手术仿真中基于导纳控制的力触觉形变模型

为了在虚拟手术仿真中获得快速、准确的力触觉形变效果,提出一种基于导纳控制的力触觉形变模型.基于该模型,采用PHANTOM OMNI力触觉交互设备,以3DS MAX 2013,Microsoft Visual C++2012,Open GL函数库为基础搭建了实时柔性体力触觉再现系统,实现了虚拟双手对心脏双点的拉拽交互操作.感知实验和交互效率的结果表明,所提出的模型简单有效,形变效果逼真、视觉反馈流畅、力触觉反馈平稳,操作者对虚拟环境的感知和交互准确可靠,能够满足虚拟手术仿真系统的要求.     

高度复杂拟凸体的实时触觉绘制

触觉绘制目前已成为虚拟现实的研究热点之一,其核心是触觉代理与目标物体的实时碰撞检测与距离计算,对高度复杂模型的触觉绘制仍然是虚拟现实领域的难题,原因是对模型复杂度敏感的算法均不能满足触觉绘制苛刻的时间要求.提出触觉包围盒概念,并针对拟凸体提出一种基于触觉包围盒的实时触觉绘制算法.触觉包围盒记录了离散的采样光线与目标物体的相交信息,进行触觉计算时,只需要执行1次线段与包围盒求交运算和5次双线性插值运算即可高速求出碰撞信息,且所得到的碰撞信息可直接用于反馈力计算.实验结果表明,该算法不仅快速有效,而且具有与触觉绘制模型复杂度不相关的优点.     

双触点交互的力触觉实时生成方法

力触觉的生成和交互有助于提升虚拟环境的沉浸感和真实性.提出了一种双触点交互的力触觉实时生成方法.把双触点交互分为4种状态,分别提出不同状态下双触点交互的力触觉实时生成算法,并建立虚双触点交互的实验环境,开展双触点交互力触觉生成的评价研究.实验结果表明,该方法能够实时生成双触点交互时的力触觉,增强虚拟环境的沉浸感和真实性,提升了人手力触觉交互的自然性.     

虚拟柔性体实时形变仿真模型研究

为了在虚拟现实柔性体力触觉交互研究中得到稳定、连续、真实的力触感,提出一种基于球面调和函数表达的虚拟柔性体实时形变仿真模型,利用球面调和函数的正交归一、旋转不变、多尺度等特性实现物体的快速准确表达.在变形体的密度、杨氏模量、泊松比等参数已知的情况下,基于径向基函数神经网络模型预测柔性体受力形变后的SH模型.仿真结果表明,该方法不仅可以准确表达柔性体的实时形变,而且使得基于SH表达的柔性体形变的视觉刷新描述与柔性体反馈力的触觉刷新描述同步,从而满足虚拟手术仿真训练等虚拟柔性体力触觉交互研究要求.     

用于实时柔性触觉再现的平行菱形链连接模型

精度高且实时性好的柔性触觉变形模型是实现触觉再现系统的关键。提出了一种新的基于物理意义的平行菱形链连接触觉变形模型,系统中各个链结构单元相对位移的叠加对外等效为物体表面的变形,与之相连的弹簧弹性力的合力等效为物体表面的接触力。使用Delta 6-DOF手控器,建立了触觉再现实验系统,对柔性体的接触变形和实时虚拟触觉反馈进行仿真, 实验结果表明所提出的模型不仅计算简单,而且能够保证触觉接触力和形变计算具有较高精度,满足虚拟现实系统对精细作业和实时性的要求。     

柔性体力触觉形变模型研究

针对虚拟现实力触觉交互中柔性体受力与形变的复杂关系,提出一种基于球面调和函数(SphericalHarmonic,SPHARM))的柔性体力触觉仿真模型。利用SPHARM的正交归一、旋转不变、多尺度等特性完成柔性体几何模型的准确表达;将柔性体在不同作用力下的形变模型映射到共同的参照系统中,在共同的参照系统中,利用主成分分析方法(Principal Components Analysis,PCA)完成柔性体在不同作用力下的形变比较,根据简化后的波动方程计算物体形变后的反馈力。实验结果表明,该方法可以准确表达柔性体的形变过程,适用于柔性体力触觉实时交互研究。     

