面向企业能源消耗过程的模糊Petri网模型研究

针对企业能源消耗系统模型的需求性,在分析企业能源消耗过程的特点和模糊Petri网基本原理的基础上,从实用、可行的角度探索基于模糊Petri网的企业能耗过程模型,详细阐述了面向企业能源消耗过程的模糊Petri网模型的定义和运行规则,并依据特定的建模原则,进行举例说明.模型的建立独立于特定的能源类型和用能设备,全面反映企业能耗过程及其影响因素,为进一步仿真分析企业能耗状况提供了依据.     

制造系统建模中Petri网的工具和方法

本文概述了Ｐｅｔｒｉ网研究方面的一些最新研究结果，讨论了基于Ｐｅｔｒｉ网的一些建模工具，这些工具特别适合于制造系统的建模，性能分析，实时控制、系统可靠性系统等，文中还介绍了实际应用中所获得的某些结果，最后，提出了Ｐｅｔｒｉ网在制造系统建模中需解决的若干问题。     

基于模糊Petri网的变电站故障诊断研究

变电站应用SCADA系统可以获得大量继电保护和断路器动作信息,然而这些信息可能是不完全不确定的,这限制了故障诊断的有效性和正确性。文章尝试使用模糊Petri网来处理SCADA系统获得的这些不确定信息,以期获得较好的并行处理性和容错性。在模糊Petri网的基本概念的基础上,阐述了搜索故障区域的方法,建立了故障诊断的模糊Petri网模型。运用文中所提出的方法进行了实例研究,仿真分析结果说明了方法的可行性。     

模糊Petri网在液压同步提升系统故障诊断中的应用

研究了基于可信度的合成式模糊产生式规则的表示方法,在此基础上,将模糊Petri网与矩阵运算相结合,给出了模糊推理过程的形式化推理算法,将复杂的推理过程采用矩阵运算实现,充分利用了模糊Petri网的并行处理能力,利用此理论及方法可以大大减少诊断时间,提高了准确度．最后以液压同步提升系统故障诊断为例证明算法的可行性和准确性．     

一种模糊petri网仿真工具的设计实现

文章将面向对象思想应用于模糊Petri网仿真工具的设计和实现过程,探讨了模糊Petri网建模与仿真的可视化问题,提出了基于网格可视化技术解决方案及具体实现方法。通过对变速箱的自动建模和诊断仿真实例,证明该系统具有良好的实用性,为模糊Petri网理论的普遍应用提供了工具平台。     

基于Petri网的加工系统递阶智能控制

运用模糊推理与Petri网方法对加工过程的智能控制进行建模,在建模中采用了递阶智能控制的原理,将其分为组织级、协调级和执行级三个层次。组织级采用模糊推理的方法,并用标识模糊Petri网为其推理过程进行建模;协调级设计中,以一台加工中心、一个机械手组成的加工系统为例,运用模糊Petri网为其协调级进行了合理规划。     

Development of thermal error model with minimum number of variables using fuzzy logic strategy

Thermally-induced errors originating from machine tool errors have received significant attention recently because high speed and precise machining is now the principal trend in manufacturing processes using CNC machine tools. Since the thermal error model is generally a function of temperature, the thermal error compensation system contains temperature sensors with the same number of temperature variables. The minimization of the number of variables in the thermal error model can affect the economical efficiency and the possibility of unexpected sensor fault in a error compensation system. This paper presents a thermal error model with minimum number of variables using a fuzzy logic strategy. The proposed method using a fuzzy logic strategy does not require any information about the characteristics of the plant contrary to numerical analysis techniques, but the developed thermal error model guarantees good prediction performance. The proposed modeling method can also be applied to any type of CNC machine tool if a combination of the possible input variables is determined because the error model parameters are only calculated mathematically based on the number of temperature variables.     

一种新的基于Petri网的分层工作流过程模型

过程模型的描述能力和分析能力难以满足企业的要求,为此,提出了一种新的基于Petri网的分层工作流过程模型。在深入研究各种工作流模型的基础上,通过对基本网进行一定的扩展,给出工作流过程的分层模型。该模型由工作流描述模型和工作流分析模型组成。工作流描述模型直接支持所有工作流模式,特别是多实例、取消、高级同步等高级Petri网无法直接描述的模式。工作流描述模型在Petri网的基础上增加了控制变量,并将变迁划分为变迁入口和变迁体两部分。控制变量与变迁之间构成读写关系。变迁入口函数通过判断控制变量,消解工作流描述模型中的冲突;变迁体函数通过可扩展逻辑描述语句,实现对控制变量的读写操作。工作流分析模型作为工作流描述模型的分析模型,剥离了工作流描述模型个案的语义信息,可以直接利用已有的Petri网分析技术来分析模型。最后,通过几个例子说明了如何使用本文提出的模型对各种复杂流程进行建模和分析。     

Progressive development of an absolute sensorless compensation system for cutting force-induced error

Cutting forces in traditional machining processes solely originates from the contact points on the cutting tool and workpiece. Therefore comprehensive mechanistic modeling of the machining process offers a means for realizing a sensorless cutting force monitoring system. This paper presents the progressive development of a sensorless compensation system for cutting force-induced error, whereby a learning and intelligent computer system is established, based on machining mechanics modeling and a reference compensation system. Experiences from normal machining sessions of new cutting tools and workpieces are modeled progressively and incorporated into the system. Finally with ample experience available, a full-fledged sensorless system is developed as a stand-alone solution. The sensorless system is economical, convenient, reliable and efficient. Administered on a CNC face milling machine, the model demonstrated exceptional performance and robustness.     

