【作者】 马斌；

【导师】 李德群； 郭志英；

【作者基本信息】 上海交通大学 ， 材料加工工程， 2007， 博士

【摘要】 本文概述了经济活动全球化对制造业的影响以及产品虚拟开发的主要支撑技术,系统总结注塑产品虚拟设计和虚拟制造需要解决的关键问题和研究现状。根据在产品全生命周期设计不同阶段对产品信息需求深度的不同,本文创新性地提出基于虚拟现实的虚拟注塑成型开发的思路,明确定义了本文研究工作的虚拟环境,为详细的算法研究奠定了基础。本文在详细分析注塑成型工艺、虚拟现实、虚拟样机的发展现状及其发展趋势的基础上,通过集成基于虚拟现实的CAD几何建模技术、基于虚拟现实的虚拟模型物理建模和行为属性建模技术、基于虚拟现实的碰撞检测技术,开发了虚拟注塑成型原型系统。本文针对虚拟注塑成型系统中的三维建模,首先,提出了由工程语义层、精确描述层和显示交互层三个层次组成的新的几何实体数据表示模型,描述了各个层次之间的映射关系,解决了在虚拟注塑成型系统中实体建模的模型表示。提出了整合集成和直接在线集成三维建模两种方法,实现了在虚拟注塑成型系统中创建、编辑三维几何模型。针对虚拟注塑成型系统中被操作的对象只能是三角面片,重建了STL三角网格模型和四面体网格模型的拓扑信息,简化了三角网格模型和四面体网格模型。STL格式文件的拓扑重建是通过依次读取三角形,查找并去除重复的顶点,建立一个包含所有不重复顶点的顶点表和包含所有三角形的单元表,建立相互间的拓扑信息,通过有效的算法完成对边的查询。对于四面体网格模型,则采用邻接图来表达四面体网格邻接关系。利用深度优先遍历邻接图,产生四面体生成树串,通过共享的面索引和额外的顶点索引,就可以定义出下一个邻接单元。通过对网格模型的简化和拓扑关系的重建,解决了如模型太大、载入时间长、模型工程语义信息丢失等问题。本文根据虚拟注塑成型的环境特点,提出了虚拟注塑成型层次信息模型,精确表达了虚拟对象(虚拟注塑部件、虚拟注塑设备)、虚拟注塑单元(生产线)、虚拟注塑车间环境之间的拓扑关系,模型包含的信息完整,满足构建虚拟注塑成型加工环境的要求;讨论了在虚拟注塑成型系统中的物理属性建模问题,推导出了建立物理量的基本公式。从运动学、动力学角度出发,将虚拟对象划分为核心对象和非核心对象。对非核心对象建立了连接关系,对核心对象赋予其基本物理量,在计算机图形学现有成果的基础上,表现了虚拟注塑成型系统中物理属性的要求;提出了多Agent的虚拟注塑成型行为建模方法,将虚拟注塑成型划分为两种基本成分:Agent和它们之间的关系。给出了各个虚拟对象Agent的表示模型,以面向对象Petri网的状态变迁机制作为Agent的行为推理模式,以实体的几何状态、物理状态及运动状态等属性变迁的计算作为Agent行为计算方法,以Agent间相互消息传递关系来描述系统行为逻辑,给出了虚拟注塑成型的系统行为推理、行为计算、消息处理的算法,在计算机上精确表达了注塑成型过程中各个零部件协同动作,实现了虚拟注塑成型的行为过程。在虚拟注塑成型系统中,碰撞是触发虚拟对象发生行为的主要因素。本文提出了一种新的连续碰撞检测算法。该算法在每个时间区间上实时处理,把单个时间区间划分成若干个子时间区间,使用连续OBB包围盒相交检测方法,计算出在子时间区间内的潜在碰撞集,并结合三角面片之间的碰撞检测和回退技术,计算出碰撞位置和初始碰撞时间。提出了改进的碰撞检测算法,在每个虚拟对象的数据结构里添加Cache字段,记录每个虚拟对象上次发生碰撞的三角形基本的几何信息,根据局部性定理,碰撞再次发生时,通过比较与更新Cache字段中的三角形的碰撞情况,改善了碰撞检测速度。基于虚拟对象物理属性和行为属性的基础上,提出了采用Tailor级数的计算已知物理和行为属性的虚拟对象的碰撞初始时间,减少其碰撞检测的回退次数,提高了碰撞检测的速度。基于上述总体框架和关键技术的研究,本文实现了一个虚拟注塑成型原型系统,通过对注塑产品实例的虚拟注塑成型过程的实现,检验了本文提出的虚拟注塑成型原型系统结构和各个功能模型的有效性。更多还原