实现牙体预备触觉交互仿真的图形显示

介绍了在牙科手术训练触觉交互系统的虚拟手术环境中,通过材料去除速率控制构成牙齿的网格变形实现牙齿被切削时材料去除过程的图形仿真.针对牙体预备操作和触觉交互装置输出力的特点,在交互系统的虚拟环境中,当工具与牙体模型发生接触时,所有进入工具空间范围的顶点都会沿着其外法线的反方向进行投射,投射量受控于材料去除速度,且网格变形速度不超过真实的牙齿材料去除速度,同时针对网格的变形位置绘制虚拟工具.通过限制网格变形可以动态的实现牙齿被切削过程的形状变化,图形显示逼真同时没有滞后.     

带有振动触觉反馈的上肢康复系统

康复机器人在脑卒中患者的术后恢复治疗中起着重要作用。为了提高患者在康复训练过程中的主动性和专注度,提出了一种带有振动反馈的上肢康复训练系统。该系统利用多传感器获取人的上肢位姿信息,实现与虚拟场景的实时交互,并通过实时多层级振动反馈引导人的康复动作。通过心理物理学实验评估受试者对不同振动强度的感受,得出了人体感受区分明显的3个振动强度等级。构建了视触觉有效性实验,受试者需要在虚拟场景中完成特定的康复动作,实验结果表明,相较于无触觉反馈,受试者在振动触觉反馈的作用下可以更稳定高效地完成康复任务。     

虚拟手术中的模型实时绘制

实时的视觉反馈在虚拟手术中可以加强操作者的沉浸感。该文分析了体绘制和面绘制的优缺点,在系统实时性的要求下,实现了基于立体纹理映射的三维体模型的面绘制。算法在容许实时交互的同时,为操作者提供了真实感较强的视觉反馈。由于文中立体纹理生成及纹理坐标计算的特殊性,对虚拟手术中的拉压变形和切割等操作也能很好地处理。     

实时多组织虚拟手术的反馈力模拟

为了在虚拟下颌整形手术系统中提供实时和真实的触觉交互,分别构建了基于虚拟中介平面的推操作触觉模型、基于粘附力的拉操作触觉模型和基于非线性粘弹性的针刺触觉模型,以模拟皮肤拉钩、整形镊和针的典型手术操作;同时通过相邻组织间的动态触觉约束建立了多组织联合形变模型,以避免表面弹簧-质点模型形变过程中可能出现的表面间相互穿透的异常现象;并进一步将触觉交互模型和多组织形变模型集成于虚拟下颌手术系统,从而为医生提供一个手术训练的虚拟平台.触觉感知和交互效率的实验结果表明,通过触觉交互识别皮肤、肌肉和骨骼能够获得较高的识别正确率,并能提供实时的触觉和视觉交互体验.     

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.     

视触觉融合的增强现实三维注册方法

增强现实技术是近年来人机交互领域的研究热点。在增强现实环境下加入触觉感知,可使用户在真实场景中看到并感知到虚拟对象。为了实现增强现实环境下与虚拟对象之间更加自然的交互,提出一种视触觉融合的三维注册方法。基于图像视觉技术获得三维注册矩阵;借助空间转换关系求解出触觉空间与图像空间的转换关系;结合两者与摄像头空间的关系实现视触觉融合的增强现实交互场景。为验证该方法的有效性,设计了一个基于视触觉增强现实的组装机器人项目。用户可触摸并移动真实环境中的机器人零件,还能在触摸时感受到反馈力,使交互更具真实感。     

