力觉交互系统稳定性研究

在中国国家自然科学基金资助项目《牙科手术模拟力觉交互系统稳定性研究》和《基于双模式力觉交互的灵巧动作技能训练方法研究》,以及中国国家高技术研究发展计划(863计划)项目《面向手眼协调操作的触(力)觉合成和视觉-力觉融合再现技术》的共同支持下,以开发高性能牙科手术模拟训练系统为目标,针对力觉交互设备控制过程中振动或噪声所导致的力觉感受稳定性丧失,围绕探索复杂虚拟环境下的力觉交互系统(HIS)失稳机理,基于力觉交互设备和力觉渲染算法,探索提高力觉交互系统稳定性和逼真度的方法,提出学术报告.通过模拟牙面探查实验,发现用虚拟工具接触牙齿表面时,若接触刚度较大会导致设备振动.通过模拟牙体预备实验,发现用虚拟工具切削牙齿时,大的接触刚度也导致设备振动.大刚度所引发的设备振动,可以通过减小刚度减少或消除,但随之而来的是由于接触力过小,导致系统丧失逼真度.因此,HIS稳定性研究的核心任务是探索在非解析表达复杂虚拟环境下的基于阻抗显示设备的HIS稳定性丧失的物理机理及其稳定合成算法.基于力觉交互系统(HIS)组成结构,假定操作者为系统的被动环节,将HIS稳定性问题分解为力觉交互设备和力觉合成算法等两部分,通过确定各自的验证任务和验证指标,实现问题解耦,方便HIS的设计和调试.在力觉设备稳定性研究方面,讨论了多自由力觉交互设备性能与系统稳定性的关系,建立了HIS控制参量与系统稳定性的关系模型,建立了提高系统稳定性的控制算法.研究发现,通过改变系统的物理参数和控制策略可以有效地提高力觉交互系统的稳定性.采用电流闭环控制策略(CCLC)和多更新率控制策略(MC)等两种方案提高了系统稳定性.CCLC是指在电机回路增加电流传感器,测量电机的实际电流,构成电流反馈;进而计算电机实际输出力矩,得到设备末端的实际输出力.MC是指在不增加上位机更新频率的前提下,在下位机微控制器上实现更高频率的插补运算,包括以更高的频率对设备末端的位置采样,以及对设备末端的输出力进行预估计算.控制器利用当前插补时刻的设备位姿,实时计算虚拟力增量,从而实现在两个连续上位机虚拟力的间隔内的高频率插补.基于自主开发的3自由度(3DOF)力觉交互设备实验平台,开展稳定性测定实验,证明了CCLC和MC的有效性.实验发现交互设备的最大可模拟虚拟刚度不仅与设备末端的位置有关,还与虚拟墙方向——虚拟力方向有关.通过实验测量得到了(3DOF)工作空间内不同点不同方向上可模拟最大刚度的分布.在力觉合成算法稳定性研究方面,基于动态单边约束的概念分析了复杂虚拟环境的力觉交互失稳机理,发现了制约系统稳定性的限制参量——等效接触刚度、动态单边约束的位置坐标变化梯度、动态单边约束的法线向量变化梯度,进而提出基于等效阻抗的稳定性处理算法.针对拥有大量数据的精细模型的力觉交互模拟,提出速度驱动的离散多层级模型力觉合成算法,离线建立物体层次模型,通过用户探查试验确定触发层次切换的速度阈值,并运用表面接触点层级映射改进碰撞检测算法,避免了模型层级切换时力信号的阶跃变化.基于等效阻抗的稳定性处理算法和离散多层级模型力觉合成算法在全口腔大数据量模型探诊中得到了验证.针对两种不同物理属性的组织的交界处交互时力觉交互设备的振动问题,提出适用于模糊边界的灰色区域法,在牙齿横切面的多组织探查和龋坏组织的探查中得到了应用.针对被操作物体拓扑结构的变化的力觉交互任务,采用了体素化建模方法,高效率地实现了材料去除和模型更新,并提出了适合于材料去除操作的虚拟匹配算法(Virtual Coupling Method),保证了拓扑结构变化时力觉模拟的稳定性,在牙体预备手术的牙齿钻削模拟中得到了验证.     

一种新型导纳力觉交互设备的研究

提出一种导纳型力觉接口设备,利用摩擦轮原理进行传动,其低惯量、高速等特点保证了力觉系统具有较高出力带宽.同时,以设备为平台建立了人机力觉交互系统,进行了力觉交互实验.     

