A systematic approach for the sequence controller design in manufacturing systems

This paper presents a systematic approach for the design and implementation of the sequence controller in manufacturing systems. By employing the IDEF0, we construct the simplified Petri net controller (SPNC) through the material flow diagram and the information flow diagram. Then, the ladder logic diagram (LLD) can be transformed from the SPNC through the token passing logic (TPL). The proposed approach, including the IDEF0, SPNC, and TPL tools, leads to the standard IEC1131-3 LLD for PLC implementation. Finally, an application of a stamping process is provided to illustrate the design procedure of the developed approach .     

An implementation methodology for supervisory control theory

In this study, a methodology for PLC implementation of Supervisory Control Theory is introduced and realized on a pneumatic manufacturing system. The implementation methodology resolves the problem of avalanche effect and enhances program readability. We use local modular approach, which exploits modular structure of the plant and of the specifications. Local modular approach, together with the implementation methodology presented in this study provides an effective way for synthesizing and realizing supervisors for Discrete Event Systems (DES) control problems. The resulting PLC program is also modular in structure, making it handable for modification and error detection.     

Synthesis of feedback control elements for discrete event systems using Petri net models and theory of regions

This paper describes a method for constructing a Petri-net-based controller for a discrete event system (DES) modelled by a Petri net. Assuming that an uncontrolled Petri net model of the DES and a set of forbidden state specifications are given, feedback control elements, i.e. a set of places and related transitions, with initial marking, are computed using the theory of regions, which is a formal synthesis technique for deriving Petri nets from automaton-based models. When feedback control elements are added to the uncontrolled Petri net model, the controlled (closed-loop) Petri net model of the system is obtained. The controlled Petri net model obtained is maximally permissive while guaranteeing that forbidden states do not occur. The proposed method is computationally efficient and does not suffer from the state explosion problem. Two examples are provided to show the applicability of the proposed method.     

Discrete event control system design using automation Petri nets and their ladder diagram implementation

As automated manufacturing systems become more complex, the need for an effective design tool to produce both high-level discrete event control systems (DECS) and low-level implementations becomes more important. Petri nets represent the most effective method for both the design and implementation of DECSs. In this paper, automation Petri nets (APN) are introduced to provide a new method for the design and implementation of DECSs. The APN is particularly well suited to multiproduct systems and provides a more effective solution than Grafcet in this context. Since ordinary Petri nets do not deal with sensors and actuators of DECSs, the Petri net concepts are extended, by including actions and sensor readings as formal structures within the APN. Moreover, enabling and inhibitor arcs, which can enable or disable transitions through the use of leading-edge, falling-edge and level of markings, are also introduced. In this paper, the methodology is explained by considering a fundamental APN structure. The conversion of APNs into the IEC1131-3 ladder diagrams (LD) for implementation on a PLC is also explained by using the token passing logic (TPL) concept. Finally, an illustrative example of how APNs can be applied to a discrete manufacturing problem is described in detail.     

Applying an Integrated Analysis Method to Develop a Shop Floor Control System

The fundamental concept of computer integrated manufacturing is to integrate the information flow, material flow and control flow of the whole manufacturing enterprise. One major task, which might be required during the integration process, is to model the related enterprise activities. Currently, the most common method of modelling automatic manufacturing systems is to describe the system from organisational, functional, information or process points of view. Many tools or methods have been developed to support those modelling processes. However, most of those methodologies are focused only on one viewpoint. There is very little connection among various viewpoints. Therefore, gaps might exist among those models which may need extra work to bridge them while implementing the developed model. In this research, an ARIS^™ based framework to assist shop floor controller development is proposed. The major merit of using ARIS is that an integrated model containing the organisation, function, information and process entities of the shop floor can be achieved. In addition, a set of rules was developed to transfer the logic of this integrated model to the control codes of the controller during the implementation stage. The main objective of this framework is to reduce the gaps among various models and hence to shorten the system modelling and development time.     

Performance Modelling and Evaluation of Dynamic Tool Allocation in Flexible Manufacturing Systems using Coloured Petri Nets: An Object-Oriented Approach

Manufacturing systems are faced with ever-increasing customisation and unstable demand. The traditional hierarchical control structures for shop floor (pre-release planning, scheduling, dispatching and activity control) are often inflexible in responding to unexpected scenario changes and are thus not robust to system disturbances. In this paper, an object-oriented approach to modelling of FMS dynamic tool allocation and control under a non-hierarchical shop floor control scheme using coloured Petri nets is presented. A client–server paradigm is used in the proposed modelling method. The complete FMS model is partitioned into individual classes (machines, magazines, tool transport system, SGVs, tool storage, etc.) thereby significantly reducing the complexity of the model to a tractable size. The system performance under different tool request selection rules is also evaluated using coloured Petri net simulation. The proposed method can provide the designer of a tool management system with a high-level and structured representation of the tool-sharing control. It also provides an effective method for prototyping and evaluating performance of object-oriented shop floor control software.     

