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.     

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.     

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.     

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.     

用于软组织变形仿真的层状菱形链连接模型

为提高软组织变形仿真的精度与实时性,提出一种新颖的、基于物理意义的层状菱形链连接模型.该模型中每层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接触力.利用6-DOFDelta手控器构建了力触觉交互实验系统,使用虚拟软组织模型进行按压、拉拽等交互操作,并通过反馈力产生触觉感.实验结果表明,该模型不仅计算简单,而且能够保证触觉接触力和变形计算具有较高精度;同时在交互过程中,力触觉感觉平稳、模拟效果逼真、满足虚拟现实系统对精细作业和实时性的要求.     

一种虚拟手术二维力觉交互装置的力学模型

对力交互装置在虚拟手术巾有着广泛的应用,作为基础研究,提出一种二维力觉交互装置的反馈力模型,通过模拟虚拟器械与肌肉组织和骨骼碰撞时的受力情况,验证模型的合理性。首先,根据人体组织的生物力学性能,参照Kamopp模型和胡克定律提出了系统的反馈力模型;然后针对系统的性能指标,通过对肌肉和骨骼两种组织的碰撞实验,验证了设备在虚拟手术过程中反馈力实现效果。仿真结果显示,反馈力方法能较准确地仿真力的变化,准确地感知骨骼的位置,对于虚拟手术系统的实用性具有重要意义。     

面向上颌骨骨折复位手术的虚拟系统设计

基于3D计算机触觉视觉交互(CHAI3D)和开放图形库(Open GL)等开源软件,设计了针对上颌骨复位手术的仿真系统。使用真实病例的CT图像搭建虚拟场景,通过Geomagic力反馈设备对虚拟模型进行三维操作并输出触觉反馈。在原有单点碰撞算法的基础上,提出了使用多个中介代理的多点碰撞算法,避免了虚拟手术工具的手柄插入虚拟器官的不实仿真;通过力反馈设备对头颅骨模型进行选择、移动和旋转,模拟手术中对头颅骨的移动和放置。系统可用于训练医学院学生,也可用于复杂手术的术前规划。     

面向虚拟介入手术的电磁力反馈模型的设计与仿真

为满足虚拟血管介入手术中力触觉反馈的实时性和精准性,采用磁悬浮原理设计一种力反馈模型生成虚拟介入手术中的周向旋转力触觉.通过分析通电线圈磁场特性和介入手术操作模式,首先设计电磁线圈阵列的拓扑结构和手术器械模型;随后针对线圈阵列提出最优电流分配策略并进行仿真验证;最后通过模型融合方法构建力矩-电流预测模型.实验结果表明,该模型能以3％的误差、40 Hz的频率预测出电流,结合最优电流分配策略可对介入手术中的关键力反馈进行实时、精确还原.     

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.     

基于力反馈的虚拟脊柱手术模拟系统的构建

针对医学手术排练演习和手术教学开发了虚拟脊柱手术模拟平台。在该平台上能够根据手术的真实环境,模拟常用手术器械和脊柱结构,实现人机实时交互。详细介绍了系统的硬件环境参数,并基于3DS MAX的建模和力触觉渲染引擎CHAI 3D进行仿真。仿真实验结果表明,基于力反馈的虚拟脊柱手术模拟系统可以有效地模拟脊柱手术时的力反馈状态,帮助医师进行脊柱手术术前训练,并适用于高校的医学教学和医疗机构人员的培训。     

Influences of haptic communication on a shared manual task

With the advent of new haptic feedback devices, researchers are giving serious consideration to the incorporation of haptic communication in collaborative virtual environments. For instance, haptic interactions based tools can be used for medical and related education whereby students can train in minimal invasive surgery using virtual reality before approaching human subjects. To design virtual environments that support haptic communication, a deeper understanding of humans′ haptic interactions is required. In this paper, human′s haptic collaboration is investigated. A collaborative virtual environment was designed to support performing a shared manual task. To evaluate this system, 60 medical students participated to an experimental study. Participants were asked to perform in dyads a needle insertion task after a training period. Results show that compared to conventional training methods, a visual-haptic training improves user′s collaborative performance. In addition, we found that haptic interaction influences the partners′ verbal communication when sharing haptic information. This indicates that the haptic communication training changes the nature of the users′ mental representations. Finally, we found that haptic interactions increased the sense of copresence in the virtual environment: haptic communication facilitates users′ collaboration in a shared manual task within a shared virtual environment. Design implications for including haptic communication in virtual environments are outlined.     

Image-driven virtual simulation of arthroscopy

In recent years, minimally invasive arthroscopic surgery has replaced a number of conventional open orthopedic surgery procedures on joints. While this achieves a number of advantages for the patient, the surgeons have to learn very different skills, since the surgery is performed with special miniature pencil-like tools and cameras inserted through little incisions while observing the surgical field on video monitor. Therefore, virtual reality simulation becomes an alternative to traditional surgical training based on hundreds years old apprentice–master model that involves either real patients or increasingly difficult to procure cadavers. Normally, 3D simulation of the virtual surgical field requires significant efforts from the software developers but yet remains not always photorealistic. In contrast to this, for photorealistic visualization and haptic interaction with the surgical field we propose to use real arthroscopic images augmented with 3D object models. The proposed technique allows for feeling the joint cavity displayed on video monitor as real 3D objects rather than their images while various surgical procedures, such as menisectomy, are simulated in real time. In the preprocessing stage of the proposed approach, the arthroscopic images are stitched into panoramas and augmented with implicitly defined object models representing deformable menisci. In the simulation loop, depth information from the mixed scene is used for haptic rendering. The scene depth map and visual display are reevaluated only when the scene is modified.     

