基于菲茨定律的虚拟现实任意形状选择模型

为了评估虚拟现实（VR）交互界面不同图形设计的点击效率，基于概率菲茨定律提出一种针对虚拟现实情境下指向性任务完成时间的预测方法，并构建了VR任意形状选择模型。首先，根据VR界面设计的实际需求，加入形状对指向性任务完成时间的影响，构建命中概率与任务难度指数的关系函数，将目标质心设为待积分函数的中心点，完成虚拟情境下概率菲茨模型定义。然后，设计实验一以获取改进概率菲茨模型中概率函数的常数项值；在此基础上设计实验二计算改进概率菲茨模型中预测函数的常数项，完成改进概率菲茨模型的构建。最后，以某VR烟草分拣系统实际点击任务对模型进行验证与评估，实验结果表明该模型能够在虚拟情境下对任务完成时间进行良好预测。     

基于VR技术的《人体解剖学》虚拟教学系统的设计与实现

基于虚拟现实（VR）技术从虚拟教学系统的功能需求、模块设计、三维人体解剖模型的导入及系统关键模块的开发细节等方面,详细阐述了整套虚拟教学系统的开发过程,完成了基于VR技术的《人体解剖学》虚拟教学系统的开发任务。该虚拟教学系统在PICO Neo3 VR一体机设备上成功安装与运行,经过测试达到了基本的设计要求。     

虚拟现实中手重映射的偏移检测阈值研究

针对虚拟现实交互（virtual reality interaction,VRI）中环境限制导致使用手的操作效率较低的问题,提出了虚拟现实中手重映射的固定偏移检测阈值估计方法以提高使用手的操作效率,该方法从人的心理感知出发,引入心理测量函数计算出偏移检测阈值从而提升交互体验。首先,根据双选择强制选择（two alternative forced choice,2AFC）理论设计实验,记录被试者使用不同偏移的虚拟手完成目标抓取任务过程中的感觉差异作为评价标准,同时记录被试者完成任务的时间,根据心理测量函数（Quickpsy）对感觉差异进行计算,估计重映射交互的检测阈值;通过协方差确定虚拟手偏移量超过阈值后的方向、幅度和轴向及其相互作用是影响触碰任务性能的显著因素,若在阈值范围内,上述因素就不再影响任务性能;最后,以某VR（virtual reality,虚拟现实）医院物资智能配送系统为例验证所提方法的可行性。研究结果表明,适当的偏移缩短了用户完成触碰任务的时间,能够在提升交互效率的同时降低传统偏移量计算方法对VR的交互保真度的影响。     

虚拟现实技术在柔性上肢康复机器人中的应用

根据末端牵引式和外骨骼式上肢康复机器人的特性,研制了一种新型的柔性上肢康复机器人。机器人的康复训练系统结合了主动和被动模式的要素,将虚拟现实（VR）技术引入上肢康复机器人,通过现实环境中的光学3D位置捕获以及VR环境中的3D位置感知,设计了虚拟动态模型交互性节点和碰撞检测实验,实现虚拟现实交互,提高虚拟模型运动实时效果和上肢康复训练精度。VR和新颖的康复机器人的集成为具有特定任务的患者提供了有效的训练。     

基于VR技术的中职学生心理健康训练系统设计

设计基于虚拟现实（Virtual Reality,VR）技术的中职学生心理健康训练系统,了解并调整学生心理健康状态。以影响中职学生心理健康的各种因素为基础组建评估指标体系,基于Logistic算法构建中职学生心理健康评估模型,并通过虚拟现实心理治疗（Virtual Reality Therapy,VRT）考试心理训练课程完成心理健康训练。实验结果表明,该方法能够缓解中职学生的考前焦虑。     

云计算环境下虚拟资源自适应调度策略

由于云计算环境下的资源调度与以往网格调度存在巨大差异,提出了一种适应云计算环境的虚拟资源调度方法;首先定义了虚拟资源调度数学模型,然后给出了一种改进的遗传算法,该算法采用经典网格任务调度算法Min-min获取初始最优解,通过海明距离约束产生初始种群,并将调度模型对应的目标函数改进为适应度函数,对交叉算子、变异算子、交叉概率和变异概率等都进行了改进;最后,通过实验证明文中方法能获得全局最早完成时间,与其它方法相比,文中方法所求解的最早完成时间提高了近20%,是一种适合云计算环境的虚拟资源调度方法。     

