面向虚拟装配的VRML模型优化重构

对基于Web的虚拟装配中VRML模型优化重构进行了研究.提出了虚拟装配环境中的五层结构信息模型;在此基础上,分析VRML模型的语法结构和语法解析过程,建立了节点重构算法和优化处理算法;实现了VRML模型组织结构和信息描述的优化重构,很好地满足了虚拟装配快速设计与分析的需求.开发了基于Web的交互式虚拟装配原型系统,验证了模型优化重构算法的可行性.     

面向航空发动机的知识化制造系统拖期调度与自重构

针对某航空发动机装配线装配效率低、工人分配不合理等问题,建立面向航空发动机的知识化制造系统拖期调度和班组自重构优化模型.提出一种启发式算法,实现生产调度与班组配置的协同优化.在算法调度层中,针对航空发动机装配过程存在复杂约束这一特点,证明与产品拖期优化目标相关的工序排序性质,设计相应工序调整算法,给出工序在并行装配组上的初始分配方案和优化方案.在重构层,根据系统负载平衡的原则优化各装配班中装配组的数量.仿真实验结果表明了模型和所提出算法的有效性.     

基于OSP场景图结构的虚拟装配碰撞检测算法的研究与实现

快速、精确的碰撞检测对提高虚拟环境交互的真实性和增强虚拟环境的沉浸感有至关重要的作用,而虚拟装配环境的复杂性、实时性和精确性又对碰撞检测提出了更高的要求;为实现虚拟装配系统中交叉表面间的精确碰撞检测,提出一种基于OSP结构的虚拟现实碰撞检测方法;该结构第一层为对象节点,主要用于粗略的碰撞检测,第二层为表面节点,第三层为多面片节点,第二层和第三层主要用于精确的碰撞检测,采用层次的碰撞检测算法,以提高碰撞检测的实时性和精度;应用结果表明该方法能有效解决虚拟装配系统表面间的精确碰撞检测问题,满足系统实时交互的应用要求.     

一种多层分布式情境装配模型

提出一种以Agent技术为基础的多层分布式的虚拟场景模型。先从装配体的视角构建装配信息模型,根据刻画特征对象的各项参数定义装配知识层;装配决策层将零件视为Agent,并定义Agent间传输状态参数的消息模板,同时根据虚拟装配任务的过程特点,建立决策规则;最后,定义用户控制层的运动控制算法,实现对用户的运动引导。实验表明该场景模型可在虚拟场景中有效呈现装配任务,并根据上下文情境准确理解用户意图。     

基于多层虚拟拓扑节能的SDN数据中心网络流量调度算法

针对“富连接”数据中心网络在低负载时能源利用率较低的问题,提出一种节能的多层虚拟拓扑流量调度算法(EMV-SDN)。建立节能流量调度问题的整形线性规划(Integral Linear Programing,ILP)优化数学模型,使得在承载所有网络负载的前提下,网络能源消耗最小。提出节能的多层虚拟拓扑流量调度算法来求解数学优化模型,得到数据流的节能调度方案。通过休眠高层的虚拟拓扑和交换机端口实现节能,降低网络能源消耗。实验结果表明,在网络能耗和数据流平均完成时间等方面,EMV-SDN算法均优于ECMP(Equal-Cost Multi-Path Routing)以及Dijkstra最短路径算法。     

断路器柔性装配车间数字孪生系统设计

为优化断路器装配车间的产线结构和作业方法,结合数字孪生技术,提出一种基于多机器人运动控制的断路器柔性自动化车间装配方案。面向自动化装配单元,结合工业机器人的柔性装配工艺及方法,对实体装配车间进行全物理属性的数字化建模,同时建立多机器人的运动学控制模型,将机器人的三维运动模型应用于虚拟孪生场景。通过数据的交互传递,实现物理单元与虚拟单元的实时链接,将车间机器人的运动轨迹、装配状态、作业运送流程等数据信息进行实时显示,从而实现断路器柔性装配数字孪生系统的搭建与同步映射。实验结果证明,所提方案对实现断路器柔性装配有显著效果。     

