On the filtered Smith predictor for MIMO processes with multiple time delays

This paper discusses about a unified implementation structure of the filtered Smith predictor (FSP) for MIMO processes with multiple time delays. Two kinds of dead-time free models are analyzed in order to extend the original properties of the SISO Smith predictor to MIMO processes with multiple time delays. It is demonstrated that FSP strategy can be applied to control open-loop unstable processes with multiple time delays by considering a model without any input, output or internal coupling delays. Moreover, for open-loop stable processes, it is shown that the FSP scheme can be used to speed-up disturbance rejection of processes with multiple time delays by using a nominal model without delay. Different simulation examples are used to illustrate the proposed strategy properties and advantages over other MIMO time-delay compensators. The results may be considered to control either square or non-square processes.     

基于分布式抗差最小二乘法的状态估计

针对电力系统互联的必然趋势,在研究传统算法和分布式算法的基础上,提出了基于结构和电压等级分布的组合分布式状态估计算法,建立了相应的数学模型。抗差估计理论主要研究抗拒少量粗差对估值的影响。拓扑错误和坏数据可以分别看作带有粗差的网络参数和量测数据,因此可以将抗差最小二乘法用于存在拓扑错误和坏数据时的状态估计。算例结果表明,基于分布式的抗差最小二乘法具有良好的抗粗差能力和收敛可靠性,并且收敛速度快。     

基于HVS和DWT数字图像水印算法的研究

文章采用了一种基于离散小波（DWT）多分辨率分解的数字水印技术,研究了水印算法,将图像进行三级小波分解,产生三个高频带系列子图和一个低频带子图。由于人眼对高频信息的敏感度低于对低频信息的敏感度,因此,采用了把水印嵌入到小波图像中的高频系数中。通过MATLAB仿真实验实现了将水印信息嵌入到原始图像中的技术,再对含水印图像加椒盐噪声、高斯低通滤波和缩小50％再放大200％进行攻击以及J-PEG压缩实验仿真,结果表明所提算法具有很好的视觉效果和鲁棒性。     

结构不确定Delta算子系统的鲁棒容错镇定

研究了圆形区域极点约束下Delta算子描述的不确定线性系统的鲁棒容错镇定问题.基于Riccati方程,导出了当Delta算子系统存在不确定性和执行器故障时,将闭环系统极点配置到指定圆盘内,确保系统鲁棒容错镇定的充分条件;运用线性矩阵不等式(Linear Matrcx Inequality,LMI)方法,对Delta算子不确定系统进行状态反馈设计,给出了系统在区域极点约束下鲁棒容错控制器存在的充分条件,并通过求解LMI得到鲁棒容错控制器的设计.通过数值仿真验证了该方法的有效性.     

时变滑模变结构与智能模糊结合的非线性系统控制

时变滑模变结构与智能模糊结合的非线性系统控制,先采用时变滑模变结构控制,通过设计动态滑模面,系统的任意初始状态一开始就处于系统的滑模面上,使系统对内部参数变化和外部干扰均具有全局鲁棒性.然后设计智能模糊控制器,使整个系统的鲁棒性在线调整,不仅增强了全局抗干扰能力,而且有效消除系统的抖振现象.     

Resilience analysis of shield tunnel lining under extreme surcharge: Characterization and field application

A resilient system should have the ability to mitigate the disruption caused by unfavorable environment and to rapidly recover to an acceptable performance level. In this paper, a detailed model to assess resilience of shield tunnel is presented. The performance robustness under disruption and the subsequent recovery rapidity are emphasized in this model. The tunnel horizontal convergence is selected as the performance indicator. The resilience index (Re) is defined by the ratio of the integral of the performance transition function over the integral of the normal performance function. The rationality and applicability of the model is validated by a real case of extreme surcharge on Shanghai metro tunnel. In this case, the performance transition and the normal performance degradation are characterized by the measured data. 70–80% of the normal performance is disrupted due to the surcharge, but only 1% is recovered by unloading of the surcharge in 9 days and 12.4% is recovered after 4 years by the soil grouting in 38 days. It results in a resilience index (Re) between 0.28 and 0.45. The lesson learned from the case indicates that the high vulnerability of lining convergence due to the severe surcharge and the long time duration between recovery measures could result in weak resilient abilities for shield tunnels. The value of resilience index Re could be significantly increased by 73% on average if the recovery duration were shortened.     

Robustness of hollow clay masonry units and seismic behaviour of masonry walls

As the recent experimental investigations indicated, the robustness of masonry units is one among the most decisive parameters which define the behaviour of masonry walls when subjected to seismic loads. If local brittle failure of units occurs, the mechanism of behaviour and known relationships between the strength and ductility properties of masonry walls change. In such a case, the design values of load bearing and energy dissipation capacity of masonry walls are overestimated, although the equations and requirements specified in the codes have been taken into consideration. If brittle units are used for the construction of structural walls, the actual structure will be exposed to an increased level of seismic risk although it has been designed for earthquake loads according to codes. This is especially the case of reinforced masonry, where brittle local failure prevents the transfer of predicted forces from reinforcing steel to masonry units. In order to provide limitations for the use of hollow units with large hole volume ratio and thin shells and webs in seismic areas, a measure to define the qualitative term “sufficient robustness”, specified in Eurocode 8, should be found.     

Bounded Nash type controls for uncertain linear systems

This paper deals with multicriteria controls for systems coping with polytopic uncertainties. The proposed controls are inspired by a Nash strategy for exactly known systems, reformulated as a nonconvex coupling between Semi-Definite Programming problems. The extension to the uncertain case duplicates the Linear Matrix Inequalities for all vertices of the polytope. A new iterative algorithm using Semi-Definite Programming is provided to design bounded Nash type controls for uncertain systems. A numerical example is given to illustrate the design method.     

Model reference adaptive control of air-lubricated capstan drive for precision positioning

Because friction-induced nonlinearities in positioning systems are generally range of motion-dependent, dual-model or dual-stage strategies are often adopted to deal with the inconsistencies encountered when a system moves from submicrometer steps (micro mode) to larger scale strokes (macro mode). Although good performance is usually obtained when each model/stage operates in its designed range of motion, a system frequently performs less satisfactorally when operating near the switching point between models or stages. An air-lubricated capstan drive was used in this study to minimize the discrepancy between macro and micro modes, and a single-mode MRAC was developed to control the capstan drive system for precision positioning. Accuracy better than ±15 nm with no overshooting was achieved in all conditions tested (including 50 nm, 500 nm and 10 μm steps). Disturbance resistance of the system also proved to be satisfactory.     

NEW OPTIMAL LARGE ANGLE MANEUVER STRATEGY FOR SINGLE FLEXIBLE LINK

INTRODUCTIONTo accommodate the requirement of lightweight,for many machine systems, such as flexiblemanipulator, large solar array and flexible antennas ofspacecraft, flexibility has become an imPOrtantcharacteristic. But flexible vibration can degrade badlythe peforance and the precision of flexible systems.Control of vibration becomes very important asdesigners attempt to push the state of the art withfaster and lighter machines systems. Researchers haveexammed many different controlle…