Influence of Vibration Modes and Human Operator on the Stability of Haptic Rendering

Developing stable controllers, which are able to display virtual objects with high stiffness, is a persistent challenge in the field of haptics. This paper addresses the effect of internal vibration modes and the human operator on the maximum achievable virtual stiffness. An 11-parameter mechanical model is used to adequately characterize the overall system dynamics. Experiments that are carried out on LHIfAM and PHANToM haptic interfaces demonstrate the importance of vibration modes to determine the critical stiffness when the user grasps the device.      

On Strong Stability Preserving Time Discretization Methods

Over the last few years, great effort has been made to develop high order strong stability preserving (SSP) Runge–Kutta methods. These methods have a nonlinear stability property that makes them suitable for the time integration of ODEs that arise from a method of lines approximation of hyperbolic conservation laws. Basically, this stability property is a monotonicity property for the internal stages and the numerical solution. Recently Ferracina and Spijker have established a link between stepsize restrictions for monotonicity and the already known stepsize restrictions for contractivity. Hence the extensive research on contractivity can be transferred to the SSP context. In this paper we consider monotonicity issues for arbitrary norms and linear and nonlinear problems. We collect and review some known results and relate them with the ones obtained in the SSP context.     

A Survey of Haptic Rendering Techniques

Computer Graphics technologies have developed considerably over the past decades. Realistic virtual environments can be produced incorporating complex geometry for graphical objects and utilising hardware acceleration for per pixel effects. To enhance these environments, in terms of the immersive experience perceived by users, the human's sense of touch, or haptic system, can be exploited. To this end haptic feedback devices capable of exerting forces on the user are incorporated. The process of determining a reaction force for a given position of the haptic device is known as haptic rendering. For over a decade users have been able to interact with a virtual environment with a haptic device. This paper focuses on the haptic rendering algorithms which have been developed to compute forces as users manipulate the haptic device in the virtual environment.     

基于谱离散方法的时滞系统PID参数整定

长流程生产过程不同回路之间存在耦合和时滞,是一个复杂的多输入多输出(Multiple Input Multiple Output,MIMO)多重时滞系统,其控制器参数整定尤为困难。为此,提出了一种基于谱离散方法的多重时滞系统PID参数整定方法,该方法运用多重时滞对象模型的伴随矩阵构造解耦矩阵,并将解耦的多重时滞系统以状态空间形式表达,通过采用谱离散方法限定闭环特征根的分布区域进行PID参数整定。由于无需模型约简即可进行参数整定,提高了多重时滞系统PID参数的整定效率。运用该方法对Wood-Berry二元精馏塔模型进行PID参数整定并仿真,并与其他方法比较,表明该方法在响应速度和扰动抑制方面具有优越性。预计提出的方法在其他长流程生产过程PID控制器参数整定方面也将有广泛的应用前景。     

图像的力/触觉表达技术研究综述

总结了图像的力/触觉表达技术研究的现状及特点,分析了图像的力/触觉表达研究中存在的问题,并展望了该技术的发展前景.     

Stabilization of Uncertain Systems With Markovian Modes of Time Delay and Quantization Density

This work studies the stabilization of a class of control systems that use communication networks as signal transmission medium. The lateral motion of independently actuated four-wheel vehicle is modeled as an uncertain-linear system. Time delay and quantization density are modeled as Markov chains. The networked control systems (NCSs) with plants being lateral motion are first transformed to switched linear systems with uncertain parameters. Sufficient and necessary conditions for the stochastic stability of closed-loop networked control systems are then established. By solving the matrix inequalities, this work presents an output-feedback controller that depends on the modes of time delay and quantization density. The controller performance is illustrated via a vehicular lateral motion system.      

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.     

彩色图像的纹理力/触觉渲染方法

针对图像纹理力/触觉再现技术中用灰度变化表征纹理所导致的彩色图像在灰度变换后丢失纹理信息的缺点,用颜色变化表征纹理,提出彩色图像的纹理力/触觉渲染方法.该方法中,切向力的计算基于像素力场算法,法向力的计算基于惩罚算法,根据颜色和空间感的心理学效应提出由亮度和色调决定约束空间,合力通过手控器反馈给操作者.实验结果表明,文中方法能够有效地对彩色图像纹理进行力/触觉渲染.     

滞后型控制系统的稳定性判据

本文根据李雅普诺夫稳定性理论,推导出滞后型控制系统x(t)=Ax(t)+Atx(t-T)无条件稳定的充分条件.并且证明所建立的稳定性代数判据,不仅简明易用,且能获得较大的稳定区域.     