基于神经网络的焊缝形状预测模型

虚拟焊接作为虚拟现实（VR）的重要应用领域之一,主要应用在工业焊接培训领域,其在不断发展完善的过程中还存在着对焊接所形成的焊缝形状预测不够精确、焊缝形状预测算法时间复杂度大、预测结果渲染粗糙等问题,该文提出新的焊缝形状预测算法,不从物理学角度来分析焊接过程中具体的热量、电压、电流等参数对焊缝形状的影响,而是采用神经网络模型,通过Matlab编程训练得到预测焊缝形状的神经网络,用此神经网络来预测焊缝形状能有效提高焊缝形状预测的精度并避免因复杂物理建模而带来的算法时间复杂度大的问题。     

虚拟环境中面向装配设计的数据场景图研究

作为虚拟环境中的数据结构，场景图的构建是虚拟现实技术领域的重要研究问题之一。针对虚拟装配设计系统的要求，讨论现有商业VR软件在开发虚拟装配设计时存在的限制，提出一个基于场景图的多层次虚拟装配设计模型VAM．在现有VR软件和VAM的基础上，说明了虚拟装配设计时的路径规划、序列生成、零件之间的约束关系等的表示和应用。     

C2组织行动过程识别的概率推理模型

评估和识别敌方行动过程是未来分布式网络化指挥控制的一个新问题.以假设检验原理为基本原则,在任务计划、平台资源、任务状态形式化描述的基础上,对敌组织结构和行动过程进行分析.建立了任务状态影响模型和任务状态观测模型,设计了以任务状态后验概率最大为目标函数、最大似然估计确定任务的概率推理模型.针对概率推理模型特点,利用改进的快速模拟退火算法(VFSA)求解该模型.案例仿真结果表明,该模型能够有效识别敌方行动过程,退火算法能在有限时间内求解出当前状态下的敌最高概率行动.     

基于改进混沌萤火虫算法的云计算资源调度

为提高云计算资源的利用率,保持负载平衡,提出一种基于改进混沌萤火虫算法的云计算资源调度模型。从任务的完成时间、完成效率、完成安全性3个方面建立云计算资源调度模型,在萤火虫算法中引入混沌算法,通过对个体进行扰动,加快收敛速度,降低局部最优的概率,并引入拉格朗日松弛函数改进云计算模型。基于Cloudsim的仿真实验结果表明,该算法能有效避免资源分配的不均衡,缩短任务完成时间,提高系统的整体处理能力。     

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.     

Effects of displays on a direct reaching task: A comparative study of head mounted display and stereoscopic widescreen display

This study was conducted to investigate the virtual display effects on direct interaction performance metrics such as accuracy, task completion time, and comfort. Eighteen participants performed tapping (pointing) tasks in the coronal plane by directly reaching for tapping targets at three egocentric distance levels, with three indices of difficulty at each egocentric distance. The position data and severity of cybersickness symptoms were collected with a motion system and a symptom questionnaire, respectively. The results indicated that accuracy was higher with the stereoscopic widescreen display than with the head mounted display. However, no significant differences in task completion time, throughput, and cybersickness were observed between the two VR displays. In addition, increasing the egocentric distance improved accuracy and lengthened the task completion time, whereas increasing the task difficulty lengthened the task completion time but did not affect the accuracy. The findings are important and informative for users in choosing between the two virtual reality displays. Generally, the stereoscopic widescreen display can be recommended for tasks requiring high egocentric distance accuracy in the coronal plane. Furthermore, developers may refer to these findings in designing interfaces that allow a more natural way of interaction for users.     

The affect of contact force sensations on user performance in virtual assembly tasks

The development of a realistic virtual assembly environment is challenging because of the complexity of the physical processes and the limitation of available VR technology. Many research activities in this domain primarily focused on particular aspects of the assembly task such as the feasibility of assembly operations in terms of interference between the manipulated parts. The virtual assembly environment reported in this research is focused on mechanical part assembly. The approach presented addresses the problem of part-to-part contacts during the mating phase of assembly tasks. The system described calculates contact force sensations by making their intensity dependent on the depth of penetration. However the penetration is not visible to the user who sees a separate model, which does not intersect the mating part model. The two 3D models of the part, the off-screen rendered model and the on-screen rendered model are connected by a spring-dumper arrangement. The force calculated is felt by the operator through the haptic interface when parts come in contact during the mating phase of the assembly task. An evaluation study investigating the effect of contact force sensation on user performance during part-to-part interface was conducted. The results showed statistically significant effect of contact force sensation on user performance in terms of task completion time. The subjective evaluation based on feedback from users confirmed that contact force sensation is a useful cue for the operator to find the relative positions of components in the final assembly state.     

