遥操作机器人系统中虚拟环境的构建

虚拟环境的建模是基于虚拟现实的遥操作机器人系统的关键技术。根据遥操作机器人系统中虚拟环境的组成结构,创建了虚拟机器人和弹性体作业对象的几何模型、运动模型和物理模型,推导了基于弹簧质点模型的弹性体受力和形变的基本方程,并介绍了虚拟现实系统的主要人机接口设备,最后建立了由数据手套控制的机器人抓取弹性小球的虚拟环境的模型。     

基于视景仿真的航炮弹道仿真系统研究

根据航炮多体系统动力学计算结果和二维弹道数值计算方法，运用虚拟仿真技术建立了一套可完成弹道解算、仿真及射击精度分析的可视化演示平台。平台的构建过程中探索了虚拟场景中空间数字模型和碰撞模型的构建方法，用以更简洁、高效的驱动特定虚拟场景进行仿真。此平台可以引入动力学计算的结果．较为真实的仿真航炮射击实验现场，并演示炮弹飞行轨迹及结果。     

Dynamic force simulator for multifinger force display

In this paper, the authors present a dynamic force simulator (DFS) for force feedback in human-machine systems. They propose a virtual world model with two force flows: one is the force flow from human to an object, the other is the force flow from an object to human. To use this model, the DFS simulates object dynamics, contact models, and friction characteristics of the human hand interacting with the object in virtual reality. After the derivation of kinematic and force relations between hand and object space, they balance the two forces: one from the human and the other from the object in the contact force space in virtual world and then realize the adequate feedback forces to human operator. Interaction with the DFS allows calculation and feedback of appropriate forces to the force controlled actuators of the sensor glove they have developed. In this paper grasping of a cylinder in the virtual world is presented. During object grasping, they measure joint angles and torques using the sensor glove system. In the future, they will use this system to analyze human dextrous manipulations called human skill     

虚拟现实技术-虚拟装配环境的构建

虚拟现实技术是一种有效的模拟人在自然环境中视、听、动等行为的高级人机交互技术。近年来,随着相关设备和技术的迅速发展,虚拟现实技术在各个领域得到广泛的应用,虚拟装配就是虚拟现实技术在制造业中的一个重要应用。本文主要探讨虚拟装配环境的构建过程,介绍了常用交互设备和以WTK工具包为代表的虚拟环境软件开发平台,重点分析了虚拟环境中的装配模型,比较两种主要的装配模型：关系模型和层次模型的结构及优缺点,提出了带约束图的结构树模型,并给出五元组结构来描述该模型中的节点。     

Virtual test track

The virtual test track (VTT) is a real-time vehicle simulator used for powertrain and chassis system development in a virtual environment. The VTT is designed and built based on the rapid control prototyping (RCP) concept. Therefore, different from the conventional vehicle simulator, the VTT can provide many additional benefits, such as ease of use, flexibility of interface with other devices, and ability to easily implement any hardware-in-the-loop system. The VTT consists of a powerful simulation engine to solve the equations of a complicated vehicle dynamics model in real-time and a sophisticated animation engine to provide real-time visual representation of vehicle behavior. It also contains multiple virtual test environments with variable surfaces and weather conditions to provide different types of driving conditions.     

Simplified approach for dynamics estimation of a minor mobility parallel robot

This paper presents the identification of an approximated polynomial model for the dynamics of a parallel kinematics machine. The case study of a specific translational Cartesian manipulator is faced. Firstly, an analysis of robot dynamics is performed to verify the presence of poorly relevant terms. A polynomial simplified model is then built by fitting the actual behaviour of the robot prototype. The seek of the coefficients of the interpolating polynomials has been constrained taking advantage of robot peculiarities, such as symmetry and intrinsic properties of multibody systems dynamics. The effectiveness of the proposed simplification is then verified by comparison with robot behaviour.     

Control of robotic object pivoting based on tactile sensing

Robotic manipulation of objects using the sole tactile feedback is a challenge. If the contact between the robot end effector and the manipulated object is distributed, the robot can exchange both friction forces and torques with it. The friction highly influences the motion of the object. By controlling the friction it is possible to perform complex manipulation tasks, such as moving the object with respect to the end effector by executing a controlled sliding motion. If the motion is a rotation with respect to the end effector, the corresponding maneuver is called pivoting. Control of the pivoting motion is considerably difficult, especially without any visual feedback. This paper proposes a novel method to regulate the object angular position, by means of a pivoting maneuver, through a parallel gripper endowed with force/tactile sensors. The strategy is based on a novel nonlinear observer that estimates the sliding velocity from force/torque measurements and a model of the sliding dynamics. We exploit the Limit Surface concept and the LuGre friction model to build a dynamic model of a planar slider. We show, through experimental results, that simple parallel grippers are able to execute such maneuvers that correspond to adding a virtual joint between the fingers, thus enlarging the robot workspace.     