基于Petri网的海关业务流程工作流模型分析

Petri网作为当今最具有前途的建模工具,它的应用几乎涉及到计算机学科的各个领域。这里通过对基于Petri网的海关业务流程工作流模型的实例分析,最终得出优秀的工作流模型可以优化工作流程、提高企业运行效率、增强企业竞争力的结论,而且该建模方式也为设计与开发高可靠性、柔性和适用性的工作流模型提供很好的依据。     

A control strategy with motion smoothness and machining precision for multi-axis coordinated motion CNC machine tools

The advanced manufacture technology requires that multi-axis coordinated motion computer numerical control (CNC) machine tools have the capability of high smoothness and high precision. At present, the study of the motion smoothness mainly concentrates on the acceleration and deceleration control method and the look-ahead process of velocity planning in the interpolation stage. The control strategy of the contouring error mainly focuses on tracking error control, cross-coupling control, and optimal control. In order to improve the motion smoothness and contouring precision for multi-axis high-speed CNC machine tools, a multi-axis modified generalized predictive control approach was presented in this paper. In the control strategy, the estimation models of tracking error, contouring error, velocity error, and acceleration error were structured separately. A new improved quadratic performance index was proposed to guarantee the minimum of these errors. Generalize predictive control was also introduced, a multi-axis generalized predictive control model was deduced for motion smoothness and machining precision for multi-axis coordinated motion CNC system, and an approved multi-axis generalized predictive controller based on the model was designed in this paper. The proposed predicted control approach was evaluated by simulation and experiment of circular, noncircular, and space line trajectories, respectively. These simulative and experimental results demonstrated that the proposed control strategy can significantly improve the motion smoothness and contouring precision. Therefore, the new position control method can be used for the servo control system of multi-axis coordinated motion CNC system, which increases motion smoothness and machining precision of CNC machine tools.     

机器人装配状态变迁控制的同步Petri网模型

采用同步Petri网对机器人自动化装配过程进行建模 ,更加全面地反映了装配状态变迁过程中的力 /位姿信息特征 ,在此基础上研究了任务级上装配状态变迁路径的评价方法及优化算法 ,该方法可用于指导产生具体的装配命令并可在不确定性存在时收敛到最终装配状态。     

机床自适应控制的新进展

提出一种可自学习、自组织,兼具约束式和是佳式的特征的铣削适应控制系统。系统实现以软件为主,综合使用模糊数学、神经元网络、专家系统等多种共工智能工具建模。建模方法具有一定的通用性,同时也避免了研究切削规律、精确度建模困难。实验证明,该系统可在刀具耐用度不减的条件下提高生产率４０％以上,并可提高加工精度。     

Building AGV traffic-control models with place-transition nets

Owing to the lack of robust design and control algorithms, most current applications of automated guided vehicle systems (AGVSs) employ simple control methods despite the fact that the system is far from efficient. Recently, Petri nets have evolved into a powerful tool for modelling complex manufacturing systems. One of the advantages of the use of Petri nets is that analysis, simulation and on-line control can all be done on the same model once the model is built. The purpose of this paper is to establish the research fundamentals in the field of the Petri-net modelling of an AGVS. The main contribution of the paper is to define basic traffic-control nets which can be used directly to model an AGVS without too much thinking. Some basic AGV Petri-net control elements are described and illustrated in detail. Also, difficulties in the use of bidirectional flows are discussed, and it has been determined how Petri nets can be used to solve these problems.     

基于模糊概率Petri网系统的故障诊断仿真研究

利用面向对象思想、高级Petri网技术、模糊及概率理论,建立了一种描述复杂系统故障关系的模型.着重介绍了基于该模型的故障诊断仿真控制策略,包括控制层策略和操作层策略.讨论了该模型的网元素实现,定义了5个库所类、5个变迁类、1个模糊概率Petri对象类、1个模糊概率Petri对象类的派生类和3个Token对象类,并给出了基于该模型的故障诊断仿真算法.最后,介绍了基于该模型的故障诊断仿真系统设计,并以简单的仿真实验验证了模型及仿真算法的适用性.     

Robot actuation using air motors

In view of the high investment and tooling cost of a CNC machining centre, the cutting and idle times should be optimised by considering the tool consumption and the non-machining time cost components. In this paper, we propose a detailed mathematical model for the operation of a CNC machine tool which includes the system characterisation, the cutting conditions and tool life relationship, and related constraints. This new module will be a part of an overall computer-aided process planning system to improve the system effectiveness and to provide consistent process plans. A hierarchical approach is presented for finding tool-operation assignments, machining conditions, appropriate tool magazine organisation and an operations sequence which results in the minimum production cost.     

浅谈Mastercam与数控机床仿真软件课程教学相结合的优势

将Mastercam自动编程与数控机床仿真软件课程教学相结合,实现建模-编程-模拟数控加工的教学流程,整个课程教学过程可在计算机上操作完成。该教学模式与传统Mastercam结合数控机床操作相比,具有诸多优势,研究对于课程的建设及推广起着重要作用。     

基于设计结构矩阵和着色Petri网的产品设计过程建模与仿真

将设计结构矩阵与着色Petri网结合后,进行了产品设计过程建模与仿真的研究。首先利用设计结构矩阵对产品设计过程进行建模,从产品设计过程特点出发,为支持基本过程逻辑的描述定义了着色Petri网基本网模型结构,将设计结构矩阵映射为着色Petri网,建立了产品设计过程着色Petri网模型。在此基础上建立了对设计资源进行有效分配的动态分配模型,通过定量仿真分析,实现了产品开发过程资源冲突的检测及资源的重新分配和调整。桥式起重机小车设计的实例说明了该方法的有效性。