Web-based virtual operating of CNC milling machine tools

This paper attempts to propose a virtual operating system applied to operation training of manufacturing facility and manufacturing process simulation. The system is based on VRML and browser/server structure, so user only needs to install a free plug-in, and run the package normally via Microsoft Internet Explorer. Initially this paper studies the system framework, structure models and concept models. Then, a communication approach based on VRML, Java and HTML, which is key to realize the virtual operating of CNC machines, has been presented. The algorithm of material removed simulation based on VRML Z-map is also presented in this paper. It has the advantages such as a lower memory requirement, and a faster computation speed. Finally, in order to validate the feasibility of the proposed approach, the CNC milling machine has been taken as an illustrative example for the prototype development.     

A portable virtual machine for Ada

A portable compiler can be constructed by letting it generate code for a virtual machine, which is then implemented on the real target machines. The design of a virtual machine which is especially suitable as a target machine for compiled Ada programs is described. The main design goals, implementability on mini-computers and portability, are discussed and the resulting design is described in some detail. Some implementation strategies for the machine are proposed and the feasibility of the virtual machine approach is discussed.     

Dynamic translation for virtual machine based traffic simulation

For virtual machine based traffic simulation platforms, the paper proposes a software framework that performs trace-based dynamic translation. Through monitoring the runtime execution status of bytecodes and translating frequently executed bytecodes, also known as hot spots, into equivalent native machine codes, the framework considerably improves the performance of virtual machine based traffic simulation platforms up to ten times or more, as the experiments showed. For the first time, the presented work clearly exhibits that a seamless combination of the two technologies – dynamic translation and virtual machine could lead to a new generation of applicable traffic simulation platforms. Such a platform not only offers high flexibility in terms of traffic model simulation, but also preserves the ability of conducting numerical computation-intensive simulations generally found in real-life industrial projects.     

Towards High-Fidelity Machining Simulation

The main purpose of any machining simulation system is to reveal or mimic the real machining process as accurately as possible. Current simulation systems often use G-code or CL data as input that has inherent drawbacks such as vendor-specific nature, incomplete data, irreversible data conversions and lack of accuracy. These limitations hinder the development of a truthful simulation system. Hence, there is a need for higher-level input data that can assist with accurate simulation for machining processes. In addition, there is also a need to take into account of true behaviour and real-time data of a machine tool. The paper presents a High-Fidelity Machining Simulation solution for more accurate results. STEP-NC is used as the input data as it provides a more complete data model for machining simulations. The status-quo of the machine tool is captured by means of sensors to provide true data values for machining simulation purposes. The outcome of the research provides a smart and better informed simulation environment. The paper reviewed some of the current simulation approaches, highlighted the current simulation problems, discussed input data sources for smart machining simulation and introduced the high-fidelity simulation system architecture.     

A distributed implementation of a virtual machine for Java

The cluster virtual machine (VM) for Java provides a single system image of a traditional Java Virtual Machine (JVM) while executing in a distributed fashion on the nodes of a cluster. The cluster VM for Java virtualizes the cluster, supporting any pure Java application without requiring that application be tailored specifically for it. The aim of our cluster VM is to obtain improved scalability for a class of Java Server Applications by distributing the application's work among the cluster's computing resources. The implementation of the cluster VM for Java is based on a novel object model which distinguishes between an application's view of an object (e.g. every object is a unique data structure) and its implementation (e.g. objects may have consistent replications on different nodes). This enables us to exploit knowledge on the use of individual objects to improve performance (e.g. using object replications to increase locality of access to objects). We have already completed a prototype that runs pure Java applications on a cluster of NT workstations connected by a Myrinet fast switch. The prototype provides a single system image to applications, distributing the application's threads and objects over the cluster. We used the cluster VM to run, without change, a real Java Server Application containing over 10 Kloc

1 Kloc means Kilo lines of code—used to describe the size of applications in terms of source lines count.

for the source code and achieved high scalability for it on a cluster. We also achieved linear speedup for another application with a large number of independent threads. This paper discusses the architecture and implementation of the cluster VM. It focuses on achieving a single system image for a traditional JVM on a cluster while describing, in short, how we aim to obtain scalability. Copyright © 2001 John Wiley & Sons, Ltd.     

Task mapper and application-aware virtual machine scheduler oriented for parallel computing

We design a task mapper TPCM for assigning tasks to virtual machines, and an application-aware virtual machine scheduler TPCS oriented for parallel computing to achieve a high performance in virtual computing systems. To solve the problem of mapping tasks to virtual machines, a virtual machine mapping algorithm (VMMA) in TPCM is presented to achieve load balance in a cluster. Based on such mapping results, TPCS is constructed including three components: a middleware supporting an application-driven scheduling, a device driver in the guest OS kernel, and a virtual machine scheduling algorithm. These components are implemented in the user space, guest OS, and the CPU virtualization subsystem of the Xen hypervisor, respectively. In TPCS, the progress statuses of tasks are transmitted to the underlying kernel from the user space, thus enabling virtual machine scheduling policy to schedule based on the progress of tasks. This policy aims to exchange completion time of tasks for resource utilization. Experimental results show that TPCM can mine the parallelism among tasks to implement the mapping from tasks to virtual machines based on the relations among subtasks. The TPCS scheduler can complete the tasks in a shorter time than can Credit and other schedulers, because it uses task progress to ensure that the tasks in virtual machines complete simultaneously, thereby reducing the time spent in pending, synchronization, communication, and switching. Therefore, parallel tasks can collaborate with each other to achieve higher resource utilization and lower overheads. We conclude that the TPCS scheduler can overcome the shortcomings of present algorithms in perceiving the progress of tasks, making it better than schedulers currently used in parallel computing.     

