The Applications of Wavelets in Hierarchical Representations and Smoothing of Curves and Surfaces

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Analysis of Die Forging Process and FEA of Piston

Die forging process of piston tail and its key technology are analyzed in detail. The key issue is to reduce friction force between punch and billet to facilitate metal flow towards two ends. Three-step forging scheme is used, namely preforming, final forging and cutting the flash. Preforming is critical for the success of the whole process and two schemes are compared. First two steps are simulated using 3D-Deform software. Simulation results show that the process is feasible and its validity is verified.     

Connectivity and synchronization of Vicsek model

The collective behavior of multi-agent systems is an important studying point for the investigation of complex systems, and a basic model of multi-agent systems is the so called Vicsek model, which possesses some key features of complex systems, such as dynamic behavior, local interaction, changing neighborhood, etc. This model looks simple, but the nonlinearly coupled relationship makes the theoretical analysis quite complicated. Jadbabaie et al. analyzed the linearized heading equations in this model and showed that all agents will synchronize eventually, provided that the neighbor graphs associated with the agents＇ positions satisfy a certain connectivity condition. Much subsequent research effort has been devoted to the analysis of the Vicsek model since the publication of Jadbabaie＇s work. However, an unresolved key problem is when such a connectivity is satisfied. This paper given a sufficient condition to guarantee the synchronization of the Vicsek model, which is imposed on the model parameters only. Moreover, some counterexamples are given to show that the connectivity of the neighbor graphs is not sufficient for synchronization of the Vicsek model if the initial headings are allowed to be in [0,2π）, which reveals some fundamental differences between the Vicsek model and its linearized version.     

Approximation property of partition of unity and its applications

The linear combination of certain partition of unity, subordinate to certain open covering of a compact set, is proved to be capable of approximating to a continuous function at arbitrarily precision. By using proper open covering and partition of unity, the robust nonlinear controllers and adaptive laws are designed for a class of nonlinear systems with uncertainties. The states and parameters of the closed-loop systems can be stabilized in the meaning of UUB (uniformly ultimately bounded) via the robus tnonlinear controllers and adaptive laws. Finally, an example shows the validity of method in this paper.     

International Journal of Automation and Computing Table of Contents

Nulnberl SPeeial Seetion on ComPutational Illtelligenee in EnterPrise (Guest Editor:Professor Edward P.K.Tsang) 1EmPlOyingComPutationalIntelligeneetoGenerateMoreIntelligent H.Hagras and Energy EfReient Living SPaees 10 An Evolutionary APProaeh to the Deli…     

Modeling and Identification of Multirate Systems

Multirate systems are abundant in industry; for example, many soft-sensor design problems are related to modeling, parameter identification, or state estimation involving multirate systems. The study of multirate systems goes back to the early 1950s, and has become an active research area in systems and control. This paper briefly surveys the history of development in the area of multirate systems, and introduces some basic concepts and latest results on multirate systems, including a polynomial transformation technique and the lifting technique as tools for handling multirate systems, lifted state space models, parameter identification of dual-rate systems, how to determine fast single-rate models from dual-rate models and directly from dual-rate data, and a hierarchical identification method for general multirate systems. Finally, some further research topics for multirate systems are given.     

Specification, Refinement and Verification of Concurrent Systems—An Integration of Object-Z and CSP

This paper presents a method of formally specifying, refining and verifying concurrent systems which uses the object-oriented state-based specification language Object-Z together with the process algebra CSP. Object-Z provides a convenient way of modelling complex data structures needed to define the component processes of such systems, and CSP enables the concise specification of process interactions. The basis of the integration is a semantics of Object-Z classes identical to that of CSP processes. This allows classes specified in Object-Z to be used directly within the CSP part of the specification.In addition to specification, we also discuss refinement and verification in this model. The common semantic basis enables a unified method of refinement to be used, based upon CSP refinement. To enable state-based techniques to be used for the Object-Z components of a specification we develop state-based refinement relations which are sound and complete with respect to CSP refinement. In addition, a verification method for static and dynamic properties is presented. The method allows us to verify properties of the CSP system specification in terms of its component Object-Z classes by using the laws of the CSP operators together with the logic for Object-Z.     

