Performance Modelling of Complex Dynamic Production Systems Using Temporised Object-Oriented Petri Nets with Changeable Structure (TOPNs-CS)

An object-oriented Petri net with changeable structure (OPN-CS) is capable of modelling complex dynamic production systems subject to changes. However, an OPN-CS is limted to functionality modelling of the system. For performance modelling of a complex dynamic production system, OPNs-CS are extended to temporised OPNc-CS (TOPNs-CS). The extension is carried out by temporising OPNs of production resources and the message passing relationships among production resources. The methods of capturing some performance proprieties based on a TOPN-CS model of a system are presented. A case study is provided to show how TCPN-CS is used for modelling complex dynamic production systems. TOPNs-CS can be applied in control, scheduling, and optimisation of the processes of a dynamic production system subject to changes.     

An adaptive agile manufacturing control infrastructure based on TOPNs-CS modelling

In this paper, an infrastructure for adaptive production control in an agile manufacturing environment is proposed. With this infrastructure, Virtual Production Systems (VPSs), each of which takes care of the production of a specific customer ordered product, can be dynamically and flexibly constructed. This can be achieved logically by product workflow and physically by the resources in one or more manufacturing systems, e.g. job shops. To respond to changes and disturbances to a VPS, architecture for the adaptive controller of a VPS is designed based on adaptive control principles and Temporised Object-Oriented Petri Nets with Changeable Structure (OPNs-CS) modelling. A case study is used in this paper to illustrate how adaptive production control of VPS functions can be conducted to cope with changes and disturbances to the production system.     

Process Variety Modeling for Process Configuration in Mass Customization: An Approach Based on Object-Oriented Petri Nets with Changeable Structures

Mass customization strategies could be usefully deployed by companies whose products are characterized by a modular design. Typically, each module serves a specific aspect of the overall product function at varying performance levels. Each product variant (constructed through a unique combination of modular performance levels), therefore, serves to customize the overall performance of the product, thus serving the unique needs of each customer. The high demand for each module guarantees economies of scale and, eventually, low cost to customer. The rationale of configuring production processes for producing individual product variants originates from the fact that massive process data is commonly available in a firm and there exists a generic process structure underlying the production of similar products in a family. To design a decision support mechanism that constructs process configuration corresponding to a given product configuration, this paper develops a formal modeling of process variety using Petri nets. Object-oriented Petri nets (PNs) with changeable structures (OPNs-CS) are applied to deal with the issues of generic representation, constraints compliance, and operational sequence requirements. Object-oriented PN (OPN) models facilitate generic representation of product and process variety as well as their instantiations. The OPNs-CS model is tested with simulation. Based on simulation results, the optimal configuration of production processes can be determined for each individual product as well as the cohort of a product family. To illustrate the feasibility and potential of OPNs-CS based process variety modeling, a case study of process configuration for mass customized textile spindles is reported.     

STOCHASTIC OBJECT-ORIENTED PETRI NETS （SOPNS） AND ITS APPLICATION IN MODELING OF MANUFACTURING SYSTEM RELIABILITY

Object-oriented Petri nets (OPNs) is extended into stochastic object-oriented Petri nets (SOPNs) by associating the OPN of an object with stochastic transitions and introducing stochastic places. The stochastic transition of the SOPNs of a production resources can be used to model its reliability, while the SOPN of a production resource can describe its performance with reliability considered. The SOPN model of a case production system is built to illustrate the relationship between the system's performances and the failures of individual production resources.     

MODELING OF FMS BASED ON UML AND OPNS

0INTRODUCTIONFleXiblemanufactunngsystem(FMS)isanadVancedmanufaeturingtechnology.FMScontrolsoftwaresupportingbothsimulationandcontrolimplementationisp~unttoexploitthefullbenefitsofFMS.Thecontrolsoftwarehastobedesignedtomeetthereal-timeconstraintsofaPnductionsystemanddynamicallychangingneedsOfthemalket.Hence,developmentmethodologiesarecriticaltodesignandimplementreusableanddrintainablecontrolsoftwaretorealizethefullbenefitsofFMS.ItisdifficulttouseanyonemethodtomodelsocomplexsystemasF…     

An entropy-based model of plastic deformation energy dissipation in sliding

In order to study the individual energy dissipation mechanisms which act in plastic deformation in sliding, an entropy production model of the sliding process is constructed. Rather than a physical material body, the system considered is a geometric space in which metallic lattice defects can exist. This system can interact with its environment which is the space of annihilated defects. In this system model energy dissipation through structural changes caused by defect creation and heat generation due to defect annihilation are included. For a behavior in which the defect annihilation rate is exponentially dependent on temperature, the minimum entropy production rate system evolution criterion predicts the existence of two different stationary entropy production rate states. In one state entropy production is dominated by structural changes and in the other by heat generation. Changes from one of these states to the other during sliding may account for the formation of a varying sliding body microstructure along the sliding direction.     

