动态环境下基于混合迭代的耦合集求解方法

针对产品开发过程中存在的耦合迭代情况,建立了动态环境下基于混合迭代的耦合集求解模型。该模型考虑了任务执行工期的不确定性、任务输出分支的不确定性和资源分配的不确定性对项目完成时间和开发成本的影响,通过引入一个资源分配矩阵K,采用任务返工概率矩阵和任务返工量矩阵确定任务的执行状态和返工工作量。最后,通过实例仿真计算项目的时间和成本的分布。计算结果表明,资源不确定性对耦合集执行时间和开发成本有很大的影响,对资源进行重新分配有利于减少任务执行时间,降低开发成本。     

基于设计结构矩阵的耦合任务迭代重叠建模和分析

为优化产品开发过程,把重叠引入耦合过程的研究中。以高斯消去算法为基础,给出了在两任务耦合情况下,确定耦合任务上、下游关系的方法。在建立信息修改比率参数数学描述的基础上,充分考虑到过程重叠时分别由任务返工和并行通讯所产生的时间消耗,结合高斯消去法和耦合任务的迭代特性,给出了两耦合任务迭代情况下开发时间的数学模型。最后,用工程实例验证了该数学模型,并分析了模型中部分参数的特性。     

考虑信息不确定性的串行迭代时间模型的研究

串行迭代模型中信息不确定性导致任务的迭代返工,增加了任务的总执行时间。针对这一问题,通过对上、下游串行任务执行过程的分析,得出造成信息不确定性的主要原因,确定信息不确定度函数,构建考虑信息不确定性的串行迭代时间模型。进而通过对该模型的分析得到任务间的依赖关系指数和上、下游设计人员间的交流次数对迭代返工时间的影响规律,从而为缩短产品开发过程中任务的迭代返工时间和总执行时间提供了理论参考。以某机械产品的开发项目为例,验证了模型的有效性。     

成熟度驱动的开发过程耦合活动迭代模型

针对复杂产品开发过程中的迭代问题,引入信息成熟度概念,提出信息成熟度名义进化函数和基于活动期望返工概率的有效进化函数。在此基础上,研究了输入信息更新时活动信息成熟度的进化过程,并针对具有耦合关系的多个开发活动,建立了由活动信息成熟度驱动的耦合活动重叠迭代模型。为验证模型的有效性和灵活性,以某型号汽车顶盖冲压模具开发过程为例对模型的应用进行描述,并探讨了模型在多方面为开发过程管理和优化提供支持的可行性。     

活动重叠的复杂产品开发过程仿真分析

为了更有效地对复杂产品开发过程的时间-成本-质量进行预测分析,提出了活动重叠的复杂产品开发过程仿真方法。将活动重叠分为顺序重叠和反馈重叠,提出了将信息输入矩阵和信息输出矩阵用于量化评价重叠情况;采用任务返工概率矩阵、返工影响矩阵、学习效应曲线及质量改进矩阵来描述设计过程的迭代特性;基于活动重叠和迭代提出了时间、成本、质量的计算方法,并改进了产品开发过程仿真算法。最后,通过一个实例证明了该模型的有效性和实用性。     

产品开发的多输入多输出活动重叠模型研究

针对产品开发过程中串行活动间可能存在的重叠情况,根据上游活动的信息进展度与下游活动的信息敏感度,提出返工迭代重叠模型,结合设计结构矩阵将其应用到普遍的多输人多输出产品开发过程中.对模型中的信息进展度和敏感度等重要参数进行讨论,揭示了它们对重叠效果的影响,说明了采用重叠方式可能存在的风险性.最后,给出该活动重叠方法的实施步骤并应用于某产品开发中,较好地验证了本文方法的可行性与有效性.     

基于内部迭代的耦合任务集求解方法

针对并行迭代模型中的工作转移矩阵模型存在的缺陷,从任务迭代时间、信息传递的不完备特性以及迭代次数的有限性等方面进行了修正,建立了改进的并行迭代模型,进而结合遗传算法,求解多阶段模式下耦合集的最优执行工期和成本。用该模型求解两个产品开发过程的耦合任务集,验证了其有效性,并进一步分析了影响耦合集工期和成本的因素。     

