Lightweight optimization of an electric bus body frame based on the C2oDE algorithm

This work focuses on the design optimization of the electric bus body frame orienting the lightweight while ensuring the performance of stiffness, strength and crashworthiness. Based on the entropy weight-TOPSIS comprehensive contribution analysis method, the components of the bus body frame, which have significant impact on the output response of the static mode model and the rear-end collision model are determined. The thickness of the top five components with the highest contribution in the two models is used as the final design variables. Design of experiment (DOE) is carried out based on the Latin Hypercube sampling method, and then the surrogate models are fitted by the least squares regression method (LSR) based on the DOE sampling data, and the accuracy of the models are validated by error analysis. With the minimization of the body mass being as the objective and other performance responses as constraints, an optimization problem is formulated for the lightweight design optimization. The optimization problem is solved by the composite differential evolution for constrained evolutionary optimization (C2oDE) algorithm. The optimization results are evaluated through finite element (FE) simulations by comparing with that before optimization. It is revealed that after optimization the body mass is reduced by 51.59kg yielding a reduction rate of 4.99%, while the energy absorption of the rear wall increases by 2.79%, the maximum invasion is reduced by 0.36%, the invasion velocity of the center of the rear wall of the electric bus is reduced by 0.46%, and the cabin center acceleration is reduced by 3.29%. As a result, based on the proposed optimization scheme, the crashworthiness performance of the electric bus body frame has been significantly improved while posing little effect on the static and modal performance.