飞机部件装配的路径规划算法研究与实现

同装配对象特殊、过程复杂,必须采用特殊的装配工艺方案。虚拟装配技术为飞机装配提供了可行的思路。装配路径规划是虚拟装配技术中的关键技术,是目前国内外相关领域研究的热点。本文在虚拟装配环境下飞机装配特点的讨论基础上,提出了一种基于装配体配合关系描述的装配路径规划算法,并在ＣＡＴＩＡ平台上进行了设计实现。     

基于工序集的动态关键路径多产品制造调度算法

针对已有的树状结构多产品加工和装配综合调度方法,不能兼顾树状结构纵横双向、影响调度结果的问题,提出基于工序集的动态关键路径多产品制造调度算法.该算法首先采用根对齐的方法,将多个树状结构的产品转化成一个虚拟加工树,使多产品调度问题简化为单产品调度问题;在调度过程中,根据虚拟加工树动态生成可调度的备选工序集合,按提出的动态...     

面向航空发动机装配线的知识化制造系统重调度和自重构

为了解决航空发动机装配过程中存在的不确定返工问题,建立了面向航空发动机装配线的知识化制造系统(knowledgeable manufacturing system,KMS)重调度和班组自重构优化模型,提出装配线重调度及自重构集成优化算法.在算法调度层,证明了以加权完工成本为优化目标的工序排序性质,并对工序进行初始排序.定义了3种邻域结构,用变邻域搜索(variable neighborhood search,VNS)对工序在并行装配组上的指派问题和调度问题进行优化.在重构层,在不违背装配组装配技能约束的前提下利用装配线负载平衡原则对装配班组进行配置,并采用禁忌搜索(tabu search,TS)对班组配置进行优化.仿真实验结果表明了模型与算法的有效性.     

交互式拆卸引导装配路径规划方法研究

在分析研究虚拟装配中的装配路径生成办法的基础上,根据实际需要提出了以交互式拆卸引导的装配路径规划方法的装配路径规划优化算法.算法主要通过人机交互的方式,记录零部件在拆卸过程中不同状态下每一步关键点的位置姿态信息.根据装配过程是拆卸过程反演的原则,通过“拆卸引导”形成零部件的装配路径,经过多次人机交互调试最终实现装配的最优路径.该算法的目的是生成无碰撞、无干涉的优化装配路径,从而实现虚拟环境中零部件更快捷、有效地装配.     

多约束条件下机器人柔性装配技能自学习

机器人的装配策略受装配对象特性、装配工艺和装配控制方法的约束,针对装配过程接触阶段的位姿不确定性问题,提出一种装配姿态调整技能自学习的方法.首先描述多约束条件下的机器人装配技能问题,建立基于力/力矩、位姿、关节角度等多模信息描述的装配系统模型;然后构建融合竞争架构的机器人决策网络和策略优化网络,通过与环境的不断交互,进...     

A non-parametric free-form optimization method for shell structures

This paper presents a numerical shape optimization method for the optimum free-form design of shell structures. It is assumed that the shell is varied in the out-of-plane direction to the surface to determine the optimal free-form. A compliance minimization problem subject to a volume constraint is treated here as an example of free-form design problem of shell structures. This problem is formulated as a distributed-parameter, or non-parametric, shape optimization problem. The shape gradient function and the optimality conditions are theoretically derived using the material derivative formulae, the Lagrange multiplier method and the adjoint variable method. The negative shape gradient function is applied to the shell surface as a fictitious distributed traction force to vary the shell. Mathematically, this method is a gradient method with a Laplacian smoother in the Hilbert space. Therefore, this shape variation makes it possible both to reduce the objective functional and to maintain the mesh regularity simultaneously. With this method, the optimal smooth curvature distribution of a shell structure can be determined without shape parameterization. The calculated results show the effectiveness of the proposed method for the optimum free-form design of shell structures.     

消声器薄壳辐射噪声优化

针对消声器薄壳辐射噪声声能虽小但仍不可忽略的问题,运用CAE方法对某消声器进行分析,计算得到由内部声场引起的辐射声功率和消声器的传声损失．结果表明,增加消声器薄壳的厚度可以有效减少薄壳的辐射声功率且不削弱消声器的消声性能．通过格林分析法可得到消声器薄壳表面对外部观测点的噪声贡献量,为优化薄壳辐射噪声提供参考．     

基于MSC Nastran及整车模型的动力总成悬置解耦分析和优化方法

基于六自由度刚体 悬置模型的动力总成悬置解耦分析和优化方法通常是在概念设计阶段,缺乏整车模型数据时的一种初步设计方法,由于未考虑车身刚度和质量的影响,难以反映实车状态下的真实解耦情况.为此,提出一种基于MSC Nastran及整车有限元模型的动力总成悬置解耦分析和优化的新方法,并验证该方法的正确性、可行性和有效性.     