耦合活动重叠执行过程的时间模型

为提高并行设计的效率,针对并行开发过程中的耦合活动重叠执行方式,深入分析了耦合活动的迭代过程后,提出了一个考虑设计活动敏感度和可变度的时间计算模型。首先采用返工概率函数积分的方法,计算各设计活动的重叠修改时间,再采用非齐次泊松过程,描述下游设计活动发现上游设计活动错误的随机过程,并在构建各设计活动进化度函数的基础上,运用数理统计方法计算各设计活动的反向修改时间,进而建立耦合活动设计过程的时间计算模型。最后,结合某型柴油机活塞连杆组改进设计的实例,运用MATLAB优化工具箱对其开发时间进行优化计算。运算结果表明了该时间模型的有效性,并为企业提供了均衡时间和成本的分析方法。     

支持设计过程仿真的逻辑迭代结构模型及其仿真

针对现有设计结构矩阵不能完整地表达产品开发过程中存在的复杂信息迭代关系,从而造成基于该模型的开发过程仿真结果的不确定性大和开发过程时间的控制难、导致产品开发计划延误的缺陷,提出一种有利于表达产品开发过程中复杂信息迭代关系的逻辑迭代结构树模型,将过程中迭代间所具有的逻辑关联作为过程模型中的重要迭代规则,以改进传统模型中由于信息不完善而造成的过程仿真偏差;建立基于逻辑迭代结构树网的设计过程仿真模型,开发相应的设计过程仿真软件,并以摩托车制动器产品的开发过程仿真为例进行了验证.结果表明新方法能更加全面有效地表达影响产品开发进度的各种因素,减少传统方法中由于模型信息不完善产生的结果失真,进一步提高产品开发过程分析与评价的准确性,有利于提高企业产品开发计划的可实施性.     

并行产品开发过程的时间模型及其优化方法

针对并行开发过程中设计活动间存在迭代和重叠的情形,提出一个时间计算模型及其优化方法。依据矩阵规划后的设计结构矩阵,将设计活动组划分为多个耦合活动块和非耦合活动块,按信息流方向依次计算活动重叠造成的设计修改时间,进而建立产品开发的时间模型。在给定成本约束下,将开发时间最短问题转化为有约束的最优化问题,并给出相应的求解算法。最后通过实例运算表明了时间模型及其优化方法的有效性。     

Multi-segment and multi-ply overlapping process of multi coupled activities based on valid information evolution

Complex product development will inevitably face the design planning of the multi-coupled activities,and overlapping these activities could potentially reduce product development time,but there is a risk of the additional cost.Although the downstream task information dependence to the upstream task is already considered in the current researches,but the design process overall iteration caused by the information interdependence between activities is hardly discussed;especially the impact on the design process’ overall iteration from the valid information accumulation process.Secondly,most studies only focus on the single overlapping process of two activities,rarely take multi-segment and multi-ply overlapping process of multi coupled activities into account;especially the inherent link between product development time and cost which originates from the overlapping process of multi coupled activities.For the purpose of solving the above problems,as to the insufficiency of the accumulated valid information in overlapping process,the function of the valid information evolution(VIE) degree is constructed.Stochastic process theory is used to describe the design information exchange and the valid information accumulation in the overlapping segment,and then the planning models of the single overlapping segment are built.On these bases,by analyzing overlapping processes and overlapping features of multi-coupling activities,multi-segment and multi-ply overlapping planning models are built;by sorting overlapping processes and analyzing the construction of these planning models,two conclusions are obtained:(1) As to multi-segment and multi-ply overlapping of multi coupled activities,the total decrement of the task set development time is the sum of the time decrement caused by basic overlapping segments,and minus the sum of the time increment caused by multiple overlapping segments;(2) the total increment of development cost is the sum of the cost increment caused by all overlapping process.And then,based on overlapping degree analysis of these planning models,by the VIE degree function,the four lemmas theory proofs are represented,and two propositions are finally proved:(1) The multi-ply overlapping of the multi coupled activities will weaken the basic overlapping effect on the development cycle time reduction(2) Overlapping the multi coupled activities will decrease product development cycle,but increase product development cost.And there is trade-off between development time and cost.And so,two methods are given to slacken and eliminate multi-ply overlapping effects.At last,an example about a vehicle upper subsystem design illustrates the application of the proposed models;compared with a sequential execution pattern,the decreasing of development cycle(22%) and the increasing of development cost(3%) show the validity of the method in the example.The proposed research not only lays a theoretical foundation for correctly planning complex product development process,but also provides specific and effective operation methods for overlapping multi coupled activities.     