An Intelligent Decision Support System for Part Launching in a Flexible Manufacturing System

The effective control of flexible manufacturing systems (FMS) poses a major challenge to designers and the research community. In this paper, the framework of a unique decision support system to assist in the control of a FMS through intelligent part-launching is introduced. The proposed system makes usr of a new heuristic method based on the pull concept, and a neural network trained with data from a system simulation model, which in turn provides a desision about choosing a part to be launched into the FMS. The performance of the proposed heuristic method was tested against another popular heuristic method normally used in existing FMS via discrete event simulation models. Data sets from the simulation program of the proposed system were used to train the neural network, which can be used on the shop floor for realtime decision support. The output from the trained neural network is based on the same principle as the proposed heuristic method used in the simulation program. Therefore, the descision support provided by the neural network can be used for improved shop floor control.     

The use of the Petri net reduction approach for an optimal deadlock prevention policy for flexible manufacturing systems

In a flexible manufacturing system (FMS) with multiple products, deadlocks can arise due to limited shared resources, such as machines, robots, buffers, fixtures etc. The development of efficient deadlock prevention policies, which can optimise the use of system resources, while preventing deadlocks from occurring, has long been an important issue to be addressed. In [1], an optimal deadlock prevention policy was proposed, based on the use of reachability graph (RG) analysis of the Petri net model (PNM) of a given FMS and the synthesis of a set of new net elements, namely places with initial marking and related arcs, to be added to the PNM, using the theory of regions. The policy proposed in [1] is optimal in the sense that it allows the maximal use of resources in the system according to the production requirements. For very big PNMs, the reachability graph of the PNMs becomes very large and the necessary computations to obtain an optimal deadlock prevention policy become more difficult. In this paper, we propose the use of the Petri net reduction approach to simplify very big PNMs so as to make necessary calculations easily in order to obtain an optimal deadlock prevention policy for FMSs. An example is provided for illustration.     

PSoC在电动自行车无刷直流电动机控制中的应用

介绍了可编程片上系统PSoC(ProgrammableSystemonChip)的基本工作原理,包括内部资源、主要功能和动态配置方法等,给出了一种以PSoC芯片Cy8c24423为核心的电动自行车调速系统设计方案,分析了系统的硬件构成和软件设计思路。实际使用表明:该系统具有较好的动态性能和稳态精度,功能完善,成本低廉,具备良好的市场应用前景。     

PLC和TP在汽车密封条生产线控制中的应用

介绍了某型汽车密封条自动化生产线的控制方案,该生产线采用了PLC和触摸屏相结合的控制方式。     

数控齿条磨齿机分齿精度控制方法的研究

阐述了一种基于PLC的数控齿条磨齿机分齿精度控制方法.以PLC为控制核心,在现有伺服电机旋转编码器和滚珠丝杠基础上增加了光栅尺构成闭环控制,利用PLC的高速计数模块和高速计数中断作位置反馈处理.给出了控制结构框图,详细介绍了光栅尺测量系统和控制方法的实现.     

Effects of Dispatching and Routeing Decisions on the Performance of a Flexible Manufacturing System

This paper is concerned with the effects of dispatching and routeing decisions on the performance of a flexible manufacturing system (FMS). Three routeing policies, no alternative routeings, alternative routeings dynamic, and alternativerouteings planned are first considered with four dispatching rules with infinite buffer capacity. However, in real-life, the size of the local buffers in FMSs may be limited by the size of the part types. Therefore, further experiments to investigate the above three routeing policies with the four dispatching rules with finite buffer capacity are also conducted in order to study the impact of limited buffer capacity on system performance. In addition, the effect of changing part mix ratios is discussed with both infinite and finite buffer capacity. The performance measures considered are makespan, average machine utilisation, average flow-time, and average delay at local input buffers. The simulation results indicate that for infinite buffer capacity, the alternative routeings planned policy, combined with the shortest total processing time dispatching rule, gives the best results for all the above performance measures. For finite buffer capacity, the alternative routeings dynamic policy gives the best results in three performance measures, except for average delay at local input buffers. Further, the effect of changing part mix ratios is not significant. ID="A1"Correspondance and offprint requests to: Dr F. T. S. Chan, Department of Industrial and Manufacturing Systems Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong. E-mail: ftschan@hkucc.hku.hk     

