Multiobjective Optimization Method for Lifecycle Design of Machine Products

Manufacturing that minimizes the exhaustion of natural resources, energy used, and deleterious environmental impact is increasingly demanded by societies that seek to protect global environments as much as possible. To achieve this, lifecycle design (LCD) is an essential component of product design scenarios, however LCD approaches have not been well integrated in optimal design methods that support quantitative decision making. This study presents a method that yields quantitative solutions through optimization analysis of a conceptual product design incorporating lifecycle considerations. We consider two types of optimization approaches that have different aims, namely, (1) to reduce the use of raw materials and energy consumption, and (2) to facilitate the reuse of the product or its parts when it reaches the end of its useful life. We also focus on how the optimization results differ according to the approach used, from the view point of the 3R concept (Reduce, Reuse and Recycling). Our method obtains optimum solutions by evaluating objectives fitted to each of these two optimization approaches with respect to the product’s lifecycle stages, which are manufacturing, use, maintenance, disposal, reuse and recycling. As an applied example, a simple linear robot model is presented, and Pareto optimum solutions are obtained for the multiobjective optimization problem whose evaluated objectives are the operating accuracy and the different lifecycle costs for the two approaches. The characteristics of the evaluated objectives and design variables, as well as the effects of using material properties as design parameters, are also examined.