基于循环迭代的飞机虚拟拆装过程建模方法

将循环迭代法应用于飞机虚拟拆装,研究飞机的拆装过程,提出一种基于循环迭代的虚拟拆装过程建模方法。结合飞机拆装过程动态循环的特性和虚拟人拆装行为并行相似的特点,建立虚拟人拆装行为参数化模型,规范虚拟人拆装行为的统一表达;在此基础上,分析虚拟人与部件的交互关系,构造虚拟人拆装行为、拆装次序、部件状态之间的迭代函数,建立虚拟拆装过程模型,实现虚拟人拆装行为的参数化描述和部件拆装过程的表达。以分布式虚拟维修训练平台中的集中故障显示接口组件拆装为例,对该方法进行仿真验证和比对,结果表明,以虚拟人拆装行为变化表示的部件状态变化使部件的拆装更易于表达,拆装训练效率有所提高。     

Development of a physically behaved robot work cell in virtual reality for task teaching

Robot task teaching on a real work cell is expensive and sometimes risky. This cost and risk can be avoided by using virtual reality technology. Using the simulated environment in virtual reality (VR), the operator can practise, explore and preview the operations for possible problems that might occur during implementation. It is therefore of practical importance to build the virtual robot work cell in VR that can facilitate the study of the performance of robotic tasks such as robotic assembly. This paper describes our work in incorporating physical behaviours of virtual objects into VR for robot task teaching. To facilitate the task teaching, we developed visual and audio cues which help visualise the dynamic interactions between virtual objects. Dynamic sensing capability is incorporated in the simulated environment. A simplified force sensor is modelled and simulated. The physical behaviours of the virtual objects are simulated using physics-based approach. A virtual robot work cell is built incorporating the developed features and an example for the task teaching is given. The implementation includes view tracking using virtual camera, visual and audio rendering, and the user interface developed in the VR. The current implementation was carried out on a PC-based VR platform, with the programs developed using Watcom C++.     

Virtual reality for assembly methods prototyping: a review

Assembly planning and evaluation is an important component of the product design process in which details about how parts of a new product will be put together are formalized. A well designed assembly process should take into account various factors such as optimum assembly time and sequence, tooling and fixture requirements, ergonomics, operator safety, and accessibility, among others. Existing computer-based tools to support virtual assembly either concentrate solely on representation of the geometry of parts and fixtures and evaluation of clearances and tolerances or use simulated human mannequins to approximate human interaction in the assembly process. Virtual reality technology has the potential to support integration of natural human motions into the computer aided assembly planning environment (Ritchie et al. in Proc I MECH E Part B J Eng 213(5):461–474, 1999). This would allow evaluations of an assembler’s ability to manipulate and assemble parts and result in reduced time and cost for product design. This paper provides a review of the research in virtual assembly and categorizes the different approaches. Finally, critical requirements and directions for future research are presented.     

A novel approach for determining fatigue resistances of different muscle groups in static cases

In ergonomics and biomechanics, muscle fatigue models based on maximum endurance time (MET) models are often used to integrate fatigue effect into ergonomic and biomechanical application. However, due to the empirical principle of those MET models, the disadvantages of this method are: 1) the MET models cannot reveal the muscle physiology background very well; 2) there is no general formation for those MET models to predict MET. In this paper, a theoretical MET model is extended from a simple muscle fatigue model with consideration of the external load and maximum voluntary contraction in passive static exertion cases. The universal availability of the extended MET model is analyzed in comparison to 24 existing empirical MET models. Using mathematical regression method, 21 of the 24 MET models have intraclass correlations over 0.9, which means the extended MET model could replace the existing MET models in a general and computationally efficient way. In addition, an important parameter, fatigability (or fatigue resistance) of different muscle groups, could be calculated via the mathematical regression approach. Its mean value and its standard deviation are useful for predicting MET values of a given population during static operations. The possible reasons influencing the fatigue resistance were classified and discussed, and it is still a very challenging work to find out the quantitative relationship between the fatigue resistance and the influencing factors.

Relevance to industry

MSD risks can be reduced by correct evaluation of static muscular work. Different muscle groups have different properties, and a generalized MET model is useful to simplify the fatigue analysis and fatigue modeling, especially for digital human techniques and virtual human simulation tools.     