Haptic Interaction Stability With Respect to Grasp Force

This paper addresses the contact instability of admittance control of a haptic interface. A high level of rigidity of the grasp of a subject operating the haptic interface will result in unstable behavior of the haptic interaction. Experiments with a system dedicated to measuring grasp force were performed to explore the conditions when grasp force has reached the critical grasp force that destabilizes the haptic interface. The critical grasp force was quantified for various values of virtual environment parameters. The experimental results are compared to simulation results obtained with a model of haptic interaction. To improve stability, two methods were applied: one with virtual coupling, the other with a compensator filter. A model was used to define the structure of the compensator filter and to determine the parameters of the virtual coupling and the compensator filter. Experimental and simulation results confirmed an improvement of stability. Both methods allow higher grasp forces of the human operator, and experiments show that the compensator filter allows higher grasp forces than the virtual coupling.     

Intelligent inferencing and haptic simulation for Chinese acupuncture learning and training.

This paper presents an intelligent virtual environment for Chinese acupuncture learning and training using state-of-the-art virtual reality technology. It is the first step toward developing a comprehensive virtual human model for studying Chinese medicine. Students can learn and practice acupuncture in the proposed 3-D interactive virtual environment that supports a force feedback interface for needle insertion. Thus, students not only "see" but also "touch" the virtual patient. With high performance computers, highly informative and flexible visualization of acupuncture points of various related meridian and collateral can be highlighted to guide the students during training. A computer-based expert system using our newly proposed intelligent fuzzy petri net is designed and implemented to train the students to treat different diseases using acupuncture. Such an intelligent virtual reality system can provide an interesting and effective learning environment for Chinese acupuncture.     

基于本体的虚拟空间模型的研究

虚拟空间模型是由空间对象及其之间的空间关系构成,它为虚拟场景的构建提供了重要的语义信息。然而,由于空间对象和空间关系本身的复杂性,构建的虚拟空间模型通常是不全面的、非具体的。针对这种问题,在充分研究本体以及UML的基础上,提出了利用本体标记虚拟空间对象及对象之间的空间关系,从而构建了虚拟空间本体。论文首先提出虚拟空间中方向关系的计算方法,然后使用UML描述虚拟空间本体的空间结构,并使用OCL描述虚拟空间本体中虚拟对象的约束信息。最后通过一个虚拟办公室的实例,证明了该方法的可行性以及有效性。     

A Real-Time, 3-D Musculoskeletal Model for Dynamic Simulation of Arm Movements

Neuroprostheses can be used to restore movement of the upper limb in individuals with high-level spinal cord injury. Development and evaluation of command and control schemes for such devices typically require real-time, “patient-in-the-loop” experimentation. A real-time, 3-D, musculoskeletal model of the upper limb has been developed for use in a simulation environment to allow such testing to be carried out noninvasively. The model provides real-time feedback of human arm dynamics that can be displayed to the user in a virtual reality environment. The model has a 3-DOF glenohumeral joint as well as elbow flexion/extension and pronation/supination and contains 22 muscles of the shoulder and elbow divided into multiple elements. The model is able to run in real time on modest desktop hardware and demonstrates that a large-scale, 3-D model can be made to run in real time. This is a prerequisite for a real-time, whole-arm model that will form part of a dynamic arm simulator for use in the development, testing, and user training of neural prosthesis systems.      

一种面向网格的二级并行计算模型研究与实现

网格的异构性、动态性使得传统的计算模型已经不能适应网格计算环境。文章提出一种面向网格的基于消息通信方式的二级计算模型以求解问题。二级计算模型可简述如下:第一步将任务粗粒度分解成若干子任务并映射到节点;第二步各节点进行全局竞争得到全局最优解并以全局最优解为对象进行细粒度方式协同计算。最后在上海高校网格E网格计算应用平台上实例验证。     

Virtual angiography for visualization and validation of computational models of aneurysm hemodynamics