A virtual reality keyboard with realistic haptic feedback in a fully immersive virtual environment

This study presents a 3D virtual reality (VR) keyboard system with realistic haptic feedback. The system uses two five-fingered data gloves to track finger positions and postures, uses micro-speakers to create simulated vibrations, and uses a head-mounted display (HMD) for 3D display. When users press a virtual key in the VR environment, the system can provide realistic simulated key click haptic feedback to users. The results of this study show that the advantages of the haptic VR keyboard are that users can use it when wearing HMDs (users do not need to remove HMDs to use the VR keyboard), the haptic VR keyboard can pop-up display at any location in the VR environments (users do not need to go to a specific location to use an actual physical keyboard), and the haptic VR keyboard can be used to provide realistic key click haptic feedback (which other studies have shown enhances user performance). The results also show that the haptic VR keyboard system can be used to create complex vibrations that simulate measured vibrations from a real keyboard and enhance keyboard interaction in a fully immersive VR environment.     

Haptic Direct-Drive Robot Control Scheme in Virtual Reality

This paper explores the use of a 2-D (Direct-Drive Arm) manipulator for mechanism design applications based on virtual reality (VR). This article reviews the system include a user interface, a simulator, and a robot control scheme. The user interface is a combination of a virtual clay environment and human arm dynamics via robot effector handler. The model of the VR system is built based on a haptic interface device behavior that enables the operator to feel the actual force feedback from the virtual environment just as s/he would from the real environment. A primary stabilizing controller is used to develop a haptic interface device where realistic simulations of the dynamic interaction forces between a human operator and the simulated virtual object/mechanism are required. The stability and performance of the system are studied and analyzed based on the Nyquist stability criterion. Experiments on cutting virtual clay are used to validate the theoretical developments. It was shown that the experimental and theoretical results are in good agreement and that the designed controller is robust to constrained/unconstrained environment.     

虚拟现实的力触觉交互技术发展现状与趋势

虚拟现实通过模拟人的视觉、听觉、力触觉等,使人处于一种与真实世界非常逼真的虚拟世界中,来感受、体验和评价虚拟世界中的场景和设备。力触觉在虚拟现实环境中有其突出优越性,力触觉使得虚拟现实环境变得真实,是唯一的既可接受周围环境输入又可以对周围环境输出的感知通道,可极大增强可视化表达的效果。虚拟现实的力触觉交互技术包括力触觉再现技术和虚拟环境的力触觉建模。介绍了这两方面的发展现状、存在的问题和今后的发展趋势。     

Touch-enabled haptic modeling of deformable multi-resolution surfaces

Currently, interactive data exploration in virtual environments is mainly focused on vision-based and non-contact sensory channels such as visual/auditory displays. The lack of tactile sensation in virtual environments removes an important source of information to be delivered to the users. In this paper, we propose the touch-enabled haptic modeling of deformable multi-resolution surfaces in real time. The 6-DOF haptic manipulation is based on a dynamic model of Loop surfaces, where the dynamic parameters are computed easily without subdividing the control mesh recursively. A local deforming scheme is developed to approximate the solution of the dynamics equations, thus the order of the linear equations is reduced greatly. During each of the haptic interaction loop, the contact point is traced and reflected to the rendering of updated graphics and haptics. The sense of touch against the deforming surface is calculated according to the surface properties and the damping-spring force profile. Our haptic system supports the dynamic modeling of deformable Loop surfaces intuitively through the touch-enabled interactive manipulation.     