International Journal of Automation and Computing

International Journal of Automation and Computing (ISSN 1476-8186) is a joint publication of Institute of Automation, Chinese Academy of Sciences and Chinese Automation and Computing Society in the United Kingdom. Editors-in-Chief Prof.     

International Journal of Automation and Computing

爪盆已阴ati口”aljo脚al ofAuto跳ation of Sei叨ees and Ch纽eseAutoma柱on and ComPuting(I SSN 1476一8186) 15 a joint Publieation of Institute and ComPudng Soeiety in the United刃ngdom. of Automation，Chinese Aeademy Prof. T N Tan Institu协ofAutol刀a生ion Chinese Academy of Sciences Beijing 100080 PeoPle，5 RePublie ofChina D刀ail:切t@刀】Pria，accn Editors一n一Chief Prof G P Liu School ofEleetronies Unive”ity ofGlam〔”退an PontyPridd CF37 IDL United Kingdom Email:gPliu@gla…     

工业人工智能的关键技术及其在预测性维护中的应用现状

随着人工智能技术的快速发展及其在工业系统中卓有成效的应用, 工业智能化成为当前工业生产转型的一个重要趋势. 论文提炼了工业人工智能(Industrial artificial intelligence, IAI)的建模、诊断、预测、优化、决策以及智能芯片等共性关键技术, 总结了生产过程监控与产品质量检测等4个主要应用场景. 同时, 论文选择预测性维护作为工业人工智能的典型应用场景, 以工业设备的闭环智能维护形式, 分别从模型方法、数据方法以及融合方法出发, 系统的总结和分析了设备的寿命预测技术和维护决策理论, 展示了人工智能技术在促进工业生产安全、降本、增效、提质等方面的重要作用. 最后, 探讨了工业人工智能研究所面临的问题以及未来的研究方向.     

A joint design of production run length,maintenance policy and control chart with multiple assignable causes

Although economic production quantity, statistical process monitoring and maintenance are three major concepts in process optimization of industrial environments, they have been often investigated separately in literature. Furthermore, in studies that consider these three concepts simultaneously, it is assumed that there is only one assignable cause in the production process. This simplified assumption is unlikely to occur in real production processes due to the usual complexity of manufacturing systems, which may lead to a poor performance in both economic and statistical criteria if the assignable cause originating the shift is different from the one anticipated at the design of the chart. To overcome these drawbacks, this paper develops an integrated model ofeconomic production quantity, statistical process monitoring and maintenance in the presence ofmultiple assignable causes. The particle swarm optimization algorithm is used to minimize the expected total cost per production cycle, subject to statistical quality constraints. Also, a comparative study is performed to illustrate the effect of considering multiple assignable causes on model’s costs. Finally, a sensitivity analysis is conducted on the expected total cost per production cycle and process variable values to extend insights into the matter.     

炼油企业全厂多周期生产计划优化研究

将生产过程和公用工程作为一个整体,建立全厂的多周期生产计划模型。全厂生产计划模型在传统的生产计划模型基础上细化了装置的能耗模型和集成了公用工程优化操作模型,实现了生产过程系统与公用工程的同时优化,避免了传统方法将生产过程系统与公用工程分割开来进行优化的缺陷。本文以中国北方某大型炼油企业为例,验证了模型的有效性。     

面向生产过程的CBM策略效益评估方法研究

针对当前设备维修策略选择主要依据人工经验或故障后果严重程度的不足,从产品生产过程涉及的多个设备维修问题出发,提出一种定量评估基于状态维修(CBM)策略效益的方法.利用离散事件仿真模拟整个生产过程,根据预测的设备故障时间分布和故障设备的维修时间构建维修策略效益评估的基本框架.以某个加工生产线为应用对象,使用ExtendSim可视化仿真软件包建立生产线的仿真模型,按照维修策略效益评估流程设计三种应用案例,评估事后维修、定期维修和基于状态维修产生的效益,结果表明,基于状态维修策略产生的效益最大,从而验证该评估方法的可行性,可为工程实际中最优维修策略的选择提供依据.     

