基于稳健性和多目标优化的车顶结构轻量化设计研究

Roof structure lightweight design based on robustness and multi-objective optimization

针对国内外顶结构轻量化的研究多是单目标优化,且没有考虑不确定性因素影响的问题,提出了一种基于多目标优化和6σ稳健性设计的车顶结构轻量化设计方法。通过参数试验设计进行了灵敏度分析,筛选出了对车顶响应贡献量较大的结构件厚度作为设计变量;采用最优拉丁超立方设计和响应面法建立了车顶各响应的近似模型;以设计变量总质量、覆雪强度、抗凹性能为优化目标,前三阶模态频率为约束条件,基于近似模型,运用第二代非支配排序遗传算法(NSGA-Ⅱ)进行了确定性多目标优化,得到确定性多目标优化结果;运用蒙特卡洛模拟技术对确定性多目标优化结果进行了6σ质量分析,并进行了6σ稳健性多目标优化。优化结果表明,车顶结构在满足各性能要求的情况下实现了轻量化,质量减轻3.77 kg,且覆雪强度提高,同时车顶结构各工况性能的稳健性提高,达到6σ质量水平。

Aiming at the problem that research on lightweight of the roof structure at home and abroad are mostly single-objective optimization and do not consider the influence of uncertainty factors, a method of roof structure lightweight design based on multi-objective optimization and 6δ robustness design was presented. The sensitivity of design variable was analyzed through parameter study and the thickness of struc- tural parts which contribute more to the response of the roof structure were selected as a design variable. Optimal Latin hypercube design and response surface methodology were applied to establish approximate models of each response of the roof. Total mass of design variables, strength of roof-snow and dent resistance as the optimization objectives, the first three modal frequencies as constraint, based on approximate models, deterministic optimal solution was obtained by using the Non-dominated sorting genetic algorithm ]I （ NSGA- II ）. With the using of monte carlo simulation techniques, 6δ quality of deterministic multi-objective optimization results of roof structure was analyzed and 6δ ro- bustness multi-objective optimization of roof structure was conducted. The optimization results indicate that under the situation of meeting re- quirements of all performance, the mass of the total mass of design variables was reduced by 3.77 kg and the strength of roof-snow is in- creased. At the same time, the robustness of each working condition performance of the roof structure also was improved, reaching six sigma quality level.