Optimal linear estimation for continuous stochastic systems with random observation delays

This paper is concerned with the linear minimum mean square error estimation for Itô‐type differential equation systems with random delays, where the delay process is modeled as a finite‐state Markov chain. By first introducing a set of equivalent delay‐free observations and then defining two reorganized Markov chains, the estimation problem of random delayed systems is reduced to the one of delay‐free Markov jump linear systems. The estimator is derived by using the innovation analysis method based on the Itô differential formula. And the analytical solution to this estimator is given in terms of two Riccati differential equations that are of finite dimensions. Conditions for existence, uniqueness, and stability of the steady‐state optimal estimator are studied for time‐invariant cases. In this case, the obtained estimator is very easy to implement, and all calculation can be performed off line, leading to a linear time‐invariant estimator. Copyright © 2011 John Wiley & Sons, Ltd.     

On input‐to‐state stability‐based design for leader/follower formation control with measurement delays

This paper addresses the design of low‐level controllers for leader–follower formations of nonholonomic vehicles in the presence of bounded measurement delays. The concept of input‐to‐state stability is extended to encompass the effect of bounded delays and restrictions on the input. A method is proposed to integrate a Smith predictor in a backstepping design on the basis of nested saturations and nonlinear small‐gain assignment, which allows for time delays in the feedback loop. Robustness analysis under uncertain bounded time delays is provided, and design tradeoffs resulting from the use of bounded controls are discussed. Illustrative simulations are shown to validate the design and robustness analysis in the context of a simple leader–follower trailing control problem. Copyright © 2012 John Wiley & Sons, Ltd.     

Automatic recognition of object size and shape via user-dependent measurements of the grasping hand

An investigation is conducted on the feasibility of using the posture of the hand during prehension in order to identify geometric properties of grasped objects such as size and shape. A recent study of Paulson et al. (2011) already demonstrated the successful use of hand posture for discriminating between several actions in an office setting. Inspired by their approach and following closely the results in motor planning and control from psychology (Makenzie and Iberall, 1994), we adopt a more cautious and punctilious approach in order to understand the opportunities that hand posture brings for recognizing properties of target objects. We present results from an experiment designed in order to investigate recognition of object properties during grasping in two different conditions: object translation (involving firm grasps) and object exploration (which includes a large variety of different hand and finger configurations). We show that object size and shape can be recognized with up to 98% accuracy during translation and up to 95% and 91% accuracies during exploration by employing user-dependent training. In contrast, experiments show less accuracy (up to 60%) for user-independent training for all tested classification techniques. We also point out the variability of individual grasping postures resulted during object exploration and the need for using classifiers trained with a large set of examples. The results of this work can benefit psychologists and researchers interested in human studies and motor control by providing more insights on grasping measurements, pattern recognition practitioners by reporting recognition results of new algorithms, as well as designers of interactive systems that work on gesture-based interfaces by providing them with design guidelines issued from our experiment.     

Reducing cache and TLB power by exploiting memory region and privilege level semantics

The L1 cache in today’s high-performance processors accesses all ways of a selected set in parallel. This constitutes a major source of energy inefficiency: at most one of the N fetched blocks can be useful in an N-way set-associative cache. The other N-1 cachelines will all be tag mismatches and subsequently discarded.We propose to eliminate unnecessary associative fetches by exploiting certain software semantics in cache design, thus reducing dynamic power consumption. Specifically, we use memory region information to eliminate unnecessary fetches in the data cache, and ring level information to optimize fetches in the instruction cache. We present a design that is performance-neutral, transparent to applications, and incurs a space overhead of mere 0.41% of the L1 cache.We show significantly reduced cache lookups with benchmarks including SPEC CPU, SPECjbb, SPECjAppServer, PARSEC, and Apache. For example, for SPEC CPU 2006, the proposed mechanism helps to reduce cache block fetches from the data and instruction caches by an average of 29% and 53% respectively, resulting in power savings of 17% and 35% in the caches, compared to the aggressively clock-gated baselines.     

