【作者】 胡朝辉；

【导师】 钟志华；

【作者基本信息】 湖南大学 ， 车辆工程， 2010， 博士

【摘要】 汽车轻量化已经成为汽车工业发展的一个关键性课题。结构优化、尺寸优化、新材料利用及轻量化工艺等都是轻量化的实施途径。目前关于轻量化实施途径的相关研究较多,但是轻量化理论体系及轻量化途径的相关分析流程需要进一步的完善。本文将多目标优化及多学科优化方法等现代设计方法加以运用,并结合近似模型及多种数值优化方法(包括作者提出的遗传蚁群混合算法)对轻量化的各种途径进行了深入的研究。从车身整体尺寸优化、零件结构优化、零件材料类型及零件规格选择优化、轻量化工艺的多学科优化设计等方面展开了详细的研究。本文主要开展了以下几个方面的研究：1.基于车身总体尺寸优化的多目标轻量化优化方法。传统的尺寸优化方法集中在零部件上,未涉及到汽车总体尺寸参数的优化。实际上,合理的汽车总体尺寸参数设计是整车取得较好轻量化效果的前提。本文在开发一款跟原车型结构相似、整车尺寸加长加宽加高的新车型时,将整车长度、整车高度、整车宽度及部分零件厚度作为设计变量,采用最优拉丁方试验设计方法进行样本数据设计,并且采用移动最小二乘响应面方法构建白车身NVH(振动噪声)、白车身关键区域强度及白车身质量等性能参数的多目标优化系统的近似模型,利用多目标遗传优化算法NSGA-Ⅱ(非支配解排序遗传算法)对近似模型进行优化。在满足白车身关键区域内强度、白车身NVH等约束性能的同时,追寻车内新增空间最大化,并实现了新车型的轻量化设计。2.基于零件形状优化的轻量化优化设计。综合遗传算法和蚁群算法的各自的优缺点,提出了一种新的基于遗传蚁群融合算法的优化策略。这种算法的特点是融合蚁群算法的特点与遗传算法(GA)交叉、变异进化策略,改善了解空间搜索的全局性。在对某车型滑移门系统进行轻量化设计时,将滑移门上中下三根导轨的形状作为优化变量,并结合Kring法构建了滑移门声学、开启平顺性等性能参数的近似模型。其中,滑移门开启平顺性的评价指标结合了某韩国专家的工程设计经验,提出了用滑移门开启时质心位置的加速度偏离整个运行过程的平均加速度的大小值来衡量整个滑移门开启的平顺性。最后用本文提出的遗传蚁群混合算法进行寻优,在满足声学和开启平顺性的同时减轻了滑移门的质量。实例显示了算法很好的优化效果。3.多材料-多零件规格组合多目标轻量化优化方法。提出一种把零部件系统的材料类型、零件规格、零件厚度组合在一起的以重量及成本最小化为目标的组合多目标优化方法。常规的轻量化设计往往在零件材料或者零件规格单一化的基础上对零件厚度进行优化设计。推导出这种多材料-多零件规格的组合多目标优化的数学模型。通过将材料类型而不是材料的多个属性、零件规格而不是零件的几何和价格属性定义为离散变量,大大降低了优化问题的复杂程度。采用最优拉丁方试验设计及最小二乘响应面方法构建了组合多目标优化系统的各个目标及约束性能参数的近似模型。利用多目标遗传优化算法NSGA-Ⅱ对组合多目标优化模型进行优化。利用此方法对某方向盘进行了轻量化设计,为验证优化结果建立了方向盘抗压试验台架。结果表明了此方法的可行性。4.面向轻量化工艺的多学科优化技术。通过多学科优化设计理论,将拼焊板技术和热成形板技术在工程问题中的应用进行了深入的研究。拼焊板的应用中：采用均匀拉丁方试验设计方法进行样本数据设计,并且采用移动最小二乘响应面方法构建了拼焊板内板门系统的刚度、强度、侧碰MDO(多学科系统)的近似模型。利用连续二次规划优化方法对此近似模型进行优化,将拼焊板内板焊缝线位置及各板件的厚度作为设计变量,在使门系统的下垂刚度、强度及侧碰性能得到提高的同时,使得门系统重量得到较大程度的减轻。热成形板的应用中：采用最优拉丁方试验设计方法进行样本数据设计,并且采用移动最小二乘响应面方法构建了白车身扭转刚度、白车身关键区域强度、整车正碰多学科系统的近似模型。利用连续二次规划优化方法对此近似模型进行优化,将采用热成形板的前中后大梁厚度、大梁内部加强板厚度作为设计变量,在满足正碰设计要求、白车身强度刚度要求的同时,大大减轻了车架的重量。更多还原

