时滞对象的自抗扰控制

时滞系统的控制在自动化领域具有重要意义。在剖析时滞系统控制的Smith预估法的本质的基础上,提出利用具有强大噪声抑制能力的"跟踪微分器"来实现"相位超前"、"相位滞后"等功能,从而解决时滞系统控制问题的新办法,其中包括把时滞算子近似成单位1的无视时滞法;把时滞算子近似成一阶惯性环节的提高阶次法;模仿Simith预估法把相位超前的虚拟输出当作被控量来进行无时滞对象控制的输出超前法;及引入虚似控制量的输入超前法等。相应的仿真研究表明,这些新方法都能控制好大时滞系统的控制问题,时滞大小已不再成为"难控"和"易控"的标准。     

基于粒子群优化算法的虚拟机放置策略

当前云计算虚拟化平台无法适用于对时延要求较高的应用。为此,提出一种基于粒子群优化算法的虚拟机放置策略。介绍粒子群优化算法,建立云环境内部时延模型,设计虚拟机放置策略架构。实验结果表明,该策略的请求响应时间比动态资源调度(DRS)策略降低14%~19%,每秒处理请求数比DRS方案提高约17%。     

基于虚拟现实的无时延感空间机器人遥控操作研究*

主要研究了克服空间机器人遥控操作时延问题的虚拟建模和仿真技术。首先概述了遥操作时延问题的研究现状;然后提出了一种基于虚拟现实预显示技术解决时延问题的方案;最后开发了基于虚拟现实的无时延感的遥控操作系统,并进行了仿真实验研究。仿真结果表明,虚拟现实技术在有效克服空间机器人遥控操作大时延中发挥了重要作用。     

A virtual subnet scheme on clustering algorithms for mobile ad hoc networks

Resolving the broadcast storm problem is an important issue in mobile ad hoc networks (MANETs). In this paper, we propose an approach for constructing a virtual subnet whose nodes are logically related. The virtual subnet can be spread upon clusters of a MANET. An intelligent agent with a routing filtering table is proposed to assist the best known clustering algorithms, the original Least ID algorithm and the original Highest Connection Cluster (HCC) algorithm, to improve group communication efficiency. Our simulation covers the network factors of hop count, deprave rate, and delay time. The simulation results show that when the proposed intelligent agent is used with the HCC algorithm, the delay time was reduced by 81.84% as compared with flooding, and by 49.25% as compared with the Ad Hoc On-Demand Distance Vector (AODV) routing algorithm. The delay time for the Least ID algorithm assisted by the proposed agents reduced by 81.84% compared to that of flooding and by 50% compared to that of AODV.     

均衡虚拟空间会议系统的混频时延和混频器数量的技术研究

合成虚拟空间会议系统(VST)的一个需要考虑的重要因素是混频器数量和混频时延的关系，其中混频器数量影响系统的成本，而混频时延影响系统的实时性，降低系统的混频时延和降低混频器数量是一对矛盾的问题．基于VST系统的通信效率与混频器关系，提出了在保证系统通信容忍的时延情况下，选取最少的混频器数量，以及在分层结构中系统通信的最小时延策略．采用这种策略能够有效地保证VST系统提供较高质量的服务时延和较低成本的混频．     

Dynamic virtual environment to test teleoperated systems with time delay communications

This paper presents a dynamic virtual environment tool for training operators and to prove different control schemes in telerobotic systems, and describes virtual reality environments used in teleoperated robotic systems. In the presented tool, the kinematic and dynamic model of the remote environment which is manipulating the operator is considered. The paper also describes how time delays in the communication channel can be easily added to the simulator, in order to analyze their effects in the teleoperated system. Finally, some experimental results achieved with this virtual teleoperated system are shown. With the presented dynamic simulator, different control schemes designed to overcome the time delay problem could be tested. © 2005 Wiley Periodicals, Inc.     

Synchronization control for physics-based collaborative virtual environments with shared haptics

In this paper, we propose a synchronization scheme to achieve a high level of consistency in peer-to-peer-based shared virtual environments (SVEs), as well as to display natural and realistic motions of virtual objects, in collaborative haptic tasks. The synchronization scheme utilizes an advanced feedback controller to compensate for the state error between geographically separated sites with a significant amount of time delay. It is designed using the mathematical model of a two-user SVE manipulating a freely moving object represented as a mass with damping resistance, with a haptic interface. Thanks to feedback control theory of time delay systems, the controller is shown to result in closed-loop stability and is be robust to perturbations in the time delay. Together with the synchronization control, a recovery filter is also designed and integrated so as to preserve the natural behavior of the synchronized object, which is, otherwise, affected by the feedback control action. In addition to verifying the theoretical results, two experiments using real Internet and local area network communications are carried out. These tests clearly support the validity of the analyses and demonstrate the applicability of the synchronization scheme.     

