柔性臂协调运动系统的动态反馈镇定

研究柔性臂协调运动系统分布参数模型的镇定问题.基于系统能量关系和正实引理,提出一种构造性的设计方法.所设计的控制器由前馈和动态反馈两部分构成,其中动态反馈部分的传递函数是严格正实的.通过线性算子半群理论和LaSalle不变集原理,证明了闭环系统是渐近稳定的.     

基于DSP/FPGA的反步法阻抗控制柔性关节机械臂

针对柔性关节机械臂与环境接触时的柔顺控制问题,提出一种反步法阻抗控制方法,并基于李雅普诺夫稳定性理论证明了控制器的稳定性.该方法是在建立柔性关节机器人模型的基础上,将李雅普诺夫函数选取与控制器设计相结合的一种回归设计方法.它从系统的最低阶次微分方程开始,逐步设计满足要求的虚拟控制,最终设计出真正的控制器.轨迹跟踪和阻抗控制实验结果表明,该方法是有效而可行的.     

基于Proteus的硬件在回路仿真

软、硬件的并行开发方法可以加快设计进程,但在系统整合时常常出现诸如软、硬件不兼容等很多问题,而硬件在回路仿真能有效解决这些问题,它的最大特点是将软件仿真与实际硬件紧密联系起来,采用该技术可以在开发周期初完成嵌入式系统的仿真.介绍了一种基于Proteus的硬件在线回路仿真技术,为嵌入式产品的开发提出了新的思路.并通过"电子警察"这一具体开发实例来说明基于Proteus的硬件在回路仿真技术在嵌入式产品开发中的意义.实践证明,基于Proteus的硬件在回路仿真可以大大缩短产品的开发周期和降低开发成本.     

Electron‐beam deposition of MgO on plastic substrate and manufacturing flexible flat fluorescent lamp

Abstract— A flexible fluorescent lamp that utilizes the same plasma discharge mode as in PDPs has been manufactured. The structure of the flexible lamp is simple and easy to manufacture. All‐plastic materials including plastic substrates, barrier ribs (spacers), and sealants for low‐temperature manufacturing processing have been adopted except for the phosphor and MgO thin film. The MgO thin films were coated on the plastic substrates as a protection layer against the plasma discharge. The adhesion and biaxial texture of MgO thin film deposited on the plastic substrates, poly‐ethyle‐nenaphthalate (PEN) and polycarbonate (PC), at low temperature (100–180°C) has been characterized. The MgO film on PEN shows good adhesion under a repeated bending test. The manufactured flexible lamp consists of two plastic substrates of about 3 in. on the diagonal, barrier rib (spacer), and external ITO electrodes. The Ne‐Xe (5%) gas mixture at 100–200 Torr was used for the discharge gas. A maximum surface luminance of about 100 cd/m² was achieved for a 1 ‐kHz AC pulse.     

Fabrication of 5.8‐in. OTFT‐driven flexible color AMOLED display using dual protection scheme for organic semiconductor patterning

Abstract— A 5.8‐in. wide‐QQVGA flexible color active‐matrix organic light‐emitting‐diode (AMOLED) display consisting of organic thin‐film transistors (OTFTs) and phosphorescent OLEDs was fabricated on a plastic film. To reduce the operating voltage of the OTFTs, Ta₂O₅ with a high dielectric constant was employed as a gate insulator. Pentacene was used for the semiconductor layer of the OTFTs. This layer was patterned by photolithography and dry‐etched using a dual protection layer of poly p‐xylylene and SiO₂ film. Uniform transistor performance was achieved in the OTFT backplane with QQVGA pixels. The RGB emission layers of the pixels were formed by vacuum deposition of phosphorescent small molecules. The resulting display could clearly show color moving images even when it was bent and operated at a low driving voltage (below 15 V).     