Economic design of inspection strategies to monitor dispersion in short production runs

Short-run productions are common in industrial environments where flexibility is required in the manufacturing of parts and several product variants can be produced. Monitoring process stability during the production run is strategic to avoid the occurrence of an excessive number of non conforming units which can lead to excessive scrap or rework costs. The selection of the best control strategy can be obtained with respect to an economic objective by minimizing the cost associated with the implementation strategy. In this paper, several strategies including preventive maintenance, Shewhart, EWMA and CUSUM control charts are compared to monitor process dispersion. Constraints related to the line productivity and the inspection activities configuration have been included in the problem formulation. A proper optimization algorithm has been developed to cope with the investigated problem. A large benchmark of process scenarios has been investigated and the obtained results show that the selection of the best strategy is not a straightforward task due to the influence of several process operating parameters. Finally, a numerical example is detailed to get more insight about the investigated problem.     

The Practical Use of Empirical Studies for Maintenance Process Improvement

Many software maintenance organizations are currently attempting to improve their maintenance processes. Using empirical studies to drive and quantify such improvements is more rare, but can be seen at some organizations. During the International Workshop on Empirical Studies of Software Maintenance (WESS96), a group of people who were using empirical studies formed a panel to discuss the barriers to and successes of using such studies. This paper is a summary of that panel's discussion. As such, it uses the experiences of the participants to show that a significant amount of empirical research on industrial projects has been completed. It discusses the results of several of these studies, and their factors for success. The paper also describes key barriers that inhibit the use of empirical research in maintenance process improvement in practice and presents a set of ideas on potential areas for further empirical research in an industrial setting. This revised version was published online in July 2006 with corrections to the Cover Date.     

人工神经网络用于乙醇发酵生产过程的建模探讨

基于发酵生产的特点及建模要求,以某企业燃料乙醇生产过程为研究对象,利用工业生产中的参数及数据,建立了以乙醇发酵效果为目标的BP神经网络模型,以静态模型反映复杂的动态问题.探讨了乙醇发酵生产模型的误差产生原因,并提出改进方案,根据已有经验将相关参数进行了合理组合,调整神经网络模型的输入输出参数结构,以提高仿真模拟效果.通过多次模型改进,使模拟的平均相对误差从10%提高至5.4%,为进一步研究发酵生产建模提供了思路.     

基于Stateflow的设备维修过程仿真研究

设备维修是工业企业的一项复杂工作,提高设备维修的效率对减少维修周期、节省企业成本具有重要意义。针对传统计划评审技术（PERT）在设备维修过程工期计算和关键路线分析等方面的局限,提出了基于Stateflow的设备维修过程仿真方法,进行了实例分析。仿真结果表明,基于Stateflow的仿真分析方法能够有效评估设备维修过程的完工时间和关键线路的分布情况,具有可视化、流程化和层次化的特点。     

A methodology for joint optimization for maintenance planning, process quality and production scheduling

Performance of a manufacturing system depends significantly on the shop floor performance. Traditionally, shop floor operational policies concerning maintenance scheduling, quality control and production scheduling have been considered and optimized independently. However, these three aspects of operations planning do have an interaction effect on each other and hence need to be considered jointly for improving the system performance. In this paper, a model is developed for joint optimization of these three aspects in a manufacturing system. First, a model has been developed for integrating maintenance scheduling and process quality control policy decisions. It provided an optimal preventive maintenance interval and control chart parameters that minimize expected cost per unit time. Subsequently, the optimal preventive maintenance interval is integrated with the production schedule in order to determine the optimal batch sequence that will minimize penalty-cost incurred due to schedule delay. An example is presented to illustrate the proposed model. It also compares the system performance employing the proposed integrated approach with that obtained by considering maintenance, quality and production scheduling independently. Substantial economic benefits are seen in the joint optimization.     

Single-machine scheduling problems simultaneously with deterioration and learning effects under deteriorating multi-maintenance activities consideration

Maintenance is important to manufacturing process as it helps improve the efficiency of production. Although different models of joint deterioration and learning effects have been studied extensively in various areas, it has rarely been studied in the context of scheduling with maintenance activities. This paper considers scheduling with jointly the deterioration and learning effects and multi-maintenance activities on a single-machine setting. We assume that the machine may have several maintenance activities to improve its production efficiency during the scheduling horizon, and the duration of each maintenance activity depends on the running time of the machine. The objectives are to determine the optimal maintenance frequencies, the optimal maintenance locations, and the optimal job schedule such that the makespan and the total completion time are minimized, respectively, when the upper bound of the maintenance frequencies on the machine is known in advance. We show that all the problems studied can be solved by polynomial time algorithms.