Comprehensive evaluation on reliability of machine tools based on extension method to determine membership degree

To solve acquired the membership degree in fuzzy evaluation, we use correlation function in extension theory to calculate the degree of association between evaluation indicators and fuzzy scales, and then the degree of association is done standers conversion and normalized processing getting the membership value of evaluation matrix in fuzzy comprehensive evaluation. Comprising traditional statistical methods and expert evaluation method, the membership value of evaluation matrix which is gat through correlation function method of extension theory is more simple and reasonable. Comprehensive evaluation value is got from Calculating linear weighted between evaluation matrix and the index weight coming from analytic hierarchy process. Finally, using two type of home made NC machine tools as example to do the practical application study of the proposed method, the results show that this method can give the reasonable evaluation.