Modular Design Method Of Vehicle BIW Structure In Conceptual Design Stage

With the gradual maturity of the automotive industry and the continuous improvement of people’s living standard,the demand of consumers has started to be diversified and even be personalized.The onefold or a small number of vehicle models have been unable to meet the needs of many different consumer groups.In order to adapt to the market competition,many big automobile enterprises need to adopt a new R&D approach to achieve control of production costs and rapid or even parallel development of a variety of models simultaneously.In such a demand,modularized design has become the mainstream development direction of the automotive industry today.However,China’s automobile industry has not yet entered the modular R&D mode,and the domestic vehicle cannot or is difficult to form a product family with rich serial products,so it is lack of market competitiveness.Therefore,the modular independent research of automobile has become imperative.In a complete vehicle structure,the body plays the role of "skeleton" in bearing,and its cost can account for 30-60%of the whole vehicle cost.And,the decision of conceptual design stage determines 70%of the overall cost of the product.Therefore,the modularized design of the body in the conceptual design stage is particularly important.In this paper,the white body in conceptual design stage is taken as the object.This dissertation mainly includes the following research contents:Firstly,the relevant research of the module division of a single level model is carried out.Based on the graph decomposition algorithm,this dissertation makes improvements that are suitable to the engineering problems.The solution is found with the genetic algorithm,and the assembly structure design scheme in optimal cost with guaranteed performance is obtained.The entire body is divided into multiple sub-components,and each sub-component can be designed as a separate module.In addition,for the problem that the mathematical model can not converge after adding the thickness of the dividing element as design variables,a quadratic optimization method is proposed to effectively improve the convergence of the algorithm.Then,on the basis of the previous paragraph,the research on the module division of multi-level models is further carried out.Compared with the traditional platform design method,the greatest advantage of modularized design is that component commonality can be achieved at all levels in whole series.In this dissertation,coding in the genetic algorithm is taken as operand,and the iterative population comparison as the starting point.The vehicle optimization population of different levels is compared to find the local guaranteed solution to achieve the modularized design of cross-level models based on the universal idea of the module in the manner of module adding,module stretching and the combination of them.Next,the method research of module classification and screening of various modules is carried out.The modules are divided into four categories in this paper:personality module,parameterized module,flexible module and universal module.For each module,a corresponding screening method is put forward:the personality module is selected according to the size characteristic;the parameterization module is selected according to the minimized additional costs;the flexible module is screened based on the sensitivity analysis release constraint;and the rest is the universal module.According to the above sequence,the modules are sequentially filtered,and the modularized design scheme of each model can be obtained,which plays a guiding role for the forward design of the body.In addition,the research on the distribution and versatility of side reinforcement is also carried out.The design of stiffeners cannot be considered in traditional conceptual design.The stiffened structures also contain several structural reinforcements.Therefore,the design scheme of side body in conceptual design stage will not be able to meet the engineering manufacturing requirements,and other ways should be proposed for supplement.In this dissertation,the collaborative optimization algorithm is improved,and a multi-level one-time constraint algorithm is obtained.Combined with the previous optimization results,we can get the design scheme of manufacture,distribution and versatility of the structural parts and reinforcement in the side-body structure,which has further improved the modularized design of the vehicle body structure in the conceptual design stage.Finally,in order to maintain the integrity of the essay,a forward design has been carried out preliminarily.After getting the body modularized design scheme by using the previous method,the structure library of modules is established according to the design and various levels of body structure size.Through the call to the module in the library,the forward design of new models can be achieved:one can get the corresponding models of modularized design only by entering the dimensions of body structure of in length,width and height.In this research,the overall theoretical framework of modularized design of white body structure in conceptual design stage is constructed,and the guiding ideology of modularized design in the initial stage of body structure design is introduced,which realizes the module division and screening of vehicle body structure and the design of reinforcement module,and also provides a clear reference scheme for the detailed design stage later.All of above are full of clear innovative significance and important engineering signification.