汽车安全气囊智能螺母拧紧设备研制

设计了一种新型的自动拧紧螺母生产设备—汽车安全气囊智能拧紧机。阐述了该设备的工作原理、结构设计及控制系统。该设备能自动高效地完成汽车安全气囊装配螺母拧紧工作,改变了目前汽车安全气囊生产行业成品装配工序手工操作伺服拧紧扳手的生产现状,降低了工人的劳动强度,提高了生产率,保证了产品质量。     

Failure classification using poles and corresponding residuals of transfer function

Using the relationship between coefficients and poles and corresponding residuals of a transfer function as well as their dependence on various physical influences, a method for failure classification is proposed in this paper. Experiments show that poles and residuals used as features permit a better classification than the use of coefficients. The method is applicable when parts of the system can be modelled by linear quasi-time-invariant transfer characteristics, the parameters of which depend on external physical influences (see Fig 1). This situation is frequently encountered in electromechanical systems.

Changes of parameters are required to be either step-like or slow compared with the system dynamics. Hence influences as varied as temperature changes, fatigue and production tolerances can be treated. Parameter variations that result in structural changes are allowed. The approach is also applicable using poles and zeroes as features instead of poles and residuals. The advantage of the latter approach is the fixed relationship between poles and residuals.     

基于增强现实的数字孪生加工系统建模与多视图交互

针对数字孪生加工系统上下文数据异构多样、缺乏高效可视化人机接口的问题,提出一种基于增强现实的数字孪生加工系统多视图交互方法.基于数字孪生技术构建了面向增强现实的加工体系,并建立了面向数字孪生加工过程的信息集成模型;研究了数字孪生加工系统的多视图生成过程,可动态实现虚实注册和动态跟踪,增强操作者与加工系统之间的高效协作能...     

形式化语言驱动的相似工艺检索原理和方法研究

工艺检索是在单件、小批量整机生产模式企业中实施CAPP系统时需要解决的主要问题之一。本文基于工艺重用的思想,提出了一种新的相似性工艺检索原理,并以此原理为基础规整了在产品结构树中查找具有相似工艺的零件查询描述语句。基于形式语言的原理定义了一种形式化零件查询语言。建立了一种产品结构树的实体关系型数据组织模型,在此基础上,论述了这种语言驱动的相似工艺查找方法。讨论了利用此原理查找相似性工艺的系统结构各组成模块,最后对此方法的特点进行了探讨。     

Requirements analysis of production management software systems

A methodology and an expert system are presented for use in determining software requirements for production planning and control systems. A dual taxonomy of production systems is proposed, based on both functional types and industrial sectors. The main aim is the production of a tool for identifying changes to the standard software or the organization of the firm which would produce the maximum benefit, based on the system concepts of potential and feasible changes. The methodology is implemented with the help of software engineering tools ranging from structured systems analysis to an object-oriented expert system shell with simultaneous support of the hypercard technique.     

基于过程控制网的协同设计建模与分析

为解决协同设计中多任务实例并发执行,以及设计过程动态控制的可视化与形式化问题,提出了协同设计全过程的概念及其形式化方法——过程控制网。协同设计全过程由设计对象、设计阶段和过程转移机制组成。过程控制网是在面向对象Petri网的基础上,通过扩展其变迁的语义得到。设计对象建模为托肯,过程转移建模为过程网,各设计阶段建模为单元网,过程网和单元网通过特定的变迁进行交互。最后,给出了协同设计全过程的过程控制网模型的运行实例。多实例并行执行所产生的变迁序列表明,该模型不仅胜任动态设计过程的控制,而且允许多个任务按照不同的过程定义同时执行。     

Framework to evaluate manufacturing capability using analytical hierarchy process

Manufacturing capability of a firm is given by the level of output generated by the production system employed which in turn decides the competitiveness in the market. The pattern of structural and infrastructural decisions in the manufacturing affects the capability of the production system. Therefore, it is crucial to know the overall manufacturing capability of a firm and the contribution of each decision in it. This paper presents quantification of manufacturing capability based on multi-criteria approach. A total of 33 decisions (criteria) and their corresponding choices have been identified from the literature analysis to quantify the manufacturing capability. These decisions are then classified into six decision areas (group criteria), and the manufacturing capability evaluation problem is modeled by using analytical hierarchy process (AHP) framework. The approach facilitates computation of manufacturing capability index by evaluating the decisions taken in the manufacturing, which is then mapped into four levels, namely, infant, industry average, adult, and world class as proposed by the Miltenburg. The methodology is illustrated with a numerical example for a job shop manufacturing system.     

