On design of quantized fault detection filters with randomly occurring nonlinearities and mixed time-delays

This paper is concerned with the fault detection problem for a class of discrete-time systems with randomly occurring nonlinearities, mixed stochastic time-delays as well as measurement quantizations. The nonlinearities are assumed to occur in a random way. The mixed time-delays comprise both the multiple discrete time-delays and the infinite distributed delays that occur in a random way as well. A sequence of stochastic variables is introduced to govern the random occurrences of the nonlinearities, discrete time-delays and distributed time-delays, where all the stochastic variables are mutually independent but obey the Bernoulli distribution. The main purpose of this paper is to design a fault detection filter such that, in the presence of measurement quantization, the overall fault detection dynamics is exponentially stable in the mean square and, at the same time, the error between the residual signal and the fault signal is made as small as possible. Sufficient conditions are first established via intensive stochastic analysis for the existence of the desired fault detection filters, and then the explicit expression of the desired filter gains is derived by means of the feasibility of certain matrix inequalities. Also, the optimal performance index for the addressed fault detection problem can be obtained by solving an auxiliary convex optimization problem. A practical example is provided to show the usefulness and effectiveness of the proposed design method.     

Nonlinear vibration analysis of spacecraft with local nonlinearity

Most spacecraft are usually assembled from some simple substructures by different kinds of connectors, which include various kinds of joints and hinges. Most of the connectors have properties of nonlinearity, and can strongly affect the dynamic characteristics of spacecraft. Mathematical models of such spacecraft usually have a large number of degrees of freedom (DOFs), but their nonlinear connectors are generally spatially localized. In general, it is impractical and time-consuming to directly calculate the frequency response of the spacecraft using current methods. To enhance the calculation efficiency of the frequency response, an improved approach is proposed in the present paper. With describing functions (DFs) and linear receptance data, the kinetic equations are firstly converted into a set of complex algebraic equations whose dimension is only associated with nonlinear DOFs and interested DOFs. Subsequently the number of iterative equations is reduced and only related to nonlinear DOFs. Hence the improved approach can be applicable to large-scale and complicated finite element (FE) models. An FE model of a satellite with some nonlinear joints is used to show and demonstrate the usefulness of the proposed method. Besides, the effects induced by nonlinear joints on payloads’ vibration of the satellite are discussed.     

ZnSe薄膜的增强吸收光双稳

报道了用常压ＭＯＣＶＤ生长的ＺｎＳｅ薄膜的光学非线性。在７７Ｋ下用纳秒脉冲激光观测到ＺｎＳｅ薄膜的增强吸收光双稳特征，非线性机理可能是由激子Ｃｏｕｌｏｍｂ相互作用屏蔽引起的。     

聚脲和聚酰亚胺的微波辐射合成

研究苯代三聚氰胺与2,4-甲苯基二异氰酸酯的微波辐射聚合及聚脲与均苯四酸二酐的微波固相聚合，考察了微波辐射时间（功率）、单体浓度、扩链剂和温度等因素对缩聚物的特性粘数、产率的影响，并与热聚合进行比较。用红外光谱对聚酰亚胺的亚酰化度进行了表征，首次用简并四波混频技术测量了缩聚物的三阶光学非线性极化率系数及其响应时间。实验结果表明：微波辐射对提高聚合物的特性粘数和产率有显著作用；合成的聚脲与聚酰亚胺具有较好的三阶光学非线性(聚脲的χ(3)=1.174×10－13esu)和较快的时间响应(24ps)。     

分布式FRA在WDM光传输系统中的作用

本文对分布式光纤喇曼放大器（FRA）利用功率耦合微分方程进行了数值计算，分析其分布放大特性，并结合对光纤通信系统容限及性能的计算讨论了利用FRA的分布放大特性降低WDM信号非线性，提高信噪比从而提高系统性能的可行性。此外指出了其在实际应用中的分布放大和频带利用等方面的局限性。     

碲基复合材料薄膜的三阶非线性光学特性

采用电化学诱导溶胶-凝胶法在导电玻璃片上制备了具有三阶非线性光学特性的碲基复合薄膜材料. 采用SEM( 扫描电镜)和EDX( X 光电子能谱)对薄膜的表面形貌和组成进行表征; 应用分光光度计得到薄膜的透射光谱、反射光谱、吸收光谱, 并结合脉冲激光器和 Z 扫描方法测量薄膜的三阶非线性光学特性. 实验结果表明制备的薄膜呈网状结构, 表面组分主要包括Si、Te、O元素; 薄膜在波长为1064nm处呈现负的非线性折射效应和饱和吸收的性质, 其非线性折射系数和非线性吸收系数分别为-4.18×10 ^{- 13} m²/W和-1.6×10 ^{- 6} m/W, 表明了碲基复合薄膜有较强的非线性光学效应, 得到三阶极化率为1.13×10 ^{- 14} (m/V)², 表明复合薄膜具有优良的三阶非线性光学性能.     

Strong tracking filter based adaptive generic model control

Generic Model Control (GMC) is a control algorithm capable of using nonlinear process model directly. Parameters in GMC controllers are easily tuned, and measurable disturbances can be compensated effectively. However, the existence of large modeling errors and unmeasurable disturbances will make the performance of GMC deteriorate. In this paper, based on the theory of Strong Tracking Filter (STF), a new approach to Adaptive Generic Model Control (AGMC) is proposed. Two AGMC schemes are developed. The first is a parameter-estimation-based AGMC. After introducing a new concept of Input Equivalent Disturbance (IED), another AGMC scheme called IED-estimation-based AGMC is further proposed. The unmeasurable disturbance and structural process/model mismatches can be effectively overcome by the second AGMC scheme. The laboratory experimental results on a three-tank-system demonstrate the effectiveness of the proposed AGMC approach.     

具有多个饱和非线性的系统分析与设计

提出了一种在状态空间中分析非线性系统的精确方法。对于具有多个非线性的分段线性系统来说，系统的状态空间被各非线性所对应的超平面分隔，系统在各超平面之间的状态轨迹可以用数值积分来求解，根据状态轨迹束穿过各超平面时截面之间的映射关系，可以分析是否存在自振荡。对于饱和非线性来说，给出了一种确定超平面的简便方法，因此本方法特别适合于分析具有多个饱和非线性的系统。最后给出了一个应用于高精度伺服系统设计的例子。