Establishing a dynamic ergonomic evaluation index system for complex product designs based on the theory of product life cycle

Abstract

Ergonomic design and evaluation for complex product (tractor as an example) in different lifecycle stages should be different and specific according to changing business strategies. Being key factors for multi-attribute evaluation, how to define indicators and assign weights to them for tractor's different lifecycle stages are discussed in this paper. Focus group has been used for brainstorming initial indicators as many as possible. Then, indicators and their relationship-structures for three lifecycle stages were assessed and optimized by two rounds of Delphi surveys involving 15 experts. After that, a synthetic indicator weight assignment method suitable for value evaluation and ranking evaluation was proposed. Indicators' weights for value evaluation was composed by experts' value judgment weight and experts' credibility weight, the former was assigned by Group Analytic Hierarchy Process method and the latter was assigned by calculating distances between individual weight and the average weight. To differentiate alternatives' ergonomic performances clearly, weight set of value evaluation has been modified by indicator's information entropy weight. The results show that there are some significant differences in three indicator systems (for three lifecycle stages) and weight sets developed by the proposed method, and this will have significant impacts on ergonomic evaluation results, which can provide useful feedback for tractor's design during its early design stage. The proposed method can be applied to ergonomic evaluation study of other complex products in their lifecycle.