Concurrent design process analysis and optimization for aluminum profile extrusion product development

Owing to intricate interdependency and information feedback among tasks, the concurrent design process probably cannot converge to the correct solution when there are wrong integration and improper interaction between activities. Therefore research on concurrent design process optimization is necessary. In the paper, a novel methodology is proposed to analyze and optimize the concurrent engineering process scientifically. Based on design structure matrix and graph theory, coupled task recognition and design task level plotting are performed for the concurrent design process of aluminum profile extrusion product development. Three factors are used to describe the coupling property of activity, namely sensitivity, complexity and affection factors, which provide the basis to analyze development process quantitatively. And an optimism algorithm is presented to define the initial iteration order of coupled task set. Finally a rational and efficient concurrent design process model is constructed, which can make aluminum profile product development faster, with lower costs and higher quality. The methodology proposed is also applicable to other concurrent engineering fields.     

并行产品开发中设计活动间重叠与信息交流

基于对设计活动的技术创新程度和上游信息对下游设计活动的重要程度,提出了知识累积函数和设计返工函数。针对下游活动的介入时间和信息交流次数,建立了信息单向传递的并行产品开发模型,通过构造考虑产品开发时间和成本权衡的全局收益变量,证明了全局收益极大值的存在性。在此基础上,分别给出了最优介入时间和最优信息交流次数的计算公式和设计活动间执行模式的判定条件。最后,通过实例验证了该结论的正确性。     

A STEP AP224 agent-based early manufacturability assessment environment using XML

Early design assessment activities have a significant impact on reducing the cost of manufacture. The efficient utilisation of the product development time and the level of coordination of the early design activities between the major stakeholders are becoming key factors for success in manufacturing today. The paper reports on a new distributed early design manufacturability assessment methodology using collaborative autonomous agents. A product data model compliant with STEP AP224 and corresponding process and facility data models are proposed to support the decision-making process. XML was used as a medium for exchange of requests and information between design, manufacturing, and facility planning agents. A prototype Web-enabled system for rapid product manufacturability assessment in the extended enterprise has been developed using distributed multi-agent CORBA objects. The reported research is a step towards the development of a generic prototype tool for collaborative design evaluation and rapid assessment of the manufacturing feasibility and resource availability at different stages of the product development process.     

Manufacturing Cost Modeling for Product Design

The process of product design is driven toward achieving design specifications while meeting cost targets. Designers typically have models and tools to aid in functional and performance analysis of the design but few tools and little quantitative information to aid in cost analysis. Estimates of the cost of manufacture often are made through a cost multiplier based on material cost. Manufacturing supplies guidelines to aid in design, but these guidelines often lack the detail needed to make sound design decisions.A need was identified for a quantitative way for modeling manufacturing costs at Motorola. After benchmarking cost modeling efforts around the company, an activity-based costing method was developed to model manufacturing cycle time and cost. Models for 12 key manufacturing steps were developed. The factory operating costs are broken down by time, and cost is allocated to each product according to the processing it requires. The process models were combined into a system-level model, capturing subtle yet realistic operational detail.The framework was implemented in a software program to aid designers in calculating manufacturing costs from limited design information. Since the information tool provides an estimate of manufacturing costs at the design prototype stage, the development engineer can identify and eliminate expensive components and reduce the need for costly manufacturing processing. Using this methodology to make quantitative trade-offs between material and manufacturing costs, significant savings in overall product costs are achieved.     

An Intelligent Knowledge-Based System for Product Cost Modelling

An intelligent knowledge-based system for product cost modellingis presented in this paper. The developed system has the capability of selecting a material, as well as machining processes and parameters based on a set of design and production parameters; and of estimating the product cost throughout the entire product development cycle including assembly cost. The proposed system is applied without the need for detailed design information, so that it can be used at an early design stage, and, consequently, redesign cost and longer lead time can be avoided. Hybrid knowledge representation techniques, such as production rules, frame and object oriented are employed to represent manufacturing knowledge. Fuzzy logic-based knowledge representation is applied to deal with uncertainty in the knowledge of cost model to generate reliable cost estimation. This paper deals with cost modelling of both a machining component and an injection moulding component, which is a process that gives high production rates, excellent quality and accuracy of products, and low manufacturing cost. Based on the analysis of the moulded product life cycle, a computer-based cost model was developed which integrated the relationship between cost factors, product development activities, and product geometry. The estimated cost included the costs of material, mould and processing. The system has been validated through a case study.     

产品开发活动的并行规划

针对并行工程产品开发过程中的活动规划问题,提出了一种启发式的规划方法,综合考虑了时序、信息、资源、活动执行时间、各活动的并行关系等关键因素,使算法能够保证资源的有效利用和信息的平滑流动,算例是某产品开发过程优化的一部分,结果表明了该算法的可行性。