触觉可视化技术中柔性物体变形模型研究

触觉可视化技术的出现开辟了虚拟现实技术新的应用前景,柔性物体变形技术成为其中的研究热点。论文对触觉可视化技术中柔性物体变形技术进行深入研究,系统地讨论了基于几何的力变形模型与基于物理意义力变形模型,分析了相关模型的基本思想和优缺点,对这些建模方法的性能进行了细致的比较。结果表明随着硬件技术的不断发展,基于物理意义的有限元模型将会得到越来越多的应用。最后对柔性物体物理形变建模的未来发展趋势做了探讨。     

触觉可视化技术中柔性物体变形模型研究

触觉可视化技术的出现开辟了虚拟现实技术新的应用前景,柔性物体变形技术成为其中的研究热点。论文对触觉可视化技术中柔性物体变形技术进行深入研究,系统地讨论了基于几何的力变形模型与基于物理意义力变形模型,分析了相关模型的基本思想和优缺点,对这些建模方法的性能进行了细致的比较。结果表明随着硬件技术的不断发展,基于物理意义的有限元模型将会得到越来越多的应用。最后对柔性物体物理形变建模的未来发展趋势做了探讨。     

单滞后时变区间动力系统的指数稳定性

用矩阵测度和时滞微分不等式研究了单滞后时变区间动力系统 x(t) =N[P(t) ,Q(t) ]x(t) +N[C(t) ,D(t) ]x(t -τ) ,τ≥ 0 的指数稳定性 ,给出了其指数稳定的判别准则 ,推广和改进了文 [1～ 3]的工作     

A Fundamental Tradeoff Between Performance and Sensitivity Within Haptic Rendering

In this paper, we show that for haptic rendering using position feedback, the structure of the feedback loop imposes a fundamental tradeoff between accurate rendering of virtual environments and sensitivity of closed-loop responses to hardware variations and uncertainty. Due to this tradeoff, any feedback design that achieves high-fidelity rendering incurs a quantifiable cost in terms of sensitivity. Analysis of the tradeoff reveals certain combinations of virtual environment and haptic device dynamics for which performance is achieved only by accepting very poor sensitivity. This analysis may be used to show that certain design specifications are infeasible and may guide the choice of hardware to mitigate the tradeoff severity. We illustrate the predicted consequences of the tradeoff with an experimental study.     

网络化时滞控制系统的有限时间稳定性分析

针对网络控制系统中存在于传感器-控制器-执行器间的双时延问题,提出了一种基于Markov模型的状态反馈控制策略.与传统应用Markov随机过程的方式相比,该策略采用两个Markov链描述每一个时延,通过状态反馈把该随机系统描述为具有四个随机参量的离散Markov跳变系统.利用Lyapunov有限时间稳定性理论分析得到该系统稳定的充分条件,并利用线性矩阵不等式(LMI)得到了可行的反馈矩阵.数值仿真结果进一步证明了该策略的有效性.     

具有参数扰动时滞系统的鲁棒镇定性

利用标量的Ｌｙａｐｕｎｏｖ函数，结合代数Ｒｉｃｃａｔｉ方程和Ｒａｙｌｅｉｇｈ’ｓ原理，讨论了具有参数扰动时滞系统的鲁棒镇定性，获得了一个充分条件。     

时滞神经网络的全局渐近稳定性分析

研究一类具有时滞的细胞神经网络的稳定性问题,利用Lyapunov—Krasovskii泛函的方法,给出时滞相关的稳定性判据。稳定性判据是以线性矩阵不等式的形式给出,可以很容易得出时滞的上界。在得到时滞相关的稳定性判据的同时也可以得到时滞无关的稳定性判据。数值算例说明其结果的优越性。     

带时滞的线性时变奇异系统的稳定性

通过比较方法建立了一类带时滞的线性时变奇异系统的稳定性判据,并讨论了相应的带有时滞的时变区间奇异系统的稳定性,给出了一个稳定性的比较定理。     

New Sufficient Conditions for Finite Time Stability of Nonlinear Time Delay Systems

In this note, we propose two new sufficient conditions on finite time stability for nonlinear time delay systems. First, a sufficient condition is proposed to verify the stability of systems by employing a continuously differentiable Lyapunov‐Krasovskii functional with indefinite derivative. Second, another sufficient condition is proposed by extending the Razumikhin approach, moreover, the corresponding estimate on convergence time of systems is also given. The results obtained herein are less conservative than the existing methods, i.e., they relax the restriction that the Lyapunov function of systems has to be decreasing in the convergence process. Finally, two numerical examples are provided to show the effectiveness of the theoretical results.