Knowledge-based system for the computer aided design of ingot casting processes

The complexity of the design in thermal manufacturing processes stems from the need to simulate complicated heat transfer, fluid flow and phase change phenomena and couple the results with the design rules and knowledge available of these processes to obtain satisfactory designs. In this regard, the ability of expert systems to use heuristic reasoning has proved to be a powerful tool in the computer-aided-design of thermal manufacturing systems.In this paper, the salient features of a knowledge-based system developed for the design of the ingot casting process has been outlined. A Prolog-based decision-making front-end is interfaced with a Fortran-based computational engine for rapid design. The results from the heat transfer analysis, obtained from the computational module, are coupled to the evaluation module, which checks for satisfaction of the design critera and violation of the design constraints. The decision-making module uses a set of design rules to manipulate the variables until the design specifications are satisfied. Modularity and flexibility are maintained using an object-oriented format. Several interesting design acceleration features like design inheritance from simpler models and design extraction from previous designs are illustrated. The main features of this knowledge-based tool and the savings in time resulting from using these special features are discussed in detail.     

利用用户定义特征实现基于约束设计

提出了基于约束的用户定义特征（User Defined Feature,UDF)定义与比实例化的通用机制及基于约束的特征库管理,并应用于国产CAD／CAM软件金银花（Lonicera)系统,以航空发动机转子为例,建立了转子特征库,对系统功能进行了验证。该项工作既为详细设计阶段考虑装约束和制造约束提供了方便,提高了设计效率,也为将用户定义特征与产品功能相联系、以支持计算机辅助概念设计打下了基础。     

A synthesized design for arc welding processes

The ability to make rational decisions based on the synthesis of various pieces of information and eventually arrive at an integrated design is a very important aspect of everyday engineering practice. In this paper, a conceptual framework for manufacturing design is obtained through a causal perspective. This framework is used in developing a knowledge-based system which gains insight into the process of arc welding. The knowledge-based system uses a few detailed analyses and experiments on simplified models to rationally produce an integrated design of the actual process using a hybrid axiomatic-algorithmic approach for design synthesis. The design strategy presented here may also be applied to other manufacturing processes.     

On the formulation and implementation of geometric and manufacturing constraints in node–based shape optimization

We introduce a novel method to handle geometrical and manufacturing constraints in parameter–free shape optimization. Therefore the design node coordinates are split in two sets where one set is declared as new design variables and the other set is coupled to the new design variables such that the geometrical constraint is fulfilled. Thereby no additional equations are appended to the optimization problem. In contrast the implementation of a demolding constraint is presented by formulating inequality constraints which indeed have to be attached to the optimization problem. In the context of a sensitivity–based shape optimization approach all manufacturing constraints have to be formulated in terms of the finite element node coordinates such that first order gradients with respect to the design node coordinates can be derived.     

Designing cellular manufacturing systems under dynamic and uncertain conditions

The paper proposes a fuzzy programming based approach to design a cellular manufacturing system under dynamic and uncertain conditions. The dynamic condition indicates a multi-period planning horizon, in which the product mix and demand in each period can be different. As a result, the best cells designed for one period may not be efficient cells for subsequent periods and some of reconfigurations are required. Uncertain condition implicates to the imprecise nature of the part demand and also the availability of the manufacturing facilities in each period planning. An extended mixed-integer programming model of dynamic cellular manufacturing system, in which some of the coefficients in objective function and constraints are fuzzy quantities, is solved by a developed fuzzy programming based approach. The objective is to determine the optimal cell configuration in each period with maximum satisfaction degree of the fuzzy objective and constraint. To illustrate the behavior of the proposed model and verify the performance of the developed approach, a number of numerical examples are solved and the associated computational results are reported.     

Constraint analysis: a design process for specifying operations onobjects

A design process for an object-oriented database design environment, known as constraint analysis, is presented. Given the increased level of semantics associated with an object-oriented database schema, constraint analysis makes use of semantics expressed as database constraints to support the flexible specification of propagation actions for operations on objects. Constraints are formally represented using Horn logic. The constraint analysis process then reasons about constraints at design time to help the designer understand the effects of constraints on object manipulation, identifying possible constraint violations as well as design alternatives for handling violations. An advantage of constraint analysis is that both inherent and explicit schema constraints are included in the analysis process. A formal representation is given that supports the analysis of constraints and the automatic identification of design alternatives for responding to constraint violations     

Ontology-based system for supporting manufacturing sustainability

Sustainability is one of the biggest challenges of this century either for the environment or economical growth. The required cultural shift needs challenging action that will involve deeply software and hardware aspect of manufacturing processes. In this paper, the software part of the matter is addressed by proposing a product centric ontology, in which concepts of product, processes and resources are associated to functions and sustainable manufacturing knowledge. The aim is to design a knowledge-based system that, simulating a sustainable manufacturing expert, is able to automatically identify change opportunities and to propose alternatives on the basis of the existing production scenario.     

