationship by using technical assesses and competitor analysis matrix in HoQ.To solve the problem of insufficient data,grey correlation analysis is introduced in QFD.It is regarded as a grey system with the customer needs as reference sequences and the engineering characteristics as comparative sequences.Furthermore,the relationship matrix between the customer needs and the engineering characteristics is determined by grey correlation degree and the weights of the engineering characteristics can be determined by grey advantage analysis.With respect to the relationships of the WHATs,extended HoQ and extended waterfall model are proposed.To establish the HoQ,simultaneous equations model is first put forward to establish the house of quality.In the structural equations of simultaneous equations model,the coefficients of the endogenous variables represent the correlation matrix of the customer needs,while the coefficients of the exogenous variables denote the relationship matrix between the customer needs and engineering characteristics.All the coefficients can be easily determined by two-stage least squares estimation of the simultaneous equations model.The structural simultaneous equations model is suitable to represent the structure of the house of quality.