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。     

一种基于物理意义的快速力反馈形变模型及实时力觉响应算法

虚拟物体在受力作用时的形变建模是虚拟环境中力/触觉人机交互的关键.文中提出了一种新的基于物理意义的形变建模方法,不仅计算速度快,满足力反馈的实时性要求,而且能够同时保证接触力和形变的计算具有较高的精度,适用于具有较大变形量的柔性物体的力反馈计算,满足精细作业对虚拟现实系统的要求.     

Noncontact impedance control for redundant manipulators

Proposes an impedance control method that can regulate a virtual impedance between a robot manipulator and external objects using visual information. The conventional impedance control method is not useful in some cases where no interaction force between the arm and its environment exists, although it is one of the most effective control methods for manipulators in contact with the environment. Using the proposed method, we can control the manipulator motion based on the virtual impedance before contact with the objects. The validity of the proposed method is verified through computer simulations and experiments using a direct-drive robot     

具有力感觉的声带肿物切除仿真方法研究

在虚拟手术系统中,实时的图形显示和使操作者感觉到真实的操作力是非常重要的。该文介绍了在建立虚拟手术系统中,具有力感觉的声带肿物切除的仿真方法。首先介绍了软组织声带以及声带肿物的几何建模办法,考虑到虚拟手术中对实时性的要求,采用了分块建模的方法;然后通过对软组织生物力学特性的分析,利用弹簧-质量-阻尼模型对其建模。采用的算法减小了计算量,真实地仿真了声带肿物取出时声带的变形以及操作者感觉到的力。     

一种具有重力补偿的串联弹性执行器接触力控制方法

针对机械臂末端安装串联弹性执行器(Series Elastic Actuator,SEA)与环境或工件接触作业工况,考虑SEA端部负载对接触面压力随机械臂运动姿态变化的问题,研究一种具有重力补偿的SEA接触力控制方法。首先分析了一种基于滚珠丝杆模组的SEA与Staubli TX90 组合的力控制实验装置结构,建立了SEA与工件接触过程的动力学模型,提出了一种具有输入重力补偿的PD型SEA弹簧力控制方法,该方法在没有接触力传感器的情况下,依据机械臂关节角对SEA端部负载进行重力输入补偿,通过检测弹簧压缩变形量,计算并反馈弹簧力实现对接触力的控制。最后通过SEA与正弦面工件接触力控制实验,并对力传感器采集的接触力信号进行频谱分析,验证了所提出控制方法的有效性。     

Real-time area-based haptic rendering and the augmented tactile display device for a palpation simulator

Although people usually contact a surface with some area rather than a point, most haptic devices allow a user to interact with a virtual object at one point at a time and likewise most haptic rendering algorithms deal with such situations only. In a palpation procedure, medical doctors push and rub the organ's surface, and are provided the sensation of distributed pressure and contact force (reflecting force) for discerning doubtable areas of the organ. In this paper, we suggest real-time area-based haptic rendering to describe distributed pressure and contact force simultaneously, and present a haptic interface system to generate surface properties in accordance with the haptic rendering algorithm. We represent the haptic model using the shape-retaining chain link (S-chain) framework for a fast and stable computation of the contact force and distributed pressure from a volumetric virtual object. In addition, we developed a compact pin-array-type tactile display unit and attached it to the PHANToM^TM haptic device to complement each other. For the evaluation, experiments were conducted with non-homogenous volumetric cubic objects consisting of approximately 500 000 volume elements. The experimental results show that compared to the point contact, the area contact provides the user with more precise perception of the shape and softness of the object's composition, and that our proposed system satisfies the real-time and realism constraints to be useful for a virtual reality application.     

Providing force feedback in virtual environments

An integral part of successfully manipulating objects is the sensation of touch or force. Experiments with telerobots (robots controlled at a distance) show that the sensation of force and contact improves the efficiency and accuracy of such tasks. Many believe that the same can be said of tasks in a virtual environment. Unfortunately, it is not possible to actually grasp a virtual object in the same manner as you would a real object because virtual objects are defined in the computer, while the user exists in the real world. Thus, there must be some intermediate device that provides the user with the effects of touch, either through the virtual environment itself or in a physical model of the object, which then communicates information to the virtual environment and displays the virtual object to the user. At the University of Tokyo, we are experimenting with surface display, a method that allows users to directly manipulate an object in a virtual environment by touching a physical model of the object's surface as presented by an intermediate device outside the computer. We have created a prototype of such a device that measures the force exerted on the surface. We have also implemented control and calculation methods, and have evaluated both the device and the methods in experiments with users. These experiments have validated the concepts underlying our work, and we are continuing to investigate implementation issues     

Interactive rigid body manipulation with obstacle contacts

The interactive manipulation of rigid objects in virtual reality environments requires an object behaviour which is at least physically plausible to be useful for applications such as interactive assembly simulation and virtual training. Physically plausible behaviour implies that collisions between simulated solid objects are taken into account and that the motion of objects with obstacle contacts can be controlled without force feedback mechanisms in an intuitively correct manner. We present a real time framework which enables the simulation of interactively controlled solid objects with a dynamically changing set of contact constraints. In this paper all contact configurations are replaced by a canonical set of point contacts which is updated dynamically. The basic step to determine the contact forces and object motion consists in the solution of a non-linear complementarity problem (NCP), which results from the unilateral contact conditions together with an adequate discretization of the corresponding differential equations of motion. © 1998 John Wiley & Sons, Ltd.     

