Lightweight Optimization of an Electric Bus Body Frame Based on the C ² oDE Algorithm

In this work, design optimization for the lightweight of the body frame of a commercial electric bus with the requirements of stiffness, strength and crashworthiness is presented. The technique for order preference by similarity to ideal solution (TOPSIS) is applied to calculate the components that have a great impact on the output response of the static modal model and the rear-end collision model. The thickness of the five components with the highest contribution in the two models is determined as the final design variable. 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 (LSR) method based on the DOE sampling data. The error analysis of the surrogate model is carried out to determine whether it can replace the finite element (FE) model for optimization, then the optimization scheme for lightweight optimization of electric bus frame is implemented based on the algorithm of composite differential evolution for constrained evolutionary optimization (C²oDE). Comparing the optimization results with the initial values, it can be found that the mass of the electric bus body frame is reduced by 51.59kg with a reduction rate of 4.99%. Meanwhile, the energy absorption of the rear wall increases by 2.79%, the maximum intrusion is reduced by 0.36%, the intrusion velocity at the center of the rear wall of the electric bus body frame is reduced by 0.46%, the acceleration at the cabin center is reduced by 3.29%, and the crashworthiness performance of the electric bus body frame is also improved.