Shape optimization of three-dimensional shell structures with the shape parametrization of a CAD system

This paper presents a method for shape optimization of flat or curved 3D shell structures, that takes advantage of the geometric modelling and automatic meshing capabilities of an existing parametric/associative CAD system. It is an extension of a method previously proposed by the authors for shape optimization of 2D and 3D solid structures. The implementation of the shell elements used is outlined, as well as the calculation of analytical sensitivities with the discrete method. The validity of the method is demonstrated with the optimization of two complex 3D shell structures.     

滚动转子压缩机转子组合结构振动特性分析与测试

为了避免压缩机转子系统在工作过程中的振动超标,需要对其开展系统化的动态优化设计,包括压缩机转子乃至整机的振动特性测试以及利用转子动力学对其建模与分析.本文以转子系统组合件(泵组件+外壳组件)为研究对象,首先创建了压缩机转子系统三维实体有限元分析模型.进一步,对转子系统的固有特性进行了分析,获得了前5阶固有频率与模态振型.最后,对该滚动转子压缩机进行了动力学实验,校验了上述分析模型的合理性.本文的研究可为压缩机系统的减振与降噪提供技术参考.     

An integrated approach for shape and topology optimization of shell structures

In this paper an automated approach for simultaneous shape and topology optimization of shell structures is presented. Most research in the last decades considered these optimization techniques separately, seeking an initial optimal material layout and refining the shape of the solution later. The method developed in this work combines both optimization techniques, where the shape of the shell structure and material distribution are optimized simultaneously, with the aim of finding the optimum design that maximizes the stiffness of the shell. This formulation involves a variable ground structure for topology optimization, since the shape of the shell is modified in the course of the process. The method has been implemented into a computational model and the feasibility of the approach is demonstrated using several examples.     

基于Abaqus和Isight的水下壳体声散射优化

针对水下椭圆壳的声散射优化问题，以壳体声散射强度最小为优化目标，以截面特征参数为设计变量建立模型。采用有限元与无限元耦合的混合优化方法，利用Python和Abaqus二次开发求解远场声散射强度，并结合Isight对水下壳体声散射进行优化。根据优化结果改进椭圆壳截面几何参数，可有效降低其声散射强度。     

A multi-objective sequential method for manufacturing cost and structural optimization of modular steel towers

This paper proposes a methodological approach for the multi-objective optimization of steel towers made from prefabricated cylindrical stacks that are typically used in the oil and gas sector. The goal is to support engineers in designing economical products while meeting structural requirements. The multi-objective optimization approach involves the minimization of the weights and costs related to the manufacturing and assembly phases. The method is based on three optimization levels. The first is used in the preliminary design phase when a company receives a request for proposal. Here, minimal information on the order is available, and the time available to formulate an offer is limited. Thus, parametric cost models and simplified 1-D geometries are used in the optimization loop performed by genetic algorithms. The second phase, the embodiment design phase, starts when an offer becomes an order based on the results of the first stage. Simplified shell geometries and advanced parametric cost models are used in the optimization loop, which present a restricted problem domain. In the last phase involving detailed design, a full 3-D computer-aided design model is generated, and specific finite-element method simulations are performed. The cost estimations, given the high levels of detail considered, are analytic and are performed using dedicated software.     

A unified approach to nonlinear buckling optimization of composite structures

A unified approach to nonlinear buckling fiber angle optimization of laminated composite shell structures is presented. The method includes loss of stability due to bifurcation and limiting behaviour. The optimization formulation is formulated as a mathematical programming problem and solved using gradient-based techniques. Buckling of a well-known cylindrical shell benchmark problem is studied and the solutions found in literature are proved to be incorrect. The nonlinear buckling optimization formulation is benchmarked against the traditional linear buckling optimization formulation through several numerical optimization cases of a composite cylindrical shell panel which clearly illustrates the advantage and potential of the presented approach.