【作者】 任怀伟；

【导师】 黄克正；

【作者基本信息】 山东大学 ， 机械设计及理论， 2008， 博士

【摘要】 从设计的角度讲,概念设计在产品设计过程中对产品的创新性影响最大;而从制造的角度讲,公差是影响产品可制造性、可装配性及生产成本的重要因素。如果能够将二者综合起来考虑,就可以在实现产品创新的同时保证设计方案的可行性,从而减少设计反复,有效缩短新产品的开发周期。为此,本文在国家自然科学基金项目:产品概念结构与公差同步综合进化设计理论与应用研究(项目号:50475129)的资助下,开展了产品概念结构与形位公差并行设计关键技术的研究。本文的主要研究内容和进展如下:系统综述了国内外计算机辅助概念设计、公差设计及两个领域集成设计研究的现状。为解决目前概念设计阶段集成公差设计中存在的问题,借鉴生长型设计方法,利用其在产品概念结构设计及表达方面的潜力,研究实现产品概念结构与形位公差并行设计的理论和关键技术。在理论方面,在详细论述功能表面、概念产品和分解重构原理的基础上,提出了产品概念结构与形位公差并行设计的理论架构:面向设计过程的功能分解、产品概念结构生长型设计及产品概念结构与形位公差并行设计机理。面向设计过程的功能分解与生长型设计同步进行,将当前设计步骤中能够实现的功能随时映射为具体结构;产品概念结构生长型设计是一个功能表面表达的功能零件不断分解重构的过程,利用数学方法描述了这一过程。功能表面为“功能-结构”映射提供了载体,其几何属性使公差可以直接定义到概念结构中,支持了公差集成设计。功能零件的分解重构使产品概念设计以可操作的方式进行,解决了概念设计过程难于控制的问题;提出了概念结构与形位公差并行设计的机理,通过功能驱动下的、功能零件与公差的同步分解重构实现并行设计过程。依据功能、结构和公差信息在设计过程中的相互关系,给出了概念结构与形位公差并行设计的过程模型。在技术方面,建立了支持概念结构与形位公差并行设计的功能、结构和公差信息模型。采用数据库技术定义了包含功能、行为和状态信息的产品功能模型,它能够描述产品功能间的层次和前后关系,并能够与对应的功能表面或功能零件相联系,从而支持了面向设计过程的功能分解。在广义定位原理的基础上,定义了功能模式,为功能模式推理和功能零件的分解重构奠定了基础。采用面向对象技术定义了功能表面类、零件类和产品类,构建了基于功能表面的产品概念结构层次模型。建立了单一公差项目表示模型,统一描述结构中的各种形位公差类型。基于结构层次模型建立了由单一公差项目模型组成的产品层次式公差模型,实现了产品结构与公差信息的集成。将面向设计过程的功能分解与生长型设计结合起来,共同完成产品概念结构的设计。借鉴质量功能配置的思想,建立了功能分解质量屋以实现面向设计过程的功能分解。采用基于规则的产生式推理方法实现功能模式的推理,建立了功能模式推理规则库,在此基础上研究了功能零件的生成过程。功能模式推理将功能分解与功能零件的分解重构联系起来,使功能在分解的过程中能够同步驱动概念结构的设计。提出了与概念结构设计并行的形位公差综合技术。根据功能表面定位功能的不同,定义了其相应的自由度。在此基础上分析了功能表面间的几何约束,通过约束与公差的对应关系生成结构需要的形位公差类型。提出了基于结构设计约束的三维公差链自动生成方法,由功能模式基准框架的标准化、约束变动关系链生成、形位公差类型及公差链生成4个部分组成。利用公差积累运动学模型和遗传算法进行了公差的计算和优化。建立了以公差为主要指标的概念结构评价标准,采用模糊评价法对设计方案进行评价。在上述理论和技术的基础上,基于MDT平台开发了支持概念结构和形位公差并行设计的Darfad-Tolerancing系统。以活塞精镗销孔夹具为例,详细描述了在Darfad-Tolerancing系统中进行概念结构与形位公差并行设计的过程。分析设计结果发现,单步公差链计算容易导致前后设计步骤间的公差分配前松后紧的问题,讨论了相应的解决方法。更多还原