An accelerated inverse perturbation method for structural damage identification

In the previous study, the inverse perturbation method was used to identify structural damages. Because all unmeasured DOFs were considered as unknown variables, considerable computational effort was required to obtain reliable results. Thus, in the present study, a system condensation method is used to transform the unmeasured DOFs into the measured DOFs, which eliminates the remaining unmeasured DOFs to improve computational efficiency. However, there may still arise a numerically ill-conditioned problem, if the system condensation is not adequate for numerical programming or if the system condensation is not recalibrated with respect to the structural changes. This numerical problem is resolved in the present study by adopting more accurate accelerated improved reduced system (AIRS) as well as by updating the transformation matrix at every step. The criterion on the required accuracy of the condensation method is also proposed. Finally, numerical verification results of the present accelerated inverse perturbation method (AIPM) are presented.     

Assessing the structural complexity of manufacturing systems configurations

Modern manufacturing systems are increasingly required to be flexible and adaptable to changing market demands, which adds to their structural and operational complexity. One of the major challenges at the early design stages is to select a manufacturing system configuration that both satisfies the production functional requirements and is easy to operate and manage. A new metric for assessing the structural complexity of manufacturing system configurations is presented in this paper. The proposed complexity metric incorporates the quantity of information using an entropy approach. It accounts for the complexity inherent in the various modules in the manufacturing system through the use of an index derived from a newly developed manufacturing systems classification code. The code captures the effect of various component types and technologies used in a manufacturing system on the system’s structural complexity. The presented metric would be helpful in selecting the least complex manufacturing system configuration that meets the requirements. An engine cylinder head production system is used to illustrate the application of the proposed methodology in comparing feasible but different manufacturing system configurations capable of producing the cylinder head based on their structurally inherent complexity.     

生产系统的开放化动向

一、前言 近几年,随着CIM和FA技术的引入、不但加快了制造企业信息化的发展、同时也使其应用逐步普及。另外,在信息处理技术方面,计算机的标准化与以内部网络为代表的通信技术的发展也很快,其发展成果将是具     

可重组制造系统

可重组制造系统是一种能够快速响应新的生产环境的新型制造系统，在快速响应市场变化和个性化生产方面具有重要的意义。阐述了可重组制造系统的发展历史、概念、分类、重组特性及其特点，评述了目前可重组制造系统的研究现状，讨论了可重组制造系统的关键技术，并提出了可重组制造系统应用研究的发展方向。     

A novel design strategy for iterative learning and repetitive controllers of systems with a high modal density: Theoretical background

This paper discusses the design and application of iterative learning control (ILC) and repetitive control (RC) for high modal density systems. Typical examples of these systems are structural and acoustical systems considered in active structural acoustic control (ASAC) and active noise control (ANC) applications. The application of traditional ILC and RC design techniques, which are based on a parametric system model, on systems with a high modal density has several important drawbacks: the design procedure is complex, the controllers require much computational power and the robustness of the controllers is low. This paper describes a novel strategy to design noncausal ILC and RC filters, which is especially suited for high modal density systems. Since it does not require a parametric system model, the novel strategy avoids several drawbacks of the traditional techniques: no cumbersome parametric model estimation is required; the ILC and RC controllers are robust to small changes of the poles and zeros of the controlled system; and the complexity of the ILC and RC control filters is restricted. A crucial element in the proposed strategy is the noncausal filtering in the ILC and RC controllers, which requires the availability of a trigger signal to announce a new ILC trial or RC period in advance. A numerical validation on a simulation model proves the potential of the developed strategy.     

Automatic control of a One-of-a-Kind Production cell

This paper reports the outcome of a research project which aims to solve the problems in automatic control of the shop floor in One-of-a-Kind Production (OKP) through developing a prototype control system for an experimental OKP cell at the laboratory. The main problems in automatic control of the shop floor in OKP are the frequent changes of product structure or type and consequent changes of production system configuration. These changes in OKP make it necessary to have a highly flexible and robust automatic control system. To resolve the problems, a distributed control system has been developed at the CIM laboratory of the Department of Production, Aalborg University, Denmark. This control system has enough flexibility and robustness to cope with the aforementioned changes in OKP. To support the design and implementation of the control system, several concepts, algorithms and control principles, such as task logic routes, address code of production resources, automatic task decomposition algorithm, generic control modules and distributed control principles are also proposed in this paper.