General information model for representing machining features in CAPP systems

Today, the generality of computer-aided process planning (CAPP) systems and their standardization do not achieve satisfactory standards levels for industry. One of the major causes here is the difficulty of integration with computer-aided design applications, due mainly to the product model used. It is therefore necessary to identify models that are general with regard to the products, but at the same time suitable for CAPP. A product model suitable for CAPP must represent the product conceptually, enabling the development of process planning functions that operate with manufacturing concepts. It is therefore necessary to develop product information models using this philosophy. The present paper focuses on this problem and proposes an information system for representing the product for internal CAPP use. It is geared towards representing all of the part information (necessary for manufacturing) integrally with the machining features and under the same concept as these features. To this end, one of the main characteristics of the model is the absence of conventional geometric entities. The application domain of the model proposed is the assignment of processes and machines in machined parts. The GF-CAPP system has revealed that the advantages of using this type of product model in CAPP are its generality with regard to the product and the ease of developing functional procedures that are general, simple and independent.     

Determining a collision-free domain for the tool in five-axis machining

The present paper considers correction of global collisions of a milling cutter on end milling of free-form surfaces on five-axis numerical controlled machine tools. Global collision refers to the collision of the cutter body with the part surfaces and the machine parts. For a tool with a flat, torus or spherical end, which is assumed to enter into collision with its side, a corrective method that will ensure its disengagement in relation to the surfaces of the work piece was defined. The main methods available for the detection and correction of global collisions were first introduced. A determination of all solutions for non-interference using two angles of correction was then sought. A series of solutions to obtain unique positioning was then proposed. Finally, an example of a complete trajectory free from global interference was introduced to validate the method.     

A generalized multi-pass machining model for machining parameter selection in turning

A machining parameter selection model has been developed using multi-pass turning operation as a general type. An approximation optimization solution approach has been defined for this machining model. This model is a constrained model with the objective of achieving minimum cost. Depth-of-cut and number-of-pass are considered as variables in the model. All parameters, including the number-of-passes, cutting speed, feed rate and depth-of-cut for each pass, reach optimal simultaneously in one stage. The performance of this machining parameter optimization model is examined using a example, and the results are compared with current publications that provide same input data.     

Statistical expert systems for measurement problems

This article considers contemporary approaches to development of expert systems that are oriented toward statistical methods of processing measurement results.Translated from Izmeritel'naya Tekhnika, No. 12, pp. 3–7, December, 1995.     

Knowledge verification for fuzzy expert systems

Abstract

The introduction and use of fuzzy logic has strengthened knowledge representation and reasoning capability in expert systems; nevertheless, it also increases the complexity and difficulty of knowledge verification, which is known to be an important issue for building reliable and high performance expert systems. In the past decade, knowledge verification problems, e.g., redundancy, conflict, circularity and incompleteness of knowledge, have been widely discussed from the viewpoint of using binary logic; nevertheless, the issue of verifying fuzzy knowledge is seldom discussed. In this paper, we attempt to detect potential structural errors among fuzzy rules by proposing a fuzzy verification algorithm. Moreover, a system for verifying fuzzy knowledge base has been developed based on the novel approach.     

A logical model for quantification of occupational risk

Functional block diagrams (FBDs) and their equivalent event trees are introduced as logical models in the quantification of occupational risks. Although a FBD is similar to an influence diagram or a belief network it provides a framework for introduction in a compact form of the logic of the model through the partition of the paths of the equivalent event tree. This is achieved by consideration of an overall event which has as outcomes the outmost consequences defining the risk under analysis. This event is decomposed into simpler events the outcome space of which is partitioned into subsets corresponding to the outcomes of the initial joint event. The simpler events can be further decomposed into simpler events creating a hierarchy where the events in a given level (parents) are decomposed to a number of simpler events (children) in the next level of the hierarchy. The partitioning of the outcome space is transferred from level to level through logical relationships corresponding to the logic of the model.Occupational risk is modeled trough a general FBD where the undesirable health consequence is decomposed to “dose” and “dose/response”; “dose” is decomposed to “center event” and “mitigation”; “center event” is decomposed to “initiating event” and “prevention”. This generic FBD can be transformed to activity—specific FBDs which together with their equivalent event trees are used to delineate the various accident sequences that might lead to injury or death consequences.The methodology and the associated algorithms have been computerized in a program with a graphical user interface (GUI) which allows the user to input the functional relationships between parent and children events, corresponding probabilities for events of the lowest level and obtain at the end the quantified corresponding simplified event tree.The methodology is demonstrated with an application to the risk of falling from a mobile ladder. This type of accidents has been analyzed as part of the Workgroup Occupational Risk Model (WORM) project in the Netherlands aiming at the development and quantification of models for a full range of potential risks from accidents in the workspace.     

Planning of expert systems for materials selection

This paper shows a methodology for materials selection structured in five steps: 1 definition of design, 2 analysis of material properties, 3 screening of candidate materials, 4 evaluation and decision for optimal solution and 5 verification tests. The steps are illustrated with actual practical examples. The aim of article is to supply a plan for building expert system of materials selection integrated into a CAD-CAM system.     