基于KVM虚拟桌面的透明消息通道设计

云管理平台和虚拟机终端用户间的通信一般采用代理软件或插件,便捷性和抗干扰能力较低。针对该问题,利用基于内核的虚拟机(KVM)虚拟桌面,提出一种云服务提供节点(虚拟机所在物理主机)和虚拟机终端用户之间双向交互的透明消息通道设计方案。在云管理平台中建立消息控制端,用于接收和处理服务节点发往虚拟机终端用户的消息,并将消息转换为图像,使图像内容以位图像素数据格式的方式读出到特定文件中,作为消息发送模块的消息来源。通过修改KVM虚拟化平台中Qemu-KVM集成的VNC Server端源码,在源码中添加消息发送模块和反馈接收模块,将消息集成融入到虚拟机桌面图像中,并对VNC Client远程终端反馈的消息进行处理,从而得到一条对虚拟机自身系统透明的,可在云平台和终端用户间双向交互的消息通道。实验结果验证了该设计方案的可行性。     

面向装配工序交叉的虚拟装配工艺信息模型

虚拟装配工艺规划中目前大都采用装配顺序描述装配过程,但尚无法表达装配工序交叉和设计中的安装布置'捌整等问题.考虑设计阶段和制造阶段的装配要求,建立了基于装配任务的装配工艺信息模型.该模型以多层次的装配进程表达产品装配工艺过程,通过任务对象的交叉安装表达工序交叉和安装布置凋整,并给出了装配调整策略;针对冗余装配任务提出了装配任务合并方法.最后通过实例验证了文中模型的正确性和有效性.     

Robot-enabled tangible virtual assembly with coordinated midair object placement

The assembly in Virtual Reality (VR) enables users to fit virtual parts into existing 3D models immersively. However, users cannot physically feel the haptic feedback when connecting the parts with the virtual model. This work presents a robot-enabled tangible interface that dynamically moves a physical structure with a robotic arm to provide physical feedback for holding a handheld proxy in VR. This enables the system to provide force feedback during virtual assembly. The cooperation between the physical support and the handheld proxy produces realistic physical force feedback, providing a tangible experience for various virtual parts in virtual assembly scenarios. We developed a prototype system that allowed the operator to place a virtual part onto other models in VR by placing the proxy onto the matched structure attached to a robotic arm. We conducted a user evaluation to explore user performance and system usability in a virtual assembly task. The results indicated that the robot-enabled tangible support increased the task completion time but significantly improved the system usability and sense of presence with a more realistic haptic experience.     

A co-simulation framework for design of time-triggered automotive cyber physical systems

Designing cyber-physical systems (CPS) is challenging due to the tight interactions between software, network/platform, and physical components. Automotive control system is a typical CPS example and often designed based on a time-triggered paradigm. In this paper, a co-simulation framework that considers interacting CPS components for assisting time-triggered automotive CPS design is proposed. Virtual prototyping of automotive vehicles is the core of this framework, which uses SystemC to model the cyber components and integrates CarSim to model the vehicle dynamics. A network/platform model in SystemC forms the backbone of the virtual prototyping. The network/platform model consists of processing elements abstracted by real-time operating systems, communication systems, sensors, and actuators. The framework is also integrated with a model-based design tool to enable rapid prototyping. The framework is validated by comparing simulation results with the results from a hardware-in-the-loop automotive simulator. The framework is also used for design space exploration (DSE).     

Creation and evaluation of a multi-sensory virtual assembly environment

The multi-modal information presentation, integrated into the virtual environment （VE）, has potential for stimulating different senses, improving the user＇s impression of immersion, and increasing the amount of information that is accepted and processed by the user＇s perception system. The increase of the useful feedback information may reduce the user＇s cognitive load, thus enhancing the user＇s efficiency and performance while interacting with VEs. This paper presents our creation of a multi-sensory virtual assembly environment （VAE） and the evaluation of the effects of multi-sensory feedback on the usability. The VAE brings together complex technologies such as constraint-based assembly simulation, optical motion tracking technology, and real-time 3D sound generation technology around a virtual reality workbench and a common software platform. The usability evaluation is in terms of its three attributes： efficiency of use, user satisfaction, and reliability. These are addressed by using task completion times （TCTs）, questionnaires, and human performance error rates （HPERs）, respectively. Two assembly tasks have been used to perform the experiments, using sixteen participants. The outcomes showed that the multi-sensory feedback could improve the usability. They also indicated that the integrated feedback offered better usability than either feedback used in isolation. Most participants preferred the integrated feedback to either feedback （visual or auditory） or no feedback. The participants＇ comments demonstrated that nonrealistic or inappropriate feedback had negative effects on the usability, and easily made them feel frustrated. The possible reasons behind the outcomes are also analysed by using a unifying human computer interaction framework. The implications, concluded from the outcomes of this work, can serve as useful guidelines for improving VE system design and implementation.     