Distributed virtual machine consolidation: A systematic mapping study

Background:Virtual Machine (VM) consolidation is an effective technique to improve resource utilization and reduce energy footprint in cloud data centers. It can be implemented in a centralized or a distributed fashion. Distributed VM consolidation approaches are currently gaining popularity because they are often more scalable than their centralized counterparts and they avoid a single point of failure.Objective:To present a comprehensive, unbiased overview of the state-of-the-art on distributed VM consolidation approaches.Method:A Systematic Mapping Study (SMS) of the existing distributed VM consolidation approaches.Results:19 papers on distributed VM consolidation categorized in a variety of ways. The results show that the existing distributed VM consolidation approaches use four types of algorithms, optimize a number of different objectives, and are often evaluated with experiments involving simulations.Conclusion:There is currently an increasing amount of interest on developing and evaluating novel distributed VM consolidation approaches. A number of research gaps exist where the focus of future research may be directed.     

基于Xen虚拟机的内存资源实时监控与按需调整

在虚拟计算环境中,难以实时地监控与分配内存资源。针对以上问题,基于Xen虚拟计算环境,提出一种能够实时监控Xen虚拟机内存(VMM)使用情况的XMMC方法并进行了实现。所提方法运用Xen虚拟机提供的超级调用,其不仅能实时地监控虚拟机内存使用情况,而且能实时动态按需分配虚拟机内存。实验结果表明,XMMC方法对虚拟机应用程序造成的性能损失很小,低于5%;能够对客户虚拟机的内存资源占用情况进行实时的监测与按需调整,为多虚拟机的管理提供方便。     

The application of ANFIS prediction models for thermal error compensation on CNC machine tools

Thermal errors can have significant effects on CNC machine tool accuracy. The errors come from thermal deformations of the machine elements caused by heat sources within the machine structure or from ambient temperature change. The effect of temperature can be reduced by error avoidance or numerical compensation. The performance of a thermal error compensation system essentially depends upon the accuracy and robustness of the thermal error model and its input measurements. This paper first reviews different methods of designing thermal error models, before concentrating on employing an adaptive neuro fuzzy inference system (ANFIS) to design two thermal prediction models: ANFIS by dividing the data space into rectangular sub-spaces (ANFIS-Grid model) and ANFIS by using the fuzzy c-means clustering method (ANFIS-FCM model). Grey system theory is used to obtain the influence ranking of all possible temperature sensors on the thermal response of the machine structure. All the influence weightings of the thermal sensors are clustered into groups using the fuzzy c-means (FCM) clustering method, the groups then being further reduced by correlation analysis.A study of a small CNC milling machine is used to provide training data for the proposed models and then to provide independent testing data sets. The results of the study show that the ANFIS-FCM model is superior in terms of the accuracy of its predictive ability with the benefit of fewer rules. The residual value of the proposed model is smaller than ±4 μm. This combined methodology can provide improved accuracy and robustness of a thermal error compensation system.     

A machine vision system for measuring wear and chipping of drilling tools

An automated measurement system for detection of drilling tool malfunctions such as wear and chipping has been developed for application to machining centres. A machine vision system with two industrial television cameras has been developed. A global image provided by the first camera is used to rotate the drill such that a major cutting edge is a central vertical line in each of the detailed images provided by the second camera. The second camera, with an autofocusing mechanism, focuses towards a potentially affected small region of the drill. Three detailed images are used for detection of drilling tool malfunctions, and failed portions are extracted using image-processing techniques. Three-dimensional surface contours of the failed portions along with one- and two-dimensional quantities such as wear width, chipping width, and the failed portion area are measured. Lighting directions are determined so that the diffusion component dominates specular reflection, and the failed portions are illuminated more than the normal portions.     

A method for managing green power of a virtual machine cluster in cloud

A green power management scheme is proposed to determine how many physical machines should be run or turned off based on the gross occupied resource weight ratio of the virtual machine cluster. The gross occupied resource weight ratio is defined as the ratio of the sum of resource weights of all virtual machines over the sum of available resource weights of all running physical machines. When the gross occupied resource weight ratio is greater than the maximum tolerant occupied resource weight ratio, preset to ensure quality of service, a standby physical machine in the non-running physical machines is selected and wakened up to join as one of the running physical machines. On the other hand, when the gross occupied resource weight ratio is less than the minimum critical occupied resource weight ratio, preset to trigger energy saving algorithms, one of the running physical machines, selected as a migration physical machine with the virtual machines therein removed after live migration, is moved from other running physical machines, and then turned off. As a result, a resource allocation process is realized to distribute loads of the running physical machines such that the total number of the running physical machines can be flexibly dispatched to achieve the objective of green power management.     

