基于虚拟样机的起重机小车碰撞仿真试验

以某20 t门式起重机小车为研究对象,利用Adams建立门式起重机小车的虚拟样机模型,并对其进行危险工况下碰撞仿真试验,获得该小车受力变化、运行状况等数据,分析其整体安全性能.形成的分析方法既可验证起重机小车设计的合理性,也可为其倾翻事故的鉴定与分析提供有效的技术支持.     

A multi-material virtual prototyping system

This paper proposes a multi-material virtual prototyping system for digital fabrication of heterogeneous prototypes. It consists mainly of a topological hierarchy-sorting algorithm for processing slice contours, and a virtual simulation system for visualisation and optimisation of multi-material layered manufacturing (MMLM) processes. The topological hierarchy-sorting algorithm processes the hierarchy relationship of complex slice contours. It builds a parent-and-child list that defines the containment relationship of the slice contours, and subsequently arranges the contours in an appropriate sequence, which facilitates toolpath planning for MMLM by avoiding redundant tool movements. The virtual simulation system simulates MMLM processes and provides stereoscopic visualisation of the resulting multi-material prototypes for quality analysis and optimisation of the processes.     

虚拟样机仿真标准化技术研究

虚拟样机标准化技术是实现大型复杂虚拟样机系统集成的根本前提,提出了虚拟样机仿真标准的制定原则,研究了虚拟样机仿真标准的主要内容,包括信息建模标准、信息交换标准、信息处理标准、信息安全标准、信息传输标准及人机界面标准等,虚拟样机标准化的研究可为虚拟样机技术的实现及进一步的应用研究提供基础。     

Modeling and real-time simulation architectures for virtual prototyping of off-road vehicles

Virtual Reality-based simulation technology has evolved as a useful design and analysis tool at an early stage in the design for evaluating performance of human-operated agricultural and construction machinery. Detecting anomalies in the design prior to building physical prototypes and expensive testing leads to significant cost savings. The efficacy of such simulation technology depends on how realistically the simulation mimics the real-life operation of the machinery. It is therefore necessary to achieve ‘real-time’ dynamic simulation of such machines with operator-in-the-loop functionality. Such simulation often leads to intensive computational burdens. A distributed architecture was developed for off-road vehicle dynamic models and 3D graphics visualization to distribute the overall computational load of the system across multiple computational platforms. Multi-rate model simulation was also used to simulate various system dynamics with different integration time steps, so that the computational power can be distributed more intelligently. This architecture consisted of three major components: a dynamic model simulator, a virtual reality simulator for 3D graphics, and an interface to the controller and input hardware devices. Several off-road vehicle dynamics models were developed with varying degrees of fidelity, as well as automatic guidance controller models and a controller area network interface to embedded controllers and user input devices. The simulation architecture reduced the computational load to an individual machine and increased the real-time simulation capability with complex off-road vehicle system models and controllers. This architecture provides an environment to test virtual prototypes of the vehicle systems in real-time and the opportunity to test the functionality of newly developed controller software and hardware.     

A virtual prototyping system for rapid product development

This paper describes a virtual prototyping (VP) system that integrates virtual reality with rapid prototyping (RP) to create virtual or digital prototypes to facilitate product development. The proposed VP system incorporates two new simulation methodologies, namely the dexel-based and the layer-based fabrication approaches, to simulate the powder-based and the laminated sheet-based RP processes, respectively. The dexel-based approach deposits arrays of solid strips to form a layer, while the layer-based approach directly forms a complete layer by extruding the slice contours. The layer is subsequently stacked up to fabricate a virtual prototype. The simulation approaches resemble the physical fabrication processes of most RP systems, and are therefore capable of accurately representing the geometrical characteristics of prototypes. In addition to numerical quantification of the simulation results, the system also provides stereoscopic visualisation of the product design and its prototype for detailed analyses. Indeed, the original product design may be superimposed on its virtual prototype, so that areas with dimensional errors beyond design limits may be clearly highlighted to facilitate point-to-point analysis of the surface texture and the dimensional accuracy of the prototype. Hence, the key control parameters of an RP process, such as part orientation, layer thickness and hatch space, may be effectively tuned up for optimal fabrication of physical prototypes in subsequent product development. Furthermore, the virtual prototypes can be transmitted via the Internet to customers to facilitate global manufacturing. As a result, both the lead-time and the product development costs can be significantly reduced.     

A virtual prototyping system with reconfigurable actuators for multi-material layered manufacturing

Proliferation of layered manufacturing (LM) in various sectors has been calling for fabrication of large, complex products with more materials and efficiency. We address this issue by integrating reconfigurable manufacturing (RM) with LM. This paper first analyses the benefits of such integration, and then presents a virtual prototyping system with reconfigurable actuators (VPRA) that can increase the number of materials, speed, and build volume to improve the efficiency and flexibility of multi-material layered manufacturing (MMLM). The VPRA system offers a test bed for design, visualization, and validation of MMLM facilities and processes. It takes advantage of the convenient graphics platform of SolidWorks™ for constructing a virtual MMLM facility by selecting reconfigurable actuators from predefined templates. The characteristics, including the dimensions and relative spatial constraints, of the actuators can be conveniently configured to suit design requirements. The mechanism and the operation process of the resulting MMLM facility can then be simulated and validated through digital fabrication of complex objects. Case studies are presented to demonstrate some possible applications of the VPRA system. Overall, the VPRA system gives insights into the characteristics of a reconfigurable MMLM system, which can be subsequently materialized for physical fabrication of multi-material objects. This approach highlights a possible direction for development of MMLM technology.     