Analysis of assembly operations difficulty: a fuzzy expert system approach

Typical mechanical products can be assembled in various sequences of assembly operations. These sequences have high impact on the assembly time, machine utilization and even on the product quality. In order to select the best sequence of assembly operations, proper evaluation of the various sequences of assembly operations is required. This, in turn, requires the consistent evaluation of each assembly operation in the sequence. The assembly operations can be evaluated for various criteria, of which the operation difficulty is the most meaningful. This paper describes a methodology to analyse the assembly operations and calculates an operation's degree of difficulty using an expert system. This analysis consists of two steps: the first one identifies the main parameters that affect the assembly difficulty and assigns fuzzy triangular values to these parameters. The second step assigns weights to the parameters in order to maximize the agreement with a domain expert. The expert system analyses the difficulty of the assembly operation performed in two orientations: horizontal and vertical. The expert system then assigns a triangular fuzzy number as the aggregate measure of the operation's difficulty.     

基于软件定义网络的虚拟数据中心管理平台

针对已有虚拟数据中心（VDC）管理平台具有代码固化、后续升级困难等缺陷,设计和实现一种基于软件定义网络（SDN）的VDC管理平台。该平台由VDC管理子系统（VDCM）、VDC计算资源控制子系统（VDCCRC）和VDC网络资源控制子系统（VDCNRC）组成,子系统之间通过RESTful API交互建立起松耦合架构。VDCNRC通过SDN控制器管理数据中心网络资源,VDCCRC通过开源云平台管理数据中心计算资源,VDC管理子系统中内置VDC管理算法框架,可快速开发适用于实际生产环境的VDC管理算法。使用Mininet、Openstack、Floodlight搭建了测试环境,验证了该平台可通过Openstack来控制虚拟机的启动、迁移和删除,可通过Openflow控制器实现VDC网络带宽资源隔离,并支持VDC创建、删除和修改等操作。     

VDVAS：一个集成的虚拟设计与虚拟装配系统

随着虚拟现实技术的逐渐成熟，研究者们已将其引入到工程领域，为实现虚拟设计与虚拟装配过程的集成，避免现有的虚拟装配系统中，虚拟环境与CAD系统间所必需进行的复杂的、无谓的数据传输，描述了一个基于多通道的、集成的虚拟设计与虚拟装配系统VDVAS。在该系统中，设计得可以通过直接三维操作和语音命令直观方便地建立机械零件及其装配模型，并通过交互拆装来得到零件的装配顺序和装配路径等信息，VDVAS的一个重要特征在于，可通过集成虚拟设计与虚拟装配过程，使设计者能在一个集成的虚拟环境中修改零件几何（假如在装配过程中发现零件存在设计缺陷的话）。     

基于行车的Fusion虚拟装配系统的设计研究

核装置体积大、结构复杂、装配精度高,为降低该类型装置的装配风险,节约装配成本,提出了一个以面向PC平台、支持大型复杂装置装配规划、训练、演示为主要目标的基于行车的虚拟装配系统(FVAS).文中通过对三维场景交互、大模型实时碰撞检测、装配定位、装配过程记录、多视点漫游观察等虚拟装配主要技术环节的研究,利用面向对象的视景仿真开发包Open Inventor,结合VC 和商用CAD软件Unigraphics,实现了FVAS的原型设计.该系统成功仿真了我国即将运行的先进超导托克马克实验装置EAST的装配方案,并在先进的聚变驱动次临界堆FDS-I概念设计研究中得到应用.     