A knowledge-based inspection process planning system for coordinate measuring machines

The coordinate measuring machine (CMM) is one of the most effective geometry inspection facilities used in manufacturing industry. To fully utilize its capabilities in a computer-integrated manufacturing (CIM) environment, we should integrate CMM with other systems and facilities. This paper presents the development of a knowledge-based inspection planner based on the fundamental principles of AI planning to integrate computer-aided design systems and CMMs. The issues involved in CAD-directed inspection process planning are examined; the task of inspection process planning is decomposed into a number of sub-tasks. According to the task decomposition, a knowledge-based planning system was designed with several modules. Each of these modules consists of a knowledge base, a control operator, a context and a communication interface. The knowledge base is the local knowledge source for problem solving; the control operator determines when and where the knowledge is applied; the context contains the initial planning state which is essential input part information, the intermediate planning states which result from the tentative decision made by the modules, and the goal state. The module interfacing was realized by directly calling procedures defined in other modules to pass the planning tasks and decisions. Examples are included to explain the planning knowledge and strategy.     

Concurrent multi-scale design optimization of composite frames with manufacturing constraints

This paper presents a gradient based concurrent multi-scale design optimization method for composite frames considering specific manufacturing constraints raised from the aerospace industrial requirements. Geometrical parameters of the frame components at the macro-structural scale and the discrete fiber winding angles at the micro-material scale are introduced as the independent design variables at the two geometrical scales. The DMO (Discrete Material Optimization) approach is utilized to couple the two geometrical scales and realize the simultaneous optimization of macroscopic topology and microscopic material selection. Six kinds of manufacturing constraints are explicitly included in the optimization model as series of linear inequalities or equalities. The capabilities of the proposed optimization model are demonstrated with the example of compliance minimization, subject to constraint on the composite volume. The linear constraints and optimization problems are solved by Sequential Linear Programming (SLP) optimization algorithm with move limit strategy. Numerical results show the potential of weight saving and structural robustness design with the proposed concurrent optimization model. The multi-scale optimization model, considering specific manufacturing constraints, provides new choices for the design of the composite frame structure in aerospace and other industries.     

An extended divide-and-conquer algorithm for a generalized class of multibody constraints

An extension to the divide-and-conquer algorithm (DCA) is presented in this paper to model constrained multibody systems. The constraints of interest are those applied to the system due to the inverse dynamics or control laws rather than the kinematically closed loops which have been studied in the literature. These imposed constraints are often expressed in terms of the generalized coordinates and speeds. A set of unknown generalized constraint forces must be considered in the equations of motion to enforce these algebraic constraints. In this paper dynamics of this class of multibody constrained systems is formulated using a Generalized-DCA. In this scheme, introducing dynamically equivalent forcing systems, each generalized constraint force is replaced by its dynamically equivalent spatial constraint force applied from the appropriate parent body to the associated child body at the connecting joint without violating the dynamics of the original system. The handle equations of motion are then formulated considering these dynamically equivalent spatial constraint forces. These equations in the GDCA scheme are used in the assembly and disassembly processes to solve for the states of the system, as well as the generalized constraint forces and/or Lagrange multipliers.     

Automated functional design of engineering systems

This paper presents a prototype intelligent system, the knowledge-based functional design automation system (KBFDA) for automating the functional design process of engineering products/systems. An integrated knowledge representation scheme combines rule-based and object-oriented representation methods to represent functions and function related design characteristics in an intelligent design environment. A knowledge-based functional reasoning strategy uses this representation to automatically generate physical behaviors from desired functions or behaviors. The required behaviors are then combined in different configurations to develop a set of potential concept variants that meet the functional requirements and functional constraints given in a design specification. Finally, the variants are ranked according to the degree to which they meet non-functional constraints. The variant with the lowest rank (score) is selected as the best solution. A case study design of a terminal insertion unit is presented to demonstrate the practicality of the proposed approach.     

Integrity constraints of manufacturing data bases

Today's manufacturing cost reduction and competitiveness largely depends on the application of automated manufacturing. Automated manufacturing could be even more efficient if computerizations of the process is taken one step further—to the integration of the design and manufacturing processes by means of or through a well-structured data base. This paper refers to several important issues related to integrity constraints in relational data bases. The literature review provides a summary of what has been done in this area by other researchers. In addition, some of the concepts proposed, developed, and even implemented before are introduced. A brief look at the classification of integrity constraints is performed by examining the real world and engineering and manufacturing worlds. This classification is supported by various manufacturing examples for each type of integrity constraints. Further, we discuss the issues of how to express and manage integrity constraints in relational data bases with particular emphasis on manufacturing applications.     

