Simultaneous structure design optimization of multiple car models using multiobjective evolutionary algorithm and FEM structure analysis

Abstract

A design system for simultaneous structure design optimization of multiple car models is developed and applied to a simultaneous design optimization of MAZDA CX-5 (SUV), MAZDA6 wagon (large vehicle), and MAZDA3 hatchback (small vehicle) to demonstrate feasibility of the developed design tool. The objectives of this design optimization problem are minimization of total weight of three car models and maximization of number of common thickness parts. This problem is difficult to find good Pareto-optimal designs because (1) number of design variable is large (222), and (2) number of constraints is large (45). To find the Pareto-optimal designs of this problem efficiently, an evolutionary multiobjective optimization algorithm named Cheetah is adopted. To evaluate crash performances accurately, a finite-element software LS-DYNA is used for each crash mode. To overcome difficulty in computational time, the K computer is used, where the required computational time is about 600 hours using 73,728 cores of the K computer. As a result, many designs that outperform the initial design developed by Mazda Motor Corporation are found and useful trade-off information between the minimization of total weight and maximization of number of common thickness parts is obtained.

Keywords

• car
• structural design
• multiobjective optimization
• evolutionary algorithm
• supercomputing
• finite element method