A versatile virtual prototyping system for rapid product development

This paper presents a versatile virtual prototyping (VP) system for digital fabrication of multi-material prototypes to facilitate rapid product development. The VP system comprises a suite of software packages for multi-material layered manufacturing (MMLM) processes, including multi-toolpath planning, build-time estimation and accuracy analysis, integrated with semi-immersive desktop-based and full-immersive CAVE-based virtual reality (VR) technology. Such versatility makes the VP system adaptable to suit specific cost and functionality requirements of various applications.

The desktop-based VR system creates a semi-immersive environment for stereoscopic visualisation and quality analysis of a product design. It is relatively cost-effective and easy to operate, but its users may be distracted by environmental disturbances that could possibly diminish their efficiency of product design evaluation and improvement. To alleviate disturbance problems, the CAVE-based VR system provides an enclosed room-like environment that blocks out most disturbances, making it possible for a design team to fully concentrate and collaborate on their product design work.

The VP system enhances collaboration and communication of a design team working on product development. It provides simulation techniques to analyse and improve the design of a product and its fabrication processes. Through simulations, assessment and modification of a product design can be iterated without much worry about the manufacturing and material costs of prototypes. Hence, key factors such as product shape, manufacturability, and durability that affect the profitability of manufactured products are optimised quickly. Moreover, the resulting product design can be sent via the Internet to customers for comments or marketing purposes. The VP system therefore facilitates advanced product design and helps reduce development time and cost considerably.     

纸面原型设计方法在虚拟仿真系统开发的应用

如果在软件产品的开发过程中试图给用户提供原型进行测试,不但困难而且成本巨大.针对该问题,采用纸面原型设计方法,从使用者的角度,分析了虚拟漫游仿真系统导向标识开发过程中"中间工作产品"的问题,并利用纸面原型进行有用户参与的测试.对用户的反馈意见和测试结果进行了分析,对导向标识进行了相应的改进,有效地指导了虚拟漫游仿真系统导向标识的开发.结果表明,在软件产品过程中,纸面原型方法是节省开发时间、节约开发成本的有效方法.     

基于虚拟现实技术的移动机器人视觉伺服控制系统设计

为了有效确保移动机器人视觉伺服控制效果,提高移动机器人视觉伺服控制精度,设计了基于虚拟现实技术的移动机器人视觉伺服控制系统。通过三维视觉传感器和立体显示器等虚拟环境的I/O设备、位姿传感器、视觉图像处理器以及伺服控制器元件,完成系统硬件设计。从运动学和动力学两个方面,搭建移动机器人数学模型,利用标定的视觉相机,生成移动机器人实时视觉图像,通过图像滤波、畸变校正等步骤,完成图像的预处理。利用视觉图像,构建移动机器人虚拟移动环境。在虚拟现实技术下,通过目标定位、路线生成、碰撞检测、路线调整等步骤,规划移动机器人行动路线,通过控制量的计算,实现视觉伺服控制功能。系统测试结果表明,所设计控制系统的位置控制误差较小,姿态角和移动速度控制误差仅为0.05°和0.12m/s,移动机器人碰撞次数较少,具有较好的移动机器人视觉伺服控制效果,能够有效提高移动机器人视觉伺服控制精度。     

A cooperative virtual prototyping system for mechatronic solution elements based assembly

In order to catch up with the steps of rapidly changing markets, the product development period of modern mechatronic products has to be as short as possible. However, mechatronic engineering is based on the interaction of mechanical engineering, electronic engineering, and computer science. Therefore, inefficient communication between the engineers who come from different domains becomes a manifest obstruction for accelerating the design of mechatronic products. Nevertheless, innovations in the field of virtual prototyping offer some potential solutions to this problem. In this paper, we present a cooperative virtual prototyping system, which utilizes the concept of solution elements and virtual reality techniques to facilitate assembling and analyzing virtual mechatronic prototypes in a multi-disciplinary workgroup.     

基于虚拟机技术的高性能手机游戏平台

介绍了基于虚拟机的高性能手机游戏平台vGame的架构,以及运行于J2ME环境的虚拟机vMachine和基于Python语法的高效动态脚本vScript,给出了vMachine和vScript的设计原理和实现方案.     