Frame-based architectures for manufacturing planning and control

Effective manufacturing planning and control (MPC) necessitates coordination and integration of various aspects of demand, production and logistics management. A holistic approach is therefore the key to success in this field. A frame-based architecture should be ideally suited to constructing knowledge-based systems for MPC, as frames can represent entities in the planning process, rules can express interrelationships between these entities, and the planning strategy is paralleled by the inference procedure. Four applications are described in detail by means of four frame-based paradigms: design of an operations regime; project planning of a new product launch; configuration of a process cell; and an analysis of the operation of an integrated manufacturing system. These architectures, and others presented in a previous article, are categorized as examples of generic tasks, a methodology proposed by Chandrasekaran¹² which defines underlying structures in terms of system goals, input/output characteristics, knowledge representation and inference strategy. The generic task approach appears to be useful in determining an appropriate architecture for a given MPC task, and also for designing and implementing the resultant knowledge-based system.     

A knowledge-based simulation environment for hierarchical flexiblemanufacturing

This article presents an approach to embedding expert systems within an object oriented simulation environment. The basic idea is to create classes of expert system models that can be interfaced with other model classes. An expert system shell is developed within a knowledge-based design and simulation environment which combines artificial intelligence and systems modeling concepts. In the given framework, interruptible and distributed expert systems can be defined as components of simulations models. This facilitates simulation modeling of knowledge-based controls for flexible manufacturing and many other autonomous intelligent systems. Moreover, the structure of a system can be specified using a recursive system entity structure (SES) and unfolded to generate a family of hierarchical structures using an extension of SES pruning called recursive pruning. This recursive generation of hierarchical structures is especially appropriate for design of multilevel flexible factories. The article illustrates the utility of the proposed framework within the flexible manufacturing context     

基于活动约束系统的变量化设计

在变量化设计过程中设计对象可以看作是一个几何约束系统,这个系统由几何元素以及作用于几何元素之间的各种约束关系构成。一个复杂的设计对象所对应的几何约束系统往往包含大量几何元素和约束关系,如果不加区别地把所有的几何元素和约束关系纳入变量化求解的范围,则很难满足交互设计的需要。而另一方面几何约束系统又往往是稀疏系统：（1）作用于任一几何元素的约束很少;（2）与任一约束相关的几何元素很少。基于这一事实给出了一种预处理策略从原始几何约束系统中搜索得到一个规模较小的活动约束系统,变量化求解在活动约束系统上进行。该方法已在自行研制的参数化造型系统GEMS5．0中实现。     

协同设计环境下的版本管理模型

计算机支持协同设计（computer supported cooperative design）是计算机支持协同工作CSCW的一个应用领域,也是CAD技术在未来发展的趋势。由于协同设计中多个人员共同参与设计,必然引进约束来保证协同。需要对设计对象和约束进行协调管理。协同设计中设计对象存在着多个版本。如何保证约束和设计对象版本间的一致对于协同设计的顺利进行具有重要意义。针对这些特点,作者提出了一种基于约束的层次化的管理协同设计版本的模型。     

Designing decision support in an evolving sociotechnical enterprise

Modern manufacturing facilities are subject to organisational, technological, engineering and market constraints. The combination of these factors allows them to be described as sociotechnical enterprises. Control of these enterprises is distributed between human and automated agents who collaborate as part of a joint cognitive system. One of the challenges facing these industries is a need to evolve operations while maintaining stable performance. Cognitive Systems Engineering (CSE) provides a range of analytical frameworks that can be used to study the effects of change on sociotechnical systems. However, the scale of these enterprises and the range of decision-making styles involved make the selection of an appropriate framework difficult. A critical review of both positivist and hermeneutic approaches to cognitive systems research is provided. Following this a cognitive engineering process is outlined that uses a mixed model approach to describe system functionality, understand the implications of change and inform the design of cognitive artefacts that support system control. A case study examines the introduction of pervasive automation in the semiconductor manufacturing industry and is used to demonstrate the utility of this process.     

A technique for optimally designing fibre-reinforced laminated plates under in-plane loads for minimum weight with manufacturing uncertainties accounted for

A procedure to design symmetrically laminated plates under buckling loads for minimum mass with manufacturing uncertainty in the ply angle, which is the design variable, is described. A minimum buckling load capacity is the design constraint implemented. The effects of bending–twisting coupling are neglected in implementing the procedure, and the golden section method is used as the search technique, but the methodology is flexible enough to allow any appropriate problem formulation and search algorithm to be substituted. Three different tolerance scenarios are used for the purposes of illustrating the methodology, and plates with varying aspect ratios and loading ratios are optimally designed and compared.     

Delta算子系统具有圆形区域极点约束的非脆弱H∞滤波器设计: 一种LMI优化方法

研究了一类Delta算子线性系统具有圆形区域极点配置的非脆弱 H∞滤波器设计问题. 本文的目的是设计滤波器使得滤波误差系统不仅满足给定的圆点极点约束或D稳定约束, 而且从扰动输入到滤波误差的传递函数满足给定的 H∞范数约束. 所设计的滤波器具有乘性的滤波器增益变化, 基于Lyapunov稳定性理论和线性矩阵不等式方法, 给出具有区域极点配置的Delta算子离散系统非脆弱 H∞滤波器存在的充分条件. 数值仿真例子说明设计方法的有效性以及所提设计方法具有更小的保守性.