【Abstract】 From a design point of view, conceptual design has the most important influence on the innovation in the whole design process of product. From manufacture perspective, tolerance has a big influence on the ability of being manufactured and assembled of a product. If the conceptual design and tolerancing can be considered in a concurrent way, an innovative design scheme with strong feasibility will be obtained directly after one design step. This can reduce the probability of re-design and shorten the period from an idea to a real product. Therefore, under the support of National Nature Science Fund Project (No:50475129), named Study on evolving theory and technology of synchronous synthetic tolerancing in product conceptual design, This thesis researches on the concurrent design process of product conceptual structure and geometric tolerance.The contents and contribution of this thesis are as follows:Firstly, the current research methods and contents in the field of computer aided conceptual design (CACD), tolerancing and their integration were summarized systematically. In order to solve the problems existed in the filed of conceptual design integrated with tolerancing, the method of growth design was borrowed for using its thinking about the product conceptual structure design and its representation. The research contents were presented with studying on the theories, technologies and software development.On theoretical studies, based on the investigation of functional surface, conceptual product and decomposition&reconsititution principle, the theoretical contents of concurrent growth design of product conceptual structure and tolerance were proposed, involving function decomposition oriented whole design phase, the growth design of conceptual structure and mechanism of concurrent design process of conceptual structure and geometric tolerance. The function decomposition oriented to whole design process is executed simultaneously with conceptual structure design process. The function that can be realized by existing structure will be mapped to its relative structure on time along with the function decomposition process. The growth design of conceptual structure takes functional surfaces as the object of operation in design process. The decomposition and reconstitution of functional part makes the conceptual design process operable and overcome the problem that the conceptual design process is hard to be controlled. The geometric attributes of functional surfaces allow tolerance information to associate with the product structure directly. The mechanism of concurrent design of conceptual design and tolerance was presented. Tolerancing of new parts was performed simultaneously with every step of conceptual structure design. According the relations of product function, structure and tolerance in conceptual design process, the design process model of structure and tolerance concurrent design was proposed.On technological research involving in this paper, the information model of product was built to support structure and tolerance design. It includes three models: function model, structure model and tolerance model. Function model was built by the support of database technology. It includes information on function, behavior, and status. It can describe the relations between function items and record which functional surface or part can implement the function stored in this model. Base on generalized location principle, the functional pattern was defined for the reasoning from function to structure. The classes of functional surface, part and product were defined using the object-oriented method, and then the structure model was built. Tolerance model was built based on structure model to realize the integration of product structure and tolerance.For implementing the conceptual structure design, the function decomposition oriented to whole design process was integrated with the growth design. QFD (Quality Function Deployment) was used to realize the function decomposition. Functional pattern needed in design process can be obtained by functional reasoning. The library of reasoning principles was built. The functional pattern associated function decomposition with the design of functional part. It makes function can drive structure design concurrently along with function decomposition. Conceptual structure design process is the basis of tolerancing.Tolerancing integrated with conceptual structure design was studied. Instead of only considering dimensional tolerance, the geometric tolerance was considered in this paper. The concept of DOF (Degree of freedom) was redefined to suitable for functional surface. Geomantic tolerance can be considered as constrains to the geometric variation between two functional surfaces. Three-dimensional tolerance chain was form between the new and old parts by following 4 steps: the standardization of DRF (Datum referred frame) of functional patterns, the generation of constrain variation chain between toleranced and referred surface on the new and old parts, the generation of tolerance types and three-dimensional tolerance chain. The genetic arithmetic was used to optimize the tolerance distribution results. For evaluating structures by tolerance, 4 criteria were presented and used in the method of fuzzy assessment.Based on above theories and technologies, a new system supporting the concurrent design of conceptual structure and tolerance, Darfad-Tolerancing, was developed on the basis of MDT Its system function, structure and development environment were introduced. The validity of proposed theories and technologies was proved by the design example of piston clamp. The concurrent design process of structure and tolerance of the piston clamp was described. Through analyzing the design result, it was found that one-step tolerance chain can lead to a tolerance allocation problem, and then some solution methods were discussed.更多还原