Hybrid client-server architecture and control techniques for collaborative product development using haptic interfaces

In this paper, a collaborative product development and prototyping framework is proposed by using distributed haptic interfaces along with deformable objects modeling. Collaborative Virtual Environment (CVE) is a promising technique for industrial product development and virtual prototyping. Network control problems such as network traffic and network delay in communication have greatly limited collaborative virtual environment applications. The problems become more difficult when high-update-rate haptic interfaces and computation intensive deformable objects modeling are integrated into CVEs for intuitive manipulation and enhanced realism. A hybrid network architecture is proposed to balance the computational burden of haptic rendering and deformable object simulation. Adaptive artificial time compensation is used to reduce the time discrepancy between the server and the client. Interpolation and extrapolation approaches are used to synchronize graphic and haptic data transmitted over the network. The proposed techniques can be used for collaborative product development, virtual assembly, remote product simulation and other collaborative virtual environments where both haptic interfaces and deformable object models are involved.     

基于虚拟仪器的霍尔电流传感器延迟补偿研究

对霍尔电流传感器延迟产生的机理进行分析。采用虚拟仪器技术,用实验方法辨识出霍尔电流传感器测量超声频域信号的延迟时间。介绍了非线性曲线拟合方法在电流传感器延迟补偿中的应用。测试表明,补偿收到了良好的效果。     

Deterministic model and transient analysis of virtual circuits

A model for a virtual circuit in the form of a tandem of servers that process incoming packets using a FIFO (first-in, first-out) discipline is proposed. The service times are assumed to be known completely. These may differ from packet to packet and from server to server. The model permits a variety of buffer or transit time constraints to be incorporated into the model. Several results that help one to understand the transient behavior of a virtual circuit are presented. On the basis of these results, a number of schemes that may be used to determine the time when the next packet must be sent over the network are presented. Transit delay and throughput are used to evaluate a given schedule. Solutions are given for maximum throughput, minimum transit delay, and maximum throughput under transit delay constraints. It is expected that these results will have a substantial bearing on the study of congestion control policies in computer networks, particularly those based on predicting network behavior     

在ZigBee网络中建立虚拟链状网

由于ZigBee网络的6层深度限制,直接建立的链状网效用不大,即使通过改进协议栈的方法来建立链状网络,必会增大信息传输的时延,导致不可靠等问题。针对这种情况,使用ZigBee透传模块+Arduino控制器建立"改良节点",在不破坏ZigBee原有网络特点的基础上,提出并实现了可远程、在线建立并管理的虚拟链状网络。该网络能够充分利用ZigBee的自组网、路由转发、透传等网络优势,发挥较高的网络传输效率并降低时延,同时该链状网还可以根据需要进行加长和缩短,实现动态管理。所提建立ZigBee虚拟链状网的方法可广泛应用在智能交通、智能电网、智能照明等系统中。     

Design of PID controllers for interval plants with time delay

First of all, the box theorem is extended to the interval plants with the fixed delay. An approach is presented to design the PID controller for interval plants with the fixed delay, which can obtain all of the stabilizing PID controllers. Then, using Hermite–Biehler theorem, extreme point results are provided by the virtual quasi-polynomials. When two virtual and two vertex quasi-polynomials corresponding to a Kharitonov-like segment plant are stable under a particular PID controller, it is sufficient that the same PID controller can stabilize this Kharitonov-like segment plant. The virtual quasi-polynomials are obtained in a simple way, and they are expressed in terms of the controller and the Kharitonov polynomials of the interval plants. A PID controller stabilizes interval plants with the fixed delay if it simultaneously stabilizes thirty-two quasi-polynomials. The example is given to illustrate the proposed method.     

无源散射变换的双边移动机器人网络遥操作

网络遥操作系统的随机时延给控制器设计带来巨大挑战,严重时破坏系统的稳定性。首先对遥操作无源理论及其波变量控制方法做了简单综述,然后提出直接无源散射变换方法,它将无源双边控制方法推广到具有随机时延的网络遥操作系统中去,保证网络遥操作系统在任何不对称随机网络时延情况下稳定。最后基于此变换方法设计了一个虚拟主从手双边移动机器人网络遥操作方案,并进行了仿真验证,结果表明结出的设计方法能满足系统性能要求。     

高铁列车运行图冗余时间优化布局方法研究

在分析各种冗余时间之间作用机理的基础上,以列车旅行时间和列车到发站延误时间最短为优化目标,建立运行图冗余时间优化布局模型。在此基础上引入遗传粒子群优化算法对模型进行求解,并用MATLAB仿真。以虚拟运行时刻表为背景,通过合理设置列车运行干扰时间和仿真分析方案,对结果进行分析。结果表明：用该模型和算法得到的布局方案相比较于固定比例方案,总延误时间短,列车在区间和车站的晚点次数少;相比较于遗传算法求解该模型的总延误时间短,总冗余时间设置多,但是列车在车站和区间的晚点次数少。     