某低温系统实时故障诊断专家系统的研究与应用

介绍了某低温系统在线故障诊断专家系统,叙述了诊断系统的基本结构及故障监测、预测和故障处理。系统使用delphi开发工具,利用各运行参数之间的逻辑关系作为推理依据,运用经验知识和理论知识相结合作为故障诊断的理论依据,对整个低温系统进行状态监测和故障诊断,指导操作人员排除故障。     

A modular architecture for rapid development of CAPP systems for agile manufacturing

Current manufacturing planning software systems, such as computer aided process planning (CAPP) systems, are general and in a closed form. It is very difficult to modify these systems to respond to a user's dynamically changing needs. These systems are no longer suitable for agile manufacturing. This paper presents research aimed at developing a novel architecture for the rapid development of CAPP systems. The architecture supports the construction of CAPP systems from prepackaged, plug-compatible software components. Specifications of the architecture and its building blocks are defined. Several important issues in architecture implementation are discussed, and an experimental system is illustrated. Finally, an Internet-based distributed CAPP system architecture is presented as a preview of next generation CAPP system development.     

Delay induced canards in a model of high speed machining

We consider here a model from Stone and Askari [Nonlinear models of chatter in drilling process, Dyn. Syst. 17 (2002), pp. 65–85] for regenerative chatter in a drilling process. The model is a nonlinear delay differential equation where the delay arises from the fact that the cutting tool passes over the metal surface repeatedly. For any fixed value of the delay, a large enough increase in the width of the chip being cut results in a Hopf bifurcation from the steady state, which is the origin of the chatter vibration. We show that for zero delay the Hopf bifurcation is degenerate and that for a small delay this leads to a canard explosion. That is, as the chip width is increased beyond the Hopf bifurcation value, there is a rapid transition from a small amplitude limit cycle to a large relaxation cycle. Our analysis relies on perturbation techniques and a small delay approximation of the DDE model due to Chicone [Inertial and slow manifolds for delay differential equations, J. Diff. Eqs 190 (2003), pp. 364–406]. We use numerical simulations and numerical continuation to support and verify our analysis.     

An analytical tim6 domain evaluation of the cutting forces in BTA deep hole machining using the thin shear plane model

This paper presents an analytical approach to describe the cutting forces in 1ST A deep hole machining processes in the time domain. The method takes into account the effect of different machining conditions. Since the cutting velocities employed in BTA deep hole machining process are relatively high, and since small chips are produced due to the presence of tool chip breakers, the analysis is developed on the basis of the thin shear plane model.

The cutting velocity is a linear function of radius and the rake angle. Cutting is different in the two regions of the cutting tool, so the total cutting force acting on the cutting tool is determined by integrating the force on a small incremental thickness of the cutting tool. This approach, to predict the value of the cutting forces without resorting to any empirical techniques, clearly illustrates the effect of various system parameters on the machining process.

The resultant force system on a new BTA cutting tool consists of an axial force and torque. But with the increase in the number of holes bored, not only does the cutting profile deteriorate, but the wear pads do too. The resultant force system will then consist of three force components and a torque, due to the fact that the forces are not balanced at the wear pads. Under such conditions, the cutting force equations derived in the latter half of the paper, coupled with the properties of the randomly varying component, can be used as the forcing function on the machine tool to evaluate not only the response but also the regions of stability and instability during the machining.     

Particle swarm optimization of a neural network model in a machining process

This paper presents a particle swarm optimization (PSO) technique to train an artificial neural network (ANN) for prediction of flank wear in drilling, and compares the network performance with that of the back propagation neural network (BPNN). This analysis is carried out following a series of experiments employing high speed steel (HSS) drills for drilling on mild steel workpieces, under different sets of cutting conditions and noting the root mean square (RMS) value of spindle motor current as well as the average flank wear in each case. The results show that the PSO trained ANN not only gives better prediction results and reduced computational times compared to the BPNN, it is also a more robust model, being free of getting trapped in local optimum solutions unlike the latter. Besides, it offers the advantages of a straight-forward logic, simple realization and underlying intelligence.     

Implementing of a three-phase integrated decision support model for parts machining outsourcing

Parts machining outsourcing (PMO) can be regarded as a strategic weapon to increase product quality and productivity as well as cost cutting in many manufacturing enterprises. However, making an outsourcing decision based on accumulated experience is neither effective nor scientific due to subjective judgement and lack of systematic analysis. Therefore, to systematically help the decision-maker survey and select suppliers to outsource and also to timely achieve the most beneficial portfolio among suppliers in a non-cooperative game structure, this paper proposes an integrated decision support model for PMO using ontology, constraint-based reasoning, fuzzy VIKOR and game theory in three phases, namely supplier prequalification, ultimate selection and order coordination. In the decision-making process, decision factors such as quality, cost and production capability are categorised and put into different phases, respectively, by their characteristics for being measured at a more reasonable method. Finally, a case from a leading printing machinery enterprise is analysed to validate the proposed model. This research is expected to improve the quality and effectiveness of decision-making in PMO.     