【Abstract】 Lightweight has become a crucial research topic in automotive technology. Structural optimization, size optimization, new materials and lightweight technology are all the ways of lightweight. Although there is much research on the ways to lightweight, the theoretical system of lightweight and the analysis procedure of lightweight means should also be further improved. In this dissertation, multi-objective optimization, multi-disciplinary optimization methods and other modern design methods combined with approximate model and a variety of numerical optimization methods(including the authors proposed hybid genetic algorithms) were adopted to reseach on all lightweight approaches. A detail research on overall size optimization of the white in body, structural optimization of parts, the type of materials and specifications optimiziation, and multi-disciplinary optimization in lightweight technology were carried out. This dissertation mainly carried out the following research:1. The overall size optimization based on multi-objective optimization method. The conventional size optimization methods focus on optimizing the size of components rather than the overall size of vehicles. In fact, a reasonable design of overall size of vehicles is best way of lightweight of vehicles. It develops a new car with similar structural, but with different length, height and width. The length, height and width of the whole car, thickness of the some panel are served as the optimal variables, and sampling points were obtained by using optimal Latin squares design of experimental method, at the meantime, the moving least-squares response surface approximate method are used to approximate the multi-objective system of the body-in-white NVH, body-in-white key area strength. The approximate model was optimized by using NSGA-Ⅱ(non-dominated sorting based genetic algorithm). It lightens the weight of the new body and searchs for additional space to maximize interior space which meeting the requirements of body-in-white NVH, strength.2. The lightweight design based on parts structure optimization. A new fusion algorithm is proposed based on genetic ant colony optimization strategy. The new algorithm employs Ant Colony system Algorithm (ACA) features and Genetic Algorithms (GA) crossover and mutation evolutionary strategy improves features of the global search. The performance of the door system, including the open comfort and open N V H, has been constructed by the Kring response surface approximate method. The shape of the three guide rails has been optimized by using fusion algorithm method to meet the sliding door open comfort and open NVH. Meantime, it lightens the weight of the sliding door. Based on South Korea’s experience, open NVH has evaluated by the deviation of opening acceleration between average acceleration. The example shows the feasibility of this method.3. Extended the research on multi-objective and multi-material-multi-part specification composite construction. Conventional lightweight design is often optimized for the part thickness basis of the single-material and single-specifications. While in this dissertation, a multi-objective optimization method is proposes by combining a system of the type of material, parts specifications, parts thickness with an aim to minimize the weight and cost. And the mathematical model of such a multi-material-multi-part specification composite construction multi-objective optimization is also proposed. In the mathematical model, the type of material, rather than a number of properties of materials, parts specifications, rather than part geometry and the price properties, are defined as discrete variables, which greatly reducing the complexity of optimization problems. Then the the optimal Latin squares design of experimental method and least-squares response surface approximate method are also adopted to construct the objectives and constraints. The approximate model is optimized by using NSGA-Ⅱ. The proposed method is illustrated through a case of lightweight design of a steering wheel and a steering wheel compression test rig, and the results also show the feasibility of this method.4. The Multi-disciplinary optimization for lightweight technology. A detail research on tailor-welded bank and hot-forming bank has carried on by using multi-disciplinary optimization. In the application of tailor-welded bank:Sampling points were obtained by using uniform Latin squares design of experimental method, and the MDO(multidisciplinary design optimization) approximated system, including the door stiffness, strength and side crashworthiness, has been constructed by the moving least-squares response surface approximate method. The approximate model was then optimized by using sequential quadratic programming method. The performance of the door system, including the vertical stiffness, strength and side crashworthiness, has been improved by optimizing the positions of the welding line as well as thickness of each part. In addition, the weight of the door is also reduced. In the application of hot-forming bank:Sampling points were obtained by using optimal Latin squares design of experimental method. The MDO approximated system with the body-in-white stiffness, body-in-white key area strength, frontal crashworthiness has been constructed by means of moving least-squares response surface approximate method. The thickness of the hot-forming rail member and the reinforcement panel have been optimized by using sequential quadratic programming method to meet the stiffness of body-in-white, body-in-white key area strength and frontal crashworthiness. Meanwhile, the weight of the body frame is also reduced.更多还原