Finite element formulation for dynamics of planar flexible multi-beam system

In some previous geometric nonlinear finite element formulations, due to the use of axial displacement, the contribution of all the elements lying between the reference node of zero axial displacement and the element to the foreshortening effect should be taken into account. In this paper, a finite element formulation is proposed based on geometric nonlinear elastic theory and finite element technique. The coupling deformation terms of an arbitrary point only relate to the nodal coordinates of the element at which the point is located. Based on Hamilton principle, dynamic equations of elastic beams undergoing large overall motions are derived. To investigate the effect of coupling deformation terms on system dynamic characters and reduce the dynamic equations, a complete dynamic model and three reduced models of hub-beam are prospected. When the Cartesian deformation coordinates are adopted, the results indicate that the terms related to the coupling deformation in the inertia forces of dynamic equations have small effect on system dynamic behavior and may be neglected, whereas the terms related to coupling deformation in the elastic forces are important for system dynamic behavior and should be considered in dynamic equation. Numerical examples of the rotating beam and flexible beam system are carried out to demonstrate the accuracy and validity of this dynamic model. Furthermore, it is shown that a small number of finite elements are needed to obtain a stable solution using the present coupling finite element formulation.     

Geometric nonlinear effects on the planar dynamics of a pivoted flexible beam encountering a point-surface impact

Flexible-body modeling with geometric nonlinearities remains a hot topic of research by applications in multibody system dynamics undergoing large overall motions. However, the geometric nonlinear effects on the impact dynamics of flexible multibody systems have attracted significantly less attention. In this paper, a point-surface impact problem between a rigid ball and a pivoted flexible beam is investigated. The Hertzian contact law is used to describe the impact process, and the dynamic equations are formulated in the floating frame of reference using the assumed mode method. The two important geometric nonlinear effects of the flexible beam are taken into account, i.e., the longitudinal foreshortening effect due to the transverse deformation, and the stress stiffness effect due to the axial force. The simulation results show that good consistency can be obtained with the nonlinear finite element program ABAQUS/Explicit if proper geometric nonlinearities are included in the floating frame formulation. Specifically, only the foreshortening effect should be considered in a pure transverse impact for efficiency, while the stress stiffness effect should be further considered in an oblique case with much more computational effort. It also implies that the geometric nonlinear effects should be considered properly in the impact dynamic analysis of more general flexible multibody systems.     

Controller design for flexible structure vibration suppression with robustness to contacts

Model-based feedback control of vibration in flexible structures can be complicated by the possibility that interaction with an external body occurs. If not accounted for, instability or poor performance may result. In this paper, a method is proposed for achieving robust vibration control of flexible structures under contact. The method uses robust linear state feedback, coupled with a state estimation scheme utilizing contact force measurement. Uncertain contact characteristics are modelled by a sector-bounded non-linear function, such that state feedback gains can be synthesized using a matrix inequality formulation of the Popov stability criterion. A separation theorem is used to establish a robust H₂ cost bound for the closed loop system. Experimental results from a multi-mode flexible structure testbed confirm that vibration attenuation and stability can be maintained over a broad range of contact characteristics, in terms of compliance and clearance.     

以太网电路仿真业务中基于本地时戳的自适应时钟方法

对以太网电路仿真业务中使用的时钟同步方法进行了详细分析.针对普通自适应时钟方法的不足,提出了一种新的自适应时钟方法--基于卡尔曼滤波的本地时戳方法.该方法可归于基于时戳的自适应时钟方法,但不需要在网络上传送时戳信息.该方法的原理是利用本地业务时钟和计数器得到表示远端和近端业务时钟的时戳信息(本地时戳).通过统计运算将时戳信息变换成满足卡尔曼过程和测量方程的随机序列,并利用卡尔曼滤波算法从该随机序列中过滤噪声,得到真实时戳.利用得到的时戳信息调节压控振荡器,从而使本地业务时钟跟踪远端业务时钟.设计了仿真设备实现本方法以及普通自适应时钟方法,并搭建测试拓扑进行评估和验证.测试结果表明,本方法综合性能更好.     

Petri网与数字系统设计

日益复杂的数字系统设计,须由各种专业的设计人员分工完成。他们之间需要一种描述系统的“共同语言”来沟通,这对于提高设计质量、缩短设计周期、减少设计费用具有积极意义。Petri网十分适合担任这一“共同语言”的角色。文章给出了数字电路测试仪器中的硬件设计的部分实例。