一种飞机模拟驾驶力反馈设备的设计与实现

飞机模拟驾驶杆是飞行模拟器的重要组成部分,是向飞行员提供操纵力的人感系统。设计了一种新的阻抗型力觉交互设备,仿真飞机驾驶杆的操纵力,提出了弹簧-电动机的力控制方案。设备通过弹簧的变形为操作者提供反馈力,通过电动机做位置伺服控制弹簧的变形量改变设备的刚度,从而调整操纵力的大小。以一自由度的样机为平台建立了人机交互系统,进行了力觉交互实验,验证了力控制方案和传动方案的可行性。     

6-DOF双并联力觉交互系统设计及实验验证

研制了一种新型双并联力觉接口,采用改进Delta并联机构与3-RRR球面并联机构具有运动学解耦特性,使该构型在保证运动空间的同时消除了运动奇异点.建立了力觉接口的控制系统,提出了带有速度前馈的PI自适应稳定交互算法,实现了对于理想力信号的快速跟踪及扰动抑制.通过跟踪长方体表面及虚拟销孔装配作业实验,验证了新型力觉接口及其力觉交互系统的性能.     

机器人力觉示教的力控制及仿真分析

针对机器人传统示教方式逐渐无法满足复杂工业生产需求的现状,提出了一种基于六维力传感器的机器人力觉示教,并介绍了其系统组成。结合一些经典力控制方法及力觉示教实际,对机器人力觉示教的力控制系统展开研究,提出了基于速度的主动柔顺控制策略,从理论上建立了机器人力觉示教时末端工具受力和力矩的运动控制算法。通过Adams仿真软件,对机器人的力觉示教运动进行了仿真分析,最终结果表明该控制算法能够有效地实现机器人力觉示教控制,使力觉示教更加主动灵活,更好地满足复杂工业生产的工艺要求。     

一种基于材料切除方法的力反馈仿真模型研究

针对目前虚拟油泥造型技术缺少力觉造型控制的问题,提出一种新的基于材料刮削率的力反馈仿真模型.该模型中虚拟反馈力与材料刮削率成正比,计算机虚拟造型时,根据材料属性和单位时间内材料的实时刮削量来计算虚拟刮削力.在基于压缩体素模型的虚拟油泥造型原型系统中,利用Phantom Desktop力觉交互设备,成功地实现了具有力觉反馈的虚拟油泥造型.仿真实验结果证明,该模型可以满足虚拟油泥造型方法的要求,能够有效地增强造型过程的真实感,且稳定、高效.     

基于柔性铰链的大口径望远镜并联调整机构

为减小地基大口径望远镜在光学追踪过程中重力变形对成像质量的影响,设计了一种基于柔性铰链的高侧向刚度、亚微米精度并联调整机构。首先,介绍了系统组成并针对技术指标的要求,开展了两自由度柔性铰链设计。建立了柔性铰链并联机构的等效运动学模型和刚度模型,搭建了并联机构刚柔耦合运动学仿真系统,分析了柔性铰链对机构精度的影响。最后,搭建实验测试系统,来验证柔性铰链的设计合理性和并联调整平台刚柔耦合运动学分析的准确性。仿真和测试结果表明,柔性铰链转动刚度误差控制在3.54%之内,小位移（微米/角秒量级）运动精度达亚微米量级,大位移（毫米/度）运动精度与仿真结果对比误差控制在微米量级,机构侧向刚度优于60 N/μm,能够满足地基望远镜光学成像的要求。     

人机交互中的力/触觉设备进展综述

在虚拟现实和遥操作系统中,力/触觉接口是非常重要的人机交互设备.目前的力觉装置有外骨骼和固定设备、数据手套和穿戴设备、点交互设备和专用设备等,这些力觉装置中采用气动、液压、电机或磁场等驱动的主动式力反馈居多,也有基于液体智能材料的被动式力觉反馈.触觉的实现方法主要有由电磁(螺线管、发声线圈)驱动的机械振动,压电晶体、形状记忆合金驱动的探针阵列,气动系统,热力泵(塞贝克效应)系统等.     

带有双手力觉反馈的人机交互系统设计

力觉反馈可以在人机交互的过程中营造出沉浸感,而双手可以实现比单手更为复杂、精细的操作。因此,设计了一种带有双手力觉反馈的人机交互系统。该系统使用两个多自由度力觉反馈装置捕捉、跟踪操作人员手部位置并提供力反馈。系统实验结果表明,该系统可在500 mm×500 mm×420 mm工作空间内精确跟踪双手位置,跟踪误差小于0.8 mm,并可提供高达20 N的反馈力和0.4 N·m的反馈力矩。通过应用实例验证了系统的有效性。实例任务结果表明,带有双手力觉反馈的任务完成时间大大短于单手力觉反馈和无力觉反馈的任务完成时间。     

具有视觉和力觉反馈的虚拟装配

在虚拟装配中，要使人们对装配对象和装配环境获得全面、逼真、自然的认识，除了视觉信息外，还应提供触觉、力觉等信息。在实现人与虚拟环境之间的视觉和力觉交互方面进行了初步尝试，通过建立虚拟对象的仿真模型和虚拟与现实世界之间的交互模型，利用常见的商用软件构造了虚拟装配环境和虚拟装配对象，研制和开发了二维力觉交互装置——力反馈鼠标，并通过实例进行了人与虚拟环境之间视觉和力觉交互的验证实验。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.