Networked multiplayer cooperative interaction using decoupled motion control method in a shared virtual environment with haptic,visual and movement feedback

This paper focuses on multiplayer cooperative interaction in a shared haptic environment based on a local area network. Decoupled motion control, which allows one user to manipulate a haptic interface to control only one‐dimensional movement of an avatar, is presented as a new type haptic‐based cooperation among multiple users. Users respectively move an avatar along one coordinate axis so that the motion of the avatar is the synthesis of movements along all axes. It is different from previous haptic cooperation where all users can apply forces on an avatar along any direction to move it, the motion of which completely depends on the resultant force. A novel concept of movement feedback is put forward where one user can sense other users’ hand motions through his or her own haptic interface. The concept can also be explained wherein one person who is required to move a virtual object along only one axis can also feel the motions of the virtual object along other axes. Movement feedback, which is a feeling of motion, differs from force feedback, such as gravity, collision force and resistance. A spring‐damper force model is proposed for the computation of motion feedback to implement movement transmission among users through haptic devices. Experimental results validate that movement feedback is beneficial for performance enhancement of such kind of haptic‐based cooperation, and the effect of movement feedback in performance improvement is also evaluated by all subjects.Copyright © 2012 John Wiley & Sons, Ltd.     

The moderating role of sensation seeking tendency in robotic haptic interfaces

This study examined the interaction effects between haptic force feedback and users’ sensation seeking tendency (i.e. need for sensations) on users’ feelings of presence (i.e. the state in which users experience virtual objects and virtual environments as if they were actual) in robotic haptic interfaces. Users with low sensation seeking tendency felt stronger physical presence and spatial presence in response to force feedback haptic stimuli (versus no force feedback), whereas users with high sensation seeking tendency did not show any difference between the two conditions, thus confirming the moderating role of the users’ sensation seeking tendency in the robotic haptic interface. Theoretical implications for human–computer interaction (HCI) research and managerial implications for the interactive media market are discussed.     

引入力触觉的数字文物多模交互方法

目的 针对当前文物资源由传统的实体文物向虚拟展示和数字文物进行扩展的趋势,如何提供一种多模态的信息呈现方式就显得尤为重要。通过将力触觉技术引入3维文物展示领域,提出一种基于多模感知的3维文物交互式呈现的算法框架。在对文物的基本特征进行视、听、触觉多通道分析的基础上,依据用户与文物模型的接触状态对多通道信息进行计算和整合。方法 在力触觉计算渲染方面,基于嵌入深度构建弹簧系统模拟轮廓形状的接触过程,引入动摩擦和静摩擦因数来反映表面摩擦力这一材质特征,通过法线贴图来实现文物表面纹理的触觉处理;针对交互的环境由2维平面拓展至立体空间,结合力触觉设备将操作时的行为和状态映射为虚拟环境中的操作代理,借助操作代理构建"旋转"和"选择-移动-释放"两种基本的操作范式来实现用户意图;最后,物理引擎的引入将物体的基本运动规律集成至虚拟场景,提升场景交互的真实感.结果 使用Phantom Omni手控器搭建面向馆藏文物的多模感知实验系统,抽取志愿者对实验系统进行测评。实验结果表明：运用本文方法,用户可从视觉、听觉、触觉多个通道对数字文物的整体和细节信息进行感知,且交互的整体过程简单、自然、有效。结论 本文提出的基于多模感知的数字文物交互式呈现方法,可有效实现对各类数字遗产特别是3维文物的多模重现,在保证较高实时性的同时拥有良好的可用性和情感体验效果。     

Proposal of an Index for the Operator’s Haptic Sensation in a Master-Slave System with Force-Feedback Function

This article proposes an index to estimate the operator’s haptic sensation of the contact between the slave device and the environment in operating master–slave systems with force feedback function. The index value is derived from the velocity information of the master device before and after contact, which is hypothesized to represent the intensity of haptic sensation stimuli presented to the operator. Two characteristics of this index are discussed by means of psychophysics experiment, which are the statistical characteristics of the index value for different operators, and how the change in the operator’s haptic sensation is reflected on the index value. The index is validated by another psychophysics experiment. The experimental results show that the performance of operator’s haptic sensation can be predicted correctly based on the proposed index value. This index is expected to be applied in the parameter design of bilateral-control systems with force feedback function.