A Study on Fuzzy Comprehensive Evaluation of Screw Pump Design Schemes with Value Engineering

Scheme design decides about 70% - 80% of the product design cost, and is critical importance to the success of product design. In this paper, a theory of fuzzy comprehensive evaluation was proposed for the selection of several options based on value engineering and fuzzy mathematics. The index system for value evaluation of the product design scheme was constructed with the function analysis method. Then based on the fuzzy control concept, the fuzzy sets including the uniform index factors, the evaluation language and so on were established, and the memberships between the factor sets and the remark sets were described with the fuzzy triangle membership functions. The fuzzy relation matrixes of the function evaluation and value evaluation were established for the products at different layers from scheme layer to goal layer, then the vectors of fuzzy evaluations were solved for defuzzification and getting the sequence of the evaluation on multiple design schemes. The fuzzy comprehensive evaluation of the project value was carried out for the 4 examples: single screw pump, double suction twin screw pump, single suction twin screw pump, and variable lead twin screw pumps. The evaluation result could give the best selection of screw pump design schemes.