Improving virtual reality navigation tasks using a haptic vest and upper body tracking

Haptic feedback is an important component of immersive virtual reality (VR) applications that is often suggested to complement visual information through the sense of touch. This paper investigates the use of a haptic vest in navigation tasks. The haptic vest produces a repulsive vibrotactile feedback from nearby static virtual obstacles that augments the user spatial awareness. The tasks require the user to perform complex movements in a 3D cluttered virtual environment, like avoiding obstacles while walking backwards and pulling a virtual object. The experimental setup consists of a room-scale environment. Our approach is the first study where a haptic vest is tracked in real time using a motion capture device so that proximity-based haptic feedback can be conveyed according to the actual movement of the upper body of the user.User study experiments have been conducted with and without haptic feedback in virtual environments involving both normal and limited visibility conditions. A quantitative evaluation was carried out by measuring task completion time and error (collision) rate. Multiple haptic rendering techniques have also been tested. Results show that under limited visibility conditions proximity-based haptic feedback generated by a wearable haptic vest can significantly reduce the number of collisions with obstacles in the virtual environment.     

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++.     

基于威布尔分布的云计算能耗优化模型研究

针对云计算环境中复杂的虚拟机正常运行状态,提出将虚拟机运行看成由硬软件串联的可修复系统,用威布尔分布描述虚拟机硬软件正常运行的方法来建模缓解云计算高能耗问题。运用半马尔科夫过程刻画虚拟机运行过程、Laplace-Stielties变换简化数值计算、Bayesian定理去除限制条件,构建处理器利用率与能耗、性能的关系模型。再结合可修复系统寿命分布理论,调整虚拟机正常运行的威布尔分布函数,得到不同形状参数下处理器运行能耗以及给定任务完成时间,最终分析形状参数、处理器利用率与能耗-性能隐含关系并给出有效降低处理器运行能耗的合理化建议。数值分析表明：增大形状参数比提高利用率更显著降低处理器运行能耗;优化虚拟机配置使得形状参数变大,可以明显降低处理器运行能耗,同时避免云系统性能过度损耗。     

移动群智感知中基于联邦学习的参与者选择机制

移动群智感知的发展使得一些任务收集的数据量过大,需要在不接收参与者原始数据的情况下评估数据质量并进行参与者选择。针对这一问题,提出一种基于联邦学习的移动群智感知参与者选择机制。考虑参与者智能终端资源水平、所处交互状态构建参与者智能终端资源评价机制,提出基于线性回归和长短期记忆网络的智能终端资源预测模型。通过预训练测试模型,评估参与者提供的数据质量,结合历史任务完成情况建立参与者信誉评价模型,实现对参与者的动态评价选择。仿真实验结果表明,所提的参与者选择机制在任务完成质量、能量消耗、通信轮数及任务完成时间等多方面体现出较好的性能。     

三维交互界面中垂直多层交互技术的研究

目的:在Leap Motion硬件的垂直操作区域,通过手的不同高度来操作映射在屏幕上的多层离散的目标选择任务,得出适合用户操作的层数,以及相应的人因分析与讨论。方法:首先通过实验得出用户常用的垂直操作范围,再在常用范围的基础上进行分层实验,并且通过选择任务所花费的时间和任务困难度ID进行线性分析,证明是否适应Fitts’law模型。结果:通过实验发现,任务困难度对任务时间在全视觉反馈和半视觉反馈下的线性拟合度分别为0.766和0.771,所以Fitts’law模型对于分层交互界面下的多层离散的目标选择任务并不适用,并且通过时间和错误率的相关数据分析得出了在全视觉反馈和半视觉反馈下的用户可操作的最大可分层数分别为20层和18层,本文结论可为基于多层的三维界面的应用场景的技术设计提供必要的设计准则。     

基于双层规划的容器云资源动态配置算法

本文分析容器云资源动态配置决策问题,通过定义容器云资源的调度任务,求解得到容器云资源调度时间;利用容器云资源调度任务的最短时间矩阵,获取容器云资源调度所需的条件。在双层规划条件下,求解容器云资源调度的目标函数和约束函数;考虑到用户的任务情况和云数据中心的云资源状况,在虚拟机上构建一个到物理主机的矩阵,通过构建容器云资源动态配置结果在优化时的目标函数,结合约束条件,实现容器云资源的动态配置。实验结果表明,资源动态配置算法不仅可以提高容器云资源的利用率,还可以减少配置完成时间,具有更好的动态配置性能。