Application of knowledge-based expert systems for rating highway bridges

This paper presents the establishment of a Bridge Rating Expert System (BRES) by using a knowledge-based computer artificial intelligent expert system for analysis and rating of existing short span prestressed concrete highway bridges. The rating methods considered were: Inventory Rating, Operation Rating, Rating Factor Rating and Sufficiency Rating. A strength rating is based on the evaluation of existing prestressed concrete bridges in accordance with the American Association of State Highway Transportation Officials (AASHTO) specifications, and inventory rating for all bridges according to the Federal Highway Administration (FHWA) guide for the Structure Inventory and Appraisal of the Nation's Bridges. The parameters considered were bridge type, dead loads, type of vehicle loading, bridge dimensions and cross-section, material properties, reinforcement details, and existing physical condition of the bridge. The results show that, through its runtime rule controller, user interface and linkage mechanisms, the BRES is a friendly user system for rating highway bridges. In addition, the EXSYSP shell provides an effective tool for other possible applications in civil engineering practice.     

基于商品领域的P2P电子商务细粒度信任模型

为了改善现有电子商务模型信任粒度过于粗糙,致使不能完成同一节点在不同领域的信任度计算问题,提出了一种P2P电子商务系统的细粒度信任模型(FGTM)。该模型阐述了领域之间的各种关系,提出了一种划分领域关系的方法,并引入了商品领域模型和领域信任度的概念,可以针对节点在任意商品领域的信任度进行度量,充分考虑领域之间的不同关系对信任度的影响。在信任度计算方面融合了多种影响因素,并给出了初始信任度的计算方法。最后,通过仿真实验验证了模型的有效性和可行性。     

A novel method for fitting unimodal continuous distributions on a bounded domain utilizing expert judgment estimates

Recent advances in computation technology for simulation/uncertainty analyses have shed new light on the triangular distribution and its use to describe the uncertainty of bounded input phenomena. Herein, we develop a novel fitting procedure for a continuous unimodal (four-parameter) family of distributions on a bounded domain, utilizing three properly selected quantile estimates and an estimate of the most likely value. The family in question is the two-sided power family of which the triangular distribution is a member. We analyze some of the procedure's fitting characteristics and use them to estimate the waiting time distribution in a stationary M/G/1 queuing system and the completion time distribution of a small project network example taken from the shipbuilding domain.     

A framework for characterising energy consumption of machining manufacturing systems

Energy consumption in machining manufacturing systems is increasingly of interest due to concern for global climate change and manufacturing sustainability. To utilise energy more effectively, it is paramount to understand and characterise the energy consumption of machining manufacturing systems. To this end, a framework to analyse energy consumption characteristics in machining manufacturing systems from a holistic point of view is proposed in this paper. Taking into account the complexity of energy consumption in machining manufacturing systems, energy flow is described in terms of three layers of machining manufacturing systems including machine tool layer, task layer and auxiliary production layer. Furthermore, the energy consumption of machining manufacturing systems is modelled in the spatial and temporal dimensions, respectively, in order to quantitatively characterise the energy flow. The application of the proposed modelling framework is demonstrated by employing a comprehensive analysis of energy consumption for a real-world machining workshop. The characteristics of energy consumption for machine tool layer, task layer and auxiliary production layer are, respectively, obtained using quantitative models in the spatial and temporal dimensions, which provides a valuable insight into energy consumption to support the exploration of energy-saving potentials for the machining manufacturing systems.     

Design of an optical content-addressable parallel processor for expert systems

The slow execution speed of current rule-based systems (RBS's) has restricted their application areas. To improve the speed of RBS's, researchers have proposed various electronic multiprocessor systems as well as optical systems. However, the electronic systems still suffer in performance from the large amount of required time-consuming pattern-matching and comparison operations at the core of RBS's. And optical systems do not fully exploit the available parallelism in RBS's. We propose an optical content-addressable parallel processor for expert systems. The processor executes the three basic RBS operations, match, select, and act, in a highly parallel fashion. Additionally, it extracts and exploits all possible parallelism in a RBS. Distinctive features of the proposed system include the following: (1) two-dimensional representation of data (knowledge) and control information to exploit the parallelism of optics in the three RBS units; (2) capability of processing general-domain knowledge expressed in terms of variables, numbers, symbols, and comparison operators such as greater than and less than; (3) the parallel optical match unit, which performs the two-dimensional optical pattern matching and comparison operations; (4) a novel conflict-resolution algorithm to resolve conflicts in a single step within the optical select unit. The three units and the general-knowledge representation scheme are designed to make the optical content-addressable parallel processor for expert systems suitable for any high-speed general-purpose RBS.     

专家系统中基于认知的知识自动获取机制

针对专家系统中知识自动获取的瓶颈问题,从专家系统自身的潜在规律(机理)出发来改变知识发现的固有流程、形成新的知识发现过程模型和构建基于认知的知识自动获取机制,并利用T型协调器,根据基础知识库中的"知识短缺"自动地启发定向挖掘知识的途径,有效地克服领域专家的自身局限,而且做到只对那些有可能成为新知识的假设进行评价,最大限度地减少评价工作量,由此形成知识自动获取机制。这一机制在很大程度上解决了智能系统中的知识自动获取的瓶颈问题。