虚拟仿真技术在网络闭环控制中的应用

Internet上数据传输的不确定延时妨碍了远程被控对象和操作者之间迅捷而透明的交互,严重限制了网络远程控制系统的性能和应用。为了解决网络延时问题,提出一种基于虚拟仿真的网络三闭环控制结构。该方法依照开环系统实现闭环控制的思想,在客户端构造虚拟被控对象模型,使虚拟仿真系统与实际系统的运行状态相似甚至相同,同时又使操作者能依据虚拟仿真系统一端的运行情况决定下一步的控制指令,从而准确地对实际系统发出所需的控制指令,最终达到远程实时控制的目的。仿真结果证明了所提方法的有效性和可行性。     

Distance Estimation Error Compensation of a Direct Control Type, Internet-based Mobile Robot System

This research is concerned with the development of an Internet-based mobile robot system, which is insensitive to the unpredictable Internet time delay in data transmission. For this purpose, the PPS (Position Prediction Simulator) is suggested and implemented to compensate for the time delay problem of the Internet. The PPS is divided into two parts, including the 3D virtual simulator and the robot position prediction part. The proposed PPS shows the visual information of a remote site, which is obtained from image processing and predicted position considering the time delay. The simulation results showed that the direct control using the PPS is insensitive to the time delay problem as in the indirect control. For the verification of the proposed PPS, the robot was moved and stopped following the planned path under various traffic conditions. The experimental results showed that the distance error could be reduced using the developed PPS.     

虚拟手术环境中软组织的快速碰撞检测

针对虚拟手术中软组织碰撞检测的实时性问题,提出了一种基于延迟更新策略的快速检测方法。该方法应用层次包围盒（BVH）的思想并根据拓扑结构特征来表示手术环境中的对象,同时使用延迟更新的策略来降低更新的计算量。首先用不同的层次包围盒来表示手术工具和手术对象;然后利用包围盒的相交测试快速排除不相交部分;再对可能发生碰撞的部分使用更为精确的三角面片相交测试来确定碰撞信息,最后使用延迟更新的策略来完成软组织变形时层次包围盒的更新。实验表明,该方法相较于现有算法在保持检测精度的同时能够有效提高碰撞检测的速度。     

虚拟环境中的计算时延

初步研究了虚拟环境中计算时延的特性,从能量传输的角度讨论了计算时延对虚拟环境稳定性的影响,并设计了一个虚拟阻尼器以抵消计算时延产生的多余能量,从而保证虚拟环境的无源稳定性.     

基于双适应度遗传算法的虚拟机放置的研究

减少数据中心产生的网络时延以及优化数据中心能源消耗和物理资源的浪费等越来越受到研究者的关注。主要关注数据中心的物理资源的浪费和数据中心产生的网络时延,并且建模一个多目标优化问题:最小化数据中心的物理资源以及数据中心的时延。通过改进型双适应度遗传算法将两个目标同时优化,将其结果与贪心算法进行比较,实验结果表明,此算法优于贪心算法,是云环境下有效的虚拟机放置算法。     

A core stateless bandwidth broker architecture for scalable support of guaranteed services

We present a novel bandwidth broker architecture for scalable support of guaranteed services that decouples the QoS control plane from the packet forwarding plane. More specifically, under this architecture, core routers do not maintain any QoS reservation states, whether per-flow or aggregate. Instead, the QoS reservation states are stored at and managed by a bandwidth broker. There are several advantages of such a bandwidth broker architecture. Among others, it avoids the problem of inconsistent QoS states faced by the conventional hop-by-hop, distributed admission control approach. Furthermore, it allows us to design efficient admission control algorithms without incurring any overhead at core routers. The proposed bandwidth broker architecture is designed based on a core stateless virtual time reference system developed recently. This virtual time reference system provides a unifying framework to characterize, in terms of their abilities to support delay guarantees, both the per-hop behaviors of core routers and the end-to-end properties of their concatenation. We focus on the design of efficient admission control algorithms under the proposed bandwidth broker architecture. We consider both per-flow end-to-end guaranteed delay services and class-based guaranteed delay services with flow aggregation. Using our bandwidth broker architecture, we demonstrate how admission control can be done on a per domain basis instead of on a "hop-by-hop" basis. Such an approach may significantly reduce the complexity of the admission control algorithms. In designing class-based admission control algorithms, we investigate the problem of dynamic flow aggregation in providing guaranteed delay services and devise a new apparatus to effectively circumvent this problem. We conduct detailed analyses to provide theoretical underpinning for our schemes as well as to establish their correctness. Simulations are also performed to demonstrate the efficacy of our schemes.