虚拟现实大空间下多虚拟目标被动触觉交互方法

针对虚拟现实（VR）大空间下为重定向行走的用户提供被动触觉时存在的虚实交互目标无法一一对应的问题,提出了一种用两个物理代理作为触觉代理为多个虚拟目标提供触觉反馈的方法,以在基于人工势场（APF）的重定向行走过程中,交替地满足用户被动触觉的需求。针对重定向行走算法本身以及标定不精确等原因造成的虚实不对齐的问题,对虚拟目标的位置及朝向进行设计并且在交互阶段引入触觉重定向。仿真实验表明对虚拟目标位置和朝向的设计可以大幅降低对齐误差;而用户实验结果证明触觉重定向的引入进一步提升了交互准确性,且能为用户带来更丰富、更具沉浸感的体验。     

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。     

A haptic pedal for surgery assistance

The research and development of mechatronic aids for surgery is a persistent challenge in the field of robotic surgery. This paper presents a new haptic pedal conceived to assist surgeons in the operating room by transmitting real-time surgical information through the foot. An effective human–robot interaction system for medical practice must exchange appropriate information with the operator as quickly and accurately as possible. Moreover, information must flow through the appropriate sensory modalities for a natural and simple interaction. However, users of current robotic systems might experience cognitive overload and be increasingly overwhelmed by data streams from multiple modalities. A new haptic channel is thus explored to complement and improve existing systems. A preliminary set of experiments has been carried out to evaluate the performance of the proposed system in a virtual surgical drilling task. The results of the experiments show the effectiveness of the haptic pedal in providing surgical information through the foot.     

SPH haptic interaction with multiple-fluid simulation

Physics-based fluid interaction plays an important role in computer animation, with wide applications in virtual reality, computer games, digital entertainment, etc. For example, in virtual reality education and games, we often need fluid interactions like acting as an alchemist to create a potion by stirring fluid in a crucible. The traditional input devices such as a mouse and keyboard can basically input 2D information without feedback. In recent years, the continuous development of haptic device not only can achieve six degrees-of-freedom input, but also can calculate the force in virtual scenes and feedback to the user to make a better virtual experience. How to use haptic device in different kinds of virtual fluid scenarios to provide better experience is an important issue in the field of virtual reality. On the other hand, the researches on multiple-fluid interaction especially based on smoothed particle hydrodynamics (SPH) method are very lacking. Therefore, we study the key techniques of haptic interaction with SPH multiple-fluid to compensate this defect in computer graphics community. Different from the single-phase flow, interaction with multiple-fluid flow has difficulties in the realization of properties of different phases. After adding the multiple-fluid simulation, it is also important to keep haptic interaction real time. Our research is based on the mixture model. We guarantee the authenticity of multiple-fluid mixing effect while changing the drift velocity solver to improve efficiency. We employ a unified particle model to achieve rigid body–liquid coupling, and use FIR filter to smooth feedback force to the haptic device. Our novel multiple-fluid haptic simulation can provide an interactive experience for mixing liquid in virtual reality.     

Finding the Latent Semantics of Haptic Interaction Research: A Systematic Literature Review of Haptic Interaction Using Content Analysis and Network Analysis

As interest in multimodal and tangible interfaces is increasing in the field of human–robot interaction and virtual reality, haptics has been researched across areas such as engineering, computer science, psychology, and neuroscience. The main objective of the study was to construct a comprehensive review of the current haptic‐related literature based on quantitative data derived from content analysis and network analysis. Using the results of content analysis and network analysis of 6,000 research articles on haptic interaction, the haptic‐related literature was classified into two categories: 1) studies on technologies providing haptic stimuli and 2) studies on the human perception of haptic stimuli. Emotions in haptic feedback and haptic perception characteristics of various body sites were identified as potential research topics for further investigation. Greater research effort on understanding human haptic sensation and perception using the proposed systematic approach could accelerate the development of haptic interaction technology.     

Six degree-of-freedom haptic rendering using spatialized normal cone search

This paper describes a haptic rendering algorithm for arbitrary polygonal models using a six degree-of-freedom haptic interface. The algorithm supports activities such as virtual prototyping of complex polygonal models and adding haptic interaction to virtual environments. The underlying collision system computes local extrema in distance between the model controlled by the haptic device and the rest of the scene. The haptic rendering computes forces and torques on the moving model based on these local extrema. The system is demonstrated on models with tens of thousands of triangles and developed in an accessibility application for finding collision-free paths.     

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。     

Control systems of haptic man-machine interfaces

Methods for construction of stable control systems for the mechanism of haptic interaction used in haptic man-machine interfaces are considered. These interfaces reconstruct realistic haptic perception of a virtual object by a man. Two approaches to the control synthesis for the interaction mechanism are proposed and analyzed. The first one is based on tracking the open-loop trajectory of motion of the virtual object (body), and the second one is based on tracking the force of interaction with this object. Unlike known papers, the analysis takes into account the nonlinearity of the control system. The analysis is performed for two possible interaction regimes: “pushing” and “holding” of the virtual object. Stability conditions that are easily implemented are obtained.