基于接触有限元模型的虚拟手指力建模研究

触觉反馈是虚拟现实应用中使人获得沉浸感的重要方式。随 显示技术的日趋成熟,触觉和力反馈的研究的焦点之一,如何度量虚拟手在接触物体时反馈的力的大小 是力反馈中的首要一步,对此,该文在研究了力反馈类型的基础上,给和指与虚拟物体间的接触数学模型,提出了基于接触有限元的接触数学模型,并有杉ＡＮＳＹＳ对霏 均匀有理Ｂ样条的手指表面和虚拟按钮间的接触变形和力分布情况进行了计算,得出了力反馈所需要的接触力大小。     

Exploring legibility of augmented reality X-ray

Virtual objects can be visualized inside real objects using augmented reality (AR). This visualization is called AR X-ray because it gives the impression of seeing through the real object. In standard AR, virtual information is overlaid on top of the real world. To position a virtual object inside an object, AR X-ray requires partially occluding the virtual object with visually important regions of the real object. In effect, the virtual object becomes less legible compared to when it is completely unoccluded. Legibility is an important consideration for various applications of AR X-ray. In this research, we explored legibility in two implementations of AR X-ray, namely, edge-based and saliency-based. In our first experiment, we explored on the tolerable amounts of occlusion to comfortably distinguish small virtual objects. In our second experiment, we compared edge-based and saliency-based AR X-ray methods when visualizing virtual objects inside various real objects. Moreover, we benchmarked the legibility of these two methods against alpha blending. From our experiments, we observed that users have varied preferences for proper amounts of occlusion cues for both methods. The partial occlusions generated by the edge-based and saliency-based methods need to be adjusted depending on the lighting condition and the texture complexity of the occluding object. In most cases, users identify objects faster with saliency-based AR X-ray than with edge-based AR X-ray. Insights from this research can be directly applied to the development of AR X-ray applications.     

非结构环境下基于人机合作技术的抓取作业研究

介绍了一种利用人机合作技术在非结构环境引导机械手抓取静态目标的方法．分别介绍了将激光—CCD摄像机系统与操作者的经验相结合获得抓取目标位置的方法,及将虚拟现实技术与操作者的经验相结合获得抓取目标姿态的方法．继而利用基于模型的视觉引导技术,引导手臂完成抓取操作．     

Elastic Model of Deformable Fingertip for Soft-Fingered Manipulation

We propose a straightforward static elastic model of a hemispherical soft fingertip undergoing large contact deformation, as occurs when robotic hands with the fingertips handle and manipulate objects, which is suitable for the analysis of soft-fingered manipulation because of the simple form of the model. We focus on formulating elastic force and potential energy equations for the deformation of the fingers which are represented as an infinite number of virtual springs standing vertically. The equations are functions of two variables: the maximum displacement of the hemispherical fingertip and the orientation angle of a contacting planar object. The elastic potential energy has a local minimum in our model. The elastic model was validated by comparison with results of a compression test of the hemispherical soft fingertip     

一种虚拟环境温度触觉再现仿真系统设计

分析了温度触觉感知特性,提出了手指和物体接触时各自表面的温度变化过程,结合单热源温度触觉再现装置设计了一种基于三维力反馈手控器的虚拟环境温度触觉再现仿真系统。手控器可控制虚拟手的动作,对虚拟物体进行温度和力的感知。仿真系统中能再现手指与不同热属性物体接触时的温度变化和力变化,且视觉效果逼真,体现了温度触觉再现的实时性和有效性。     

Optimisation-based proximity queries and penetration depth computation

The virtual reality (VR) was found to be a perfect technique that could be used as a training approach, since it shows many advantages despite its weakness. In the VR some major bottlenecks arises namely the proximity queries (PQ) and penetration depth computation. This paper shows a novel algorithm used to solve those problems. Problems of PQ are ubiquitous within many tasks in computer graphics, virtual environments, robotics, manufacturing, and mechanical design. Interactions in any virtual scene usually involve contact or close proximity between its objects. Determining which pairs of objects are in contact or at close proximity is a complex task in most of the virtual environments. The PQ is the shortest vector over which one object needs to be translated in order to bring the pair in contact.     