A framework using cluster-based hybrid network architecture for collaborative virtual surgery

Research on collaborative virtual environments (CVEs) opens the opportunity for simulating the cooperative work in surgical operations. It is however a challenging task to implement a high performance collaborative surgical simulation system because of the difficulty in maintaining state consistency with minimum network latencies, especially when sophisticated deformable models and haptics are involved. In this paper, an integrated framework using cluster-based hybrid network architecture is proposed to support collaborative virtual surgery. Multicast transmission is employed to transmit updated information among participants in order to reduce network latencies, while system consistency is maintained by an administrative server. Reliable multicast is implemented using distributed message acknowledgment based on cluster cooperation and sliding window technique. The robustness of the framework is guaranteed by the failure detection chain which enables smooth transition when participants join and leave the collaboration, including normal and involuntary leaving. Communication overhead is further reduced by implementing a number of management approaches such as computational policies and collaborative mechanisms. The feasibility of the proposed framework is demonstrated by successfully extending an existing standalone orthopedic surgery trainer into a collaborative simulation system. A series of experiments have been conducted to evaluate the system performance. The results demonstrate that the proposed framework is capable of supporting collaborative surgical simulation.     

集成环境下建筑内人员的疏散模拟

针对建筑内人员疏散的问题,提出集成模拟框架,确立面向计算机辅助设计(CAD)图纸的疏散效率评估流程.基于地理信息系统(GIS)技术,实时分析场景要素的空间分布特征,模拟人员对外部环境的认知与交互.应用虚拟现实(VR)技术对建筑布局及人员行为加以表现,基于Client-Server机制实现多视图集成.应用实例表明,CAD...     

Design,programming and orchestration of heterogeneous manufacturing systems through VR-powered remote collaboration

Modern manufacturing systems are often composed of a variety of highly customized units and specifically designed manufacturing cells. Optimization of assembly and training of staff requires a series of demo installations and excessive use of costly operational resources. In some cases, components are located at different sites, making the orchestration of the whole system even more difficult.Virtual Reality (VR) collaboration environments offer a solution by enabling high fidelity testing and training of complex manufacturing systems. On the other hand, such platforms are difficult to implement in an engineering perspective, as they are required to provide reliable, standard interfaces towards both robotic components and human operators.The VirCA (Virtual Collaboration Arena) platform is a software framework that supports various means of collaboration through the use of 3D augmented/virtual reality as a communication medium. VirCA offers functions for the high-level interoperability of heterogeneous components in a wide range of domains, spanning from research & development, through remote education to orchestration and management of industrial processes in manufacturing applications. This paper provides an overview of the industrial requirements behind high-fidelity virtual collaboration and demonstrates how the VirCA platform meets these requirements. Use cases are provided to illustrate the usability of the platform.     

Virtual user models for the elderly and disabled for automatic simulated accessibility and ergonomy evaluation of designs

This paper presents a framework for automatic simulated accessibility and ergonomy testing of virtual prototypes of products using virtual user models. The proposed virtual user modeling framework describes virtual humans focusing on the elderly and people with disabilities. Geometric, kinematic, physical, behavioral and cognitive aspects of the user affected by possible disabilities are examined, in order to create virtual user models able to represent people with various functional limitations. Hierarchical task and interaction models are introduced, in order to describe the user’s capabilities at multiple levels of abstraction. The use of alternative ways of a user task’s execution, exploiting different modalities and assistive devices, is supported by the proposed task analysis. Experimental results on the accessibility and ergonomy evaluation of different workplace designs for the use of a telephone and a stapler show how the proposed framework can be put into practice and demonstrate its significant potential.     

机构虚拟设计平台的研究与开发

以胶印机的机构设计为背景,提出了一个集成化的机构虚拟设计平台的体系结构,介绍了基于功能分解的机构概念设计,描述了构造装配模板实现概念模型与装配结构模型间的映射,并阐述了机构设计中的分析与评价等问题。     

A design flow for supporting component-based software development in multiprocessor real-time systems

Component-based software development established as an effective technique to cope with the increasing complexity of modern computing systems. In the context of real-time systems, the M-BROE framework has been recently proposed to efficiently support component-based development of real-time applications on multiprocessor platforms in the presence of shared resources. The framework relies on a two-stage approach where software components are first partitioned upon a virtual multiprocessor platform and are later integrated upon the physical platform by means of component interfaces that abstract from the internal details of the applications. This work presents a complete design flow for the M-BROE framework. Starting from a model of software components, a first method is proposed to partition applications to virtual processors and perform a synthesis of multiple component interfaces. Then, a second method is proposed to support the integration of the components by allocating virtual processors to physical processors. Both methods take resource sharing into account. Experimental results are also presented to evaluate the proposed methodology.