Continuous time stochastic adaptive control: non-explosion, ε-consistency and stability

For completely observed continuous time constant parameter stochastic linear systems, an indirect adaptive control law is presented which, subject principally to a weak location hypothesis concerning the true parameter, and a persistent excitation hypothesis, generates ε-consistent recursive least squares parameter estimates and ensures the system is mean square sample path stable. The adaptive control algorith mentails (i) recursively calculating the least squares estimate of the system parameter, and (ii) recursively generating the LQR feedback gain matrix lying in a set of matrix gains γ known to contain a stabilizing gain. The a.s. non-explosion of the system is a direct consequence of this construction.     

薄板坯连铸工艺液芯压下的有限元分析

简要介绍世界几种主要薄板坯连铸工艺。着重叙述应用大型通用商业软件MSC.MARC。模拟液芯压下时铸坯的变形，确定最佳压下方案的有限元分析，液芯压下应该在结晶器出口处及二冷区扇形段开始部分进行，这样能减小铸坯的应变。     

A robust adaptive pole‐placement controller without strictly positive real condition

This paper considers the adaptive pole‐placement control problem for system (1) with unmodelled dynamics η_n dominated by a small constant ε multiplied by a quantity independent of ε but tending to infinity as the past input, output, and noise grow. Using bounded external excitation and randomly varying truncation techniques, we give a design method of adaptive pole‐placement controller. It is shown that the closed‐loop system is globally stable, the estimation error for the parameter contained in the modelled part is of order ε, and the closed‐loop system under the adaptive pole‐placement control law is suboptimal in the sense of $$\mathop{\lim\sup}\limits_{{n\to\infty }}{1\over n}\mathop{\sum}\limits_{i=0}^n{\left({A^{*}(z)y_{n}‐L(z)C(z)w_{n}‐B(z)R(z)y_{n}^{*}}\right)^{2}{\leq}O({\varepsilon}^{2})+\gamma^{2}\mathop{\sum}\limits_{j=1}^q{b_{j}^{2}}}$$\nopagenumbers\end while the SPR condition used usually in other papers is replaced by a stability condition. Copyright © 2001 John Wiley & Sons, Ltd.     

Finite‐Element Implementation of a Self‐consistent Texture Model with a Hardening Law Based on Dislocation Densities

A self‐consistent texture model is implemented in the finite‐element code ABAQUS/Explicit®. Hardening of the slip systems is described by evolution laws for dislocation densities, and the Bauschinger effect is included. With these ingredients the cold rolling of an IF‐steel is simulated and the evolution of texture and anisotropy is examined. The use of the dislocation based hardening law is found to have a significant effect on the evolution of the anisotropic yield surface, but only very little influence on the texture. Furthermore, the hardening model is used to investigate the evolution of dislocation densities in differently oriented grains during plane strain compression. It is found that the dislocation density varies greatly depending on orientation, an observation which can help to explain the orientation dependence of recrystallization.     

多孔薄膜荫罩热变形的有限元仿真设计

荫罩的热变形使电子束产生着屏偏移 ,进而导致了色纯变坏。本文采用大型软件ANSYS对 1 5英寸荫罩进行了热变形的有限元仿真 ,从而得到了电子束的着屏偏移。建立了包括阴极射线管 (CRT)里所有部件的完整的有限元模型。荫罩被建为无孔连续薄壳的模型 ,对它的表面导热系数和表面弹性模量作了等效的计算。考虑了弹簧片的预应力以及弹簧片和销钉的连接。这样可使我们的分析模型更接近真实情况。本文给出了 50 0、1 0 0 0、1 0 0 0 0s时的热变形和电子束着屏偏移。分析表明 :电子束着屏偏移的最大值发生在 50 0s左右。利用这种分析方法及研究结果可指导新型荫罩的设计和研制。     

基于随机分析和概率预测的固定式海洋平台结构风险评估研究

对极端海况进行了环境荷载的联合概率分析。引入了整体不确定性和敏感性分析理论,利用非正态过程、具有不同相关性的多变量随机模拟技术,求解结构的失效概率。提出结构失效分析的新方法,并利用DNV提供的历史数据,对结构失效的后果做了适当分析。以埕北12-C井组平台为实例,对平台甲板高程(Air Gap)失效分析进行了实例计算。结果表明,使用多维联合极值分布理论及相应的求解方法,是离岸工程结构物风险评估的重要手段。     

Total simulation model of the thermo-mechanical process in shape rolling of steel rods

The production of steel reinforcing bars for civil engineering is investigated by means of FEM-simulation. An integrated system for computing appropriate thermo-mechanical parameters of the rolling process is proposed. Generalized plane strain approach and coupled thermal-mechanical solution are applied. The microstructural model combines both the effect of the recrystallization mechanisms (static, dynamic and metadynamic) upon the austenite grain forming in hot rolling and that of phase transformation upon the final microstructure. The phases are created during interrupted below the temperature of martensite transition cooling. Thus a typical industrial process for thermo-mechanical strengthening of reinforcing bars, known as Tempcor-process is considered. Computational results are validated to experimental measured mechanical properties of the steel. By means of computer simulation the system can perform different solutions, giving the possibility to obtain a reasonable choice of different thermo-mechanical rolling conditions.     

碾压混凝土坝应力场有限元及施工仿真分析

采用三维有限元法对某碾压混凝土坝(RCC)在施工导流期的应力场进行分析,着重校核了顶部未到设计龄期的碾压混凝土和大型导流底孔周边的应力分布;并初步探讨了在多因素影响情况下,从开始施工到蓄水运行的坝体温度场、应力场的全过程仿真分析方法。     

Optimal and self‐tuning fusion Kalman filters for discrete‐time stochastic singular systems

Based on the optimal fusion estimation algorithm weighted by scalars in the linear minimum variance sense, a distributed optimal fusion Kalman filter weighted by scalars is presented for discrete‐time stochastic singular systems with multiple sensors and correlated noises. A cross‐covariance matrix of filtering errors between any two sensors is derived. When the noise statistical information is unknown, a distributed identification approach is presented based on correlation functions and the weighted average method. Further, a distributed self‐tuning fusion filter is given, which includes two stage fusions where the first‐stage fusion is used to identify the noise covariance and the second‐stage fusion is used to obtain the fusion state filter. A simulation verifies the effectiveness of the proposed algorithm. Copyright © 2008 John Wiley & Sons, Ltd.     

一种外置式视频同步信号发生器的设计

对随机视频信号的特点进行了研究，提出了采用谱分析提取随机视频信号的同步频率的方法，根据数据传输的要求设计了基于USB接口的外置式视频同步信号发生器并给出了系统的硬件框图和软件流程。系统具有自动分析随机视频信息隐含的同步信号频率，精确产生同步脉冲信号的特点，满足随机视频信号采集和稳定显示的同步要求。同步精度达到300帧内图像漂移小于1个像素。利用该视频同步信号发生器控制非标准图像采集卡实现了计算机辐射的随机视频信号的采集和稳定显示。