MM-UAV: Mobile Manipulating Unmanned Aerial Vehicle

Given significant mobility advantages, UAVs have access to many locations that would be impossible for an unmanned ground vehicle to reach, but UAV research has historically focused on avoiding interactions with the environment. Recent advances in UAV size to payload and manipulator weight to payload ratios suggest the possibility of integration in the near future, opening the door to UAVs that can interact with their environment by manipulating objects. Therefore, we seek to investigate and develop the tools that will be necessary to perform manipulation tasks when this becomes a reality. We present our progress and results toward a design and physical system to emulate mobile manipulation by an unmanned aerial vehicle with dexterous arms and end effectors. To emulate the UAV, we utilize a six degree-of-freedom miniature gantry crane that provides the complete range of motion of a rotorcraft as well as ground truth information without the risk associated with free flight. Two four degree-of-freedom manipulators attached to the gantry system perform grasping tasks. Computer vision techniques and force feedback servoing provide target object and manipulator position feedback to the control hardware. To test and simulate our system, we leverage the OpenRAVE virtual environment and ROS software architecture. Because rotorcraft are inherently unstable, introduce ground effects, and experience changing flight dynamics under external loads, we seek to address the difficult task of maintaining a stable UAV platform while interacting with objects using multiple, dexterous arms. As a first step toward that goal, this paper describes the design of a system to emulate a flying, dexterous mobile manipulator.     

计算碰撞检测中接触位置的算法

介绍了一种针对用三角形网面表示的不规则物体的碰撞检测中接触点,接触法线和刺穿深度的计算方法.该方法先将两三角形网面的交线投影到一个坐标轴上,然后对交线端点的投影点进行排序,从而将交线分成一组或多组,每组交线首尾相连构成一个圈,每个圈代表一个接触区域;针对每个接触区域,利用交线计算接触点,接触法线,并根据三角形网面在接触位置的拓扑关系,分顶点,边和面三种刺穿情况计算出刺穿深度.通过实际应用,证明了该方法在解决不规则物体的多点碰撞检测中的可行性和可靠性,适用于三维游戏制作、虚拟现实中的物理仿真等各项应用研究.     

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.     

Physically accurate haptic rendering with dynamic effects

We focus on the realism/transparency aspect of haptic rendering. We introduce a novel approach that enables physically correct and accurate simulation of contact wrench W/sub c/ for general rigid objects in real time, taking into account not only friction and gravity but also dynamic effects. Our method for contact force and moment simulation builds on the real-time identification of geometrically valid contact states despite digital errors. Our approach applies to general rigid bodies including both polyhedral and nonpolyhedral objects. For nonpolyhedral, curved objects, we build our contact state representation and contact force/moment model directly on the smooth and accurate representation of the object surfaces. Our approach's key idea is to solve for the contact force and moment analytically based on not only the contact configuration, but also the real-time identification of the exact type of the corresponding contact state, the type of instantaneous motion of the held object prior to reaching the contact configuration.     

Two-handed tangible interaction techniques for composing augmented blocks

Modeling tools typically have their own interaction methods for combining virtual objects. For realistic composition in 3D space, many researchers from the fields of virtual and augmented reality have been trying to develop intuitive interactive techniques using novel interfaces. However, many modeling applications require a long learning time for novice users because of unmanageable interfaces. In this paper, we propose two-handed tangible augmented reality interaction techniques that provide an easy-to-learn and natural combination method using simple augmented blocks. We have designed a novel interface called the cubical user interface, which has two tangible cubes that are tracked by marker tracking. Using the interface, we suggest two types of interactions based on familiar metaphors from real object assembly. The first, the screw-driving method, recognizes the user??s rotation gestures and allows them to screw virtual objects together. The second, the block-assembly method, adds objects based on their direction and position relative to predefined structures. We evaluate the proposed methods in detail with a user experiment that compares the different methods.     

Modelling and design of an augmented reality differential drive mobility aid in an enabled environment

In this paper the authors discuss the modelling and design of an augmented reality platform for disabled wheeled mobility studies. This design consists of a virtual environment with two degrees of freedom motion platform and integrated ground contact force feedback. Differential drive mobility users continue to be in touch with reality on their own mobility aid while interacting with virtual objects. The major domain related to the differential drive mobility of the disabled members of society which coincides with the use of manual wheelchairs, electric wheelchairs and mobility scooters. In order to account for environmental and dynamic effects, the wheeled mobility user needs to map the intended trajectory into the virtual world. Motion and inertia force feedback produced on the augmented simulator give the users a haptic sensory stimulus input regarding spatial movement and ground contact forces. The main objective is to model and design an augmented reality platform with real world kinematic and dynamic properties to place a wheeled mobility user closer to real world encounters. The use of the designed augmented reality platform will be beneficial to disabled wheeled mobility users in need of occupational therapist training and evaluation.