基于虚拟机技术的DCS仿真系统设计与实现

提出了基于虚拟机技术的DCS仿真系统的实现方式,描述了虚拟控制器的具体实现方法及虚拟机技术的其他应用.     

Combinatorial auction-based allocation of virtual machine instances in clouds

Most of the current cloud computing providers allocate virtual machine instances to their users through fixed-price allocation mechanisms. We argue that combinatorial auction-based allocation mechanisms are especially efficient over the fixed-price mechanisms since the virtual machine instances are assigned to users having the highest valuation. We formulate the problem of virtual machine allocation in clouds as a combinatorial auction problem and propose two mechanisms to solve it. The proposed mechanisms are extensions of two existing combinatorial auction mechanisms. We perform extensive simulation experiments to compare the two proposed combinatorial auction-based mechanisms with the currently used fixed-price allocation mechanism. Our experiments reveal that the combinatorial auction-based mechanisms can significantly improve the allocation efficiency while generating higher revenue for the cloud providers.     

虚拟数控加工过程物理仿真模型的建立

该文首先阐述了虚拟数控加工过程物理仿真的研究内容,其次重点讨论了所建立的切削力仿真,刀具磨损仿真与变形仿真,加工误差仿真,振动仿真和切屑形成过程仿真的数学模型。最后,提出了物理仿真今后研究的方向。     

利用虚拟机技术提高独立学院实验教学质量和科研水平

现阶段,在实验教学硬件设备要求较高而实验教学改革注重综合能力培养的指导下,很多依靠计算机硬件设备开展的实验课程遇到了较大的挑战.本文根据独立学院的具体情况结合虚拟机技术的特点,具体的分析了虚拟机技术在计算机实践教学中能起到的巨大作用和广阔的应用前景.并倡导全国独立院校要善于通过模拟真实的环境,去探索和研究科学的东西,提高自己的实践教学和科研水平.     

虚拟加工中心加工过程算法研究

在虚拟加工环境的建造过程中,关键技术是三维实体的数据结构和加工仿真的逐步成型算法。该文重点研究了毛坯的数据结构特点,四边形离散化方法和毛坯文件的存储格式等,并且分析了三坐标加工中心的加工特点,同时还给出了虚拟加工过程中毛坯被加工成工件的逐步成型算法。该算法在虚拟加工环境中得到了成功应用,文中给出了该算法在三坐标加工中心的验证实例。     

Holistic methodology using computer simulation for optimisation of machine tools

Virtual machine concepts supporting optimisation of machine tools have been developed in earlier work. The virtual machine concept is a tool that can describe the behaviour of a machine tool while considering the interaction between mechanics of the machines and the control system. Considerable amount of work has been done proving the concept and showing the potential of such a design tool in different contexts. Several studies have shown the potential of using the virtual machine concept, although, no work has been found that is exploring the potential of a full optimisation study.     

The kinematic analyses of the 3-DOF parallel machine tools

A 3-degree-of-freedom (3-DOF) parallel machine tool based on a tripod mechanism is developed and studied. The kinematics analysis is performed, the workspace is derived, and an analysis on the number of conditions of the Jacobian matrix and manipulability is carried out. A method for error analysis and manipulability is introduced. Hence, the manipulability analysis of the parallel machine tool is accomplished.     

Cousins Virtual Jane and Virtual Joe,extraordinary virtual helpers

Higher education institutions deliver web-based learning with varied success. The success rate of distributed online courses remains low. Factors such as ineffective course facilitation and insufficient communication contribute to the unfulfilled promises of web-based learning. Students consequently feel unmotivated. Instructor control and in the courseroom further isolates students, whereas success rate increases when students unite in virtual communities. King (2002) increased student participation in his online classes by creating a virtual student, Joe, as a participating student and supplementary facilitator. This investigation responds to King’s call for further directions on how a virtual helper enhances online facilitation. This inspired our investigation of how Virtual Jane might augment online facilitation. King’s prediction, “It seems that Joe Bags may have a family in the future,” (p. 164) became a reality in a South African masters’ web-based class on web-based learning.     

Agent virtual machine for automation controllers: Example application: Shipboard automation

We are interested in providing an agent infrastructure for truly distributed control. Requirements include multiple language implementations, so that this agent host environment can exist in both real-time controllers and contain the ability to operate with external agent systems. Our first infrastructure, the Autonomous Cooperative System (ACS), accomplished these goals, but presented other issues. Although ACS has been successfully deployed on commercial controllers, new releases of controllers will cause complications in the evolution of the software and adoption of future functionality. We need to establish a formal integration procedure of the agent functionality with the controllers and to transform the underlying system into a fully integrated and open heterogeneous system. We use a shipboard automation example to demonstrate the use of the agent virtual machine. With this system, the shipboard automation system is designed as a distributed and survivable environment, thereby spreading intelligence throughout the controllers and not in central locations.