Practical Output Regulation of Uncertain Strict‐Feedback Form Systems

In this paper, an output feedback control is proposed to solve the practical output regulation problem of a class of nonlinear systems. In the first step of the design procedure, two sets of coordinate transformations are used to convert the output regulation problem of the system in the strict‐feedback form into the regulation problem of the transformed system in the uncertain normal form. Then, for the resulting system, a state feedback in the cast of nested sliding mode control is designed. Finally, by using the nonlinear separation principle, the output feedback controller is achieved by substituting the estimated states, resulting from the high‐gain observer, instead of real states. It can be shown that the states of the closed‐loop system are ultimately bounded. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

基于改进MUSIC的声源定位方法

为设计更有效的声源定位方法,深入研究了传统 MUSIC 算法,并针对其分辨率低且在麦克风数目较少时波达方向 (direction of arrival,DOA)估计精度较差等问题,对传统 MUSIC 算法进行了优化,利用广义互相关算法估计出声源信号到达各 麦克风之间的时间差,并据此构建出对应的矢量信号,最后通过计算谱函数确定 DOA 估计值。 仿真和实验结果表明,优化后的 MUSIC 算法可以得到更加尖锐的指向性波束,更低的旁瓣,并且能使方位角的定位精度达到±4°,俯仰角的定位精度达到±5°。     

Enhanced mechanical and thermal properties of AlN ceramics via a chemical precipitation process

A uniform dispersion of sintering additives is crucial to improve the thermal and mechanical properties of AlN ceramics. In this study, the Y₂O₃-coated AlN composite powder was successfully prepared by the chemical precipitation (CP) process, thereby improving the homogenization of Y₂O₃ in AlN green compacts. The precipitation coating behavior of Y₂O₃ precursor was investigated by FTIR and TG-DSC, and the corresponding reaction equation was proposed. The results of TEM, XRD, and XPS for the CP processed AlN powder indicated that a uniform amorphous Y₂O₃ layer was fully wrapped on the surface of AlN powder. The microstructures and phases of the sintered AlN samples prepared via the CP and conventional ball-milling (BM) processes, respectively, were compared. The CP process can result in decreasing oxygen content in AlN grains, facilitating the formation of the desirable isolated second phases, and strengthening the grain and grain boundary of AlN ceramic. As a result, the thermal conductivity, bending strength and fracture toughness of the CP processed AlN ceramic are 9.43%, 10.56%, and 18.50% higher than those of the BM processed sample, respectively, illustrating the CP process is a pretty effective way to simultaneously improve the thermal and mechanical properties of AlN ceramics.     

不同精度冗余数据的融合

针对融合误差的最大值和数学期望,提出了一个评判数据融合方法优劣的标准.随后,提出了一种新的数据融合方法,扩展加权平均法.当待融合数据为两个时,通过理论分析得到了计算融合参数的公式.当有更多的数据参与融合时,通过数值仿真得到了该方法的各个融合参数.该方法能解决最大似然估计法所难以解决的均匀分布数据的融合问题,且具有比包括最大似然估计法在内的其它三种有代表性的数据融合方法更高的精度.     

Non-conservative ultimate bound estimation in LTI perturbed systems

A closed formula for ultimate bound estimation in LTI systems with non-vanishing perturbations is presented. The formula, based on geometrical properties of the system, provides an alternative to Lyapunov's second method based study. Although it is not proven that the bound obtained is always less conservative than the Lyapunov's bound, some examples are introduced where the estimations are significantly improved. An extension of the idea for nonlinear systems is also sketched.     

气吸式排种器排种性能影响因素的试验研究

采用均匀设计的方法进行了气吸式排种器排种大豆质量影响因素的试验研究,考察了排种器排种盘转速和真空室压力与性能参数之间的关系,建立了粒距合格率、漏播率与重播率与影响因素之间的数学模型,获得了回归方程和最优结构参数。对于该气吸式排种器排种盘转速和真空室压力的最优化值分别为0.58r.s-1和0.003MPa,对气吸式排种器的设计具有指导意义。     

一种新的求全局最优的遗传算法

利用近年来广泛应用的遗传算法，对积分-水平集求全局最优概念性算法的蒙特卡罗随机投点的实现途径进行了改进，从而得到一种新的求全局最优的遗传算法。文中算法设计了适合的初始种群的均匀设计取法、交叉算子、变异算子和选择算子，给出了测度的勒贝格计算方法，从理论上证明了算法的收敛性。最后，选用了标准测试函数并与其他算法进行了比较，从数值上验证了算法的可行性。     

溴化锂主机冷却水水质问题分析

对一例具体工程溴化锂主体铜管腐蚀的原因进行详细实验分析，发现冷却水中产生：铜管点蚀的主要原因是冷却水中存在着Cl^-离子，但腐蚀部位的Cl^-含量却大大低于国家行业标：准中控制含量，故在此文中提出质疑。     

聚苯乙烯微球表面温敏性毛发特性研究

针对通过乳液种子半连续聚合法制得的表面带毛发状温敏性高分子刷单分散聚苯乙烯微球，研究不同接枝配方和工艺所导致的壳层不同高分子刷结构的温敏特性．并考察介质环境pH值和离子强度的影响。结果表明．纯PNIPA刷的相变温度在29．C～33℃之间．通过共聚所得的单一P（NIPA—co-AA）或P（NIPA—co—NVP）刷均使相转变温度提高，转变区域拓宽，当亲水性共单体的量过多时会导致相变过程不明显。微球表面同时存在PNIPA和P（NIPA—co—AA）两种高分子刷杂混时，会出现两个相变区域。而表面同时存在PAA和PNIPA两种纯高分子刷混合时．其相变过程不明显．且呈现奇异的震荡现象。此外．体系pH值较大时．有利于刷的舒展．表现出高的溶胀倍率，而离子强度增大别使刷的相变程度减弱．相变温度也发生偏移。     

Filtering on nonlinear time-delay stochastic systems

In this paper, we address the filtering problem for a general class of nonlinear time-delay stochastic systems. The purpose of this problem is to design a full-order filter such that the dynamics of the estimation error is guaranteed to be stochastically exponentially ultimately bounded in the mean square. Both filter analysis and synthesis problems are considered. Sufficient conditions are proposed for the existence of desired exponential filters, which are expressed in terms of the solutions to algebraic Riccati inequalities involving scalar parameters. The explicit characterization of the desired filters is also derived. A simulation example is given to illustrate the design procedures and performances of the proposed method.