It has recently become possible to simulate aneurysmal blood flow dynamics in a patient-specific manner via the coupling of three-dimensional (3-D) X-ray angiography and cmputational fluid dynamics (CFD). Before such image-based CFD models can be used in a predictive capacity, however, it must be shown that they indeed reproduce the in vivo hemodynamic environment. Motivated by the fact that there are currently no techniques for adequately measuring complex blood velocity fields in vivo, in this paper we describe how cine X-ray angiograms may be simulated for the purpose of indirectly validating patient-sperific CFD models. Mimicking the radiological procedure, a virtual angiogram is constructed by first simulating the time-varying injection of contrast agent into a precomputed, patient-specific CFD model. A time-series of images is then constructed by simulating the attenuation of X-rays through the computed 3-D contrast-agent flow dynamics. Virtual angiographic images and residence time maps, here derived from an image-based CFD model of a giant aneurysm, are shown to be in excellent agreement wiith the corresponding clinical images and residence time maps, but only when the interaction between the quasisteady contrast agent injection and the pulsatile flow are properly accounted for. These virtual angiographic techniques pave the way for validating image-based CFD models against routinely available clinical data, and provide a means of visualizing complex, 3-D blood flow dynamics in a clinically relevant manner. They also clearly show how the contrast agent injection perturbs the noraml blood flow patterns, further highlighting the potential utility of image-based CFD as a window into the true aneurysmal hemodynamics.     

Force display using a hybrid haptic device composed of motors and brakes

In the virtual environment, force feedback to the human operator makes virtual experiences more realistic. However, the force feedback using active actuators such as motors can make the system active and sometimes unstable. To ensure the safe operation and enhance the haptic feeling, system stability should be guaranteed. Both active actuators such as motors and passive ones such as brakes are commonly used for haptic devices. Motors can generate a torque in any direction, but they can make the system active and thus, sometimes unstable during operation. On the other hand, brakes can generate a torque only against their rotation, but they dissipate energy during operation and this dissipation makes the system intrinsically stable. Consequently, motors and brakes are complementary to each other. In this research, a two degree-of-freedom (DOF) haptic device equipped with motors and brakes is designed, in which each DOF is actuated by a pair of motor and brake. Simultaneous operation of motors and brakes is analyzed. Models for some environments, virtual wall contact and frictional effect, are proposed. The results for the hybrid haptic system are compared with those for the active haptic system and the passivity based control system. The experimental results show that the hybrid haptic device is more suited to some applications than the other haptic systems.     

Using EMG to anticipate head motion for virtual-environment applications

In virtual environment (VE) applications, where virtual objects are presented in a see-through head-mounted display, virtual images must be continuously stabilized in space in response to user's head motion. Time delays in head-motion compensation cause virtual objects to "swim" around instead of being stable in space which results in misalignment errors when overlaying virtual and real objects. Visual update delays are a critical technical obstacle for implementing head-mounted displays in applications such as battlefield simulation/training, telerobotics, and telemedicine. Head motion is currently measurable by a head-mounted 6-degrees-of-freedom inertial measurement unit. However, even given this information, overall VE-system latencies cannot be reduced under about 25 ms. We present a novel approach to eliminating latencies, which is premised on the fact that myoelectric signals from a muscle precede its exertion of force, thereby limb or head acceleration. We thus suggest utilizing neck-muscles' myoelectric signals to anticipate head motion. We trained a neural network to map such signals onto equivalent time-advanced inertial outputs. The resulting network can achieve time advances of up to 70 ms.     

Robust neural force control scheme under uncertainties in robotdynamics and unknown environment

The original impedance function is known to lack robustness due to unknown robot dynamic model and the environment. In order to improve that result, a new impedance function is derived which specifies a desired force directly. This results in a new robust robot force tracking impedance control scheme, which employs a neural network as a compensator to cancel out all uncertainties. The proposed neural force control scheme is capable of making the robot track a specified desired force as well as of compensating for uncertainties in environment location and stiffness, and in robot dynamics. Separate training signals for free-space motion and contact-space motion control are developed to train the neural compensator online. The design of the training signals is justified. Simulation studies with a three-link rotary robot manipulator are carried out and the results show excellent force tracking performance     

一个新颖的虚拟环境建模语言

 虚拟现实系统的复杂性使得对虚拟环境的建模工作较为困难,本文提出了基于属性-行为的面向对象语言模型对虚拟环境的建模提供了更强大的支持,尤其在行为描述、系统性能支持方面更加灵活.在此基础上,我们进一步设计并实现了虚拟环境建模语言YHVML,该语言作为虚拟现实软件开发平台的核心,具有较好的平台独立性.     

基于智能网络的租户服务质量保证技术

在多租户虚拟网络环境中,用户对于网络服务的多样性以及性能的稳定性需求并不会随着网络架构和运营模式的升级而削弱,用户需求之间的差异性和动态性对于不同切片间资源的分配和调度效率提出了新的挑战.针对多租户虚拟网络的特殊环境,首先提出了QVR(QoS-Virtual Routing)流量调度算法,同时将用户流量调度与网络虚拟资...