基于移动Agent技术的虚拟企业协调机制

虚拟企业由于需要具备对市场机遇的快速反应能力以及企业间的协作能力,必然需要与信息技术紧密联合,同时对系统架构的柔性和可扩展性提出了很高的要求。提出了一种基于移动Agent技术的虚拟企业协调机制,并通过基于XML的工作流技术保证了业务流程的灵活性和可扩展性,给出了使用Java反射机制的工作流引擎的实现机制。并进一步通过结盟、变更移动A-gent和监控移动Agent的具体实现,介绍了该机制下工作流的应用以及在Aglet移动开发环境下主从模式的开发。     

Five-axis pencil-cut planning and virtual prototyping with 5-DOF haptic interface

In this paper, techniques of 5-axis pencil-cut machining planning with a 5-DOF (degree of freedom) output haptic interface are presented. Detailed techniques of haptic rendering and tool interference avoidance are discussed for haptic-aided 5-axis pencil-cut tool path generation. Five-axis tool path planning has attracted great attention in CAD/CAM and NC machining. For efficient machining of complex surfaces, pencil-cut uses relatively smaller tools to remove the remaining material at corners or highly curved regions that are inaccessible with larger tools. As a critical problem for 5-axis pencil-cut tool path planning, the tasks of tool orientation determination and tool collision avoidance are achieved with a developed 5-DOF haptic interface. A Two-phase rendering approach is proposed for haptic rendering and force-torque feedback calculation with haptic interface. A Dexel-based volume modeling method is developed for global tool interference avoidance with surrounding components in a 5-axis machining environment. Hardware and software implementation of the haptic pencil-cut system with practical examples are also presented in this paper. The presented technique can be used for CAD/CAM, 5-axis machining planning and virtual prototyping.     

Collaborative virtual prototyping of product assemblies over the Internet

Product assembly design is a complex activity involving collaboration between several designers. Currently, many manufacturing firms out source the design and development of different portions of a product to different suppliers. Due to the absence of an integrated tool for collaborative product assembly design, designers currently follow an indirect approach. This makes collaboration an unorganized and inefficient activity. This paper discusses the architectural novelties and design considerations utilized to develop an integrated collaborative assembly design tool. Further, the scenarios of using such a tool are discussed in detail. This discussion highlights how the tool contributes towards making collaboration an organized and efficient activity and enables designers to rapidly design and prototype the product assembly.     

安全增强型虚拟磁盘加密系统技术

应用文件系统过滤驱动技术,结合审计、防U盘扩散、防缓存泄漏方法,对现阶段流行的虚拟磁盘加密软件的透明加解密方案进行改进,在其虚拟驱动层上增加了旨在提升整体安全性能的文件系统过滤驱动层(下面称之为安全层).针对开源的truecrypt进行测试,结果表明,在Windows各版本操作系统下,对虚拟磁盘加密软件上加入安全层以后,解决了U盘扩散、虚拟磁盘卸载之后缓存泄漏等安全问题,实现了对用户操作的审计监控,能有效增强虚拟磁盘加密软件的安全性能.     

通信系统融合虚拟仿真技术实现

随着时代的发展,科技的发展,尤其是信息科技的飞速发展,促使我们的教学也要"与时俱进",不断满足国家和社会对通信人才的需要.因此在这样时代背景下,就需要我们改进教学,适应社会的需要.     

虚拟人足球比赛阵法的系统建模与仿真

足球比赛阵法是进行足球比赛关键的部分,阵法应用的合适与否直接影响球队的成绩。文章首先对虚拟人足球进行了简要介绍,然后根据足球运动的特点,在机器人足球比赛仿真研究理论的基础上,对阵法仿真系统建模进行探索性研究,给出了阵法仿真系统层次结构模型,并对模型各部分做了分析,引入了亲密度矩阵（ADM）,加强了球员进攻防守协作的力度,显著提高了球队的整体进攻防守性能,最后对433阵型下的阵法进行了实验仿真,实验结果表明方法的可行性。     

汽车刚弹声耦合动力系统建模与控制

为解决汽车噪声问题,首先采用包含线性和非线性连接子结构的自由界面模态综合法,建立副车架橡胶支承控制前后的整车随机动力学模型;然后在时域内对汽车控制前的动力学模型进行仿真模拟,并与台架试验结果进行对比,发现两者具有较好的一致性,说明所建模型是有效的;最后将副车架橡胶支承作为无源控制元件,应用准最优控制理论对在路面随机载荷和发动机载荷作用下汽车振动和车内噪声特性进行研究,并与未加控制和理想最优控制时的响应结果进行对比,结果表明用准最优控制理论进行整车减振降噪具有很好的综合效果.该结果可为不同控制方法的选取提供理论依据.     

Web服务、移动Agent及工作流技术在组建动态联盟中的应用

动态联盟的目标是可重构、软件重用和规模可变。基于XML的Web Service(WS)技术,由于其平台中性、松散耦合以及智能的服务发现机制成为企业间应用集成有效解决方案,同时将企业现有应用以Web服务形式包装可以更好支持实现动态联盟的三个目标。鉴于此,以WS技术为基础,结合工作流和移动Agent技术,从理论上提出组建动态联盟系统框架的方案。