【Abstract】 Design of injection products is a complex process. It is very necessary for reducing the production cycle, improving the quality and winning the competition that must be considered about the product design, injection mould design, numerical simulation of injection molding, injection mould processing, and the process of injection molding. In this article, the impact of global economic activities on manufacturing industry and the main supporting technologies of product innovation engineering are summarized. The problem that should be resolved to realized real-time collaboration for virtual design and virtual manufacturing about the injection product under virtual reality are analyzed and summarized systematically. According to the different requirements for product information during different stages of collaboration in whole-product-life-cycle, the idea to realize virtual development of injection product based on virtual reality technique is presented for the first time, and the virtual injection molding environment for research work in this article is established clearly and definitely, which provides basis for the following detailed algorithm research.In this article, based on the techniques of injection molding, virtual design, virtual manufacturing, virtual prototype, the fundamental frame of injection product virtual injection molding development is established through integrating of the technique of CAD based on virtual reality, the technique of Physically-Based Modeling and behavior-based modeling and collision detection technique. This development environment supports the virtual design of the injection product and equipment and simulation of injection molding process.When develops VR-CAD technique for geometric modeling, in according with the requirements on geometric information for geometric modeling in virtual environment, geometric information model is firstly presented. This data model not only can be describing in geometric modeling but also can be applied on the simulation and evaluation in the virtual environment. Based on this data model the virtual reality technique and CAD technique are integrated. Because the triangle model is the main subject when the virtual objects act on each other, so, hierarchical product information model is put forward for virtual design or virtual manufacturing. Conquering the fault which the information about geometric model of virtual object is not complete. Aiming at different service goals, product information is presented. Complete and obvious topological information is dispensable basis for subsequent handling of triangular mesh models and tetrahedral mesh models. For triangular mesh models in STL format, an algorithm is applied in rebuilding its topological structure efficiently. For tetrahedral mesh models, adjacent graph is applied in rebuilding the topological relationship of tetrahedral set. Another then, according to topological relationship the memory capacity of triangular mesh and tetrahedral element is reduced through compressing the storage of triangular and tetrahedral element structure.In this article, the idea to simulate real injection molding in virtual environment is presented firstly, and called virtual injection molding. Based on this idea the hierarchical injection environment information model is presented. Based on this environment model, physical-based modeling is executed for virtual object in virtual injection environment, and optimized method about physically-modeling is presented. Based on the physical properties of virtual object in virtual injection molding environment, in this article, the behavior modeling method is presented firstly. There are virtual machine agent, virtual mould agent, virtual product agent and virtual hand agent in the virtual injection molding environment modeled with multi-agent system. The fundamental structure of agent in virtual injection molding is presented firstly. In virtual injection molding environment modeled with multi-agent system, the state transition mechanism described by an object-oriented Petri net is used as the agent behavior inference method. The variance computations of geometrical shape, physical properties and movement parameters are employed for the behavior computation pattern of the agents. The message processing mechanism is adopted to describe the system behavior. The algorithms for agent behavior inference are presented, and the algorithms for system behavior inference are presented.In virtual injection molding environment, independent virtual objects realize the function of injection molding through activating the messages of collision. To detect the collision between virtual objects accurately and rapidly, a novel continuous collision detection algorithm was presented. The algorithm performed well at each time interval in real-time with the time interval being divided into several sub-intervals. By using continuous overlap detection method for oriented bounding boxes (OBB), a potentially colliding set of sub-intervals was computed. The initial collision times and positions among the virtual objects were calculated by using collision detection method among triangle facets and backtracking method. In order to improve the detection velocity, the method that the field of“Cache”is added on each virtual object to record the information of collision, and compare it with the next collision detection. Based on physics and behavior modeling of virtual objects, in this article, the new method was presented by using the series of Tailor method to calculate the colliding time accurately. To some virtual objects which the property of physics and behavior has been calculated, this method would improve the velocity of collision detection.According to the theoretical studies stated above, the virtual injection molding prototyping system for injection product is developed based on the system of unix. System structure, development process model and function model proposed in this article are verified by development example.更多还原