格里森专家制造系统(GEMS)开创弧齿锥齿轮及双曲面齿轮数字化制造新纪元

格里森专家制造系统(GleasonExpertManufacturingSystem),简称GEMS系统。GEMS系统是一个集成化的计算机网络软件系统,它集成格里森基于视窗平台的圆锥齿轮软件模块(CAGETM4WIN,G-AGETM4WIN,SummaryManager,FEA,andUMCTM)于一体,提供工程工作站和格里森数控机床之间的信息通讯和互换。GEMS系统创造一个高效、无缝、协同的圆锥齿轮制造系统。本文介绍开发GEMS系统新软件模块的有关理论,包括计算机模拟数控机床加工圆锥齿轮,轻载和重载下的齿轮接触啮合模拟(TCA和LTCA),齿面误差修正,以及高阶运动误差设计等。同时介绍GEMS系统的功能和应用。GEMS系统的应用必将开创弧齿锥齿轮及双曲面齿轮数字化制造新纪元,中国已在应用这项新技术方面首先迈出了成功的一步。     

某型叉车自动变速器控制系统的快速原型和硬件在环试验研究

依据叉车工作泵的压力大小分为空载、满载、半载3种工况,计算叉车输入特性、输出特性和牵引特性,据此建立了以油门开度、车速和油泵压力为控制参数的三参数换挡规律;设计了基于dSPACE的实车快速控制原型试验,验证了换挡控制策略和执行机构策略;设计了自动变速器控制器(TCU)样机和硬件在环仿真试验台,进行了基于dSPACE的硬件在环试验,验证了控制策略在TCU样机中的控制效果。试验结果表明:基于dSPACE开发的TCU满足性能要求,并能提高开发效率,可为叉车自动变速器控制器的开发提供参考。     

起落架收放试验全电伺服控制气动载荷模拟系统性能分析

以新型起落架收放试验全电伺服控制气动载荷模拟系统为研究对象,建立新型全电伺服控制系统的数学模型,采用MATLAB/SIMULINK软件对该数学模型进行仿真。研究结果表明:仿真结果与试验结果吻合良好,最大误差在7%以内,平均误差在4%以内。验证了该全电伺服控制气动载荷试验模拟系统的合理性与有效性,说明本文设计的全电伺服控制气动载荷模拟系统自动化程度高、响应速度快、控制精度高以及可靠性好,并具有很好的载荷跟随性。     

电磁轴承数字控制系统设计及实现

电磁轴承系统的刚度、阻尼是可调的 ,所以 ,其动态性能与采用的控制器有关 ,有可能获得最优的控制策略。本文在原有模拟控制系统的基础上 ,采用 DSP技术 ,设计了一种新的数字控制系统 ,着重从控制器硬件、软件结构方面进行了讨论 ,并予以系统实施。采用工业控制专用的 DSP芯片、集成的 A/ D和数字 PWM控制输出接口 ,提高了数字控制器的速度和可靠性 ;控制器串口的设计使得其过程监控和状态分析更为方便 ;使用简单的数字 PID算法 ,实现了 8.5 kg转子的五自由度稳定起浮和旋转。这种数字控制系统可作为开发和实施实时控制策略、进行电磁轴承产品工程化的实用平台 ,也可以替代现有的模拟控制系统。     

An Optimal Deadlock Prevention Policy for Flexible Manufacturing Systems Using Petri Net Models with Resources and the Theory of Regions

In this paper, an optimal deadlock prevention policy for flexible manufacturing systems (FMSs) is proposed. In an FMS, dead-locks can arise because of a limited number of shared resources, i.e. machines, robots, buffers, fixtures etc. Deadlock is a highly undesirable situation, where each of a set of two or more jobs keeps waiting indefinitely for the other jobs in the set to release resources. The proposed optimal deadlock prevention policy is based on the use of reachability graph analysis of a Petri net model (PNM) of a given FMS and the synthesis of a set of new net elements, namely places with initial marking and related arcs, to be added to the PNM, using the theory of regions, which is a formal synthesis technique toderive Petri nets from automaton-based models. The policy proposed is optimal in the sense that it allows the maximal use of resources in the system according to the production requirements. Two examples are provided for illustration. RID=" ID=" <E5>Correspondence and offprint requests to</E5>: M. Uzam, Ni&gbreve;de &Uuml;niversitesi, M&uuml;hendislik-Mimarlik Fak&uuml;ltesi, Elektrik-Elektronik M&uuml;hendisli&gbreve;i B&ouml;l&uuml;m&uuml;, Kamp&uuml;s, 51100, Ni&gbreve;de, Turkey. E-mail: murat_uzam&commat;hotmail.com