Simultaneous stabilization for a collection of nonlinear control systems in canonical form

A controller design method is provided to simultaneously stabilize a collection of nonlinear control systems in canonical form. It is shown that, under a mild assumption, any collection of nonlinear systems in canonical form can be simultaneously stabilized by one continuous state feedback controller. A constructive universal formula is presented explicitly. An illustrative example is given to demonstrate the validity of the method. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Output regulation of nonaffine nonlinear systems using singular perturbation theory

A control synthesis method for output regulation based on singular perturbation theory combined with inverting design is considered for a class of nonaffine nonlinear systems. The resulting control signal is defined as a solution to ＂fast＂ dynamics which inverts a series error model, whose state is exponentially stable. It is shown that, under sufficient conditions being consistent with the assumptions of singular perturbation theory, this problem is solvable with （ε） tracking error if and only if a set of first-order nonlinear partial differential equations are solvable. The control law can be easily constructed and the simulations show the feasibility and effectiveness of the controller.     

基础位移激励下椭圆抛物面碳纤维索网的振动

在考虑温度变化的基础上,研究椭圆平面双曲抛物面碳纤维索网在基础激励下的非线性振动问题,建立了椭圆平面双曲抛物面碳纤维索网在基础位移激励下的非线性振动方程,采用Galerkin原理及KBM法求得了椭圆平面双曲抛物面碳纤维索网非线性振动的近似解．在把碳纤维索网与钢丝索网比较的基础上,讨论分析了位移激励、温度、振幅、外阻尼等因素对椭圆平面双曲抛物面碳纤维索网非线性振动的影响,得到了碳纤维索网对温度变化不敏感,而钢丝索网受温度的影响却很大,且碳纤维索网振动特性优于钢丝索网振动特性的结论．     

大型动力系统的降维：基于模态截断的非线性Galerkin方法

为了有效地求解大型动力系统,现已提出了各种降维方法．根据非线性Galerkin方法的求解思路,我们将大型动力系统分解成三个子系统,即”慢子系统”、”适速子系统”和”快子系统”．在此基础上提出了改进的非线性Galerkin方法,即：在数值积分过程中将适速子系统的贡献导入慢子系统．然后,以一个含有立方非线性的5自由度强迫振动系统为例阐明了新方法的有效性．     

基于支持向量机对激光焊接的自适应控制

激光焊接过程是典型的不确定性非线性系统,且难以用具体的数学模型对其进行描述。为了对其进行控制,首先采用基于最小二乘支持向量机的方法对其离线建立了非线性模型;然后基于模型设计了自校正PID控制器。仿真结果表明了建模和控制方法的有效性和优越性。     

基于稳态非线性模型和线性ARX模型组合的非线性预测控制

通过点集映射来表示非线性系统的稳态模型,用系统的稳态增益来修正具有外界输入的线性自回归（AutoRegressive with eXternal input, ARX）模型的动态增益,提出了一种基于稳态非线性模型和线性ARX模型组合的非线性预测控制算法．该算法用递归最小二乘法在线辨识系统的动态模型参数,用序列二次规划算法求解目标函数．最后通过对典型化工非线性对象pH中和过程的仿真对本算法进行了验证．结果表明,本算法比广义预测控制算法具有更好的设定值跟踪性能和抗干扰能力．     

Matlab遗传算法工具箱在非线性优化中的应用

投影寻踪是一种降维处理技术,通过它可以将多维分析问题通过投影方向转化为一维问题分析。应用该法的关键在于寻求最佳投影方向,这可以转化为一个复杂的非线性优化问题来进行解决。选取某地区大气环境质量评价的投影寻踪评价模型,编制相关的目标函数和约束函数,应用基于MATLAB的遗传算法和直接搜索工具箱进行优化求解。结果表明：该工具箱在求解此类非线性优化问题上的有效性和方便性,从而为各领域应用投影寻踪模型提供了强有力的优化工具。     

循环载荷作用下两类楼板抗震性能的非线性有限元分析

为比较组合楼板和普通混凝土楼板的抗震性能,采用非线性有限元分析方法研究它们在循环载荷作用下的受力行为,并由此得到两类楼板的滞回曲线、骨架曲线及应力应变分布规律．计算结果表明,采用可靠构造措施的压型钢板与混凝土组合作用明显,在不失较高承载力的同时,组合楼板仍具有良好的抗震性能．将计算结果与试验数据相比较,验证该数值分析方法的有效性。     

Small Changes,Big Impact: Tungsten Bronzes with Extremely Large Second Harmonic Generation Achieved by the Transition Metal Doping on the B-Site

Two novel transition metal-doped tungsten bronze oxides, Pb_2.15Li_0.85Nb_4.85Ti_0.15O₁₅ (PLNT) and Pb_2.15Li_0.55Nb_4.85W_0.15O₁₅ (PLNW), are synthesized by high-temperature solid-state reactions. The Rietveld method using the high-resolution synchrotron radiation indicates that PLNT and PLNW crystallize in the orthorhombic polar noncentrosymmetric space group, Pmn2₁ (no. 31). As a class of tungsten bronze oxide, PLNT and PLNW retain a unique rigid framework composed of d⁰ transition metal cation (Ti⁴⁺ or W⁶⁺)-doped highly distorted NbO₆ octahedra along with the subsequently generated Pb/LiO₁₂ and PbO₁₅ polyhedra. Interestingly, the d⁰ transition metal-doped tungsten bronzes, PLNT and PLNW, exhibit extremely large second-harmonic generation (SHG) responses of 56 and 67 × KH₂PO₄, respectively. The observed immeasurably strong SHG is mainly attributed to a net polarization originating from the alignment of highly distorted NbO₆ octahedra with doped transition metals in the frameworks. It is believed that doping transition metal cations at the B-site of the tungsten bronze structures should be an innovative strategy to develop novel high-performance nonlinear optical materials.