On finite-time stability and stabilization of nonlinear port-controlled Hamiltonian systems

The finite-time stability and stabilization of nonlinear port-controlled Hamiltonian(PCH)systems are investigated in this paper,and a number of new results are proposed.Firstly,by exploiting the Hamiltonian structural properties,a proper form of the Hamiltonian function is obtained,based on which a finite-time stability criterion is then presented for a class of Hamiltonian systems.Secondly,using the obtained stability criterion and the so-called"energy shaping plus damping injection"technique,the continuous finite-time stabilization problem is studied for the PCH system,and several global stabilization results are provided.Finally,the continuous robust finite-time stabilization of the PCH system with external disturbances is investigated,and two results on designing global robust finite-time stabilizers are obtained.Study of several examples with numerical simulations shows that the control design approach developed in this paper works very well.     

Stability and static output feedback stabilization for a class of nonlinear discrete-time singular switched systems

In this paper, the stability and static output feedback stabilization problems for a class of nonlinear discrete-time singular switched systems are discussed. First, based on Lyapunov theory and the implicit function theorem, linear matrix inequalities sufficient conditions are developed which guarantee that the nonlinear discrete-time singular switched systems are regular, causal, have unique solution in a neighborhood of the origin, and are uniformly asymptotically stable. Then, with these conditions, and based on singular value decomposition approach, the design method of static output feedback controllers is given. Last, numerical examples are provided to illustrate the effectiveness of the proposed methods.     

S-粗集与数据挖掘单位圆特征

给出单向S-粗集(one direction singular rough sets)、单向S-粗集对偶(dual of one direction singular rough sets)的结构。单向S-粗集与单向S-粗集对偶是改进Z.Pawlak粗集得到的,单向S-粗集与单向S-粗集对偶具有动态特性。给出单向S-粗集、单向S-粗集对偶与Z.Pawlak粗集的关系。S-粗集具有三类形式:单向S-粗集、单向S-粗集对偶、双向S-粗集,利用单向S-粗集、单向S-粗集对偶,给出数据内挖掘、数据外挖掘概念,给出数据内挖掘的外同心圆定理、数据外挖掘的内同心圆定理,并给出其应用。S-粗集是粗集理论与应用研究的新分支。     

Gnash在ARM嵌入式Linux平台的实现①

Flash是Adobe推出的PC平台主流的多媒体格式标准和产品,但Adobe一直没有推出应的嵌入式解决方案。为了解决Flash格式动画文件在各种嵌入式设备上的播放问题,基于开源的GNUGnashflash解决方案,实现了flash动画文件在ARM嵌入式Linux平台的播放。分析了Gnash系统的组成结构,研究了其各个功能模块的实现技术以及与其他模块和操作系统平台的关系。然后针对嵌入式系统主频低、内存小的特点,对Gnash的功能模块进行裁剪,去掉了ActionScript引擎等动画播放不需要的交互式部分功能,并在基于ARM的Intel XSCALE PXA270嵌入式Iinux平台实现了Gnash系统。     

搜索引擎在学术期刊编辑工作中的作用与应用策略

本文通过阐述分析网络信息资料库的特点,讲述了学术期刊编辑如何使用搜索引擎来更简单方便的检索工作所需要的信息,并点明了在使用搜索引擎时应注意的问题,从而使编辑在工作中减少无用功,提高工作效率。     

基于图像处理的课室人员位置分布识别

对大型课室人员位置分布识别有利于课室灯光节能管理,基于面积判据的人员位置识别算法没有应用场景的约束,但容易因人体Blob图像粘连而产生误判;基于座位网格的算法只适用于直线排列的固定座位,但算法简单可靠。实验证明:两种方法均能有效地检测出人员分布情况,后者对固定座位的课室检测准确性更好,效率更高。